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Sediments of the central and southern Strait of Georgia, British Columbia Pharo, Christopher Howard 1972

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151% SEDIMENTS OF THE CENTRAL AND SOUTHERN STRAIT OF GEORGIA, BRITISH COLUMBIA o by CHRISTOPHER HOWARD PHARO B.Sc. U n i v e r s i t y of Auckland, New Zealand, 1965. M.Sc.(Hons) Uni v e r s i t y of Auckland, New Zealand, 1967, A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of: Geology We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October, 1972 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced deg ree at t he U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r ee t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Depar tment o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Depar tment o f geological Sciences The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, Canada Date November 23, 1972 ABSTRACT A study of the d i s t r i b u t i o n , d i s p e r s a l and composition of s u r f i c i a l sediments i n the S t r a i t of Georgia, B.C., has resulted i n the understanding of basic sedimentologic conditions within t h i s area. The S t r a i t of Georgia is: a long, narrow, semi-enclosed basin with a r e s t r i c t e d c i r c u l a t i o n and a s i n g l e , main, sediment source. The Fraser. River supplies p r a c t i c a l l y a l l the sediment now being deposited i n the S t r a i t of Georgia, the bulk of i t during the spring and summer freshet. This r i v e r i s b u i l d i n g a delta into the S t r a i t from the east side near the south end. Ridges of Pleistocene deposits within the S t r a i t and Pleistocene material around the margins, l i k e bedrock exposures, provide l o c a l sources of sediment of only minor importance. Rivers and streams other than the Fraser contribute i n s i g n i f i c a n t quantities of sediment to the S t r a i t . Sandy sediments are concentrated i n the v i c i n i t y of the de l t a , and i n the area to the south and southeast. Mean grain s i z e decreases from the d e l t a toward the northwest along the axis of the S t r a i t , and basinwards from the margins. S i l t s and clays are deposited i n deep water west and north of the de l t a f r o n t , and i n deep basins northwest of the d e l t a . Poorly sorted sediments containing a gravel component are located near t i d a l passes, on the Vancouver Island shelf area, on ridge tops within the S t r a i t , and with sandy sediments at the southeastern end of the study area. The Pleistocene ridges are areas of non-depos-i t i o n , having afc.most a t h i n veneer of modern mud on t h e i r crests and upper flanks. The southeastern end of the study area contains a t h i c k wedge of shandy sediment which appears to be part of an e a r l i e r d e l t a of the Fraser River. Evidence suggests that i t i s now a s i t e of a c t i v e i i submarine erosion. Sediments throughout the. S t r a i t are compositionally extremely s i m i l a r , with-Pleistocene deposits of the Fraser River drainage basin providing the p r i n c i p a l , heterogeneous source. Gravels and coarse sands are composed p r i m a r i l y of l i t h i c fragments, dominantly of d i o r i t i c to g r a n o d l o r i t l c composition. Sand f r a c t i o n s exhibit increasing s i m p l i c i t y of mineralogy with decreasing g r a i n - s i z e . Quartz, f e l s p a r , amphibole and fine-grained l i t h i c fragments are the dominant constituents of the f i n e r sand grades. Coarse and medium s i l t f r a c t i o n s have compositions s i m i l a r to the f i n e sands. )Fihe s i l t s show an increase i n abundance of p h y l l o s i l i c a t e material, a feature even more evident i n ithe ^cU'ay-rsizesifrrraciti^ and f e l s p a r are the main minerals i n the coarse clay f r a c t i o n , with minor mixed-layer clays and k a o l i n i t e . The f i n e clay f r a c t i o n i s dominated by montmorillonite, with l e s s e r amounts of i l l i t e and c h l o r i t e . The sediments have high base-exchange c a p a c i t i e s , r e l a t e d to a considerable content of montmorillonite. Magnesium i s present i n exchange positi o n s i n greater quantity i n Georgia S t r a i t sediments than i n sediments from the Fraser River, i n d i c a t i n g a p r e f e r e n t i a l uptake of t h i s element i n the marine environment. Manganese nodules c o l l e c t e d from two l o c a l i t i e s i n the S t r a i t imply slow sediment accumulation rates at these s i t e s . Sedimentation rates on and close to the d e l t a , and i n the deep basins to the northwest, are high. i i i LIST OF CONTENTS PAGE ABSTRACT i LIST OF CONTENTS i i i LIST OF FIGURES v LIST OF TABLES v i i LIST:OECABPENDICES v i i i -ACKNOWLEDGEMENTS i x CHAPTER 1: INTRODUCTION 1.1 Geographic s e t t i n g 1 1.2 Geologic s e t t i n g 4 1.3 Geologic h i s t o r y 9 1.4 Climate 18 1.5 Oceanographic c h a r a c t e r i s t i c s 21 1.5.1 C i r c u l a t i o n 22 1.5.2 Fresh-water budget 34 1.6 Previous studies 36 1.7 SamplingsProcedures 37 1.7.1 Shipboard procedures 37 1.7.2 Laboratory procedures 38 CHAPTER 2: BATHYMETRY 2.1 Introduction 39 2.2 Physiographic subdivisions 43 2.3 Discussion 45 CHAPTER 3: LITHOLOGY 3.1 Introduction 53 3.2 Laboratory methods 54 3.3 D i s t r i b u t i o n of bedrock outcrops 57 3.4 D i s t r i b u t i o n of gravels 57 3.5 D i s t r i b u t i o n of sand 61 3.6 D i s t r i b u t i o n of s i l t - and c l a y - s i z e material 65 3.7 Sa n d - s i l t - c l a y r a t i o s 65 3.8 Size analyses 71 3.9 Cumulative p r o b a b i l i t y curves 88 3.10 Factor analysis 104 3.11 Water content 112 3.12 Sediment colours 113 3.13 Discussion: sedimentation rates and sediment d i s p e r s a l 116 i v PAGE CHAPTER 4: MINERALOGY 4.1 Introduction 134 4.2 Gravels 138 4.3 Sands 140 4.4 Sub—sand—size mineralogy 143 4.4.1 A n a l y t i c a l methods 149 4.4.2 Mineral i d e n t i f i c a t i o n c r i t e r i a 154 4.4.3 Discussion of sub—sand--size mineralogy 162 4.4.3.1 S i l t f r a c t i o n 163 4.4.3.2 Clay f r a c t i o n 169 4.4.4 Semi-quantitative studies 183 4.4.5 Chemis t r y 190 4.4.5.1 A n a l y t i c a l methods 194 4.4.5.2 Discussion 196 4.4.6 Fine-sediment textures 204 4.5 Summary and conclusions 225 CHAPTER 5: GEOCHEMISTRY 5.1 Introduction 228 5.2 Carbon 228 5.2.1 A n a l y t i c a l methods 228 5.2.2 Discussion 233 5.3 Manganese nodules 236 5.3.1 L o c a l i t i e s 237 5.3.2 Morphology 238 5.3.3 Chemical analyses 240 5.3.4 Discussion 242 6: SUMMARY Atfu CONCLUSIONS CHAPTER 6: SUMMARY AND CONCLUSIONS 244 REFERENCES 251 APPENDICES 266 V LIST OF FIGURES NO. PAGE 1 Location of study area 2 2 Bathymetry, sample l o c a t i o n s , and geographic features i n the S t r a i t of Georgia (IN POCKET AT REAR) 3 Geologic sketch map of surrounding area 5 4 Surface wind c i r c u l a t i o n i n the S t r a i t of Georgia at d i f f e r e n t times of the year 19 5 D i s t r i b u t i o n of s a l i n i t y , temperature and density measurements, February, 1950 23 6 D i s t r i b u t i o n of s a l i n i t y , temperature and density measurements, June, 1950 24 7 S a l i n i t y d i s t r i b u t i o n s on flood and ebb tides 25 8 C i r c u l a t i o n patterns determined by surface d r i f t - b o t t l e recoveries 27 9 Compilation of current patterns i n the S t r a i t of Georgia 29 10 L i v i n g animals and g r a v e l l y deposits as yet unburied by modern muds: Halibut Bank 32 11 L i v i n g animals and gra v e l l y deposits as yet unburied by modern muds: Halibut Bank 32 12 Demarkation of s i l t y water of Fraser River discharge from " c l e a r " oceanic water of Georgia S t r a i t ; July, 1971 33 13 Demarkation of s i l t y water of Fraser River discharge from " c l e a r " oceanic water of Georgia S t r a i t ; July, 1971 33 14 P r o f i l e s across the S t r a i t of Georgia showing bottom topography on an exaggerated v e r t i c a l s s c a l e 40 15 P r o f i l e s across the S t r a i t of Georgia showing bottom topography on an exaggerated v e r t i c a l scale 41 16 P r o f i l e along the axis of Ballenas Basin from Sturgeon Bank to Ballenas Islands. V e r t i c a l scale exaggerated 42 17 Subdivisions oftthe S t r a i t of Georgia into areas of d i s t i n c t i v e morphology 44 18 D i s t r i b u t i o n of sand-size sediment 60 19 Textural diagrams based on the schemes of Folk (1954) and Shepard (1954) 67 20 D i s t r i b u t i o n of sediment types based on the t e x t u r a l c l a s s i f i c a t i o n of Folk (1954) 68 21 D i s t r i b u t i o n of sediment types based on the t e x t u r a l c l a s s i f i c a t i o n of Shepard (1954) 69 22 D i s t r i b u t i o n of median gra i n - s i z e 84 23 D i s t r i b u t i o n of mean grai n - s i z e 85 24 Location map f o r samples used to construct Figures 25 to 32 90 25 to 37 i n c l u s i v e : Cumulative p r o b a b i l i t y curves of s i z e -frequency data for selected sample groups and composite groupings of samples 92-98 38 D i s t r i b u t i o n of Factors from the Factor Analysis 108 39 E f f e c t s of g l y c o l a t i o n on the 12.4S peak 159 40 X-ray diffractograms of the 53 - 20 micron f r a c t i o n s of Group A samples 164 41 X-ray diffractograms of the 2 0 - 5 micron f r a c t i o n s of Group A samples 165 42 X-ray diffractograms of the 5 — 2 micron f r a c t i o n s of Group A samples 166 v i NO. PAGE 43 X-ray diffractograms of powder mounts of Group B s i l t s 167 44 X-ray diffractograms of the. 2 — 0.2 micron f r a c t i o n from sample FR3U (Group A) 171 45 X—ray diffractograms of the 2 — 0 . 2 micron f r a c t i o n from samples 23 and 53 (Group A) 172 46 X-ray diffractograms of the 2 — 0 . 2 micron f r a c t i o n from samples 145 and 162 (Group A) 173 47 X-ray diffractograms of the 2 - 0 . 2 micron f r a c t i o n from samples 280 and 342 (Group A) 174 48 X-ray diffractograms of the 2 - 0 . 2 micron f r a c t i o n from samples 350 and 102 (Group A) 175 49 X-ray diffractograms of the 2 - 0 . 2 micron f r a c t i o n from sample 263 (Group A) 176 50 X-ray diffractograms of the <2 micron f r a c t i o n from samples 19 and 77 (Group B) 178 51 X-ray diffractograms of the <2 micron f r a c t i o n from samples 104 and 196 (Group B) 179 52 X-ray diffractograms of the <2 micron f r a c t i o n from samples 257 and 268 (Group B) 180 53y-raX-rayfdiffractogramstbf the <2 micron f r a c t i o n from samples 345 and 351 (Group B) 181 54 Ternary diagram of clay mineral percentages 188 55 Binary p l o t s of montihorillonite to c c h l o r i t e + k a o l i n i t e ' and montmorillonite to i l l i t e r a t i o s against distance from Sand Heads 189 56 P l o t of pH against time f o r F r a s e r M i v e r samples treated with sea-water 191 57 Plot of Eh against time f or Fraser River samples treated with sea-water 192 58 Diagrammatic arrangements of clay p a r t i c l e s i n sediments and f l o c c u l e s 206 59-'.riSgaMingrEieHtronpM±cr.gphptogclipKsee£e££eeze-diBded mud 210-211 60 Scanning Electron Microphotographs of f a e c a l p e l l e t s 212-213 61 Scanning Electron Microphotographs of agglutinated mud lumps 215-218 62 Scanning Electron Microphotographs of glauconite grains 219-224 63 Plot of organic carbon content against clay content 235 64 Photographs of manganese nodules: (a) from Sangster Ridge; (b) from sample s i t e 341 239 LIST OF TABLES I Stratigraphi.c c o r r e l a t i o n s i n the. Lower Mainland, Northern Washington, and I n t e r i o r of B r i t i s h Columbia II R e p r o d u c i b i l i t y of sieve analyses III Reproducibility- of p i p e t t e analyses IV Colour changes i n sediments induced by s e l e c t i v e removal of constituents V Ratio of quartz:plagioclase:potash f e l s p a r VI Ratio of mica ( i l l i t e ) : montmorillonite VII Semi-quantitative clay mineral analysis VIII T o t a l exchange ca p a c i t i e s and contents of exchangeable bases IX Contents of oxalate-extractable i r o n , aluminum, manganese and s i l i c a X C o r r e l a t i o n matrix XI ' T o t a l carbon, organic carbon and carbonate contents XII Semi-quantitative spectrochemical analyses of manganese nodules v i i PAGE 10-13 56 56 115 142 170 184-5 197 199 201 229-232 241 v i i i APPENDICES PAGE I S t a t i s t i c a l parameters from s i z e analyses 266 11(a) Input data for Factor Analysis 270 11(b) Varimax Factor Matrix, four-Factor model 281 11(c) Varimax Factor Score Matrix, four-Factor model 285 III Fraser River Delta Project 286 IV Sample l o c a l i t i e s 287 ix ACKNOWLEDGEMENTS The writer i s s i n c e r e l y g r a t e f u l to Dr William C. Barnes who, i n h i s capacity as thesis supervisor, spent many hours discussing aspects of the study, offered considerable encouragement, and c r i t i c a l l y read the manuscript. Expenses incurred during laboratory research and the f i n a l preparation of the manuscript were met by grants NRC A-7027 and RC 21-9692 held by Dr Barnes. Discussions with, and the help of Dr L.M. Lavkulich on aspects of the clay mineralogy are g r a t e f u l l y acknowledged. The writer also wishes to express h i s gratitude to the many other people with whom he came i n contact who contributed i n some way to the completion of t h i s p r o ject. Among them are: the o f f i c e r s and crew of the CNAV LAYMORE; Mr E. Montgomery and Mr.B. Cranston for t e c h n i c a l assistance; Drs L i o n e l Carter and John Luternauer, Mr R.D. MacDonald, and Mr Mike Pullen who, while s t i l l graduate students at UBC, became engaged i n stimulating discussions on marine geolo g i c a l research; Dr D.L. T i f f i n for h e l p f u l discussions on aspects of the morphology and structure of the S t r a i t , and for making bathymetric charts a v a i l a b l e to the wr i t e r ; fellow graduate students who, at short n o t i c e , offered t h e i r assistance with the sample c o l l e c t i n g ; and Miss Jan Bain f o r typing the f i n a l manuscript. The considerable help, understanding and devotion of my wife Sue, who has withstood the disadvantages of being the wife of a graduate student and can s t i l l smile, has been a major f a c t o r i n the su c c e s s f u l completion of t h i s t h e s i s . FRONTISPIECE F l o c c u l e s t r u c t u r e w i t h i n a g l a u c o n i t e p e l l e t 2 FIGURE 1 Location of the study area in southwestern British Columbia. Canada, and northwestern Washington. U.S.A. 3 for transportation, sport and recreation, as well as for d i s p o s a l of sewerage, garbage and other waste material. The long axis of the S t r a i t of Georgia extends i n a north-westerly d i r e c t i o n from the U.S. San Juan Islands i n the south to Quadra Island i n the north, between l a t i t u d e s 40°50'N and 50°00'N, a distance of some 225 kilometres (Figure 1). Access to the open P a c i f i c Ocean i s achieved i n the south by way of Juan de Fuca S t r a i t , through the p a r t i a l b a r r i e r of the Canadian Gulf Islands and the U.S. San Juan archipelago. To the north connection with the P a c i f i c i s made through numerous narrow channels. Of the t o t a l length of the S t r a i t , only the southern 110 kilometres between l a t i t u d e s 48°50'N and 49°26'N are included i n t h i s study, which covers the area extending from Alden Ridge i n the south to Ballenas Islands i n the north. Within t h i s area the S t r a i t has an average width of 28 kilometres, varying between 17h kilometres j u s t south of Texada Island to 35 kilometres between Valdes Island and Point Grey. Topography i n the S t r a i t v aries considerably from the smooth fan of sediments of the Fraser River d e l t a that extends almost completely across the S t r a i t , to the rugged region of steep-sided banks and ridges separating deep, f l a t - f l o o r e d basins i n the north (see map, Figure 2). Tabular summaries of the dimensions and parameters of the S t r a i t of Georgia are a v a i l a b l e i n Waldichuk (1957), Mathews, Murray, and McMillan (1966) and T i f f i n (1969). High mountains of the Vancouver Island Range to the west are separated from the S t r a i t by a broad, low-lying, emergent portion of the Georgia Depression (Holland, 1964). On the east side, north of Burrard I n l e t , the Mainland Coast Range r i s e s almost d i r e c t l y above the S t r a i t , being separated i n only a few places by a narrow s t r i p of lowland.. South of Burrard I n l e t the S t r a i t i s bordered by the extensive low-lying, f l a t t i s h expanse of the Fraser Lowland. Names of geographic features referred to throughout the text are given i n Figure 2. 1.2 GEOLOGIC SETTING A generalised g e o l o g i c a l sketch map of the area surrounding the Central and Southern S t r a i t of Georgia i s presented i n Figure 3. The area l i e s i n the "...western part of the 'Paleozoic-Mesozoic C o r d i l l e r a n volcanic orogenic b e l t ' or P a c i f i c engeosyncline... (Danner, 1968, p.2). I t i s part of a long, l i n e a r s t r u c t u r a l depression that extends from the Gulf of C a l i f o r n i a i n the south through the Great V a l l e y of C a l i f o r n i a , Willamette V a l l e y Oregon, Puget Sound Washington, Georgia Depression B r i t i s h Columbia, to Dixon Entrance Alaska, where i t seems to disappear. A large part of t h i s depression i s near to or below s e a - l e v e l , but i s a c t u a l l y inundated only i n B r i t i s h Columbia and part of the Washington and C a l i f o r n i a sections. The S t r a i t of Georgia i s the submerged portion of the Georgia Depression (Holland, 1964) which extends along the coast of B r i t i s h Columbia between Vancouver Island and the Mainland. Emergent portions of Georgia Depression flank the S t r a i t on e i t h e r side, and are known as the Georgia Lowland on the mainland side and the Nanaimo Lowland along the east coast of Vancouver Island. The Georgia Lowland forms a narrow s t r i p ranging from four to eighteen kilometres i n width and representing i n large part an elevated T e r t i a r y erosional surface (Holland, 1964, p.36). South of Burrard In l e t the Georgia Lowland i s c a l l e d the Fraser Lowland, a large, 134 00 123° 00 laVoo 133*00' LEGEND Recent and Pleistocene ALLUVIUM, ORIFT, 4NTERGLACIAI, SEDIMENTS Tertiary Sedimentary and Volcanic Rocks INCLUDES CHUCKANUT, BURRARD, KITSHANO, AND SOOKE FORMATIONS, METCHOSIN VOLCANICS. Upper Cretaceous Sedimentary Rocks NANAIMO GROUP Pre-Upper Cretaceous Sedimentary, Metamorphic. Volcanic and Plutonic Rocks INCLUDES THE VANCOUVER, BOWEN ISLAND, JARVIS, SICKER, OAMBIER, AND SAN JUAN GROUPS, LEECH RIVER FORMATION, AND MALAHAT VOLCANICS y-,'sl-? Coast Range Intrusives Is/and Intrusions Sources: GEOLOGIC MAP OF BRITISH COLUMBIA , (OSC MAP 933A) 1963. GUIDEBOOK FOR OEOLOGICAL FIELD TRIPS IN SOUTHWESTERN BRITISH COLUMBIA , (UBC GEOLOGY DEPT REPORT Na 6) 1968. IE.MULLER 1967. MULLER AND JELETZKY 1970. TIFFIN 1969. Figure 3: GEOLOGICAL SKETCH MAP OF THE AREA AROUND THE CENTRAL AND SOUTHERN STRAIT OF GEORGIA, BRITISH COLUMBIA. CANADA. AND WASHINGTON. U.S.A. 6 triangular-shaped feature of low r e l i e f believed to be l a r g e l y de p o s i t i o n a l i n o r i g i n (Holland, 1964). The Nanaimo Lowland i s a post-Cretaceous erosional feature that has been modified l o c a l l y by g l a c i a l erosion and deposition of a mantle of g l a c i a l and f l u v i o g l a c i a l m a terial. I t i s underlain by a thick sequence (5,000 feet to 10,000 feet) of marine- and non-marine Upper Cretaceous s t r a t a of the Nanaimo Group (Clapp, 1912, 1913, 1914, 1917; Usher, 1952; Muller and Jeletzky, 1970) deposited i n two basins which were separated by two u p l i f t e d ridges of pre-Mesozoic rocks that trend northward from the Nanoose area on Vancouver Island (Muller and Jeletzky, 1967). North of Burrard Inlet the Georgia Lowland i s underlain by g r a n i t i c intrusions of the Coast C r y s t a l l i n e Belt (Holland, 1964; Roddick, 1965) plus i n l i e r s of older rocks. To the south the c r y s t a l l i n e basement l i e s under some 15,000 feet of l a t e Cretaceous, T e r t i a r y and Quaternary continental and marine sediments (Roddick, 1965; Hopkins, 1966; Mathews, Murray and McMillan, 1966). Apart from an i n l i e r of probable Mid- to Upper- Cretaceous greywackes and a r g i l l i t e s i n the G a r i b a l d i area (Mathews, 1958), there i s no d e f i n i t e l y known equivalent of the Nanaimo Group on the B.C. mainland. There i s s t i l l some controversy as to whether the uppermost Nanaimo Group (Gabriola Formation) i s Palaeocene rather than Late Cretaceous i n age and therefore c o r r e l a t a b l e with the Burrard and K i t s i l a n o Formations, or whether on the other hand the lower part of the Burrard Formation i s Late Cretaceous i n age (McGugan, 1962; Rouse, 1962; Crickmay and Pocock, 1963; Hopkins, 1966; Scott, 1967). 7 The Fraser Lowland, extending eastward from Georgia S t r a i t as a broadly t r i a n g u l a r reentrant, occurs i n an area that was once the s i t e of a s t r u c t u r a l depression known as the Whatcom Basin (Hopkins, 1966). This basin, which extended eastward from the coast to Laidlaw, B.C. then southwestward to Bellingham, Washington, i s floored by Late Cretaceous rocks overlying c r y s t a l l i n e basement, and i s bounded to the south by Late Cretaceous to Early T e r t i a r y continental sediments of the Chuckanut Formation. Hopkins (1966) did not regard e i t h e r the Late Cretaceous or the Chuckanut to be part of the Whatcom Basin f i l l , but instead he re l a t e d them to a once more extensive region of marine and continental sedimentation that included the area over which the Nanaimo Group now outcrops. Knowledge of the rocks i n the Whatcom Basin i s l a r g e l y r e s t r i c t e d to information obtained from d r i l l cores, augmented by scattered outcrops around the basin margin, road cuts, and some tunnels. A thick, luxuriant vegetative cover, deep weathering of surface m a t e r i a l , and a th i c k mantle of Pleistocene deposits are severe r e s t r i c t i o n s to the a c c e s s i b i l i t y and area of outcrops. The basin i s f i l l e d with a thick sequence of continental deposits; no marine rocks have been i d e n t i f i e d from d r i l l core or i n outcrop. T e r t i a r y sediments, and the underlying Cretaceous, lap on to the i n t r u s i v e complex of the Coast Mountains (see Roddick, 1965), dipping southward toward the centre of the basin. To the east and south T e r t i a r y rocks wedge out on pre-Tertiary metamorphic and u l t r a b a s i c rocks of Canadian and American Sumas Mountains, and upon the Palaeocene Chuckanut Formation. The thickness of sediment i n the basin, the consistent basinward dips of s t r a t a from north and south rims of the 8 basin, the thickening of beds and formations toward the ;centre of the basin, and the inclusion of younger strata that seem to wedge out to the north, south of Burrard Inlet (Roddick, 1965; Mathews, Murray and McMillan, 1966), suggest that persistent i f intermittent subsidence and deposition took place throughout the Late Mesozoic and Tertiary. No Tertiary rocks similar to those of the Whatcom Basin occur on eastern Vancouver Island, and later Tertiary sediments, believed to be several thousand feet thick, are known only from drill-holes in the Fraser Lowland. A descriptive summary and references to other stratigraphic analyses are given by Hopkins (1966) for the Tertiary formations in the Whatcom Basin. Roddick (1965) has presented a detailed account of the geology and petrology of the southern Coast Mountains. The geology of ^ loutheasterhhVancouveralslandrhaslbeenhdi'scU'Ssed by -Clapp (1921, 1913, 1914, 1917), Usher (1952), Muller (1967), and Muller and Jeletzky (1967, 1970). Pleistocene deposits are both widespread and thick, locally reaching a cumulative thickness of 1700 feet (Johnston, 1923; Armstrong and Brown, 1954; Armstrong, 1956, 1957, 1960; Fyles, 1963; Armstrong et al., 1965). Late- and post- Pleistocene sediments, both of periglacial origin and modern river deposition, have accumulated locally to thicknesses in excess of 1000 feet (Mathews and Shepard, 1962). Since the end of the Pleistocene the Fraser River has constructed a delta extending westward into the Strait of Georgia some 16 miles from New Westminster (Mathews and Shepard, 1962). The trend of the Strait is similar to that of the structures in the flanking rocks, especially on the western side in the Nanaimo Group. Muller (1967) advanced the idea that the pattern of faulting in 9 the Nanaimo Group rocks might represent splays of one or more major f a u l t s along the east coast of Vancouver Island, the pattern being of numerous fault-bounded blocks t i l t e d toward the northeast and down-thrown to the southwest. T i f f i n (1969) advocated a s i m i l a r block-faulted o r i g i n f o r the southern Island slope ridges, although he considered the downthrown side to be to the northeast; i . e . , opposite to that of Muller (1967). Faulting along the l i n e of the Vancouver Island slope followed downflexing of the S t r a i t of Georgia associated with the u p l i f t of the Coast Mountains. Maximum depression of the basin axis occurred along the western side of the S t r a i t . The dominance of f a u l t i n g rather than f o l d i n g i n the Insular Belt (area west of the mainland coast) i s advocated by Sutherland-Brown (1966), Muller (1967), and by Muller and Jeletzky (1967, 1970). Bedrock structures, probably f a u l t - c o n t r o l l e d , are v i s i b l e i n some of T i f f i n ' s (1969) seismic p r o f i l e s . The occurrence of fault-bounded blocks of Nanaimo Group sediments 5000 feet above s e a - l e v e l i n the A l b e r n i and Cowichan areas (Fyles, 1963; Muller and Jeletzky, 1967) indicates that block-f a u l t i n g may well have been the common s t r u c t u r a l feature of the Nanaimo Group rocks, but the d i r e c t i o n of throw may not have been consistent. The a v a i l a b l e evidence supports the contention that the o r i g i n a l control on the o r i g i n of the S t r a i t of Georgia was te c t o n i c . 1.3 GEOLOGIC HISTORY Deciphering the geologic h i s t o r y of the area of the S t r a i t i s made d i f f i c u l t by the lack of outcrop and by the poor r e s o l u t i o n of bedrock types i n seismic p r o f i l e s . Between the Late Cretaceous and Pleistocene much of the geologic record i s blank. The o u t l i n e of the 10 C O R R E L A T I O N OF KNOWN PACIFIC N O R T H W E S T PALEOZOIC FORMATIONS PERIOD S Y S T E M EPOCH-SERIES VANCOUVER ISLAND SAN JUAN I SLANDS STRAIT OK GEORGIA C A S C A D E MT S- OF B C - B WASHINGTON (NORTH OF 4 0 ° 30') B C INTERIOR' A S H C R O F T - K A M L O O P S PR INCETON Q_ UJ D. G_ H =» <t cc ex. cr, b OCHOAN GUADALU PI AN LEONARD IAN WOLFCAMPiAN UPPER SICKER 1 TR AF TO N UPPER CMILLIWACK UPPER CHILLIWACK (WASH! 1 iR-CVl MIDDLE HARPER RANCH 2 a < tu — 0 < 1 > >- lu "> O 2 D 2 5 1 c VIR6ILI AN MISSOURIAN DESMOINESIAN LAMPASAN-ATOKAN MOR ROWAN o ^  ^  ^ L O W E R „ S I C K E R MIDDLE CHILLIWACK , ( SJ ) P L A N T - B E A R I N G C L AS T l C S (WASH ) (B C) MIDDLE CHILLIWACK j (WASH) , ( B C ) ~"~"T LOWEfT •' HARPER RANCH a u 2 ? S ° Q. CU — V) c in CHES TERI AN MERAMECIAN 0 S AG E AN KINDERHOOKAN NONE REC )G N IZED IN MAP AREA 2 0 — a 2 ° o : > LU 11 Q | BRADFOROIAN CHAUTAUQUAN S E N E C A M ERIAN PRESIDENT CHANNEL BEOS (S J ) LOWER CHILLIWACK 0 % c ULSTER IAN . PRE-DEVONIAN ? TU RT LE B A CK C OMPLEX (S-J-) SCHISTS OF VEDDER MT (B CO Y E L L O W A S T E R COMPLEX (WASH) ETC . TABLE 1: i n o f S t r a t i g r a p h i c r e l a t i o n s h i p s of known format ions the Lower M a i n l a n d , N o r t h e r n Washington and I n t e r i o r B r i t i s h Co lumbia . From Danner (1968). C O R R E L A T I O N OF KNOWN PAC IF IC N O R T H W E S T MESOZOIC FORMATIONS PERIOD S Y S T E M E P O C H - S E R I E S T E X A D A IS- E-VANC IS- SAN J U A N IS STRAIT OF GEORGIA C A S C A D E MTS- OF BC- -WASHINGTON NORTH OF 4 0 " 30' B C- INTERIOR; ASHCROFT-KAMLOOPS HOPE P R I N C E T O N a: DANIAN MAESTR ICHT IAN SENONI AN T U R O N I A N C E N O M ANI AN ALB I AN A P T I A N B A R R E M I A N HAUTERIVI AN VALANGIN I AN BERR IAS IAN L O W E R C H U C K A N U T , N A N A I M O " 2 ' — G R C U P I T IS-, y is-,S-J ) C H E A K A M U S ~~~.FM-, COAST, Mrs. L O W E R C H U C K A N U T 1 L O P E Z P I L L O W L A V A S G R E Y W A C K E : P A S A Y T E N G R O U P ( W A S H ) IB C) S P I E D E N F O R M A T I O N L S ^ J 1 _ ? . N O O K S A C K K I N G S V A L E - •> ( B C ) I B R 0 K E N 8 A C K H I L L F M ? P E N I N S U L A F M (8 C) S P E N C E '•i-. . B R I D G E J A C K A S S M T fBREW'-iruOOEf I G R O U P G R O U P < PORTLANOI AN KIMMERIOGIAN G R O U P ( W A S H ) O E W O N E Y C R E E K G R O U P OXFOROI AN A G A S S I Z PRAIRIE F M -CALLOVI AN B A T H O N I A N K E N T B I L L H O O K M Y S T E R I O U S C R E E K (8 CO _•, A S H C R O F T G R O U P B A J O C I A N TOARC I AN N O O K S A C K V O L C A N I C S ? C H E H A L I S ' V O L C A N I C S ? H A R R I S O N L A K E PL IENSBACH I AN S I N E M U R I A N H E T T A N G I A N RHAETIAN P A R D O N S B A Y NO RI A N KARNI A N L ADINI AN _ 5 E p i M E _ « ^ - j f t - 3 T r | SUTTON LS IRANKLIN CREEK VOLCANICS Tv IS) BAY -OPE" ^. L9AY T E X A D A VOLCANICS (ST-G) C U L T U S ( W A S H ) I B - C O C U L T U S F M ( Q C ) HAhO^KM IS L A D N E R T H O M P S O N G R O U P G R O U P N I C O L A - P A V I L I O N " T U L A M E E N " G R O U P S ( B C 0 ANISIAN SCYTHIAN Table 1 . . . . continued. 12 C O R R E L A T I O N OF KNOWN PACIFIC N O R T H W E S T C E N O Z O I C FORMATIONS EPOCH-SER IES S T A G E - A G E CALIFORNIA VANCOUVER ISLAND SAN JUAN ISLANDS C A S C A D E MTS' OF B C - 6 WASH-NORTH CF 4e°30' B C INTER IOR AS H C ROFT-K AMLOOPS P R I N C E T O N PLIOC EN E SAN JOAQUIN PRE - S E YM OUR Itj PAR-SEDIMENTS OF FRASER DELTA P L A T E A U B A S A L T ETCH E G 0 IN 1 T\ f* A J H T . C ; M I O C E N E J A \ J A L 1 1 U O _ _ D U T O MJTE NEROLY CIERBO BRIONES TEMBLOR VAQUEROS SOOKE FM (VIS) LOWER 1 P I A L ' F I r v OLIGOCENE u L f t K L L L T BLAKELEY CARMAN A H-FM HANNEGAN VOLCANICS LINCOLN HUNTINGDON GROUP (WASHO(BC) KITSILANO (BC) E O C E N E KE AS E Y • METCH?OSIN~ 1 (VIS) | KTFrTcTopsT^-^^^^-^^ GROUP PRINCETON TRANOUILLE" GROUP 6E.DS T E J O N TRANSITION BEOS BURRARD (BC) DOMENGINE CAPAY P A L E O C E N E ME G AN 0 S -y-^tS-J-) ^'CHUCKANUT CHUCKANUT (WASH) MART INEZ Footnotes: 1. The terms: Trefton, President Channel and Lower, Middle and Upper Harper ranch are informal stra t i g r a p h i c names as yet not formally defined. The term "Trafton" replaces "Stillsguamish" previously assigned to these rocks but now recognised f r o a e a r l i e r use as a Pleistocene s t r a t i g r a p h i c u n i t . The d i v i s i o n s of the Sicker Group and Chilliwack Group are based on present knowledge of f o s s i l zones i n rocks mapped as belonging to these groups. Middle Pennsylvanian f u s u l i n i d s have been i d e n t i f i e d i n limestone from'the Ballenas Islands by Charles Ross ( j . Muller, Oral communication). 2. New age assignments f o r the Ladner Group and Dewdney Creek Group are based on the work of J ane s Contes i n the Manning Park area. T a b l e 1 . . . . c o n t i n u e d . Table 1: QUATERNARY RECORD CLIMATIC TRENDS (approximate d a t e s ) A l p i n e g l a c i e r s slowed r e c e s s i o n and advance A l p i n e g l a c i e r s g e n e r a l and r a p i d r e c e s s i o n A l p i n e g l a c i e r s slow r e c e s s i o n A l p i n e g l a c i e r s maximum r e c e n t e x t e n t C o o l p e r i o d Warmer p e r i o d C o l d p e r i o d X e r o t h e r m i c (Warm-Dry) C l i m a t i c Optimum (Warm-Moist) 1950 A.D. 1920-1950 A.D. 1850-1920 A.D. 1650-1850 A.D. 1550-1700 A.D. 900-1000 to 12C0-130O A.D. 500 B.C. 3,4000 to 5-6000 BP 6000-8000 BP STRATIGRAPHY Mount S t . Helens Ash (1802) e r u p t i o n Mount S t . Helens Ash about 500 y e a r s ago Mount R a i n i e r Ash 2,000-2,300 y e a r s ago Mount S t . Helens Ash about 3,000 y e a r s ago Mount Mazama Ash about 6,600 y e a r s ago BRITISH COLUMBIA WASHINGTON P o s t G l a c i a l FRASER CLACIATION ^SUMAS STADE 10.000 to 11.000 + S a l i s h Croup Sumas D r i f t (Lowland) l o c a l P o s t G l a c i a l Sequences Sumas D r i f t (Lowland) l o c a l EVERSON 11,000 to INTERSTADE 13,000 t G l a c i e r Peak ash (12,000 y e a r s ago) o < < O o VASHON 13,500 to STADE 18,000 ± (Lowland) CTANS 17,000 to CREEK 21.000 + STADE ( A l p i n e ) OLYMPIA INTERGLACIATION 15,000 to 50,000~T ' ( C o o l and m o i s t - P i n e , s p r u c e , f i r p o l l e n ) Whatcora g l a c i o m a r i n e Newton s t o n y c l a y C l o v e r d a l e sedimen t s S u r r y D r i f t (Lowland) Quadra sediments Be 11inghara g l a c i o m a r i n e Deming sand Ku1s han g l a c i o m a r i n e d r i f t Vashon D r i f t ( Lowland) Evans Creek ( D r i f t ( A l p i n e ) K i tsap Forma t i o n SALMON SPRINGS GLACIATION G r e a t e r than 50,000 Semiamu D r i f t (age unknown) Dashwood D r i f t ( V a n . I s . age unknown) Salmon S p r i n g s D r i f t PUYALLUP INTERGLACIATION STUCK GLACIATION" ALDERT0N_INTERGLACIATION ORTING GLACIATION G l a c i a l and i n t e r -g l a c i a l sequences i n d r i l l h o l e s Sequences i n S o u t h e r n and S o u t h e a s t e r n Puget Sound Table 1 . . . . c o n t i n u e d . 14 geologic h i s t o r y presented here has been compiled from Snavely and Wagner (1963), Danner (1965, 1968), Sutherland-Brown (1966), Hopkins (1966), Roddick (1966), Mathews (1968)., and T i f f i n (1969). Table 1, taken from Danner (1968), summarises s t r a t i g r a p h i c r e l a t i o n s h i p s i n the area. The oldest rocks i n the area belong to the Sicker Group, which comprises 8,000 to 10,000 feet of al t e r e d b a s a l t i c flows, breccias, and t u f f s , l o c a l l y i n t e r c a l a t e d and i n t e r f i n g e r i n g with greywacke, a r g i l l i t e and chert. The Sicker Group i s o v e r l a i n by about 1,000 feet of c r i n o i d a l and cherty limestones of ?Late Pennsyl-vannian or Early Permian age. A period of mild u p l i f t and l o c a l erosion i s suggested f o r the remainder of the Permian and the Early T r i a s s i c : no rocks of t h i s age have been i d e n t i f i e d i n the area. From the M i d - T r i a s s i c to the Late T r i a s s i c (Mid Karnian) rapid sinking and eruption of 10,000 feet of sodic basalt flows and p i l l o w lavas of the Karmutsen Formation occurred. Extrusion of lava seems to have stopped i n the Late T r i a s s i c , to be followed by deposition of between 400 and 3000 feet of limestones over most of the area. This limestone i s preserved i n i s o l a t e d patches over much of Vancouver Island and on Texada Island. Sedimentation continued into the Early J u r a s s i c , and was succeeded by explosive eruption of p o r p h y r i t i c andesite agglomerates and t u f f s of the Bonanza Formation. Most of the Middle and Late Jurassic and Early Cretaceous was a period of general non-deposition and possibly erosion. The future s i t e of Georgia S t r a i t i s believed to have been a tectonic highland at t h i s time, and most of Vancouver Island and Georgia S t r a i t continued to be exposed and eroded u n t i l the Santonian, when basal conglomerates of the Upper Cretaceous Nanaimo Group were deposited i n a depression (a downwarped or downfaulted trough) c a l l e d the Georgia Seaway (Sutherland-Brown, 1966). Deposition of 5,000 to 10,000 feet of a l t e r n a t i n g marine shales and marine and non-marine sandstones, some coal measures and conglomerates, followed and continued throughout the Late Cretaceous. General withdrawal of the sea from the area occurred sometime i n the uppermost Cretaceous or e a r l i e s t Palaeocene. Marine sediments are missing from the sequence of ?Late Cretaceous to Eocene rocks i n the Whatcom Basin and there are no sediments of t h i s age on the southeast coast of Vancouver Island. The early T e r t i a r y i s represented i n the southern t i p of Vancouver Island by some 7,500 feet of submarine p i l l o w basalts (Metchosin V o l c a n i c s ) , although t h i s sequence appears to be r e l a t e d to a petrographic province to the south (i n Western Washington and Oregon, see Snavely and Wagner, 1963). T e r t i a r y marine sedimentation seems to have been r e s t r i c t e d to the west coast of Vancouver Island. Snavely and Wagner (1963) depict a Mid T e r t i a r y shoreline crossing southern Vancouver Island and entering Washington near Bellingham on t h e i r p'alaeogeographic reconstructions of T e r t i a r y h i s t o r y . Sutherland-Brown (1966) suggests t h i s shoreline extended from Kyoquot to Sooke on Vancouver Island, where Oligocene and Early Miocene marine sediments overlap older rocks and have a d i s t i n c t shoreline conglomerate at the base of the se c t i o n . Within Whatcom Basin ?Late Cretaceous to Late Eocene non-marine conglomerates, sandstones, shales, and some l i g n i t e s and coals, were deposited i n a l l u v i a l p l a i n environments. M a t e r i a l was derived from the growing Coast Ranges and Vancouver Island mountains, although f l o r a l evidence suggests that the growing uplands were much lower than at present. Local vigorous u p l i f t may have occurred to provide a source for conglomerates. Roddick (1966) t e n t a t i v e l y concluded that r e l a t i v e l y l i t t l e u p l i f t of the Coast Mountains occurred i n the Early T e r t i a r y , but most has occurred since the Pleistocene. He c i t e s as evidence that although coarse conglomerates occur i n the T e r t i a r y , marine Upper Cretaceous rocks intruded by quartz d i o r i t e s are found i n the G a r i b a l d i area at an elevation of 6,000 f e e t . Pliocene plateau basalts of the c e n t r a l i n t e r i o r of the Province of B r i t i s h Columbia r i s e gradually from 2,500 feet to 8,500 feet i n the Coast Mountains. In both cases the amount of u p l i f t indicated i s about 6,000 f e e t , and the younger basalts place a l i m i t i n the time of u p l i f t . How f a r across the S t r a i t of Georgia T e r t i a r y continental sedimentation extended i s not known. Mathews (1968) considers the S t r a i t of Georgia to have been a subsiding basin i n which several thousand feet of c l a s t i c sediment accumulated. However, d e f i n i t e answers cannot be obtained from seismic records, and T e r t i a r y rocks are unknown from the east coast of Vancouver Island. Hopkins (1966) suggests that deposition of T e r t i a r y rocks slowed or ceased by the end of the Eocene or e a r l i e s t Oligocene. During the Miocene orogenic a c t i v i t y i n western Washington and Oregon produced a number of more or l e s s i s o l a t e d , closed basins with l o c a l accumulation within them of continental sediments. By the Late Pliocene and Pleistocene, general u p l i f t of the Coast Mountains and Cascade Mountains added to the c l a s t i c sediments c a r r i e d to the area. Pleistocene stratigraphy of the Lower Fraser V a l l e y has been described by Armstrong and Brown (1954), Armstrong (1956, 1957, 1960), and Armstrong et al.(1965). Up to 2,000 feet of older Pleistocene and Pliocene sediments have been recorded i n d r i l l holes (Danner, 1968). Over these occur the i n t e r g l a c i a l sands and clays that make up the Quadra sediments (see Table 1) at Point Grey; s i m i l a r sediments at Point Roberts to the south are believed by Danner (1968) to be older than the Point Grey beds. Extensive deposits of outwash, t i l l and glaciomarine d r i f t , and i n t e r g l a c i a l a l l u v i a l sediments occur above an erosion surface cut on Quadra sediments. Pleistocene deposits with chaotic and s t r a t i f i e d i n t e r n a l structures are recorded i n seismic p r o f i l e s across the S t r a i t ( T i f f i n , 1969). Some of these deposits have been correlated t e n t a t i v e l y with Pleistocene deposits on nearby land (e.g. McCall Ridge Unit and Point Grey s e r i e s ) . Mathews (1968) suggested that the e n t i r e Georgia Depression was at one time f i l l e d with Pleistocene sediments but T i f f i n (1969) found no evidence of debris of Pleistocene age i n the f l o o r of Ballenas Basin on the west side of the S t r a i t . During each of the major g l a c i a l episodes i c e advanced southward and southwestward into the S t r a i t of Georgia, flowing out to sea by way of the present Juan de Fuca S t r a i t . Ice thickness i n the S t r a i t of Georgia reached at l e a s t 5,000 feet (Roddick, 1965; Mathews, 1968; G l a c i a l Map of Canada, 1958). At l e a s t two (Fyles, 1963: Vancouver Island) or three (Armstrong et a l . , 1965: Vancouver and Fraser Lowland areas) major l a t e advances of i c e are known on land surrounding the S t r a i t . T i f f i n (1969), however, could not f i n d c l e a r evidence for the number of g l a c i a l advances that had taken place within the S t r a i t , p a r t l y because of the rapid l a t e r a l and v e r t i c a l f a c i e s changes exhibited by the Pleistocene deposits, and p a r t l y because the i c e -deposited material, influenced by changing sea-levels, must have undergone some reworking and modification. 18 During the Late Pleistocene or early post Pleistocene, the thick wedge of sediment comprising Roberts Swell (see Figure 2) was deposited. This material appears to have come from the southeast and i s believed to have been an older d e l t a of the Fraser River, b u i l t at a time when the r i v e r discharged into the S t r a i t from near Bellingham i n the U.S. ( T i f f i n , .1969). Subsequently, at sometime s h o r t l y a f t e r the Sumas Stade, the Fraser River changed from i t s southerly course to i t s present one and commenced constructing: i t s present d e l t a . The growth of the delta and the d i s p e r s a l of sediments i n the S t r a i t were influenced, and often d i r e c t e d , by Pleistocene and older deposits. Ponding of sediments occurred behind such upstanding features as Roberts Reef, Fraser Ridge, Finger Ridge and the section of McCall Ridge between McCall Bank and Point Grey, u n t i l such times as these b a r r i e r s were buried and sediment d i s p e r s a l could continue unimpeded. The present d i s t r i b u t i o n of sediments i n Georgia S t r a i t r e f l e c t s both the early influence, and the continued existence, of some of these older ridges and Pleistocene deposits. 1.4 CLIMATE Surface wind c i r c u l a t i o n on the P a c i f i c coast i s d i r e c t l y r e l a t e d to the proximity of a semi-permanent high-pressure c e l l i n the eastern P a c i f i c Ocean centred at approximately 30°N, 145°W. P r e v a i l i n g winds i n summer r e s u l t i n g from t h i s c e l l are northwesterly. The s l i g h t weakening and southward migration of t h i s high-pressure c e l l i n the winter, coupled with the development and i n t e n s i f i c a t i o n of a low-pressure c e l l i n the Aleutian area, causes a r e v e r s a l of wind d i r e c t i o n s i n the winter. P r e v a i l i n g winds on the P a c i f i c coast are southeasterly i n autumn and early winter, s h i f t i n g to southerly and southwesterly by the l a t e winter. 19 Surface wind patterns in llie Strait of Gcori ' ia (luring ( A ) winter, O c l o l i e i - M a r c h . (Ii) sprint; transi-tion, A p r i l - M a y , and ( C ) summer, J ime-Scple inl ier (Kxlended from Harris and l ial lrav, l!).">-l). FIGURE 4: S u r f a c e w i n d c i r c u l a t i o n i n t h e S t r a i t o f G e o r g i a a t d i f f e r e n t t i m e s o f t h e y e a r ( f r o m Waldich.uk, 1957 , p.417) . Within the S t r a i t of Georgia t h i s general picture i s strongly modified by the presence of the mountains and by the l o c a l wind patterns i n Juan de Fuca Strait.,. Puget Sound and the Fraser V a l l e y . The r e s u l t (Figure 4) i s a closed, anticlockwise c i r c u l a t i o n f o r the southern part of the S t r a i t (south of a l i n e between Nanaimo and Vancouver, and north of the Olympic Peninsula) i n winter, with a s h i f t to generally e a s t e r l y or southeasterly winds throughout the S t r a i t during spring, and a rather confused pattern i n summer, with p r e v a i l i n g southwesterly or southeasterly winds i n the southern parts and north-westerlies at the northern end. Wind records kept by the Meteorological O f f i c e at Vancouver International A i r p o r t show that p r e v a i l i n g winds at the a i r p o r t are, on the basis of percentage frequency from each d i r e c t i o n , almost always e a s t e r l y . The monthly data f o r the years 1964 to 1972 suggest the average p r e v a i l i n g winds for each month, except one or twommonths i n summer, are eas t e r l y blowing at 6 to 8 miles per hour. However, the data also shows that westerly winds are generally stronger, i f of shorter duration, and these winds w i l l be the important ones c o n t r o l l i n g movement of sediment on the d e l t a , and erosion of coastal regions on the east side of the S t r a i t . P r e c i p i t a t i o n , mostly as r a i n , i s moderate and increases from west to east. The western margin of the S t r a i t i s i n the r a i n shadow of the Vancouver Island Mountains, and receives an average of 40 inches of p r e c i p i t a t i o n per year. In Burrard I n l e t the average amount of p r e c i p i t a t i o n per year i s 60 inches. The wettest period i s from October to February, averaging 6 to 8 inches per month; the d r i e s t , July and August, averaging l e s s than 1 inch per month. 21 A i r temperatures seldom f a l l below f r e e z i n g , and never stay that low for any length of time. Warm a i r from the P a c i f i c tends to moderate temperatures i n the S t r a i t , r e s u l t i n g i n average winter values of 2°C (January and February), with an increase a f t e r mid-February to average values of 13°C i n May and 18°C i n July and August, with midday temperatures often reaching 24°C. 1.5 OCEANOGRAPHIC CHARACTERISTICS A comprehensive analysis of the physi c a l oceanographic c h a r a c t e r i s t i c s of the S t r a i t of Georgia i s ava i l a b l e i n Waldichuk (1957). This study was based on data c o l l e c t e d over a period from 1949 to 1951, taken to be representative of the seasonal v a r i a t i o n s of 1950, and augmented by data from other oceanographic.surveys i n 1930 to 1932 and 1952 to 1953. A b r i e f review w i l l be given here, drawn mainly from Waldichuk (1957), of those oceanographic factors considered to be of importance to the d i s p e r s a l and d i s t r i b u t i o n of the Recent sediments i n the S t r a i t of Georgia. Waldichuk (1957) considered the S t r a i t of Georgia to be an oceanographically unique feature. In contrast to other B.C. fjords i t s axis runs p a r a l l e l to the coast, the freshwater inflow i s l a t e r a l rather than from one end, and there i s a connection to the open ocean at both ends. It i s neither as steep-sided nor as narrow as many of the B.C. f j o r d s , but i t s great depth and obvious o r i g i n as a g l a c i a l l y eroded and modified deep v a l l e y contrasts sharply to the estuaries of the coast a l p l a i n of the eastern U.S.A. The rate of freshwater input greatly exceeds that of evapor-ation, and although the S t r a i t receives water from many sources the Fraser River i s the most important, contributing some 80% of the t o t a l 22 freshwater input into the S t r a i t . This tremendous, l o c a l i s e d i n f l u x of l o w - s a l i n i t y water greatly complicates the oceanography of the S t r a i t , creating a highly s t r a t i f i e d s i t u a t i o n with mixing and entraining of sea-water near the r i v e r mouth. Inflow of sea-water i s mainly from the south, the e f f e c t of the northern outlets - Discovery Passage and Johnstone S t r a i t - i s very small and may be neglected when considering water movement: e s p e c i a l l y water movement i n the Central and Southern S t r a i t . Intense v e r t i c a l mixing of the e n t i r e water column occurs i n the San Juan Archipelago - Gulf Islands area. The s t r a t i f i c a t i o n patterns and fresh-water d i s t r i b u t i o n s are further complicated by e f f e c t s due to changing tides and seasons (see Waldichuk, 1957; and Figures 5, 6, and 7). 1.5.1 CIRCULATION The main factors responsible for moving water masses and determining the d i s t r i b u t i o n of water properties i n the S t r a i t of Georgia include t i d e s , r i v e r runoff, winds and s a l i n i t y gradients. Modifying these factors are the d i r e c t i v e influences of topography, with C o r i o l i s and c e n t r i f u g a l forces assuming minor r o l e s . T i d a l e f f e c t s i n the S t r a i t of Georgia are at a maximum near the Fraser River mouth, and decrease to the north. With ebbing tides the fresh-water flow i s i n the same d i r e c t i o n as that of the tide and tongues of muddy water extend across the S t r a i t , even as far as or i n t o Active Pass. Flooding tides on the other hand r e s u l t i n a rapid flow of water northward along the shore, which tends to shear o f f lobes of r i v e r water leaving clouds of brackish water moving independently under the influence of wind and tides (Waldichuk, 1957). Flooding t i d a l currents 23 D i s l r i l i n l i i m o l p r o p e l I i r s al l i m KinTai 'c ' in t l i c S l r i i i l o f ( ' c o i j M a , l>'i-1 >ni.-ii-y ]().">(). ( A ) s a l i n i l y , (1!) t c ' m p n a h u c , ( ( ' ) d e n s i t y (at). FIGURE 5: D i s t r i b u t i o n o f s a l i n i t y , t e m p e r a t u r e and d e n s i t y m e a s u r e m e n t s i n t h e S t r a i t o f G e o r g i a , F e b r u a r y 1950 ( f r o m W a l d i c h . u k , 1957 , p . 3 5 3 ) . 24 FIGURE 6: D i s t r i b u t i o n o f s a l i n i t y , temperature and d e n s i t y measurements i n the S t r a i t of G e o r g i a , June 1950 (from W a l d i c h u k , 1957 , p . 3 5 8 ) . 25 FLOOD £88 (A) Salinitv distribution at the surface on flood and ebb stages of the tide off the Fraser River estuarv. (Observed on survev, 1—S Decem-ber 19-19.) (B) Schematic sections of salinitv distribution off the Fraser Riser estuarv on flood and ebb stages of the tide. FIGURE 7: S a l i n i t y d i s t r i b u t i o n s on f l o o d and ebb t i d e s (from W a l d i c h u k , 1957, p . 3 6 6 ) . 26 are generally stronger and of longer duration on the eastern side of the S t r a i t than on the west, while the reverse i s true for ebbing t i d e s . Since the flood tides tend to set i n a northerly d i r e c t i o n , t h i s combined t i d a l flow, augmented by C o r i o l i s e f f e c t s , topographic i n f l u -ences and the closed anticlockwise wind pattern, tends to produce a general anticlockwise water c i r c u l a t i o n within the S t r a i t . Departures from t h i s general picture do occur however. Even during ebb tide a northward movement of s i l t y water from the r i v e r mouth into Burrard In l e t and beyond may be seen on a i r photographs and i s indicated by current measurements monitored continuously for one year (Dr. S. Tabata, F i s h e r i e s Research Board of Canada, o r a l comm., 1972) and casual observation. Johnston (1921), comparing old and new soundings of the Fraser River d e l t a , and Mathews and Shepard (1962), i n a s i m i l a r type of study, found i n d i c a t i o n s of heavier s i l t i n g on the northern side of the d e l t a than i n other areas. T i f f i n ' s (1969) studies i n the S t r a i t indicated that a c t i v e sedimentation i s occurring only to the north of Sand Heads. S a l i n i t y measurements (Waldichuk, 1957) support the concept of northward transport of water along the eastern side of the S t r a i t , with l o w - s a l i n i t y water from the Fraser River veering to the r i g h t almost as soon as i t enters the S t r a i t of Georgia (see Figures 5, 6 and 7). LaCroix and T u l l y (1954) o f f e r evidence of a general, o v e r a l l northward flow of water through the S t r a i t besides the general anticlockwise c i r c u l a t o r y pattern. Surface currents i n the S t r a i t are neither as well known nor as c l e a r l y understood as might be expected. Available information i s l i m i t e d to surface-current studies made with d r i f t - b o t t l e s (Waldichuk, 27 \ ' W ' A V Patterns of drift bottle recoveries from releases on a line across the Strait of Georgia and associated winds during the summer 1927. FIGURE 8: C i r c u l a t i o n p a t t e r n s i n t h e S t r a i t o f G e o r g i a d e t e r m i n e d by s u r f a c e d r i f t -b o t t l e r e c o v e r i e s ( f r o m W a l d i c h u k , . 1957 , p . 3 8 8) . 28 1957) or f r e e - f l o a t i n g current followers (Giovando and Tabata, 1970; Tabata et a l . , 1971). and to a few studies made with current meters over varying lengths of time at d i f f e r e n t anchor stations (Pickard, 1956; Huggett, 1966; Tabata et a l . , 1970; Tabata et a l . , 1971). Interpretation of d i r e c t current studies, whether made by surface d r i f t e r or stationary meters, i s complicated by the e f f e c t s that short-term factors such as winds, t i d e s , yawing of the ship, etc., have on the measurements. Recent shallow- and surface-current studies made i n the S t r a i t include those of Giovando and Tabata (1970), Tabata et a l . (1970), Tabata et a l . (1971) and Tabata et a l . (unpubl.; o r a l comm. Tabata, 1972). Tabata et a l . (unpubl.) report on the r e s u l t s obtained from moored instruments that recorded continuously f o r a period of over one year. Three mooring s i t e s were situated along a l i n e between Valdes Island and the Iona Island sewage o u t f a l l channel. Of considerable importance are the consistent, p e r s i s t e n t easterly currents recorded at the surface and 50 metres depth at the s t a t i o n i n mid-Strait (Figure 9). Giovando and Tabata (1970) used f r e e - f l o a t i n g current-followers to determine current v e l o c i t i e s and d i r e c t i o n of flow of Fraser River water subsequent to i t s entrance i n t o the S t r a i t of Georgia. They found that water from South (Main) Arm enters the S t r a i t as a surface j e t which undergoes l i t t l e l a t e r a l spreading and, i f there i s no s i g n i f i c a n t wind d r i f t , may r e t a i n i t s entrant d i r e c t i o n f o r some time (e.g. high-water slack to next low-water). The surface water may move i n a v a r i e t y of ways i n the S t r a i t : ( i ) p e rsistent northward movement on ebb as we l l as flood tides to or near to the mainland shore west of Howe Sound. 29 FIGURE 9: Schematic compilation of current directions in the Strait of Georgia. KEY Pickard 1956 Hugget 1966 (numbers refer o ^ to depths in metres at which current was measured) Giovando and Tabata 1970 ' Tabata et al. 1971 Tabata (oral comm.) 1972 Om , . , . , 50m depths at which 100m continuous current - records were obtained. 30 Subsequently the movement may be westward to mid-Strait, then northwestward, rather than immediately northwestward along the mainland shore; ( i i ) flow northward and eastward toward the mainland shore between Burrard I n l e t and South Arm; ( i i i ) westward movement to the v i c i n i t y of the Gulf Islands over a time i n t e r v a l that may encompass several t i d e s ; (iv) water entering the S t r a i t on early stages of an ebb tide can, i f wind e f f e c t s are n e g l i g i b l e , sometimes be moved southward; (v) water entering the S t r a i t at low-water slack, during i n t e r -mediate values of run-off at l e a s t , appears to turn northward immediately, and appears to undergo pe r s i s t e n t northerly movement. i Surface current speeds up to three to f i v e knots are common at times of strong ebb t i d a l flow associated with the freshet. Current v e l o c i t i e s i n the open S t r a i t are generally i n the order of one to two knots when there i s no strong wind influence. The smallest v e l o c i t y value obtained by :Giovando'ian!d'!:Tabata-. (1970) ?was/0 ;2 knot.' Water entering the S t r a i t from South Arm contributes to the formation and extension of a plume of r i v e r water north of the Arm. Extension of t h i s plume much to the south i s believed to be con t r o l l e d by wind d r i f t and t i d a l action. Tabata et al..(1971) reported on a number of observations of current movements conducted over r e l a t i v e l y short time i n t e r v a l s (less than one week). They point out that the conclusions that can be drawn from t h e i r study are v a l i d only i f the measurements are uncontam-inated by lower frequency oceanographic events. Other evidence (Tabata et a l . , 1970) suggests that s i g n i f i c a n t oceanographic v a r i a b i l i t y with time scales greater than one week do occur elsewhere i n the S t r a i t . Of primary concern for t h i s (Tabata et a l . , 1971) study was the determination of current movements around the Iona Island sewage o u t f a l l , through which treated e f f l u e n t i s released to the S t r a i t v i a an open channel that extends almost to the western edge of Sturgeon Bank. Current movements were monitored by dye-studies, f r e e - f l o a t i n g current-f followers and, occasionally, meters. North of the o u t f a l l channel and i n a zone extending to about two miles offshore, current movement was predominantly northward. Ebb t i d a l e f f e c t s were masked except for a slowing of the northward current's v e l o c i t y , although large fl o o d tides sometimes induced an ea s t e r l y flow. The northward flow eventually extends around Point Grey and may move eastward into Burrard I n l e t . Westward of the northward moving stream, surface layer v e l o c i t i e s i n d i c -ated an o v e r a l l southerly, although v a r i a b l e , flow. The net southerly movement occurs for periods of a few days at least and had not been observed before. Tabata et a l . (1971) suggest that i t may be the manifestation of a large clockwise eddy i n the ce n t r a l S t r a i t , whose persistence and frequency are not known. Its presence c o n f l i c t s with previously-held ideas that have been postulated for current flow i n the S t r a i t . Occasional southward movement of surface water from the Fraser i n the S t r a i t of Georgia i s indicated by Tabata et a l . (1970) and Giovando and Tabata (1970). L i t t l e or no current v e l o c i t y information i s a v a i l a b l e from the c e n t r a l S t r a i t on or near to banks and ridges. Some mud obviously does get deposited and trapped i n these places, but i f the sedimentation rate was the same on the banks as i t i s i n the deep basins, then no r e l i c t boulders or gravels should be found at the surface, and no 32 FIGURE 10 FIGURES 10 and 11: L i v i n g a nimals and g r a v e l l y d e p o s i t s as y e t u n b u r i e d by modern muddy sed i m e n t s . 115 f t (35 m.) dep t h , H a l i b u t Ridge. (Photo: Mr R.D. MacDonald, Geology Dept, U.B.C.) FIGURE 11 FIGURE 12 FIGURES 12 and 13: Views to the southwest a c r o s s the S t r a i t of G e o r g i a from near Sand Heads (Sand Haeds l i g h t v i s i b l e i n F i g u r e 12) showing d e m a r c a t i o n between s i l t y water from F r a s e r R i v e r d i s c h a r g e and " c l e a r " o c e a n i c water o f G e o r g i a S t r a i t . J u l y , 1971. FIGURE 13 34 sedentary attached life - f o r m s such as sponges or corals be present (see Figures 10 and 11). Consequently, i t i s suspected that currents of s u f f i c i e n t strength to prevent deposition of hemipelagic material (but not n e c e s s a r i l y strong enough to cause erosion) e x i s t around the tops and flanks of many of the ridges. Diver observations by Mr. R.D. MacDonald, Geology Dept., U.B.C, on Halibut Bank tend to confirm this suspicion. The " t i d e l i n e " demarkation of s i l t y water from " c l e a r " Georgia S t r a i t water was explained as due to compression of isohalines by the flooding t i d e by Waldichuk (1957). Tabata et a l . (1971) provide evidence from dye studies suggesting that the "ti d e l i n e " marks a shear zone between two d i s t i n c t water masses, one flowing north (the s i l t y one), and the other south. 1.5.2 FRESHWATER BUDGET The larges t source of fresh water for the S t r a i t of Georgia i s from stream runoff. This runoff i s of two types: stored; ~ from streams with headwaters i n regions of winter snow; or d i r e c t - from streams whose discharge depends on the l o c a l r a i n f a l l . By f a r the most important contributor of freshwater to the S t r a i t i s the Fraser River. It i s a stream of the stored runoff type and reaches i t s peak discharge i n l a t e June or early J u l y . Its low discharge period i s from February to A p r i l , during which time the coastal drainage area i s the only s i g n i f i c a n t contributor of fresh water to the S t r a i t . The Fraser River, contributing some 80% of the t o t a l runoff i n t o the S t r a i t , drains an area of 85,600 square miles upstream from Hope, B.C., and a further 4,500 square miles of area downstream from 35 Hope. Of the three main r i v e r mouths the greatest volume of water enters the S t r a i t v i a South Arm. North Arm passes only 10 to 15% of the t o t a l outflow, while Canoe Pass has not been a s i g n i f i c a n t channel for some years. . Mathews,r.Murray and McMillan ,(1966) summarise information a v a i l a b l e to that date on the Fraser River, i t s bed and suspended loads, flow rates, etc. Pretious (1969, 1972) and Tywonink (1972) provide more recent information on the sediment loads transported by the Fraser River. G l a c i a l streams, such as the Squamish River at the head of Howe Sound, are pri m a r i l y of the stored runoff type. Peak discharge may occur up to one month l a t e r than that of the Fraser River. Rivers flowing into the S t r a i t from Vancouver Island such as the Cowichan, Chemainus, Nanaimo, Puntledge and Campbell are predominantly of the d i r e c t runoff type, and peak runoff c l o s e l y follows periods of high p r e c i p i t a t i o n . These r i v e r s are generally of l i t t l e importance i n supplying anything other than suspended or dissolved materials to Georgia S t r a i t . They discharge into basins behind the p a r t i a l b a r r i e r of the Gulf Islands or into shallow bays. Waldichuk (1957) suggests that the i n l e t s bordering the S t r a i t of Georgia (e.g. Bute, Toba, Burrard, Saanich and Howe Sound) can be treated as separate oceanographic e n t i t i e s which have l i t t l e e f f e c t on the c h a r a c t e r i s t i c s of the Georgia S t r a i t waters, while they themselves are influenced greatly by conditions i n the S t r a i t of Georgia. They are usually " s i l l e d " somewhere along t h e i r length, the s i l l s providing e f f e c t i v e traps for bed-load sedimentary material. Probably the only contirbution they can o f f e r to the S t r a i t i s to further d i l u t e i t s surface waters and to provide some suspended sediment during freshet 36 times. Even then i t appears that t h i s material i s masked by sediment from the Fraser River. 1.6 PREVIOUS STUDIES Geological investigations i n the S t r a i t of Georgia have, u n t i l comparatively recently, been r e s t r i c t e d to d e t a i l e d studies of areas bordering the S t r a i t . Johnston's (1921, 1922, 1923) studies of the Fraser River d e l t a were for a long time the only source of information a v a i l a b l e on the Recent sediments of the S t r a i t . Mathews and Shepard (1962) duplicated some of Johnston's work i n an e f f o r t to e s t a b l i s h growth rates and sediment d i s p e r s a l patterns, among other things, for the Fraser River d e l t a . During t h e i r survey they located, described and attempted to explain some anomalous, rounded h i l l s occurring near the foot of the d e l t a f r o n t . These h i l l s have been more extensively studied by T i f f i n et a l . (1971) who confirmed e a r l i e r suggestions ( T i f f i n , 1969; Mathews and Shepard, 1962) that they may have been produced by s l i d i n g or slumping of material down the d e l t a f r o n t . The t i d a l f l a t s at Boundary Bay are described i n a p u b l i c a t i o n by K e l l e r h a l s and Murray (1969). Garrison et a l . (1969) report on the e a r l y diagenetic cementation of sands by low-magnesium c a l c i t e i n the channels of the Fraser River. More general investigations within the S t r a i t include those of Waldichuk (1954, 1957), who gave a b r i e f and very generalised d e s c r i p t i o n of the bottom sediments i n the S t r a i t , and Cockbain (1963a, 1963b) who produced, as an adjunct to h i s f o r a m i n i f e r a l studies, a report and map of the d i s t r i b u t i o n of sediments within the S t r a i t . In neither case were the sediments studied i n any d e t a i l . No d e t a i l e d study of the geology or structure of the S t r a i t had been made u n t i l 1969, when 37 T i f f i n (unpublished Ph.D. t h e s i s , I n s t i t u t e of Oceanography and Dept. of Geophysics, U n i v e r s i t y of B r i t i s h Columbia) completed a survey of the Central and Southern parts of the S t r a i t using continuous seismic-r e f l e c t i o n p r o f i l i n g techniques. Mathews, Murray and McMillan (1966) summarised f u l l y the information a v a i l a b l e to that date on the Fraser River and the nature, quantity and seasonal v a r i a b i l i t y of i t s load. They also summarised av a i l a b l e knowledge of the s e t t i n g , geomorphology, sediment d i s t r i b u t i o n s and sedimentation rates of the S t r a i t of Georgia and areas adjacent to i t (Boundary Bay, Howe Sound, Saanich I n l e t , P i t t Lake). 1.7 SAMPLING PROCEDURES 1.7.1 SHIPBOARD Sampling was car r i e d out during January, 1970, from the Canadian Naval A u x i l i a r y Vessel (CNAV) LAYMORE. A t o t a l of 358 Peterson and La Fond - Dietz grab samples, 28 large Kullenberg gravity cores and 12 small Phleger cores were c o l l e c t e d . F i f t e e n camera stations were occupied, using 50 or 100 foot f o i l s of black-and-white f i l m i n an Edgerton, Germeshausen and Grier underwater camera with strobe u n i t . The ship's o f f i c e r s were responsible for navigation and for l o c a t i n g sampling s i t e s . Most of the l a t t e r was accomplished by radar and v i s u a l f i x e s . Immediately upon r e t r i e v a l a l l samples were described i n terms of colour (against the G.S.A. rock colour chart), texture, and macrofaunal content. 38 1.7.2 LABORATORY Samples were analysed f o r g r a i n - s i z e d i s t r i b u t i o n s by combined sieve and pipette techniques, and petrographic and X-ray d i f f r a c t i o n examinations were u t i l i s e d to determine the mineralogy. Other c h a r a c t e r i s t i c s determined included organic carbon and calcium carbonate contents, cation exchange c a p a c i t i e s , oxalate-extractable inorganic oxides and hydroxides, and exchangeable base concentrations. More de t a i l e d descriptions of the methods of sample treatment and analysis are given i n the appropriate sections. Of the 358 grab samples c o l l e c t e d , only 187 were subjected to mechanical s i z e - a n a l y s i s because of the rather uniform nature of the sediments over a f a i r l y large area of the S t r a i t ; a feature recognised i n the ear l y , v i s u a l examination of samples immediately a f t e r t h e i r r e t r i e v a l . Within the text samples are referred to by a sing l e number e.g. 123, although f u l l i d e n t i f i c a t i o n i s 70-1-123, r e f e r r i n g to I.0.U.B.C. cr u i s e number 70-1. Core samples are indicated by a "C" following the sample number e.g. 123C. Samples c o l l e c t e d from the Fraser River, near Ruby Creek 12 miles east of Aggassiz, B.C., are prefixed "FR". Location of sampling s i t e s i n the S t r a i t of Georgia i s shown on Figure 2. 39 CHAPTER 2 BATHYMETRY 2.1 INTRODUCTION: The bathymetry and topographic features of the study area are shown i n Figure 2, which was interpolated from charts constructed by T i f f i n (1969). Canadian Hydrographic Service charts and f i e l d sheets, and a de t a i l e d echo-sounding survey conducted by Cockbain (1963a) i n the region of the S t r a i t north of the Fraser River d e l t a , provided the data from which the contours could be drawn. Contours are missing from areas where there i s l i t t l e information, but t h e i r omission does not a f f e c t t h i s study, which i s concerned with the deeper rather than the marginal areas of the S t r a i t . Positions of contours are believed to be accurate to within 0.5 kilometres ( T i f f i n , 1969). Nine cross-sections are presented i n Figures 14 and 15, and one l o n g i t u d i n a l section, extending from Sturgeon Bank on the Fraser Delta to Ballenas Islands at the north end of the study area, i s given i n Figure 16. V e r t i c a l exaggeration on the p r o f i l e s i s x25.8. 1:1 scale p r o f i l e s are indicated by the dashed l i n e s on some of the exaggerated f i g u r e s . Water depths on the S t r a i t reach a maximum of 433 metres, which, i s considerably greater than the depths usually encountered on the nearby continental s h e l f , but not much greater than the depths of some of the mainland f j o r d s . Off Barkley Sound the shelf a t t a i n s a maximum depth of 236 metres, with an average depth for the shelf of 200 metres (Carter, 1970). The shelf break i n Queen Charlotte Sound occurs between 183 and 275 metres (Luternauer and Murray, 1969). The percentage d i s t r i b u t i o n s of depths i n the S t r a i t are: 40 400-Figure 14: Profiles across the Strait of Georgia showing bottom topography on an exaggerated scale. Dashed line on sections AA' and CC7 are at 1-1 scale. Positions of sections are given in figure 2. 41 Figure 15 ". Profiles across the Strait of Georgia showing bottom topography on an exaggerated scale. Dashed lines represent a 1-1 scale. Positions of sections are shown in figure 2. 42 soJiaui U c o ,N o •c CO 10 II 5^ I o I I i o o <0 IQ I o o CM saJioiu Figure 16 : the low scale is shown in A profile along Ballenas Basin from Sturgeon Bank to rise between Sangster Ridge and Ballenas Islands. True V1 represented by the dashed line. figure 2. Location of this section is Km 3780 2800 1640 367 % t o t a l area T o t a l study area Area deeper than 36.6m. (20fm) Area deeper than 183m. (lOOfm) Area deeper than 366m. (200fm) 100 75 44 10 2.2 PHYSIOGRAPHIC SUBDIVISIONS It i s very often useful to unite, under a s i n g l e name, i n d i v i d u a l features or areas which are s u f f i c i e n t l y unique or d i s t i n c t i v e that reference to them or d e s c r i p t i o n of them may be f a c i l i t a t e d by such a grouping. That such a subdivision of Georgia S t r a i t i n t o d i s t i n c t i v e areas should have been done i s at once apparent from inspec-t i o n of the bathymetric chart (Figure 2). characterised by the nature of the bottom-sediments and the p h y s i c a l c h a r a c t e r i s t i c s of the water masses i n the S t r a i t . Cockbain (1963a), and l a t e r Mathews, Murray and McMillan (1966), recognised areas of the S t r a i t characterised by d i s t i n c t i v e morphologies. Although the sub-d i v i s i o n s recognised by Cockbain (1963a) and by Mathews, Murray and McMillan (1966) are s i m i l a r , the l a t t e r extended the area of t h e i r survey to include the regions of the S t r a i t west and south of the Fraser Delta. recognised by t h e i r unique combinations of morphologic, bathymetric, geolo g i c a l ( s t r u c t u r a l ) and geophysical c h a r a c t e r i s t i c s . The regions are (see Figure 17): the Fraser Delta; Area of Deep Basins; Elevated Area of Ridges; Roberts Swell and Nearby Mainland Shelf; Boundary Basin and Alden Ridge; and the Island Slope. A d e t a i l e d and comprehensive account of the structure, stratigraphy, and probable h i s t o r y of each region i s given by T i f f i n (1969). Waldichuk (1954, 1957) subdivided the S t r a i t into areas T i f f i n (1969) distinguished s i x subdivisions that could be 44 1 Fraser Delta Area. 2 Area of Deep Basins. 3 Elevated Area of Ridges. 4 Roberts Swell and Mainland Shelf. 5 Boundary Basin and Alden Ridge. 6 Island Slope. FIGURE 17." Subdivisions of the Strait of Georgia into areas of distinctive morphology. (After Tiffin. 1969). 45 2.3 DISCUSSION: The following discussion i s l a r g e l y a d e s c r i p t i o n of the bathymetric features of the S t r a i t , (see also Figure 2). The adjectives "steep," "wide," "high" etc., r e f e r to the apparent topography, as shown on the exaggerated scale c r o s s - p r o f i l e s . In true scale, slopes are much l e s s pronounced (Figures 14, 15 and 16). Johnston (1921, 1922, 1923) and Mathews and Shepard (1962) have described the Fraser River Delta i n considerable d e t a i l . Within the scope of the present study the area referred to as the Fraser River Delta i s that portion of the d e l t a seaward from the extensive t i d a l f l a t s that have developed around the r i v e r ' s mouth. The d e l t a front extends some 27 kilometres from Point Grey to Point Roberts, with active sedimentation most noticeable west and north of Sand Heads. T i d a l f l a t s extend some 9 kilometres from the land to the edge of the upper d e l t a slope. Foreset beds now almost reach the opposite side of the S t r a i t . The upper, part of the d e l t a front forms a smooth slope of between 3v/2<-to 1-V4 down toward the f l o o r of the S t r a i t . Further from the r i v e r mouth the gradient decreases to 1° or l e s s and the slope merges with bottomset beds of the northern deep basins. The only d i s r u p t i o n to the smooth slope of the d e l t a front i s caused by a protruding ridge top (Fraser Ridge) northwest of Sand Heads that i s believed to possess a Cretaceous or T e r t i a r y bedrock core (Mathews and Shepard, 1962; T i f f i n , 1969). At present i t i s almost buried by d e l t a sediments, but i t stands 370 metres above the pre-delta basin f l o o r ( T i f f i n , 1969), i n d i c a t i n g that not only was pre-delta r e l i e f i n the area considerable, but also that d e l t a i c sedimentation has been very heavy. 46 To the west of Sand Heads, near the base of the d e l t a slope, i s a group of small, rounded h i l l o c k s with a r e l i e f of 15 to 30 metres. F i r s t located by-Mathews and Shepard (1962) and described i n more d e t a i l by T i f f i n et a l . (1971), they are attributed to s l i d i n g or slumping of material from higher on the d e l t a f r o n t . South of Canoe Pass the t i d a l f l a t s become increasingly narrow and the gradient of the upper d e l t a slope increases markedly. Seawards a smooth, fea t u r e l e s s , f l a t t e n e d , dome-shaped topographic high c a l l e d Roberts Swell appears (section H-H', Figure 15) between 100 and 150 metres below the surface. Roberts Swell i s a depositional feature composed of Late or post-Pleistocene sediments, but i s not re l a t e d to the present d e l t a of the Fraser River although modern de l t a sediments o v e r l i e i t on the north ( T i f f i n , 1969). The 'southwestern margin of Roberts Swell i s a U-shaped, marrow v a l l e y that changes i n character from north to; south. Its northern portion i s smooth-floored, U-shaped i n section and not p a r t i c u l a r l y steep-sided. To the south i t becomes more V-shaped, deeper and supports quite steep f l a n k s . It i s cut deeply into Roberts Swell sediments at i t s southern end, where i t swings from a southeasterly to an e a s t e r l y trend before widening and merging with Boundary Basin. T i f f i n ' s (1969) seismic survey indicates that i t has changed from a northward sloping to a southward sloping v a l l e y as a r e s u l t of sedimentation r a i s i n g the l e v e l of the f l o o r i n the north (to about 185 metres below sea l e v e l ) , and erosion i n c i s i n g i t deeper i n the south (to over 220 metres below present mean sea l e v e l at one spot west of Boundary Basin). The roughly triangular depression of Boundary Basin occurs to the southwest of Roberts Swell. Its f l o o r i s rather more i r r e g u l a r than that of the deep basins to the north, and l i k e the southern end of 47 T r i n c o m a l i . T r o u g h i t appears t o be eroded i n t o R o b e r t s S w e l l sediments. T i f f i n was l e d to t h i s c o n c l u s i o n because of the p o s s i b i l i t y of j o i n i n g r e f l e c t i n g h o r i z o n s a c r o s s Boundary B a s i n , the e x i s t e n c e of t r u n c a t e d r e f l e c t o r s i n the Roberts S w e l l u n i t , and because the power n e c e s s a r y to or r e s p o n s i b l e f o r e r o d i n g sediments i n t h i s a r e a can be p r o v i d e d by t i d a l c u r r e n t s i n the v i c i n i t y of Boundary Pass (up t o and ex c e e d i n g 2.5 m e t r e s / s e c . ) . The b a s i n i n c r e a s e s i n d e p t h toward Boundary Pass, where the deepest p o i n t o c c u r s (269 m e t r e s ) , and the s o u t h e a s t e r n margin s l o p e s s t e e p l y up toward A l d e n Bank, which r i s e s t o w i t h i n a few metres of t h e s u r f a c e a t i t s s h a l l o w e s t p o i n t , and s l o p e s g e n t l y down on i t s e a s t e r n s i d e i n t o a s h a l l o w d e p r e s s i o n between i t and the mainland c o a s t . The s t e e p s l o p e s above R o b e r t s S w e l l a r e c o n t i n u e d t o the s o u t h e a s t around a l o n g narrow r i d g e t h a t extends t o the s o u t h e a s t from R o b e r t s P e n i n s u l a a t between 25 and 70 metres dep t h . T h i s s t r u c t u r e , R o b e r t s Reef, i s b e l i e v e d t o be composed of P l e i s t o c e n e sediments. Between R o b e r t s Reef and A l d e n Ridge t h e head of Boundary B a s i n r i s e s more g e n t l y and smoothly t o t h e n o r t h . E a s t o f P o i n t Roberts and Ro b e r t s Reef i s the b r o a d , almost f l a t - f l o o r e d , s h a l l o w (up t o about 30 metres) expanse of Boundary Bay. The e x t e n s i v e t i d a l f l a t s on t h e n o r t h s i d e of Boundary Bay a r e b u i l t , as i s much o f t h e f l o o r o f the s h e l f , on a now i n a c t i v e segment of the F r a s e r R i v e r D e l t a w h i c h was c o n s t r u c t e d a t a time when the r i v e r f l o w e d out o f , or a t l e a s t had a d i s t r i b u t a r y i n t o , t h i s r e g i o n . The term s h e l f i s used t o i n d i c a t e a zone c l o s e t o l a n d t h a t s l o p e s basinward a t a low a n g l e . The s h e l f b r e a k , which can oc c u r a t any d e p t h i n t h i s a r e a , i s then the o u t e r margin of the s h e l f where the g r a d i e n t i n c r e a s e s s u d d e n l y . The s t e e p zone between the s h e l f b r e a k and t h e b a s i n f l o o r s i s r e f e r r e d t o as the s l o p e . The s h e l f o r s l o p e on the 48 northeastern s i d e of the S t r a i t i s referred to as the Mainland shelf or slope, and on the southwestern side as the Island shelf or slope. Shelf or slope terms are v i r t u a l l y meaningless i n the region of the d e l t a , although the term slope i s used i n a loose way to r e f e r to the upper (steeper) or lower (less steep) slopes of the d e l t a f r o n t . The Mainland shelf i s well-defined i n the southeast, but i n the northwest i t i s either narrow or missing e n t i r e l y . Instead the slope extends from the shoreline to the f l o o r of the S t r a i t . The Island shelf- i s ^ c l e a r l y developed i n the region of Nanoose Harbour, Nanaimo Harbour, and along the eastern sides of Gabriola and Valdes Islands. South and north of Gabriola Reefs the Island slope has a d i f f e r e n t character. In the south the slope i s characterised by numerous ridges, a l l trending i n a southeasterly d i r e c t i o n , p a r a l l e l i n g each other and bedrock structures on the Gulf Islands. On the upper portions of the slope the ridges, may form rocky shoals or i s l e t s . North of Gabriola reefs the slope i s smooth and unbroken by ridges, tends to be steeper than In the south, and to be oversteepened i n the lower portions beneath the recent sediments of Ballenas Basin ( T i f f i n , 1969), a feature not evident to the south. In the south the ridges are close together, but tend to become more widely spaced approaching Gabriola Reefs. The trend of the ridges, and the change i n t h e i r spacing from south to north, i s s i m i l a r to the pattern of f a u l t i n g displayed i h the Nanaimo Group sediments on the adjacent Gulf Islands. North of Gabriola reefs the change i n character of the slope may be a t t r i b u t e d to a change i n the nature of the bedrock, although T i f f i n could not conclude t h i s d e f i n i t e l y from the nature of the seismic records. 49 Extending northwest from, and merging with, the lower parts of, the Fraser Delta and situated on the west side of the S t r a i t i s an area occupied by two deep basins. These basins were named Ballenas and Malaspina by Cockbain (1963a). Within the study area the basins are separated over much of t h e i r length by Sangster Ridge, although near the eastern end of Malaspina Basin only a low c o l that e x i s t s between the eastern end of Sangster Ridge and South Ridge separates the. two. The c o l i s le s s than 20 metres above the basin f l o o r at t h i s junction. Ballenas Basin, the larger of the two, extends some 65 kilometres i n a northwesterly d i r e c t i o n from Valdes Island i n the south to Ballenas Islands i n the north. For the most part the f l o o r of the basin i s wide (4 to 6 kilometres) and f l a t , sloping gently to the northwest. Depths are greater than 360 metres over most of the basin, with a maximum of 423 metres. The southeastern end of Ballenas Basin appears to have been protected from encroaching d e l t a foreset sediments by a bedrock ridge (Finger Ridge: T i f f i n , 1969). On the southern side of t h i s ridge water depths reach more than 380 metres. The northwestern margin of Ballenas Basin i s a low ridge j o i n i n g Ballenas Islands to Sangster Ridge. The bottom r i s e s gently up from the basin f l o o r to t h i s ridge, which also serves to separate Ballenas Basin from Hornby Basin (i n the northwest, but outside t h i s study area). Malaspina Basin extends northeastward of Ballenas Basin beyond the l i m i t s of the study area. The portion investigated shows a more i r r e g u l a r f l o o r than that of Ballenas Basin, and a narrower, more V-shaped p r o f i l e . Water depths i n Malaspina Basin are shallower, on an average, than i n Ballenas Basin although the deepest spot i n the Central and Southern S t r a i t (433 metres) occurs i n Malaspina Basin at the base of Round Ridge. 50 Sangster Ridge consists of two parts. The western part, which, connects to Ballenas Islands v i a a low saddle and to the platform of Lasqueti Island, i s an east-southeast trending hump that r i s e s to w i t h i n 200 metres of the surface. I t i s believed, from seismic records and from dredging, to-be of morainal o r i g i n ( T i f f i n , 1969). The eastern part of the ridge i s much smaller and consists of several separate h i l l s r i s i n g from a low base. It i s considered to have a d i f f e r e n t o r i g i n from the main, western, portion of Sangster Ridge; T i f f i n (1960) considers i t to be part Pleistocene material and p a r t l y i o f t i g n e o u s - i n s t r u s i v e o r i g i n . In the northeastern side of the S t r a i t the bedrock f l o o r slopes up toward the mainland coast (see seismic p r o f i l e s i n T i f f i n , 1969) and a number of northeast-southwest trending ridges are developed on this elevated sloping platform. Round Ridge i s a steep-sided, narrow, c o n i c a l feature situated on the north slope of Malaspina Basin and believed to comprise i n t r u s i v e igneous rocks. On the northeast side of Ballenas Basin i s South Ridge, a r e l a t i v e l y inconspicuous feature consisting of 2 separate peaks of l i m i t e d height. On the northeast side of South Ridge, r i s i n g slowly at f i r s t then abruptly above i t , i s the much more prominent structure of Halibut Ridge, which r i s e s to within 23 metres of the surface at i t s shallowest point. Halibut Ridge i s a long, narrow feature sloping gently to the northwest and southeast along i t s length, and to the northeast where a wide valley- separates i t from McCall Ridge. McCall Ridge i s the most extensive of a l l the ridges i n the Central and Southern S t r a i t of Georgia. It trends some 35 kilometres i n a northwest-southeast d i r e c t i o n p a r a l l e l to Halibut Bank and the mainland coast, and s t r i k i n g towards but o f f s e t to the west from Point Grey. The 175 metre deep, f l a t - f l o o r e d Sechelt Basin separates McCall Ridge from the steeply i n c l i n e d mainland slope of Sechelt Peninsula. The southeastern end of this basin has been cut by a deep v a l l e y that slopes down to the f l o o r of Queen Charlotte Trench some 75 metres below. Queen Charlotte Trench trends i n a northeasterly d i r e c t i o n toward Howe Sound but i s prevented from providing an open connection to Howe Sound at basin f l o o r l e v e l by a s i l l west of Bowen Island (Mathews, Murray and McMillan, 1966). CONCLUSION: The S t r a i t of Georgia can be subdivided, on the basis of morphology, bathymetry and structure i n t o d i s t i n c t i v e regions. A broad grouping i s suggested from the d e s c r i p t i o n of the various areas. A l i n e between Queen Charlotte Trench and P o r l i e r Pass separates the S t r a i t into two regions whose bottom topography i s quite d i s t i n c t , and i s r e l a t e d p r i m a r i l y to Pleistocene ( i n the northwest) or Holocene (to the southeast) deposition and/or erosion. Southeast of the l i n e mentioned above, the S t r a i t has a smooth topography associated with active and rapid deposition of sands and muds from the Fraser River. The Roberts Swell feature, likewise a broad, smooth area of deposition, i s also believed to have been formed by the Fraser River, at a time when the Fraser entered the S t r a i t from a more southerly point than at present. Boundary Basin has a smoother ou t l i n e than the topography to the north. To the northwest the topography r e f l e c t s a complex i n t e r p l a y of bedrock structure, erosion by i c e , and deposition of Pleistocene g l a c i a l and i n t e r g l a c i a l sediments. I t i s an area of extreme r e l i e f (from the 400+ metres depth of the deep basins to the 23 metre shoal of Halibut Ridge) and rugged topography, although smoothing of the topography i s slowly being accomplished by deposition and accumulation of hemi-pelagic sediments - the bottomset or pro-delta muds introduced by the Fraser River. CHAPTER THREE LITHOLOGY 3.1 INTRODUCTION Within this chapter lithologic attributes of the sediments are described and discussed. The results of the size analysis of 187 Strait of Georgia bottom-sediment samples are presented and explained. From the results of these analyses, and the observations recorded when samples were f i r s t collected, maps have been constructed of sand distributions, and of facies based on the proportions of sand (plus gravel):silt:clay in each sample. The granulometric data was submitted to factor analysis and the results of this are discussed, particularly in relation to the question of distribution and dispersal of sediments. The cores examined showed a remarkable uniformity in colour and in texture, both among cores and within a single core. With the exception of one, there was no evidence of bedding in any core. A mottled appearance to the internal surface of s p l i t cores, and the occurrence of what can be identified as burrows and mounds on the sea floor in the area of some of the core sites ( s t i l l visible even in the very poor quality photographs obtained) suggests bioturbation by bottom-dwelling organisms is an important process in homogenising the sediments. Accumulation of clays and fine s i l t s by settling from suspension is also an important factor in producing non-laminated sediments. X-ray diffraction analysis of the mineralogy in 10 subsampL taken at the surface, 10, 20, 40, 80, 150, 176, 180, 200 and 230 cm. along the length of one core indicated a similar mineralogy throughout, with no systematic variations. Microscopic examination of smear 54 s l i d e s confirmed t h i s f i n d i n g , and permitted recognition of diatoms and some r a d i o l a r i a n skeletons as w e l l . 3.2 LABORATORY METHODS Size analyses were performed by conventional sieve and pipette techniques (Krumbein and Pettijohn, 1938). Samples were homogenised p r i o r to subsampling i n case s e t t l i n g of p a r t i c l e s or f l u i d migration had occurred between the times of c o l l e c t i o n and of ana l y s i s . Two subsamples were taken, one being dried to constant weight at 120°C and used to ca l c u l a t e water content of the sediment. The other was shaken i n d i s t i l l e d water for two hours to remove soluble sea s a l t s . The material was centrifuged and the supernatant l i q u i d evaporated. Usually t h i s would r e s u l t i n an estimation of the s a l t content of the sample, but for many of the Georgia S t r a i t sediments the supernatant was discoloured a translucent or transparent, pale brownish, brownish green or greenish o l i v e colour, even a f t e r llg to 2 hours centrif u g i n g at 2800 rpm. X-ray d i f f r a c t i o n of the residue a f t e r gentle heating toward dryness indicated that the material may be i n part poorly c r y s t a l l i n e clay mineral matter, but most of i t i s l i k e l y to be c o l l o i d a l and dissolved (?) organic matter. Oxidation of the residue with 30 percent hydrogen peroxide often removed much of the dis c o l o u r a t i o n . The centrifuged sediment was mixed i n a milk-shake blender for 10 to 15 minutes with a 5 gram per l i t r e s o l u t i o n of CALGON (trade name for sodium hexametaphosphate), which was found to be an e f f e c t i v e dispersing agent. The mixture was then washed through a 230-mesh (62 micron) sieve, thoroughly washed with dispersant s o l u t i o n , and the sub-sieve s o l u t i o n c o l l e c t e d i n a s e t t l i n g tube. The s e t t l i n g tube was 55 made up to one l i t r e with d i s t i l l e d water, and was placed i n a water-bath to come to a steady temperature. Thorough s t i r r i n g of the contents of the tube and inspection of i t next day revealed whether f l o c c u l a t i o n had taken place or whether the dispersing procedure had been succe s s f u l . If i t was not, the sample was centrifuged, washed, centrifuged again, then redispersed i n fresh dispersant. The f r a c t i o n remaining on the 230-mesh sieve was washed, a i r - d r i e d , c a r e f u l l y disaggregated i f necessary, and sieved at 1/2-phi i n t e r v a l s through a nest of three inch diameter sieves (Hoskins S c i e n t i f i c L t d . ) . M a t e r i a l passing the l a s t (230 mesh) sieve was added to the s e t t l i n g tube of the same sample. Pipette aliquots were removed at times calculated according to Stokes' Law to permit the weights of material i n each phi i n t e r v a l to be obtained. Raw weights obtained by sie v i n g and from the pipette analyses were combined to cal c u l a t e weight percent per % or 1 phi i n t e r v a l r e s p e c t i v e l y f o r each sample. R e p r o d u c i b i l i t y of the technique was tested by sie v i n g the same sample more than once, and by conducting complete pipette analyses on more than one subsample of the same sample. Results are presented i n Tables II and I I I . Almost a l l samples contained s u f f i c i e n t f i n e material to require pipette a n a l y s i s , although many did not have s u f f i c i e n t sand to warrant s i e v i n g . The class l i m i t s used are those of the Wentworth (1922) grade scale (see also chart i n Folk, 1968, page 25). Raw data was processed with the aid of an IBM Systems 360 model 67 computer (UBC Computing Centre). Measures of mean g r a i n - s i z e , standard deviation, skewness and ku r t o s i s were derived from hand-plotted cumulative p r o b a b i l i t y curves using the graphical parameters of Folk 56 S i z e Weight pe r c e n t A % & e mm. 1 2 3 4 mean 0.5 0 . 71 .05 .03 . 05 100 1 0.5 .44 51 . 62 .49 . 52 .18 30 .01 1 .6 1.5 0. 35 21 .45 20. 97 21 .76 20 . 33 21.13 1 .43 6.6 . 16 .74 2 0.25 44 . 26 45. 32 44 .92 45 . 83 45.08 1 .57 3.4 . 16 . 35 2.5 0.177 27 . 34 28. 72 26 . 63 27 .01 27.42 2 .09 7 . 3 . 08 . 28 3 0.125 5 .78 3. 99 5 .40 5 . 71 5. 22 1 . 79 31 . 09 1 .6 3. 5' 0.088 .57 36 .52 . 50 .48 .21 34 .02 4 .0 4 0.0625 .14 12 .11 . 11 .12 .03 21 0 0 TABLE I I : R e p r o d u c i b i l i t y of s i e v e a n a l y s i s . Sample 82 s p l i t i n t o f o u r approximately equal subsamples. A = g r e a t e s t d i f f e r e n c e , 6 = l e a s t d i f f e r e n c e between subsamples. S i z e Wt A % 9 mm. 1 2 4 0. 0625 .539 . 581 .042 8 4.5 0. 044 0 . 581 . 581 100 5 0. 31 1. 124 0 1 .124 100 6 0. 0156 1.686 1.163 .023 1. 3 7 0. 0078 6.181 6. 395 .214 3. 3 8 0. 0039 12. 924 15.698 2 .674 17 9 0. 002 26.410 20.349 6 . 061 23 10 0. 00098 14.610 23.837 9 . 227 39 >10 36.525 31.395 5 . 130 14 X 9.60 9.55 .05 5 a 2.38 2. 25 . 13 5. 5 Table I I I p a r t 1: Sample 350. S i z e Weight pe r c e n t A % 6 % e mm. 1 2 3 4 0. 0625 0 1. 627 1.678 1. 678 100 .051 3 4.5 0. 044 .683 . 740 0 # 740 100 .057 7. 7 5 0. 031 . 341 .370 1. 342 1. 001 75 .029 2. 2 6 0 . 0156 2. 901 2.959 1.342 1. 617 54 .058 2 7 0. 0078 6. 997 8. 876 9. 396 2. 399 26 . 520 5. 5 8 0. 0039 18.089 15.533 16.107 2. 556 14 . 574 3. 2 9 0. 002 17.406 16.642 17.114 . 472 3 . 292 1. 7 10 0. 00098 14.505 15 .163 16.107 1. 602 10 .658 4. 1 >10 39.079 38.092 36.913 2. 166 6 . 987 2. 5 X 10.02 9.92 9 .90 12 1.2 .02 2 a 3.14 3. 20 3.13 • 07 2.2 .01 • 31 Table I I I p a r t 2: Sample 230 TABLE I I I : R e p r o d u c i b i l i t y o f p i p e t t e a n a l y s e s . Separate analyses of samples 350 and 230. A = g r e a t e s t d i f f e r e n c e , 6 = l e a s t d i f f e r e n c e between ana l y s e s , x = graphic mean g r a i n s i z e , a = i n c l u s i v e g r a p h i c standard d e v i a t i o n . 57 and Ward (1957). Q-mode factor analysis was performed on the granulometric data - percent weight of sediment i n each 1 phi i n t e r v a l - using a computer programme belonging to the Geology Department, U.B.C. Isopleth maps were constructed using the technique described by Cullen (1966), which assumes a continuous, l i n e a r change i n the values from any one s t a t i o n to i t s immediate neighbours. Due regard i s taken of topographic features between s t a t i o n s , and sensible, although subjective, modifications to the contours can be made by eye. 3.3 DISTRIBUTION OF BEDROCK OUTCROPS Bedrock i s exposed i n the main t i d a l channels between the islands on the west side of the S t r a i t . The determination of the outcrops as bedrock i s based l a r g e l y on negative evidence: the i n a b i l i t y to obtain grab samples from these areas despite successful t r i g g e r i n g of the grab; long, deep score marks on the soutside of the grab; the r e t r i e v a l of only i s o l a t e d cobbles and boulders from nearby sample s i t e s ; and the existence i n these areas (Boundary, Active and P o r l i e r Passes) of strong t i d a l currents that l o c a l l y exceed 6 knots. Huggett (1966) presents information obtained by the U.S. Coast and Geodetic Survey from current measurements made near Boundary Pass. Here currents are commonly up to 5 knots and constant, with bottom currents generally equalling or exceeding the speeds of surface currents. In the v i c i n i t y of these t i d a l passes the bedrock outcrops are believed to be of Upper Cretaceous Nanaimo Group sediments. 3.4 DISTRIBUTION OF GRAVELS The d i s t r i b u t i o n s of gravel and very coarse sand are considered together for two reasons: there i s often a mode i n the gravel to very 58 coarse sand range separated from modes i n the f i n e r sizes by a d i s t i n c t gap i n the s i z e d i s t r i b u t i o n ; the two siz e - c l a s s e s are believed to be ge n e t i c a l l y r e l a t e d i n so f a r as they occur e i t h e r together or separately i n areas where they are unrelated to present depositional mechanisms. Generally, the gravels are r e s t r i c t e d to the marginal areas or to the tops of the banks i n the northern part of the study area. However, the appearance of gravels i n Boundary Basin led to a t h e o r e t i c a l d i s t i n c t i o n of two types of gravel deposits: those out of equilibrium with the present sedimentary regime, considered to be r e l i c t deposits; and those located i n areas believed to be erosional, and hence considered to be lag concentrates. The p r a c t i c a l d i s t i n c t i o n i s not easy, i n f a c t i s rather subjective, being based on features of grain shape and surface texture, and upon topographic and sedimentologic considerations. R e l i c t gravels occur on upstanding features such as the ridges and i n some marginal areas. The'components tend to be angular to subangular (roundness scale of Powers, 1953) with only a few subrounded elements. Surface textures vary but tend to be rough, and may also be p i t t e d by p r e f e r e n t i a l removal of minerals from the pebbles. The pebbles r a r e l y support any form of attached animal l i f e , although sponges and sponge fragments are a common, i n t e g r a l part of the sediment. The occurrence of gravels on ridges, separated by basins or by long distances from possible sources, precludes t h e i r o r i g i n as modern deposits. There i s no known sedimentary process acting i n the S t r a i t of Georgia which could transport gravels to these areas. They are out of equilibrium with present conditions e x i s t i n g i n the S t r a i t . Their continued existence i s a function of eit h e r s u f f i c i e n t current movement around the ridges preventing deposition of a l l but a small amount of mud, or a lack of, or low rates of, sedimentation as a r e s u l t of 59 i n s u f f i c i e n t sediment reaching these s i t e s . The presence of sponges and other l i f e forms associated with these gravels suggests a maintenance of food supply and a lack of suffocating deposits of mud (Figures 10 and 11). Sponge debris has been c o l l e c t e d from the sediments on the flanks of some ridges i n d i c a t i n g that currents or, perhaps at times, v i o l e n t storms may be strong enough to move and redeposit t h i s m aterial. A lack of gravel on the bank flanks, however, suggests that the banks themselves are not presently a c t i v e as l o c a l sources of sediment. Decreasing amounts of gravel, but the continued presence of very coarse sands away from the crests of McCall and Halibut Ridges, and around Ballenas Islands, implies that the ridge deposits may have been reworked during lower stands of sea l e v e l . Lag concentrate gravels occur i n the southern part of the area of study, i n the v i c i n i t y of Point Roberts, Trincomali Trough and Boundary Basin. Here the gravels are associated with areas that show topographic and i n t e r n a l morphological features a t t r i b u t e d to a c t i v e submarine erosion (see Section 2.3). The gravel components are more commonly subrounded than angular, although a range of shapes does occur. Their surfaces are generally more p i t t e d and abraded than those of the ridge top samples. Encrustation of the pebbles with a wide v a r i e t y of l i f e forms including mussels, brachipods, barnacles, bryozoans, and worm tubes i s common. Near Point Roberts a sample with a low concentration of very coarse sands appears.to be c l o s e l y r e l a t e d to those of the ridge top samples; however, i t i s considered to be the r e s u l t of erosion of Pleistocene deposits s i m i l a r to those on nearby Roberts Peninsula. Gravels of the i s l a n d s h e l f and slope are r e l a t e d to a r e l i c t o r i g i n . Derivation from l o c a l sources, p a r t i c u l a r l y i n the area south 6 0 of Gabriola Reefs, i s a p o s s i b i l i t y , but the composition of the gravels here i s not s i g n i f i c a n t l y d i f f e r e n t from those of the ridges or the is l a n d shelf and slope to the north. 3.5 DISTRIBUTION OF SAND Figure 18 shows the d i s t r i b u t i o n of sand i n the S t r a i t of Georgia, with isopleths constructed at 5, 10, 20, 30, etc percent. The isopleths r e f e r to sand only. Had they been constructed on a sand-plus-gravel basis a s l i g h t l y modified picture would have emerged i n the v i c i n i t y of Boundary Basin. The general d i s t r i b u t i o n i s consistent with patterns derived by other methods. Sand content of the sediments i s high i n the south, decreases from the de l t a basinwards to the north and west, and basinwards from the margins of the S t r a i t . Sand content i s high i n the Roberts Swell, Boundary Basin and Alden Bank areas i n the south, along the Island Shelf and upper slope, the upper slopes of the Delta front and along the mainland slopes north of Burrard I n l e t . Proximity to source and/or the e f f e c t s of current action are r e f l e c t e d i n the d i s t r i b u t i o n of sand content i s o p l e t h s . No sand occurs i n the t i d a l channels between the Gulf or San Juan Islands. High percentages of sand are encountered i n Boundary Basin which, as has been indicated, i s considered to be an erosional feature. High sand and gravel contents here are believed due to a washing of f i n e material from older Holocene sediments, and prevention of deposition of suspended sediment now by t i d a l currents. Sand concentrations over the broad dome of Roberts Swell, west of Point Roberts, are large. In t h i s area t i d a l currents of the reversing type may exceed speeds of 30 cm/second 62 only 41 cm. above the bottom (Pickard, 1956; Waldichuk, 1957). Washed material w i l l tend to be c a r r i e d northwest or southeast and e i t h e r redeposited or- even e n t i r e l y removed from Georgia S t r a i t . The sands of Roberts Swell thus represent lag concentrates or r e l i c t sediments. A s i m i l a r explanation i s advocated for the sand and gravel contents of the bank tops - current v e l o c i t i e s are s u f f i c i e n t l y strong to prevent accumulation of muds other than as a t h i n , s u p e r f i c i a l veneer, or trapped i n the i n t e r s t i c e s between pebbles and cobbles. D i s p e r s a l trends of sediment from the Fraser River upon entering the S t r a i t are evident from the d i s t r i b u t i o n of sand. The northwards bend of the 5% and 10% sand isopleths j u s t west of Sand Heads suggests the immediate northward d e f l e c t i o n of the Fraser River plume on entering the S t r a i t , and the transport of material i n t h i s d i r e c t i o n . Decreasing sand contents from the d e l t a northwards, and from the margins basinwards, follow the c l a s s i c a l pattern of higher sand concentrations closer to source areas or to land. It has not been possible to resolve unequivocally what happens to the bed-load material of the Fraser River when i t reaches the S t r a i t of Georgia. T i f f i n et a l . (1971) considered that the bed-load,, a f t e r i n i t i a l deposition on bars arid banks, was eventually r e d i s t r i b u t e d on the extensive t i d a l f l a t s around the r i v e r ' s mouth. Johnston (1921) suggested that bed-load sediment eventually made i t s way to the d e l t a f r o n t , a f t e r periods of r e s t on bars and banks, and generally only during the freshet, where i t e i t h e r came under the influence of strong, p e r s i s t e n t , northward t i d a l currents or was buried under f i n e r material. Mathews and Shepard (1962) proposed that under the influence of the salt-water wedge that intrudes up the Fraser River to approximately near Steveston during the flood t i d e , bottom-load sediment was stopped from 63 reaching the S t r a i t . With the aid of south-setting ebb flow, the coarser material was believed to be moved to the south. Evidence from f a c t o r analysis presented l a t e r i n t h i s chapter tends to support t h i s hypothesis. However, most observations (Johnston, 1921; Waldichuk, 1957; Giovando and Tabata, 1970; Tabata et a l . , 1971; and Tabata, 1972, o r a l comm.) indicat e that north-setting f l o o d tides are stronger and of longer duration than south-setting ebb-tides on the eastern side of the S t r a i t , and that i n f a c t there i s a net northward movement of sediment by currents along the delta, f r o n t , even during ebb t i b e s . This would tend to move the bottom-load sediments to the north along with most of the suspended material. A possible explanation f o r the anomalous s i t u a t i o n of higher sand contents south of the d e l t a may be that during the freshet seaward flow from the r i v e r i s strong enough to overpower the northward moving currents even during flood t i d e s . If southward movement of Fraser River bed-load but northward transport of suspended-load was occurring on t h e i r reaching the S t r a i t of Georgia, isopleths of mean grain s i z e and of sand content should show a pattern of decreasing values more or le s s concentric about Sand Heads, since South Arm i s the most ac t i v e of the various d i s t r i b u t a r y channels of the Eraser River. Examination of Figures 18, 22, and 23 indicates that the patterns displayed by these parameters are not l o g i c a l l y consistent with southward transport of bed-load sediment, although t h i s observation i s d i a m e t r i c a l l y opposed to conclusions that can be drawn from the factor analysis (see section 3.10). Also, apart from stations 21 (on Alden Ridge), 286 (on the Island Shelf close to shore j u s t north of Nanaimo), and 351 (close to shore on the mainland side at the northwestern end of the study area), the highest sand values of the samples investigated occur at sample s i t e s 82 and 83, northwest of Point Roberts and south of Canoe Pass. While the a r e a l d i s t r i b u t i o n of sand contents could be considered consistent with southeastward transport of bed-load sand from Sand Heads, those of the mean and median grain sizes are not. Rather than a southeasterly decrease i n g r a i n - s i z e , the decrease i s northwestward, from 82 to 83, and the mud content of the samples increases i n the same d i r e c t i o n . Sediment samples c o l l e c t e d from the bed of the Fraser River at Ruby Creek, 12 miles east of Agassiz, had a lower sand content and a f i n e r mean g r a i n - s i z e than did 82 or 83. The composition of the sands from samples 82 and 83 i s ind i s t i n g u i s h a b l e from those of the Fraser River and from some of the r e l i c t Pleisotcene deposits (e.g. 354 on Halibut Ridge, and Quadra sediments at Point Grey). Since the Fraser River flows through, and derives much of i t s load from, extensive Pleistocene deposits, i t i s not su r p r i s i n g that Fraser River and ( r e l i c t ) Pleistocene sediments should be s i m i l a r i n composition. Samples 82 and 83 could therefore have been derived from either the Fraser River or from the erosion of Pleistocene deposits on or close to the present coast. Derivation by erosion from the Pleistocene material of Point Roberts i s precluded by the occurrence, closer to Point Roberts and i n shallower water, of samples that contain less sand and of f i n e r mean grain s i z e . I t i s suggested that these samples were c o l l e c t e d from an area of erosion and washing of older Fraser River d e l t a material, perhaps deposited at a time when Canoe Pass was more important as a d i s t r i b u t a r y than i t i s now. If t h i s hypothesis i s true, material removed from these s i t e s w i l l be redeposited both to north and south 65 along the d e l t a front, and may obscure or modify the expected patterns of percent sand and of mean gr a i n - s i z e d i s t r i b u t i o n s (see also Appendix I I I ) . 3.6 DISTRIBUTION OF SILT AND CLAY SIZE MATERIAL Fine to very f i n e sand, s i l t and clay comprise the bulk of the modern sediment accumulating i n the S t r a i t of Georgia (see Figure 19). Accumulation of sandy material along the margins away from the Fraser River d e l t a i s , as has been pointed out, a t t r i b u t a b l e to l o c a l d e r i v a t i o n and deposition. Figures 20, 21, 22, and 23 i n d i c a t e the d i s t r i b u t i o n of the f i n e r sediments. As can be seen from these f i g u r e s , most of the f i n e material i s currently being deposited to the west and north of the Fraser River mouth. While some i s obviously reaching bank tops and the area to the south, i t s contribution to the sedimentary makeup i n these areas i s r e l a t i v e l y minor. The f i n e f r a c t i o n s are mi n e r a l o g i c a l l y very s i m i l a r over the e n t i r e area of the S t r a i t of Georgia. The Fraser River, accounting f o r over 80% of the fresh-water inflow to the S t r a i t (Waldichuk, 1957), i s the main contributor of f i n e material, to the extent that donations from other sources are swamped and consequently i n d i s t i n g u i s h a b l e . 3.7 SAND-SILT-CLAY RATIOS The technique of p l o t t i n g proportions of s i z e components on a ternary diagram provides an invaluable basis f o r the construction of fa c i e s maps of Recent sediment d i s t r i b u t i o n s . The diagram can be subdivided i n any way that i s considered to be meaningful, and the i n d i v i d u a l subdivisions given names and used as components on a f a c i e s map. 66 The choice of end-members i s purely a r b i t r a r y but, l i k e the subdivision of the diagram, they should be components that have some sedimentological meaning. For f a c i e s maps the end-members are usually size-grades. Various s i z e i n t e r v a l s have been used (Wimberley, 1955) but the most common are the gravel, sand and mud, or sand, s i l t and clay grades. Consideration was given to u t i l i s i n g a possible break i n the s i z e d i s t r i b u t i o n s at 6 p h i ( i . e . coarser-than-6 phi, 6. to 8 phi, and finer-than-8 phi) but i t was considered to be a l i t t l e too tenuous since: (1) i t meant combining material analysed by sieving with that determined by p i p e t t i n g ; (2) the mineralogy of the coarse s i l t f r a c t i o n s i s not s i g n i f i c a n t l y d i f f e r e n t from that of the f i n e sands; and (3) i t would not s i g n i f i c a n t l y a l t e r the plo t s of samples composed of only f i n e r m aterial, much of which f e l l i nto the finer-than-6 p hi range. The f i n a l decision was to r e t a i n the conventional end-members sand, s i l t and clay. Since gravels have only r e s t r i c t e d d i s t r i b u t i o n , grouping these with sand as one end-member was not considered to detract from the i n t e r p r e t i v e value of t h i s technique f o r Georgia S t r a i t sediments. Folk (1954) and Shepard (1954) devised useful and widely used ways of presenting sediment data on tr i a n g u l a r diagrams (Figure 19). Sediments from Georgia S t r a i t have been plotted on both these schemes and the r e s u l t i n g d i s t r i b u t i o n of f a c i e s , based on subdivisions of the respective ternary diagrams, are presented i n Figures 20 and 21. While Shepard's (1954) scheme i s encountered more commonly i n the l i t e r a t u r e i t i s presented here p r i m a r i l y f o r purposes of comparison w i t h other studies. Folk's (1954) subdivision i s considered to have more advantages f or the construction of f a c i e s maps. I t u t i l i s e s a 69 Figure 21 : DISTRIBUTION OF SEDIMENT TYPES. BASED ON THE TEXTURAL CLASSIFICATION OF SHEPARD (19541. SAND GRAVEL sand (£62 micron) end-member that can be taken to represent bed-load or s a l t a t i o n - l o a d material and two end-members i n the f i n e r range, the suspended load. The suspended-load i s divided i n the proportion of c l a y - s i z e to s i l t - s i z e material that i s present i n the sample. The scheme produces what i s v i r t u a l l y a sand:mud r a t i o , which can be taken as representing the amount of washing at the s i t e of deposition. Construction of f a c i e s maps requires the drawing of only f i v e contours (90%, 50%, and 10% sand, and 1:2 and 2:1 c l a y : s i l t r a t i o s ) , the segments bounded by three of these contours thus being related d i r e c t l y to the subdivisions of the ternary diagram. The remainder of the discussion on the d i s t r i b u t i o n of f a c i e s i n the S t r a i t w i l l be based on Figure 20, a f t e r Folk's scheme. Most of the sediments i n the S t r a i t of Georgia are muds and clays, containing less than 10% sand, with a scatter of samples i n the sandy-mud and muddy sand f i e l d s . Very few samples f a l l i n the sand category (>90% sand-sized material) and i n fa c t only 15% of the samples analysed had more than 50% sand, whereas 65% contained le s s than 10% sand. The occurrence of an area of anomalously sandy, and coarse, sediments on the east side of the S t r a i t northwest of Point Roberts and southeast of Sand Heads has been discussed already. Other areas of sand deposits include: Alden Bank where wave and current action have sorted and graded older sandy sediments (?old d e l t a sediments - T i f f i n , 1969); the west side of the S t r a i t between Nanaimo and Nanoose at l o c a l i t y 286, where the sands appear to be l o c a l l y derived as well as i n part r e l i c t ; and at the f a r northwestern end of the study area, on the eastern coast (#351), where a s i m i l a r , l o c a l d erivation i s suspected. 71 South Arm of the Fraser River i s the most ac t i v e d i s t r i b u t a r y i n supplying sediments to the de l t a front and to the S t r a i t . In the v i c i n i t y of South Arm sandy s i l t s , s i l t s , and s i l t y sands grade west-wards and northwards into the muds and, eventually, clays that f l o o r the largest part of the S t r a i t . To the south, what are believed to be old de l t a foreset beds (Roberts Swell sediments, T i f f i n , 1969) are repre-sented by a zone of muddy sands which grades southwest and eastwards into f i n e r sediments of Boundary Bay. Overlying the muddy sands of Roberts Swell at i t s northwestern edge, and extending toward the northwest i s an area of sandy muds which has a broad U-shaped d i s t r i b u t i o n c l o s i n g toward the southeast. The arms of the U extend northwestward along the Island Shelf and Slope and along the mid and lower d e l t a slopes. They embrace a broad, north - south trending swath of mud that has a short northwesterly extension i n t o Ballenas Basin. To the northwest the muds grade into clays that cover the basin f l o o r s and are an i n t e g r a l part of the ridge-top sediments i n the, northwestern part of the study area. Along the axis of the Strait,, from southeast to northwest, there i s a gradation from muddy sand through sandy muds to muds and f i n a l l y clays. Where the de l t a encroaches on the S t r a i t s i l t y sand and sandy s i l t s grade l a t e r a l l y westward through sandy mud, and northward v i a s i l t s , to muds and clays. Similar gradations from sandier sediments to basin muds take place from the margins basinwards although the areal d i s t r i b u t i o n s are more compressed. 3.8 SIZE ANALYSES Most s i z e analyses, and the subsequent attempts at environ-mental discrimination using th*e?data from the grai n - s i z e d i s t r i b u t i o n or parameters derived from i t , have been developed through the study of sands and coarser sediments. The l i m i t a t i o n s involved i n the si z e - a n a l y s i s of fine-grained sediment have been repeatedly pointed out i n the l i t e r a t u r e , and many arguments have been presented against the empirical " s i z e - a n a l y s i s - t o - u l t i m a t e - p a r t i c l e s " approach for these sediments (see Gripenberg, 1934; Swift et a l . , 1972; among others). Because of t h i s , few authors have attempted to do more than merely state that dominantly muddy sediments e x i s t i n various environments. Duane (1964) for example, would not analyse samples containing more than 5% sub-sieve s i z e material. There are two possible approaches to a study of muddy sediments. Either a l l arguments against analysing t h i s type of sediment can be reviewed and considered, and t h e i r overwhelming bias against such pro-cedures accepted. Or, disregarding a l l l o g i c a l arguments to the contrary, samples can be subjected to conventional a n a l y t i c a l techniques and the res u l t s studied. I f , when mapped, the quantitative d e s c r i p t i v e parameters thus derived produce g e o l o g i c a l l y sensible areal d i s t r i b u t i o n s , with due regard to known oceanographic features of the environment of deposition, then the p r a c t i c a l r e s u l t s must take precedence over the t h e o r e t i c a l arguments. The second approach has been taken i n th i s study. Apart from Gripenberg's (1934) study of the North B a l t i c Sea sediments, few people have taken t h i s approach with fine-grained sediments. Granulometric studies of sediments usually produce a mass of data that must be reduced for more e f f i c i e n t handling. S t a t i s t i c a l treatment of sediment s i z e data has been used extensively to accomplish t h i s end. The s t a t i s t i c s used, however, have r e l i e d heavily on two important assumptions: that the size-frequency d i s t r i b u t i o n follows or approaches a log-normal (or normal, when using the log transform of the grain - s i z e In millimetres) p r o b a b i l i t y function; and that the s i z e d i s t r i b u t i o n i s continuous. I t i s apparent from the l i t e r a t u r e that 73 neither assumption i s e n t i r e l y v a l i d , and t h i s has important implications for the i n t e r p r e t a t i o n of cumulative p r o b a b i l i t y curves of sediment s i z e d i s t r i b u t i o n s . Arguments for and against the concept of normal d i s t r i b u t i o n of sediment size-frequency d i s t r i b u t i o n s have been proposed by, among others, Krumbein (1934, 1938), Krumbein and Pettijohn (1938), Doeglas (1946), Pe t t i j o h n (1957), Herdan (1960), Friedman (1962), Middleton (1962), Rogers and Schubert (1963), Rogers et a l . (1963), and Tanner (1964). Considerable evidence has been published that refutes the concept of continuity of the s i z e d i s t r i b u t i o n (Folk, 1966). Udden (1914) showed a shortage of 3 to 4 phi diameter grains i n aeolian sands. Wentworth (1933) found two gaps i n natural s i z e d i s t r i b u t i o n s at -1 phi and at 8 phi, plus a minor minimum at 3.5 phi. Minima i n the -1 to -1^/2 p h i and 4 to 4^/2 p h i ranges were noted by Hough (1942), while Pet t i j o h n (1957) records gaps at 0 to -2 phi and 3 to 5 phi. Tanner (1958, 1959), Spencer (1963) and Rogers et a l . (1963) a l l reported minima i n the s i z e d i s t r i b u t i o n s of sediments i n s i m i l a r s i z e ranges. G r i f f i t h s (1962, 1967), however, contends that the gaps are a r t i f i c i a l , and are induced by a change i n a n a l y t i c a l technique. Swift et a l . (1972) discuss evidence that suggests the break between 50 and 30 microns (415 to 5 p h i ) , commonly considered to be a n a l y t i c a l l y - i n d u c e d , i s i n f a c t r e a l . Belderson (1964) used sieves over the range 230 to 18 microns (2 to 6 p h i ) , and found that the break s t i l l occurred i n the same place. He suggested that the break was caused by p a r t i c l e s i n aggregates. Sheldon (1968) recorded the same break and considered that i t was formed n a t u r a l l y , during transportation of the sediment, not during analysis. A s i m i l a r explanation i s offered f or the o r i g i n of the "Sawdust Sand" by Pryor and Vanwie (1971). 74 The existence of minima i n p a r t i c l e s i z e d i s t r i b u t i o n s led some workers to postulate either the existence of primary populations i n the gravel, sand (+ coarse s i l t ) , and clay grades, or d e r i v a t i o n of the sediment by mixing of populations that represent d i f f e r e n t sources, d i f f e r e n t ages, or d i f f e r e n t methods of transportation (Doeglas, 1946; Folk and Ward, 1957; Tanner, 1958, 1964; Spencer, 1963; Rogers and Schubert, 1963; Sengupta, 1967; Visher, 1969). More d e t a i l e d consideration i s given l a t e r to the implications of z i g zag or polymodal cumulative p r o b a b i l i t y curves of s i z e d i s t r i b u t i o n s . An abundant l i t e r a t u r e e x i s t s on the use of c e r t a i n s t a t i s t i c a l parameters derived from g r a i n - s i z e d i s t r i b u t i o n curves to characterise sediments by t h e i r environment of deposition (for examples see: Krumbein, 1934; Krumbeih„-.and Aberdeen, 1937; Krumbein and Pettijohn, 1938; Inman, 1952; Passega, 1957; Folk and Ward, 1957; Mason and Folk, 1958.; Friedman, 1962, 1967; K o l d i j k , 1968; Moiola and Weiser, 1968; Isphording, 1972; among many others). This use, however, has been severely c r i t i c i s e d by Klovan (1966) and Solohub and Klovan (1970) on sound experimental grounds. S t a t i s t i c a l descriptors derived from the size-frequency d i s t r i b u t i o n s are important i n f a c i l i t a t i n g communication about the nature of the sediment, and permitting comparisons to be made between and among samples. The choice of which s t a t i s t i c a l measures to use, however, i s complicated by the great number a v a i l a b l e , and, e s p e c i a l l y with respect to graphical measures, there do not seem to be any good reasons for accepting any one kind over any other. Although Cadigan (1954), Davis and E r h l i c h (1970) and Isphording (1972) have shown that graphical measures give r e s u l t s that are s i g n i f i c a n t l y d i f f e r e n t from the method of moments for the same curves, the present author believes that the former may be the only t h e o r e t i c a l l y sound way of quantifying s i z e data for 75 f i n e grained sediments. Limitations are more or l e s s imposed. Polymodal curves are d i f f i c u l t to treat adequately despite Folk's (1966, 1968) contention that i n c l u s i v e graphic measures compensate for polymodality more than any other graphic solutions, and "open-ended" curves create t h e i r own problems. But as Folk (1968) points out, graphic techniques provide a quick, reasonably accurate method for approximating the measures of ce n t r a l tendency of the d i s t r i b u t i o n ( i . e . the mean and median: the average grain s i z e ) , the spread of values about the centre (the standard deviation - a measure of the degree of sorting for sediments), asymmetry (skewness) or how well-defined the curve i s (k'urtosis). Size analyses of S t r a i t of Georgia sediments are complicated by the large quantity of admixed subsieve-size material. As a r e s u l t , two methods of measuring g r a i n - s i z e may be involved: s i e v i n g , which measures a purely mechanical or p h y s i c a l s i z e based on intermediate diameter or l e a s t c r o s s - s e c t i o n a l area; and p i p e t t i n g , which measures an hydraulic equivalent to the mechanical s i z e . Because two separate properties are being measured, the r e s u l t s must be interpreted with some caution. Fortunately, many of the samples from the deeper or more northerly parts of the study area contained l i t t l e (less than 5%) or no sand, so that for these samples the question of changes i n technique did not a r i s e . Instead, they were replaced by problems of e f f e c t i v e disaggregation and d i s p e r s a l of f l o c c u l a t e d c l a y s , and of "open-endedness" of the r e s u l t i n g size-frequency d i s t r i b u t i o n s . The problem posed by fine-grained sediments i s centred on the type of information that i s required from the r e s u l t s . If a l l that i s required is. a purely mechanical separation of a sample into i t s 76 o r i g i n a l constituents, then the problem i s much reduced. I f , however, the prime reason for conducting s i z e analysis i s to obtain information about the environment of deposition, mechanical separation into component grains may w e l l be meaningless (see Swift et a l . , 1972). Separation of f l o c c u l e s into i n d i v i d u a l grains creates a s i t u a t i o n that never existed i n the f i r s t place, and r e s u l t s i n comparing sand grains that acted independently with clay p a r t i c l e s that did not. Gripenberg's work suggests that clay f l o c c u l e s a t t a i n an optimum s i z e i n sea water; therefore, to be consistent i n s i z e measurement, comparison should be made between sand-grains and clay f l o c c u l e s . Recreating conditions encountered i n nature i n the laboratory i s v i r t u a l l y impossible. No knowledge may be a v a i l a b l e of the s a l i n i t y of the water i n the depositional area, and reproduction of the concentration of f i n e , terrigenous, suspended matter i n the water column i s impossible. Even i n the Fraser River maximum concentration of suspended material r a r e l y exceeds 1 gram per l i t r e (Pretious, 1969), a concentration far too low f o r e f f e c t i v e s i z e analysis by pipette. Five samples from Georgia S t r a i t were size-analysed i n sea water to compare the si z e d i s t r i b u t i o n s obtained i n t h i s way with those r e s u l t i n g from standard procedures (washed to remove s e a - s a l t , dispersed i n CALGON). The r e s u l t i n g curves were quite i r r e g u l a r ; probably as a r e s u l t of the concentration required fo r analysis and the non-turbulent nature of the water column. During dispersion, the ultimate e f f e c t of which i s theoret-i c a l l y to disaggregate f l o c c u l e s into t h e i r component grains without reducing the s i z e of the i n d i v i d u a l p a r t i c l e s composing the f l o c c u l e s , the clay minerals, by v i r t u e of t h e i r weakly bonded p l a t y structure, may w e l l be reduced i n s i z e by cleaving. Arguments have been advanced (e.g. G r i f f i t h s , 1962, 1967) that s i z e measurements i n the sub-sand range are b a s i c a l l y measurements of degree of effectiveness of dispersion techniques, and these may only be r e l i a b l e when done at the same time, by the same technique, i n the same laboratory, by the same worker. Despite a l l t h e o r e t i c a l arguments, however, i t i s i n t e r e s t i n g to consider Figures 22 and 23, showing the d i s t r i b u t i o n s of median and mean values. Both show s i m i l a r trends and both are explicable i n a way that i s sedimentologically reasonable. If the Fraser River i s the main source of sediment for the S t r a i t i t would be expected that mean s i z e would decrease to the north and west away from the d e l t a . There i s information a v a i l a b l e suggesting that net current movement i n the S t r a i t i s to the north (see section 1.5.1), and i f t h i s i s true then the sediments should r e f l e c t t h i s movement. In f a c t , sediments probably provide the best record a v a i l a b l e of net long term current movements i n any body of water. Despite the drawbacks of f l o c c u l a t i o n e f f e c t s , i t i s evident from Figures 25 to 30 that there i s a steady f i n i n g of sediment to the north and west away from the r i v e r mouth. I t can be assumed that the va r i a t i o n s i n grain s i z e , such as the regular decrease i n mean s i z e from samples 201 to 317 along the axis of Ballenas Basin (Figure 30), are r e a l . The v a r i a t i o n cannot be a function of the a n a l y t i c a l technique, since samples were not analysed i n numerical order. Five pipettes analyses were done simultaneously, with s l i g h t staggering of withdrawal times, and samples were taken at random such that some from the northwest, some from the southeast, and some from the cen t r a l regions were analysed either together or on successive days. 78 The Implication i s that the use of s t a t i s t i c a l analysis to characterise properly treated, c o n s i s t e n t l y analysed, fine-grained sediments may be j u s t i f i e d . However, the following l i m i t a t i o n s must be r e a l i s e d : only graphical methods are v a l i d ; frequency and cumulative curves may have to be s u b j e c t i v e l y extrapolated beyond the l a s t measured s i z e i n order to span the desired range of p e r c e n t i l e values (5 to 95); and while the dispersion and a n a l y t i c a l procedures may be reproducible, and provide values that can be compared from sample to sample, they do not n e c e s s a r i l y give any i n d i c a t i o n of conditions or state of the sediment as i t was being deposited. The parameters used to describe the S t r a i t of Georgia samples are the i n c l u s i v e graphic measures of Folk and Ward (1958). Phi p e r c e n t i l e values were read d i r e c t l y from cumulative p r o b a b i l i t y curves. In many samples the cumulated amount of sediment accounted for at the time of removal of the l a s t p i p e t t e aliquot was l e s s than 70%. Inclusive graphic measures require p e r c e n t i l e values up to 95%. To obtain t h i s value the p r o b a b i l i t y curve was extrapolated beyond the l a s t measured point by extending the curve as a s t r a i g h t l i n e through and beyond the l a s t three plotted points. If curvature was encountered i n this region of the graph-, extrapolation was based on an approximate " b e s t - f i t " l i n e determined by eye through these points. Extending the curve i n t h i s way introduces a degree of s u b j e c t i v i t y to the r e s u l t s obtained - i t implies that t h i s part of the d i s t r i b u t i o n i s normal. As has already been discussed, and can be seen from Figures 25 to 37, t h i s i s not n e c e s s a r i l y a v a l i d assumption. As an approximation, however, i t does permit the d e r i v a t i o n of the desired parameters. While the median values are a l l unaffected, some of the graphic mean values and a l l of the standard deviation, skewness and 79 » k u r t o s i s parameters may be based on values read from the extrapolated portion of the curve. The f i n a l pipette aliquot was taken at a time equivalent to a l l material coarser than 0.98 micron (10 phi) e f f e c t i v e diameter having s e t t l e d below the l e v e l sampled by the pipette. This i s a l i t t l e l a r g e r than 0.6 micron l i m i t i n g diameter f o r p i p e t t i n g suggested by G r i f f i t h s (1967). It i s believed that, from the point of view of expediency and because further decrease i n p a r t i c l e s i z e r e s u l t s i n greater deviation of s e t t l i n g v e l o c i t y from Stokes' Law, extending the pipette analysis beyond t h i s (0.98 micron) i s unwarranted. The cumulative p r o b a b i l i t y curve must have a l i m i t at the f i n e end. The t h e o r e t i c a l p h y s i c a l l i m i t i s the unit c e l l thickness of the clay minerals. They can only be reduced by cleaving to a c e r t a i n thickness, and there i s probably a l i m i t i n g surface area.irelated to any p a r t i c u l a r thickness also. Grim (1968) gives values for optimum minimum dimensions of w e l l c r y s t a l l i s e d k a o l i n i t e of 0.3 microns x 0.05 microns, and of i l l i t e 0.1 microns x 0.003 microns. No values were given f o r smectite (montmorillonite group) or c h l o r i t e s . Holeman (1965) contends that the thicknesses of clay minerals may approach s i n g l e , or small multiples of, unit c e l l dimensions. He suspects montmorillonite i s able to produce flakes of 14& (1 unit c e l l ) to 20£ thickness and areal dimensions lOx to lOOx the thickness. Gibbs (1965) l i s t s s izes of clay p a r t i c l e s determined by electron microscope as: k a o l i n i t e , average 1 micron, range 0.3 to 4.0 microns; i l l i t e no average given, range 0.1 to 0.3 microns; montmorillonite average s i z e 0.1 micron, range 0.02 to 0.2 microns. Some idea of the lower l i m i t of sizes present i n S t r a i t of 80 Georgia samples may be gleaned from the r e s u l t s of s i z e separation of some samples p r i o r to X-ray d i f f r a c t i o n studies. Four samples were separated into 2.0 to 0.2 micron, 0.2 to 0.08 micron and fi n e r - t h a n -0.08 micron s i z e f r a c t i o n s using a Sharpies continuous-flow super-centrifuge. Very l i t t l e clay-mineral material was found i n the f r a c t i o n f i n e r than 0.08 microns. While t h i s i s consistent with Toombs' (1958) observations that the bottom-sediments from Bute Inlet were the r e s u l t of mechanical rather than chemical s i z e reduction, and therefore the clay sizes should be rare, i t i s at odds with other observations. Montmorillonite i s generally considered to be r e s t r i c t e d to the f i n e r clay s i z e ranges (Grim, 1968; Holeman, 1965; Whitehouse et a l . , 1960; Jackson, 1956), le s s than 0.2 microns i n diameter. Montmorillonite has been i d e n t i f i e d from the S t r a i t of Georgia sediments, and might therefore have been expected i n the f r a c t i o n f i n e r than 0.08 microns. That i t does not appear i n more than trace amounts may r e f l e c t one of two things. F i r s t , that i n f a c t no clays, montmorillonite included, are f i n e r than 0.08 microns i n the S t r a i t of Georgia sediments. If t h i s i s so, the l i m i t to the extrapolated end of the p r o b a b i l i t y curve should be somewhere between 13 and 14 p h i (0.12 and 0.06 microns r e s p e c t i v e l y ) , and commonly w i l l be rather abrupt. The second p o s s i b i l i t y i s that the r e l a t i v e lack of finer-than-0.08 micron grains i s an a r t i f a c t of the treatment process f o r these p a r t i c u l a r samples. While the aim of the pre-analysis treatment was to clean the samples, removing organic matter, amorphous oxides and extraneous poorly c r y s t a l l i s e d phases, the procedure may at the same time induce a greater degree of s r y s t a l l i n i t y i n the clay mi-hera-ls than a c t u a l l y existed i n the untreated state. This suspicion i s reinforced a f t e r comparing X-ray diffractograms obtained from untreated samples with those from samples that were treated (see next Chapter). Peaks are generally more intense, higher, sharper, and narrower at t h e i r bases, and the background much reduced f o r the treated specimens. During the course of washing some samples p r i o r to separating the sand f r a c t i o n from the mud, one sample was inadvertently overlooked f o r a period of three to four weeks, In that time the bulk of the sediment had s e t t l e d , but a transparent greenish layer, obviously denser than the overlying water, was present above the sediment. I t was expected that t h i s f l u i d would contain c o l l o i d a l organic material, but addition of hydrogen peroxide to i t produced no v i s i b l e e f f e c t . Some was X-rayed as an oriented sample on a glass s l i d e , and a regular se r i e s of 14& r e f l e c t i o n s that f i t t e d a sequence c h a r a c t e r i s t i c of c h l o r i t e , a l l well-ordered, sharp peaks, resulted. This would suggest that c h l o r i t e can e x i s t , at l e a s t i n unnatural conditions, i n p a r t i c l e s of extremely small s i z e . In a way,, the anomaly of the f i n e s t s i z e f o r clay minerals emphasises G r i f f i t h s * (1962, 1967) contention that s i z e analyses of multicomponent systems are d i f f i c u l t to i n t e r p r e t . Even among clay minerals each species has i t s range and optimum s i z e (Gibbs, 1965). Median, mean, standard deviation, skewness and kurto s i s were calculated f o r most samples, regardless of the number of modes involved on the frequency d i s t r i b u t i o n . Folk (1966, 1968) contends that the wider coverage of the curve provided f or by the i n c l u s i v e graphic"measures permits;.a more or les s s a t i s f a c t o r y i n t e r p r e t a t i o n of the curve. However, no s i n g l e parameter, or combination of them, i s adequate to describe polymodal curves. Dissection of multimodal curves into separate components w i l l be discussed i n the next section. Possibly the only s a t i s f a c t o r y 82 way of dealing with polymodal systems i s merely to ind i c a t e that they occur, the grain-sizes corresponding to the modes, and what they might i n d i c a t e . In Georgia S t r a i t multimodal curves are most commonly associated with samples containing gravels and coarse sands, and represent a combination of present-day hemi-pelagic sedimentation of muds with r e l i c t sediments, lag concentrates or l o c a l l y derived sands. Finer sediments are usually unimodal, although t h e i r cumulative p r o b a b i l i t y plots are often curved rather than s t r a i g h t (see Figures 25 to 37). Examination of Appendix I, which l i s t s the s t a t i s t i c a l parameters for each sample, shows that most Georgia S t r a i t samples are very poorly sorted. Apart from two samples taken from the d e l t a front between Sand Heads and Point Roberts (samples 82 and 83), which are w e l l sorted, the sorting ranges from poor to extremely poor. Poor sorting values i n S t r a i t of Georgia bottom sediments aretthe. result., of one of two things: i n areas of sandy or g r a v e l l y sediments the s o r t i n g i s n a t u r a l l y poor by v i r t u e of admixed hemi-pelagic mud; and i n the deeper basins, or areas characterised by muddy sediments, the sorting i s more l i k e l y a function of d i s p e r s a l and disaggregation methods i n the laboratory p r i o r to analysis. Gripenberg's (1934) research suggests that, i n nature, f i n e r sediments may a c t u a l l y be better sorted as a r e s u l t of f l o c c u l a t i o n of clay minerals. A s i m i l a r s i t u a t i o n i s argued by Rolfe (1957), who suggests that median diameters of c l a y - r i c h systems may s h i f t ten-fold from a dispersed to a f l o c c u l a t e d s i t u a t i o n . Most of the Georgia S t r a i t sediments are strongly f i n e skewed to near symmetrical. The f i n e skewness r e f l e c t s the mixing of hemi-pelagic muds with sands and gravels. Nearly symmetrical curves may occur i n 83 sandy or muddy sediments. While there i s a general trend from strongly fine-skewed through fine-skewed to nearly symmetrical curves from southeast to northwest along the axis of the S t r a i t , skewness i s not considered to be of environmental s i g n i f i c a n c e . Instead i t r e f l e c t s only the general change from coarse, sandy, r e l i c t sediments to f i n e , t o t a l l y hemi-pelagic clays i n the northwest that has already been shown to take place i n the S t r a i t . Kurtosis values calculated from the S t r a i t of Georgia samples range from 0.33 to 5.18, that i s , from very p l a t y k u r t i c to extremely l e p t o k u r t i c (Folk and Ward, 1957), with the majority i n the mesokurtic range. Southeast of the Fraser Delta values are predominantly i n the l e p t o k u r t i c and very l e p t o k u r t i c range, as i s one sample from near the r i v e r mouth at Sand Heads and some of the marginal samples at the northwestern end of the study area. P l a t y k u r t i c values are scattered s p o r a d i c a l l y , and with, ho apparent pattern, throughout the length of the' S t r a i t . Mapping the d i s t r i b u t i o n s of values f o r i n c l u s i v e graphic standard deviation, graphic skewness and graphic k u r t o s i s , using the verbal l i m i t s applied by Folk and Ward (1957), resulted i n i r r e g u l a r , more or le s s random patterns. General, but vaguely defined, trends could be established for skewness and k u r t o s i s , but not for standard deviation. It i s stressed that, because of the l i m i t a t i o n s discussed e a r l i e r , l i t t l e emphasis should be placed on values obtained a f t e r subjective extra-polation of the cumulative p r o b a b i l i t y curves well beyond the l a s t measured points. Values obtained for the median and mean, however, do show patterns that have some sedimentological meaning. 86 Areal d i s t r i b u t i o n s of the median and graphic mean s i z e are shown i n Figures 22 and 23. Since both are so s i m i l a r and because they are approximations of the same thing, they w i l l be discussed together, referred to loosely as mean grain s i z e or mean s i z e . Mean s i z e decreases r a d i a l l y , outward from Sand Heads. Along the l i n e of samples that comprise Figure 30, extending from Sand Heads northwestwards along the axis of Ballenas Basin to Ballenas Islands, the median and mean grain-sizes decrease continuously, as they do across the S t r a i t from Sand Heads to at least the foot of the Island Slope. The anomalous region of coarse, extremely well-sorted sand to the southeast of Sand Heads has been discussed above, but i t i s i n t e r e s t i n g to note that from sample #82, mean s i z e decreases both to northwest and southeast along the d e l t a f r o n t , and to the southwest across the S t r a i t . South and southeast of Sand Heads the influence of strong, reversing t i d a l currents, which have bottom current v e l o c i t i e s up to 30cm./sec. (Pickard, 1956; Waldichuk, 1957) i s r e f l e c t e d by the unusual d i s t r i b u t i o n of isopleths and the region not only of coarser mean size,, but also of a high percentage of sand. Mean s i z e increases southwestward of Roberts Swell, giving way to gravels and f i n a l l y to bedrock on the f l o o r of Boundary Pass. Eastwards the f i n e s i l t y sediments of Boundary Bay o v e r l i e the coarser, sandier Roberts Swell sediments. The Boundary Bay sediments probably r e s u l t from deposition of material derived by erosion of Pleistocene deposits of Point Roberts, and from masses of s i l t y water from the Fraser River that make t h e i r way southeastward under unusual conditions of surface flow, are blown into Boundary Bay, and cannot escape. The fast-flowing currents over Roberts Swell may carry washed material either out of the system v i a Boundary Pass, or northwestward and into deeper water on the northwest side of Roberts Swell. 87 The narrowness of the band of isopleths along the mainland and i s l a n d shelves and slopes opposite and north of the de l t a region suggests that material l o c a l l y derived i n these areas i s deposited l o c a l l y , and does not influence the main pattern of sedimentation i n the S t r a i t . The r e l i c t Pleistocene sediments of the ridges likewise do not a f f e c t the general p i c t u r e very much, i f at a l l . The main pattern of sedimentation can be seen from the distri^-'; bution of mean s i z e s . Assuming s i z e decreases continuously i n the d i r e c t i o n of transport, bulges i n the general l i n e of the isopleths should i n d i c a t e the path of maximum sediment transport. On both Figures 22 and 23 a bulge i s evident on the near-source i s o p l e t h s , i n d i c a t i n g westerly/ northwesterly transport f o r the main mass of sediment. A s i m i l a r trend i s indicated on Figure 20. Along the axis of the S t r a i t there i s a general decrease of mean grain s i z e from the southeast to northwest. The trend i s modified by a reentrant of f i n e r sediments on the west side of the S t r a i t directed toward the southeast. The f i n e r sediments may represent the remnants of an older s i t u a t i o n , when the de l t a was somewhat further away than at present: the shape of the reentrant i s a r e s u l t of the growth of the modern de l t a . In the northwestern sector: of the study area a northwesterly bulge i n the 9 p h i i s o p l e t h may in d i c a t e more rapid sedimentation into and i n the head of Ballenas Basin rather than to the north. The r e l a t i o n s h i p of the trends displayed by changes i n mean grain s i z e to suspected current patterns and t h e i r value i n helping portray net current movements w i l l be discussed l a t e r . It has been established that, although the p r e c i s i o n involved with p i p e t t e analysis of f i n e sediment may not be excellent, the r e s u l t s that were obtained produced reasonably l o g i c a l patterns when mapped. 88 Descriptive parameters of the s i z e d i s t r i b u t i o n can be obtained gr a p h i c a l l y , but care must be exercised when in t e r p r e t i n g the r e s u l t s obtained a f t e r extensive extrapolation of the f i n e end of the cumulative curve. 3.9 CUMULATIVE PROBABILITY CURVES Cumulative curves of sediment analyses p l o t t e d on p r o b a b i l i t y paper with an arithmetic scale (e.g. CODEX #3127; DIETZGEN #340-PS90; C.C & S G-23) are presented i n Figures 25 to 37. D i s t r i b u t i o n s following a normal Gaussian p r o b a b i l i t y function p l o t as s t r a i g h t l i n e s on t h i s paper because of the expanded scale i n the " t a i l " regions of the curve (Otto, 1939). Reading p e r c e n t i l e values f o r graphic s t a t i s t i c s i s f a c i l i t a t e d (see also arguments i n Folk, 1968), as are comparisons between and among various samples. P r o b a b i l i t y plots of many sediments however are not s t r a i g h t l i n e s (Tanner, 1958, 1964; Doeglas, 1946; Spencer, 1963; t h i s study), suggesting that most sediment s i z e populations do not follow a normal d i s t r i b u t i o n . Departures from a s t r a i g h t l i n e have been v a r i o u s l y explained as being the r e s u l t of: transporting mechanisms (Doeglas, 1946); truncating, censoring or f i l t e r i n g of a s i n g l e population, or mixing d i f f e r e n t populations (Tanner, 1958, 1964); simple mixing of populations (Folk and Ward, 1957; Curray, 1960; Spencer, 1963; Sengupta, 1967); and skewness of a s i n g l e population (Herdan, 1960). Fluctuations i n current strength, f l u c t u a t i n g current d i r e c t i o n s , changes i n rate and quantity of sediment supplied, and mixing of sediments of more than one source, mode of transport or age, whether n a t u r a l l y or a r t i f i c i a l l y , a l l contribute to asymmetry of d i s t r i b u t i o n curves and associated bending of p r o b a b i l i t y p l o t s . 89 Harding (1949) and Cassie (1950, 1954, 1963) discussed the use of probability curves in biological research, and described how they might be dissected into component parts on the basis that the straight sections between inflections were due to the influence on the curve of one, single component. Their assumption was that the components have distributions (plots) that follow a normal probability function. Harris (1958), Spencer (1963), Tanner (1964) and Sengupta (1967) used the assumption of normality in the size distribution of sediments to dissect non-linear cumulative probability curves from sediments or sedimentary rocks from various l o c a l i t i e s . The dissection of a polymodal curve may be feasible and practical from a mathematical point of view but is i t from a geological one? Since skewed (or asymmetrical) distributions seem to be the rule rather than the exception in nature (that i s , the size-frequency distribution curves of natural sediments are generally not normal) the basically a r t i f i c i a l process of separating polymodal curves of sediments into normally distributed components must be held to question. It may be an unjustified exercise. Figure 24 shows the positions of the samples which were used to construct Figures 25 to 37. Figures 25 and 33 to 37 are composite figures of probability curves without regard to position in the Strait, with sample 317 included in Figures 33 to 37 for comparison. Certain features are apparent upon inspection of these figures: (1) sediments from areas containing gravels are definitely polymodal and the resulting curves quite irregular; (2) of the finer samples, most have probability plots that are continuously curving and do not show definite inflexion points; (3) as the sediments become coarser, the plots become more obviously bimodal or even polymodal; and (4) along the axis of the 90 On the f o l l o w i n g seven pages are f i g u r e s composed of c u m u l a t i v e p r o b a b i l i t y curves c o n s t r u c t e d from g r a i n -s i z e f r e q u e n c y d a t a . F i g u r e s 25 t o 32 show c u m u l a t i v e p r o b a b i l i t y curves f o r groups of samples a r r a n g e d a l o n g or a c r o s s the S t r a i t o f G e o r g i a . F i g u r e 24 shows the l o c a t i o n s o f these sample groups. F i g u r e s 33 to 37 are composite diagrams of c u m u l a t i v e p r o b a b i l i t y curves from a l l a n a l y s e d samples. Sample 317 has been i n c l u d e d f o r comparison. 9 2 FIGURE 26 9 3 FIGURE 27 0-1 1 5 10 20 30 40 50 60 70 80 90 95 99 99-9 C U M U L A T I V E P E R C E N T 97 98 96 100 102 93 FIGURE 28 J I i l l l I I I I L FIGURE 29 j | I I i i i I i i | i | I I 0-1 1 5 10 20 30 40 50 60 70 80 90 95 9 9 99-9 C U M U L A T I V E P E R C E N T 95 96 9 7 98 99 S t r a i t ( i . e . along Ballenas Basin, Figure 30) from Sand Heads i n the southeast to the northwestern margin of the study area, and across the axis of the S t r a i t from the d e l t a to the Gulf Islands, progressively f i n e r sediments occur away from the d e l t a . In the southeastern portion of the area, i n the v i c i n i t y of Roberts Swell and Boundary Basin, the sediments are often coarse and t h e i r p r o b a b i l i t y p l o t s quite i r r e g u l a r . Across the axis of the S t r a i t i n the northwest (Figure 32) the change from polymodal g r a v e l l y muds to muds and back to g r a v e l l y muds r e f l e c t s the change from marginal and bank top deposits to basin sediments. Curves of f i n e sediments are often bent, which renders t h e i r i n t e r p r e t a t i o n subjective. It may be possible to approximate them by a b e s t - f i t s t r a i g h t l i n e , but these cases are few. It i s d i f f i c u l t , on a continuous curve, to construct two or more s t r a i g h t l i n e s whose resultant w i l l take the bend into account, and the resultant of these l i n e s i s often as f a r o f f the actual curve as the plotted points deviate from a s i n g l e b e s t - f i t s t r a i g h t l i n e . The lack of i n f l e x i o n points also makes the i n t e r p r e t a t i o n of the amount of mixing of populations d i f f i c u l t or impossible. G e o l o g i c a l l y , however, i t presents a p o t e n t i a l l y i n t e r e s t i n g s i t u a t i o n when the bent curve i s e n t i r e l y i n the f i n e (suspended?) sediment range. Consideration can be given to the p o s s i b i l i t y of two types of material i n the suspended load that might behave d i f f e r e n t l y i n the depositional environment. One, the coarser portion, comprises d i s c r e t e p a r t i c l e s that do not tend to f l o c c u l a t e , that are sub-equant i n shape, and are composed predominantly of quartz and feldspar grains. The other, f i n e r , portion i s composed of platy minerals that tend to behave d i f f e r e n t l y h y d r a u l i c a l l y , and to f l o c c u l a t e , p a r t i c u l a r l y i f the clay mineral s u i t e i s w e l l represented. Figures 42 and 41 show tracings of X-ray diffractograms of selected samples (the same i n both figures) of 100 the 2 to 5 micron and the 5 to 20 micron s i z e f r a c t i o n s . There seems to be an increase, even more marked i n the s i z e f r a c t i o n s f i n e r than 2 microns (Figures 44 to 49), of clay or p l a t y minerals that might suggest a mineralogical explanation for the shape of the cumulative p r o b a b i l i t y curve. Interpretation of the flexed regions of p r o b a b i l i t y curves as caused by truncation (Tanner, 1964) of coarser material was suggested by the smoothness of the curvature and the lack of d e f i n i t e i n f l e x i o n points. Arguing against t h i s explanation i s the fact that the deviation from a s t r a i g h t - l i n e p r o j e c t i o n toward the coarser from the f i n e r end of the curve i s often not continuous and may even reverse. In Figure 30 a progressive decrease i n the deviation from the s t r a i g h t - l i n e p r o j e c t i o n of the f i n e end of the curve i s evident, the curve becoming almost s t r a i g h t f o r samples 317, 311 and 289. The percentage of c l a y - s i z e material i n the samples increases i n the same d i r e c t i o n as the decrease i n deviation (away from the d e l t a and Fraser River mouth). Perhaps t h i s may provide more evidence i n favour of a mineralogical explanation of the curvature. Closer to the mouth of the Fraser the region of the greatest f l e x i n g of the curve becomes coarser, s h i f t i n g to 6 to 7 p h i from 7 to 8 p h i , and the deviation of the coarser end of the curve increases. T o t a l amount of curvature of the graph increases closer to the r i v e r mouth. This could be interpreted as follows: f o r the f i n e s t sediments, the t o t a l sediment most c l o s e l y resembles the f i n e r m aterial, the "coarse suspended load" being much reduced; closer to the source the influence of the coarser suspended material, or the increasing coarseness of the sample, i s greater and the e f f e c t on the curve consequently more pronounced. 101 Sediments that are maladjusted to the present sedimentational environment (factors of source and transport) but which may be adjusting to the oceanographic one (that i s , the t i d a l currents, etc.) often possess a p r o b a b i l i t y curve that i s marked by a coarser segment joined by a region of low or zero increase i n cumulative percentage (often between 1.5 and 3.0 phi) to a t y p i c a l l y bent f i n e r section. In some instances a minimum appears at or close to 4.0 ph i , but as t h i s i s the region of change from sieve to pipett e techniques, the p o s s i b i l i t y that i t i s a n a l y t i c a l l y induced cannot be ignored. The shapes of these curves are believed to be caused by the mixing of r e l i c t or lag sands or gravels with modern suspended material. The hiatus indicated by a low increase i n percentage of material i s probably the r e s u l t of modification (e.g. by washing) of the sand or older deposit during changing l e v e l s of the sea. Individual features of i n t e r e s t displayed by Figures 25 to 37 include: 1. Figure 25 i s constructed from samples at the southeast end of the study area. It shows the e f f e c t s of mixing f i n e material representing modern accumulation of muddy sediment, and/or r e d i s t r i b u t i o n of older, winnowed f i n e s , with r e l i c t sands and gravels. The i r r e g u l a r i t y and multicomponent nature of some of these curves i s marked. 2. Figures 26 and 27 are from samples arranged i n l i n e s across the S t r a i t from Canoe Pass to Galiano Island. Samples 81 and 82, 83 and 85 are coarser than the r e s t , which tend to have the sandy portions of t h e i r curves i n the region of 3-4 phi. Samples 82, i n p a r t i c u l a r , and 83, are the coarsest of the s u i t e , are the best sorted, and have minimal amounts of admixed f i n e s . The remaining samples, have very s i m i l a r curves, suggesting s i m i l a r conditions of deposition. 102 Explaining the curves of 82 and 83 as the r e s u l t of erosion and winnowing of f i n e s leads to the suggestion that the l i m i t s of t h i s erosion were once more extensive (basinwards) but have since narrowed to the zone between 81 and 82 and the shore, and between 85 and 83 and the shore. Addition of f i n e material now may be indicated by the higher percentage of f i n e s i n 81 and 85 r e l a t i v e to 82 and 83. 3. Superimposing Figure 28 over Figure 27 indicates that, while sample 81 i s not too d i f f e r e n t i n content of f i n e s or coarseness of sandy material from sample 100, there i s a grouping of samples from further offshore (96, 97, 98) that are extremely s i m i l a r to each other and are only s l i g h t l y f i n e r i n the sand f r a c t i o n from the group i n Figure 27. Sample 93 r e f l e c t s the addition of gravels at the coarse end of the d i s t r i b u t i o n . 4. Figure 29 portrays cumulative p r o b a b i l i t y curves of samples c o l l e c t e d along a l i n e between Sand Heads and P o r l i e r Pass. Samples close to either end of the l i n e (119, 103) show i r r e g u l a r v a r i a t i o n i n the coarser end of the d i s t r i b u t i o n . Samples 111 to 114 have d i s t r i b u t i o n s very s i m i l a r to those of 86 to 89 (Figure 27) while 115, 116, and 118 show the influence of large amounts of f i n e material. The bent curves displayed by 115 to 118 are f a i r l y t y p i c a l of those for f i n e material from samples r e l a t i v e l y close to the r i v e r mouth. 5. A l i n e of samples extending from near Sand Heads northwestward nearly to Ballenas Islands (Figure-30), and aligned along the axis of Ballenas Basin, shows a gradual increase i n fineness of the sediment to the northwest away from the d e l t a . I t i s a c l a s s i c a l example of decrease i n grain s i z e away from the source and i s associated with an increase i n clay content that i s both gradual and continuous. Samples from near the 103 top of the delta such as 129 have s i m i l a r curves as 86 to 89 of Figure 27. Curves of samples 132 and 156 to 171 are si m i l a r to those of 115 to 118 (Figure 29). Samples 196 to 317 form a package of curves representing the f i n e s t material i n the Basin. The curves of samples 289, 311 and 317, at the northwestern extremity of the basin, become inc r e a s i n g l y l i n e a r although t h e i r cumulated t o t a l s are only s l i g h t l y greater than 60% at the time of the l a s t s i z e measurement. 6. The l i n e of samples shown i n Figure 31 i s situated along the northern side of the S t r a i t , i n the deeper water between McCall Ridge and the mainland coast. A s i m i l a r separation of curves into two groups separated by a d i s t i n c t gap occurs here also. Curves for samples 161, 166 and 183 comprise the coarse group. Although f i n e r than the coarse group from Figure 30, they are d i s t i n c t l y separated from the rest of the curves i n t h i s f i g u r e . While some of the remaining samples have curves that are decidedly i r r e g u l a r at the coarser end, they are s i m i l a r o v e r a l l to the f i n e r part of the second group of Figure 30. The reason f o r the grouping i s not cle a r . It may be f o r t u i t o u s , or i t may be a r e f l e c t i o n of the clockwise current pattern that i s suspected to e x i s t i n the ce n t r a l S t r a i t (Tabata et a l . , 1971). I t could also be explained by a mineralogies change. The curves of the f i n e r group tend to be s t r a i g h t e r than those of the coarser group. As suggested above t h i s could be explained by the existence of a "coarse" and a " f i n e " suspended load (an "equant-grain" load and a "platy" load) so that the change from the bent to the s t r a i g h t e r curves might ind i c a t e a l i m i t to the region of maximum deposition of "coarser" suspended load material. However, when a l l curves are compared by overlaying Figures 25, and 33 to 37 no such gaps are obvious; the changes are e s s e n t i a l l y 104 continuously gradational from the f i n e r to the coarser samples. As a p i c t o r i a l method of presenting the r e s u l t s of granulo-metric a n a l y s i s , the cumulative p r o b a b i l i t y curve i s excellent. The mixing of populations of d i f f e r i n g s i z e c h a r a c t e r i s t i c s , whether of d i f f e r e n t sources, ages or methods of transport, i s often evident. Polymodality i s generally c l e a r l y expressed by changes i n slope or i r r e g u l a r i t i e s of the curve. The d i s s e c t i o n of such curves into t h e i r fundamental components, however, r e l i e s on the assumption that the components have d i s t r i b u t i o n s that are normal (or log-normal). This assumption i s not n e c e s s a r i l y true, and d i s s e c t i o n into components consequently not j u s t i f i e d . Vishner (1969) advocates the more extensive use of cumulative p r o b a b i l i t y p l o t s i n presenting granulometric data. He suggests that with continued presentation of data i n t h i s form i t may eventually be p o s s i b l e to d i s t i n g u i s h environments by d i s t i n c t i v e shapes of p r o b a b i l i t y p l o t s . The present writer supports these suggestions, and would extend them further to suggest more de t a i l e d i n v e s t i g a t i o n of the p o s s i b i l i t y that cumulative p r o b a b i l i t y curves are s e n s i t i v e enough to show d i f f e r e n t components i n the suspended load. 3.10 FACTOR ANALYSIS Granulometric analysis provides the basis for the c a l c u l a t i o n , or graphical d e r i v a t i o n , of s t a t i s t i c a l descriptors of the g r a i n - s i z e d i s t r i b u t i o n . Careful i n t e r p r e t a t i o n and analysis of the descriptors can be a valuable t o o l i n communicating information about a sediment, or for e l u c i d a t i n g the nature of the appropriate sedimentary processes. However, i t has been adequately shown, both by the inconsistent r e s u l t s achieved by many workers ( c f . Moiola and Wieser, 1968, and Friedman, 1967), 105 and by the comparative study of Solohub and Klovan (1970), that use of s i z e parameters derived from g r a i n - s i z e d i s t r i b u t i o n s to d i s t i n g u i s h between environments of deposition has not been p a r t i c u l a r l y successful. It has proved of l i m i t e d value for modern environments, and of no value whatever for ancient ones since previous knowledge of the environment i s required. Solohub and Klovan (1970) subjected the same s i z e data derived from samples from Lake Winnipeg to various treatments proposed i n the l i t e r a t u r e , using only those samples that were predominantly sandy since the techniques toube<evaluated'-were developed through the study of sands. They concluded that, f or the most part, unless a p r i o r i knowledge of the environment was^available, d i s t i n c t i o n s of d i f f e r e n t environments were p r a c t i c a l l y impossible-by these techniques (C-M p l o t s : Passega (1957); Inclusive Graphic Measures: Mason & Folk (1958); moment parameters: Friedman (1961); discriminant functions: Sahu (1964)). Klovan (1966) and Solohub and Klovan (1970) argued that there was no good reason for using any one type of derived parameter i n perference to any other, and pointed out that i t was f u t i l e to use r e l a t i v e l y simple b i v a r i a t e analysis to explain or describe what i s i n r e a l i t y a complex multivariate (multidimensional: see Folk and Ward, 1957) s i t u a t i o n . Sediments lend themselves to analysis by m u l t i v a r i a t e techniques, and u t i l i s i n g the weight percent of material i n each s i z e i n t e r v a l w i l l make use of a l l the information that i s usually a v a i l a b l e to s t a t i s t i c a l a n a l y sis. Like s t a t i s t i c a l techniques, factor analysis manipulates empirical data by reducing the complexity of the o r i g i n a l data matrix. It attempts to create a minimum number of new v a r i a b l e s (factors) that are l i n e a r combinations of the o r i g i n a l ones such that the new v a r i a b l e s 106 account for as much of the o r i g i n a l variance as possible. For example, Klovan (1966), i n a study of the a p p l i c a t i o n of factor analysis i n sedimento'lpgy using Krumbein and Aberdeen's (1938) Barataria Bay data, found that 97% of the variance between 69 sample vectors based on 10 components (variables) could be accounted f o r by only 3 fa c t o r s . A mathematical des c r i p t i o n of fac t o r analysis i s outside the scope of t h i s report. Excellent, d e t a i l e d accounts of the theory can be found i n Harman (1960) and C a t e l l (1952, 1965a,b). Discussion of the theory and pr a c t i c a l g g e b l o g i c a l applications of factor analysis are a v a i l a b l e i n Imbire and Purdy (1962), Imbrie and Van Andel (1964), Klovan (1966, 1968), McManus, Kelley and Creager (1969), Solohub and Klovan (1970). Factor analysis may be ca r r i e d out by two d i s t i n c t but related procedures: R-mode and Q-mode. The R-mode procedure focuses attention on n v a r i a b l e s , and calcu l a t e s r e s u l t s following the inspection of an n x n matrix of v a r i a b l e s ; i . e . , i t compares variables on the basis of a l l samples. This method often leads to t r i v i a l or, i n the case of s i z e data, meaningless geological r e s u l t s . The Q-mode procedure inspects the r e l a t i o n s h i p s between N samples on the basis of a l l (n) va r i a b l e s ; i . e . , attention i s focussed on N samples and r e s u l t s follow the inspection of an N x N matrix of re l a t i o n s h i p s between a l l pairs of samples. The S^ -mode procedure was used f o r the S t r a i t of Georgia sediments. For the Georgia S t r a i t sediments the data matrix used for f a c t o r analysis was the weight percent i n each s i z e class of 1 p h i i n t e r v a l (Appendix 11(a)). The h a l f - p h i i n t e r v a l s used for sieving were grouped into whole p h i values so that the en t i r e g r a i n - s i z e spectrum was represented by the amount of sediment contained i n equal-size class i n t e r v a l s . Since i t uses s i z e data f o r the input matrix, r e s u l t s of the 107 f a c t o r analysis are subject to the same p r a c t i c a l and t h e o r e t i c a l l i m i t a t i o n s and r e s t r i c t i o n s as have been mentioned e a r l i e r . One hundred and eighty-two samples were treated, using 15 s i z e - c l a s s e s as v a r i a b l e s . The f a c t o r analysis programme used belongs to the Geology Department, U.B.C. (Dr A.J. S i n c l a i r ) ; the computer was the IBM systems 360 model 67 i n use at the Computing Centre, U.B.C. The programme calcu l a t e s the minimum number of f a c t o r s required to account f o r 95% of the variance of the o r i g i n a l data. It then proceeds with each successive i t e r a t i o n to drop one of the factors and r e c a l c u l a t e and p r i n t the varimax f a c t o r matrix and varimax f a c t o r score matrix. Factor loadings are stored on f i l e , and can be used to construct p l o t s of f a c t o r d i s t r i b u t i o n s using the Calcomp p l o t t e r . The minimum number of factors necessary to account f o r 95% of the variance i n the S t r a i t of Georgia samples i s eight, which, considering.the nature of the input data, i s f a r too large a number of factors to consider. A four-factor model was eventually chosen, which accounted f o r 88% of the t o t a l variance (Factor I: 38.5%; Factor I I : 28.5%; Factor I I I : 16.8%; Factor IV: 6.8%). It i s not as easy to handle as the three-factor models of Klovan (1966) and Solohub and Klovan (1970). A three-factor model for the Georgia S t r a i t samples was also inspected however, although Factors I and II are the same as i n the four-factor model, the varimax factor score matrix was not e a s i l y interpreted. The varimax factor score matrix (Appendix l i e ) reveals that Factor I i s accounted for by v a r i a b l e s representing the 9, 10 and >10 p h i s i z e classes; Factor II by 6 to 8 p h i classes i n c l u s i v e , and Factor I I I by 4 to 6 p h i classes i n c l u s i v e . Factor IV was best accounted f o r by v a r i a b l e s representing the -3 to 1 p h i classes i n c l u s i v e . The f a c t o r 108 FIGURE 38: Distribution of areas characterised by factors derived from factor analysis of sediment size - data for Strait of Georgia samples. Isopleths for Factors I. II. and III are-. "'• -0-8 -09 V 109 score matrix also reveals that large negative values f o r f a c t o r loadings i n the varimax f a c t o r matrix (Appendix l i b ) are the descriptors f o r Factors I through I I I , and high p o s i t i v e loadings characterise Factor IV. A map of the d i s t r i b u t i o n of loading values f o r the various factors i s presented as Figure 38. Limits to the boundaries of the areas best described by Factors I through I I I were a r b i t r a r i l y chosen at a f a c t o r loading value of -0.6: within the areas shown to be represented by these factors the values are more negative than -0.6. Factor IV has been indicated where the loading value was greater than 0.6. With due regard to the problems involved i n analysing f i n e -grained sediments, and the consequent reservations that must be held about the p r e c i s i o n of the r e s u l t s , c e r t a i n features of the factor d i s t r i b u t i o n are worth noting, and some conclusions can be drawn. 1. The factors represent c e r t a i n s i z e grades, and may be taken to i n d i c a t e (represent) some function of the depositional process(es) (as opposed to c e r t a i n environments - see Solohub and Klovan, 1970). 2. The s i z e groups represented are: I - clays (<2.0 microns) II - medium to very f i n e s i l t s (15.6< 2 microns) III - coarse s i l t (62<15.6 microns) 3. The pattern depicted on Figure 38 i s b a s i c a l l y i d e n t i c a l to that of Figure 20, based on the sand ( + g r a v e l ) : s i l t : c l a y r a t i o s . 4. The boundary between Factors I and I I , and II and I I I ixsi located i n p o s i t i o n s that account for the gaps between bundles of cumulative p r o b a b i l i t y curves of s i m i l a r shape and slope (Figures 26, 27, 29, 30 110 and 31) I.e. the separate bundles are associated with, d i f f e r e n t f a c t o r s . 5. Since the main source of sediment f o r the S t r a i t of Georgia i s the Fraser River, the three factors should be related to t h i s s i t u a t i o n . In favour of t h i s idea i s the fac t that none of the f a c t o r s , except Factor I I I l o c a l l y on the Vancouver Island side of the S t r a i t , i s relat e d to the marginal areas. '6. The factors can be interpreted i n terms of the sediment contributed by the Fraser River. a) Factor I I I represents bed load and some coarse suspended load. b) Factor II represents the coarse f r a c t i o n of the suspended load. c) Factor I i s the f i n e portion of the suspended load. ] It has already been suggested, and some evidence e x i s t s i n support of t h i s suggestion, that the d i s t r i b u t i o n of fine-grained sediment i s to some extent m i n e r a l o g i c a l l y c o n t r o l l e d . 7. Factor I, representing mainly material that i s f i n e r than about 2.0 microns, represents the clay minerals and p a r t i c l e s that tend to f l o c c u l a t e . They are platy rather than blocky, and even i n the f l o c c u l a t e d state tend to isefctl'e somewhat slower than blocky grains of the same diameter. 8. Although clay-mineral matter i s s t i l l admixed, Factor II represents the coarse suspended f r a c t i o n composed of blocky, f r e e - s e t t l i n g grains The region of Factor II coincides with that of the muds i n Figure 20, which i s believed to be the zone of heaviest deposition of suspended sediment beyond the de l t a f r o n t . 9. Most of the sediment supplied by the Fraser River to the S t r a i t of Georgia i s contributed during the freshet. At that time the muddy, brackish, sediment-laden water leaves the r i v e r at Sand Heads as a I l l narrow j e t with a v e l o c i t y at the surface of up to 5 knots (Giovando and Tabata, 1970) and may extend a l l the way across the S t r a i t to northern Galiano Island. Current data (see map, Figure 9) suggest that the surface waters turn north from the j e t and become part of a clockwise r o t a t i o n of surface water i n the cen t r a l S t r a i t . 10. The clockwise r o t a t i o n i s r e f l e c t e d by the d i s t r i b u t i o n of Factor I I . 11. The northward transport of clays (Factor I) i s effected by spin-off of surface water toward the north out of the eddy, and by the general northward flow of deeper water along the east side of the S t r a i t north of Burrard I n l e t . 12. Factor III has been interpreted as bottom-, and some suspended-, load from the FraserERiver. The d i s t r i b u t i o n pattern of t h i s f a c t o r i s of considerable i n t e r e s t . Mathews and Shepard (1962) suggested that bottom-load sediment from the Fraser entered the S t r a i t of Georgia only during the ebb t i d e , having been stopped during flood tid e conditions by the i n t r u s i o n of a wedge of higher s a l i n i t y water along the channel bottom. During ebb t i d e flow the s a l t wedge moves out of the channel permitting the release of bottom-load sediment to the d e l t a front. Current v e l o c i t i e s are increased during the ebb, and e s p e c i a l l y during the freshet, since r i v e r flow and t i d a l outflow are i n the same d i r e c t i o n . Ebb t i d e i n Georgia S t r a i t near the r i v e r mouth sets to the south, as indicated by some of the d r i f t e r studies (Giovando and Tabata, 1970) and.the shape of the isohalines (Waldichuk, 1957). Movement of bed-load sediment southwards might occur on an ebb ti d e . A continuous, perennial, northward flow seems to exi s t along the d e l t a front close to the r i v e r mouth (Johnston, 1921; Giovando and Tabata, 1970; Tabata et a l . , 1971). This northward current should have 112 some e f f e c t on the suspended and bottom-load sediments, and i s manifest by the northward bulge i n Factor II north of Sand Heads. Once beyond the western margin of the narrow northward-flowing zone (Tabata et a l . , 1971) the bottom load.may come under the influence of the strong t i d a l currents on the east side of the S t r a i t near Point Roberts. The southward movement of bottom-load sediment, shown as a southeasterly bend i n the d i s t r i b u t i o n of Factor I I I , provides an explanation for the f i l l i n g of the northern end of Trincomali Trough that T i f f i n (1969) describes. 13. That Factor I I I should appear i n Boundary Bay may be a function of erosion and deposition of Pleistocene sediment from Point Roberts and other places around the bay. 14. Factor IV, representing the coarser material, has only a sporadic d i s t r i b u t i o n . 15. The lack of fa c t o r representation of most sediments from marginal areas and those from Roberts Swell may r e f l e c t the ( p a r t i a l l y ) r e l i c t nature of these sediments. It i s evident that factor analysis provides another useful a n a l y t i c a l t o o l with which sediments, or the data derived from them, can be manipulated and compared. Interpretation of fa c t o r analysis must s t i l l be made with care, but when done i n conjunction with other techniques and procedures i t can y i e l d information that may e i t h e r corroborate i n t e r p r e t a t i o n s made by other methods, or i t may suggest patterns that might i n d i c a t e the next procedure to attempt i n order to decipher the sedimentary processes, involved. 3.11 •WATERCCONTENT Water contents of sediments used f o r t e x t u r a l analyses were determined from the weight loss upon drying to constant weight at 120°C. 113 There Is a general trend, except toward the south and southeast, of increase i n water content away from the Fraser River mouth. This observation i s i n general agreement with Mathews and Shepard (1962) who r e l a t e i t to changes i n packing of p a r t i c l e s . It follows the same general trend as those of the median and mean gra i n - s i z e changes and clay content. Water contents are highest - up to 72% - where clay content i s high, at the northwest end of Ballenas Basin and i n Malaspina Basin. This trend i s very s i m i l a r to the observations of Inderbitzen and Simpson (1971), from studies of sediments along a g u l l i e d section of the upper San Diego Trough off Del Mar, C a l i f o r n i a , that water content i s r e l a t e d to g r a i n - s i z e , and i s r e l a t e d to depth or to topography only to the extent that g r a i n - s i z e i s . In the S t r a i t of Georgia the water content i s r e l a t e d to, i f not c o n t r o l l e d by, the clay content. Lowest values are associated with sandy well-sorted sediments (82, 83, 21). The sandy sediments of Roberts Swell have r e l a t i v e l y low water contents. 3.12 SEDIMENT COLOURS Colours of sediments were determined by comparison with the G.S.A. Rock Colour Chart. Despite the apparent p o t e n t i a l f o r objective determination of sample colours by d i f f e r e n t workers i t was i n t r i g u i n g to note that personal bias i n the i n t e r p r e t a t i o n of colours could s t i l l occur. This was manifested by d i f f e r e n t watches se l e c t i n g s l i g h t l y d i f f e r e n t values to describe the most commonly occurring colour. Changing l i g h t conditions i n s i d e the ship's laboratory and sea conditions outside, coupled with a tendency f o r marine sampling to become more than a l i t t l e boring, must have contributed to the v a r i a t i o n i n colour coding. Wet sediments, immediately upon r e t r i e v a l but, i n the case of large grab samples usually a f t e r subsampling, were compared with the 114 rock colour chart and t h e i r colours noted. In the laboratory the colours of dry sediment were noted a f t e r separation into gravel, sand and mud components. Composition determines colour i n sediments to a large degree. Gravels tend to be multi-hued, the colour depending on the source, degree of a l t e r a t i o n , and subsequent encrustation by i r o n or manganese oxides or encrusting animals. Sands likewise show a close r e l a t i o n s h i p between colour and mineralogy, and the colour changes associated with d i f f e r e n t g rain s i z e s r e f l e c t the commonly observed feature of gr a i n - s i z e control of mineralogy. Very coarse.and coarse sands tend to be multi-hued, but f i n e sands, through loss of the multicomponent grains ( e s p e c i a l l y rock fragments of igneous origin)., tend towards a more monotonous colour. Quartz and feldspar are generally the two most common constituents of the sands, tending to make the colour an o v e r a l l l i g h t greyish. Admixtures of varying proportions of ferromagnesian minerals, and fragments of dark, fine-grained rocks may modify the colour toward darker values. Muds tend to be greenish grey (10Y4/2) to o l i v e grey (5Y 3/2) or dark greenish grey (5GY 4/1). Greyish o l i v e green (5GY 3/2) i s also a common colour. Since muds are a prominent part of almost a l l samples, the majority of the wet sediments are dark and greenish or greyish o l i v e hued. On drying, the muds change to l i g h t grey (N7) or l i g h t o l i v e grey (5Y 6/1). No systematic patterns were evident i n the colour determin-ations. Some v a r i a b i l i t y occurred i n the southern part of the area, but thi s was probably the r e s u l t of the presence of sandier material with the consequent heterogeneity of colours. 115 During the course of treatment of samples p r i o r to determination of mineralogy by X—ray d i f f r a c t i o n , several chemical procedures aimed at s e l e c t i v e l y removing c e r t a i n amorphous constituents were employed. These include: oxidation of organic material with 30 percent hydrogen peroxide; removal of organic material and n o n - c r y s t a l l i n e i r o n , aluminum, manganese and s i l i c a with a c i d i c ammonium oxalate; removal of amorphous oxides of i r o n , aluminum and manganese with sodium d i t h i o n i t e - c i t r a t e -bicarbonate. Table IV shows the colour changes that occurred a f t e r the various treatments. TABLE IV - COLOUR CHANGES LN SEDIMENTS INDUCED BY SELECTIVE REMOVAL OF CONSTITUENTS SAMPLE ORIGINAL ACID AMMONIUM H ^ SODIUM DITHIONITE— COLOUR OXALATE CITRATE-BICARBONATE 53 10Y4/2 5Y4/3* 5Y4/2** : ." .N4-N3*** 145 10Y4/2 11 280 5GY4/1 " * } ** } *** r e f e r to colours of otthehe Munsell Colour Chart, and are approximately equivalent, on the G.S.A. Rock Colour Chart, to 5Y4/4, 5Y4/1 and N3-N4 respectively.' The most pronounced colour change occurred a f t e r treatment with sodium-d i t h i o n i t e - c i t r a t e - b i c a r b o n a t e , i n d i c a t i n g that amorphous oxides and hydroxides of i r o n and manganese are the prime causes of the dark colours of the muds. Exposure to the atmosphere of many of the muddy samples from the deep basins ( i . e . 280 from Ballenas Basin and 295 from Malaspina Basin) resulted i n a reddish brown colour developing at the surface and extending inwards, probably i n d i c a t i n g oxidation of ferrous i r o n . 116 Greenish, to brownish green c o l l o i d a l organic material contributes to the colour of ..the very muddy sediments. This material i s almost impossible to sediment using even a high-speed centrifuge ( i n d i c a t i n g that i t may not be p a r t i c u l a t e but due to organic pigments), but can often be removed e f f e c t i v e l y by adding 30 percent hydrogen peroxide to the sample. Limonitic stains were noted on some rock fragments, and on some grains of coarse sand. Iron s t a i n i n g of coarse sand i s apparent i n the Pleistocene sediments of Point Grey, suggesting that the stained grains i n the Georgia S t r a i t sediments may be either i n h e r i t e d by erosion of the Pleistocene, or may have developed t h e i r stains i n s i t u . 3.13 DISCUSSION: SEDIMENTATION RATES AND SEDIMENT DISPERSAL Ca l c u l a t i o n of sedimentation rates i n various parts of the S t r a i t of Georgia from the information derived from sediment studies has not been possible. The longest core c o l l e c t e d was only 3 metres, which, on the basis of rates of sedimentation calculated by other workers (see below) does not represent more than 200 to 900 years. No material was found i n the cores that could have been used for C-^ dating, and the cores were, i n the most part, monotonous homogeneous mud. Some mottling due to burrowing organisms was evident i n one or two cores, while rare i s o l a t e d , displaced s i n g l e valves of pelecypods and small twigs were encountered. Fortunately, information from other sources i s a v a i l a b l e , e s p e c i a l l y f o r sedimentation rates on the d e l t a front (see also Appendix I I I ) . From core samples taken from the subaqueous part of the d e l t a front Johnston (1921) suggested that annual increments may vary from a few inches to several feet. Off the main mouth of the r i v e r he 117 suggested an average rate of deposition of 20 feet per year, with the v a r i a t i o n ranging from a few inches to as much as 50 feet annually. Core samples from depths between 50 and 100 fathoms apparently showed no evidence of seasonal or annual l a y e r i n g , but rather were believed to be an expression of massive bedding. The sedimentation rate was postulated as 1 foot or more annually. The la c k of layering i n the cores noted by Johnston was substantiated from the: cores c o l l e c t e d f o r t h i s study. No layering was found i n any of the cores studied that were taken off the d e l t a front or i n Ballenas Basin. This contrasts sharply with the cores studied by F l e i s c h e r (1972) from the Santa Barbara Basin, C a l i f o r n i a , where layering that i s believed to be re l a t e d to flood discharge of the Santa Clara River i s conspicuous. F l e i s c h e r i d e n t i f i e d the o r i g i n of the layers on the basis of colour as well as mineralogy, the colour differences being re l a t e d to differences i n carbonate content between the normal marine muds and the r i v e r sediments. In the S t r a i t of Georgia carbonate contents i n the marine sediments are low and the colours of both r i v e r and marine sediments are s i m i l a r . Johnston (1921) and Mathews and Shepard (1962) calculated rates of d e l t a growth based on comparisons of depth soundings taken several years apart over the same areas. Comparisons of depth soundings made i n 1859 with those made i n 1919 (Johnston, 1921, p.43-44) led Johnston to be l i e v e an annual advance of the active part of the d e l t a of 27 feet per year. Mathews and Shepard (1962) compared charts composed i n 1929 by the Canadian Hydrographic Service with a chart made i n 1959 by the Public Works Department. From these they constructed hypsographic curves permitting an estimation of the annual average increment to the 118 d e l t a over the 30 year i n t e r v a l . They arrived at a f i g u r e of 28 feet per year at the 300 foot contour, although the annual advance at shallower depths was somewhat l e s s . V e r t i c a l increments were i n the order of 1 foot per year (Mathews and Shepard, 1962, Figure 7, p.1423). Cockbain (1963a) constructed an isopach map of sediment th i c k -nesses based on echosounding p r o f i l e s i n the Central S t r a i t of Georgia, between the lower slopes of the d e l t a front and Texada and Lasqueti Islands. Isopachytes were drawn at 0, 50 and 100 feet of thickness of Recent sediments. Cockbain concluded that the elevated areas, the banks and ridges, were hot covered by modern sediment, although the v a l l e y s between the ridges may contain over 100 feet of modern muds. The deep basins contain t h i c k sequences of Recent sediments, with isopachytes compressed along the basin margins suggesting both steep basin sides and a t h i c k accumulation of sediment. The deposits i n Ballenas Basin show at l e a s t three sub-bottom r e f l e c t i n g horizons p a r a l l e l i n g the surface and dipping gently from southeast to northwest. They can be followed across the basin and extend most of i t s length. Malaspina Basin did not show the same development of sub-bottom r e f l e c t o r s ; the shallowest r e f l e c t o r occurs at 150 feet , while i n Ballenas Basin the shallowest r e f l e c t o r found occurs at 50 feet. These observations were confirmed by T i f f i n (1969), who also found that whereas the r e f l e c t o r s i n Ballenas Basin dip and t h i n toward the northwest, those of Malaspina Basin dip and t h i n toward the southeast. Cockbain (1963b) also suggested that r e l a t i v e rates of s e d i -mentation could be obtained from a consideration of. the t o t a l number of foraminifers present i n any unit volume of surface sediment. Where sedimentation rates were high, the number of foraminifers would be 119 d i l u t e d , and where rates were low t h e i r numbers would be correspondingly r e l a t i v e l y higher. Low numbers of foraminifers i n the S t r a i t of Georgia thus suggested high sedimentation rates. Only b r i e f mention was given to the p o s s i b i l i t y of other f a c t o r s , such as p r o d u c t i v i t y and death rates, causing v a r i a t i o n s i n abundance of foraminifers. Thicknesses of Quaternary sediments and rates of accumulation of Holocene sediments were calculated from sparker p r o f i l e s by Mathews, Murray and McMillan (1966). In the northern central part of the S t r a i t , the accumulation rate i s given as 18 feet per thousand years (0.55 cm./yr), assuming the end of the Pleistocene to be 10,000 years B.P. In the v i c i n i t y of the Fraser River Delta, the accumulation rate was c a l c u l a t e d at 90 feet per thousand years (2.7 cm./yr). Unfortunately, the actual places i n the S t r a i t from which these rates were calculated were not indicated. An extremely high average rate of sediment accumulation i n Ballenas Basin was calculated by T i f f i n (1969) as 2 cm.'/yr. This f i g u r e i s based on the assumption that sedimentation commenced some 10,000 years ago. T i f f i n implies that t h i s rate i s rather high t h i s f a r from the d e l t a , but quotes Holtedahl (1965) as f i n d i n g an accumulation rate of 1 cm./yr i n a Norwegian f j o r d that did not have a large r i v e r to supply the sediment. However, i f an empirical compaction correction i s applied to the maximum thicknesses of sediment i n Ballenas and Malaspina Basins (260 and 230 metres r e s p e c t i v e l y ) , the corresponding thicknesses of loose sediment would be i n the order of 300+ metres, which, for a 10,000 year period of accumulation, increases the rate of deposition i n the deep basins to over 3 cm./year. Accumulation rates for sediments from areas clos e to the S t r a i t have also been established. K e l l e r h a l s and Murray (1969) proposed an 120 a v e r age r a t e o f v e r t i c a l growth o f t h e t i d a l f l a t at Boundary Bay o f 0.42 mm./yr, f o r t h e l a s t 4,351 y e a r s . I n S a a n i c h I n l e t on t h e s o u t h e a s t e r n end of Vancouver I s l a n d a s e d i m e n t a t i o n r a t e o f 12 to 18 f e e t per thousand y e a r s (0.36 t o 0.55 cm./yr) based on C l k d a t e s i s e s t i m a t e d by Mathews, Murray and M c M i l l a n (1966). T h i s p a r t i c u l a r a r e a i s o f c o n s i d e r a b l e i n t e r e s t because t h e sediment a c c u m u l a t i n g I s b i o g e n i c r a t h e r than t e r r i g e n o u s . The r e s u l t s of t h e p r e s e n t s t u d y tend t o s u b s t a n t i a t e t h e c o n c l u s i o n s r e ached i n t h e s t u d i e s c i t e d above. In t h e s o u t h e a s t e r n p a r t o f t h e a r e a , i n t h e r e g i o n o f Rob e r t s S w e l l , Boundary B a s i n , A l d e n Bank and t h e e a s t e r n end of T r i n c o m a l i Trough, s e d i m e n t a t i o n r a t e s a r e e i t h e r e x t r e m e l y low or n e g a t i v e . The b a t h y m e t r i c form o f Boundary B a s i n and t h e E a s t e r n end of T r i n c o m a l i Trough suggest a c t i v e e r o s i o n , as does e v i d e n c e from s e i s m i c p r o f i l e s ( T i f f i n , 1969), and t h e p r e s e n c e o f g r a v e l s and v e r y c o a r s e sands i n t h e s e a r e a s t h a t a r e b e l i e v e d t o be l a g c o n c e n t r a t e s t e n ds t o su p p o r t t h i s c o n t e n t i o n . Dredge h a u l s from t h e f l a n k s of T r i n c o m a l i Trough (by Dr J.W. Murray, Geology Dept, U.B.C.: dredge h a u l #10, J u l y 26, 1968: 48° 51.5'N 123° 02.7'W) r e t r i e v e d h i g h l y i r r e g u l a r c a r b o n a t e cemented c o n c r e t i o n s t h a t c o n t a i n e d s h e l l and sand d e b r i s , and were e x t e n s i v e l y b o r e d . These c o n c r e t i o n s resemble some o f th o s e d e s c r i b e d i n G a r r i s o n e t a l . (1969), which were c o l l e c t e d from an a r e a o f low sediment a c c u m u l a t i o n and v i g o r o u s wave and t i d a l c u r r e n t a c t i o n i n d i s t r i b u t a r y c h a n n e l s and from s h a l l o w - w a t e r marine l o c a l i t i e s c l o s e to t h e F r a s e r R i v e r D e l t a f r o n t . The abundant e p i - and i n - f a u n a l elements o f t h e R o b e r t s S w e l l s ediments, as w e l l as t h e g e n e r a l l y sandy n a t u r e o f t h e s e d e p o s i t s , a l s o s u g g e s t s slow, i f any, a c c u m u l a t i o n o f f i n e sediment. I n f a c t , t h e 121 shape of Roberts Swell, and the high current v e l o c i t i e s near the bottom (over 30 cm./sec; Pickard, 1956) suggests that the sediments of Roberts Swell may be being washed and the sands concentrated. Some of the washed material may be r e d i s t r i b u t e d to the northwest where currents are l e s s strong, and some to the south where they are removed from the area by the intense current action through Boundary Pass, probably to accumulate i n Juan de Fuca S t r a i t or i n more sheltered waters around the Gulf and San Juan Islands. Within Boundary Pass i t s e l f , and the other t i d a l passes among the Gulf Islands (Active Pass, P o r l i e r Pass) the e f f e c t s of t i d a l scour appear to be s u f f i c i e n t to prevent deposition of any material and to a c t u a l l y expose bedrock. Suspended material derived from the Fraser River, and sediment eroded from the Pleistocene c l i f f s around Point Roberts, that i s c a r r i e d into Boundary Bay tends to be retained and deposited there. Southwesterly winds blowing into the Bay keep the sediment-laden water trapped. The region of the Fraser River Delta, e s p e c i a l l y i n the upper parts reached i n t h i s survey, presents evidence of both a c t i v e , heavy sedimentation i n the v i c i n i t y and to the north of Sand Heads, and possible erosion southeast of Sand Heads (see also Appendix I I I ) . The anomaly of the coarse sands at sample locations 82 and 83 has already been discussed. Because of the high current v e l o c i t i e s recorded from Roberts Swell close by, the p o s s i b i l i t y of t i d a l scour and washing of older d e l t a deposits i n t h i s area cannot be discounted. Johnston (1921) could f i n d no evidence of measurable advance of the d e l t a front more than three miles south of the present Sand Heads l i g h t despite an a c t i v e growth seawards of 28 feet per year north of here. The existence of coarse sands and gravels, i n areas where they could not possibly be transported under the present sedimentary regime, and of other features to be discussed below, indicates that the bank, tops and flanks are areas of l i t t l e sediment accumulation. The sedimentological evidence also suggests, a l b e i t t e n t a t i v e l y , that sedimentation rates are higher to a shallower depth on McCall Ridge than on Halibut Ridge, and are low i n even the deeper parts of ridges i n the northwest (e.g. Sangster Ridge) and i n the area between the northwestern end of McCall Ridge and the mainland. The evidence upon which these suggestions are based includes: the existence of manganese nodules; abundant f a e c a l p e l l e t s ; the d i s t r i -bution of sands and gravels; the occurrences of large numbers of diatoms the existence of agglutinated mud lumps and some glauconite " p e l l e t s . " D i s c o i d a l concretions of earthy ferromanganese material usually about a pebbel nucleus, and poorly developed crusts or stains that give p o s i t i v e tests f or manganese have been found l o c a l l y i n the S t r a i t . D i s c o i c a l concretions were co l l e c t e d from l o c a l i t y 341, on the side of the c o l connecting the northwestern end of Sangster Ridge with the r i s e that emerges as the Ballenas Islands, and from the southern side of Sangster Ridge (dredge haul c o l l e c t e d i n 1968 by Dr J.W. Murray, U.B.C. Geology Department, from p o s i t i o n 49° 21.8'N, 124° 02.0'W). These nodules w i l l be described i n greater d e t a i l l a t e r . Low rates of sedimentation are conducive to t h e i r growth and develop-ment (Degens, 1965, p.89). Limonitic and manganiferous stains or t h i n i r r e g u l a r accretions are present on cobbles and pebbles i n other areas of the S t r a i t , notably i n the south, i n the Trincomali Trough - Boundary Basin 123 area which, has already been discussed as an area of low or negative sediment accumulation. Stains and small crusts of i r o n and manganese compounds are present on pebbles from l o c a l i t y 172, at Gabriola Reefs on the Island Shelf, and on some pebbles from ridge top samples (e.g. 354, 242). Faecal p e l l e t s have been found i n some ridge-top and i s l a n d shelf and slope samples. Their uniform s i z e , shape and colour suggests the same, but unknown, organism was responsible. They occur mainly i n the 0.3 to 0.5 mm. s i z e range, are e l l i p s o i d a l i n shape with smooth surfaces, and tend to be a l i g h t yellowish grey, which may ind i c a t e removal of organic pigments by the organism responsible. While not a conclusive i n d i c a t o r of slow sedimentation, the occurrence of these i n areas where other evidence points to slow sediment accumulation suggests that the habitat of the organism responsible was one where s e d i -mentation rates are low. No s i m i l a r p e l l e t s were discovered from muddy sediments c o l l e c t e d from areas at s i m i l a r depth but where sedimentation rates are believed to be higher. The occurrence of sands and gravels on bank tops and flanks i n p o s i t i o n s that the present sedimentary processes a c t i v e i n the S t r a i t could not place them, and the lack of s u f f i c i e n t f i n e material deposited from suspension under the present regime to bury them beyond the reach of the grab sampler, has already been discussed. The occurrence with these unburied coarse deposits of sedentary bottom-dwelling organisms such as sponges i s interpreted as strong evidence i n favour of r e l a t i v e l y slow rates of sedimentation i n these areas. Some of the larger sponge fragments have i r o n and manganese compounds accumulating within t h e i r s k e l e t a l framework and s t a i n i n g t h e i r surfaces. 124 These specimens seem to have been l y i n g i n the sediment f o r some time, and may have smaller vase sponges: growing from them. In at least one l o c a l i t y , 242 (see Figure 2), diatoms provide a conspicuous and prominent part of the sediment. The f r u s t u l e s were i d e n t i f i e d by Dr F.J.R. Taylor, I n s t i t u t e of Oceanography, U.B.C., as Coscinnodiscus c e n t r a l i s which i s found i n great abundance i n Howe Sound. They were found i n smaller quantities at other" l o c a l i t i e s and are interpreted as i n d i c a t i n g s u f f i c i e n t current a c t i v i t y to maintain a good supply of nutrients that would support an abundant diatom fauna. Other e c o l o g i c a l factors would no doubt be important, but the r e l a t i v e cleanness of the gravels, abundance of sponge debris and presence of a few, abraded foraminifer tests suggests a low sedimentation rate and at least some current a c t i v i t y . A s s o c i a t i e d commonly with f a e c a l p e l l e t s , but also from some shelf and ridge samples that did not contain p e l l e t s are i r r e g u l a r l y shaped, pale greenish, agglutinated lumps of mud. These lumps are si m i l a r i n shape to some of those i l l u s t r a t e d by Murray and Mackintosh (1968) from Queen Charlotte Sound. They are not associated with foraminifer t e s t s , and t h e i r s i z e i s not consistent. Although t h e i r o r i g i n as a function of sample preparation cannot be discounted, other p o s s i b i l i t i e s e x i s t . They may have a s i m i l a r o r i g i n to the p a r t i c l e s that make up the Eocene Sawdust Sand fromaTennessee_(Pryor/and. Vanwie, 1971) which were believed to be se l f - a c c r e t e d aggregates that grew i n an area where they were agitated by water movements. They may also represent a form of glauconite. The i r r e g u l a r cracked surface i s probably a r e s u l t of gel shrinkage. Their mineralogical composition i s s i m i l a r to that of the accompanying muds. Further consideration on the o r i g i n of the mud 125 lumps w i l l be given i n Chapter 4. In a core from sample s i t e 300 darker green lumps of q u i t e i r r e g u l a r shape, plus, smaller, more evenly sized though i r r e g u l a r l y shaped p e l l e t s , are associated with- a l a r g e number of f a e c a l p e l l e t s . A r e l a t i o n s h i p i s not suspected because of the wide range In s i z e and shape of the lumps. They occur i n greater quantity near the top of the core, decreasing i n abundance with increasing depth u n t i l they disappear at about 80 cm. X-ray d i f f r a c t i o n studies i n d i c a t e they are composed of a mixed-layer c l a y mineral that conforms to a v a r i e t y of glauconite containing a high percentage of expandable layers (probably Burst's (1958a, 1958b) type 3 glauconite (Hower, 1961)).. Conditions conducive to the development of glauconite include (Cloud, 1955; Degens, 1965); an environment with a negative oxidation p o t e n t i a l ; a v a i l a b l e potassium and i r o n ; source and presence of three-layer clays; slow sedimentation; near normal s a l i n i t y ; high organic content of the sediments. A l l . t h e s e conditions, except high organic content, are met i n Georgia S t r a i t . Hower (.1961), considering Burst's (1958a, b) models of g l a u c o n i t i s a t i o n and the r e l a t i o n s h i p between glauconite structure and the l i t h o l o g i c type of the enclosing sediment, believes that the process of glauconitisiaMons f.eflectshithe^sedimentation rate, being carried closer to completion i n an environment where sediment accumulation i s slow or negative. The glauconites from core 300 are poorly ordered, contain a large amount of expandable material and occur i n muddy sediments. Their existence permits only speculation about the sedimentation rates; i t i s probably not as high as i n the adjacent basins where the dark green lumps have not been found i n the cores or grab samples. The area i n which core 300 i s located does not appear to 126 have a thick, sediment cover (Cockbain, 1963a; T i f f i n , 1969, plates. V, VI). In summary, In the southeastern portion of the study area, sedimentation rates are low or negative with a c t i v e erosion i n Boundary Basin and the t i d a l passes between i s l a n d s , but north and northwest of a l i n e between Galiano Island and Sand Heads sedimentation rates range from high or very high on or near the d e l t a , e s p e c i a l l y to the north of Sand Heads, decreasing to the northwest but s t i l l high In the deeper basins, to low on the Island Shelf, Mainland Slope, and on the tops and upper flanks of the ridges within the S t r a i t . Sedimentologically, the S t r a i t can be considered as consisting of three b a s i c a l l y d i f f e r e n t regions: the area to the south and south-east of Sand Heads, an area of erosion; the Fraser Delta, the region of heaviest sedimentation; and the northwestern region, an area of lower rates of sedimentation where clays are accumulating. The area of the Fraser Delta includes the d e l t a front foreset beds and the muds that are t r a n s i t i o n a l to prodelta clays of the basins i n the northwest. Foreset bed sediments forming the present d e l t a now extend across the S t r a i t to the Gulf Island slope, where they lap up and onto Pleistocene sediments. The sediments also overly the north end ofd Roberts Swell, but do not cover t h i s feature. Dispe r s a l of sediment to the north and northwest over the delta area has been discussed i n sections on mean grain s i z e , sand content, s a n d : s i l t : c l a y r a t i o s , and fa c t o r a nalysis. Sediment d i s p e r s a l w i l l be determined (influenced) f i r s t by the c i r c u l a t i o n of surface waters (section 1.5.1). Subsequently, as sediment s e t t l e s from suspension, i t w i l l come under the influence of deeper currents. Suspended material might then be expected to show the e f f e c t s of net surface-water c i r c u l a t i o n patterns. Clays and cl a y - s i z e d p a r t i c l e s that stay i n suspension f o r a considerable length of time would be expected to be influenced by both surface and deep water c i r c u l a t i o n . Movement of muddy, s i l t - l a d e n water northwards, and sometimes southeastwards, along the d e l t a front i s c l e a r l y displayed on a i r photographs (e.g. Figures 12, 13) and by d i r e c t observation from a high vantage point such as on Point Grey or from the slopes of the mountains on the north shore of Burrard I n l e t . Persistent seaward movement of surface water from the Fraser River occurs during the freshet (June, J u l y ) . This i s the time_of maximum sediment i n f l u x to the S t r a i t . Bottom sediment i s deposited on the d e l t a f r o n t , on the upper and middle slopes, to be r e d i s t r i b u t e d by e i t h e r the strong, predominantly northward, t i d a l currents a c t i v e along the d e l t a f r o n t , or northwesterly winter storms, or be covered by f i n e r sediments. It contributes to the continual outward growth of the de l t a . Suspended sediment i s c a r r i e d out with the j e t of surface water, and may reach the opposite side of the S t r a i t . Once i n the S t r a i t there i s a general tendency f o r the surface water to veer/ north, whether close to the d e l t a front or near the opposite side. This w i l l bring the surface water and i t s suspended sediment load under the influence of the clockwise r o t a t i o n or eddy that i s suspected to ex i s t i n the c e n t r a l S t r a i t of Georgia.(Tabata et a l . , 1971). The water then follows a sweeping curve to the r i g h t , that takes i t eventually into Burrard I n l e t , passing over the southeastern extension of McCall Ridge. This covers the area considered to be the region of major mud deposition (coarse suspended load from cumulative p r o b a b i l i t y curves, or Factor II from the factor a n a l y s i s : see Figure 38) which extends due west from the r i v e r mouth i n a broad inverted L-shaped swath north then east into Burrard I n l e t . 128 Current movements along the east side of the S t r a i t north of Burrard Inlet are not well known but appear to be northwesterly directed at speeds i n the order of 0.1 to 0.4 knots at the surface. About the currents at depth nothing i s known, but t h e i r existence and persistence are suggested by the lack of a t h i c k muddy Recent sediment cover on Halibut or McCall Ridges even though/;the adjacent Sechelt Basin has a t h i c k accumulation (60+ metres: T i f f i n , 1969) of modern muds. The currents may be of s u f f i c i e n t strength to prevent deposition of sediment on the banks. The northwestern portion of the study area, referred to above as the region of slower accumulation or modern sediment, has an i n t r i g u i n g anomaly associated with i t . The deep ba s i n s , ~ B a l l e n a s - i n ~ p a r t i c u l a r , have t h i c k accumulation of sediment but the flanking basin sides and adjacent elevated areas have only t h i n veneers, or may even be devoid, of modern sediments. Sediments i n t h i s region are very fine-grained, generally clay minerals and other minerals of c l a y - s i z e . Two s p e c i a l problems are associated with the sediments i n the northwestern region: 1. How does the f i n e s t sediment get to the north? That i t does i s evident from the mean grain s i z e (mean and median), s a n d : s i l t : c l a y r a t i o s , and from the factor a nalysis. Along Ballenas Basin, from southeast to northwest, the mean grain s i z e decrease i s continuous. 2. Why are the ridge tops and flanks, even the ridges i n deeper water i n the northwest, r e l a t i v e l y f r e e of modern sediment while the adjacent basins have 4 to 6 times or more the thickness of Recent sediments? 129 In the. laboratory, during s i z e and mineralogical a n a l y s i s , two s i t u a t i o n s were observed" which, bear on these problems: (1) a considerable amount of the washed samples (to remove sea s a l t ) tended to remain i n suspension f o r very long periods of time, and the p o s s i b i l i t y e x i s t s that without the addition of e l e c t r o l y t e s the material would never s e t t l e ; (2) i n sea water, or with the addition of calcium c h l o r i d e , a sample r a p i d l y f l o c c u l a t e d . This l a t t e r observation, and the studies of Gripenberg (1934), of Whitehouse et a l . (1960) and Hahn and Stumm (1970), i n d i c a t e the importance of f l o c c u l a t i o n i n the s e t t i n g of the fine-grained material. Fl o c c u l e formation i n the natural environment may not be simple. Dr L.M. Lavkulich (Dept of S o i l Science, U.B.C.) suggests that i n a system of r e l a t i v e l y low concentration such as t h i s one i s supposed to be, the f l o c c u l e s may form and break up continuously. It i s p o s s i b l e , therefore, that some s i z e f r a c t i o n a t i o n may be achieved i n suspension. Under the p h y s i c a l conditions of wind or wave generated turbulence, formation and disaggregation of f l o c c u l e s may be occurring during d i s p e r s a l of the suspended sediment, and s i z e f r a c t i o n a t i o n accomplished i n t h i s manner. On dropping below the l e v e l of more intense turbulence, and into water of higher s a l i n i t y , the f l o c c u l e s may remain formed and s e t t l e under gavity while at the same time being transported by the slower, northerly d i r e c t e d , deeper water currents. A model or mechanism for sedimentation i n the northwestern region must account for the differences i n sediment thickness over the banks and i n the basins. Recent sediment thicknesses i n Ballenas Basin, while varying w i t h bedrock topography, are a maximum of 260 metres and an average of 200 metres. Within the sediment p i l e numerous p a r a l l e l 130 r e f l e c t i n g horizons occur, generally thinning to the" northwest and dipping i n the same d i r e c t i o n at v e r y s l i g h t angles ( T i f f i n , 1969). The i n t e r n a l r e f l e c t o r s may be more obvious nearer the d e l t a , and may disappear before reaching the f a r northwestern end of the basin. The source of the sediment, as determined by thinning of i n t e r n a l r e f l e c t i n g horizons ( T i f f i n , 1969), i s the Fraser River. Sediment must reach the northwestern end of the area by one or both of two mechanisms: s e t t l i n g of material held i n suspension; and by t r a c t i o n or turbid currents along the bottom. S e t t l i n g of suspended material should t h e o r e t i c a l l y r e s u l t i n an even blanket of sediment over everything, the thickness of the blanket depending on the distance from the r i v e r mouth. It would be expected therefore that i n the deeper areas, presumably out of the influence of even moderate currents, such as the low saddle connecting the northwest and southeast segments of Sangster Ridge, the thickness of the sediment mantle should be uniform from "ridge" top to adjacent basin. In f a c t , the basin sediments are 4 to 6 times thicker than those on the adjacent saddle ( T i f f i n , 1969). Other ridges and many of the basin walls and ridge sides are devoid of s i g n i f i c a n t modern sediment cover. Very often the f l a t basin f l o o r meets the adjacent ridge flank abruptly. There i s no evidence on the f l o o r of the basins adjacent to the sidewalls that would suggest removal of material by s l i d i n g or slumping. Although there are no current measurements at depth i n the northern section of the S t r a i t , currents of s u f f i c i e n t strength to keep the ridge tops and flanks sediment-free must e x i s t . However they cannot be uniform throughout the S t r a i t , as some deep areas i n the S t r a i t have slower sedimentation rates than others at the same or shallower depths. 131 Probably the most important information permitting e l u c i d a t i o n of sedimentational mechanisms i s provided by the seismic records. The presence of r e f l e c t o r s that change from strong to weak away from the d e l t a front and t h i n i n the same d i r e c t i o n , but which appear to be contained within the sidewalls of the basin, a l l point to the p r o b a b i l i t y that t u r b i d i t y currents are an important mechanism i n d i s t r i b u t i n g sediments along Ballenas Basin. Cores taken from and along Ballenas Basin, however, do not give any evidence of the existence of t u r b i d i t y currents (graded bedding, laminations, r i p p l e - d f i f t laminae, clear basal demarkation of the flow: Kuenen, 1957). Some mottling of the cores that was probably due to the a c t i v i t y of burrowing organisms, and some poor but decipher-able photographs of the bottom taken from s t a t i o n 280 that show tracks and burrows, suggest that bioturbation may have disturbed any bedding features. Also, i f a t u r b i d i t y current was i n i t i a t e d i n fine-grained, moderately sorted sediment and deposition occurred i n an area of s i m i l a r l y fine-grained, moderately sorted sediment, there might not nece s s a r i l y be any v i s i b l e evidence f o r the existence of t u r b i d i t y flow deposits. It must also be r e a l i s e d that i f the sedimentation rate i n Ballenas Basin i s indeed 2 cm./year, then the longest core obtained (3 metres) records h i s t o r y only as far back as 1820 AD. At a rate of 0.55 cm./year (Mathews, Murray and McMillan, 1966) the recorded time would extend only as f a r as 1372 AD. Even allowing 1.5 metres compaction, the maximum time represented would s t i l l be only 900,years. T i f f i n et a l . (1971) suggest that the formation of the h i l l o c k s at the base of the d e l t a west of Sand Heads was due to a s l i d i n g of material from higher on the delta f r o n t , and they estimate t h i s to have occurred only 132 200 years ago. This s l i d i n g , should have triggered at l e a s t one t u r b i d i t y current, but no evidence of any was found. E i t h e r the expected t u r b i d i t y flow did not occur, or, assuming the estimated age given by T i f f i n et a l . (1971) i s not too low, the sedimentation irate i s indeed high enough to prevent a record being obtained with the apparatus used. In the seismic records r e s o l u t i o n i s not p a r t i c u l a r l y good i n the upper 12 to 18 metres, making i t d i f f i c u l t to determine whether or not t u r b i d i t y flow has occurred i n the time i n t e r v a l represented by t h i s thickness. The evidence for the existence of t u r b i d i t y currents i n Georgia S t r a i t i s not unequivocal, but the mechanism does provide an explanation for the apparent anomaly of the differences between ridge-top and basin sediment thicknesses. Low sedimentation rates have been suggested for the ridges, p a r t i c u l a r l y the deep ones at the northwest end of the study area (Sangster Ridge, Ballenas Island Ridge), and the shallower region between northwest McCall Ridge and the mainland. Some clay i s mixed with the sands and gravels of the ridges and i t s mineralogy i s the same as that from the Fraser River, but the fa c t that manganese nodules can grow on the deeper ridges, and coarser sediments have not yet been buried beyond the reach of the grab sampler, suggests that the amount of clay accumulating i n these areas i s r e l a t i v e l y small. Either l i t t l e hemipelagic sediment reaches the northwestern end of the study area, an u n l i k e l y s i t u a t i o n given currents with measured strengths of up to 0.75 knots to 312° at 90 metres depth (Station F l l , Tabata et a l . , 1970) i n the central S t r a i t , or bottom currents are s u f f i c i e n t l y strong to prevent s i g n i f i c a n t accumulation of mud on bank tops. The d i f f e r e n t depths at which coarse sediment s t i l l e x i s t s exposed 133 on the bottom suggests that current strengths and movements are not uniform throughout the S t r a i t . The present writer believes that currents provide the means of preventing permanent sedimentation on the ridges. The t h i c k sediment accumulations i n Ballenas and Malaspina Basins are the r e s u l t of deposition of hemipelagic muds introduced to the S t r a i t by the Fraser River. As w i l l be shown i n the following chapter, the sediments from both basins are p r a c t i c a l l y i d e n t i c a l i n composition (with due regard to g r a i n - s i z e e f f e c t s on mineralogy) to sediments on the de l t a and from the Fraser River. T e x t u r a l l y , the s u r f i c i a l . sediments from Ballenas and Malaspina Basins are i d e n t i c a l . 134 CHAPTER 4 MINERALOGY 4.1 INTRODUCTION Information on the composition of p o t e n t i a l sources f o r the S t r a i t of Georgia sediments i s scarce. A generalised account of the composition of the sand f r a c t i o n to be expected from the Cascade Mountains, the Coast Mountains and from Vancouver Island i s given by Mathews, Murray and McMillan (1966). Their findings are summarised here: Composition of sand-fractions from: ( i ) Coast Mountains - g r a n i t i c d e t r i t u s important; quartz 20% to 50%; plagioclase 15% to 40%; potash f e l s p a r 10% to 20%; amphibole (hornblende) ±5%; plus b i o t i t e , epidote, garnet, magnetite, fragments of metamorphic and volcanic rocks, b a s a l t i c hornblende and volcanic rock fragments. ( i i ) Cascade Mountains - quartz 15% to 25%; fe l s p a r 15% to 45% (plagioclase and potash fe l s p a r i n about equal proportions); chert and quar t z i t e 25% to 50%; plus c h l o r i t e , garnet, micas, sphene and s t a u r o l i t e . ( i i i ) Vancouver Islandr- high proportion, of l i t h i c grains and metavolcanic material. (iv) Fraser River sands seem most c l o s e l y r e l a t e d to the Cascade Suite; the dark colour of the sands being due to dark grains of chert. Muscovite i s conspicuous although present i n small q u a n t i t i e s , and i s supplied to the S t r a i t only by the Fraser and perhaps the Nooksack Rivers. Unfortunately, no information was provided describing the locations of the samples from which t h i s information was taken, and no mention was made whether the descriptions apply to t o t a l sand f r a c t i o n or only a portion of i t . No information i s a v a i l a b l e on the mineral composition of Pleistocene deposits e i t h e r around the margins of the S t r a i t , or those through which the Fraser River flows and from which i t 135 derives, muck of it s . load. A mineralogical study of the s i l t - and clay—sized components from a l l u v i a l sediments of trie Fraser River was undertaken by Mackintosh and Gardner (1966). They described a progressive increase i n p h y l l o s l l i c a t e mineral content with decreasing g r a i n - s i z e . S i l t f r a c t i o n s were e s s e n t i a l l y s i m i l a r to f i n e and very f i n e sand-size material, consisting of a preponderance of quartz, f e l s p a r and c h l o r i t e , with l e s s e r amounts of amphiboles and pyroxenes. The cl a y f r a c t i o n s contained montmorillonoid and c h l o r i t e minerals plus l e s s e r amounts of micas, mixed-layer mont-morillonoid - c h l o r i t e , quartz and f e l s p a r . In the present study, mineralogical analysis, of the sub-sand-s i z e f r a c t i o n s has been stressed. Less emphasis has been placed on the gravel and sand f r a c t i o n s because of the r e l a t i v e l y smaller amounts and r e s t r i c t e d d i s t r i b u t i o n s of the coarser sediments. Bands or patches of sediments with d i s t i n c t i v e , unique mineralogic compositions or associations have been used s u c c e s s f u l l y i n some areas f o r determining sediment d i s p e r s a l patterns (e.g. Van Andel, 1964; Imbrie and Van Andel, 1964; Ross, 1970). The a p p l i c a t i o n and success of t h i s technique r e l i e s on the presence of more than one source of sediment supply, the separate sources being located i n areas of d i f f e r e n t bedrock l i t h o l o g i e s . Such a s i t u a t i o n does not e x i s t i n the S t r a i t of Georgia. E a s i l y eroded l o c a l sources around the margins of the S t r a i t are g l a c i a l l y derived Pleistocene deposits. The Fraser River, which supplies most of the sediment to the S t r a i t also derives much of i t s load from Pleistocene deposits. The r e s u l t i s a generally uniform composition f o r the sediments throughout the S t r a i t . Consequently sediment composition i s of l i t t l e help i n e l u c i d a t i n g d i s p e r s a l patterns i n t h i s area, but instead points to the dominance of one heterogeneous 136 source for S t r a i t ot Georgia .sediments. This source, i s p r i m a r i l y Pleistocene deposits either by l o c a l erosion or v i a the Fraser River. Around the margins of the S t r a i t , l o c a l sources other than Pleistocene deposits may be apparent; v o l u m e t r i c a l l y they are of l i t t l e importance. A l l samples containing gravels and very coarse sands were examined, and hand-specimen i d e n t i f i c a t i o n s of coarse constituents were v e r i f i e d by t h i n section study of selected pebble l i t h o l o g i e s . Sand f r a c t i o n s of g r a v e l l y and non-gravelly samples .were examined, q u a l i t a t i v e l y with a binocular microscope. F i f t e e n samples chosen from various parts of the S t r a i t were size-separated into eight f r a c t i o n s by wet-sieving through 10, 18, 35, 45, 60, 120, 230 sand 325 mesh sieves, and the material caught on each sieve was examined separately. Thin-sections of grain-mounts and stained grain-mounts were made from the 60 to 120 mesh (fine sand) f r a c t i o n s of these samples. Staining to d i s t i n g u i s h potash and p l a g i o c l a s e f e l s p a r s and quartz was performed on l i g h t f r a c t i o n s separated from the t o t a l 60-120 mesh f r a c t i o n by centrif u g i n g i n bromoform. The l i g h t minerals were mounted on glass s l i d e s using DOMTAR Lap Cement as the mounting-medium ( c f . Gross and Mo ran, 1970). Felspars were stained with sodium c o b a l t i n i t r a t e s o l u t i o n (Chayes, 1952) following an eight-minute etch i n hy d r o f l u o r i c acid vapour (time schedule and procedure according to Gross and Moran, 1970). Point-counts were made of quartz, plagioclase and potash fe l s p a r using a binocular microscope. Results are presented i n Table V as the r a t i o of quartz-plagioclase-potash f e l s p a r . Nine samples from the S t r a i t of Georgia and three from the Fraser River at Ruby Creek, 12 miles east of Agassiz, B.C., ref e r r e d to as the Group A samples, were subjected to d e t a i l e d p h y s i c a l and chemical treatment and analysis f o r sub-sand-size mineralogy, cation exchange 137 capacities., content of exchangeable bases and p o s s i b l e diagenetic e f f e c t s . The e s s e n t i a l l y uniform composition of the sediments through-out the S t r a i t of Georgia was established w i t h these samples. M i n e r a l -o g i c a l analysis by X—ray d i f f r a c t i o n was conducted on 53 to 20, 20 to 5, 5 to 2, 2 to 0.2 and finer-than-0.2 micron s i z e f r a c t i o n s of the Group A samples. Another f i f t y - s e v e n samples, Group B, were separated into coarse to medium s i l t , , and cl a y (less than 2.0 microns) s i z e - f r a c t i o n s and subjected to X-ray d i f f r a c t i o n analysis without any treatment other than washing to remove soluble sea s a l t s . These samples were used for semi-quantitative clay-mineral analysis a f t e r the method of Johns, Grim and Bradley (1954). They confirmed the uniformity of the sub-sand-size mineralogy found from the Group A samples. One of the more important features of the mineralogy i s the d i s t r i b u t i o n of sand-size flakes of muscovite, Mathews and Shepard (1962) and Mathews, Murray and McMillan (1966) contend that muscovite i s contributed to the S t r a i t of Georgia only by the Fraser and perhaps by the Nooksack Rivers. Examination of the sand-size f r a c t i o n s from various S t r a i t of Georgia sediments, paying p a r t i c u l a r attention to the presence or absence of obvious even i f q u a n t i t a t i v e l y unimportant muscovite, revealed t h i s contention to be erroneous. With the exception of some samples from close to shore on the western side of the S t r a i t at the northwestern end of the study area, which d i d not appear to contain muscovite (e.g. 286, 337, 341), t h i s mineral has been found i n the sand f r a c t i o n s of almost a l l other samples studied, p a r t i c u l a r l y those from ridge crests (e.g. 354, 263), on the western side of the S t r a i t , and from the region opposite and south of the d e l t a . Sample 351 f o r example contains a considerable quantity of muscovite and other micaceous 138 minerals s i m i l a r to those of the Fraser River. This sample s i t e i s at the extreme northwestern end of the study area on the eastern side of the S t r a i t . Muscovite i s present, but not abundant, i n samples located between s i t e 351 and the Fraser Delta suggesting that suspended-load transport of sand-sized muscovite from the Fraser River along the eastern margin of the S t r a i t of Georgia cannot be occurring. Bottom topography between the d e l t a and sample l o c a l i t y 351 i s very i r r e g u l a r , and i s cut by the axis of Queen Charlotte Trench, which suggests that bottom transport of muscovite from the d e l t a area i s u n l i k e l y . Since muscovite i s present, sometimes i n moderate qu a n t i t i e s , i n sediments on ridge crests within the S t r a i t , both as d i s c r e t e grains and as a constituent offgrani'tox rock fragments, Pleistocene deposits as well as the Fraser River are l i k e l y to provide a source for muscovite. 4.2 GRAVELS Gravel i s used here as a general term for a l l material coarser than 2mm. e f f e c t i v e sieve diameter. Most gravels are associated with sand and mud, except i n the t i d a l channels and passes, and were separated from the remainder of the sediment by wet-sieving, Individual gravel components - pebbles and cobbles - range from angular to rounded although the majority are subangular to subrounded. Their surface textures may be smooth or quite i r r e g u l a r and p i t t e d . They may possess f l a t t e n e d but r a r e l y s t r i a t e d faces, and numerous broken pebbles with rounded edges were found. Pebbles and cobbles c o l l e c t e d from Boundary Basin and the southern parts of the Island slope, and l e s s commonly those from ridge c r e s t s , may support a varied fauna of encrusting organisms, including long, convolute, sandy worm tubes , barnacles, c o r a l s , sponges and o c c a s i o n a l l y pelecypods such as Mytilus. Ferromanganese stains are 139 common, and accretionary manganese nodules around pebble nuclei, were found at two l o c a l i t i e s at the northwest end of. the study area. The composition of the gravel constituents i s s i m i l a r to that i n Pleistocene deposits i n nearby land outcrops. L i t h o l o g i e s include: fresh and altered d i o r i t e s and granodiorites, the most common rock type (ranging from coarsely c r y s t a l l i n e with varying proportions of hornblende, and p l a g i o c l a s e and quartz, to f i n e l y c r y s t a l l i n e and often epidotised); amphibolites; volcanic and low-grade metamorphic rocks; sandstones and a r g i l l i t e s . Red volcanic rock fragments are not common i n t h i s s i z e f r a c t i o n but are conspicuous i n the f i n e gravel, very coarse sand and coarse sand s i z e ranges. The v a r i e t y of l i t h o l o g i e s i s not as great as that of the gravels on the Point Grey beaches, which may be a function of the sampling procedure rather than the actual conditions. Many of the pebbles and cobbles have a more weathered appearance than the beach material with i r o n or i r o n and manganese s t a i n s , p i t t e d or rough surfaces, and a s u p e r f i c i a l greenish d i s c o l o u r a t i o n e s p e c i a l l y evident on some granodiorites and d i o r i t e s that i s not common on beach boulders. The d i f f e r e n c e can be a t t r i b u t e d to subaqueous weathering. Or i g i n of the gravels as either r e l i c t Pleistocene or l a g -concentrate has been considered e a r l i e r . The Fraser River i s not trans-porting gravels as bed-load to near Sand Heads at present, even during the freshet. Their d i s t r i b u t i o n i n the S t r a i t i s such that, except perhaps for l o c a l marginal accumulation, g l a c i e r s , f l u v i o - g l a c i a l streams or f l o a t i n g i c e afford the most l i k e l y explanations as means of transport. The composition i s heterogeneous and r e f l e c t s the geology of the surrounding areas (see Figure 3). 140 4.3 SANDS Quartz and fe l s p a r dominate and, with, l i t h i c . fragments and green and brown hornblende, provide the bulk of the sand-size mineralogy. Micas, including muscovite, b i o t i t e and c h l o r i t e , and pink garnet are conspicuous i f not always q u a n t i t a t i v e l y important constituents of the sand mineralogy of almost a l l samples. Magnetite i s present i n most samples although never i n abundance. Epidote and rare grains of sphene and s p i n e l are also p e r s i s t e n t trace components. In an excellent discussion introducing the re s u l t s of mineral-ogic studies of Recent sediments from Barkley Sound, Carter (1970) pointed out that meaningful comparisons of sand-size mineralogy can only be obtained from study of total'sand mineralogy among samples with s i m i l a r s i z e ranges and, presumably, means and standard deviations. He also suggested that mineraloglc studies of s i n g l e s i z e - f r a c t i o n s can be misleading because of the dependency of mineral composition on grain s i z e . Carter's research produced r e l i a b l e evidence i n support of h i s contentions. The idea of s i z e control of mineralogy has also been discussed by Davies (1972). Examination of eight s i z e - f r a c t i o n s separated from several S t r a i t of Georgia samples, one sample from the Fraser River and one from Pleistocene sediments near the base of the c l i f f s at Point Grey, indicated that s i z e control of mineral composition i s an important factor i n f l u e n c i n g these sediments also. Coarser s i z e f r a c t i o n s contain quartz, f e l s p a r and hornblende as dominant i n d i v i d u a l mineral species but the bulk of the samples consist of a v a r i e t y of l i t h i c fragments. Granodiorites, quartz d i o r i t e s and d i o r i t e s are the dominant l i t h i c constituents i n the coarser s i z e s , but t h e i r coarse c r y s t a l l i n i t y r e s u l t s i n t h e i r loss by reduction to i n d i v i d u a l minerals i n f i n e r s i z e grades. Red.grains of volcanic rock are conspicuous and are apparent i n most sandy sediments from the east and ce n t r a l parts of the S t r a i t . They seem to be rarer or even absent from sandy sediments on the Vancouver Island side. Dark, fine-grained l i t h i c fragments are apparent i n a l l sands, but decrease i n prominence i n f i n e r s i z e s as a r e s u l t of both t h e i r breakdown and the r e l a t i v e increase i n quantities of quartz, fe l s p a r and hornblende. Fragments of metamorphic rocks are more conspic-uous from samples close to the western margin, but are present over the e n t i r e S t r a i t . Finer s i z e f r a c t i o n s are dominated by quartz and f e l s p a r , with subordinate but prominent amounts of red and green hornblende and dark, fine-grained l i t h i c fragments. Garnet, micas and other minerals may be conspicuous but are of much l e s s importance volumetrically. Minor differences i n the mineralogy can be detected, mainly i n samples from the western side of the S t r a i t at the northwestern end of the study area and close to shore. Further from shore ei t h e r the differences no longer e x i s t or the sediments are c h i e f l y muds. The p r i n c i p a l departures from the usual composition include l e s s e r quantities of mica, e s p e c i a l l y muscovite (none at a l l i n 337, 341, 342), or l e s s v a r i e t y of mineralogy (286). Sample 315, close to sample 286, does have a sand composition s i m i l a r to most others, however, which may be interpreted as further support for the contention that the mineral composition, and muscovite, may be derived from Pleistocene deposits as w e l l as from the Fraser River, while sources marginal to the S t r a i t are l o c a l and of minor importance. This suggestion i s consistent with the compositions of samples such as 263 and 354 from ridge tops within the S t r a i t , 21. from Alden Bank, 58 from Roberts Swell, 142 SAMPLE Q : P : K Q:F 2H 8 3 .08 3.62 1 .0 .68 16 21 3.42 3.67 1.0 .74 10 40 4.09 4.00 1 .0 .81 1 1 58 2.73 2.93 1 .0 .70 2 82 3.14 3.07 1 .0 .77 IC 9 3 2. 16 1. 89 I .0 .74 8 10 3 5.71 7.57 1.0 .67 7 172 1 .57 2. 14 1 .0 .50 9 238 9.00 9.80 1 .0 .83 8 242 2.53 3. 13 1.0 .61 9 286 3.43 2.71 1.0 .92 5 351 3.54 3. 15 1.0 .85 3 354 3.21 2.93 1.0 .83 5 QUADRA 4.63 6.88 1.0 .58 13 FR3U 2. 53 2.41 1.0 .74 5 AV. 3.65 3.99 1.0 .73 * 1 3 .00 * 3 6.29 * 4 1.65 * 8 NO INFORMA TION 4.00 * 9 GIVEN 2 .43 * . l l 8.00 *1 2 6.14 *AV . 3.64 TABLE V: RATICS OF QUART Z ( Q) : PLAGTOCLASF(P) : POTASH F E L S P A R ( K ) f AND CUARTZ(G) -.FELSPAR ( F ) FOR 60 TO 120 MESH LIGHT FRACTIONS OF SELECTED GEORGIA STRAIT SAMPLES.*.H IS THE PERCENTAGE OF HEAVY MINERALS IN THIS FRACTION. * REFERS TO INFORMATION FROM TABLE It P.36 T GARRISON ET AL (1969): DISCREPANCY BETWEEN THESE AND THE GEORGIA STRAIT VALUES IS DUE TO THE INCLUSION OF QUARTZITE AMD CHERT GRAINS WITH QUARTZ IN THE FORMER'S ANALYSES. 143 103 and 106 from the d e l t a f r o n t , and FR3U from the Fraser River, which, are a l l very s i m i l a r , d i f f e r i n g o n l y i n proportions of components. That any differences In the mineralogy of sands i n the S t r a i t are of minor importance i s suggested by determination of quartz:felspar; and 'quartz:plagioclase:potash f e l s p a r r a t i o s f o r the l i g h t mineral f r a c t i o n s of the 60 to 120 mesh s i z e ranges for several samples scattered throughout the S t r a i t . The r e s u l t s (Table V) did not i n d i c a t e any trends i n v a r i a t i o n among samples and i n f a c t the v a r i a t i o n among samples was s i m i l a r to that found by Garrison et a l . (1969) among compositions of early diagenetic concretions c o l l e c t e d from d i s t r i b u t a r y channels of the Fraser River. A propos of an e a r l i e r consideration, that of comparing mineralogy of samples within s i m i l a r s i z e ranges, the Georgia S t r a i t sediments do not lend themselves to t h i s kind of treatment. Few sandy samples are well-sorted. Only three samples are e n t i r e l y sand with l i t t l e or no mud; a l l others have s u f f i c i e n t quantities of sub-sand-size material to render them poorly sorted. A large number of the samples that do contain sand have t h i s f r a c t i o n i n the f i n e to very f i n e sand range as a coarse t a i l to a dominantly s i l t and clay s i z e d i s t r i b u t i o n . Compared to the s i l t s and clays, sands are v o l u m e t r i c a l l y of much l e s s importance. 4.4 SUB-SAND-SIZE MINERALOGY As mentioned i n the introduction, X-ray d i f f r a c t i o n analysis of the sub-sand-size mineralogy was conducted on two groups of samples that had undergone quite d i f f e r e n t chemical and physical pre-analysis treatments. The reasonsif or., t h i s c i d i v i s i o n are: i . a crude experiment designed to show what detectable diagenetic e f f e c t s might occur when the.sediments passed from a f r e s h -water to marine environment was carried" out on Group A samples. Sediments from the S t r a i t that had obviously been In the marine environ-ment some time were included to compare with the Fraser River material. A few samples were chosen to be representative, covering as wide an area as possible of the S t r a i t . These samples were subjected to det a i l e d X-ray analysis and selected chemical techniques. i i . Johns, Grim and Bradley (1954) developed a widely used, semi-quantitative technique for clay-mineral analysis. Samples to be analysed by t h i s technique should not be chemically treated i n any way, except f o r removal by washing of soluble sea s a l t s . The 57 samples from Group B were chosen f o r the purpose of semi-quantitative analysis. i i i . Two schools of thought exist concerning the preparation of c l a y - r i c h sediments (or clays) for X-ray analysis (Bradley, 1964). The f i r s t school employs chemical and phys i c a l treatments which attempt to remove organic matter and amorphous, poorly c r y s t a l l i n e or badly deteriorated phases, thus attempting.to high-grade the residue or to regrade i t to a r e l a t i v e l y constant composition (Jackson, 1956, 1964; used i n many s o i l science l a b o r a t o r i e s ) . The second group believes that theunatural assemblage:sho.uldbbe? examined^aantreated;," following the argument that ^hevprevibusbitechniqueditends. to^ create! a clay-mineral condition (of orderliness or c r y s t a l l i n i t y ) that did not exi s t i n the natural state. The second approach studies the mineralogy as i t r e a l l y i s and may, for example, lead to the i d e n t i f i c a t i o n of greater quantities of mixed—layer clays. It can also be argued, i n favour of the second a l t e r n a t i v e , t'-tHat-'- clays i n the marine environment are not usually associated w i t h as much organic matter or amorphous material as 145 are clays i n soils., and because mixed:-layer phases may be the most stable form i n the marine environment (Berry and Johns, 1966), a technique that requires no more involved pre-analysis. treatments than soluble s a l t removal may be quite s a t i s f a c t o r y f or marine clays. Some conclusions to t h i s problem can be reached having used both techniques on samples from the same, r e l a t i v e l y small area. Comparing Figures 44 to 49 with Figures 50 to 53 indicates that the two approaches give quite d i f f e r e n t r e s u l t s . X-ray peaks are better developed, sharper, and narrower at t h e i r bases i n Group A samples. For Group B samples the background i s greater, and mixed-layer clays, with a f a i r l y high percentage of expandable layer s , are more apparent. Considerable d i f f i c u l t y was encountered i n i d e n t i f y i n g and c l e a r l y separating k a o l i n i t e and c h l o r i t e . As has been well established i n l i t e r a t u r e on clay mineralogy, c h l o r i t e s have even-numbered orders of basal spacings that coincide with the standard basal spacings of k a o l i n i t e . The usual method of d i s t i n g u i s h i n g the two minerals has been to X-ray an a i r - d r i e d sample, heat the sample to 550°C to 600°C for some period of time (there i s no"general agreement on the time period required, although C a r r o l l (1970) believes one hour to be adequate), X-ray again and compare the two diffractograms. T h e o r e t i c a l l y the k a o l i n i t e structure should have collapsed while the c h l o r i t e (001) peak should have increased i n sharpness i f not i n i n t e n s i t y ; higher order c h l o r i t e peaks are thermally unstable (Grim, 1968; C a r r o l l , 1970). Grim and Johns (1954) and Johns, Grim and Bradley (1954), on the other hand, have found that t h i s method does not always give the desired r e s u l t s . A f t e r much experimentation Johns, Grim and Bradley (1954) concluded that any changes i n the 7A and 3. peaks ( c h l o r i t e (002) -146 k a o l i n i t e (001) and c h l o r i t e (004). k a o l i n i t e (002) peaks respectively) found a f t e r heating f o r 45 minutes at 450°C, then a:Lr-qnenching, can be a t t r i b u t e d to c h l o r i t e i f the two minerals are suspected to be present, and i f the degree of c r y s t a l l i n i t y of the c h l o r i t e i s not p a r t i c u l a r l y good. Johns and Grim (1958) were unable to i d e n t i f y with c e r t a i n t y small amounts of k a o l i n i t e i n the presence of c h l o r i t e by heat treatment. The technique of heat treatment to d i s t i n g u i s h between k a o l i n i t e and c h l o r i t e i s not a s a t i s f a c t o r i l y unambiguous technique. Use of t h i s method led to the somewhat anomalous s i t u a t i o n of having sediments derived from the Coast Mountains and i n t e r i o r of B r i t i s h Columbia, from rocks that are r i c h i n c h l o r i t e , apparently having abundant k a o l i n i t e but only minor amounts of c h l o r i t e . To i d e n t i f y k a o l i n i t e i n the presence of c h l o r i t e Andrew et a l . (1960) presented a method based on the formation of i n t e r s a l t a t i o n complexes. B a s i c a l l y t h i s technique depends on the formation of a 14A" kaolinite-potassium acetate complex followed by replacement of the acetate ion by a n i t r a t e ion from ammonium n i t r a t e . This r e s u l t s i n a kaolinite-potassium n i t r a t e complex with a f i r s t - o r d e r basal spacing of 11.6&, which does not coincide with any other spacing of common clay minerals. The method i s laborious, requiring c l o s e l y c o n t r o l l e d humidity conditions and, as pointed out by Biscaye (1965, p.1284), dry-grinding with potassium acetate can be detrimental to the c r y s t a l l i n i t y of Recent clays. This method was attempted on some Georgia S t r a i t samples (e.g. Figure 49) with inconclusive r e s u l t s . Brindley (1961) and V i v a l d i and Gallego (1961a) suggested heating i n acid solutions clay-mineral mixtures i n which c h l o r i t e and 147 k a o l i n i t e were believed to occur. Brindley proposed hydrochloric acid ; V i v a l d i and Gallego refluxed a sample for 30 minutes i n 20% sulphuric acid. The s o l u b i l i t y of c h l o r i t e s i n acids has been summarised by Grim (1968, p.435-439). Some l i m i t a t i o n s to t h i s method were pointed out by Brindley (1961) who suggests that the c h l o r i t e composition, p a r t i c l e s i z e , acid concentration, time and temperature may a l l be important i n acid s o l u b i l i t y . V i v a l d i and Gallego (1961a) in d i c a t e that some c h l o r i t e s are ac i d - i n s o l u b l e , andi s'ome k a o l i n i t e s s p e c i f i c a l l y those members of the k a o l i n group containing i r o n , may be dissolved under acid conditions. Simmering the (Group B) S t r a i t of Georgia samples at about 95°C f o r two hours i n IN HCl seemed to o f f e r some so l u t i o n to the problem of dist i n g u i s h i n g k a o l i n i t e i n the presence of c h l o r i t e . The c h l o r i t e 14A* peak was greatly diminished and the 4.7& peak l o s t e n t i r e l y . The 7& peak ( c h l o r i t e (002)/kaolinite (001)), while always remaining, was very much reduced from i t s former i n t e n s i t y , e s p e c i a l l y when compared to the i l l i t e (mica) peak. The 3. 53# peak ( c h l o r i t e (004)) was generally l o s t and a small peak remained at 3.58A" ( k a o l i n i t e (002)). While not absolute i n i t s a b i l i t y to q u a n t i t a t i v e l y separate the two minerals, the warm HCl treatment i s adequate enough to permit t h e i r q u a l i t a t i v e i d e n t i f i c a t i o n . This method indicated the more l o g i c a l s i t u a t i o n f o r the S t r a i t of Georgia samples: that most of the 7£ peak was c h l b r i t i c i n o r i g i n rather, than k a o l i n i t i c . At the same time i t e f f e c t i v e l y precluded the semiquantitative analysis of samples treated and analysed i n t h i s way. Duplicating o r i e n t a t i o n s , thicknesses, segregation, and c r y s t a l l i t e s i z e d i s t r i b u t i o n becomes a very r e a l problem when making s l i d e s f o r X-ray d i f f r a c t i o n studies, and t h i s problem 148 is enhanced after chemical treatments. Because of these d i f f i c u l t i e s , measurement of peak areas on samples X-rayed after different treatments, even relating them to the same internal standard, often is not satis-factory . Simple slow-scanning of the regions of the (001) kaolinite - (002) chlorite (7>A) and (002) kaolinite - (004) chlorite (3.5A*) peaks was advocated by Biscaye (1964) as a definitive method of identifying kaolinite in the presence of chlorite. At slow scan-speeds of l°20/min. or less the differences between the locations of these peaks should be resolved: the kaolinite (001) occurs at 7.16& (12.3°20) for Cu Ka radiation, while the chlorite (002) occurs at 7.08>A (12.5°20); kaolinite (002) i s situated at 3.58>A (24.87°20) and chlorite (004) at 3.54A* (25.1°20). At the faster scan speed of 2°20/min. these couplets are usually unresolved. An indication of the presence of small quantities of kaolinite in some Group A samples is seen as an inflection on the lower angle side of the 77A (12.5°20) and 3.5A* (25°20) chlorite peaks (Figures 44 to 49). For convenience and relative efficiency when dealing with large numbers of samples the techniques of either warm IN HCl treatment or slowly scanning the region of the and 3. peaks offer a reasonable way of determining the presence or absence of kaolinite in the presence of chlorite. The latter technique can be used for semiquantitative studies (Biscaye, 1964, 1965). Vivaldi and Gallego (1961b) maintain that the acid treatment is also useful for distinguishing swelling chlorite from montmorillonite. Naidu et a l . (1971) chose to use a l l 3 techniques: heat treatment at 600°C for 1 hour; treatment in 2N HCl for 1 hour at 80°C; and slow scan-speed over c r i t i c a l regions. 149 4.4.1 ANALYTICAL METHODS Differences i n the X-ray diffractogram. traces between Group A and Group B samples (compare Figures 44 to 49 with. Figures 50 to 53) can be d i r e c t l y correlated with the pre-analysis treatments the two groups of samples underwent. Group A samples were subjected to a sequence of chemical treatments designed to upgrade the constituents to a common l e v e l of c r y s t a l l i n i t y , and to remove amorphous or poorly c r y s t a l l i n e phases that tend to produce large background values.. The technique i s s l i g h t l y modified from that of K i t t r l c k and Hope (1963). Samples were kept wet a f t e r c o l l e c t i o n by being placed i n p l a s t i c bags within closed containers. The following technique was used: 1. Place approximately 20 grams dry weight equivalent of sample i n a 250 ml. centrifuge b o t t l e . 2. Add about 100 to 150 ml. d i s t i l l e d water, then shake,, using a w r i s t -action or tray shaker, 2 hours, then centrifuge; decant and discard supernatant. 3. Repeat step 2 unless or u n t i l the supernatant does not give a p o s i t i v e t e s t f o r chloride on addition of a drop of s i l v e r n i t r a t e s o l u t i o n . 4. Wash the sample through a 230, 275 or 325 mesh sieve with 100 ml. sodium acetate (NaOAc) so l u t i o n (82gm. NaOAc-S^O, 27ml. g l a c i a l a c e t i c a c i d , adjust to pH 5.0, make to 1 l i t r e ) . 5. Shake 5 mins; heat at 80°C i n water bath; centrifuge and discard supernatant. 150 6. Wash with. 50 ml. NaOAc (wash. = shake, centrifuge, decant). 7. Add 20 ml. water to residue, shake 3 mins. ; add 1 ml. 30% ^O^, s t i r ; when froth i n g ceases add more ^2^2 ^ m^~' a ^ 1 u o t s > heat i n water bath at 75-80°C to f a c i l i t a t e oxidation of organic matter and to eventually c l e a r the so l u t i o n of ^2^2' 8. Add 10-15 ml. saturated NaCl, f i l l b o t t l e 2/3 f u l l of water; s t i r , centrifuge, decant. 9. Add 100 ml. c i t r a t e buffer (dissolve 188 grams sodium c i t r a t e dihydrate, 31 grams NaHCO^, arid 175 grams NaCl i n water, adjust to pH 7.3 with c i t r i c acid or NaOH and make to 2.5 l i t r e s with water); shake 5 minutes; heat to 75-80°C i n water bath; add 4 grams sodium d i t h i o n i t e slowly, s t i r slowly then vigorously; heat 15 minutes, cool , centrifuge, decant. 10. Wash with 50 ml. c i t r a t e b u f fer. 11. Add water to 10 cm. mark on b o t t l e ; shake 5 minutes; centrifuge at a convenient speed and time f o r the 0.2 micron p a r t i c l e s to s e t t l e 9 cm. Jackson (1956) gives tables and nomographs of centrifuge speeds and times. 12. Decant, and repeat step 11 on the residue. Supernatant holds p a r t i c l e s l e s s than 0.2 micron i n diameter. 13. Add water to 10 cm. mark on b o t t l e ; shake 5 minutes; centrifuge at a convenient speed and time f o r the 2.0 micron p a r t i c l e s to s e t t l e 9 cm. Decant the 2-0.2 micron f r a c t i o n . Repeat. 14. Repeat step 13, with adjustment to centrifuge speed and time, 151 to separate the 5—2 micron f r a c t i o n s . 15. Obtain the 53—20 and 20—5 f r a c t i o n s by sedimentation. The c i t r a t e - b i c a r b o n a t e - d i t h i o n i t e treatment removes i r o n oxides i n p a r t i c u l a r , and other amorphous and c r y s t a l l i n e oxides and hydroxides (McKeague et a l . , 1971). I t can also separate an i n t e r -gradient and 14& mineral i n t o i t s 10& and 14X phases (Jackson, 1964). For four of the Group A samples t h i s procedure was s l i g h t l y modified by separating the clay f r a c t i o n into 2 to 0'i.2 micron, 0.2 to 0.08 micron and finer-than-0.08 micron s i z e f r a c t i o n s using a Sharpies continuous-flow super-centrifuge. Samples were mounted for X—ray d i f f r a c t i o n analysis by the "dropper-on-glass-slide" technique which, while apparently r e s u l t i n g i n some segregation errors (Gibbs, 1965), produces excellent p r e f e r e n t i a l l y oriented samples. P r e f e r e n t i a l o r i e n t a t i o n r e s u l t s i n accentuated basal (for p h y l l o s i l i c a t e s ) r e f l e c t i o n s and increases the s e n s i t i v i t y , permitting detection of small amounts of even poorly c r y s t a l l i n e material. To f a c i l i t a t e g l y c o l a t i o n , enhance basal spacings, and to provide a means of d i s t i n g u i s h i n g e s p e c i a l l y the 14X minerals, f i n e r -than-2 micron s i z e f r a c t i o n s of Group.A samples were homoionically saturated with magnesium and potassium.. Homoionic saturation ensures that hydration w i l l be more or l e s s uniform within a l l c r y s t a l s of a species, since d i f f e r e n t cations r e t a i n d i f f e r e n t amounts of water of hydration. Magnesium permits (as does calcium) r e l a t i v e l y uniform i n t e r l a y e r adsorption of water by expandable-layer clays. Potassium 152 s p e c i f i c a l l y r e s t r i c t s i n t e r l a y e r adsorption of water by ve r m i c u l i t e while leaving c h l o r i t e phases expanded. The magnesium saturation procedure involves a c i d i f y i n g a sample aliquot with two to three drops of 0.1N HCl to prevent p r e c i p i -t a t i o n of Mg(0H)2 and consequent p o s s i b l e formation of 14! c h l o r i t e -l l k e minerals from montmorillonites (Jackson, 1956). 10 to 20 ml. IN MgCOAc^ (magnesium acetate) i s added to the suspension, which i s mixed thoroughly i n a vortex mixer, shaken for three minutes, centrifuged and the supernatant poured o f f . The Mg(0Ac)2 wash procedure i s repeated a t o t a l of three times. Two washings (10 to 20 ml. s o l u t i o n added, mixed thoroughly, shaken, centrifuged and decanted) with IN MgC^ follows, then two washings with d i s t i l l e d water and two with either ethanol or methanol. A f t e r the l a s t washing about 2 ml. of water i s added and a s l u r r y i s made from which s l i d e s for X-raying can be prepared. The potassium-saturation procedure i s b a s i c a l l y the same as that f o r magnesium, except that no a c i d i f i c a t i o n i s necessary, and only IN KC1 i s required. Samples are washed three times with IN KC1, and excess s a l t i s removed by washing twice with d i s t i l l e d water and twice with alcohol. G lycerol s o l v a t i o n , or g l y c o l a t i o n , of magnesium-saturated samples r e s u l t s i n the expansion of montmorillonite group clays to 18&: magnesium-saturation f a c i l i t a t e s t h i s expansion. Either ethylene g l y c o l or a 10% g l y c e r o l s o l u t i o n may be used. The technique employed i s b a s i c a l l y that of Jackson (1956). A few mis of 10% g l y c e r o l i s added to the residue l e f t a f t e r the l a s t alcohol wash. A s l u r r y i s prepared and s u f f i c i e n t material transferred to a s l i d e by eye-dropper to make an oriented sample. Samples are not permitted to dry out completely or the expanded phase may collapse (Hoffman and Brindley, 1961), and i f necessary they can be stored i n a dessicator i n a gl y c e r o l atmosphere. Potassium-saturated s l i d e s were X-rayed a f t e r a i r - d r y i n g , and heating to 300°C and 550°C for one and a hal f to two hours. Magnesium-saturated s l i d e s were X-rayed a f t e r a i r - d r y i n g and a f t e r g l y c o l a t i o n . A l l Group A samples were X-rayed i n a P h i l i p s X-ray unit u t i l i s i n g n i c k e l f i l t e r e d , copper Ka r a d i a t i o n generated at 40 Kv and 20mA and passed through 1°, 0.1", and 1° s l i t s . Scan speed was 1° 20/minute; time constant 3 seconds; counts f u l l scale 300. Chart speed, regulated to s u i t the scan speed and type of chart paper used, was 31.54"/hour. Pre-analysis treatment of Group B samples was considerably le s s sophisticated. It involved washing three times with d i s t i l l e d water to remove soluble s e a - s a l t s , sieving through a 230 mesh sieve to separate sand from the s i l t s and cla y s , and s i z e f r a c t i o n a t i o n by s e t t l i n g to separate the s i l t s from the clays at 2.0 microns. To d i s t i n g u i s h the expandable-layer clay component (montmorillonite), g l y c o l a t i o n was performed on the same s l i d e that had been X-rayed a f t e r a i r - d r y i n g . G l y c o l a t i o n was achieved by heating a dessicator containing the s l i d e s plus ethylene g l y c o l i n an oven f o r 1^ hours at 60°C (Brunton, 1955), then keeping the s l i d e s i n the g l y c o l atmosphere u n t i l they were X-rayed, usually the next day. While t h i s technique i s d i r e c t l y opposed to that of Jackson (1956), and even though magnesium saturation was not attempted, i t was successful i n so far as a peak at about 18A\ c l e a r l y separated from the 14$ peak, was evident (see Figures 50 to 53). The reason for t h i s success with-marine clays as opposed to s o i l clays may be rela t e d to the findings of C a r r o l l and Starkey (1960) that magnesium ions from sea-water move in t o exchange posi t i o n s on clays i n preference to sodium or calcium ions. Hence marine clays are probably s u f f i c i e n t l y n a t u r a l l y magnesium-saturated that g l y c o l expansion i s f a c i l i t a t e d . A discussion on the problems of d i s t i n g u i s h i n g k a o l i n i t e i n the presence of c h l o r i t e has been presented elsewhere i n t h i s chapter. Only the technique of warming the sample with IN HCl f o r two hours was used with the Group B samples. While the method may not be amenable to quantitative i n t e r p r e t a t i o n s , i t did show that c h l o r i t e i s present i n greater quantities than k a o l i n i t e , and confirmed the conclusions reached a f t e r studying the Group A samples. X7ray diffractograms were obtained from powder mounts of the coarse s i l t f r a c t i o n from Group B samples. Group A samples were separated into 53-20, 20-5, and 5^2 micron fractions.. X-ray diffractograms were made of each of these f r a c t i o n s on oriented specimens mounted on s l i d e s (Figures 40, 41 and 42) and, for the 53-20 micron f r a c t i o n , on powder mounts also. 4.4.2 MINERAL IDENTIFICATION CRITERIA The same c r i t e r i a f o r i d e n t i f i c a t i o n of minerals was used for both Group A and Group B samples. The terms employed r e f e r to clay mineral groups i d e n t i f i a b l e by X-ray d i f f r a c t i o n and not to i n d i v i d u a l species. I d e n t i f i c a t i o n of i n d i v i d u a l species requires somewhat simpler mixtures, d e t a i l e d chemical analysis and, usually, X-ray powder photo-graphs (e.g. Brindley and G i l l e r y , 1956; Warshaw and Roy, 1961), and i s beyond the scope of t h i s study. The clay-mineral groups are i d e n t i f i e d by t h e i r c h a r a c t e r i s t i c X-ray d i f f r a c t i o n maximum rela t e d to t h e i r s p e c i f i c basal spacings. Clay-155 minerals with, s i m i l a r basal spacings. can be distinguished, by t h e i r unique reactions to d i f f e r e n t p h y s i c a l or chemical treatments. The following c r i t e r i a were used i n t h i s study: I l l i t e : A basal (001) r e f l e c t i n g s e r i e s of loX (8.9°'20)-,-5& (17.8° 20) and 3.3/2 (26.8° 20) that i s not affected by g l y c o l a t i o n i s a t t r i b u t e d to i l l i t e . The term i l l i t e i s used as o r i g i n a l l y defined by Grim, Bray and Bradley (1937, p.816) as "...a general term f o r the clay mineral constituent of argillaceous sediments belonging to the mica group...'." Peaks at 10A*, 5/2 and 3.3/2 are generally sharp, narrow and very w e l l defined i n both the 2 to 0.2 micron Group A samples and i n the Group B clays. In f a c t , the mineral responsible i s more than l i k e l y a w e l l - c r y s t a l l i s e d , f i n e l y ground mica. Much micaceous material - musco-v i t e , b i o t i t e and leached v a r i e t i e s of both - i s evident i n the sand f r a c t i o n s of the Georgia S t r a i t and Fraser River sediments. "Mica" and " i l l i t e " are therefore synonymous and have been used a r b i t r a r i l y fo r the same r e f l e c t i o n s i n the s i l t - and c l a y - s i z e d f r a c t i o n s r e s p e c t i v e l y . K a o l i n i t e and c h l o r i t e : The problem of the i d e n t i f i c a t i o n of k a o l i n i t e i n the presence of c h l o r i t e has been discussed elsewhere. For Group A samples slow scanning speeds revealed small amounts of k a o l i n i t e by shoulders on the low angle sides of the 7/2 and 3. 5/2 peaks. Warm acid treatment of Group B samples s i m i l a r l y suggested a small quantity of k a o l i n i t e . Mackintosh and Gardner (1966) record only small amounts of k a o l i n i t e from a l l u v i a l sediments of the Fraser River. C h l o r i t e has. d i f f r a c t i o n maxima at 14&, 7/2, 4.7/2 and 3.5/2. Persistence, and i n t e n s i f i c a t i o n , of the 14/2 peak af t e r heat treatment to 550°C of potassium-saturated samples, despite thermal i n s t a b i l i t y of the 7&-, 4.7A* and 3. 5 ! peaks., provides a sound basis f o r the i d e n t i f i c a t i o n of c h l o r i t e (Grim, 1968; C a r r o l l , 1970). Because of the problems presented f o r quan t i t a t i v e studies by the c h l o r i t e - k a o l i n i t e separation using acid treatments, the 7! peak area was a t t r i b u t e d to both c h l o r i t e and k a o l i n i t e f o r the purposes of constructing Figure 54. A s i m i l a r procedure was employed by Knebel et a l . (1968). Montmorillonite: M a t e r i a l which expanded i t s (001) spacing from 14! to about 18! following g l y c o l s o l v a t i o n was assigned to the montmor-i l l o n i t e group. For the Group A samples t h i s expansion was usually complete, and the expanded peak quite d i s t i n c t . Glycolated c l a y - f r a c t i o n s of Group B samples did not expand as much, commonly only to 16! or 17!, and only occasionally to 17.5!. MacEwan (1961) records t h i s l e s s e r expansion with ethylene g l y c o l as being u n i v e r s a l f o r a l l montmorillonite. The low angle side of the expanded peak (Group B) was i n v a r i a b l y very i r r e g u l a r consisting of many small, sharp peaklets. Between the 14! c h l o r i t e and 17! expanded montmorillonite peaks one or more peaklets occurred either as d i s t i n c t i v e features or as bumps on the side of the expanded peak (see Figures 50 to 53). Vermiculite: The apparent absence of verm i c u l i t e from Group A and Group B samples i s i n t e r e s t i n g . The micaceous components of the sand f r a c t i o n s consist of: a colo u r l e s s , clear or translucent, fresh, angular mica that i s i d e n t i f i e d as. muscovite; a black or very dark coloured mica i d e n t i f i e d as b i o t i t e ; a s o f t , rounded, greenish micaceous mineral that i s probably c h l o r i t e ; a pale, bronze-coloured mica that 157 can o c c a s i o n a l l y be seen developing from b i o t i t e and i s consequently believed to be a leached v a r i e t y of t h i s mineral; and a gold coloured, generally very f r i a b l e , curled, e x f o l i a t i n g mica of unknown o r i g i n . This l a s t mica i s very common i n the Fraser River samples and from the sand f r a c t i o n of sample 351, but rarer i n other samples. The abundance of fresh and weathered micas, p a r t i c u l a r l y b i o t i t e , might be expected to provide l o c i for the development of ver m i c u l i t e (Barshad, 1948; K e l l e r , 1964). Magnesium-saturated v e r m i c u l i t e has an (001) d i f f r a c t i o n maximum at about coincident with the (001) d i f f r a c t i o n maxima of both c h l o r i t e and montmorillonite. Heat treatment (at 500°C) w i l l eventually collapse the ve r m i c u l i t e to 10X ( C a r r o l l , 1970; Walker, 1961) while c h l o r i t e remains at 14&. Montmorillonite undergoes a s i m i l a r l a t t i c e collapse on heating. Solvation with polar organic l i q u i d s w i l l expend the montmorillonite l a t t i c e to 188, but not vermiculite which, along with c h l o r i t e , remains at 148. Consequently, i n the presence of both c h l o r i t e and montmorillonite, p o s i t i v e i d e n t i f i c a t i o n of vermiculite becomes very d i f f i c u l t i f not impossible. I t i s quite possible that vermiculite does occur, but i t s i d e n t i f i c a t i o n i s prevented by a masking e f f e c t due to c h l o r i t e and montmorillonite. That v e r m i c u l i t e i s probably present, at le a s t i n the sand and s i l t f r a c t i o n s , was indicated by the r e s u l t s of r a p i d l y heating some of the ragged, gold-coloured micaceous minerals from sample 351 i n a Bunsen flame. Some of these micas underwent rapid , r e l a t i v e l y large, expansion i n a d i r e c t i o n normal to the cleavage (perpendicular to the c a x i s ) , a feature that i s c h a r a c t e r i s t i c of ver m i c u l i t e (Berry and Mason, 1959; p.510). Barshad (1948), i n a discussion on the rel a t i o n s h i p s 158 between v e r m i c u l i t e and b i o t i t e , showed, that sodium-saturated v e r m i c u l i t e has a basal spacing of 12.56!. As w i l l be discussed l a t e r the X-ray diffractograms of the s i l t f r a c t i o n s from Group A samples showed a peak at 12. 4 ! . Since the Group A samples were extensively treated with sodium s a l t s i t i s po s s i b l e that the 12. 4! peak represents sodium-saturated verm i c u l i t e . Although not always so obvious the 12.4! peak was also observed i n 53-20 micron f r a c t i o n powder mounts of Group A s i l t s . It i s not seen i n Group B s i l t s . As w i l l be discussed i n the section on mixed-layer phases, i t s obvious appearance i n oriented s l i d e s but not i n powder mounts suggests that t h i s peak i s due to a p h y l l o s i l i c a t e , and i t s presence i n Group A but not Group B powder mount diffractograms may be strongly i n favour of i t s i n t e r p r e t a t i o n as due to a sodium-saturated verm i c u l i t e . A discussion of other possible sources of the 12.4! peak i s given l a t e r . Mixed-layer minerals: The incomplete expansion, i n Group B samples, of the montmorillonite peak and the r e l a t i v e l y reduced s i z e of the c h l o r i t e 14! peak compared to that of Group A samples suggests that the montmorillonite forms an expandable and dominant component of a chlorite-montmorillonoid mixed-layer clay. Mackintosh and Gardner (1966) record; the presence of a mixed-layer montmorillonoid-chlorite clay mineral from Fraser River a l l u v i a l sediments, but do not i l l u s t r a t e or describe i t further. The asymmetry of the 14! peak of a i r - d r i e d , unglycolated Group B clay f r a c t i o n s suggests the p o s s i b i l i t y of a 10!-14! mixed-layer s e r i e s , but i f so the 14! component must be mostly montmorillonite and predominant. Mixed-layer phases were not i d e n t i f i e d from any Group A clay f r a c t i o n s . However, the s i l t f r a c t i o n s (Figures 40, 41 and 42) showed 159 FIGURE 39 : X-ray d i f f -ractograms of 2 - 5 micron f r a c t i o n of some Group A samples showing the behaviour of the 7.3 20 peak on g l y c o l a t i o n . A.M FR1 FRl FR2 FR2 + g l y c . FR3 + g l y c . FR3 160 a sharp peak at 12. 4 ! which, may be interpreted as either due to a sodium-saturated v e r m i c u l i t e (see above) or .'as the expression of a mixed-layer phase. That t h i s peak i s generated by a p h y l l o s i l i c a t e i s suggested by comparing Group B s i l t f r a c t i o n s and Group A 53-20 micron f r a c t i o n s X-rayed as powder mounts (the 12.4! peak was absent) with the Group A s i l t s X-rayed as oriented s l i d e s to accentuate p h y l l o s i l i c a t e r e f l e c t i o n s (where the 12.4! peak i s obvious). It i s a ::sharply~ defined peak, best developed i n the f i n e r s i l t s and becoming les s obvious i n the coarser f r a c t i o n s , and more prominent i n the Fraser River samples than i n the Georgia S t r a i t ones. Sample 102 (Group A) from close to the r i v e r mouth at Sand Heads has the best developed example of t h i s peak from the Georgia S t r a i t samples. Figure 39 shows the e f f e c t s of g l y c o l a t i o n on t h i s peak: a 14& peak i s evident i n a l l unglycolated analyses and i n some of the glycolated ones; a f t e r g l y c o l a t i o n the 12.4! peak may not move at a l l , may s h i f t to 14!, or may migrate to a s l i g h t l y higher spacing at 14.7!. The peak has been i d e n t i f i e d from Group A s i l t f r a c t i o n s only, and has no expression i n the c l a y - s i z e d material. Possible i n t e r p r e t a t i o n s are: 1. I t i s the expression of sodium-saturated ve r m i c u l i t e (and therefore evidence of the presence of vermiculite) as discussed above. 2. It i s a r e l a t i v e l y large mineral of random mixed-layer type that i s broken i n t o i t s constituent phases below a c e r t a i n s i z e l i m i t . Arguing against t h i s i s the fa c t that i t occurs i n Group A s i l t s , which have been subjected to c i t r a t e - d i t h i o n i t e treatment along with the associated clays, and t h i s process i s s u f f i c i e n t l y intense to separate intergradient or mixed-layer clays Into t h e i r d i f f e r e n t components (Jackson, 1964). 1 6 1 3 . The peak, maximum occurs, between and 1 4 A suggesting a regular 1 0 A ' - 1 4 A ' mixed-layer structure. I t s l i m i t e d expansion following gl y c o l a t i o n s suggests a^  mica-vermiculite i n t e r l a y e r mineral, i n which the ve r m i c u l i t e i s developing from, or i n , the weathered mica. The prominence of t h i s peak i n samples from the Fraser. River and the occurrence i n these samples of the golden,-highly weathered, mica flakes suggests some r e l a t i o n s h i p between the two. 4 . The sharpness of the peak and i t s at least p a r t l y expandable properties could be interpreted as due to a 1 2 . montmorillonite (sodium-saturated montmorillonite with only one water l a y e r ) . Counting against t h i s i s the poor expansion of the peak on g l y c o l a t i o n and the occurrence of t h i s peak i n coarse s i l t f r a c t i o n s whereas montmorillonite i s generally only found i n the f i n e clay sizes (Jackson, 1 9 5 6 ; 1 9 6 4 ) . 5 . Figure 6 , p . 8 4 , from Jonas and Brown ( 1 9 5 9 ) indicates that possible combinations of ( i l l i t e ) and 1 5 . 4 A * (montmorillonite) or 108 ( i l l i t e ) and 1 4 ! ( c h l o r i t e ) minerals also e x i s t to explain t h i s peak. The 1 4 ! c h l o r i t e peak did not s h i f t following g l y c o l a t i o n , and nowhere else was there any hint of the existence of a "swelling c h l o r i t e " (Grim and Johns, 1 9 5 4 ) . It i s u n l i k e l y that the mixture i s of any of these combinations. The i n t e r p r e t a t i o n favoured here i s that the 1 2 . 4 ! peak i s caused by the presence of small amounts of vermi c u l i t e . Preferred o r i e n t a t i o n accentuates the r e f l e c t i o n s from even small quantities of p h y l l o s i l i c a t e s . The i d e n t i f i c a t i o n , i s based on the l i m i t e d expansion of t h i s peak a f t e r g l y c e r o l s o l v a t i o n , and i t s presence in. sodium-saturated samples only. 162 Varying q u a n t i t i e s of non-clay minerals were present i n a l l samples. In the finer-than— 2 microns s i z e - f r a c t i o n quartz and f e l s p a r are common; amphibole i s generally r a r e r . In the s i l t s amphibole i s more conspicuous, and i s p a r t i c u l a r l y evident on diffractograms of powder mounts. Quartz and f e l s p a r also increase i n abundance i n the s i l t f r a c t i o n s , at the expense of the clay minerals. (-Quartz: Peaks at 4. 26X and 3 . 337A (the l a t t e r coincident with the (003) r e f l e c t i o n from mica) i d e n t i f y quartz. In an oriented sample with accentuated r e f l e c t i o n s from layer s i l i c a t e s the 4 .268 peak becomes diagnostic for the presence of quartz. Felspar: Stained grain-mounts of the sand-sized f r a c t i o n s i n d i c a t e the presence of both potash.and p l a g i o c l a s e f e l s p a r ; the former i n only small amounts. Felspar peaks were i d e n t i f i e d i n the X-ray diffractograms, but no attempt was made to separate the two types by X-ray methods. Amphibole: A peak with a maximum at 8. 4 8 - 8 . 5 8 was used to i d e n t i f y amphibole (Jackson, 1956, 1964). 4-.4.3 DISCUSSION OF SUB-SAND-SIZE MINERALOGY Comparing Figures 40 to 43 with Figures 44 to 49 suggests a s i g n i f i c a n t d i f f e r e n c e between s i l t - and c l a y - f r a c t i o n mineralogy for the same samples, although among a l l samples a marked s i m i l a r i t y i n the mineral suites i s evident. N o n - p h y l l o s i l i c a t e minerals increase i n abundance r e l a t i v e to p h y l l o s i l i c a t e s . from the f i n e to the coarse s i l t f r a c t i o n s . The coarse s i l t and f i n e sand f r a c t i o n s are e s s e n t i a l l y i d e n t i c a l , consisting p r i m a r i l y of quartz, f e l s p a r and amphibole, with 163 small but conspicuous amounts of micas and garnet. Clay f r a c t i o n s contain c h l o r i t e , montmorillonite and mica as dominant minerals, with l e s s e r amounts of k a o l i n i t e , quartz, f e l s p a r and sometimes amphibole. Finer clay f r a c t i o n s show a greater amount of montmorillonite, which i s a function of the more common f i n e s i z e of t h i s mineral (Jackson, 1956, 1964). 4.4.3.1 S i l t f r a c t i o n : Figures 40, 41 and 42 are tracings of X—ray diffractograms f o r oriented samples of 53-20, 20-5 and 5-2 micron f r a c t i o n s r e s p e c t i v e l y for Group A samples. Figure 43 shows tracings of X-ray patterns from random powder mounts of Group B samples. The l a t t e r show the same mineral s u i t e occurring throughout the S t r a i t of Georgia which, apart from minor differences i n proportions of components among samples and differences r e l a t e d to the method of sample preparation f o r X-raying, i s b a s i c a l l y i d e n t i c a l to that of the Group A samples. The main differences i n the r e s u l t s suggest quartz and f e l s p a r are much more abundant i n the powder mounts than i n the preferred o r i e n t a t i o n s l i d e s . This observation i s consistent with conclusions reached following v i s u a l inspection of the f i n e and very f i n e sand grades where c h l o r i t e and mica are much less obvious. Amphibole i s present i n much less quantity than quartz or f e l s p a r , but i s usually i n excess of the micaceous minerals. The apparent anomaly i n the r e l a t i v e o r i e n t a t i o n of micaceous minerals accentuating r e f l e c t i o n s and r e s u l t i n g i n peak i n t e n s i t i e s that are out of proportion to the minerals' true abundance. Group A s i l t f r a c t i o n s show a higher l a y e r - s i l i c a t e content f o r Fraser River samples than f o r those from Georgia S t r a i t . Amphibole 164 FIGURE 40 : X-ray d i f f r a c t o g r a m t r a c i n g s f o r the 20 - 53 micron s i z e f r a c t i o n o f Group A samples. FR1U FR2U FR3U 23 53 102 /AJA^H!^ 14 5 A J I ^ ^ ^ ^ 162 ^ 263 .JuJV_7*>Wv<v^ vVM'VRA« |^ I I l I l I I i V 350 v**' 60 50 40 20 rf V ^ l / v / t I I 10 5 3 29v 165 FIGURE. 41: X-ray diffractogram tracings for the 5 - 2 0 micron size f r a c t i o n of Group A samples. 20? 166 FIGURE 42 : X-ray diffractogram tracings for the 2 - 5 micron size f r a c t i o n of Group A samples. FR1U FR2U FR3U vV tvAv^VwNvA' 2 3 ^K^-^s^^^ 53 Hi 162 263 280 342 1 0 2 ^ K j . 3 5 0 w ^ u ^ J i A ^ ^ ^ , . ,.. , 5 . 6 . . . . . . 4 - 6 . >^0 i 6 ' • 'id • ' ' 'id - "3 168 contents however are higher i n the S t r a i t samples, e s p e c i a l l y In the coarse s i l t f r a c t i o n . The enhanced 8. peak for amphiboles i n an oriented s l i d e i s believed by Biscaye Q-965) to be a r e s u l t of preferred o r i e n t a t i o n on (110) cleavage surfaces, the 8.4/2 spacing being re l a t e d to the (110) s e r i e s . 53-20 micron f r a c t i o n (Figure 40): mica, quartz, c h l o r i t e and f e l s p a r peaks, plus a well-developed 12.4/2 peak are present i n the Fraser River samples. Georgia S t r a i t specimens display the same peaks but with better developed amphibole and a less obvious 12.4& peak. 20-5 micron f r a c t i o n (Figure 41): the same mineral s u i t e e x i s t s as above except that amphibole i s much less obvious than i n the 53-20 micron f r a c t i o n . Layer s i l i c a t e s are s t i l l more obvious i n the Fraser River than i n the Georgia S t r a i t samples. 5-2 micron f r a c t i o n (Figure 42): a greater change Ln the mineralogy than between the previous f r a c t i o n s i s apparent. The non-p h y l l o s i l i c a t e content has decreased, while the p h y l l o s i l i c a t e f r a c t i o n has become more prominent. The 12.4/2 peak i s much more pronounced ( r e l a t i v e to the 14/2 peak), e s p e c i a l l y f o r the Fraser River samples. C a l c i t e of unknown o r i g i n occurs i n some Georgia S t r a i t samples (342, where i t i s prominent; 102, 145 and 350). T h e o r e t i c a l l y the pre-analysis treatment should have removed most i f not a l l the c a l c i t e , and c a l c i t e values calculated from the amount of carbonate-carbon present i n the samples i s low (0.42-2.96% CaC0 3; see Table XI). As w i l l be described below there i s an even' greater mineralogic change i n the cl a y - s i z e d f r a c t i o n s than between the s i l t f r a c t i o n s . Somewhere within the 2 to 5 micron range there i s a change from a s u i t e of minerals dominated by blocky grains of quartz and fe l s p a r to a suit e 169 dominated by p l a t y , micaceous, (fine-grained mica and clays) minerals. Mineralogical changes" between s i z e f r a c t i o n s and differences among samples i s a function of the source mineralogy which may be accentuated by, or impose modifications or r e s t r i c t i o n s on, the mode of transport of the minerals to the depbsitional s i t e s . 4.4.3.2 Clay f r a c t i o n - Group A: Subsequent to the pre-analysis treatments described above, Group A clay f r a c t i o n s were separated into 2-0.2 micron and finer-than-0.2 micron f r a c t i o n s by ce n t r i f u g a t i o n . For f i v e of the samples the f r a c t i o n a t i o n was c a r r i e d further using a Sharpies continuous-flow super-centrifuge to separate the 0.2 to 0.08 and finer-than -0.08 micron f r a c t i o n s . Each f r a c t i o n of a l l samples was subjected to magnesium-saturation, g l y c e r o l solvation., potassium-saturation, and heating, at least 5 X-ray diffractograms being obtained f o r each sample f r a c t i o n . In some 2 to 0.2 micron f r a c t i o n s extra diffractograms were obtained following i n t e r s a l t a t i o n with ammonium s a l t s , and/or a f t e r HCl treatment, i n order to substantiate the c h l o r i t e / k a o l i n i t e d i s t i n c t i o n . Components of the coarse clay (2 to 0.2 micron f r a c t i o n ) are c h l o r i t e , montmorillonite, i l l i t e (mica), quartz and f e l s p a r . A l l samples are b a s i c a l l y extremely s i m i l a r i n development of peaks and i n mineralogy. Small differences are apparent, such as the appearance i n some but not a l l samples of the 8.4$ amphibole peak. I n t e n s i t i e s of some of the p h y l l o s i l i c a t e peaks vary from sample to sample,' but there i s no systematic change i n the r a t i o s of mica to montmor-i l l o n i t e (Table VI). 170 No. Mica :Montmorillonite (x:l) No. Mica:Montmorillonite (x:l) FR1U 1.91 162 1.09 23 0.92 263 1.79 53 0.97 280 1.97 102 1.41 342 1.36 145 1.39 350 1.50 Table VI: Ratio of mica to montmorillonite (as x : l ) on the loS and 188 peaks of magnesium-saturated, glycerol-solvated samples using the technique of Johns, Grim and Bradley (1954): peak area = peak height x peak width at 1/2 peak height; area of mica peak x4. Montmorillonite (generally dominant) and c h l o r i t e are the main minerals i n the f i n e clay f r a c t i o n (<0.2 microns), occurring i n a l l samples although more obvious i n some than i n others (e.g. 280, 342). Quartz and f e l s p a r peaks are rare or absent, and clay mineral peaks dominate but are generally broader and not as sharp as those of the coarse clay f r a c t i o n s . C a l c i t e peaks were i d e n t i f i e d from a l l samples. The peaks are a l l w e l l developed, sharp, and c l e a r , with a sequence p r a c t i c a l l y i d e n t i c a l to that of c a l c i t e . The o r i g i n of the c a l c i t e i s not known. Treatment procedure includes an acid stage which i s meant to r i d the sample of c a l c i t e and other carbonates, and calcium chloride was not added to f l o c c u l a t e the sample. The mineralogy of the 0.2 to 0.08 micron f r a c t i o n i s the same as that i n the 2 to 0.2 micron f r a c t i o n s , being mostly the clay minerals montmorillonite Cdominant), c h l o r i t e and i l l i t e , with, very minor amounts of quartz and f e l s p a r . The peaks are u s u a l l y more ragged and l e s s sharp than those of the 2.0 to 0.2 micron f r a c t i o n s ; even the 30 25 20 1 5 i i i | i ' 2QK FIGURE 44: X - r a y d i f f r a c t o g r a m t r a c i n g s o f the 2.0 - 0.2 micron f r a c t i o n o f sample FR3U (Group A ) . (1) = Mg-s a t u r a t e d , g l y c e r o l s o l v a t e d ; (2) = M g - s a t u r a t e d ; (3) = K - s a t u r a t e d ; (4) = K - s a t u r a t e d , heated 3 0 0 ° C ; (5) = K - s a t u r a t e d , heated 550 C. (5) ' ' ' ' 25 ' ' I i i i i I 20 15 20° 3 0 2 r 1 ?°. . . . V , , ,0 1 0 29 ( FIGURE 45: X-ray di£fractogram t r a c i n g s o f the 2.0 - 0.2 micron f r a c t i o n o f samples 23 and 53 (Group A). (1) = Mg-saturated, g l y c e r o l s o l v a t e d ; (2) = Mg-saturated; (3) = K-saturated; (4) = K-satured, heated 300°C; (5) = K-saturated, . heated 550°C. I i i i 172 , 5 . ? 173 2 0 u . , , , , 2,5 , , , , 2,0 , , , , 1|5 1 1 1 1 i p 1 1 1 1 5 , 3, FIGURE 46: X-ray d i f f r a c t o g r a m t r a c i n g s o f the 2.0 - 0.2 m i c r o n f r a c t i o n of samples 145 and 162 (Group A ) . 145 ( 4 ) sfr+f ( 5 ) 4vVy ( (1) = M g - s a t u r a t e d , g l y c e r o l s o l v a t e d ; (2) M g - s a t u r a t e d ; (3) = K - s a t u r a t e d ; (4) = K-sat u r a t e d , h e a t e d 3 0 0 o C ; Q ( 5 ) = K-s a t u r a t e d , h eated 550 C. (4) y*»VM (5) ^ •MA/*-. I 1 1 ' I I > I I I I I I I I I I I I I I I 30 25 20 15 10 26" FIGURE 47: X - r a y d i f f r a c t o g r a m t r a c i n g s of the 2.0 -micron f r a c t i o n of samples 280 and 342 (Group A) (1) = M g - s a t u r a t e d , g l y c e r o l s o l v a t e d ; (2) = Mg-s a t u r a t e d ; (3) = K - s a t u r a t e d ; (4) = K - s a t u r a t e d , heated 3 0 0 ° C ; (5) = K - s a t u r a t e d , heated 5 5 0 ° C . 175 FIGURE 48 : X-ray d i f f r a c t o g r a m t r a c i n g s o f the 2.0 - 0.2 m i c r o n f r a c t i o n s o f samples 350 and 102 (Group A ) . ( l ) = M g - s a t . , g l y c e r o l s o l v a t e d ; (2) =Mg-sat. ;. (3)=K-^ s a t . ; (4) K - s a t . , h e a t e d 300°C; (5) K- .. s a t . , h e ated 550°C. (4) FIGURE 49 : X - r a y d i f f r a c t o g r a m t r a c i n g s of 2 .0 -0 .2 micron f r a c t i o n ' o f sample 263 [Group A ) : (1) Ca f l o c c u l a t e d ; (2) washed, a f t e r NH.NO :oo 3? (4). KC.H g l y c e r o l s o l -s a t , ; (8) KJ s a t . , heated t r e a t e d ; (11) heated 5 5 0 ° C . N H 4 N 0 3 i n t e r s a l t a t e d i n t e r s a l t a t e d ; (5) M g - s a t . ' v a t e d ; (6.)' Mg-sa t . . ; (7) heated 3 0 0 ° C ; (9). (10) K - s a t . , HCl HCl t r e a t e d , 5 5 0 ° C (io) V ^ / ^ (11) 26^ 177 i l l i t e peak, i s l e s s sharply defined than i n the coarser s i z e s . Peaks are d i s t i n c t i v e f o r the. various separate mineral groups, but there Is a hint of a I 0 8 - I 4 8 i n t e r l a y e r mineral given by the asymmetry of the 108 peak, and the grassiness of the diffractogram between the 108 and 148 peaks f o r the magnesium-saturated f r a c t i o n from sample 350. Montmorillonite was the only clay mineral detected i n the f r a c t i o n finer-than-0.08 microns, but with the exception of sample -FR-1© i t s peaks were usually very poorly defined. They were often displayed as only low bumps i n the region of 148 that showed a d i f f u s e expansion to 188 fo llowing g l y c e r o l s o l v a t i o n . C a l c i t e peaks appear i n a l l samples and are w e l l developed. However, the s o l i d material was f l o c c u l a t e d with calcium chloride p r i o r to X-raying which suggests at l e ast a possible source f o r the c a l c i t e . Group B: X-ray diffractograms of the finer-than-2.0 micron f r a c t i o n of Group B samples are not as clean and d i s t i n c t i v e as those of the Group A c l a y s . The peaks are generally not as sharp, u s u a l l y broader at t h e i r bases, and often more ragged i n appearance than those of the Group A clays. A mixed-layer clay c o n s i s t i n g of 108 and 148 expandable material i s present i n small q u a n t i t i e s . Montmorillonite, c h l o r i t e , i l l i t e , minor k a o l i n i t e , quartz and f e l s p a r are the basic mineral constituents. Amphibole, i n small amounts, i s present i n some samples (e.g. 351). The e s s e n t i a l s i m i l a r i t y i n the mineralogy among samples that had been established by the Group A material i s evident among the Group B samples also. Such a s i m i l a r i t y throughout the area of the S t r a i t among samples containing this, v a r i e t y of basic clay-mineral types i s 178 30 25 20 15 10 5 3 i i i I ' i i i i I i i i i I i i i . i I i i i i I i i i i I i I io' ' ' '25 ' ' ' ' 2 0 ' ' ' ' 1 5 ' ' ' ' l b ' ' ' ' '5 ' i 179 29° 20, , . i I f i i i i 1° . FIGURE 52: X-ray d i f f r a c t o g r a m t r a c i n g s o f the c l a y (<2.0 m i c r o n s ) f r a c t i o n from samples 257 and 268 (Group B ) . (1).= g l y c o l a t e d ; (2) = a i r - d r i e d ; (3) = HCl t r e a t e d . " 30 25 20 15 10 FIGURE 53: X-ray d i f f r a c t o g r a m t r a c i n g s o f the c l a y (<2.0 m i c r o n s ) f r a c t i o n from samples 345 and 351 (Group B ) . (1) = g l y c o l a t e d ; (2) = a i r - d r i e d ; (3) = HCl t r e a t e d . not consistent with, the experimental and p r a c t i c a l findings of Sherman (1953), Whitehouse et a l . (I960), G r i f f i n (1962), Meade U964) and Hahn and Stumm (1970). An explanation for t h i s s i t u a t i o n may be provided by the geographic and oceanographic conditions of the S t r a i t of Georgia. The close s i m i l a r i t y between the Fraser River and Georgia S t r a i t sediments i n the s i l t and clay s i z e s , as w e l l as the enormous amount of sediment, that the Fraser River supplies to i t s d e l t a and to the S t r a i t each year (700 x 10 cubic feet annually: Mathews and Shepard, 1962; also Pretious ,'rl969, 1972) suggests that the primary source of the Georgia S t r a i t f i n e - f r a c t i o n sediments i s the Fraser River. The mineralogy i s p r i m a r i l y of d e t r i t i a l terrigeneous o r i g i n r e f l e c t i n g the composition of sediment source of the Fraser River, which i s l a r g e l y the more e a s i l y eroded, semi- or un-^consolidated Pleistocene deposits upstream of the Fraser Canyon (Pretious, 1972). The area of the S t r a i t i s r e l a t i v e l y small, and i s semi-enclosed with a v i r t u a l l y closed c i r c u l a t i o n of at least the surface waters (see Chapter 1). Sediment i s introduced by the Fraser i n large quantity over the two to three month long spring and summer freshet. Compared to the Gulf of Mexico for example (e.g., Pisnak and Murray, 1960; G r i f f i n , 1962) neither the time, the distance from source, nor the area of basin i s s u f f i c i e n t to permit a clay-mineralogic segregation or f r a c t i o n a t i o n . Under laboratory conditions i t i s very d i f f i c u l t to recreate such an important environmental condition as turbulence. Regardless of f l o c c u l a t i o n tendencies — either r a t e or ultimate optimum s i z e attained of d i f f e r e n t c l a y minerals, turbulent transport w i l l profoundly influenc 183 the dLs.triButi.ori and d i s p e r s a l of clay minerals. E a r l y — f l o c c u l a t i n g c l a y minerals: w i l l be buoyed-up under conditions of turbulence, and i f t h i s turbulence i s severe enough the f l o c c u l e s may not l a s t f o r any length of time, but instead w i l l be continuously forming and disaggre-gating . 4.4.4 SEMI-QUANTITATIVE STUDIES Numerous quantitative or semi-quantitative methods, of varying degrees of s o p h i s t i c a t i o n , f or estimating clay mineral propor-tions i n sediments or s o i l s have been proposed i n the l i t e r a t u r e . Pierce and Siegel (1969) summarise and compare a few of these, and point out the inconsistent r e s u l t s that can be obtained from the same X-ray diffractograms when analysed by the d i f f e r e n t techniques. They also i n d i c a t e that while there i s confusion because of the lack of a standard method for q u a n t i f i c a t i o n of clay-mineral studies, those methods that are i n use are usually i n t e r n a l l y consistent within themselves, and each i s as well-founded as any other for quantitative studies. The method chosen here was that of Johns, Grim and Bradley (1954), which was modified s l i g h t l y by using the weighting factors advocated by Biscaye (1965) to make d i r e c t comparison of peak areas more f e a s i b l e . The weighting factors are: 1 x the area of the 17$ glycolated peak f o r montmorillonite; 4 x the 10X peak i n the glycolated sample; and 2 x the 7& peak i n the glycolated sample. Biscaye's (1965) dis c r i m i n a t i o n of c h l o r i t e from k a o l i n i t e was not made because of the poor r e s o l u t i o n of the c h l o r i t e / k a o l i n i t e couplets at 7$ and 3.5A1. The technique was applied only to Group B samples, which were chosen to cover the e n t i r e S t r a i t with a s u f f i c i e n t number of samples to produce a useful CORRECTED CONTENT PEAK AREAS AS 2X PERCENT DSH 3 N O . M. 4 X 1 . (C + K) H I C + K KM i C L A Y 19 1 0 5 3 9 4 0 6 0 0 4 1 36 23 4 2 . 5 2 0 2 5 8 2 0 8 0 0 6 2 4 37 36 28 4 0 . 6 19 4 2 5 52 8 6 4 4 8 0 29 4 6 2 5 32 .2 17 4 6 9 0 2 6 9 6 5 5 2 4 2 3 2 26 2 5 . 5 13 54 7 8 0 5 7 6 5 6 0 4 1 30 29 2 6 . 6 17 58 6 8 4 4 9 2 4 8 8 4 1 30 29 2 1 . 4 10 6 2 6 1 0 8 0 0 4 2 6 3 3 4 4 2 3 1 9 . 8 13 7 3 7 3 8 7 2 0 6 0 8 3 6 3 5 29 2 0 . 6 4 4 7 7 7 2 0 6 8 8 6 0 0 3 6 34 30 1 6 . 6 25 8 6 7 7 0 6 7 2 6 0 8 38 33 30 1 1 . 6 2 4 8 8 6 5 6 8 6 4 5 4 6 3 2 4 2 2 6 1 4 . 8 3 0 9 2 8 9 0 9 9 6 9 0 4 3 2 3 6 32 2 0 . 2 9 9 3 1 3 7 2 1 7 4 0 9 2 8 34 4 3 23 2 0 . 0 17 9.8 82 8 5 8 8 4 9 2 4 3 31 2 6 1 0 . 0 3 3 1 04 1 0 1 2 8 6 4 6 4 2 4 0 3 4 2 5 4 . 0 29 111 9 2 4 1 0 8 8 5 5 8 3 6 4 2 23 4 . 6 2 3 1 1 5 1 0 7 9 1 1 0 4 8 5 6 36 36 28 1 1 . 6 4 6 121 9 0 0 1 6 8 0 6 7 2 28 5 2 21 2 0 . 0 5 5 1 2 4 8 3 2 9 0 0 8 1 6 3 3 35 32 1 5 . 0 5 0 1 2 6 8 7 3 8 8 0 5 9 4 3 7 38 25 1 1 . 2 3 4 128 1 0 2 0 9 7 6 5 3 4 4 1 39 21 7 . 8 3 2 13 3 6 3 9 8 0 0 6 0 0 3 1 39 29 8 . 5 3 7 148 2 3 9 2 1 3 4 4 8 8 8 5 2 29 19 2 3 . 8 3 1 152 93 8 7 8 0 4 5 0 43 3 6 21 1 8 . 4 5 4 161 9 1 0 8 3 2 4 3 8 4 1 38 21 1 2 . 6 4 6 167 1 0 5 6 6 7 2 4 7 4 4 8 31 21 1 5 . 2 5 1 170 1 2 9 6 9 2 8 5 5 2 4 7 3 3 20 1 6 . 2 4 4 1 8 4 8 9 6 1 2 4 0 7 3 6 3 1 4 3 26 2 0 . 5 5 0 186 1 4 0 4 9 4 8 7 7 4 4 5 30 25 2 2 . 4 4 5 190 1 1 5 2 8 4 8 7 0 4 4 1 3 1 2 5 2 3 . 0 6 0 19 6 1 4 4 3 1 1 8 0 6 6 4 4 4 36 20 2 3 . 5 5 8 2 1 2 1 0 3 2 8 6 4 6 5 6 41 3 4 25 3 2 . 0 7 2 2 1 5 1 0 4 0 1 5 0 0 7 6 0 32 4 6 2 3 3 0 . 6 7 1 2 2 0 1 1 5 5 1 0 4 0 7 0 4 4 0 36 2 4 2 9 . 5 6 5 22 2 7 5 6 7 6 8 4 9 2 3 7 38 24 3 0 . 4 6 2 2 2 7 1 6 8 6 8 8 4 8 8 12 5 2 3 6 3 3 . 2 2 5 5 72 0 7 0 0 42 6 3 9 38 23 4 3 - 4 3 9 2 5 7 1 7 2 2 1 4 4 0 7 6 0 4 4 37 19 4 1 . 2 6 7 2 61 9 8 4 7 2 0 6 3 2 4 2 3 1 27 4 0 . 5 71 2 6 5 1 2 6 0 1 0 0 8 8 1 2 4 1 3 3 26 4 0 . 5 6 7 2 6 8 1 4 4 0 2 0 6 4 1 0 1 6 3 2 4 6 22 4 1 . 5 4 2 299 1 2 3 6 1 C 0 8 6 5 8 4 3 3 5 2 3 5 0 . 2 7 3 302 7 4 8 7 4 4 3 9 6 4 0 3 9 21 5 5 . 0 6 7 309 1 5 2 1 1 3 2 8 6 0 6 4 4 38 17 5 4 . 2 7 4 311 5 2 8 1 C 0 8 4 2 6 27 5 2 22 5 5 . 4 7 6 3 1 5 1 5 0 7 6 8 5 4 4 11 5 3 37 5 6 . 0 1 0 329 9 8 0 1 4 6 0 68 8 31 4 7 22 6 1 . 5 7 5 3 3 0 7 0 4 6 7 2 4 9 8 38 36 27 6 1 . 6 7 4 185 3 32 1 1 6 4 1 2 9 2 7 8 4 3 6 4 0 2 4 6 2 . 0 7 7 3 3 5 6 6 5 1 0 5 6 6 0 2 29 4 5 26 6 2 . 8 7 7 3 3 7 6 1 6 1 1 4 0 6 8 0 25 4 7 28 6 3 . 5 18 3 4 5 5 6 0 8 6 4 4 2 0 3 1 4 7 2 3 6 6 . 0 7 8 3 5 1 1 3 2 6 1 2 1 6 6 9 0 4 1 38 21 6 5 . 8 1 0 T A B L E V I I : C O R R E C T E D P E A K A R E A S AND CONTENT OF THE T H R E E M A I N C L A Y - M I N E R A L GROUPS M O N T M O R I L L O N I T E { M ) , I L L I T E ( I ) , AND C H L O R I T E + K A O L I N I T E ( S E E T E X T : C + K ) , FOR THE F I N E R - T H A N - 2 . 0 M I C R O N S I Z E -F R A C T I O N OF GROUP B S A M P L E S . DHS=DI S T A N C E FROM SAND H E A D S IN K I L O M E T R E S . & C L A Y R E F E R S TO C L A Y CONTENT OF TOTAL S A M P L E . 186 or meaningful p i c t u r e . Oriented s l i d e s of the. finer—than - ^ 2 . 0 micron f r a c t i o n were X—rayed a f t e r a i r - d r y i n g and following g l y c o l a t i o n . This, treatment served to separate the montmorillonite (expandable f r a c t i o n ) from the c h l o r i t e non-expanding c l a y s ) , and to permit t h e i r comparison with 108 i l l i t e ; a l l measurements were made on the diffractograms from the glycolated samples. The problems encountered with, the d i s t i n c t i o n and consequent quan t i t a t i v e separation of small amounts of k a o l i n i t e i n the presence of c h l o r i t e have been discussed e a r l i e r . I t was eventually decided to c a l l the 78 peak " c h l o r i t e plus k a o l i n i t e " rather than to separate the two, and to use t h i s peak, weighted accordingly, r e l a t i v e to the 108 i l l i t e . While Johns, Grim and Bradley (1954) advocate comparing the 3.58 c h l o r i t e + k a o l i n i t e peak with the 3. 38 i l l i t e , the coincidence of a quartz peak i n th i s p o s i t i o n r e s t r i c t s the usefulness of the i l l i t e 3.38 peak f o r comparative purposes. Analysis of Group A samples and warm HCl treatment of Group B samples, as w e l l as the findings of Mackintosh and Gardner (1966), ind i c a t e that k a o l i n i t e i s present i n only small amounts and therefore the 78 peak i s l a r g e l y c h l o r i t e . Results of the semiquantitative study are presented i n Table VII, which l i s t s weighted peak areas and percentages of montmor-i l l o n i t e (M), i l l i t e ( I ) , and c h l o r i t e + k a o l i n i t e (C+K). The weighted peak area of i l l i t e was assigned a value of 1 and the other peak areas, appropriately weighted, were referred as a r a t i o to i l l i t e . From the rat i o s the percentage contribution of each mineral was calculated assuming they accounted for 100% of the mineralogy; a reasonable assumption f o r the finer—than—2 -microns s i z e - f r a c t i o n . A small error due to the presence of quartz and f e l s p a r , as well as possible 187 v e r m i c u l i t e , w i l l r e s u l t but has been neglected. Results: of the semiquantitative analysis, have been plotted on two f i g u r e s (54 and 55) to determine whether any p r e f e r e n t i a l f l o c c u l a t i o n of c e r t a i n c l a y minerals had occurred. The studies alluded to elsewhere (including Whitehouse et a l . , 1960; G r i f f i n , 1962; Hahn and Stumm, 1970) predict e a r l y , rapid f l o c c u l a t i o n of k a o l i n i t e , c h l o r i t e and i l l i t e i n even low s a l i n i t y water, with the formation of large f l o c c u l e s . Montmorillonite tends to remain dispersed f o r longer, being transported further, f i n a l l y f l o c c u l a t i n g only i n water of higher s a l i n i t y and into samller-sized f l o c c u l e s . Researchers i n the Gulf of Mexico have recognized clay mineral provinces, delineated by the predominance of c e r t a i n clay types, that can be explained by the p r e f e r e n t i a l f l o c c u l a t i o n of the various minerals (e.g. Pisnak and Murray, 1960; G r i f f i n , 1962). It i s quite apparent from Figures 54 and 55 that t h i s s i t u a t i o n does not exist i n the S t r a i t of Georgia. The spread of the sample points i n Figure 54 can be almost covered by a c i r c l e representing an estimated error of measurement of 18%, and even an error of only 10% can account for the v a r i a t i o n among many samples. If p r e f e r e n t i a l f l o c c u l a t i o n had occurred, the r a t i o of montmorillonite to either i l l i t e or to c h l o r i t e + k a o l i n i t e would be expected to increase with distance from the source (Sand Heads). Figure 55 displays no such r e l a t i o n s h i p ; i n f a c t the regression l i n e i s almost h o r i z o n t a l suggesting no c o r r e l a t i o n at a l l . As has been pointed out above t h i s s i t u a t i o n can be explained by the rapid i n f l u x over a short time i n t e r v a l of large volumes of sediment into a semi-enclosed area with an almost closed c i r c u l a t i o n pattern of i n t e n s i v e l y mixed water. The area i s too small and the mixing too thorough to permit the development of clay mineral zones by p r e f e r e n t i a l 188 FIGURE 54: Ternary plot of clay mineral ratios for Group B Strait of Georgia sediments. 189 CO CO Mont,/2(Chlor.+Kaol.) ' IN. CO Ss £ O CO « « 0} o Ss S « CO " C l C N "CM CN ' * - i • • J L CM i - | C i Mont./4(Illite) FIGURE 55: B i v a r i a t e p l o t s o f the r a t i o of m o n t m o r i l l o n i t e to c h l o r i t e + k a o l i n i t e and to i l l i t e ( a p p r o p r i a t e l y weighted peak-area r a t i o s ) a g a i n s t d i s t a n c e from Sand Heads. 190 f l o c c u l a t i o n . 4.4.5 CHEMISTRY To determine the e f f e c t on Fraser River sediments on t h e i r passing from f r e s h - to salt-water environments, three sediment samples were c o l l e c t e d from the Fraser River near the mouth' of Ruby Creek, 12 miles east of Agassiz, B.C., well upstream of possible contamination by salt-water. These samples did not include very coarse sands and gravels. Subsamples were s p l i t from the Fraser River samples, and two from each were placed i n Georgia S t r a i t sea-water (from 200 metres depth, U.B.C. B i o l o g i c a l Oceanography Station No. 1: s a l i n i t y 31.01%. oxygen 3.44 m l . / l . ; October, 1970) f o r 95 days. One of each of the subsample pa i r s was agitated and aerated d a i l y while the other was l e f t undisturbed f o r the duration of the experiment. pH and Eh were monitored over the 95 day period (Figures 56 and 57). pH was measured on the water near the sediment-water i n t e r f a c e using a Portomatic model 175 pH meter. Over the duration of the experiment, the non-aerated sub-samples generally maintained a s l i g h t l y higher pH than the aerated ones. There was an i n i t i a l r i s e i n the pH from 7.0 to nearly 8.0, followed by a decrease to about 7.4. The pH maintained t h i s value f o r nearly 70 days then rose to values near 7.5 f o r the aerated samples and near 8.0 for the non-aerated. They remained reasonably constant then u n t i l the experiment was terminated on the 95th day (Figure 56). Figure 57 shows the highly i r r e g u l a r r e s u l t s obtained from the Eh measurements. L i t t l e emphasis should be placed on the redox values: -the experiment maintained p o s i t i v e values i n d i c a t i n g generally o x i d i s i n g conditions throughout the time involved. In the S t r a i t , however, the 5 ^ i i l ' i ' ' I I 10 20 30 40 50 60 70 80 90 100 Time (days) FIGURE 56: Change i n pH w i t h time f o r n o n - a e r a t e d (A) and a e r a t e d (B) F r a s e r R i v e r samples i n sea w a t e r . • • = FR1,1A; * * = FR2,2A; o o FR3,3A. See t e x t f o r e x p l a n a t i o n of sample numbers. Time (days) 192 FIGURE 57: Change i n Eh w i t h t i m e f o r n o n - a e r a t e d (A) and a e r a t e d (B) F r a s e r R i v e r s a m p l e s i n s e a w a t e r . • = FR 1,1A; * * = FR2,2A; o o = FR3,3A. See t e x t f o r e x p l a n a t i o n o f s a m p l e numbers. Time (days) sea-bottom conditions, are believed, to be more generally reducing at least i n the deep basins. Samples 280 and 350 for example were r e t r i e v e d as o l i v e greenish muds. Aft e r r e l a t i v e l y short exposure to the atmosphere a red-brown surface, that moved inward as an ever—thickening l a y e r , developed. I t i s believed that the laboratory experiment was not an adequate reproduction of the true environment, and no conclusion could be obtained from i t . At the end of the experiment a l l subsamples as well as untreated Fraser River material and nine samples from various locations i n the S t r a i t of Georgia (Group A samples) were analysed f o r t o t a l cation exchange capacities and amounts of exchangeable bases. Acid ammonium oxalate extractions of amorphous, inorganic, oxides and hydroxides of i r o n , manganese, aluminum and s i l i c a were also obtained from these samples. Techniques employed were standard methods of s o i l analysis used i n the Department of S o i l Science, U.B.C. Results are presented i n Tables VIII and IX. Samples prefixed FR are those from the Fraser River: FR1, 2 and 3 were those l e f t undisturbed i n sea-water 5 FR1A, 2A and 3A were the subsamples i n sea-water that were aerated d a i l y ; FR1U, 2U and 3U r e f e r to the raw samples from the Fraser not subjected to sea-water treatment. Ion exchange capacity and other chemical measurements were conducted on whole samples of the sediments, not on the c l a y f r a c t i o n s only. I t has been pointed out by C a r r o l l (1959) that clays are not the only minerals with the capacity for base exchange. Measuring these parameters i n multicomponent systems, such as these samples are, r e s u l t s i n average values from the sediment that are integrated sums of values from the i n d i v i d u a l components. I t i s not possible to use base-exchange 194 capacity to i d e n t i f y clay-mineral groups, under these circumstances. The value of the measurements l i e s more i n t h e i r implications f o r environ-^ mental studies. It Is the sediment's capacity to.adsorb and perhaps f i x introduced ions that i s being measured, not simply that of the clay f r a c t i o n which would be higher and could consequently lead to erroneous assumptions of how much material might be s a f e l y introduced to the system. The data presented here (Table VIII) gives an i n d i c a t i o n of the p o t e n t i a l that Georgia S t r a i t and Fraser River sediments have for adsorbing and " f i x i n g " metal ions. 4.4.5.1 ANALYTICAL METHODS 1. Exchangeable cations and t o t a l exchange c a p a c i t i e s : a. Weigh lOgm. (dry weight equivalent) into 100 ml. centrifuge tubes. b. Add 40 ml. ammonium acetate s o l u t i o n , stopper, shake 5 min., l e t stand overnight, and shake again 5 min. c. Prepare Buchner funnels - Whatman #2 f i l t e r papers plus a layer of " C e l i t e " = and place above c o l l e c t i n g j a r s . d. Transfer contents of centrifuge tube to funnels with suction applied. Rinse tubes and stoppers with ammonium acetate (NH^OAc) so l u t i o n from wash-bottle. e. Wash sample with 4 successive 40 ml. portions of NH^OAc, with a s p i r a t i o n between each wash. f. Transfer the leachatevto 250 ml. volumetric f l a s k , r i n s e b o t t l e with NH.OAc, make volumetric to mark with NH.OAc. Mix we l l . Save 70 to 80 ml. i n a p l a s t i c b o t t l e f or analysis of Na, Ca, K and Mg. (exchange c a t i o n s ) . 1 ml. toluene may be placed i n each p l a s t i c b o t t l e i f samples are to be stored. g. Replace funnels containing NH, +-saturated samples on suction b o t t l e s 195 and wash. wiLth. 3 successive 40 ml. portions of isopropanol, w.Lth_ a s p i r a t i o n between each, washing. Discard washings. Rinse b o t t l e s 3 times with, d i s t i l l e d water. h. Leach sample with 4 successive 50 ml. portions of IN KC1. Transfer leachate to 250 ml. volumetric and make to mark with d i s t i l l e d water. This extract i s used to determine t o t a l exchange c a p a c i t i e s . i . T o t a l exchange capacity i s determined by micro-Kjeldahl determination of NH.+. 4 j . Concentration of exchangeable bases i s determined by atomic absorption (using a Perkin-Elmer model 303 atomic absorption spectro-photometer) . k. Note: samples r i c h i n montmorillonite may undergo a change s i m i l a r to syneresis, r e s u l t i n g i n the sediment cake p a r t i a l l y dehydrating and cracking. The cracks permit easy flow of s o l u t i o n r e s u l t i n g i n values f o r the t o t a l exchange capacities that are too low. One way of combatting t h i s may be to mix the sample with " C e l i t e " or f i l t e r pulp (after the normal " C e l i t e " layer has been constructed). 2. Acid ammonium oxalate extraction .of amorphous, inorganic, i r o n , manganese, aluminum, and s i l i c a : a. Place 1.00 gm. (dry weight) of sample f i n e r than 100 mesh i n 100 ml. tubes. b. Add 40 ml. oxalate s o l u t i o n (700 ml. 0.2M ammonium oxalate plus 535 ml. 0.2M o x a l i c a c i d , adjusted to pH 3) and stopper the tubes t i g h t l y . c. Place the tubes h o r i z o n t a l l y i n a box and shake f o r four hours (extraction must be done i n the dark). d. Centrifuge and analyse the supernatant by atomic absorption 196 spectrophotometry. 4i4.5.2 DISCUSSION Exhaustive studies, and/or discussions, are a v a i l a b l e concerning the changes wrought on clay-mineral suites subsequent to passage from f r e s h - to salt-^water environments or as a consequence of laboratory treatment of clay minerals with sea-water (e.g. Grim and Johns, 1954; Powers, 1957; Johns and Grim, 1958; C a r r o l l , 1959, 1964; C a r r o l l and Starkey, 1960; Pisnak and Murray, 1960; Whitehouse et a l . , 1960; G r i f f i n , 1962; Grim and Loughnan, 1962; Berry and Johns, 1966; K e l l e r , 1970; Naidu et a l . , 1971; Morton, 1972). Despite t h i s abundant l i t e r a t u r e there i s s t i l l controversy over whether the clay-mineral su i t e i n the marine environment i s a r e s u l t of marine diagenesis or an expression of the composition of the source area. Arguments for and against these ideas are presented i n the works c i t e d . Detailed and comprehensive accounts of ion-exchange phenomena and processes are a v a i l a b l e i n the l i t e r a t u r e (see for example and for reference C a r r o l l , 1959; C a r r o l l and Starkey, 1960; and G i l l o t , 1968). Only the r e s u l t s obtained i n t h i s study w i l l be discussed here. C a r r o l l (1959, 1964) and C a r r o l l and Starkey (1960) suggest that base exchange, also referred to a s i ion-exchange (which does not r e s -t r i c t the process to metal or hydrogen cations) or cation exchange, occurs as a prelude to diagenesis when clays are moved from f r e s h - to salt-waters. They also showed that Mg ions tend to move into exchange po s i t i o n s i n preference to either Na or Ca despite the f a r greater concentrations of the former i n sea-water, and the apparently greater bonding energy of the l a t t e r . 197 SAMPLE CA NO. FR 1 10.94 FR IA 11.56 FR2 11.2 5 FR2A 10.63 FR3 8.13 FR3A 8.75 FR1U 13.44 FR2U 13.44 FR3U 10.94 GS23 15.00 GS53 8.7 5 GS 102 9.69 GS145 5.94 GS162 5.94 GS263 5.63 GS280 10.94 GS342 7.50 GS350 10.63 *MURR.1 13.83 * JACK.6 7.64 #LEHM.1 3.68 *HAN.l 8.00 MG NA K 3.75 2.20 0.69 3.97 2.67 0.56 4.66 2.53 0.66 3.63 2.67 0.53 3.22 1.69 0.53 3.19 2.39 0.56 1.63 0.15 0.27 1.75 0. 26 0.28 1.31 0.22 0.32 8.22 3.19 2.81 12.28 2.48 3. 75 7.91 1.99 1.84 12.25 2.63 3.41 11.63 6.34 3.41 15.94 5.25 5.03 33.13 5.25 7.63 23.38 8.25 9.50 33.88 6. 11 7.72 2.02 0.79 0.53 5.99 0.42 0.48 1.72 0.005 0.42 11.62 0.13 0.66 M-EXCHANGE 1CLA Y CAPACITY 8.36 8.24 10.96 7.89 6.96 7.77 6.73 10.2 8.29 12.3 6.90 9.2 16.79 14. 7 40.89 3 0. 5 14.76 15.2 30.00 56.6 30.68 35.7 29.38 46.7 39.51 72. 1 34.28 58.6 31.37 75.6 23.45 20.92 7.42 27.89 TABLE V I I I : EXCHANGEABLE CATIONS AND ION-EXCHANGE CAPACITIES, FRASER RIVER* GEORGIA STRAIT, AND GLACIOMARINE UPLAND SOILS (* AFTER AHMAD, 1955; MUR*AYVILLE, JACKMAN ROAD, LEHMAN ROAD, AND THE HANEY CLAY P I T ) . VALUES ARE RECORDED AS MILLIEQUIVALENTS PER 100 GRAMS OF DRY SAMPLE (MEQ/100GM). 198 j | While the. content of exchange Ca does not show, any consistent d i f f e r e n c e s between the untreated or treated Fraser River or Georgia ++ + + S t r a i t samples, the contents of Mg , Na and K do (Table V I I I ) . These cations are a l l taken up by the sediments a f t e r contact with sea^water. Of them the change In the Mg content i s by f a r the greatest, substan-t i a t i n g the experimental findings of C a r r o l l and Starkey (1960. The Na + increase i s reasonably obvious but K + does not seem to be taken up by the sediment a f t e r only a short time i n sea-water. Samples from Georgia S t r a i t have exchangeable base concentrations that seem to be related to the distance the sample i s from Sand Heads which, i f a l l sediment i s considered to be derived from the Fraser River, implies a longer transport time during which the sediment i s i n reactive.contact with sea-water. T o t a l exchange capacity i s also r e l a t e d to the clay content of the sample. Samples close to Sand Heads (102) have values, e s p e c i a l l y f or Na + and K +, that are l i t t l e d i f f e r e n t from the values obtained from sea-water treated subsamples from the Fraser River. Georgia S t r a i t samples 280, 342 and 350, the furthest away of a l l from Sand Heads, had the highest values for a l l exchangeable base concentrations. S i g n i f i -c antly, the values for t o t a l exchange capacities have a p r a c t i c a l l y i d e n t i c a l d i s t r i b u t i o n . Contents of inorganic, amorphous oxides and hydroxides removed by oxalate extraction show an only s l i g h t l y d i f f e r e n t p i c t u r e (Table IX). In none of the cases (Fe, Mn, A l , Si) did the untreated Fraser River samples d i f f e r s i g n i f i c a n t l y from the treated ones. Iron values are f a i r l y uniform throughout the e n t i r e set of samples. Aluminum, manganese and s i l i c a show increasing concentrations for samples taken at Increasing distances from Sand Heads and with high contents of c l a y - s i z e material. 199 >AMPLE 3IIRON %ALUMI NUM MANGANESE S I L I C A NO. PPM PPM FR1 .564 .1312 208.0 2440.0 FR 1A .536 .1400 246.0 27 20.0 FR2 .640 . 1744 272.0 272 0.0 FR2A .552 .1620 228.0 3200.0 FR3 .528 .1168 150.0 2400.0 FR3A . 498 .1232 148.0 2520,0 FR1U .580 . 1424 226.4 2320.0 FR2U .634 .1520 225.6 24 00.0 FR3U .600 .1208 176.0 2440.0 GS23 .364 .1328 28.0 2240.0 GS53 .32 8 .2480 34.0 3360. 0 GS102 .620 .1696 91.2 4 G 00.0 GS145 .5 54 .3520 132.8 5440.0 GS162 .646 . 2840 88.0 512 0.0 GS263 .268 .3280 47.2 3400.0 GS280 .552 .3540 3408.0 5520.0 GS342 .408 .3568 335.2 4500.0 GS350 .468 .4080 798. 4 5360. 0 TABLE IX: CONCENTRATICNS OF AMORPHOUS INORGANIC OXIDES EXTRACTABLE WITH ACID AMMONIUM OXALATE. 200 The manganese values, show t h i s p a r t i c u l a r l y c l e a r l y . Sample 280 has a marked anomaly i n i t s concentration of manganese, the value being nearly an order of magnitude greater than for the next highest concen-t r a t i o n , while the c l a y content i s about the same, and distance from Sand Heads s l i g h t l y l e s s . Table X did not i n d i c a t e any s i g n i f i c a n t c o r r e l a t i o n s between the concentration of manganese and the clay content, or any other of the variables considered. The control of the concentration of manganese i s not known. The r e s u l t s obtained from the determinations of exchangeable base contents, t o t a l exchange c a p a c i t i e s , and acid ammonium oxalate extractions were submitted to c o r r e l a t i o n analysis using the Small Triangular Regression Package (STRIP) computer programme from theJU.B.C. Computing Centre l i b r a r y . The data was submitted i n three ways: (1) using only the samples from the Fraser River; too few observations were included for s i g n i f i c a n t c o r r e l a t i o n s to be obtained; (2) a l l the Georgia S t r a i t plus the three subsamples from the Fraser River that had not been subjected to sea-water treatment; (3) a l l 18 samples (Table X). Values for the c o r r e l a t i o n c o e f f i c i e n t ("r") i n d i c a t i n g s i g n i f i c a n c e at the 1% and 5% l e v e l s are included i n Table X. From Table X, i t seems reasonable to suggest that the amount of clay i n a sample exerts the most c o n t r o l on exchange capacities and concentration of some exchange ions or oxalate-extractable elements. The very high c o r r e l a t i o n between clay content and oxalate extracted aluminum at the 1% l e v e l i n a l l cases suggests a basic r e l a t i o n s h i p between the two, but i t i s not understood. C a r r o l l and Starkey (1960) found that A^O^ (as w e l l as SiO^ and Fe20^) was dissolved from clay minerals, probably by i t s removal from the octahedral layer. A l 0 VARIABLE I CLAY MEDIAN SIZE IRON ALUMINUM MANGANESE S I L I C A CALCIUM MAGNESIUM SODIUM POTASSIUM EXCI1. CAP. % ORGANIC C >-< 1.0000 0.9815 0.3316 0.9777 0.54S0 0.0139 0.4209 0.9496 0 . 764 5 0.9237 0.8674 0.9006 TABLE X Q W 2 2 o :=> < w Ui < < co D t—I C J —1 < u I—I co w z < Q O CO co co < H O a. a, a: C J x w 1.0000 -0.2567 1.0000 -0.9870 -0.3333 0.4983 0.0983 0.0015 0.0201 -0.5165 0.2146 0.8962 -0.3537 0.7703 -0.3949 0.8921 -0.4783 0.8525 -0.4772 0.9004 -0.3156 1.0000 0.4140 1.0000 -0.0325 0.0423 -0.5209 0.1278 0.8952 0.6495 0.7841 0.2968 0.8966 0.4839 0.8832 0.4080 0.8960 0.3291 1.0000 -0.3015 1.0000 0.0213 -0.2564 0.0074 -0.4855 -0.0066 -0.3504 -0.0448 -0.4891 -0.0091 -0.3571 1.0000 0.7885 1.0000 0.9433 0.8696 0.8272 0.7279 0.8444 0.7850 1.0000 0.8633 1.0000 0.9080 0.7430 C o r r e l a t i o n s between t w e l v e v a r i a b l e s d e t e r m i n e d f r o m e i g h t e e n s a m p l e s : n i n e f r o m G e o r g i a S t r a i t and n i n e f r o m t h e F r a s e r R i v e r (see e x p l a n a t i o n i n t e x t ) . To be s i g n i f i c a n t a t t h e 51 and 11 l e v e l s , ' r ' must be g r e a t e r t h a n 0.792 and 0.842 r e s p e c t i v e l y . o 202 i s i n s o l u b l e at the. pR of sea-water, and the process, was believed to be p o s s i b l y due to a complexing reaction with: organic material. If the Al^O^ hydrolysed, i t could become a v a i l a b l e f o r the formation of gib b s i t e j - l i k e material that could combine with montmorillonite or vermiculite c l a y minerals to form either a c h l o r i t e or a mixed-layer montmorillonite-chlorite mineral. Z e o l i t e s have not been recognised i n the X-ray diffractograms. These minerals have high exchange capacities s i m i l a r to those of the clay minerals ( C a r r o l l , 1959). Other minerals can also take part i n exchange reactions, p a r t i c u l a r l y i f present as small grains. The cation exchange c a p a c i t i e s of the sediments considered here, however, must be l a r g e l y determined by the clay mineral content, and i s an averaged value of the exchange capacities of the various clay mineral species present. C a r r o l l (1959) records the ranges of cation exchange capacities f or various clay mineral groups, the range being a function of differences i n structure, s i z e and chemical composition of the members of the groups. The recorded ranges are (in m i l l i e q u i v a l e n t s of base exchangeable per 100 grams of dry sediment): k a o l i n i t e 3 - 1 5 ; montmorillonite 7 0 — 100; i l l i t e 10 - 40; v e r m i c u l i t e 100 - 150; glauconite 1 1 - 2 0 . I | The p r e f e r e n t i a l uptake of Mg by clay minerals, whether i n I j | exchange positions or s u b s t i t u t i n g f or A l i n octohedral p o s i t i o n s , i s recorded by numerous workers (e.g. C a r r o l l , 1959, 1964; C a r r o l l and Starkey, 1960). Mackintosh and Gardner (1966) consider t h i s process to be occurring i n sediments from the sea (Georgia S t r a i t ) , and the high c o r r e l a t i o n between clay content and exchange Mg recorded here, as well I | as the obvious marked increase:ih Mg content from untreated (FR1U etc.) to treated (FR1 IA etc.) Fraser River and Georgia S t r a i t samples seen 203 on Table V I I I substantiates t h i s hypothesis. The c o r r e l a t i o n between c l a y content and % organic carbon i s discussed i n the next chapter. It I s a commonly observed and anticipated r e l a t i o n s h i p (see references quoted, and Hahn and Stumm, 1970). The i n t e r p r e t a t i o n of studies of ion exchange capacities and exchangeable or extractable ion contents i s neither easy nor, i n the case of marine sediments, s a t i s f a c t o r y because of the uncontrollable changes to chemical e q u i l i b r i a that can occur. Any addition of water w i l l a l t e r the chemical equilibrium of populations of exchange cations. It i s also believed ( C a r r o l l , 1959) that values obtained f o r calcium may not r e f l e c t the true exchange calcium contents as t h i s ion tends to be p r e f e r e n t i a l l y adsorbed onto other cations. C a r r o l l and Starkey (1960) emphasise the complicated nature of exchange reactions, pointing out I | that the d i f f e r e n t bonding energies of the common exchange cations Ca , Mg , Na , and K , the e f f e c t of cations already held i n exchange p o s i t i o n s , the v a r i a t i o n s i n charge of the exchange p o s i t i o n s , the i o n i c a c t i v i t y and the buffer mechanism of sea-water a l l contribute to t h i s complexity. The bonding energies, or order of r e p l a c e a b i l i t y , has been found to be: Li<Na<K<Rb<Cs and Mg<Ca<Sr<Ba ( C a r r o l l and Starkey, 1960). Of the usually encountered cations, the order i s Na<K<Mg<Ca. However occasionally the order can be Ca<Mg ( C a r r o l l and Starkey, 1960), and "H" + | | Mg ions move in t o exchange posit i o n s i n preference to Na or Ca That Mg w i l l be p r e f e r e n t i a l l y adsorbed over Na , which i s present i n sea-water i n f a r greater concentrations, i s due to the p r e f e r e n t i a l uptake of divalent over monovalent cations by clays. The p r e f e r e n t i a l uptake I | | j of Mg over Ca when the l a t t e r has the higher bonding energy i s explained by C a r r o l l and Starkey (1960) as a function of greater 204 I | a v a i l a b i l i t y of Mg ions i n sea-water. 4.4.6 FINE-SEDIMENT TEXTURES Textural studies were made of four separate materials of the c l a y — s i z e f r a c t i o n s using a Cambridge Stereoscan Scanning Electron Microscope (SEM). The features studied included freeze-dried clay from sample 280 ( i t was hoped that freeze-drying would remove adsorbed and occluded water leaving the c l a y structure i n much the same state as when i t had s e t t l e d ) , f a e c a l p e l l e t s , mud lumps and glauconite grains. The l a s t three were examined i n an attempt to determine whether the self-aggregation process to form mud lumps or f l o c c u l e s , as advocated by Pryor and Vanwie (1971), could be recognised. Pryor and Vanwie (1971) sug-gested a d i f f e r e n t i a l f l o c c u l a t i o n mechanism of suspended clay material with the formation of f l o c c u l e aggregates i n an a g i t a t i n g , turbulent environment to explain the o r i g i n of the aggregate grains i n the Eocene "Sawdust Sand" of Tennessee. The transportation and sedimentation of s i l t s and clays as f l o c c u l e s has been described and discussed by, among many others, Gripenberg (1934), Sherman (1953), Lambe (1960), Rosenqvist (1958, 1959, 1962), Whitehouse et a l . (1960), Belderson (1964), Meade (1964), Hahn and Stumm (1970),, Pryor and Vanwie (1971), Biddle & Miles (1972). The clay-mineral s u i t e i n the S t r a i t of Georgia i s transported i n and sedimented from a weak s a l t s o l u t i o n . Floccules are expected and the anticipated f a b r i c of the f l o c c u l e s would be close to a perpen-d i c u l a r , card-house-type array (Lambe, 1960) or the edge-edge and edge-face types of Pryor arid Vanwie (1971) (Figure 58). The freeze-dried sample was expected to give some idea of the nature of the o r i g i n a l f l o c c u l e s , 205 E x p l a n a t i o n o f F i g u r e 58. ( a ) , ( b ) , (c) and (d) are from P r y o r and Vanwie (1971) : (a) = f a c e - f a c e ( F F ) ; (b) = edge-edge ( E E ) ; (c) = edge-f a c e ( E F ) ; (d) = edge-edge, f a c e - f a c e , e d g e - f a c e , and g r a i n s , (c) i s the b a s i c Goldschmidt - Lambe concept o f the cardhouse s t r u c t u r e . (c) and (d) appear to be the p a r t i c l e arrangements d i s p l a y e d i n F i g u r e 62 (a - k ) . (e) , ( f ) and (g) are from Meade (1964) , a f t e r Lambe (1960), (e) = edge-face f l o c c u l e s from s a l t - f r e e w a t e r ; ( f ) = f a c e - f a c e f l o c c u l e s from s a l t s o l u t i o n ; (g) = p r e f e r e n t i a l l y o r i e n t e d , o r Lambe's (1960) d i s p e r s e d system. ( h ) , ( i ) and ( j ) are from R o s e n q v i s t (1962), showing i n an i d e a l i s e d way the Goldschmidt - Lambe cardhouse s t r u c t u r e . (h) = u n d i s t u r b e d , s a l t - w a t e r d e p o s i t ; ( i ) = u n d i s t u r b e d , f r e s h - w a t e r d e p o s i t ; ( j ) = remoulded s t r u c t u r e . Lambe (1960) t h e o r i s e d t h a t p a r t i c l e s s e t t l i n g from a d i s p e r s e d system r e s u l t e d i n a p a r a l l e l arrangement of p l a t e s w i t h consequent e f f i c i e n t p a c k i n g . When p a r t i c l e s are f l o c c u l a t e d i n , and s e t t l e from, s u s p e n s i o n , the f l o c c u l e s are c l o s e r t o a p e r p e n d i c u l a r a r r a y , w i t h more p l a t e s p a r e l l e l i f the s u s p e n s i o n i s n o n - s a l t y (non-e l e c t r o l y t e ) , but m o s t l y p e r p e n d i c u l a r i f s a l t - f l o c c u l a t e d . 206 FIGURE 58". Various concepts of the arrangements of clay particles in sediments and floccules. Explanation on opposite page. 207 assuming that the structure was s t i l l preserved. P a r t i a l or complete destruction of f l o c c u l e structure was anticipated i n the f a e c a l p e l l e t s . The mud lumps and the glauconite grains, however, although not believed to represent the same thing and coming from quite d i f f e r e n t environments, were believed to have been at least p o t e n t i a l l y i d e a l for t e s t i n g Pryor and Vanwie's (1971) concept of aggregated f l o c c u l e s . The freeze-dried c l a y and the f a e c a l p e l l e t s were chosen as " c o n t r o l " features against which the f a b r i c of the lumps and the glauconite could be compared. Treatment of the samples p r i o r to SEM study was very simple. It involved only a i r - d r y i n g the p e l l e t s , lumps and glauconite, and cementing these (as whole arid broken grains) plus some of the freeze-dried mud to separate specimen stubs with S i l v e r Dag. The samples were coated with gold to render them conducting. The a i r - d r i e d material gave few problems during examination, but the freeze-dried mud seemed to change volume s l i g h t l y under electron bombardment, developing minute cracks i n the gold coating which resulted i n the formation of discharge l i n e s across photographs. Sample 280 i s a l a r g e l y c l a y - s i z e d (72% clay; median diameter 9.2 phi) sediment with a f a i r l y high water content (67%) that was o r i g i n a l l y a drab olive-greenish colour. A f t e r freeze-drying a f i n e , pale reddish brown, f l u f f y , loose powder remained. Some coarse s i l t -sized grains could be detected by rubbing the powder between the f i n g e r s . These grains may have been c a r r i e d even as f a r as s i t e 280 as an i n t e g r a l part of a clay-mineral f l o c c u l e (Biddle & Miles, 1972). Features referred to as p e l l e t s are e l l i p s o i d a l , generally f a i r l y smooth-surfaced aggregates that are a uniform drab grey colour 208 i n a l l samples, and are most common i n the 32 to 60 mesh range. The p e l l e t s viewed w i t h the SEM were from l o c a l i t y 150, but are not r e s t r i c t e d , to t h i s s i t e . They were common i n samples from bank or r i d g e tops and where p o o r l y sorted g r a v e l l y or coarse sandy muds were c o l l e c t e d . The mud'lumps are an enigma. They are i r r e g u l a r shaped, o f t e n s p h e r o i d a l , p a l e g r e e n i s h lumps w i t h , when dry,' a cracked, almost b o t r y o i d a l , surface. They have been found i n many of the sandy mud samples, p a r t i c u l a r l y those c o n t a i n i n g very coarse sands and g r a v e l s . They were not found i n the s i z e - a n a l y s e d samples, presumably because the d i s p e r s i o n treatment destroyed them i f they were present. The problem they pose i s one of o r i g i n . Three p o s s i b i l i t i e s e x i s t , none of which can p r a c t i c a l l y be discounted: (1) they could develop sl o w l y i n the container of stored sediment during slow dr y i n g out of the sample, t h e i r shape and surface f e a t u r e s then r e f l e c t i n g shrinkage on w a t e r - l o s s ; (2) they could be produced a r t i f i c i a l l y as a f u n c t i o n of washing (using a w r i s t a c t i o n shaker, which a g i t a t e s by o s c i l l a t i n g the sample through a small arc) and w e t - s i e v i n g to separate the sands from muds; (3) t h e i r o r i g i n could be n a t u r a l , by aggradation of mud on the bottom i n a s l i g h t l y t u r b u l e n t , c u r r e n t - a f f e c t e d , environment. In s i z e they are i r r e g u l a r and v a r i a b l e , being present i n most sand grades. L i k e the g l a u c o n i t e , they are not f l o c c u l e s , s i n c e the s i z e of f l o c c u l e s tends to be smaller (20-50 microns) and l i m i t e d (Gripenberg, 1934; Lambe, 1960; Belderson, 1964). I t i s p o s s i b l e too that these lumps are not only formed by the t h i r d a l t e r n a t i v e but a l s o represent a low-order form of g l a u c o n i t e (Burst, 1958a, b). C o m p o s i t i o n a l l y they are not s i g n i f i c a n t l y d i f f e r e n t from the usual c l a y mineralogy. I t must be emphasised, however, that an 209 a r t i f i c i a l origin, as a function of s i z e separation by sieving cannot be disregarded. The glauconite grains pose no such problems. They were found i n a core (300C) } £n greater concentration near the top, taken from an area where sedimentation i s r e l a t i v e l y low (see above, Chapter 3). Their shape i s generally quite i r r e g u l a r but rounded, ranging from e l l i p s o i d a l to spheroidal. S i z e i s v a r i a b l e , generally i n the coarse to very coarse sand grade, and much larger than the f a e c a l p e l l e t s . Their colour i s s i m i l a r to those described by Van Andel (1964), pale-greenish i n s i d e a dark green, almost black, t h i n outer skin. When wet they are a more uniform dark green. M i n e r a l o g i c a l l y they have a high content of montmorillonite. These grains are therefore glauconite i n the morphological sense (Burst, 1958; Degens, 1965), not the mineralogical. Reviews of the nature, mineralogy, geochemistry and formation of glauconite are a v a i l a b l e i n Could (1965), Burst (1957a, b), Hower (1961) and Degens (1965). It i s s u f f i c i e n t to point out that most of the conditions favouring the syndepositional formation of glauconite are met i n t h i s environment. A r e l a t i v e l y slow rate of sedimentation i s suspected; 2:1 layer clays are present; the environment i s marine, and reducing; organic material i s a v a i l a b l e but not abundant. Although not measured i n t h i s sample, i r o n and potassium are a v a i l a b l e i n other sediments i n the S t r a i t . Clay f a b r i c s of the freeze-dried sample are i l l u s t r a t e d i n Figure 59 (a - d). The i l l i t e (mica) and organic constituents (diatom mainly) are quite d i s t i n c t i v e ; other components are not i d e n t i f i a b l e . The s i z e of components ranges from s i l t through clay, and the coarser p a r t i c l e s exert a modifying Influence on the f l o c c u l e and packing structure. The f a b r i c of t h i s sediment i s not obvious but seems to be a 210 FIGURE 59: Scanning E l e c t r o n Microphotographs of te x t u r e s from f r e e z e - d r i e d mud. Sample 70-1-280. 211 212 FIGURE 60: Scanning E l e c t r o n Microphotographs o f t e x t u r e s from f a e c a l p e l l e t s . Sample 70-1-150. F i g u r e 60 c o n t i n u e d . 214 mixture of edge-edge, edge-face, face-face and grains, modified toward a remolded s t r u c t u r e (Figure 58). Packing of grains and f a b r i c i n f a e c a l p e l l e t s from sample 150 are revealed i n Figure 60 Ca — d). Organic debris and what appear to be micaceous mineral fragments are conspicuous but the packing f a b r i c i s not c l e a r . Because of the o r i g i n of f a e c a l p e l l e t s no f a b r i c was expected to be preserved. Surface features and some i n t e r n a l structure of the enigmatic mud lumps are shown i n Figure 61 (a - g). Figure 61 (a) and (b) show two v a r i a t i o n s of surface texture, the smooth and botryoidal types r e s p e c t i v e l y . Figures 61 (c) through (g) portray i n t e r n a l features of the mud lumps. Figures 61 (c) and (d), while resolving the p l a t e - l i k e habit of the mineral grains, do not reveal obvious f a b r i c . I f anything, the f a b r i c of 61(c) i s of the face to face type. Figures 61 (e) through (g) however represent progressive enlargements of a zone of what appears to be clay f l o c c u l e s with very obvious and spectacular f a b r i c . The open, card-house structure of Lambe (1958) and Rosenqvist (1958, 1962) i s c l e a r l y shown. Although the thickness of the gold coating has rendered Figure 61 (c) a l i t t l e fuzzy at high magnification, an open, edge-edge and edge-face arrangement of p a r t i c l e s i s evident. Although only a r e l a t i v e l y small area within a mud lump, t h i s type of structure i s suggestive of an agglutinated or aggregated f l o c c u l e o r i g i n , which would support the idea of formation of the mud lumps. An aggregated f l o c c u l e o r i g i n , i n which the f l o c c u l e s have an open, perpendicular array structure (Lambe, 1958), i s even more evident i n the electron photomicrographs of the glauconite grains (Figure 62, a - m). Edge-edge, edge-face and face-face arrangements are 215 FIGURE 61: Scanning E l e c t r o n Microphotographs o f t e x t u r e s from a g g l u t i n a t e d mud lumps. Sample 70-1-150. (c) X5000 F i g u r e 61 c o n t i n u e d . 217 F i g u r e 61 c o n t i n u e d . F i g u r e 61 c o n t i n u e d . 219 FIGURE 62: Scanning E l e c t r o n Microphotographs o f t e x t u r e s from g l a u c o n i t e p e l l e t s . Sample 70-1-300C. F i g u r e 62 c o n t i n u e d . F i g u r e 62 c o n t i n u e d . 222 F i g u r e 62 c o n t i n u e d . F i g u r e 62 continued. F i g u r e 62 c o n t i n u e d , 225 apparent. The face—face, arrangement (Figure 62 .(f), (j) and (JO) seems, to have developed By remolding or s l i g h t compaction of an o r i g i n a l l y predominantly edge-edge, and/or edge—face structure. Fabrics portrayed by the mud lumps and glauconite confirm the "corner plane-cardhouse" (or Goldschmldt-Lambe) theory of mineral arrangement i n f l o c c u l a t e d clays (Rosenqvist, 1958; Lambe, 1960; Meade, 1964). That no d i s t i n c t i v e f a b r i c could be recognised i n the fae c a l p e l l e t s was to be expected, and at least supports an argument against a f a e c a l o r i g i n of the mud lumps and glauconite grains. The apparent absence of open f a b r i c In the freeze-dried clay was disappointing. It may be a r e f l e c t i o n of the sample preparation, or even the sampling process. Freeze-drying samples c o l l e c t e d with a grab or corer that produces le s s sample compression and disturbance than a LaFond-Dietz or Phleger r e s p e c t i v e l y might reveal or preserve o r i g i n a l f l o c c u l e structures. That the f a b r i c structures, which appear f a i r l y d e l i c a t e , should be preserved i n the lumps and glauconite grains i s believed to r e s u l t from the eventual protection of the inner portions of these grains from further disruption. The outer surfaces are always smoother and do not show f a b r i c structure. Slow sedimentation and perhaps r e l a t i v e l y gentle a g i t a t i o n may be the explanation f o r the better preservation of the open structures i n glauconite grains compared to those of the mud lumps. 4.5 SUMMARY AND CONCLUSIONS The Fraser River i s the'-iprimary source f o r the Recent sediments i n the S t r a i t of Georgia. This, r i v e r has an immense watershed involving a wide v a r i e t y of rock types. I h i i t s lower reaches (south of Quesnel) 226 much of i t s course i s through s o f t , e a s i l y eroded, g l a c i a l d r i f t and t i l l . A l a r g e part of i t s load is. derived from t h i s material. Within the S t r a i t , l o c a l sources of sediment include Pleistocene deposits such as Point Grey and Point Roberts, and the upstanding ridges within the S t r a i t , also l a r g e l y of Pleistocene g l a c i a l and i n t e r g l a c i a l material ( T i f f i n , 1969). Marginal areas of the S t r a i t north and west of the Fraser Delta are of only minor, l o c a l importance. No coarse sediment reaches the study area from Vancouver Island. This s i t u a t i o n imposes a monotonous s i m i l a r i t y on the sediment composition within the S t r a i t of Georgia, a feature p a r t i c u l a r l y evident from the mineralogy of the s i l t and clay s i z e grades. Most of the sand-size material separated from the samples co l l e c t e d occurred i n the fine-sand grade. I t s composition i s dominated by quartz, f e l s p a r and ferromanganesian minerals (mostly amphiboles). Mica i s conspicuous i n most samples although not nec e s s a r i l y abundant. The d i s t r i b u t i o n of muscovite i s greater than has been known, and the p r o b a b i l i t y of i t s o r i g i n from more sources than just the Fraser River has been established. This reduces i t s value as a source i n d i c a t o r . Pink garnet i s conspicuous,aalthough present i n small q u a n t i t i e s , i n a l l samples. The mineralogy of the sub-sand-size f r a c t i o n s i s remarkably consistent. Minor qu a n t i t a t i v e d i f f e r e n c e s are indicated by v a r i a t i o n i n X-ray d i f f r a c t i o n peak i n t e n s i t i e s , but the same mineralogy i s recorded throughout the S t r a i t . Coarse and medium s i l t f r a c t i o n s are b a s i c a l l y s i m i l a r to the f i n e and very f i n e sands. In the f i n e s i l t f r a c t i o n p h y l l o s i l i c a t e minerals become more prominent, eventually dominating the mineralogy i n the c l a y f r a c t i o n s . Mica, montmorillonite, and c h l o r i t e are the main c l a y mineral types. Some k a o l i n i t e i s 227 suspected as w e l l as, i n untreated samples,, jnixed-rlayer clays. D i f f e r e n t i a l f l o c c u l a t i o n and segregation of clay-mineral species In the marine environment of the S t r a i t does not occur. A l t e r a t i o n of the c l a y s u i t e on passing from fresh water to the marine environment i s minor, and i s revealed as an increase i n content of exchangeable cations, p a r t i c u l a r l y magnesium. A s i g n i f i c a n t c o r r e l a t i o n e x i s t s between the content of clay-sized material i n a sediment and i t s exchange capacity, exchange cations, and contents of some oxides and hydroxides. S i m i l a r i t y of Fraser River and Georgia S t r a i t samples implies that the mineralogy i n the S t r a i t r e f l e c t s the source composition and i s not a function of marine diagenesis,.' Examination of mud f a b r i c s with the scanning electron microscope indt'catfes that f l o c c u l a t i o n i s an important process i n clay sedimentation, with the formation of open, card-house type or perpendicular array structures. 228 CHAPTER 5 GEOCHEMISTRY 5.1 INTRODUCTION A b r i e f and mainly d e s c r i p t i v e account Is given of the d i s t r i b u t i o n and content of carbon, of organic and carbonate o r i g i n , i n the sediments of Georgia S t r a i t . Nodular ferromanganese accretions c o l l e c t e d from two sampling s i t e s i n the S t r a i t are described. 5.2 CARBON 5.2.1 TECHNIQUES The carbon contents of one hundred and forty-two S t r a i t of Georgia and three Fraser River sediment samples were measured i n duplicate with a LECO model 572-100 Carbon Determinator (Laboratory Equipment Corporation, St. Josephs, Michigan). Samples were oven-dried at low temperature (less than lOO^C), crushed i n a po r c e l a i n mortar to pass a 35 mesh sieve, and subsampled by quartering. T o t a l carbon content was determined from one subsample, and organic carbon was determined on;another subsample following treatment with 5% HCl to d i s s o l v e carbonates (Frankenberg and G i l e s , 1970). The difference between the two r e s u l t s gave a measure of the carbonate carbon content. The LECO Carbon Determinator measures carbon contents gaso-m e t r i c a l l y , a f t e r o x i d i s i n g a sample i n a stream of oxygen, with i r o n and t i n accelerators, i n a high temperature induction furnace. Carbon contents of small samples (usual sample weight i s 1.0 or 0.5 gm.) can be analysed with high p r e c i s i o n . Van Andel (1964) quotes a r e p r o d u c i b i l i t y of 0.02% carbon. A r e p r o d u c i b i l i t y of ± 0.1% between duplicates of S A M P L E TOTAL NG. CARBONS ORG A IS I C X1 . 7 2 = « CARB CN^ ORGANIC MATTER CAR BCNAT E CARBON % X€ .33=? CARBONATE AS CAC03 IC 1.38 G.53 0.91 0.85 7.C9 13 1.08 G.6 0 1 .03 0.48 4.02 19 1.42 0.58 1 .00 0.84 6. 96 21 0.34 G. 19 0 .33 0. 15 1.21 23 0.87 C.60 1 .03 0.27 2.22 25 0.98 G.67 1.15 G.31 2.53 40 1.16 0.7 1 1.22 0.45 3.68 42 1 .77 C.73 1 .26 1.04 8.61 44 1.11 0.90 1.55 0.21 1.77 45 1.52 0.9 1 1.57 0.61 5. 11 46 2.30 0.55 0.95 1.75 14.51 48 0.86 0.46 0.79 0.40 3.34 5C 0.91 0.35 0.60 0.56 4.65 53 1.18 0.84 1 .44 0.34 2.83 54 0.69 0.56 0 .96 0.13 1.08 56 0.57 C.42 0.72 0.15 1.21 58 0.66 0.47 0.81 0. 19 1.57 6C 0.75 G.54 0.93 0.21 1.74 62 0.76 C.52 0.89 0.24 2.03 7 3 1.26 G.E 7 1.50 C.39 3.23 75 1 .05 0.75 1 .29 C.30 2.49 76 1.0 8 0.78 1 .34 0.30 2.49 77 1.06 G.64 1 ,1C 0.42 3.51 79 0.94 0.67 1.15 C. 27 2.25 81 0.71 C.45 0.7 7 C.26 2.12 82 0.09 0. 07 0.12 0.02 0. 16 83 0.18 C. 18 0.31 G.00 G. CO 85 0.78 0.52 0.8 9 0.26 1.34 86 1.07 0.55 0.95 0.52 4.33 87 1. 54 C. 99 1.70 0.55 4.55 88 1.27 0.72 1 .24 G.45 4.58 89 1.20 G.77 1 .32 0.43 3.58 92 0.57 C.55 0.95 0.02 0.17 93 0.69 0.5 1 0.88 0. 11 0. 92 96 1.51 0.93 1 .60 G. 58 4.84 97 1.47 1. C4 1 .79 0.43 3.53 98 1.55 l.C-2 1.75 C. 53 4.37 100 1 .25 0.76 1 .31 G.49 4.02 102 0.84 0.48 0.83 0.36 2.96 1C3 1.04 0.56 0.96 0.48 3.99 104 1.18 0.66 1.14 C.52 4.38 1C6 1.16 C.65 1.12 C.51 4.26 108 1. 56 1.01 1 .74 0.55 4.59 1C9 1 .46 l.CO 1.72 G.46 3. 84 I l l 1.08 0.72 1.24 C.34 3. 06 113 1 .46 1 . 07 1.84 C.39 3.26 114 1.42 1.C1 1 .74 0.41 3.46 115 1.54 1.48 2.55 C.06 0.50 116 1 .37 1.10 1.89 C.27 2.25 121 1 .37 1. 19 2.05 0. 18 1.5C 124 1.18 1.14 1 .96 0.04 0.33 125 1.55 1.30 2.24 0.25 2. 08 126 1.40 1.21 2.08 0.19 1.58 128 1.15 1.01 1 .74 0.14 1.17 129 1.20 0.91 1 .57 G.29 2.42 133 1 .45 1. 13 1 .94 0.32 2.67 141 1 .49 1.3 3 2.29 G. 16 1.33 145 1.35 1.30 2.24 C.05 0.42 14 7 1.22 1.21 2.08 0.01 0.08 148 1.08 C.99 1 .70 0.09 0.75 149 1.18 0.98 1 .69 0.20 1.67 152 1.44 1. 34 2.3G C. 10 0.83 15 3 1.56 1 .36 2.34 C.20 1.67 16 C 1.4 6 1.24 2 .13 0.22 1.83 16 1 1.22 1.C6 1.82 G. 16 1.33 162 1 .02 0.87 1 .50 0.15 1.25 16 3 1.05 1.G1 1.74 0.04 0.33 167 1.34 1.31 2.25 0.0 3 0.25 168 1.63 1.3G 2.24 C.33 2. 75 170 1.37 1.31 2 .25 0.06 0.5C 17 1 1.54 1. 29 2.22 0.2.5 2.08 183 1.45 1.27 2.18 G.18 1.50 184 1.38 1.25 2.15 0.13 1.08 186 1 .30 1.15 1 .98 0.15 1.25 19C 1.27 1.20 2 .06 0.07 0.58 193 1.54 1.45 2.49 C. 09 0.75 196 1.57 1 .30 2 .24 G.27 2.25 197 0.98 C.95 1.63 0.03 0.25 2CC 1.64 1.47 2 . 53 C. 17 1.42 202 1 .70 1.46 2.51 C.34 2.83 204 1 .4 8 1.43 2 .46 G.05 0.42 2C9 1.30 1.13 1 .94 0.17 1.42 212 1.49 1.30 2.24 0. 10 0.83 213 1 .52 1.41 2 .43 0. 11 0.92 214 1.53 1.45 2.49 0.08 0.67 215 1.24 1. 03 1.7? 0. 21 1.75 219 1.27 0.98 1.69 C.29 2.42 22C 0.95 0.89 1 .53 0.06 C.5C 221 1.55 1.21 2.08 0.34 2.83 222 1.47 1 .4C 2.41 C. 07 0.58 223 1.65 1.54 2 .65 0.11 0.92 225 1.70 1.74 2.99 0.04 0.33 227 0.52 G.48 0.83 G.04 0.33 229 1 .09 0.96 1.65 0.13 1.08 23C 1.0 6 NC C ATA 231 . 1.54 1.41 2 .43 0.13 1.08 23 2 1.48 1.36 2.34 C.12 1.00 234 1 .06 0.85 1 .46 0.21 1.75 231 236 1 .28 1.06 1 .82 0.22 1.83 238 0.78 C.61 1 .05 0.17 1.42 251 1.63 1.44 2.4 8 0.19 1.58 25 3 1 .08 1.0 1 1.74 C..07 0.58 254 1.80 1.5 3 2 .63 0.27 3 .08 25 5 1 .43 1.40 2.41 C.03 0.25 257 1 .57 1.49 2.56 G. 08 0.67 259 1 .63 1.58 2.72 G.05 0.42 261 1.61 1.49 2.56 0. 12 1.00 262 1.46 1.43 2.46 C.03 0.25 263 0.90 0.88 1 .51 G.02 0. 17 264 1.31 1. 18 2 .03 0.13 1.08 265 0.99 0.93 1.6C C.06 0.50 267 1 .47 1.43 2.46 C. 04 0.33 268 1.16 1. 04 1.79 0.12 l.CC 269 1. 50 0. 89 1 .53 0.61 5 .08 28C 1.79 1.46 2.51 0.33 2.70 282 2 .00 1 .97 3.39 0.03 0.25 284 1.80 1.78 3.06 0.02 0.17 286 0.58 0. 58 1.00 C.00 C O O 287 1 .76 1.42 2.44 0. 34 2.83 289 1 .73 1.65 2 .84 0.08 0.67 291 1.45 1.28 2 .20 0.17 1.42 293 1 .72 1.61 2.77 0. 11 0. 92 295 0 .85 0.62 1 .06 0.23 1.92 2 97 1. 50 1.44 2 .48 0.06 0.50 299 1.22 0.99 1.70 0.2 3 2. 17 301 1 .47 1.21 2.08 G.26 2. 17 302 1 .41 1.27 2.18 0.14 1. 17 3C3 1 .64 1.54 2.65 C.10 0.83 305 1.80 1.74 2.99 C.06 0.5 0 3C9 1 .44 1.42 2 .44 0.O2 0.17 311 1.88 1.80 3.10 0.08 0.67 313 1.48 1.22 2 .IC C.26 2. 17 315 0 .90 0.84 1.44 C.06 C.5C 317 2.00 1.88 3.23 0.12 1.00 321 1.99 1-75 3.01 G.24 2.GO 3 26 1.4 5 1.34 2.30 0.11 0.92 328 1 .31 1.23 2 .12 G.08 0.67 329 1.85 1.84 3.16 0.01 0.08 23 C 1.86 1.48 2.5 5 C.38 3. 17 331 1 .29 1 .00 1.7 2 0.29 2.42 332 1.43 1. 14 1 .96 0. 29 2.42 335 1.82 1.47 2 . 53 0.35 2.92 336 1 .84 1.40 2.41 0.44 3.67 337 1 .03 0.88 1.51 0. 15 1.25 34C 1.44 1.31 2.25 0.13 1.08 341 1 .13 1. C4 1 .79 C.09 0.75 342 1 .36 1. 14 1 .96 0.12 1. CC 345 2.10 1.92 3.30 0.18 1.50 347 1.56 1. 47 2. 53 C.09 0.75 349 2.01 1.8 1 3.11 C.20 1.67 35C 1.78 1.73 2.98 G.05 0.42 351 0.43 0.35 0.60 C.08 0.67 232 FRIU 0.86 C.59 1.01 G.27 2. 25 FR2U 0.93 0.62 1 .07 C. 31 2. 58 FR3U 0.71 0.50 0.86 G. 20 I . 75 *28C 1.79 1.46 2.51 0.33 2. 70 *28GA 1.53 1.19 2.0 5 C.34 2. 78 *28GE 1.57 1.19 2.0 5 0.38 3 . 17 *28CC 1.56 1.23 2.12 0.33 2. 67 *28CC 1.51 1.19 2.05 0.32 2. 67 •28 0 1.79 1.12 1.93 C.67 5 . 54 '28CA 1.53 C.87 1 .50 G.66 5. 46 '2.8CB 1.57 G.66 1 .14 0.91 . 7 . 59 '28CC 1.56 C.63 l . C f i C.93 7. 75 •28CC 1.51 NO DATA PERCENT ORGANIC CARBON AVERAGE RANGE GULF OF CALIFORNIA SLCPE 3 .60 0 .8 -7 .4 BAS INS 2.5 5 C . 4 - 4 . G GULF OF PAR IA 0.71 C. 1-1.4 NISSISSIPPI DELTA 0.61 0. 1-1.3 ARANSAS BAY, TEXAS 1 .2 6 0 .61 -1 .7 SAN ANTONIO BAY* TEXAS 0.82 0. 3 -2 .7 CALIFORNIA OFFSHORE BASINS 4.32 GULF OF MEXICC SHELF 0.36 SLOPE 0.82 SIGSBEE DEEP 0 .47 AEI.CJAN LAGOON* V»EST AFRICA 6.43 4. 5-12.8 £RCACHCN BASIN* FRANCE 2.07 0 . 3 - 5 . 2 BALTIC SEA 2.55 2 .3 -4 .8 BENGAL SHELF 0.77 C. 2-1.6 PERU-CHILE TRENCH BASIN 0 .67 0 . 1 - 0 . 9 SLOPE 1.92 C . 3 - 9 . 6 FROM VAN ANDEL (1964 , TAELE X, P.259 ) . TABLE XI: CARECN CCNTENTS OF GECRGIA STPAIT AND FRASER RIVER SAMPLES. SUBSAMPLES OF « 2 8 0 WERE ANALYSED AFTER TREATFEr-TS WITH HCL (NARKED TO REMOVE CARBONATE, AND HYCPCGEN PEROXIDE (MARKED ») TO REMOVE ORGANIC MATTER. 233 samples was regarded as acceptable for t h i s study, and i n fa c t most duplicates gave results, that agreed within ±0.05%. High, p r e c i s i o n overlooks- the f a c t that the subsample analysed weighs only 0.5 gm. , which i s assumed to be representative of a grab-bucket-full of sediment that i t s e l f i s supposedly representative of a large area of sea-floor. Averages of the d u p l i c a t e values are presented i n Table XI, which also includes some average values f o r Recent marine sediments f o r comparison (from Van Andel, 1964, Table X, p.259). One sample, number 280, was divided into f i v e subsamples each of which was further s p l i t into three. T o t a l carbon content was measured on one of the three from each subsample, the other two being treated with e i t h e r hydrogen peroxide (to oxidise organic matter) or 5% HCl (to d i s s o l v e carbonate). Results are included i n Table XI. More consistent r e s u l t s are obtained with the HCl treatment than with peroxide; the l a t t e r does not appear to be as e f f i c i e n t at o x i d i s i n g organic matter as HCl i s at removing carbonates. 5.2.2 DISCUSSION The organic carbon content of the Georgia S t r a i t sediments averages 1.08% (corresponding to an organic matter content of 1.86%: organic matter = 1.72x % organic carbon Kemp and Lewis, 1968; see also Trask, 1939; Emery, 1960), with values ranging between 0.07% and 1.97% (0.12% to 3.39% organic matter). These values are very low compared to those from the sediments i n the basins off the C a l i f o r n i a coast (Emery, 1960), and low. even when compared to the carbon content of B a l t i c Sea sediments (Van Andel, 1964, Table X, p.259). Average values of organic carbon from the M i s s i s s i p p i Delta are lower than those from Georgia S t r a i t (Van Andel, ibid..), -wh±eh_inay r e f l e c t a r e l a t i o n s h i p between sedimentation r a t e and carbon content such, as that discussed by Emery (1960). Too high-a r a t e of deposition of terrigenous material d i l u t e s the organic content, while sedimentation rates that are too low generally permit oxidation and consequent loss of organic matter before It can be protected by b u r i a l . Carbonate carbon averages 0.23% (a c a l c i t e equivalent of 1.92% assuming a l l the carbonate i s present as c a l c i t e : c a l c i t e % = 8.33 x % carbonate carbon), varying between 0% and 1.75% (0% to 14.51% c a l c i t e ) . Coarse carbonate debris, either whole or coarse sand-size fragments of s k e l e t a l material, was not included i n t h i s analysis. The average carbonate content, expressed as c a l c i t e , for the Fraser River samples i s 2.19%, while the average value f o r organic carbon .(organic matter) i s 0.57 (0.98)%. The d i s t r i b u t i o n of carbonate-carbon values i n the S t r a i t of Georgia does'not show a regular pattern. Generally, there i s a concen-t r a t i o n of the highest values southeast of a l i n e between Point Roberts and the southeastern end of Mayne Island. This coincides f a i r l y c l o s e l y with the sandier, r e l i c t sediments of Roberts Swell and Boundary Basin, where a f a i r l y abundant fauna including molluscs, echinoids, bryozoans and s o l i t a r y corals occurs. Intermediate values (0.25 to 0.75%) also occur i n t h i s area, and i n a broad band north, southwest and south of Sand Heads. Isolated groups of samples with intermediate values occur throughout the northwestern portion of the S t r a i t . A b e l t of low values (0.1 to 0.25%) separates the Roberts Swell and Fraser Delta areas, and low values occur over most of the rest of the S t r a i t northwest of the delta. Very low contents of carbonate-carbon (less than 0.1%) are 235 • •• • • • •••••• • • • • • • • •••• a • • • •• % • • * ' . • • 0 20 40 60 80 100 Percent clay FIGURE 63? Relationship between organic carbon and clay content for Strait of Georgia and Fraser River M sediments. 236 scattered throughout tha S t r a i t northwest of Point Roberts. Very low values for organic carbon (less than 0.5%) occupy a broad, hour-glass shaped zone that trends south-southeast from Sand Heads but does not reach Boundary Basin. Low values (0.5 to 1.0%) occur along the d e l t a front from Sand Heads to Point Grey, south of a l i n e between Sand Heads and P o r l i e r Pass, i n i s o l a t e d patches around the margins of the S t r a i t , and i n l o c a l areas associated with ridge tops. Intermediate concentrations of organic carbon (1.0 to 1.5%) occur throughout most of the S t r a i t northwest of Sand Heads except for i s o l a t e d areas with high organic carbon contents (greater than 1.5%) that are associated with the c l a y - r i c h sediments of the deep basins, Ballenas and Malaspina. Reference has already been made to the r e s u l t s of a c o r r e l a t i o n and regression analysis conducted on Group A samples i n which % clay and % organic carbon were included as v a r i a b l e s . In the three cases described (also Table X) the c o r r e l a t i o n between organic carbon and clay content i s high. When a l l analysed samples (N=146) are included i n a c o r r e l a t i o n matrix and regression analysis the c o r r e l a t i o n i s 0.788, which i s s i g n i f i c a n t at the 1% l e v e l (see also Figure 63). A s i m i l a r l y high, p o s i t i v e c o r r e l a t i o n between organic carbon and clay contents has been noted by many workers (e.g. Van Andel, 1964; Thomas, 1969; Kemp, 1969, 1971; Thomas et a l . , 1972) which suggests that the organic matter i s either fine—grained or, moreJlikely, i s adsorbed as non—particulate, molecular material onto the clay minerals (Hahn and Stumm, 1970). 5.3 MANGANESE NODULES To date, manganese nodules have been recorded from only one other l o c a l i t y i n B r i t i s h Columbia's coastal waters ( G r i l l et a l . , 237 1968a, b). Manganese nodules are of value i n the present thesis i n so far as t h e i r existence Implies c e r t a i n r e s t r i c t i o n s on chemical and phy s i c a l conditions f o r l o c a l i s e d areas i n the S t r a i t . Of primary importance i s the implication of low sedimentation rates required for nodule growth and preservation. I t i s not proposed to attempt either a review of published information on sea-floor manganese nodules (see for further refernces Mero, 1964; Bonatti and Nayudu, 1965; Chester, 1965; Degens, 1965) or any sophisticated chemical i n t e r p r e t a t i o n s (see Bender, Ku and Broecker, 1966; E l d e r f i e l d , 1972). Manganese crusts and stains on pebbles and i n sponge skeletons have been referred to and described i n e a r l i e r sections; only the nodules w i l l be discussed here. 5.3.1 LOCALITIES Two s i t e s are known where well-developed nodules occur. One of these was a dredge haul c o l l e c t e d i n July, 1968, from the CSS VECTOR by Dr J.W. Murray, Geology Department, U.B.C. The dredge s i t e was located at l a t i t u d e 49°21.8'N, longitude 124°02.0'W, on the southwest side of Sangster Ridge i n approximately 300 metres of water. From other evidence i n the dredge haul, and from seismic studies, t h i s ridge has been interpreted as of Pleistocene age and morainal o r i g i n ( T i f f i n , 1969). The second l o c a l i t y , 70-1-341, i s at 49°21.7'N, 124°09.1'W, at 326 metres depth on the eastern side of the low c o l connecting Sangster Ridge to the Ballenas Islands. Samples from t h i s l o c a l i t y were c o l l e c t e d with a Peterson grab sampler. In neither case i s the area over which the nodules occur f u l l y known, but samples without nodules were co l l e c t e d nearby suggesting the areas of nodule occurrence are small. 238 5.3.2 MORPHOLOGY Sample material from Sangster Ridge includes one large, d i s c o i d a l nodule, one pebble completely en c i r c l e d by a narrow, raised band of accretionary ferromanganese material, two nodule fragments, and a small patch of ferromanganese material on a q u a r t z - d i o r i t e cobble. The specxmenss from l o c a l i t y 341 include one broken and four e n t i r e nodules s t i l l with, pebble n u c l e i , seven separate fragments of concavo-convex d i s c o i d a l rims without-"nuclei but showing the imprint of the pebble, and some sponge skeletons containing a brown, earthy material that gave a p o s i t i v e test f o r manganese when fused with sodium carbonate (Berry and Mason, 1959, p.266). Nodules from both l o c a l i t i e s are d i s c o i d a l , and always have a pebble as t h e i r nucleus. Their shape i s usually concavo-convex, and the occurrence of cor a l s , sponge bases, bryozoa and rare worm tubes on the convex sides suggest that they probably rested on the bottom with t h i s surface uppermost. In a l l specimens except one the pebble was s t i l l v i s i b l e i n the centre even when the d i s c o i d a l rim had grown 0.3 to 0.5 cm. above the pebble surface. One nodule showed onlyr.a shallow depression i n the upper surface above the pebble. The largest nodule from the Sangster Ridge dredge haul and some fragments from l o c a l i t y 341 possessed a second, l e s s well-developed, bench on top of the main nodular mass (Figure 64 a). In t e r n a l l y , the nodules are c o n c e n t r i c a l l y laminated, with t h i n laminae which are c l o s e l y spaced p a r a l l e l to the upper and lower surfaces, but wider and thicker around the curved rim of the d i s c . A t h i n l i m o n i t i c skin i s often developed on the lower surface. FIGURE 64: Manganese nodules c o l l e c t e d from (A) S a n g s t e r Ridge, and (B) sample s i t e 70-1-341. 240 The largest nodule, from Sangster Ridge, while not t r u l y c i r c u l a r i n o u t l i n e , has a maximum diameter of 13.5 cm. It i s 2.5 cm. t h i c k from the lower surface of the main nodule mass to the top of the upper bench. Radial width of manganese accumulation around the pebble nucleus averages about 3 cm., with a maximum of 4.5 cm. Fragments of d i s c o i d a l nodules from s i t e 341, s t i l l bearing the imprint of the pebble nucleus, range between 3 and 5.5 cm. i n width from pebble imprint to nodule rim. Surface textures range from almost smooth, p a r t i c u l a r l y on undersurfaces, to l o c a l small areas that are f i n e l y b o t r y o i d a l . The l a t t e r texture covered the e n t i r e upper surface of two nodules from s i t e 341. 5.3.3 CHEMICAL ANALYSES Four samples were sent to Mr S. Holland, Minera l o g i c a l Branch, Department of Mines and Petroleum Resources, V i c t o r i a , B.C., for semi-quantitative spectrochemical analysis f o r several elements and assays of manganese, i r o n , cobalt and n i c k e l . Results are given i n Table XII, which also includes the analysis of a manganese nodule from J e r v i s Inlet c o l l e c t e d by Dr J.W. Murray, Geology Department, U.B.C, and analysed i n the same laboratory. The analyses represent average compositions over the width of nodules from which the samples were taken. The samples were: . A: three fragments representing a wedge broken o f f the large Sangster Ridge nodule. It extends from nucleus i to outer margin; B: two nodule fragments from Sangster Ridge; C: l a r g e fragment of a nodule from l o c a l i t y 341; D: large fragment of a nodule from l o c a l i t y 341, s i m i l a r 241 EL. A B C D JERVIS S i >10 >10 >5 >5 A l 0 . 3 - 3 1 - 9 0 . 2 3 - 2 . 1 0 . 1 7 - 1 .5 1 - 9 Mg 0 . 5 - 4 . 5 1 - 9 0 . 4 2 - 3 . 7 5 0 . 3 - 3 0 . 2 5 - 2 . 2 5 Ca 0 . 0 7 - 0 . 6 0 . 2 2 - 1 . 9 5 0 . 0 3 - 0 . 3 0 . 0 1 7 - 0 . 1 5 0 . 4 5 - 4 . 0 5 P 0 . 0 2 - 0 . 1 8 0 . 0 2 7 - 0 . 2 4 N . D . N . D . Fe 2 . 2 - 1 9 . 5 2 . 1 7 - 1 9 . 5 0 . 7 - 6 0 . 5 - 4 . 5 4 - 3 6 Pb 0 . 0 5 - 0 . 4 5 0 . 0 3 - 0 . 3 0 . 0 1 7 - 0 . 1 5 0 . 0 0 3 - 0 . 0 3 <0 .1 Cu 0 . 0 1 3 - 0 . 1 2 0 . 0 0 7 - 0 . 0 6 0 . 0 0 3 - 0 . 0 3 0 . 0 0 1 7 - 0 . 0 1 5 Zn 0 . 0 0 3 - 0 . 0 3 C . 0 0 1 3 - 0 . 0 1 2 0 . 0 G 0 3 - O . 0 0 3 0 . 0 Q C 3 - 0 . 0 0 3 -Mn >10 >10 >1.0 >10 >5 Ag T R A C E T R A C E T R A C E N . D . N . D . V 0 . 0 0 5 - 0 . 0 4 5 0 . 0 0 5 - 0 . 0 4 5 0 . 0 0 4 - 0 . 0 3 6 0 . 0 C 1 7 - 0 . 0 1 5 0 . 0 0 7 - 0 . 0 6 T i 0 . 0 1 7 - 0 . 1 5 0 . 0 5 - 0 . 4 5 0 . 0 1 - 0 . 0 9 0 . 0 0 5 - 0 . 0 4 5 0 . 0 1 7 - 0 . 1 5 N i 0 . 0 0 5 - 0 . 0 4 5 0 . 0 0 3 - 0 . 0 3 0 . C C 3 - 0 . 0 3 0 . 0 0 2 7 - 0 . 0 2 4 0 . 0 0 7 - 0 . 0 6 Co 0 . 0 1 - 0 . 0 9 0 . 0 1 2 - 0 . 1 0 5 0 . 0 0 3 - 0 . 0 3 0 . 0 0 2 3 - 0 . 0 2 1 0 . 0 0 3 - 0 . 0 3 Na >2 >,2 >2 >2 >2 K 0 . 4 2 - 3 . 7 5 0 . 4 2 - 3 . 7 5 0 . 3 - 3 0 . 3 - 3 0 . 4 5 - 4 . 0 5 Sr 0 . 0 0 7 - 0 ^ 0 6 0 . 0 2 - 0 . 1 8 0 . 0 0 7 - 0 . 0 6 0 . 0 0 7 - 0 . 0 6 0 . 0 1 7 - 0 . 1 5 Cr 0 . 0 0 3 - 0 . 0 3 0 . 0 0 3 - 0 . 0 3 0 . 0 0 3 - 0 . 0 3 0 . 0 0 3 - 0 . 0 3 Ba 0 . 0 2 7 - 0 . 2 4 0 . 0 7 - 0 . 6 0 . 0 2 3 - 0 . 2 1 0 . 0 1 7 - 0 . 1 5 0 . 0 7 - 0 . 6 Mo 0 . 0 0 3 - 0 . 0 3 0 . 0 0 2 - 0 . 0 1 8 0 . C C 3 - 0 . 0 3 0 . 0 0 1 7 - 0 . 0 1 5 0 . 0 1 3 - 0 . 12 A S S A Y S Mn 2 2 . 7 8 21 . 31 3 2 . 7 5 3 1 . 9 7 2 8 . 6 5 Fe 9 . 2 5 9 . 5 0 3 . 4 1 3 . 0 0 Co 0 . 0 3 5 G . 0 4 1 0 . 0 1 1 0 . 0 1 0 0 . 0 1 N i 0 . 0 3 0 . 0 2 1 0 . 0 1 9 G . 0 1 8 0 . 0 2 Mn/Fe 2 . 4 6 2 . 2 4 9 . 6 0 1 0 . 6 6 0 . 0 4 0 . 0 2 T R A C E Q U A N T I T I E S O F : S B , A S , G A , S B , A S , G A , G A , Z R , B . GA , Z R , B . C U , Z R , CR Z R , 8 . Z R , 8 . T A B L E X I I S E M I - Q U A N T I T A T I V E SPEC TROCHE M I C A L A N A L Y S E S AND A S S A Y S OF G E O R G I A S T R A I T I A , B , C , AND D: SEE T E X T ) AND J E R V I S I N L E T MANGANESE N O D U L E S . A N A L Y S E S BY M I N E R A L O G I C A L L A B O R A T O R Y , D E P T OF M I N E S AND P E T R O L E U M R E S O U R C E S , V I C T O R I A , B . C . 242 to but not part of the same nodule as C. 5.3.4 DISCUSSION Detailed chemical analyses of manganese nodules from J e r v l s Inlet have been presented by G r i l l et a l . 0-966a, b). X-ray d i f f r a c t i o n data suggested that the dominant manganese mineral i n these nodules was todorokite, which i s also believed to be the dominant mineral i n the S t r a i t of Georgia nodules. I d e n t i f i c a t i o n i n the l a t t e r instance i s based on r e l a t i v e l y poor q u a l i t y X-ray diffractograms, with no chemical compositional data to substantiate i t . In physical appearance the d i s c o i d a l nodules from J e r v i s Inlet are quite s i m i l a r to those from the S t r a i t of Georgia. Both the J e r v i s Inlet and Georgia S t r a i t nodules have r e l a t i v e l y high manganese and low i r o n contents which r e l a t e s them to Mero's B regions that occur close to the North and South American coasts. Mero (1964) believes the nodules i n these regions may have formed r e l a t i v e l y r a p i d l y , at least when compared to the rates of formation of deep-sea nodules. From the l o c a t i o n of the J e r v i s Inlet nodules on a submarine ridge that was believed to have been formed during the Sumas Stade of the Fraser River G l a c i a t i o n , G r i l l et a l . (1968b) concluded that they could be no older than 12,000 years. If t h i s maximum age i s accepted for the S t r a i t of Georgia nodules also, the minimum accumulation rate for the large Sangster Ridge nodule would be 0.004 mm./year, considerably greater than some rates quoted by Mero (1964, p.154) for deep-sea nodules of 1 mm./lOOO years or 1 mm./100,000 years. For nodules, to s t i l l e x i s t on or close to the sea-bottom, or at least within easy reach..of a small grab-sampler, sedimentation 243 rates must be low. Manganese does occur i n considerable concentrations i n the sediments from some places i n the S t r a i t without the presence of nodules (see Table IX: sample 280 has an oxalate—extractable manganese content of 3,408 ppm.). Sedimentation rates calculated for Ballenas Basin, where sample 280 Is located, range from 0.55 to 2 cm./year (see section 3.13). Ballenas Basin i s also believed to be a reducing environment which tends to prevent the p r e c i p i t a t i o n of manganese as i n s o l u b l e oxides i n nodular accretions. 244 CHAPTER 6 SUMMARY AND CONCLUSIONS 1. The modern sediments In the S t r a i t of Georgia have the Fraser River as t h e i r p r i n c i p a l source. Sediment c a r r i e d by the Fraser i s medium to f i n e sand s i z e and f i n e r , and the bulk of i t i s added during the spring and summer freshet. 2. S t r a i t of Georgia sediments are of two kinds: those r e l a t e d to the modern delta and to modern sedimentation, which are f i n e to very f i n e sands, s i l t s , and clays; and those that are r e l a t e d to older d e l t a i c or to Pleistocene g l a c i a l and i n t e r g l a c i a l deposition, which are mostly coarser, more poorly sorted, sands and angular gravels. 3. Despite the problems inherent i n the granulometric analysis of fine-grained sediments, the r e s u l t s make some sense sedimentologically. Isopleths of meanr'and median g r a i n - s i z e i n d i c a t e that sediments become f i n e r to the west and northwest away from the d e l t a , northwestwards along the axis of the S t r a i t , and, i n a more compressed way, basinwards from the margins. D i s t r i b u t i o n of the sand-content isopleths r e f l e c t s both the predominance of sub-sand-size sediment i n the S t r a i t as well as the concentration of sandy material i n the area to the southeast of the d e l t a where erosion i s believed to be a c t i v e . Textural f a c i e s maps present much the same p i c t u r e . The U-shaped bend i n the isopleths and boundaries, of the various parameters between Galiano Island and the d e l t a could be the r e s u l t of any one or a combination of the following: a) An older d e l t a grew from the. southeast along the axis of the S t r a i t , extending i t s bottomset.beds northwestwards into Ballenas Basin. The old foreset beds now form the feature c a l l e d Roberts Swell. A change i n the sedimentation pattern r e s u l t i n g from d i v e r s i o n of the Fraser to i t s present course resulted i n the d e l t a growing into the S t r a i t from the side, with, i t s bottomset then foreset beds overlapping the old d e l t a as i t advanced. This modified the pattern of the parameters measured. b) The pattern i s r e l a t e d to present d e l t a sedimentation and i s due to a southward movement of bed load on the ebb t i d e (after Mathews and Shepard, 1962). c) It i s the r e s u l t of redeposition of material winnowed from Roberts Swell and transported northward i n t o deeper water (after T i f f i n , 1969). T i f f i n suspects that t h i s mechanism i s more p l a u s i b l e than the preceding one to explain the high concentration of sand south of the Fraser River mouth and over the northwestern edge of Roberts Swell. In a l l cases the western limb of the U i s explained by a l o c a l or r e l i c t source of coarser sediment on the western side of the S t r a i t . I t seems quite l i k e l y that a l l three mechanisms are intermixed, and the U-shape of the feature i s a composite expression of t h i s . 4. Bed load sediment (the coarser of the f i n e sands) i s deposited on the d e l t a front and subsequently moved northwards under the influence of the continuous longshore currents.. During the freshet some sediment may, e s p e c i a l l y on an ebb t i d e , be moved basinwards of t h i s influence and be deposited to the south of Sand Heads. The suspended load, on 246 being c a r r i e d into the S t r a i t , comes under the influence of t i d a l and more per s i s t e n t currents. Lt i s moved northwards along with the surface-water c i r c u l a t i o n , becoming enmeshed i n a clockwise eddy of the surface water i n the S t r a i t . Deeper water, however, tends to be more constantly north-flowing. The suspended sediment must also come under the e l e c t r o -l y t i c influence of the s a l t water, causing f l o c c u l a t i o n of clay minerals. 5. Main dep o s i t i o n a l areas f o r the sediments are: a) the d e l t a , west and north of Sand Heads. Sediments deposited here are r e d i s t r i b u t e d by longshore currents, b) lower d e l t a slopes and the eastern ends of the northern basins, e s p e c i a l l y Ballenas Basin, where Recent sediment thicknesses are i n excess of 180 metres at a distance of 50 km from the Fraser River. The eastern end of Sechelt basin also has a thick sediment f i l l . Recent sediments cover the eastern ends of the ridges along the mainland coast north of Burrard I n l e t , but further to the northwest they t h i n r a p i d l y to become only l o c a l i s e d concentrations, with Pleistocene sands and gravels s t i l l exposed on the ridge c r e s t s . Ridge flanks often have l i t t l e thickness of Recent sediment cover, and i t i s pos s i b l e that currents are of s u f f i c i e n t strength to keep them sediment-free . Current v e l o c i t i e s are poorly known for the S t r a i t north of the d e l t a , e s p e c i a l l y at depth. On the Vancouver Island shelf and slope, Recent sediments are t h i n , except where confined i n l o c a l pockets behind small ridges on the slope. 6. South of Sand Heads i s an area of coarser sands and gravels 247 suggesting a zone of erosion or winnowing of an older sedimentary feature that may have been an old de l t a of the Fraser. The high t i d a l current v e l o c i t i e s , even near the bottom i n t h i s area may be, and have been, sweeping sand from and across Roberts Swell to the northwest, to be deposited i n deeper water south of Sand Heads, or to the southeast or east into Boundary Basin to be removed from the S t r a i t through Boundary Pass. 7. Only r e l a t i v e l y small quantities of sediment are derived l o c a l l y around the margins of:the S t r a i t . Sands and gravels occur around the eastern and western margins of the S t r a i t , the coarse f r a c t i o n of the sediment being derived either l o c a l l y or from Pleistocene deposition. There i s l i t t l e basinward movement of t h i s material. Some mud, presumably re l a t e d to the modern sedimentary regime, i s admixed with the coarser d e t r i t u s . It i s impossible to decipher the o r i g i n of the s i l t - and c l a y - s i z e f r a c t i o n s on mineralogical grounds since the mineral composition of these f r a c t i o n s i s p r a c t i c a l l y uniform over the en t i r e S t r a i t . 8. The ridges i n the northwest, on the eastern side of the S t r a i t , are composed of gravels plus mud. They do not appear to be supplying sediment l o c a l l y excep1tj.f<or sp.ongenf.ragmehtsn r.These ;r.ldges.c-arie-,.composed of Pleistocene sediments, probably modified by reworking during lower stands of s e a - l e v e l , now. remaining as: r e l i c t deposits. They are the s i t e s of l i t t l e , i f any, accumulation of modern muddy sediment. 9. The deep basins are the s i t e s of very t h i c k accumulations of very 248 fine-grained sediments. Two depositional processes seem to be a c t i v e over the basins: a) s e t t l i n g of f i n e sediment, mainly c l a y s , from suspension; and b) some form of mass transport of sediment down the basin axes.. The form t h i s l a s t process, takes i s not known for c e r t a i n , however the seismic and echo—sounding p r o f i l e s of T i f f i n (.1969) and Cockbain (1963a) r e s p e c t i v e l y , showed sub-bottom r e f l e c t o r s whose c h a r a c t e r i s t i c s o f - f a d i n g e r e f l e c t i n g i n t e n s i t i e s , and thinning, could be explained by invoking t u r b i d i t y currents as the mechanism. Sedi-mentation rates i n these areas are very high, and the cores taken repre-sent only a r e l a t i v e l y very short i n t e r v a l of the t o t a l sedimentary h i s t o r y . Existence of t u r b i d i t y currents a c t i v e only recently cannot be discounted, and i t i s p o s s i b l e that the t u r b i d i t y currents were composed of material that was already f a i r l y well-sorted, and of s i m i l a r mean g r a i n - s i z e to the sediment i n the area i n which they came to r e s t . I f so, v i s i b l e textured expression of the t u r b i d i t e would not e x i s t . 10. Inspection of cumulative p r o b a b i l i t y curves of sediment s i z e -frequency data l e d to a possible explanation of t h e i r non-linear shape i n the sub-sand-size region. The s i l t - s i z e material i s composed of grains of quartz and f e l s p a r , with some amphiboles and rare garnets, and subordinate amounts of p h y l l o s i l i c a t e s . The c l a y - s i z e f r a c t i o n s are dominated by p h y l l o s i l i c a t e s (montmorillonite, i l l i t e , c h l o r i t e , minor mixed-layer phases and k a o l i n i t e ) , although quartz and f e l s p a r are s t i l l present. Equant grains and p l a t y minerals react d i f f e r e n t l y i n a f l u i d medium but, If small enough, even equant grains w i l l be affected by e l e c t r i c a l forces as a r e s u l t of a greater number of broken bonds per unit volume than i n the coarser/sizes (see also C a r r o l l , 1959). 249 When the mean s i z e is: larger (In the s i l t range) the curve often has a pronounced bend, while f i n e r (clay—size) samples tend to approach a s t r a i g h t l i n e . This can be Interpreted as a r e s u l t of the coarse sediments containing a greater amount of suspended material that act and s e t t l e as independent grains. The f i n e r samples have les s of t h i s material,.;and more of the t o t a l mineralogy i s p l a t y . Hence not only the shape of the cumulative p r o b a b i l i t y curves but also the change from Factor I to Factor II and at least part of the sediment d i s t r i b u t i o n can a l l be explained m i n e r a l o g i c a l l y . 11. Recent current studies i n the S t r a i t of Georgia have suggested the existence In the upper 50 metres of the S t r a i t of a clockwise eddy whose extent and development have not yet been established. This eddy seems to have expression i n the sediments as the region of mud which corres-ponds to the zone of heaviest pro-delta sedimentation. Clays are d i s t r i -buted to the northwest by slower moving, deeper currents. That not much sediment, even clay, i s s e t t l i n g on ridges i n the far northwest of the area i s indicated by unburied, r e l i c t , Pleistocene gravels, and manganese nodules, on Sangster Ridge and on the low saddle connecting Sangster Ridge to the platform from which Ballenas Islands r i s e . The existence i n these areas of currents of s u f f i c i e n t strength to keep the ridges swept c l e a r of s e t t l i n g sediment i s believed' to be responsible for this s i t u a t i o n . 12. D i r e c t measurement of currents i n any body of water i s influenced by short-term e f f e c t s and v a r i a t i o n s that may mask net current movements. V a r i a b i l i t y of current movements i n the S t r a i t of Georgia on a short-term basis , r e f l e c t i n g changes i n wind speed and d i r e c t i o n , t i d a l e f f e c t s , 250 r i v e r discharge, etc. are a l l evident i n the studies of Huggett (1966) and Giovando and Tabata C1970). Study of sediment d i s t r i b u t i o n and d i s p e r s a l patterns reveals the consequences of long—term, net e f f e c t s of current movements and sediment transport. 13. The d i s t r i b u t i o n pattern of sediments i n the S t r a i t of Georgia has i n t e r e s t i n g palaeogeographic implications. If a l l that was a v a i l a b l e f o r study was a section of i n t e r m i t t e n t l y exposed outcrops or a s e r i e s of d r i l l cores along the length of the S t r a i t , and assuming the f a c i e s and mineralogy were the same as they are now, i t would be impossible to detect the presence of land to the west (Vancouver Island). Also, the impression gained from study of the s a n d : s i l t : c l a y f a c i e s maps, or mean g r a i n - s i z e changes along the length of the S t r a i t , i s that the source lay to the southeast, since d i r e c t i o n of f i n i n g of sediment i s from southeast to northwest. The i n t e r p r e t a t i o n would be that transport of sediment was l o n g i t u d i n a l down the axis of the S t r a i t , whereas i n fact the source i s on one side and transport i s at f i r s t l a t e r a l , then l o n g i t u d i n a l . If the Roberts Swell sediments were interpreted as old d e l t a deposits, the f i n a l analysis would be that the r i v e r supplying the S t r a i t flowed i n t o i t from the southeast. 251 REFERENCES Ahmad, N., 1955, Investigation of some physical and chemical properties of the stony marine clays i n the Fraser V a l l e y area of B r i t i s h Columbia: Unpubl. M.S.A. Thesis, Dept of Soil Science, University of British Columbia. Andrews, R.W., Jackson, M.L., and Wada, K., 1960, I n t e r s a l t a t i o n as a technique f o r d i f f e r e n t i a t i o n of k a o l i n i t e from c h l o r i t i c minerals by X-ray d i f f r a c t i o n : Soil Sci. Soc. America Proc, v.24, p.422-424. 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K ' 101626 221 2. 58. 23. 16. 1.5 201. 3. 6 4. 8 2.99 . 65 1.58 . 61 131742 223 44. 34. 13. 9. 3.5 214. 0. 7 • • • • • 191900 288 2. 5 3. 26. 20. 1. 2 146. 3. 6 4. 5 3.7 2 .44 .87 .46 211909 33 7 93. 4. 3. 13.2 27. 2.0 2. 0 .98 .17 1.82 . 64 231909 402 60. 25. 15. 1.5 49. 3. 6 4. 8 2.38 . 83 1.58 . 61 251912 4 82 35. 4 5. 1 9. 0.6 27. 4. 8 5. 7 2.36 .56 1.24 . 55 401741 268 4. 60. 24. 13. 1.8 194. 2. 9 3. 7 3.37 .41 1.31 . 56 421722 3 42 15. 38. 30. 17. 1.4 201. 3. 8 3. 7 4.7 3 .01 1.29 . 56 441712 408 40. 40. 21. 0.7 130. 4. 8 5. 7 2.78 . 59 1. 14 . 53 451706 456 17. 57. 2 7. 0.2 77. 5. 8 6. 1 3.43 .54 1.27 . 55 461637 449 21. 48. 18. 13. 2.2 31. 1. 7 2. 2 4.51 .21 1.12 .52 48 16 32 345 70. 17. 14. 2.3 128. 3.4 4. 4 2.49 .73 1.5 3 . 60 501628 268 7 3. 15. 11. 2.6 150. 3. 0 4. 0 2.39 . 76 1.94 . 65 531610 156 29. 40. 31. 0.4 104. 5. 8 6. 6 3.2 7 .42 .81 .44 541484 1 87 64. 18. 17. 1.8 132. 3. 6 5. 0 2.89 . 77 1.41 . 58 561494 255 71. 19. 11. 2.4 132. 3.5 4. 2 1.84 .91 2.09 . 67 581511 336 73. 17. 10. 2.7 115. 3. 4 4. 0 1.98 . 73 2.84 .73 601516 405 6 1. 23. 16. 1.6 104. 3. 8 4. 9 2.64 . 81 1.74 . 63 6 21523 461 68. 18. 13. 2. 1 69. 3. 2 4. 3 2. 49 . 76 .90 .43 731327 217 16. 41. 44. 0.2 77. 7.4 7. 4 3.23 .09 .88 .46 751340 255 31. 43. 26. 0.4 177. 5.0 6. 4 3.28 .68 1.04 . 50 761347 277 33. 42. 25. 0.5 168. 5. 1 6. 2 3.09 .59 .80 . 44 771361 308 33. 43. 25. 0.5 161. 5. 1 6. 2 2.73 . 60 .98 .49 791376 368 43. 36. 21. 0.8 146. 4.4 5. 7 2.93 . 75 1. 18 . 54 811389 425 69. 15. 16. 2.2 115. 2. 4 4. 1 3. 1 4 . 81 1.07 . 51 8 21395 447 100. • • 100.0 77. 1.8 1. 8 0.42 . 1 8 .33 . 24 831315 4 52 99. 1. • 99.0 86. 2. 2 2. 2 0.39 .04 1.06 .51 851299 400 55. 27. 1 8. 1.2 174. 3. 7 4. 9 3.06 . 64 1.01 . 50 861288 3 73 24. 52. 24. .3 187. 5.2 6. 3 3.0 6 . 72 1. 13 .53 871274 333 10. 59. 31. . 1 201. 6. 0 6. 9 3.09 .49 .94 .48 881267 299 17. 53. 30. .2 203. 5.9 6. 8 3. 17 . 50 .92 .47 891254 256 15. 52. 33. . 2 205. 6.4 7. 1 3.18 . 3 8 .90 .47 9 31112 217 11. 46. 25. 17. 1.3 79. 3. 6 4. 2 • • * • 961150 320 4. 56. 40. 0.0 282. 7. 1 7. 4 2.65 .21 .83 . 45 971159 341 5. 55. 41. 0. 1 282. 7.2 7. 9 3.1 3 .35 .90 .43 981170 379 3. 64. 33. 0.0 245. 6.4 7. 2 2.87 .47 .92 . 47 1001199 4 52 38. 37. 25. .6 196. 5.3 5. 8 3.37 .29 .85 .45 1021220 498 37. 48. 15. .6 79. 4.7 5. 4 2.34 .53 1. 15 . 53 1031182 543 24. 57. 19. .3 90. 5. 3 5. 7 2.51 .37 1. 11 .50 104 1171 622 5. 66. 29. . 1 79. 6.4 7. 0 2.42 .41 1.07 . 52 1061125 550 13. 63. 24. . 1 155. 5. 8 6. 4 2.6 1 .43 1. 12 .53 1081092 493 22. 52. 26. .3 241. 5.9 6. 6 3.09 .41 1.05 . 51 1091077 4 84 17. 53. 30. . 2 260. 6. 2 6. 8 3.0 1 .37 .97 .49 1111151 498 17. 60. 23. .2 170. 5. 6 6. 3 2.66 .46 1.09 . 52 1131119 446 14. 54. 32. .2 251. 6.4 6. 9 2.92 .32 .96 .49 1141104 433 7. 61. 33. . 1 267. 6.4 6.9 2.74 .41 .96 .49 1151028 393 2. 52. 46. 0.0 316. 7.6 7.8 2.55 . 1 9 .85 .46 1161051 360 • 48. 52. 0.0 33 3. 8. 1 8.7 2.79 .36 .97 .49 1181013 313 1. 46. 53. 0.0 223. 8.2 8.4 2.28 .13 .91 .47 119 986 2 73 17. 39. 43. .2 115. 7.3 7. 3 3.30 .03 .91 .47 121 979 290 3. 43. 55. 0.0 177. 8.4 8.4 2.54 .04 .99 .50 123 940 343 1. 49. 51. 0.0 289. 8. 1 8. 2 1.96 . 08 .94 .48 1241004 392 1. 49. 50. 0.0 278. 8.0 8. 2 2.35 .14 .94 .48 1251023 421 1. 53. 4 6. 0.0 326. 7. 8 8. 1 2.60 .24 .90 .47 1261034 4 63 3. 63. 34. 0.0 311 . 6.9 7.3 2.34 .31 .99 . 50 1271056 521 12. 55. 33. . 1 263. 6. 6 7. 1 3.07 . 2 7 1.05 . 51 1281066 556 6. 62. 3 1 . . 1 205. 6. 6 7. 1 2.64 .33 .99 . 50 1291075 580 6. 64. 30. . 1 163. 6.4 6. 9 2.60 .34 .93 .48 1301080 596 3. 63. 34. 0.0 168. 6. 8 7.3 2.53 .33 .75 .43 1311083 615 3. 63. 34. 0.0 216. 6. 8 7.3 2.51 .36 .99 .50 1321090 629 3. 61. 36. 0.0 199. 6. 8 7.3 2.47 .45 1.00 . 50 1331100 664 2. 61. 3 7. 0.0 170. 7. 0 7.5 2.41 . 37 .93 .48 1341110 697 2. 59. 3 8. 0.0 137. 7.2 7.7 2.47 .32 .98 .49 1351119 730 3. 62. 35. 0.0 91 . 6.9 7.4 2.45 . 33 1.00 . 50 141 965 453 1. 47. 53. 0.0 347. 8.2 8.4 2.36 . 13 .93 .48 145 914 349 1. 43. 57. 0.0 201. 8. 6 8.7 2.42 . 10 .98 .49 147 905 318 22. 39. 3 8. .3 113. 6.6 7. 1 3.26 . 28 .76 .43 148 817 404 24. 25. 20. 31. 1.0 128. 4. 1 4. 1 5.77 .04 .72 .42 149 839 433 15. 16. 23. 46. .4 201. 7. 7 6. 2 m •m • 151 878 473 2. 39. 59. 0.0 366. 8. 6 8.6 2. 19 • 1.02 . 51 152 891 439 1. 45. 54. 0.0 37 5. 8.3 8.4 2.38 .09 .88 .47 153 950 505 1. 51. 49. 0.0 362. 8. 0 8. 2 2.45 . 17 .84 . 46 154 914 516 1. 53. 46. 0.0 357. 7. 7 8. 1 2.52 . 27 .92 . 48 156 960 575 2. 57. 41. 0.0 307. 7.3 7.5 2.1 1 . 1 8 .89 .47 1581012 641 1. 57. 42. 0.0 269. 7.4 7. 9 2.60 .31 .91 .47 1601066 709 1. 56. 43. 0.0 192. 7. 6 8. 0 2.33 .25 .94 .48 16 11098 747 1. 53. 45. 0.0 143. 7. 8 8. 2 2.27 . 28 .95 . 49 1621066 848 6. 58. 36. 0. 1 63. 7. 0 7.4 2.60 .25 1.01 . 50 1631060 829 3. 50. 47. 0.0 106. 7.9 8. 1 2.50 . 1 9 .92 . 48 1641047 814 2. 50. 4 8. 0.0 157. 7. 9 8. 2 2.44 . 17 .96 .49 1651036 777 • 48. 52. 0.0 225. 8. 1 8.2 2.09 .09 .94 . 49 166 1014 753 • 47. 53. 0.0 243. 8.2 8.7 2.56 .30 .97 .49 167 989 712 * 49. 51. 0.0 282. 8. 0 8.4 2.35 .25 .94 . 49 168 972 676 1. 47. 52. 0.0 293. 8. 1 8.4 2.41 .24 .93 .48 169 951 640 1. 55. 44. 0.0 29 3. 7. 6 8. 0 2.58 .22 .92 .48 170 930 606 1. 55. 44. 0.0 313. 7. 6 8. 0 2.63 .29 .92 .48 171 892 583 • 53. 46. 0.0 338. 7. 7 8. 1 2.58 . 27 .90 .48 175 851 536 37. 63. 0.0 371. 9. 0 9. 0 2.49 .06 .93 . 48 182 955 7 74 1. 42. 57. 0.0 192. 8.4 8.6 2.12 . 1 1 .94 . 49 183 970 806 • 45. 54. 0.0 245. 8.2 8.4 2.06 . 15 .95 .49 184 980 83 6 4. 46. 50. 0.0 253. 8.0 8. 2 2.20 . 15 1.01 . 50 185 993 859 1. 50. 50. 0.0 .161. 7.9 8. 2 2.36 .22 .96 .49 1861011 898 3. 52. 45. 0.0 154. 7. 8 8. 1 2.33 .23 1.07 . 51 190 871 771 • 40. 60. 0.0 174. 8. 6 8. 8 2.12 .15 .94 .49 193 842 655 • 43. 57. 0.0 342. 8.5 8.9 2.31 .25 .90 . 48 196 79 6 549 * 42. 58. 0.0 375. 8.4 8.6 1.98 .23 .95 .49 200 7 43 535 • 43. 57. 0.0 .38 4. 8.4 8.7 1.98 .26 .95 .49 268 201 750 575 • 41. 59. .0 37 5. 8.4 8.5 1.80 . 12 .91 . 48 202 758 617 4 5. 55. 0.0 366. 8.4 8.4 1.88 .08 .95 .49 203 767 651 • 45. 55. 0.0 342. 8. 3 8.4 1.95 .14 .92 .48 204 787 714 • 47. 53. 0.0 315. 8.2 8. 3 2.06 .10 .96 .49 207 808 796 • 38. 62. 0.0 152. 8. 7 8.8 1.98 .08 .95 . 49 209 825 843 1. 3 5. 64. 0.0 293. 8.9 9. 0 2.08 .03 1.00 . 50 212 758 901 27. 72. 0.0 121. 9.3 9.3 1.98 -.01 1.00 . 50 213 744 864 • 32. 68. 0.0 174. 9.0 9. 1 2.06 1.1 0 .92 .48 214 735 830 • 30. 70. 0.0 155. 9.2 9.3 2.05 .07 .93 .48 215 725 793 2. 27. 71. 0.0 119. 9.2 9. 3 2.2 3 .07 .96 .49 217 716 745 • 36. 64. 0.0 287. 8. 8 9.0 2.05 .16 .90 . 47 219 704 696 1. 34. 65. 0,0 228. 8. 8 8.8 2.07 .02 1.01 . 50 220 70 3 685 1. 7. 27. 65. 0. 1 238. 9. 1 9. 1 3.17 -.09 1.23 . 55 221 693 644 . 38. 62. 0.0 329. 8. 6 8. 7 1.79 .09 1.01 . 50 222 676 580 38. 62. 0.0 379. 8. 7 8. 9 2.27 .16 .95 .49 22 3 666 532 33. 66. 0.0 38 4. 9.0 9. 1 1.83 .14 .72 . 42 225 657 489 1. 27. 72. 0.0 2 0 1 . 9.2 9. 2 1.96 .00 1.03 . 51 228 639 649 1. 33. 66. 0.0 267. 8. 8 8.9 2.00 .10 .97 .49 229 6 46 680 2. 30. 69. 0.0 176. 9.2 9. 2 2.31 .01 1.03 . 51 230 643 693 29. 71. 0.0 152. 9.2 9.4 2.04 . 1 1 .95 .49 231 647 703 • 29. 70. 0.0 210. 9. 1 9. 2 1.80 .08 .95 .49 232 656 735 1. 30. 69. 0.0 265. 9. 1 8.9 1.57 -.12 .95 .49 233 661 764 • 32. 6 8. 0.0 210. 9.0 9. 2 2.04 . 15 .87 . 47 234 664 783 2. 32. 66. 0.0 137. 9.0 9. 1 2.45 .01 1.03 . 51 236 668 810 1. 23. 76. 0.0 132. 9. 4 9.5 2.09 .08 .92 . 48 237 679 850 • 29. 71. 0.0 165. 9.2 9.3 1.90 .04 1. 29 .56 238 639 885 5. 4 1 . 17. 3 7. .9 7 3 . 4. 7 5.8 4.26 .27 .86 . 46 251 565 575 . 35. 65. 0.0 399. 8. 8 9. 0 2.05 .16 .93 .48 25 5 455 451 1. 3 1 . 29. 39. .5 165. 6.0 6.5 3.41 . 1 6 .79 .44 257 466 566 • 33. 67. 0.0 402. 8. 8 9. 1 2.06 .20 .95 .49 259 498 643 26. 74. 0.0 338. 9.3 9.4 1.81 .15 .83 . 46 26 1 511 677 • 29. 71. 0.0 316. 9.2 9. 3 2.0 3 .06 .86 . 46 26 2 515 701 1. 28. 72. 0.0 204. 9.3 9.4 2.06 .06 .95 . 49 263 516 719 37. 17. 47. .6 97. 7. 6 7.2 3.63 -.06 .64 .39 26 4 520 730 7. 28. 65. . 1 187. 9.0 9.0 2.38 0.00 1.0 . 50 265 526 759 2. 8. 2 4. 67. . 1 139. 9. 1 9. 0 * • • • 267 544 832 • 27. 73. 0.0 168. 9.4 9.3 1.80 -.05 1.03 . 51 268 554 870 20. 18. 20. 42. 0.6 97. 5.0 5.4 5.77 -. 32 .77 .43 269 453 876 6 1 . 13. 26. 1.6 9 1 . 3.2 5.0 3.61 . 70 .94 . 48 280 386 552 * 28. 72. 0.0 406. 9. 2 9.3 1.9 2 .09 .89 .47 282 373 476 * 20. 80. 0.0 348. 9. 6 9.6 1.83 .01 .98 .50 284 363 447 2. 26. 72. 0.0 274. 9.4 9.5 2.89 .04 1.14 . 53 286 353 414 9 0 . 6. 4. 9.0 82. 3.2 3. 2 .35 .37 2. 24 . 69 287 280 420 24. 47. 14. 15. 2.4 104. 2.2 2.9 4.63 .30 1.21 .55 289 30 3 525 * 24. 76. 0.0 408. 9.3 9.3 1.74 -.01 1.01 . 50 290 316 590 m 27. 72. 0.0 402. 9.2 9. 2 1.69 .01 1.01 . 50 291 320 611 1. 2 5. 74. 0.0 384. 9.2 9.2 1.83 .03 .98 . 50 292 325 637 • 20. 80. 0.0 342. 9.6 9.6 1.80 0.00 .98 .50 293 329 649 26. 74. 0.0 366. 9.4 9.4 1.83 -.01 .98 . 50 29 4 334 676 9. 21. 16. 53. .4 279. 8. 2 6. 9 5.06 -.24 .90 .47 295 336 683 2. 16. 19. 63. .2 223. 9.0 8. 0 4.26 -.2 9 1. 25 . 56 297 336 702 m 24. 76. 0.0 375. 9.4 9.4 1.8 3 -.01 .98 . 50 298 341 720 • 2 5. 75. 0.0 292. 9.4 9.4 1.90 -.01 .99 . 50 299 350 766 1. 26. 73. 0.0 170. 9. 4 9.4 2.2 3 -.02 1.04 . 51 269 300 362 81 8 14. 24. 62. . 2 210. 8. 8 8.3 3.33 -. 1 9 1.18 .54 301 366 848 3. 27. 21. 0.0 177. 9.2 9. 1 2.05 -.0 7 1.02 . 51 302 290 832 10. 23. 66. . 1 137. 9.2 8.6 3.16 -.20 1. 12 .53 303 280 7 73 • 24. 76. 0.0 216. 9.4 9.4 1.84 -.03 1.00 . 50 305 268 704 • 23. 77. 0.0 30 4. 9. 4 9.5 1.9 8 .12 .99 .50 309 262 624 3. 23. 74. 0.0 324. 9.4 9.5 2.22 0.00 1.08 . 52 311 238 512 . 24. 76. 0.0 408. 9.4 9.7 2. 25 .22 .97 .49 3 13 231 465 16. 27. 57. .2 195. 8.6 8.0 3.31 -.15 .72 . 42 315 234 433 66. 24. 10. 1.9 77. 3.7 3.9 1.8 6 .41 3.48 .78 317 186 501 • 22. 78. . 0.0 408. 9.4 9.6 1.78 .14 .81 .45 321 196 666 • 27. 73. 0.0 393. 9.2 9. 2 2. 1 4 -.14 1.31 .57 326 200 762 • 23. 76. 0.0 210. 9.6 9.6 2.11 .02 .96 .49 327 204 796 • 22. 77. 0.0 220. 9.4 9.5 2.00 . 1 1 .97 .49 328 152 7 72 4. 2 5. 71. 0.0 192. 9.3 9.3 2.32 -.0 8 1. 12 . 53 329 144 72 7 2 5. 75. 0.0 338. 9.4 9. 4 1.98 -.03 1.00 . 50 330 134 669 * 25. 75. 0.0 397. 9.2 9.3 1.90 . 04 .99 . 50 331 129 61 8 6. 22. 72. 0.0 256. 9.4 9. 3 2.51 -.08 1. 22 .55 332 126 604 • 23. 77. 0.0 238. 9.6 9.7 2.26 .06 1.02 . 50 334 116 561 * 25. 75. 0.0 244. 9. 7 9.7 2.39 .01 .96 .49 335 112 531 a 23. 7 7. 0.0 402. 9.6 9.7 2.1 5 . 1 1 .91 .48 336 103 502 3. 20. 77. 0.0 248. 9.6 9.5 1.3 3 -.12 1. 24 . 56 337 94 4 79 17. 51. 14. 18. 2. 1 73. 2.7 3. 1 , • * • 340 51 504 13. 22. 15. 50. .5 265. 8. 0 6.3 4.94 -.4 5 .74 . 42 34 1 50 516 7. 42. 11. 40. 1.0 326. 5.2 5.6 4.51 .08 .76 .43 34 2 52 536 14. 9. 18. 59. .3 322. 8. 8 7.4 4.88 -.42 1. 16 . 54 34 3 51 571 22. 19. 58. .3 262. 9.6 m * * * • 34 5 53 621 • 22. 78. 0.0 280. 9. 4 9.5 1.9 1 .06 .94 .49 347 53 653 9. 22. 68. 0.0 247. 11.0 m • • * • 349 73 707 2 5. 75. 0.0 388. 9.3 9. 3 1.80 .04 .91 .48 350 84 747 1. 24. 76. 0.0 356. 9.2 9.2 1.63 .08 .94 .49 351 98 802 80. 10. 10. • 132. 3.4 3. 6 1.90 .56 5. 18 . 84 SO. = SAMPLE NUMBER; X,Y = X AND Y COORDINATES; % = WEIGHT PERCENT, G = GRAVEL, S = SAND, Z = SILT, C = CLAY; S/M = SAND TO MUD RATIO; D = DEPTH IN METRES; INCLUSIVE GRAPHIC MEASURES (FOLK AND WARD, 1957) ARE IN PHI UNITS: MD = 1 ED IAN, MZ = GRAPHIC MEAN, S.D. = INCLUSIVE GRAPHIC STANDARD DEVIATION, SK = INCLUSIVE GRAPHIC SKEWNESS, K = GRAPHIC KUHTOSIS, K« = UORttALISED KURTOSIS (K/(1+K) ). 270 APPENDIX 11(A) DATA KATR1X FOR FACTOR ANALYSIS SAMPLE COORDS PHI: WT? NO. X Y - 3 - 2 -1 ' 0 1 2 3 4 5 6 7 8 9 10 M O 101626 221 1.34 0 .85 0 .63 1.39 2 .30 17 .69 3 5 . 8 7 7 .67 7 .57 4 8 . 0 3.41 3.21 3.09 10.14 131742 223 30 .25 9.95 4 .22 2 .92 4 .97 16 .96 4 . 3 5 4 . 7 9 3.99 3.75 2 .86 2.13 1.62 1.87 5.37 191900 288 0 .53 0 . 9 9 0 .45 6.88 3 1 . 7 7 6 .23 7 .92 6.96 8 .09 5.95 4.41 3.89 3.60 12 .26 211909 337 0.58 8.45 39 .51 39 .19 5.24 1.45 0.84 0 .99 .45 .41 .49 1.77 231909 402 0. 07 7.79 52 .55 10.49 .6.26 4.91 3.22 3.05 4 .74 6.94 l 251912 482 0 .05 0 .05 0 .5C 7 .21 27 .51 19.03 14 .06 7.14 5. 19 3.89 3.46 11.9 401741 268 0 .76 2 .79 4 .33 5.53 1 8 . 6 7 10 .77 12 .44 8.96 7.01 4 .33 3.28 2.54 2 . 6 9 7.91 421722 342 7.64 3.80 3 .53 4 .15 6.48 8 .54 3.30 15 .83 12.46 8.68 5.20 3.78 3.31 3.94 9.46 441712 400 0.01 0 . 0 5 0 . 0 7 2.16 37.42 14.21 13.20 7.44 4 . 9 0 4.90 3.45 12.18 451706 456 0.01 0 .10 0 .77 15 .79 19.55 16 .70 13.21 7.11 5.69 3 .49 17.59 461637 449 9.76 5.50 6.15 7.16 10.74 15 .14 9 .79 5.06 5.27 5.66 4 . 1 9 2.87 2.48 2.71 7.52 481632 345 0 . 1 7 0 .03 0.02 0 .35 3 2 . 4 0 3 6 . 8 7 3 .60 5.24 4.31 3.23 2.95 2.95 7.69 501628 268 0.10 0.23 1.71 4 7 . 7 4 2 3 . 2 9 3.99 5.27 3.35 2.85 2.38 2.57 6.52 531610 156 0.01 0 .10 0 *65 2 8 . 5 8 9.19 13.54 9 .39 8 .00 6.13 6.52 17.89 2 7 1 541484 187 0.07 0.09 0.03 0.33 16.82 46.82 4.52 6.38 3.73 3.80 3.59 3.94 9.89 561494 255 0.01 0.25 8.71 62.30 8.01 4.81 3.00 2.10 2.10 1.90 6.81 581511 336 0.16 0.08 0.59 22.56 49.55 7.38 4.51 3.08 2.05 1.95 1.95 6.15 601516 405 0.31 3.95 57.13 7.83 6.62 5.30 3.20 3.20 1.43 11.03 621523 461 0.03 0.06 1.26 38.93 27.88 4.94 5.18 5.43 2.90 3.02 2.59 7.77 731327 217 0.02 0.10 0.89 14.82 7.37 10.74 10.74 11.70 10.10 10.10 23.41 751340 255 0.04 0.48 0.63 29.77 18.03 12.19 6.86 5.84 4.57 4.57 17.02 761347 277 0.24 1.35 31.31 16.46 12.28 7.53 5.86 5.02 4.88 15.07 771361 308 0.05 0.77 31.83 15.40 13.14 7.70 6.49 5.29 4.68 14.65 791376 368 0.05 1.35 41.59 14.84 9.48 6.08 5.24 4.39 3.40 13.58 811389 425 0.01 0.25 26.90 39.13 2.58 2.36 3.81 4.65 4.27 3.51 2.98 9.54 821395 447 0.44 65.44 32.99 0.71 0.05 0.05 0.00 0.00 0.00 0.00 0.00 831315 452 0.15 29.72 65.92 2.81 0.33 0.2 0.2 . 2 .2 .C7 . 2 851299 400 0.03 3.69 33.98 16.95 7.64 7.82 6.27 5.27 4.00 4.09 10.23 861288 373 0.03 0.26 23.30 23.29 14.04 8.08 6.51 4.97 4.28 15.24 871274 333 0.01 0.09 9.07 22.04 17.69 11.33 7.55 6.56 6.36 18.49 881267 299 0.02 0.17 16.37 21.33 13.52 9.87 8.77 6.21 4.57 19.18 891254 256 0.03 0.19 14.88 18.55 12.56 11.32 9.20 7.96 5.31 19.99 272 931112 217 7 .81 0 . 9 0 2 . 6 2 2 . 0 5 3 . 3 8 5 . 7 1 10.21 2 5 . 0 5 6 . 4 6 4 . 1 3 9 . 5 6 5 . 1 7 5 .68 4 . 6 5 6 .62 961150 320 0 . 0 2 0 . 0 9 4,.32 16 . 13 14 .18 1 4 . 4 2 1 1 . 0 0 10 .51 12 .22 17.11 971159 341 0 . 0 1 0 . 0 1 0 . 0 6 4 . 6 8 1 1 . 0 2 1 5 . 0 9 1 6 . 0 3 1 2 . 5 3 8 . 7 6 7 .81 2 4 . 1 1 981170 379 0 . 0 2 0 . 1 2 2 . 6 2 2 0 . 1 0 2 0 . 9 7 1 3 . 5 0 9 . 4 0 7 . 4 7 7 .47 18.32 1001199 452 0 . 0 5 4 . 7 5 2 0 . 6 2 1 2 . 4 8 9 . 2 2 1 1 . 6 4 9 . 6 0 6 .92 5 .82 4 . 2 5 14 .63 1021220 498 0 . 0 4 0 . 2 1 4 . 1 6 3 2 . 1 6 1 8 . 6 5 1 4 . 4 6 9 . 3 3 5 . 8 3 4 .20 2 . 3 3 8 .63 1031182 543 0 . 0 3 0 . 1 1 0 . 0 3 0 . 9 0 2 . 7 6 2 0 . 2 5 19 .76 1 8 . 2 6 1 2 . 1 7 7 . 1 0 4 .94 4 . C 6 9 . 6 3 1041171 622 0 . 0 2 0 . 1 9 4 . 4 0 1 2 . 9 3 2 1 . 5 9 2 2 . 1 1 9 .62 8 . 5 8 6 .24 14 .31 1C61125 550 0 . 0 9 0 .27 3 . 3 9 1 2 . 5 3 2 0 . 7 8 1 9 . 9 5 1 3 . 4 9 8 . 5 5 6 .08 5 . 1 3 12 .73 1081092 493 0 . 0 2 0 . 0 4 0 . 1 7 1 .13 2 0 . 4 0 1 4 . 5 7 15 .02 1 3 . 5 5 8 .98 5 .06 5 . 3 9 15 .67 1091077 484 0 .01 0 . 1 2 0 . 6 8 1 5 . 9 9 17 .02 1 4 . 7 4 1 1 . 9 6 9 . 7 4 7 .51 4 . 4 3 17 .8 1111151 498 0.03 0 .09 1 . 2 3 1 6 . 0 7 2 1 . 5 7 1 8 . 1 9 1 2 . 0 3 7 . 8 4 5 .88 4 . 4 8 12 .60 1131119 446 0 .01 0 . 1 6 1.38 1 2 . 4 3 1 4 . 7 8 1 6 . 5 0 1 3 . 0 9 9 .96 7 .97 6 . 2 6 17 .65 1141104 433 0 . 0 2 0 . 1 7 6 . 3 7 1 8 . 3 4 18 .51 1 4 . 1 5 9 . 8 0 8 .71 7 . 6 2 16 .33 1151028 393 1 .72 9 .91 1 8 . 7 7 1 3 . 5 6 9 . 6 5 1 6 . 1 6 9 . 3 9 2 0 . 8 6 1161051 360 2 . 6 2 1 0 . 7 3 1 7 . 5 4 17 .28 13 .61 8 . 9 0 29 .32 1181013 313 1 .00 3 .31 1 0 . 3 6 1 5 . 7 4 16 .57 15 .33 13 .26 24 .44 119 986 273 0 . 4 3 0 .74 0 . 5 8 1 .63 5 . 0 6 0 .81 9 . 9 7 8 .34 9 . 5 9 11 .10 11 .10 10 .91 2 1 . 2 5 273 121 979 290 1 3 . 9 5 13.52 16 .13 2 4 . 8 5 2 . 7 6 6 . 1 0 8 .72 1 3 . 9 5 123 940 343 1 9 . 1 5 16 .92 1 5 . 5 9 1 8 . 2 6 0 . 6 9 2 . 6 7 9 . 8 0 1 6 . 9 2 1241004 392 16 .72 14 .86 1 1 . 8 9 2 3 . 4 0 0 .82 5 . 5 7 1 0 . 7 7 1 5 . 9 7 1251023 421 1 5 . 3 6 11 .42 10 .17 2 4 . 4 9 1 . 2 0 6 . 2 3 15.3:> 1 5 . 7 7 1261034 463 13 .22 10 .25 8 . 9 15 .10 2 .91 1 1 . 3 3 1 6 . 9 9 2 1 . 3 1 1271056 521 11 .41 8 . 7 5 7 . 1 6 16 .98 1 2 . 2 0 1 3 . 5 3 1 5 . 6 5 1 4 . 3 2 1281066 556 1 1 . 5 9 8 .04 7 . 3 3 16 .08 0 .01 0 . 0 2 0 . 1 1 6 . 1 9 1 6 . 0 8 17 .98 1 6 . 5 6 1291075 580 10 .84 8 . 6 7 6 .78 14 .64 0 .01 0 . 0 3 0 . 0 7 6 .12 2 0 . 3 1 1 8 . 1 6 1 4 . 3 7 13C1080 596 1 1 . 1 0 9 . 9 9 8 .21 1 7 . 3 1 0 . 0 9 0 .21 0 . 4 1 2 . 6 3 1 2 . 7 9 1 8 . 6 5 1 8 . 6 5 1311083 615 11 .96 9 . 3 1 7 .64 16 .62 2 . 9 6 1 2 . 9 6 19 .94 1 8 . 6 1 1321090 629 12 .78 8 .94 8 . 6 3 1 6 . 2 9 2 . 8 9 1 1 . 5 0 2 1 . 4 0 1 7 . 5 7 1331100 664 13 .01 10 .36 9 . C 3 18 .06 1 .73 8 . 2 3 1 9 . 1 2 2 0 . 4 5 1341110 697 15 .21 10.81 8 .11 1 9 . 6 0 2 . 0 1 7 . 4 3 1 6 . 5 6 2 0 . 2 8 1351119 730 14 .10 1 0 . 4 7 6 . 4 4 17 .72 2 .94 9 . 6 7 18 .12 2 0 . 5 4 141 965 453 16 .69 13 .91 1 2 . 1 7 2 6 . 7 7 0 . 5 6 3 .48 10 .78 1 5 . 6 5 145 914 349 17 .82 13 .79 1 4 . 3 7 2 8 . 4 5 0 . 8 6 3 . 7 4 7 . 4 7 1 3 . 5 1 147 905 318 8 . 9 7 9 . 2 4 10 .33 18 .76 0 .01 0 . 2 C 1 .61 2 0 . 4 1 1 7 . 4 0 6 . 8 0 6 . 2 5 148 817 404 6 . 2 8 6 .98 8 .74 9 . 9 3 5 .56 4 . 6 2 3 .62 3 . 8 7 4 . 6 4 8 . 0 0 5 . 2 3 3 . 9 5 4 . 1 9 6 .98 17 .44 274 149 839 433 9 . 5 7 2 . 7 6 2 .32 2 . 0 3 3 .45 4 . 5 8 3 . 1 8 3 . 1 9 3 . 2 5 4 . 1 8 3 . 8 3 1 1 . 6 7 9 . 9 3 10 .98 2 5 . 0 9 151 878 473 1 .63 2 . 8 6 6 . 8 0 1 2 . 8 8 16 .45 15 .38 13 .24 3 0 . 7 6 152 691 439 0 . 5 6 3 . 8 6 1 2 . 4 3 1 5 . 4 3 13 .72 1 5 . 0 0 1 3 . 2 9 25 .72 153 950 505 0 . 5 3 4 . 5 0 1 4 . 2 6 1 6 . 8 9 15 .01 1 2 . 7 6 1 1 . 2 6 24 .77 154 914 516 0 . 7 4 4 . 8 2 16 .08 1 8 . 0 8 14 .48 1 2 . 0 6 10 .45 23 .31 156 960 575 2 . 0 4 8 .08 1 7 . 4 6 1 7 . 7 8 13 .58 17 .14 9 . 3 8 1 4 . 5 5 1581012 641 1 .39 7.61 1 7 . 4 7 1 6 . 9 0 14 .93 10 .14 9 . 3 0 2 2 . 2 6 16C1066 709 0 . 9 3 5 .01 15 .02 1 8 . 4 4 17 .39 1 1 . 5 9 1 0 . C l 21 .61 1611098 747 1 .09 3 .02 1 0 . 7 8 2 1 . 5 5 18 .10 1 2 . 5 0 9 . 7 0 23 .27 1621066 848 0 .01 0 . 5 7 1 .62 0 . 4 8 3 . 1 2 9 . 3 4 1 7 . 0 5 1 7 . 9 6 14.11 9 . 5 3 8 . 4 3 1 7 . 7 8 1631C60 829 0 . 0 2 0 .32 0 . 4 7 0 . 6 3 1 . 0 9 4 . 3 6 1 1 . 9 2 1 7 . 3 6 16 .85 13 .11 10 .04 2 3 . 8 3 1641047 814 1 .71 6 . 3 1 8 . 0 8 1 7 . 3 0 18 .11 12 .26 10 .67 2 4 . 5 7 1651036 777 0 . 4 8 4 . 9 6 8 . 0 2 1 6 . 9 3 17 .82 15 .78 8 .40 27 .62 1661014 753 0 .41 3 . 2 4 6 . 3 5 1 7 . 8 4 19 .46 1 2 . 9 7 10 .68 2 9 . 0 5 167 989 712 0 . 4 7 4 . 2 8 9 .91 1 8 . 4 7 16. 14 1 3. 22 10. 50 27 .02 168 972 676 0 . 6 1 1.92 1 1 . 6 9 1 7 . 0 5 16 .50 12 .65 1 1 . 9 6 2 7 . 6 3 169 951 640 0 . 8 0 6 .28 1 5 . 0 7 1 9 . 0 9 14 .57 11 .55 8 . 7 9 2 3 . 8 6 17C 930 606 0 . 9 0 4 . 7 3 18 .02 1 7 . 7 9 14.41 1 1 . 2 6 8 .33 2 4 . 5 5 275 171 892 583 0 . 4 9 5 . 5 6 1 5 . 7 6 1 8 . 2 3 13.91 11 .43 9 .58 2 5 . 0 3 175 851 536 0 . 3 2 1.28 1 0 . 2 6 8 . 6 5 1 6 . 3 5 13 .78 1 1 . 8 6 3 7 . 5 0 182 955 774 0 . 6 2 2 . 7 5 6 .41 1 4 . 2 0 18 .70 1 6 . 2 6 1 3 . 5 7 2 7 . 0 2 183 970 806 0 . 3 2 2 . 3 6 7 . 6 7 1 6 . 5 2 18 .88 1 8 . 2 9 10 .62 2 5 . 3 6 184 980 836 0 .14 1 .07 1 .56 0 . 6 8 0 . 2 5 2 . 5 1 6 . 5 4 1 8 . 1 1 19 .11 15 .59 1 1 . C 6 2 3 . 3 9 185 993 859 0 . 8 7 4 . 6 9 9 . 5 9 1 6 . 7 3 1 8 . 5 6 14 .48 9 . 5 9 2 5 . 5 0 1861011 898 . 0 . 1 1 0 . 8 9 0 . 7 6 0 . 1 8 0 . 1 5 0 . 4 7 3 .81 9 .51 1 6 . 0 1 2 2 . 2 0 1 2 . 0 5 1 1 . 1 0 21 .88 190 871 771 0 . 2 5 1.57 5 . 3 5 1 2 . 2 7 2 0 . 7 7 1 5 . 1 0 16 .68 2 8 . 0 1 193 842 655 0 . 4 1 2 . 2 6 3 . 5 5 1 8 . 0 5 19 .02 1 3 . 8 6 1 2 . 5 7 .33.30 196 796 549 0 . 2 4 1 .36 5 . 7 7 1 4 . 2 5 2 0 . 3 6 1 5 . 2 7 17 .98 2 4 . 7 7 200 743 535 0 . 1 9 0 . 7 7 3 . 8 5 1 2 . 7 2 2 5 . 4 4 15 .03 1 5 . 8 0 2 6 . 2 1 201 750 575 0 . 1 9 0 . 4 5 4 . 0 7 1 5 . 3 6 2 1 . 2 3 19.42 16 .26 2 3 . 0 3 202 758 617 0 . 2 3 1 .29 6 .02 1 6 . 3 4 2 1 . 0 7 17 .63 1 5 . 4 8 2 1 . 9 3 203 767 651 0 . 2 9 1.41 5 .64 1 8 . 3 4 19 .28 17 .40 15 .05 22 .58 204 787 714 0 . 3 9 3 . 1 7 7 . 7 0 1 7 . 2 1 19 .02 1 7 . 6 6 13 .58 21 .28 207 808 796 0 . 1 8 1.21 5 . 1 4 1 2 . 7 0 18 .75 16 .94 18 .15 26 .92 209 825 843 0 . 9 2 1 .77 4 . 6 0 9 . 5 5 19.11 14 .51 1 6 . 9 9 3 2 . 5 6 212 758 901 14 .16 1 6 . 9 9 1 6 . C 5 3 9 . 1 7 0 . 4 3 C . 9 4 3 . 7 8 8 . 5 0 276 213 744 864 16.76 17.21 16.76 33.97 0.30 0.00 4.41 10.59 214 735 830 15.89 17.00 17.CO 36.22 0.20 0.00 3.70 9.98 215 725 793 0.25 0.16 0.18 15. 10 15.96 16. 81 38.43 0.18 0.46 0.95 0.86 2.92 7.72 217 716 745 18.51 16.90 15.69 31.39 0.20 0.80 3.62 12.88 219 704 696 18.41 16.74 16.32 31.80 0.84 2.09 4.18 9.62 22C 703 685 0.66 0.38 0.77 0.85 12.59 11.87 14.87 37.90 1.64 2.65 1.10 2.15 4.43 8.15 221 693 644 22.42 17.18 16.70 28.15 0.29 1.43 5.25 8.59 222 676 580 19.18 16.44 14.92 30.45 0.12 0.61 7.31 10.96 223 666 532 18.84 15.35 19.89 31.05 0.21 0.35 I.76 12.56 225 657 489 15.92 16.27 19.81 36.09 0.94 1.42 2.83 6.72 228 639 649 17.12 18.71 15.53 31.85 0.88 1.99 2.79 11.15 229 646 680 16.38 15.02 17.C7 36.52 1.71 2.73 2.39 8.19 230 64 3 69 3 18.09 17.41 14.51 39.08 1.02 2.90 7.00 231 647 703 17.01 18.95 18.47 33.04 0.39 0.49 1.94 9.72 232 656 735 18.63 17.11 30.42 21.29 0.76 0.76 1.14 9.89 233 661 764 17.98 16.76 16.14 35.15 0.08 1.04 0-41 11.65 234 664 783 16.16 15.67 14.69 35.26 2.06 3.92 4.90 7.35 236 668 810 13.89 16.77 17.C3 42.19 0.68 1.57 1.05 6.81 277 237 679 850 16 .92 1 6 . 5 0 17 .34 3 7 . 2 3 238 635 885 4 . 4 1 0.31 0 . 7 1 1.03 6 . 4 3 7 . 0 5 9 . 5 0 2 0 . 1 7 251 565 575 19 .45 1 6 . 8 6 16.54 31 .12 255 455 451 1 .02 1 .79 8 . 8 8 9 . 1 6 1 0 . 5 9 18 .90 257 466 566 18 .23 18 .23 14 .66 3 4 . 0 7 259 498 643 20. 83 18 .32 18. 32 3 7 . 3 6 261 511 677 17 .48 1 7 . 1 3 16 .41 37 .82 262 515 701 15 .79 16 .52 1 8 . 3 6 37 .08 263 516 719 0 . 0 5 8 . 4 2 11 .14 1 0 . 5 9 2 4 . 9 9 264 520 730 16 .02 1 5 . 3 9 15 .07 3 4 . 8 6 265 526 759 2 . 0 7 12.48 1 5 . 3 9 15 .97 3 5 . 4 2 267 544 832 16 .82 1 5 . 7 7 18 .23 3 8 . 9 0 268 554 870 7 .61 7 . 7 8 4 . 4 3 3 .61 1.92 7 . 5 3 9 . 6 4 10 .11 2 2 . 6 3 269 453 876 0 . 1 0 0 .82 4 . 7 4 5 .31 6 . 1 6 14.21 28C 386 552 16 .64 19 .23 1 5 . 5 0 36 .98 282 373 476 12 .03 1 8 . 9 0 1 8 . 9 0 4 2 . 1 0 284 362 447 8 . 1 3 15 .88 12 .78 4 3 . 7 6 286 353 414 0 . 0 4 . 3 1 .94 . 8 4 2.62 0 . 1 7 1.27 2 . 5 4 8 .04 1.72 4 . 5 6 1 9 . 2 5 1 4 . 2 1 4 . 2 1 2 . 2 3 3 . 8 4 0 .14 0 . 9 7 3 . 2 4 1 1 . 6 7 2 . 8 2 5 . 1 5 1 9 . 4 4 1 2 . 0 3 5 .73 2 . 5 8 0 . 1 6 0 . 7 9 3 . 1 7 1 0 . 7 0 0 . 1 4 0 .72 1 .80 2 . 5 1 0 . 0 9 1.07 1 .43 8 .56 0 . 5 1 1.47 1 .47 8 .81 0 . 5 7 17 .32 1 8 . 7 7 2 . 4 5 1 .36 4 . 3 5 7 . 0 5 0 .31 3 . 1 4 8 .17 7 . 6 5 1 .74 2 .32 9 . 9 7 0 . 1 1 0 . 3 5 2 . 4 5 7 . 3 6 2 . 6 4 3 . 0 6 6 . 5 8 5 .64 2 . 5 9 4 . 2 3 1 3 . 7 9 3 0 . 9 3 1 5 . 6 0 2 .76 2 . 7 5 2 . 8 4 0 . 1 5 1.11 1 .48 8 .51 0 . 3 3 1 .29 0 . 8 6 5 . 5 9 2 . 0 3 3 . 8 7 3 . 8 7 9 . 6 8 0 . 9 8 3 4 . 0 5 5 4 . 7 8 4 . 0 8 0 . 7 3 0 . 6 3 278 287 28C 420 2 .29 2 .50 289 303 525 1 5 . 4 3 19 .29 290 316 590 1 6 . 9 6 18 .95 291 320 611 1 5 . 4 5 1 9 . 8 7 292 325 637 13 .41 1 9 . 0 3 293 329 649 1 6 . 8 0 16 .80 294 334 676 8 . 4 8 12 .31 295 336 683 7 . 9 9 12 .50 297 336 702 15 .97 16 .36 298 341 720 15 .54 1 7 . 9 9 299 35C 766 13.89 16 .39 300 362 818 12 .71 1 3 . 4 5 301 366 848 14 .86 1 7 . 0 5 302 290 832 1 0 . 1 5 1 3 . 9 5 303 280 773 14 .50 18.24 305 268 704 14.21 1 9 . 0 7 309 262 624 18.58 16 .89 311 238 512 14 .48 2 0 . 1 7 9 . 4 3 1 4 . 2 4 1 0 . 6 5 5 .23 2 .91 9 . 9 9 1 8 . 8 0 37 .61 1 8 . 4 6 34.92 18 .21 36 .42 1 9 . C 3 4 1 . 9 6 19 .27 3 7 . 5 5 6 .94 2 . 2 9 2 . 3 3 3 . 7 8 12 .86 27 .90 . 0 .72 1 .16 1.91 2 .32 14 .93 3 5 . 7 6 2 0 . 2 5 3 8 . 9 4 18 .40 38 .84 1 7 . 5 0 39 .44 15 .81 3 2 . 3 6 2 1 . 8 6 31 .90 1 6 . 4 9 36 .02 18 .71 38 .82 1 7 . 2 0 4 0 . 7 7 18 .58 3 8 . 5 2 1 5 . C O 4 0 . 8 5 7 . 0 8 1 1 . 4 4 1 2 . 3 9 8 . 1 2 2 . 2 9 1 .46 0 . 1 9 1 .45 0 . 0 0 7 . 2 3 0 . 2 4 0 . 5 0 2 . 0 0 7 . 9 8 0 .67 0 . 5 5 2 .21 6 . 6 2 0 . 0 9 0 . 8 7 0 . 4 3 5 . 1 9 0 . 2 0 0 . 9 9 0 . 9 9 7 .41 5 .61 5 . 8 5 3 . 7 1 1 .37 2 . 7 4 3 . 8 3 4 . 0 5 5 . 1 7 2 . 5 1 1.62 2 . 4 3 6 .94 0 . 3 1 0 . 0 0 2 . 3 4 5 .84 0 . 2 5 0 . 8 2 1 .64 6 .54 0 . 8 3 1.39 6 . 3 9 4 . 1 7 0 . 0 3 0 . 6 0 6 . 2 3 7 . 5 7 2 . 5 2 2 . 5 1 6 .21 2 . 5 1 2 .19 1 .75 7 . 8 7 0 . C 7 0 . 0 7 0 . 1 7 0 .91 9 . 1 0 5 . 7 2 2 . 5 4 4 . 8 2 0 . 3 7 1 .40 0 .94 7 . 0 2 0 . 1 4 1.12 0 . 3 7 7 . 1 1 0 .04 0 . 5 0 3 . 9 6 1 .53 1.69 1 .35 1 .35 0 . 2 1 1 .03 0 .52 7 . 7 6 279 313 231 465 8 . 5 0 12 .91 13 .53 30 .58 315 234 433 1 .86 1 .63 2 . 1 0 5 . 8 3 317 186 501 1 5 . C O 19 .13 1 8 . 7 6 3 9 . 7 6 321 196 666 1 5 . 1 4 1 8 . 5 0 19 .62 3 4 . 7 5 326 2CC 762 13 .64 1 5 . 7 3 17 .48 4 3 . 0 1 327 204 796 13 .88 18 .62 17. 54 40 . 62 328 152 772 14 .39 16 .14 1 7 . 3 0 37 .33 329 144 727 1 4 . 2 3 1 5 . 4 7 2 2 . 2 8 3 7 . 1 3 330 134 669 1 3 . 8 9 17 . 16 2 2 . 88 34 . 31 331 129 618 11 .67 15 .68 17 .87 3 8 . 2 8 332 126 604 13 .86 1 6 . 8 7 1 7 . 1 7 4 2 . 4 7 334 116 561 1 2 . 5 0 1 4 . 6 9 15 .63 4 4 . 3 8 335 112 531 14. 85 1 6 . 5 9 16 . 16 4 4 . 11 336 103 502 1 1 . 5 3 1 5 . 0 5 2 0 . 1 7 4 0 . 7 0 337 94 479 15 .93 1 .01 0 . 7 5 2 . 6 3 12 .14 2 4 . 6 4 2 .27 3 . 8 6 4 . 7 7 9 .32 340 51 504 8 . 6 9 4 .52 2 . 9 5 3 .20 8 .82 3 . 9 0 6 . 4 7 1 1.65 13 .20 24 .85 341 50 516 4 . 5 8 2 . 0 2 2 . 2 4 4 . 0 1 16 .93 16 .12 5 . 8 5 9 .41 1 0 . 4 3 2 0 . 3 5 1 . 5 9 1 4 . 1 4 9 .51 4 . 4 2 4 . 4 2 0 . 1 2 1 .00 3 . 7 9 14 .29 4 7 . 2 5 1 7 . 4 7 3 . 7 3 0 . 9 3 0 . 2 3 0 .38 1.50 5 . 2 5 0 .22 7 . 2 9 0 . 0 0 4 . 8 4 0 . 3 5 1.40 1 .40 6 . 9 9 0 . 4 7 C . 6 7 1 .35 6 . 4 3 3 . 7 7 3 .31 2 . 5 3 5 . 2 5 0 . 3 7 1.24 4 . 3 3 4 . 9 5 0 . 3 3 C C O 4 . 0 9 7 . 3 5 5 .94 3 . 2 8 2 . 1 9 5 . 1 0 3 . 3 1 1 .25 2 .11 4 . 0 6 4 . 2 2 7 . 5 0 1 .76 1.31 5 .24 3 . 1 1 3 . 6 0 1 .80 3 . 2 4 1 1 . 1 0 7 . 7 3 1 .R2 2 . 0 5 3 . 2 2 4 . 9 2 2 . 0 7 1 .55 2 .72 1.01 1.53 2 . 8 0 342 52 536 3 . 4 8 7 .38 3 .22 0 .87 0 . 1 8 0 .92 2 . 6 6 4 .51 2 . 3 2 2 . 6 9 3 . 8 5 9 . 3 6 10 .26 1 4 . 4 9 3 3 . 8 3 2 8 0 343 51 571 11.52 6.50 3.54 48.44 0.41 0.96 4.13 8.49 8.44 4.32 1.77 1.48 345 53 621 13.28 19.50 18.67 39.42 1 . 6 6 2.08 5.39 347 53 653 11.96 1.81 7.58 58.36 0.07 0.46 1.88 7.00 2.87 2.90 4.71 349 73 707 16.95 18.73 20.52 35.68 0.10 1.34 1.34 5.35 350 84 747 15.70 20.35 23.84 31.40 0.58 0.58 1.16 6.40 351 98 802 1.89 C O 2. 83 6. 84 0.06 2.23 22.64 55.28 6.14 0.00 2.12 APPENDIX 11(B) VARIMAX FACTOR MATRIX No. X Y COMM. 1 2 3 4 10 1626 221 0.5139 0.6552 -0.2460 0.0336 -0.1517 13 1742 223 0.5599 0.3707 0.2938 0.1836 0.5499 19 1900 288 0.4768 0.5141 0.3348 0.1537 0.2772 21 1909 337 0.6224 0.5263 0.4497 0.3721 0.0689 23 1909 402 0.8495 0.4702 0.5612 -0.3136 -0.4638 25 1912 482 0.9902 0.5823 0.3248 -0.6862 -0.2732 40 1741 268 0.7905 0.6202 0.4722 0.1593 0.3969 42 1722 342 0.9017 0.5529 0.4100 0.0212 0.6538 44 1712 408 0.9211 0.5444 0.3510 -0.6178 -0.3461 45 1706 456 0.5831 0.5463 -0.0306 -0.8159 -0.1342 46 1637 449 0.9106 0.4758 0.3550 0.2356 0.7090 48 1632 345 0.9316 0.5545 0.5767 0.0821 -0.5333 50 1628 268 0.8204 0.5486 0.5195 0.1887 -0.4626 53 1610 156 0.8289 0.5093 0.1975 -0.6150 -0.3902 54 1484 187 0.8919 0.4919 0.6039 -0.0904 -0.5263 56 1494 255 0.8221 0.4449 0.5922 -0.2240 -0.4726 58 1511 336 0.9485 0.5336 0.6322 -0.0969 -0.5048 60 1516 405 0.7708 0.4488 0.5261 -0.2858 -0.4592 62 1523 461 0.8863 0.5776 0.5297 0.1210 -0.5074 73 1327 217 0.8515 0.2239 -0.1829 -0.7229 -0.4953 75 1340 255 0.9657 0.4569 0.3542 -0.7515 -0.2583 76 1347 277 0.9594 0.4919 0.3413 -0.7143 -0.3013 77 1361 308 0.9435 0.5056 0.3025 -0.7066 -0.3117 79 1376 368 0.8842 0.4629 0.4548 -0.5703 -0.3714 81 1389 425 0056311 C0;5156 0.4112 0.3585 -0.2601 82 1395 447 0.4272 0.4208 0.3700 0.3214 -0.0992 83 1315 452 0.7080 0.5021 0.4648 0.3889 -0.2975 85 1299 400 0.8192 0.6220 0.4597 0.0519 -0.4671 86 1288 373 0.9601 0.4509 0.2156 -0.8277 -0.1591 87 1274 333 0.9605 0.4222 -0.0439 -0.8824 -0.0395 88 1267 299 0.9329 0.4255 0.0923 -0.8519 -0.1329 89 1254 256 0.9344 0.4240 0.0187 -0.8541 -0.1571 93 1112 217 0.7327 0.6327 0.4445 0.1576 0.3317 96 1150 320 0.8505 0.2814 -0.3752 -0.7937 -0.0240 97 1159 341 0.9404 0.3855 -0.5748 -0.6725 -0.0956 98 1170 379 0.9360 0.4517 -0.2661 -0.8318 -0.0221 100 1199 452 0.8339 0.7412 0.2708 -0.1849 -0.4206 102 1220 498 0.9727 0.6179 0.2389 -0.6690 -0.2936 103 1182 543 0.9925 0.6313 0.0142 -0.7520 -0.1680 104 1171 622 0.5582 0.5624 -0.5552 -0.5749 -0.0564 106 1125 550 0.9837 0.5508 -0.1427 -0.8086 -0.0790 108 1092 493 0.9768 0.6199 -0.0482 -0.7256 -0.2523 109 1077 484 0.9721 0.5234 -0.0597 -0.8124 -0.1858 111 1151 498 0.9812 0.5479 -0.0319 -0.8159 -0.1197 113 1119 446 0.9971 0.5408 -0.2040 -0.7973 -0.1654 114 1104 433 0.9632 0.4516 -0.2845 -0.8228 -0.0356 115 1028 393 0.7097 0.1816 -0.5369 -0.6230 0.0184 116 1051 360 118 1013 313 119 986 273 121 979 290 123 940 343 124 1004 392 125 1023 421 126 1034 463 127 1056 521 128 1066 556 129 1075 580 130 1080 596 131 1083 615 132 1090 629 133 1100 664 134 1110 697 135 1119 730 141 965 453 145 914 349 147 905 318 148 817 404 149 839 433 151 878 473 152 891 439 153 950 505 154 9914 516 156 960 575 158 1012 641 160 1066 709 161 1098 747 162 1066 848 163 1060 829 164 1047 814 165 1036 777 166 1014 753 167 989 712 168 972 676 169 951 640 170 930 606 171 892 583 175 851 536 182 955 774 183 970 806 184 980 836 185 993 859 186 1011 898 190 871 771 193 842 655 196 796 549 200 743 535 201 750 575 202 758 617 203 757 651 204 787 714 0.8788 -0.0980 0.9713 -0.2679 0.5780, 0.4056 0.7873 -0.4511 0.8640. -0.2186. 0.9804 -0.1410 0.9222 0.1511 0.9723 0.4666 0.9984 0.5219 0.9809 0.5052 0.5407 0.4584 0.9649 0.4745 0.9790 0.4866 0.9471 0.4668 0.9488 0.4235 0.9860 0.3853 0.9899 0.4753 0.9812 -0.2328 0.9604 -0.5474 0.8259 0.1586 0.8624 0.3471 0.7019 0.1680 0.9805 -0.6579 0.8550 -0.2139 0.5273 0.0494 0.9109 0.1910 0.8096 0.2605 0.9306 0.3090 0.9706 0.2032 0.9472 0.1091 0.9666 0.5075 0.9790 0.0812 0.8820 -0.0985 0.8206 -0.1783 0.8470 -0.2380 0.9288 -0.0698 0.9108 -0.1318 0.9460 0.2562 0.8530 0.2661 0.8982 0.2121 0.6295 -0.6443 0.9637- -0.5251 0.8900 -0.2999 0.8634 -0.1058 0.9308 -0.1126 0.7621 0.0368 0.9076 -0.6206 0.8051 -0.4337 0.8829 -0.5257 0.7978 -0.4885 0.8848 -0.4891 0.9040 -0.3861 0.9079 -0.3412 0.9021 -0.2765 -0.9229 -0.0769 -0.9406 0.0751 0.1967 -0.6116 -0.7392 : -0.1723 -0.8765 0.1990 -0.9718 -0.0866 -0.8746 -0.3599 -0.7187 -0.4825 -0.3356 -0.7627 -0.4241 -0.7357 -0.2829 -0.8059 -0.5863 -0.6284 -0.5909 -0.6256 -0.6112 -0.5951 -0.7629 -0.4293 -0.8467 -0.3344 -0.7468 -0.4461 -0.9578 0.0251 -0.7904 0.1635 0.4122 -0.7533 0.3670 0.1985 0.3335 0.2937 -0.7002 0.2145 -0.8892 -0.1286 -0.9376 -0.2027 -0.8958 -0.2604 -0.7822 -0.3569 -0.7978 -0.4416 -0.9444 -0.1673 -0.9529 0.0910 -0.7123 -0.4477 -0.9819 -0.0249 -0.9223 -0.0079 -0.8772 0.0726 -0.8456 0.2378 -0.9540 0.0021 -0.9371 0.0707 -0.8848 -0.3027 -0.8274 -0.3061 -0.8662 -0.3154 -0.4562 0.0727 -0.7703 0.2910 -0.8486 0.2609 -0.8362 0.3911 -0.9484 0.0467 -0.8388 0.2254 -0.6152 0.3706 -0.6984 0.3427 -0.6807 0.3693 -0.5989 0.4352 -0.6648 0.4419 -0.7753 0.3789 -0.8032 0.3675 -0.8706 0.2397 -0.1074 -0.0961 0.0276 -0.0877 -0.0914 -0.0928 -0.0699 -0.0732 -0.1782 -0.0673 -0.0331 -0.0327 -0.0411 -0.0389 -0.0565 -0.0933 -0.0854 -0.0945 -0.0970 -0.2517 0.7535 0.6901 -0.1065 -0.0444 -0.0677 -0.0649 -0.0510 -0.0602 -0.0976 -0.1379 -0.0351 -0.0882 -0.1472 -0.1186 -0.1369 -0.1101 -0.1017 -0.0769 -0.0627 -0.0589 -0.0298 -0.1001 -0.1088 -0.0022 -0.1270 0.0798 -0.0815 -0.1088 -0.0829 -0.1053 -0.0913 -0.1017 -0.1061 -0.1013 207 209 212 213 214 215 217 219 220 221 222 223 225 228 229 230 231 232 233 234 236 237 238 251 255 257 259 261 262 623 264 265 267 268 269 280 282 284 286 287 289 290 291 292 293 294 295 297 298 299. 300 301 302 303 305 808 825 758 744 735 725 716 704 .7703 693 676 666 657 639 646 643 647 656 661 664 668 679 639 565 455 466 498 511 515 516 520 526 544 554 453 386 373 363 353 280 303 316 320 325 329 334 336 336 341 350 362 366 290 280 268 796 843 901 864 830 793 745 696 685 644 580 532 489 649 680 693 703 735 764 783 810 850 885 575 451 566 643 677 701 719 730 759 832 870 876 552 476 447 414 420 525 590 611 637 649 676 683 702 720 766 818 848 832 773 704 Q. 9.25Q 0.9232 0.9.532 0.99.17 0.9.875 0.9802 0.9821 0.9674 0.7420 0.8225 0.5417 0.9076 0.9734 0.9463 0.5747 0.9281 0.9719 0.5870 0.9355 0.9522 0.9679 0.9946 0.7849 0.9690 0.6817 0.9640 0.8868 0.9837 0.9884 0.9237 0.9471 0.5646 0.5815 0.8035 0.8451 0.9654 0.9556 0.5894 0.9579 0.7023 0.9793 0.9841 0.9677 0.9797 0.9912 0.8065 0.7093 0.9747 0.99.76 0.8855 0.9708 0.8881 0.9738 0.9886 0.9671 -0.6657 -0.8014 -0.9221 -0.8250 -0.8690 -0.9209 -0.7112 -0.8280 -0.6999 -0.6841 -0.6689 -0.7363 -0.9381 -0.8042 -0.9350 -0.8800 -0.8536 -0.6549 -0.8093 -0.9419 -0.9484 -0.9179 0.3658 -0.7411 0.2802 -0.7903 -0.8770 -0.8933 -0.9218 -0.0562 -0.8709 -0.6842 -0.9167 0.2276 0.4661 -0.8886 -0.9462 -0.7645 0.4912 0.3531 -0.5289 0^.8942 -0.9203 -0.9497 -0.9232 0.0910 -0.2544 -0.9318 -0.9435 -0.9322 -0.8262 -0.8954 -0.8876 -0.9472 -0.9333 -0.5820 -0.4083 -0.1705 -0.4081 -0.3069. -0.1040 -0.5397 -0.4087 0.1154 -0.4718 H3.6142 -0.4067 -0.1059 -0.4038 -0.1554 -0.2067 -0.2843 -0.2190 -0.3318 -0.2108 0.0074 -0.2002 0.7352 -0.4863 0.7016 -0.4167 -0.0810 -0.2117 -0.1605 0.6957 -0.1394 0.0237 -0.1493 0.3863 0.6239 -0.2084 0.0741 0.0589 0.6609 0.3502 -0.0743 -0.2080 -0.1166 0.0514 -0.1209 0.4085 0.4332 -0.0628 -0.0777 -0.0197 0.2790 -0.0895 0.4152 -0.0469 -0.0366 0.3737 0.3321 0.2716 0.3865 0.3706 0.3453 0.4236 0.3343 0.3580 0.3581 0.3360 0.4434 0.2866 0.3648 0.2731 0.3322 0.4020 0.3318 0.4091 0.1366 0.2615 0.3343 0.3276 0.4230 -0.2472 0.4031 0.3331 0.3742 0.3355 0.3230 0.3770 0.2823 0.3447 0.1930 0.3336 0.3630 0.2315 -0.0356 0.0642 0.1559 0.3330 0.3755 0.3274 0.2727 0.3524 0.3607 0.3980 0.3201 0.3184 0.1230 0.3565 0.2791 -0.0695 0.2986 0.3078 -0.0594 -0.0625 -0.0051 -0.0408 -0.0271 0.0458 -0.0745 -0.0556 0.3328 -0.0607 -0.0641 -0.0579 -0.0034 -0.0586 -0.0415 -0.0262 -0.0300 -0.0083 -0.0560 -0.0439 0.0040 -0.0179 0.0564 -0.0671 0.2230 -0.0571 -0.0084 -0.0257 -0.0172 -0.5715 -0.1644 0.1272 -0.0117 0.7518 -0.3569 -0.0231 0.0337 0.0103 -0.5251 0.6563 0.0016 -0.0157 -0.0018 0.0273 -0.0094 0.7079 0.5464 0.0069 0.0035 0.0330 -0.2884 -0.0193 -0.0935 0.0081 0.0066 309 262 624 0.9100 -0.9062 Q.0682 0.2899. -0.0139 311 238 512 0.9099 -0.8951 -0.0842 0.3186 -0.0062 313 231 465 0.9.685 -0.5749 0.6058 -0.4699 -0.2240 315 234 433 0.9422: 0.5102 . 0.6765 -0.3269 -0.3434 317 186 501 0.9863 -0.9441 -0.0230 0.3068 0.0148 321 196 6~66" 0.8725 -0.9272 0.0617 0.0857 0.0405 326 200 762 0.9512 -0.9428 0.0106 0.2493 0.0109 327 204 796 0.9774 -0.9438 -0.0194 0.2935 0.0108 328 152 772 0.9978 -0.9819 0.0651 0.1681 -0.0326 329 144 727 0.8884 -0.9218 -0.0103 0.1929 0.0384 330 134 669 0.6653 -0.8808 -0.1183 0.2737 0.0249 331 129 618 0.9805 -0.9609 0.2088 0.1081 -0.0442 332 126 604 0.9713 -0.9706 0.0880 0.1416 0.0396 334 116 561 0.8372 -0.8995 -0.0271 0.1638 0.0222 335 112 531 0.9505 -0.9449 0.0334 0.2374 0.0148 336 103 502 0.9708 -0.9529 0.2347 0.0837 0.0247 337 94 479 0.4839 0.3963 0.4308 0.1796 0.3300 340 51 504 0.8148 0.1371 0.4360 0.2367 0.7415 341 50 516 0.8728 0.3139 0.5353 0.4727 0.5140 342 52 536 0.5519 -0.0938 0.3669 0.2155 0.6017 343 51 571 0.3360 -0.1983 0.5300 0.0971 -0.0796 345 53 621 0.9616 -0.9531 0.0085 0.2278 0.0355 347 53 653 0.2340 -0.3691 0.2992 -0.0357 -0.0836 349 73 707 0.9659 -0.9275 -0.0766 0.3157 0.0099 350 84 747 0.8707 -0.8684 -0.0942 0.3279 0.0127 351 98 802 0.9401 0.4595 0.6815 -0.0167 -0.5140 VARIANCE 38.533 26.534 16.769 6.371 CUM.VAR. 38.533 65.068 81.837 88.208 APPENDIX IICC) VARIMAX FACTOR SCORE MATRIX V a r i a b l e F a c t o r 1 2 3 4 -3 0. 3696 0 . 2322 0. 3023 0. 9824 -2 0 . 4612 0. 3413 0. 3716 1. 5604 -1 0. 4281 0. 3647 0. 3169 1. 5152 0 0. 5023 0. 3954 0. 3564 1. 5940 1 0. 7074 •0. 4225 0. 6392 1. 4985 2 0 . 7458 0. 4083 0. 8699 0. 3664 3 1. 1103 0. 8361 1. 4264 - 1 . 1315 4 0. 5822 1. 3087 - 0 . 4041 - 1 . 4183 5 0 . 3456 0. 4202 -2 . 6347 0. 4908 6 1. 0848 - 1 . 4298 - 1 . 6597 0 . 4203 7 1. 1419 -2 . 4323 0. 3517 -0 . 0960 8 - 0 . 4879 - 1 . 7505 1. 0208 - 0 . 1690 9 - 1 . 3772 -0 . 7239 0. 4024 0. 3097 10 - 1 . 7289 - 0 . 0147 0. 1690 0 . 4917 >10 - 1 . 9630 0. 2893 - 0 . 3108 0. 5590 286 APPENDIX I I I FRASER DELTA PROJECT At the time this, thesis, was i n i t s f i n a l stages of prepar— ation r e s u l t s from a study of the Fraser Delta were beginning to emerge. The delta study was. aimed at determining a sediment budget for the d e l t a f r o n t . Preliminary r e s u l t s i n d i c a t e that the d e l t a has been a c t i v e l y , and vigorously, eroded south of Sand Heads, i s i n a more or l e s s stable state between Sand Heads and North Arm, and i s growing seaward j u s t south of the North Arm Je t t y . While some of the material contributing to outgrowth of the delta near the North Arm Je t t y has been added a r t i f i c i a l l y by dredging North Arm (and pumping the t a i l i n g s to the south over the j e t t y ) , some must be added by longshore d r i f t of sandy material from the south. The d e l t a survey was conducted over the t i d a l f l a t s and upper d e l t a slopes, i n shallower water than that from which samples 70-1-82 and 70-1-83 (this thesis) were c o l l e c t e d . The soundings agree with sedimentological evidence obtained from samples 82 and 83, whose o r i g i n was interpreted as the r e s u l t of erosion of older delta sediments. APPENDIX IV SAMPLE LOCATIONS No. Latitude (°N) Longitude (°W) No. Latitude (°N) Longitude (°W) 1 48°56' 123°19.1 f 48 48°54.2' 123°04.1' 2 48°55.1' 123°17.8 t 123°16.4' 49 48°54.2' 123°05.0' 3 48°54.1' 50 48°52.1 r 123°05.9' 4 48°53.4' 123°15 T 51 48°57.3 t 123°06.6' 5 48°52.6' 123°13.7' 123 013.7 t 52 48°50.0 r 123°07.7' 6 48°52' 53 48°49.2' 123°09.1' 7 48°51.3' 123°11.4* 54 48°51.8 r 123°13.9' 8 48°51.1' 123°10.4' 55 48°52.6' 123°12.8' 9 48°50.8' 123°0855' ;;56 48°53.6' 123°12.0' 10 48°50.8 r 123°07' 57 48°54.4' 123°10.0' 11 48°50.8' 123°06.3' 58 48°55.7' 123°09.5' 12 48°5o.l' 123°04.3' 59 48°56.86 r 123°08.5' 13 48°49.2' 123°01.9' 60 48°57.6' 123°07.7' 14 48°48.8' 123°00.6' 61 48°58.28' 123°07.1' 15 48°48.3' . 122°59.0' 62 48°59.1' 123°06.25' 16 48°48.0' 122°59.3' 122°55.2' 63 49°00' 123°08.9' 17 48°47.4' 64 48°59.2' 123°09.9' 18 48°48.0' 122°54.5' 65 48°58.46' 123°11' 19 48°48.8' 122°53.3' 66 48°57.5' 123°12.1' 20 48 49.5' 122°53.0' 122°52.2' 67 48°56.8' 123°13' 21 48°50.1' 68 48°56.1' 123°13.9* 22 48°50.9' 122°51.6 T 69 48°55.1' 123°15.2' 23 48°51.9' 122°50.8' 70 48°53.6' 123°17' 24 48°53.1' 122°50.2' 71 48°53.2' 123°17.3' 25 48°54.08* 122°48.9* 72 48°52.8* 123°17.9' 26 48°55.5' 122°53.3' 73 48°54.9' 123°20' 27 48°54.8' 122°53.7' 74 48°55.4' 123°19.4' 28 48°54.9 f 122°54.3' 75 48°55.9' 123°18.6' 29 48°53.3' 122°55.0' 76 48°56.4' 123°17.9' 30 48°52.4' 122°55.8' 77 48°57.2' 123°16.7 T 31 48°52.1' 122°56.2' 78 48°58* 123°15.7' 32 48°51.9' 122°56.25' 79 48°58.6' 123°14.7' 33 48°51.1' 122°56.72' 80 48°59.3* 123°13.9* 34 48°50.35' 122°57.15' 81 49°00' 123°13' 35 48°49.55' 122°57.7' 82 49°00.6' 123°12' 36 48°48.3' 122°58.2' 83 49°01.9' 123°15.5* 37 48°47.8' 122°58.7' 84 49°01.4* 123°16.3' 38 48°47.4' 122°58.9' 85 49°006. ' 123°17.3' 39 48°50.9' 123°02.3' 86 48°59.9' 123°18.4' 40 48°50.5' 123°01.0' 87 48°59 r 123°20' 41 48°51.7' 123°00.8' 88 48°58.2' 123°20.9' 42 48°52.8' 123°00.2' 89 48°57.2' 123°22.4' 43 48°53.9 r 122 059.8' 90 48°56.6' 123°23.3' 44 48°55' 122°59.3 r 122°58.5' 91 48°56.3' 123°23.9' 45 48°56.3 r 92 48°55.8' 123°24.5' 46 48°57' 123°01.6' 93 48°58.1' 123°29.3' 47 48°55.3' 123°03.1' 94 48°58.9' 123°28.0' 288 No. Latitude (°N) Longitude (°W) 95 4 8 ° 5 9 . 4 ' 1 2 3 ° 2 7 . 2 ' 96 4 9 ° 0 0 . 4 ' 1 2 3 ° 2 5 . 6 * 97 4 9 ° 0 0 . 9 r 1 2 3 ° 2 4 . 7 * 98 4 9 ° 0 1 . 8 « 1 2 3 ° 2 3 . 4 ' 99 4 9 ° 0 2 . 6 ' 1 2 3 ° 2 2 . 3 ' 100 4 9 ° 0 3 . 3 ' 1 2 3 ° 2 0 . 5 5 r 101 4 9 ° 0 4 . 1 ' 1 2 3 ° 1 9 . 6 f 102 4 9 ° 0 4 . 5 5 ' 1 2 3 ° 1 8 . 6 4 ' 103 4 9 ° 0 6 . 3 r 1 2 3 ° 1 9 . 3 ' 104 4 9 ° 0 8 . 7 t 1 2 3 ° 1 8 . 1 3 t 105 4 9 ° 0 7 . 9 ' 1 2 3 ° 2 0 . 3 ' 106 4 9 ° 0 7 . 3 ' 1 2 3 ° 2 1 . 7 t 107 4 9 ° 0 6 . 8 5 ' 1 2 3 ° 2 3 . 3 ' 108 4 9 ° 0 6 . 2 5 ' 1 2 3 ° 2 3 . 3 ' 109 4 9 ° 0 6 . 2 * 1 2 3 ° 2 5 . 2 ' 110 4 9 ° 0 5 . 9 ' 1 2 3 ° 2 0 . 6 ' 111 4 9 ° 0 5 . 5 ' 1 2 3 ° 2 1 . 7 ' 112 4 9 ° 0 5 ' 1 2 3 ° 2 3 . 1 ' 113 4 9 ° 0 4 . 5 r 1 2 3 ° 2 4 . 2 ' 114 4 9 ° 0 4 . 3 ' 1 2 3 ° 2 5 . 1 ' 115 4 9 ° 0 3 . 6 ' 1 2 3 ° 2 7 . 1 ' 116 4 9 ° 0 3 ' 1 2 3 ° 2 9 ' 117 4 9 ° 0 2 . 5 ' 1 2 3 ° 3 0 . 5 ' 118 4 9 ° 0 2 . 2 ' 1 2 3 ° 3 1 . 6 r 119 4 9 ° 0 1 . 4 ' 1 2 3 ° 3 3 . 7 ' 120 4 9 ° 0 1 . 3 r 1 2 3 ° 3 4 . 8 ' 121 4 9 ° 0 2 . 0 ' 1 2 3 ° 3 3 . 6 ' 122 4 9 ° 0 2 . 7 ' 1 2 3 ° 3 2 . 8 ' 123 4 9 ° 0 3 . 4 ' 1 2 3 ° 3 2 . 0 r 124 4 9 ° 0 4 . 6 ' 1 2 3 ° 3 0 . 3 ' 125 4 9 ° 0 5 . 2 ' 1 2 3 ° 2 8 . 9 * 126 4 9 ° 0 6 . 2 ' 1 2 3 ° 2 7 . 5 ' 126(2) 4 9 ° 0 6 . 0 ' 1 2 3 ° 2 7 . 1 ' 127 4 9 ° 0 7 . 5 ' 1 2 3 ° 2 5 . 3 ' 128 4 9 ° 0 8 . 3 ' 1 2 3 ° 2 4 . 3 r 129 4 9 ° 0 8 . 9 ' 1 2 3 ° 2 3 . 2 * 130 4 9 ° 0 9 . 3 ' 1 2 3 ° 2 2 . 7 ' 130(2) 4 9 ° 0 8 . 9 * 1 2 3 ° 2 2 . 2 ' 131 4 9 ° 0 9 . 7 ' 1 2 3 ° 2 2 ' 132 4 9 ° 1 0 . 1 « 1 2 3 ° 2 1 . 4 * 133 4 9 ° 1 0 . 9 ' 1 2 3 ° 2 0 . 3 ' 134 4 9 0 1 1 . 7 ' 1 2 3 ° 1 9 . 1 ' 135 4 9 ° 1 2 . 5 ' 1 2 3 ° 1 8 ' 136 4 9 ° 1 0 . 1 ' 1 2 3 ° 2 4 . 5 ' 137 4 9 ° 0 9 . 6 * 1 2 3 ° 2 5 . 3 ' 138 4 9 ° 0 9 ' 1 2 3 ° 2 6 . 5 ' 139 4 9 ° 0 8 . 3 ' 1 2 3 ° 2 8 * 140 4 9 ° 0 7 . 5 ' 1 2 3 ° 2 9 . 5 ' 141 4 9 ° 0 6 . 9 ' 1 2 3 ° 3 0 . 7 ' 142 4 9 ° 0 6 . 3 ' 1 2 3 ° 3 1 . 9 * 143 4 9 ° 0 5 . 7 ' 1 2 3 ° 3 2 . 9 * 144 4 9 ° 0 5 . 1 * 1 2 3 ° 3 3 . 6 ' No. Latitude (°N) Longitude ( 145 4 9 ° 0 4 . 7 ' 1 2 3 ° 3 5 . 2 ' 146 4 9 ° 0 4 . 2 ' 1 2 3 ° 3 5 . 8 ' 147 4 9 ° 0 3 . 9 ' 1 2 3 ° 3 6 . 3 ' 148 4 9 ° 0 7 . 6 ' 1 2 3 ° 3 8 . 2 ' 149 4 9 ° 0 8 . 1 ' 1 2 3 ° 3 6 . 0 * 150 4 9 ° 0 8 . 3 f 1 2 3 ° 3 4 . 9 * 151 4 9 ° 0 8 . 7 ' 1 2 3 ° 3 4 . 0 T 152 4 9 ° 0 9 . 0 ' 1 2 3 ° 3 3 . 1 ' 153 4 9 ° 0 9 . 2 ' 1 2 3 ° 3 2 . 2 ' 154 4 9 ° 0 9 . 4 * 1 2 3 ° 3 1 . 7 ' 155 4 9 ° 0 9 . 9 ' 1 2 3 ° 2 9 . 6 ' 156 4 9 ° 1 0 . 4 ' 1 2 3 ° 2 8 . 4 ' 1574 o 4 9 ° n » 1 2 3 ° 2 6 . 5 * 158 4 9 0 1 1 . 5 , 1 2 3 ° 2 4 . 7 ' 159 4 9 ° 1 2 . 2 ' 1 2 3 ° 2 2 . 4 ' 160 4 9 ° 1 2 . 7 ' 1 2 3 ° 2 0 . 8 ' 161 4 9 ° 1 3 . 3 ' 1 2 3 ° 1 8 . 6 ' 162 4 9 ° 1 6 . 6 ' 1 2 3 ° 1 7 . 9 ' 163 4 9 ° 1 6 . 2 ' 1 2 3 ° 1 8 . 5 ' 164 4 9 ° 1 5 . 9 ' 1 2 3 ° 1 9 . 4 ' 165 4 9 ° 1 5 . 1 ' 1 2 3 ° 2 0 . 6 ' 166 4 9 ° 1 4 . 7 ' 1 2 3 ° 2 2 . 1 ' 167 4 9 ° 1 3 . 8 ' 1 2 3 ° 2 4 . 1 ' 168 4 9 ° 1 3 . 2 ' 1 2 3 ° 2 5 . 5 ' 169 4 9 ° 1 2 . 4 ' 1 2 3 ° 2 7 . 2 ' 170 4 9 ° 1 1 . 7 ' 1 2 3 ° 2 8 . 9 ' 171 4 9 ° 1 0 . 7 ' 1 2 3 ° 3 1 . 0 ' 172 4 9 ° 0 9 . 1 ' 1 2 3 ° 3 7 . 2 ' 173 4 9 ° 0 9 . 6 ' 1 2 3 ° 3 6 . 2 ' 174 4 9 ° 1 0 ' • 1 2 3 ° 3 5 . 4 ' 175 4 9 ° 1 0 . 8 * 1 2 3 ° 3 3 . 9 ' 176 4 9 ° 1 1 . 4 ' 1 2 3 ° 3 3 ' 177 4 9 ° 1 2 . 3 ' 1 2 3 ° 3 1 . 2 ' 178 4 9 ° 1 3 . 1 * 1 2 3 ° 2 9 . 6 ' 179 4 9 ° 1 4 . 1 ' 1 2 3 ° 2 7 . 9 ' 180 4 9 ° 1 4 . 8 ' 1 2 3 ° 2 6 . 4 ' 181 4 9 ° 1 5 . 7 ' 1 2 3 ° 2 4 . 8 ' 182 4 9 ° 1 6 . 1 ' 1 2 3 ° 2 4 . 2 ' 183 4 9 ° 1 6 . 8 ' 1 2 3 ° 2 2 . 9 ' 184 4 9 ° 1 7 . 5 * 1 2 3 ° 2 1 . 8 ' 185 4 9 ° 1 8 . 0 ' 1 2 3 ° 2 0 . 7 * 186 4 9 ° 1 8 . 8 ' 1 2 3 ° 1 9 . 1 ' 187 4 9 ° 1 9 . 8 r 1 2 3 ° 2 4 . 4 * 188 4 9 ° 1 8 . 9 ' 1 2 3 ° 2 5 . 5 ' 189 4 9 ° 1 8 . 2 ' 1 2 3 ° 2 6 . 5 ' 190 4 9 ° 1 7 . 2 5 * 1 2 3 ° 2 8 . 2 ' 191 4 9 ° 1 6 . 4 ' 1 2 3 ° 2 9 . 3 ' 192 4 9 ° 1 5 . 7 ' 1 2 3 ° 3 0 . 5 * 193 4 9 ° 1 4 . 4 * 1 2 3 ° 3 1 . 6 ' 194 4 9 ° 1 3 . 3 T 1 2 3 ° 3 4 ' 195 4 9 ° 1 2 . 2 ' 1 2 3 ° 3 5 ' 196 4 9 ° 1 2 ' 1 2 3 ° 3 6 ' 289 No. Latitude (°N) Longitude ( 197 49°10' 123°41.8' 198 49°10.6' 123°41.2' 199 49°11.5' 123°39.9' 200 49 °12. 3 r 123°38.7' 201 49°13.5 V I23°37.4' 202 49°14.5' 123°36.1' 203 49°15.3* 123°35.0' 204 49°16.8' 123°32.8' 205 49°17.4' 123°32.0' 206 49°18.3' 123°31.2' 207 49°18.8' 123°30.1' 208 49°19.3' 123°29.5' 209 49°19.9* 123°28.4' 210 49°20.4* 123°28.1' 211 49°20.7' 123°26.7* 212 49°22.5' 123°29.9' 213 49°21.7' 123°31.4' 214 49°20.8* 123°32.6* 215 49°19.9' 123°33.8' 216 49°19.4' 123°34.3' 217 49°18.7' 123°35.2' 218 49°18' 123°36.1' 219 49°17.5' 123°36.8* 220 49°17.2' 123°37.1' 221 49°16.2' 123°38.4' 222 49°14.6' 123°40.5' 223 49°13.4' 123°42.0' 224 49°12.9 T 123°42.5' 225 49°12.3' 123°43.3" 226 49°11.5' 123°44.2' 227 49°10.7 T 123°45.3 ? 228 49°17.1' 123°40.6' 229 49°12.9* 123°39.6' 230 49°18.3 T 123°39.9' 231 49°18.5' 123°39.1' 232 49°19.3' 123°38' 233 49°20' 123°37.2' 234 49°20.5' 123°36.6' 235 49°21' 123°36.3* 236 49°21.2' 123°35.9' 237 49°22.2' 123°34.5' 238 49°23.8' 123°35.5* 239 49°23.4' 123°36' 240 49°22.6' 123°37.1' 241 49°21.8' 123°38.2' 242 49°21.55' 123°38.4' 243 49°21' 123°39.1' 244 49°20.3* 123°40.2* 245 49°19.5 T 123°41.1' 246 49°19.2 r 123°41.2 r 247 49°18.7* 123°42.1' 248 49°17.8' 123°43.2' No. Latitude (°N) Longitude (°W) 249 49°17.5' 123°43.6* 250 49°17.1 l 123°44.1' 251 49°16.1' 123°45.4' 252 49°14.7 r 123°47.3' 253 49°14' 123°48' 254 49°12.9 T 123°49.6' 255 49°14.1' 123°52.9* 256 49°15.4' 123°51.1' 257 49°17.2' 123°48.9' 258 49°18.5' 123°47.3' 259 49°18.9 r 123°46.9' 260 49°19.1* 123°46.6' 261 49°19.7' 123°45.6' 262 49°20.3' 123°44.9' 263 49°20.8' 123°44.4' 264 49°21.05 T 123°44.05' 265 49°21.8' 123°43.1' 266 49°22.6' 123°92.1' 267 49°23.6' 123°40.7' 268 49°24.6' 123°39.5' 269 49°26.1' 123°43.7' 270 49°25.0' 123°44.8' 271 49°24.7' 123°45.6' 272 49°24.1' 123°46.1' 273 49°23.1' 123°47.3' 274 49°22.6' 123°47.9' 275 49°21.7' 123°49' 276 49°21' 123°50' 277 49°20' 123°51.1' 278 49°19V7 r 123°51.6' 279 49°10.4' 123°52.2' 280 49°17.92' 123°53.7* 281 49°16.5' 123°55.4' 282 49°16' 123°55.95' 283 49°15.7' 127°56.3* 284 49°15.3 f 123°57' 285 49°14.8 T 123°57.4' 286 49°14.5' 123°58.1' 287 49°15.7' 124°01.1' 288 49°16.9* 123°59.7' 289 49°18.4' 123°57.9' 290 49°20' 123°55.9* 291 49°20.55' 123°55.3' 292 49°21.15 t 123°54.5' 293 49°21.5 r 123°54.1' 294 49°22.2' 123°53.3' 295 49°22.35' 123°53.11' 296 49°22.7' 123°53.1' 297 49°22.9' 123°52.6' 298 49°23.3' 123°52.0» 299 49°24.5' 123°50.6' 300 49°25.8* 123°49.0* 290 No. Latitude (°N) Longitude (°W) No. Latitude (°N) Longitude (°W) 301 49°26.5' 123°48.1* 330 49°24.8' 124°02.2* 302 49°27.2 t 123°51.8 l 331 49°23.5' 124°03.5* 124°04' 303 49°25.6' 123°53.5 l 332 49°23.1« 304 49°24.5* 123°54.8' 333 49°22.6* 124°04.7 T 305 49°23.9' 123°55.5' 334 49°22* 124°05.3' 306 29°23.2' 123°55.5' 335 49°21.2* 124°06.1' 307 49°23* 49°22.1» 49°21.7' 123°56.6' 336 49 O20.5 r 124°07.1' 308 123057.5* 337 49°20' 124°08' 309 123°58.5' 338 49°19.7' 124°09.5' 310 49°20.85' 123°58.9* 339 49°19.5' 124°11.6' 311 49°18.9' 124°01.0' 124°01.8' 340 49°21.3' 124°09.3' 312 49°18.2' 341 49°21.7' 124°09.1 T 313 49°17.2' 124°02.3' 342 49°22.2' 124°08.6' 314 49°17.4» 124°02.8 t 343 49°23.2' 124°07.9' 315 49°16.7' 124 O02.9' 344 49°24.0' 124°07.2' 316 49°18.9* 124°03.9' 345 49°24.6' 124°06.8' 317 49°19.3* 124°03.5' 346 49°25.2' 124°06.1' 318 49°21' 124°02« 347 49°25.5' 124°06.0' 319 49°22.2' 124 o00.9' 348 49°25.7' 124°05.3' 320 49°22.85' 124°00.4' 349 49°26.7' 124°04.0' 321 49°23.8' 123°59.5' 350 49°27.7' 124°02.6' 322 49°24.87' 123°58.6' 351 49°29.0' 49°21.9' 124°00.8' 323 49°25.5' 123°58' 352 123°47.1' 324 49°25.8' 123°51.8' 353 49°21.6' 123°46.3' 325 49°26* 123°57.7' 354 49°21.1' 123°45.3' 326 49°26.5' 123°57.3' 355 49°20' 123°43.3' 327 49°27.3' 123°56.4' 356 49°19.6' 123°42.3' 328 49°27.4' 123°59.2' 357 49°18.7' 123°40.4' 329 49°26.3' 124°00.J5' 358 49°17.8' 123°38.6' FIGURE 2 B A T H Y M E T R Y LIMES OF PROFILES CONTOUR INTERVAL TIDAL FLATS 4 A' 20 METRES S A M P L E L O C A T I O N S SAMPLE NUMBERS ONLY GIVEN, FULL IDENTIFICATION IS 70-1-1SAMPU ItoJ. REFERS TO 10.U.I.C. CRUISE k, 71-1. SYMBOL '123 SAMPLE No. ANAtrSEO SAMPLES ARE UNDERLINED , G E O G R A P H I C F E A T U R E S NAMES ARE FROM TIFFIN IttSSI. BOREHOLES C E N T R A L A N D S O U T H E R N STRAIT OF GEORGIA N A U I I C A L M I I I S 

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