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Geological setting and surficial sediments of Fatty Basin, a shallow inlet on the west coast of Vancouver… Wiese, Wolfgang 1971

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GEOLOGICAL SETTING AND SURFICIAL SEDIMENTS  OF FATTY BASIN, A SHALLOW INLET ON  THE WEST COAST OF VANCOUVER ISLAND,  BRITISH COLUMBIA WOLFGANG WIESE B.Sc, University of B r i t i s h Columbia, 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Geology We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1971 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 a t 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 , 1 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 & e o I o 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 Ap + U. 28 , /9VI ABSTRACT Fatty Basin and Useless Inlet r e s u l t from modification by water and ice erosion of depressions caused by Early Tertiary f a u l t i n g . U p l i f t of the land due to p o s t - g l a c i a l rebound i s i n excess of 6 m (20 f t ) for the l a s t 7000 years. Shallow entrance s i l l s cause the i n l e t s to act as traps for organic detritus brought i n by t i d a l action. The rate of deposition of fine-grained suspended debris i s i n the range of 900 g/m /year, with maximum deposition during l a t e summer, when phytodetritus i s most abundant. Five sedimentary environments exist i n Fatty Basin, namely mud zones, rock slopes, beaches, deltas, and zones of strong currents. In addition to boulder accumulations and bedrock exposures, general categories of sediments are pebbles and gravels, t e r r e s t r i a l sands, s h e l l debris, muds, and shell-gravel mixtures. S t a t i s t i c a l analysis of the size d i s t r i b u t i o n of 125 samples resulted i n recognition of 8 groups of sediments , which were then subdivided into 13 types on the basis of composition and grain shape. Olive-green mud r i c h i n organic matter covers almost three-quarters of the bottom surface i n the Basin. Coarse t e r r e s t r i a l sands are derived mainly from bedrock exposures within about 300 f t of the shore , whereas most of the fine sands, s i l t s , and clays originate from g l a c i a l sediments. The source area for g l a c i a l debris i s i n the Henderson Lake region, under-l a i n dominantly by Karmutsen basalts. S h e l l debris, notably barnacle plates and calcareous worm tubes, i s e s s e n t i a l l y confined to the rock-slope i i i environment, where i t accumulates i n a narrow zone along the base of steep slopes. The rock-slope environment represents a preferred habitat f o r l o b s t e r s , because i t offers better shelter and food supply than the other environments. In Fatty Basin, the t o t a l area most suitable to lobsters amounts to about 3 8 , 0 0 0 m^  (= J% of the bottom surface), i n Useless I n l e t , t h i s area covers 1 3 5 , 0 0 0 m (= 5% of the bottom surface). TABLE OF CONTENTS Chapter P a S e I. INTRODUCTION 1 1. Nature and Objective of Study 1 2. F i e l d and Laboratory Work 2 3. Previous Work 4 I I . THE SETTING 5 1. Geomorphology 5 2. Pre-Pleistocene Geology 8 3. Origin of the Inlets 12 4. G l a c i a l History 15 5. Physical Oceanography 17 I I I . THE SEDIMENTS 21 1. Rate of Sedimentation 21 2. Clay Mineralogy 23 3. Heavy Minerals 2 6 k. Delta Developments 32 5. Sediments i n Fatty Basin, Useless I n l e t , and Rainy Bay • 37 6 . Sediment D i s t r i b u t i o n h5 A. Boulders , ^ B. Pebbles and Gravels " 4 6 " ( i ) Mostly angular, coarse gravel with few s h e l l fragments 4D" i i i i v Chapter Page ( i i ) Rounded pebbles and gravel k"J C. T e r r e s t r i a l Sands U8 ( i ) Medium to fine sand 1*8 ( i i ) Coarse sand with abundant gravel U8 ( i i i ) Coarse sand with some gravel, pebbles, and sh e l l s ^9 D. Shell Debris ^9 ( i ) Coarse s h e l l debris with few t e r r e s t r i a l fragments h9 ( i i ) Medium-sized s h e l l debris, very muddy and with abundant t e r r e s t r i a l gravel 5 0 ( i i i ) Fine to very f i n e shell-hash 5 1 E. Muds 5 1 ( i ) Olive-green mud r i c h i n organic matter 5 1 ( i i ) Olive-green mud with abundant small s h e l l -fragments 5 U ( i i i ) Grey mud 5 ^ F. Coarse Shell-Gravel Mixtures 5 5 ( i ) Coarse, muddy mixture of shell s with gravel and sand 5 5 ( i i ) Muddy, very coarse gravel (angular)-shell mixture 5 5 7 . Lithology of the Sediments 5 6 ( i ) Sediment Colours 5 6 Chapter Page ( i i ) Grain Shape and Roundness 57 ( i i i ) Surface Textures 58 8. Effects of the Fauna upon Sedimentation 60 9. Organic Carbon D i s t r i b u t i o n 63 10. Nature and D i s t r i b u t i o n of the Shell-bearing Fauna .... 66 IV. SUMMARY AND CONCLUSIONS 71 1. The Setting 71 2. The Sediments • 75 ( i ) Rate of Sedimentation 75 ( i i ) Clays and Heavy Minerals 75 ( i i i ) Nature and D i s t r i b u t i o n of Sediments ... 76 (iv) Sedimentary Environments 8 l (v) Organic Carbon 8U (vi) Shell-bearing Fauna 85 3. General Conclusions , 87 V. BIBLIOGRAPHY 90 VI. APPENDICES 93 1. Appendix 1 91* ( i ) Size analysis 9^ ( i i ) Heavy minerals 95 ( i i i ) Clay minerals 95 (iv) Organic carbon 95 (v) Rocks 96 (vi) Shell-bearing fauna 96 2. Appendix 2 (Tables) 97 LIST OF FIGURES F i glare Page 1. General Location 1 - 2 2. Locations of Bottom P r o f i l e s T - 8 3. Bottom P r o f i l e s 7 - 8 • b. Bottom P r o f i l e s 7 - 8 5. Geology 11 - 12 6. Locations of Faults and Fracture Zones lb - 15 7. Frequency Rose of Fault Directions .. ." 1^ - 15 8. Temperature and S a l i n i t y D i stributions 20 - 21 9. Dissolved Oxygen Dis t r i b u t i o n s 20 - 21 10. Rates of Sedimentation 22 - 23 11. Heavy Mineral Percentages 29 - 30 12. Deltas 36 - 37 13- Cumulative Curve Groups 37 - 38 Ik. Sediment Types ••• • •• 37 - 38 15. Symbols for Sediment Types as used on Diagrams bl - b2 16. Grain-Size-Nomenclature Triangle h i - b2 17. Plots of Mean versus Deviation and Skewness; Plot of Skewness versus Deviation bl - b2 18. Plots of Skewness versus Kurtosis bl - b2 19. Organic Carbon D i s t r i b u t i o n 63 -6b 20. Variation of pH-values with Depth 6 5 - 6 6 21. D i s t r i b u t i o n of Main Shell-bearing Fauna 68 - 69 v i LIST OF TABLES Table Page 1. Weight Percentages of Heavy Minerals 30 2. Weight Percentages of Light Minerals 31 3. Measures of S t a t i s t i c a l Parameters 42 k. Ranges of S t a t i s t i c a l Parameters Within Sediment Groups 43 5. True Surface Areas of Sediment Types 44 6. Organic Carton Contents 6U 7. Bivalves and Univalves 67, 68 8. Foraminifera 70 9. C o l l e c t i o n Dates of Sedimentation Bowls 98, 99 10. S t a t i s t i c a l Parameters and Percentages of Gravel, Sand, and Mud 100-104 v i i LIST OF PHOTOGRAPHS Photograph Page 1. View of Fatty Basin towards West b - 5 2. View across Fatty Basin towards Worth b - 5 3. View across Fatty Basin towards South-West b - 5 b. A e r i a l view of Worth-Western Shore of Fatty Basin b - 5 5. View into Outer Section of Useless Inlet from Junction Passage b - 5 6. View of Rainy Bay b - 5 7. View of the Big Gut 20 - 21 8. View of the Small Gut 2 0 - 2 1 9. View of Ridge South of Fatty Basin 3 6 - 3 7 10. View of South-Delta i n Fatty Basin 3 6 - 3 7 11. View of Worth-Delta i n Fatty Basin 3 6 - 3 7 12. Outcrop of Organic Material on Oyster Beach 36 - 37 13. Rounded Pebbles 55 - 56 lb. Coarse, Angular Gravel 55 - 56 15. Gravelly Sand 55 - 56 16. Shell Debris 55 - 56 17- Small Shear Zone 70 - 71 18. Large G l a c i a l Groove 70 - 71 19. Base of Bedrock Slope 70 - 71 20. Green Mud 70 - 71 v i i i i x Photograph Page 21. Pebbles and Gravel 70 - 71 22. S h e l l Accumulations 70 - 71 LIST OF MAPS Map 1. Sample Locations i n Fatty Basin 2. Sample Locations i n Useless Inlet and Rainy Bay 3. Bathymetry of Fatty Basin h. Bathymetry of Useless Inlet 5. Sediment D i s t r i b u t i o n i n Fatty Basin 6. Sediment D i s t r i b u t i o n i n Useless Inlet and Rainy Bay x ACKNOWLEDGMENTS The writer i s indebted to the Nanaimo B i o l o g i c a l Station of the Fisheries Research Board of Canada for making t h i s work possible. In p a r t i c u l a r , Dr. R. Ghelardi and Mr. C. Shoop, who both i n i t i a t e d t h i s study, gave invaluable advice and assistance on numerous occasions. Other s c i e n t i s t s of the B i o l o g i c a l Station kindly provided much useful i n f o r -mation on the ecologic and oceanographic c h a r a c t e r i s t i c s of Fatty Basin. Dr. R.L. Chase of the geology department of the University of B r i t i s h Columbia, fellow graduate student John Luternauer, and former graduate student Lio n e l Carter offered many h e l p f u l discussions and constructive advice. Dr. B. Cameron of the Geological Survey of Canada kindl y i d e n t i f i e d the foraminifera. The writer i s grateful to Mr. and Mrs. Charles H i l l , who made l i f e i n the Fatty Basin camp enjoyable and the summer 196*9 a most memorable one, and to Miss Elizabeth Amezcua for typing the f i n a l draft of t h i s t h e s i s . x i INTRODUCTION 1. Nature and Objective of Study Fatty Basin i s located i n the northeast corner of Barkley Sound on the vest coast of Vancouver Island, near the head of Useless Inlet and just north of the entrance into Alberni Channel (Figure l ) . In 19^b, the Basin was chosen by the Fisheries Research Board of Canada as a suitable s i t e for a lobster transplant experiment, to be conducted by the Nanaimo B i o l o g i c a l Station. A permanent camp and hatchery were constructed, and i n I965 the f i r s t lobsters were introduced into Fatty Basin. Numerous and intensive studies have been carried out since that time, mostly concerned with the ecologic and oceanographic c h a r a c t e r i s t i c s of the Basin and neighboring i n l e t s . The present investigation on the geo-l o g i c a l environment of Fatty Bassin and Useless Inlet i s one of a series on a l l important aspects of the lobster habitat. Furthermore, i t i s an attempt to recognize c h a r a c t e r i s t i c s of marine sedimentation within these shallow i n l e t s , and to r e l a t e them to simi l a r coastal features i n B r i t i s h Columbia and strongly glaciated areas elsewhere. 1 4r58' 125W 2 2. F i e l d and Laboratory Work Sediment samples were collected from boats provided by the Fisheries Research Board at the Fatty Basin s t a t i o n , which included: ( i ) A diesel-powered work boat of about 15 f t length, equipped with a small hydraulic winch; ( i i ) a flat-deck boat, consisting e s s e n t i a l l y of a f l o a t i n g platform powered by a small outboard motor; ( i i i ) a small speed-boat; (iv ) a row boat. Most of the bottom sampling was done with a miniature version of a Pettersson grab sampler. A small snapper was also used, but proved unsatisfactory on many occasions. Coring was f i r s t attempted with a small Phleger gravity corer. Because of unsatisfactory r e s u l t s , e specially i n soft muds, coring was then done by hand during Scuba-dives, with only a p l a s t i c core l i n e r which was pushed and rotated into soft sediments. Cores up to 2 feet i n length were obtained t h i s way. Many surface sediment samples were collected by hand during Scuba- and skin-diving excursions. This method allowed excellent observation of the sediments 'in s i t u ' as well as selective and repre-sentative sampling. Positioning of sample locations i n Fatty Basin was done i n a s i m i l a r l y unconventional way. A strong (120 lbs p u l l ) f i s h i n g l i n e , with small p l a s t i c f l o a t s attached at 30 f t i n t e r v a l s , was extended 3 from f i x e d shore points. At the end of the l i n e , a larger f l o a t attached to a heavy anchor kept the l i n e straight and i n a steady p o s i t i o n , and a subsequent compass reading gave i t s correct bearing. The boat was then moved along the l i n e , and samples were taken next to each of the p l a s t i c f l o a t s . Accurate positioning of sample s i t e s to within a few feet was assured by t h i s method. In the less protected and deeper waters of Rainy Bay and Useless I n l e t , however, stronger winds and currents usually prevented such accurate positioning. Consequently, locations of sample s i t e s here were determined mostly by compass readings from the boat to various f i x e d shore points, with the r e s u l t s estimated to be accurate to within a few tens of feet. An attempt was made to determine the sedimentation rate and i t s variations i n Fatty Basin throughout a f u l l year. Four sediment bowls (glass j a r s , opening diameter 7.3 cm, height 18.5 cm) were placed 2 feet above the bottom at four locations within Fatty Basin (Map No. l ) , where they were exchanged at approximately monthly in t e r v a l s by FRB-personnel. Echosounding runs were done with the "Decibar", a research vessel of the Fisheries Research Board, which i s about 30 f t long and probably the largest ship able to enter Useless Inlet and Fatty Basin through the shallow and narrow passages. Rocks and geologic structures were studied along the shore-l i n e s from a boat, and also during several foot traverses along prominent ridges i n the area. The study of structures was aided by a e r i a l photo-graphs (l/U mile to the in c h ) , available for the entire area. 1+ Laboratory work involved sieving and hydrometer methods for grain-size analysis; separation and study of heavy minerals; i d e n t i f i c a t i o n of clay minerals; determination of organic carbon contents; i d e n t i f i c a t i o n of the major shell-bearing fauna. Detailed accounts of the methods used are presented i n the appendix. 3. Previous Work Previous investigations i n the area under consideration were concerned mainly with the b i o l o g i c a l and physical oceanography of Fatty Basin. They were carried out by the Fisheries Research Board of Canada as part of the lobster transplant project since 196k. In early 1969> the Canadian Hydrographic Service conducted a depth survey of Fatty Basin on a 30-ft g r i d pattern. Results of that survey were used i n t h i s study for preparation of a bathymetric map of Fatty Basin. In 1970, Carter completed a PhD-thesis on the s u r f i c i a l s e d i -ments i n Barkley Sound, which borders the presently studied area. Frequent comparison of res u l t s proved h e l p f u l to recognize sedimentation character-i s t i c s exclusive to the r e s t r i c t e d environments of Fatty Basin and Useless I n l e t . View of Patty Basin towards west. The camp i s v i s i b l e i n the background centre, reefs 2 and 3 appear j u s t below the water surface, and reefs 1 and 4 form two islands i n the oackground. The object j u s t o f f the north-delta i s a small barge carrying lobster traps. The Big G-ut opens i n the background to the l e f t , the Small Gut i s hidden behind the b l u f f i n the l e f t centre. The picture was taken near the end of a f l o o d t i d e , and o f f the two guts, the now slowly inflowing waters cause a very smooth surface as comparea to the main part of the Basin. View across Patty Basin towards north. The large, U-shaped v a l l e y i n the f a r background i s now occupied by Henderson Lake 3 i View acroso ?atty Basin towards south-west. The narrow passage o~i the Small Gut, c o l l e c t i n g the Basin with Rainy Bay, i s c l e a r l y v i s i b l e i n the l e f t centre. Tzartus I s l a n d appears i n the f a r background l e f t , and the open expanse of Barkley Sound stretches i n the f a r background to the r i g h t . A e r i a l view of the north-western share of ffott., Bu. i n , witl, tlie camp i n the centre, reef 1 i n the foreground, reef 4 i n the f a r l e f t centre, and the north-delta (flooded) i n the r i g h t background. I View i n t o the Outer S e c t i o n of U s e l e s s I n l e t  from J u n c t i o n passage. Hi^h mountains o f the Vancouver I s l a n d Ranges are v i s i b l e i n the back-ground. View of Rainy Bay from a h i g h h i l l south-east of P a t t y B a s i n . THE SETTING 1 . Geomorphology Low, rounded, heavily forested h i l l s characterize the immediate v i c i n i t y of Fatty Basin, strongly r e f l e c t i n g the effects of heavy P l e i s t o -cene g l a c i a t i o n . Steep c l i f f s , i n most cases nearly v e r t i c a l , are common along the many f a u l t s and fracture zones cris s - c r o s s i n g the area. Along the NW-side of Useless Inlet and NE-shore of Uchucklesit Inlet and thus bordering the area of i n t e r e s t , mountains of the Vancouver Island Ranges (Holland, I 9 6 U ) r i s e steeply to over TOO m, whereas near Fatty Basin the maximum elevation i s only about 250 m. Most slopes are covered with heavy overburden, l a r g e l y due to extensive deposits of g l a c i a l d r i f t , confining rock outcrops to shorelines and f a u l t c l i f f s . Fatty Basin i s a shallow, bowl-shaped, elongate depression about 4000 f t ( 1 2 2 0 m) long, up to 2 0 0 0 f t ( 6 1 0 m) wide, and 104 f t (32 m) deep. Connection with the ocean i s through two narrow passages, the "guts". The Big Gut, between the Basin and Useless I n l e t , i s about 9 0 0 f t ( 2 7 5 m) long, of about 1 2 0 f t ( 3 7 m) average width (with a minimum width of only 2 0 f t at the very narrow NW-end), and with about 3 f t ( l m) average depth at low t i d e s . The Small Gut, between the Basin and Rainy Bay, i s about 8 0 0 f t (244 m) i n length, averages 3 5 f t ( l l m) i n width, and h f t ( 1 . 2 m) i n depth at low tides (the NE-end into the Basin, however, i s completely exposed at very low tides.'). 5 Two small, rocky i s l a n d i n the Basin r i s e above high-tide l e v e l and two more are exposed at low t i d e s . A l l are referred to as "reefs" here. Five other rock exposures within the Basin r i s e only a few feet above the muddy bottom, but are nevertheless f a i r l y extensive. The camp i s located on an outcrop extending from the shore into the Basin, and i s forming an i s l a n d at high t i d e s . The maximum depth of about 10h f t (32 m) i s reached i n one of two deep depressions ("holes") just o f f the Small Gut, which act as traps for coarse debris being swept into the Basin through the two guts. Fresh water inflow i s maintained by three permanent creeks, which debouch at the north and south ends and the north-eastern side of the Basin, and by several seasonal creeks and t r i c k l e s , whose mouths l i e mostly along the eastern shore. Useless Inlet may be separated into three parts, which are named here the Outer, the Central, and the Inner Section, a l l d i f f e r i n g d i s t i n c t l y from each other. In the Outer Section (Plate I I I , Photograph Wo. 5), the i n l e t i s of the f j o r d type common to the west coast of Vancouver Island (e.g. Effingham I n l e t , Pipestem I n l e t ) . A straight channel of about 5500 f t (l6T8 m) length extends from the i n l e t mouth to the Central Section. The NW-shore i s very straight and steep, but the SE-shore has a gentler slope and i s dissected by many small bays. Here, several almost v e r t i c a l c l i f f s t r i k e nearly at r i g h t angles to the general shoreline d i r e c t i o n . The bottom topography i s i r r e g u l a r , with numerous small depressions and r i s e s (see Figure 3), and d i f f e r s from most other fjords i n i t s sedimenta 7 cover, which i s predominantly sand. A rocky s i l l of about 6 fathoms ( l l m) depth occurs at the mouth of the i n l e t , but some rocks here protrude r i g h t up to above the surface, rendering the entrance narrow and treacherous for any larger ships. The Central Section has the deepest point of Useless Inlet (34 fathoms = 62 m). Unlike t y p i c a l f j o r d s , t h i s part i s very wide r e l a -t i v e to i t s length, with a strongly indented shoreline along i t s northern side. The bottom topography, however, i s smooth, with sediment, dominantly mud, blanketing any i r r e g u l a r i t i e s that may have existed, whereas only one small, permanent creek flows into the Outer Section, several r e l a t i v e l y large creeks enter the Central Section and have brought abundant sediment to t h i s part of the i n l e t , which has resulted i n an extensive development of deltas. The Inner Section, with a bedrock s i l l at i t s entrance, i s but a narrow branch-off from the Central Section; the actual head of Useless Inlet i s formed by Mud Bay within the Central Section. The Inner Section may be envisaged as a passage between Fatty Basin and Useless I n l e t , not being an i n t e g r a l part of e i t h e r , but for the purpose of t h i s paper i t i s regarded as a section of Useless I n l e t . I t i s characterized by a very i r r e g u l a r bottom topography, with numerous rocky r i s e s separating small basins, and by shallow depth with a maximum of 8 fathoms (15 m). Rainy Bay i s a wide bay open to the more exposed waters of Junction Passage. Several rocky islands form part of a bedrock s i l l across i t s mouth, but near the SE-shore t h i s s i l l i s poorly developed. Some large bedrock exposures r i s e to within 8 fathoms (15 m) of the Location of BOTTOM PROFILES _0.5 miles y Basin The map i n d i c a t e s l o c a t i o n s o f t h e b o t t o m p r o f i l e s p r e s e n t e d on t h e f o l l o w i n g p a ge s . V e r t i c a l e x a g g e r a t i o n on a l l p r o f i l e s i s a p p r o x i m a t e l y 1 : 1 3 Depth s a r e g i v e n i n f a t h o m s ( 1 fm = 6 f t ) F igure 2 OYSTER BAY MUD BAY FATTY BAS IN FATTY BASIN 0.2 0.4 0,6 0.8 1.0 mi les Figure A 8 surface, but most of the bottom of Rainy Bay i s blanketed with the common olive-green mud, giving the bay a smooth bottom topography. 2. Pre-Pleistocene Geology Rock exposures i n t h i s region are mostly confined to shorelines and f a u l t c l i f f s , because the slopes are generally covered with heavy overburden, t h i c k underbrush, and for e s t . Examination of the rocks , therefore, had to be l i m i t e d to the shorelines i n most places. The i n t r i c a t e system of i n l e t s and bays, however, offered an excellent picture of the geology of the area. Furthermore, most of the many f a u l t s are very evident both i n nature and on a e r i a l photographs. Following are generalized descriptions of the major rock units exposed i n the Fatty Basin - Useless Inlet area (Figure 5) . The s t r a t i g r a -phic nomenclature i s that of Muller and Carson (1969). ( i ) Volcanic rocks of the Bonanza Subgroup (Upper T r i a s s i c to Lower Jurassic) dominate the area of in t e r e s t . They are characterized by andesites, dacites, and t u f f s , with andesites the by far most abundant. Occurring as d i s t i n c t flows of various thicknesses, the andesites are mostly greenish-grey to reddish-brown, but great v a r i a t i o n may be found; the i n d i v i d u a l flows usually are sharply defined by an abrupt change i n colour. The mineralogy consists dominantly of phenocrysts and microl i t e s of intermediate plagioclase, associated with small amounts of (clino-) 9 pyroxene and very l i t t l e hornblende; secondary minerals l i k e c h l o r i t e , c a l c i t e , and epidote are commonly present. C h l o r i t e a l t e r a t i o n i s wide-spread and probably responsible f o r most of the greenish colour t i n t s . Small amounts of c a l c i t e and epidote are almost ubiquitous throughout the andesite flows, and secondary quartz commonly occurs as f i l l i n g s of fractures and vugs. Dacites and ryhodacites are r e l a t i v e l y rare and have been observed mostly along the northern shore of Fatty Basin. L i t h i c t u f f s , graded by g r a v i t y s o r t i n g , occur s p o r a d i c a l l y and are best exposed at a few l o c a l i t i e s i n the Basin. ( i i ) The Quatsino Formation (Upper T r i a s s i c ) i s exposed mostly as massive, l i g h t to dark grey limestone, with extensive outcrops along southern Seddall Island and the TTE-Shore of Uchucklesit I n l e t . Predomi-nantly f i n e - g r a i n e d , the limestone i s i n many places c r y s t a l l i z e d to a fine-sugary or c o a r s e l y - c r y s t a l l i n e texture near contacts with v o l c a n i c rocks. These contacts commonly appear i n i n t r i c a t e shapes, with veins or minute v e i n l e t s of andesite extending f a r i n t o the limestone. Frequently, andesite fragments are scattered throughout the contact zone of a carbonate rock, and i n at l e a s t one case (Uchucklesit I n l e t ) , a b r e c c i a of large v o l c a n i c fragments wi t h i n a l i g h t - g r e y , fine-grained matrix was observed over a zone about 30 feet wide. Features l i k e these are po s s i b l y the r e s u l t s of l a v a flows being extruded over poorly consolidated lime muds of the present Quatsino Formation. On the SE-shore of Mud Bay i n Useless I n l e t , a small exposure of limestone b r e c c i a was observed. Angular limestone blocks of various sizes 10 here are densely scattered throughout a fine-grained, l i g h t grey limestone matrix, and i n these blocks the only f o s s i l s within the area of interest were found. They were recognized as c r i n o i d stems, but poor preservation prevented further i d e n t i f i c a t i o n . ( i i i ) D i o r i t e s occur i n two small exposures i n Fatty Basin and near the mouth of Uchucklesit I n l e t , respectively. The l a t t e r i s a s l i g h t l y altered hornblende d i o r i t e , with some of the hornblende replaced by c h l o r i t e and epidote. The rock i n the Fatty Basin outcrop, however, has undergone excessive a l t e r a t i o n , and most of i t s hornblende has been replaced by c h l o r i t e and epidote. Remnant grains of clinopyroxene are surrounded by a dense mass of f i n e l y - f i b r o u s t r e m o l i t e - a c t i n o l i t e , c h l o r i t e , and epidote, and the effects of the Quatsino limestone, which probably was penetrated by t h i s small d i o r i t e stock, are apparent i n the form of abundant c a l c i t e throughout the rock, an otherwise rather uncommon feature within d i o r i t e s . These intrusives are most l i k e l y part of the West Coast D i o r i t e , which i n turn may be part of the West Coast C r y s t a l l i n e Complex (Muller and Carson, 1969). They are e x c e l l e n t l y exposed on Tzartus Island across Junction Passage, and appear as f i n e to medium grained hornblende d i o r i t e s . The unaltered rock consists mainly of plagioclase (andesine) and hornblende, associated with only minor quartz and potash feldspar; accessory minerals are epidote, magnetite, b i o t i t e , and sphene. (iv ) About ^000 feet west of the Useless Inlet entrance, the contact between Bonanza volcanics and granodiorites of the Island Instrusions (Middle to Late Jurassic) i s exposed on the shore. This i n t r u s i v e i s part 11 of the Kennedy Lake Batholith and consists mainly of plagioclase (oligoclase) , with minor quartz, hornblende, potash feldspar, b i o t i t e and c h l o r i t e , and accessory magnetite, apatite, and sphene. (v) The Karmutsen Formation (Lowerto Upper T r i a s s i c ) , which i s characterized by extensive green, massive bas a l t s , i s exposed along Henderson Lake (north of Uchucklesit I n l e t ) and Alberni Channel. I t does not appear i n the immediate v i c i n i t y of Fatty Basin and i s not shown on Figure 5, but i t constitutes an important source for the sediments of the area. The basalts consist mainly of plagioclase (andesine to l a b r a d o r i t e ) , associated with minor hornblende, clinopyroxene (augite), and magnetite. The matrix i s very r i c h i n c h l o r i t e , and numerous veins are f i l l e d with c h l o r i t e , epidote, or feldspar. ( v i ) Mafic dykes, 5 to 15 feet wide, have been observed i n a few outcrops i n both Fatty Basin and Useless I n l e t . They tend to follow the d i r e c t i o n a l trends of major f a u l t s and fracture zones. The mineralogy of the dykes i s dominated by feldspar (andesine to labradorite) and clinopyroxene (augite). Epidote i s very abundant, and minor replacement by c h l o r i t e and t r e m o l i t e - a c t i n o l i t e was observed. 3. Origin of the Inlets Numerous f a u l t s and fracture zones criss-cross the Fatty Basin Useless I n l e t area and are s t r i k i n g l y apparent on a e r i a l photographs. Their d i s t r i b u t i o n i s presented i n Figure 6, and t h e i r d i r e c t i o n a l trends are summarized i n the frequency rose of Figure 7 (a). From the l a t t e r , two dominant s t r i k e directions for the f a u l t s and fracture zones can be recognized, one of them trending S 60° W - N 60° E, the other N 6o° W -S 60° E. In t e r e s t i n g l y , these directions appear to coincide with the general trends of i n l e t s and bays. On Figure 7 (b), such d i r e c t i o n a l trends have been superposed upon the frequency rose as determined from the surface fractures alone. The obvious coincidence i n preferred directions suggests a major influence of the f a u l t s and fracture zones upon the o r i g i n of the bays and i n l e t s . The re l a t i o n s h i p between f a u l t structures and coastal depres-sions becomes very apparent when both are actually observed i n the f i e l d . Faults and wide shear zones commonly p a r a l l e l the shoreline, and often the steep to v e r t i c a l bedrock slopes along the i n l e t perimeters are actual f a u l t faces. In other cases, f a u l t s s t r i k e at some angle to the coas t l i n e , causing offsets of the l a t t e r by as much as 30 feet and forming v e r t i c a l to overhanging c l i f f s . Both the Big Gut and Small Gut are surface expressions of wide shear zones, which, due to the soft nature of the strongly sheared rocks, have been p r e f e r e n t i a l l y eroded by ice and water. 13 The shear-zones l i k e l y originated before completion of the extrusion of the Bonanza volcanics. Narrow dykes of strongly fractured andesite and andesite-breccia i n the immediate v i c i n i t y of and p a r a l l e l to some of the wide shear-zones (most notably the Big Gut) , have been intruded into these zones of weakness, located probably at the contacts between previously extruded lava flows. The rocks forming the dykes are andesites s i m i l a r to most of the surrounding bedrock, which suggests that they are probably also part of the Bonanza volcanics. The shear-zones may therefore have originated towards the end of the extrusion of the Bonanza subgroup i n early Jurassic time. Thus, since they follow the dominant directions discussed above, the l a t t e r also seem to have o r i g i -nated i n the Early Jurassic. A major episode of block f a u l t i n g occurred along the west coast of the present Vancouver Island during Early Tertiary (Muller, 1969). We assume the f a u l t s of the Fatty Basin area to have formed during that time, following the pre-existing d i r e c t i o n a l trends of the many shear-zones . Most of the f a u l t s dip 70° - 90°, but good evidence for the d i r e c t i o n of movement i s scarce. Only i n the small canyon above Oyster Beach were structures resembling slickensides observed, which here p i t c h about 80° on a steeply dipping f a u l t c l i f f . Numerous minor f a u l t s , however, show v e r t i c a l displacements of up to several feet, and both the s i m i l a r i t y between these and the large f a u l t s as w e l l as the c r i s s - c r o s s i n g network of steep f a u l t scarps suggest that the major f a u l t structures had the same sense of motion. Most of the f a u l t movement probably was of the I l l d i p - s l i p type, with only minor l a t e r a l displacements. A few low-angle f a u l t s occur i n the area, but these are un-related to the main f a u l t system. They cut older fractures with l i t t l e displacement, they do not seem to be associated with any shear zones, and t h e i r s t r i k e directions seem to be at random r e l a t i v e to the d i r e c t i o n -a l trends followed by other f a u l t s . In conclusion, i t i s suggested that the i n l e t s of the Fatty Basin - Useless Inlet area originated p r i m a r i l y from large-scale block f a u l t i n g during the early Tertiary. Depressions formed at that time were subjected to subsequent erosion and possibly renewed minor f a u l t i n g . The f i n a l shape of the i n l e t s was attained during the l a s t g l a c i a l period, when ice flows concentrated i n and accentuated the depressions. N60°E FREQUENCY ROSE Strike Directions of Faults and Fracture Zones S60°E C i r c l e Diameter = 50 of Joint Directions ^'R.B.-eastern shore ----Sunshine Bay U.l.- outer section + Oyster Bay Small Gut Mud Bay U. I.-south shore of central section U.l.-inner section + Big Gut Junction Passage KB.-south shore UchucklesitTnlet U. I - inner section to Mud Bay R.B.= Rainy Bay U.l. = Useless Inlet FB.= Fatty Basin 15 k. G l a c i a l History The region was l a s t covered with ice during the Late Wisconsin G l a c i a t i o n , which l o c a l l y corresponds to the Vashon Stade of the Fraser Gla c i a t i o n . Starting at about 25,000 years B.P. , the ice advanced and reached a maximum approximately 15,000 to 17,000 years ago, when i t extended to the continental break about Uo miles west of Barkely Sound (Carter, 1970). The ice then receded r a p i d l y , and with diminishing t h i c k -ness, i t formed v a l l e y glaciers on the present west coast of Vancouver Island. Such glaciers l a s t covered the Fatty Basin area between 11,000 and 12,000 years ago, at that time retre a t i n g towards the north-northwest (Henderson Lake). Most of the g l a c i a l d r i f t , mainly cobble- and pebble-sands, probably originated from these retre a t i n g v a l l e y g l a c i e r s , whereas clayey s i l t s were deposited e a r l i e r under the more extensive i c e cover. Evidence for the g l a c i a l past i s abundant throughout the area of i n t e r e s t , i n the form of U-shaped valleys and, on bedrock exposures, numerous deep grooves, s t r i a t i o n s , i r r e g u l a r furrows, and generally smooth, rounded surfaces. The ice flow directions were strongly influenced by the topography, since g l a c i a l s t r i a t i o n s p a r a l l e l the shorelines of the i n l e t s i n most cases. Even shallow and narrow depressions l i k e the Big Gut, which trends i n a direc t i o n almost at a ri g h t angle to the o v e r - a l l ice movement here, deflected the flow of the i c e . As discussed i n a previous chapter, the depressions are fault-derived and have existed already p r i o r to the g l a c i a l advance. G l a c i a l sediments, as b r i e f l y mentioned above, are yellowish-brown t i l l s and medium to l i g h t grey clayey s i l t s . Most of the sands, s i l t s , and clays i n Fatty Basin and Useless Inlet are derived from these g l a c i a l deposits. Since the probable directions of former i c e movements are known, the source areas for an appreciable percentage of the t e r r e s -t r i a l sediments i n t h i s area can be roughly outlined. They are mostly within the Henderson Lake region, underlain predominantly by Karmutsen and Bonanza rocks; Photograph h gives a good o v e r - a l l picture of the entire g l a c i a l passage from Henderson Lake to Fatty Basin. 17 5. Physical Oceanography Herlinveaux (1966) published an account of the physical oceanography of Fatty Basin and Useless Inlet i n volume No. 228 of the Manuscript Report Series of the Fisheries Research Board, and most of the information presented i n t h i s chapter i s taken from that paper. The data are based on observations during a one-year period from I96U to 1965. The factor most responsible for the oceanographic c h a r a c t e r i s t i c s of Fatty Basin i s the constricted nature of the entrance passages, the two guts, which commonly causes a head difference between the sea l e v e l s i n the Basin, Rainy Bay, and Useless I n l e t . This head difference may reach maxima up to 1 foot during spring tides of large t i d a l ranges, with the sea l e v e l outside being higher during the flood and lower during ebb t i d e s . The head difference r e s u l t s i n a very rapid and turbulent water flow through the two guts, the so-called " j e t s " , which cause extensive mixing of the transported waters. Fatty Basin receives l i t t l e runoff, and consequently the incoming and outgoing t i d a l volumes are nearly equal, but may change s i g n i f i c a n t l y i n magnitude. During large spring t i d e s , the volume transported can be as high as 8.5 x 10 f t or 26.6% of the Basin f, 3 volume, whereas on neap t i d e s , the volume may be as l i t t l e as 1.3 x 10° f t or only h.1% of the Basin volume. Since creeks contribute only r e l a t i v e l y small amounts of fresh water to Fatty Basin, most of the l o w - s a l i n i t y water appears to come i n from Alberni Inlet through Rainy Bay and the Small Gut. S a l i n i t i e s i n Rainy Bay are usually lower than those i n Useless I n l e t , and consequently the waters entering Fatty Basin through the Small Gut tend to override the water from Useless I n l e t . This phenomenon can be commonly observed during upcoming t i d e s . The temperature i n Fatty Basin i s marked by an annual cycle, with a maximum of 19 -8° C i n summer and a minimum of 5-9° C i n winter. The cycles at a l l depths usually appear to be i n phase; only during a short period i n May, 19&5, did the temperature at 2k m stop r i s i n g p a r a l l e l to the temperatures at shallower depths. Both the p o s i t i v e gradients i n winter (surface waters colder than deep waters) and the negative gradients i n summer (surface waters warmer than deep waters) were i n t e n s i f i e d during neap tides and weakened during spring t i d e s . This t i d a l effect i s l i k e l y due to the increase or decrease of the "jet action" and i t s mixing effects i n the Basin with spring or neap t i d e s , respectively. In January, the v e r t i c a l p o s i t i v e gradient reaches i t s greates development, and i t i s generally more s i g n i f i c a n t i n Useless Inlet and Rainy Bay than i n Fatty Basin. S i m i l a r l y , the negative gradient during summer also seems to be less pronounced i n Fatty Basin, where the temper atures at depth are higher than i n the surrounding i n l e t s . The isotherms, which reach from Junction Passage into Useless Inlet without di s r u p t i o n , are broken at both the Small and the Big Gut, where water s t r a t i f i c a t i o n s are destroyed i n vigorous mixing processes. Furthermore, the two guts are shallow to the extent that normally only surface waters can enter the Basin at a l l times. 19 In early June, 1965, a marked thermocline was noted i n Fatty Basin between 20 and 2k meters depth, i n d i c a t i n g a lack of exchange down to the bottom waters. A p o s i t i v e s a l i n i t y gradient exists i n the area throughout the year and at a l l depths, but i t seems to be best developed near the surface i n winter and spring due to winter p r e c i p i t a t i o n and the resultant i n -crease i n runoff. Like the temperature gradient, the v e r t i c a l s a l i n i t y gradient i s always less i n Fatty Basin than i n Useless I n l e t , since s a l i n i t y i s strongly affected by the j e t - a c t i o n as w e l l . P e r i o d i c a l l y , the water column i n Fatty Basin i s agitated from the surface to the bottom. Coinciding with the sharp thermocline, a marked halocline was noted between 20 and 2k meters i n Fatty Basin during early June, 1965. The dissolved oxygen concentration seems to move through a seasonal c y c l e , with a maximum i n January and a minimum during November i n the whole water column. In early June, 1965, however, when a lack of exchange near the bottom i n Fatty Basin was indicated by marked haloclines and thermoclines, the concentration of dissolved oxygen dropped to zero at 2k meters. High concentrations occur during September and are probably the r e s u l t s of an autumnal phytoplankton bloom and good water exchange at a l l depths. Throughout most of the year, the dissolved oxygen concen-t r a t i o n s are higher at corresponding depths i n Fatty Basin than i n Useless Inlet or Rainy Bay. 20 In conclusion, the oceanographic c h a r a c t e r i s t i c s of Fatty Basin are strongly influenced by the shallow entrance passages, the two guts. Water exchange i s e n t i r e l y dependent upon t i d a l flushing through these narrow channels, which causes two j e t s of water that tend to keep the whole Basin mixed to homogeneity, especially during spring t i d e s . Further-more, only surface waters can enter the Basin over the shallow s i l l s . During l a t e May and early June, just after the "spring "bloom" of phytoplankton with i t s associated oxygen maximum, when the surface s a l i n i t i e s are low, stagnant bottom waters occur i n the deep "holes" of Fatty Basin. As soon as the surface s a l i n i t i e s increase, however, the usual good exchange of the bottom waters takes place again, and an oxygen-ated regime resumes. I V i e w o f t he B i g Gut f r o m t h e I n n e r b e c t i o n o f U s e l e s s I n l e t , w i t h F a t t y Baa In i n the b a c k g r o u n d . The e n t r a n c e t o t h e g u t h e r e i s a l s o i t s n a r r o w e s t s e c t i o n * a t t h i s p o i n t , a head d i f f e r e n c e be tween the w a t e r s on e i t h e r s i d e up to 1 f o o t may d e v e l o p d u r i n g maximum t i d a l exchange , c a u s i n g t he " j e t - a c t i o n " as d i s c u s s e d i n t h e t e x t . V i ew o f t he S m a l l Gut f r o m t h e P a t t y B a s i n s i d e d u r i n g a v e r y l ow t i d e . B e d r o c k e x p o s u r e s b l o c k t he e n t r a n c e xo t he gu t i n the f o r e g r o u n d , and most of t he w a t e r f l o w c o n c e n t r a t e s i n a n a r r o w c h a n n e l of abou t 8 to 10 f e e t w i d t h to t he r i g h t . B o t h g u t s r e p r e s e n t s u r f a c e e x p r e s s i o n s o f f a u l t s and s h e a r zones ) i n d i c a t i n g the major i n f l u e n c e of t h e s e s t r u c t u r a l f e a t u r e s upon t h e s h a p i n g o f the i n l e t s . Barkley Useless Sound I n l e t .Fatty Basin Useless I n l e t Patty Rainy Basin Bay Temperature (°C) Salinity ( % 0 ) Q. OJ Q Figure 8 Longitudinal sections of temperature and s a l i n i t y d i s t r i b u t i o n s from Junction p through Useless I n l e t , Patty Basin, ana Rainy Bay. (from Herlinveaux, 1 9 6 6 ) Barkley Sound Useless I n l e t Fattv Rainy Basin Bay NOV. 18 1964' A Jan. 27 1965 £ 0 * — 20-sz *-> 30-Q OJ 40 Q Apr .12 1965;^  " \1/ 20 30 40 t no /£*•'• :^S. data -/if /•* * .Y7.0—p: <V6?f-• 9 C-4.5-Jane 3 1965%^'' J u l y 15 1965': Dissolved Oxygen (ml/ l ) Figure 9 (from Herlinveaux, 1966 ) Longitudinal sections of dissolved oxygen d i s t r i b u t i o n s from Junction Passage through Useless I n l e t , Fatty Basin, and Rainy Bay THE SEDIMENTS 1. Rate of Sedimentation Due to contamination or actual loss of several samples during r e t r i e v a l of the sampling howls, the data for monthly sedimentation rates at the four stations i n Fatty Basin are incomplete. The exchange of howls, furthermore, could not be maintained at exactly one^nonth i n t e r v a l s , and was e n t i r e l y omitted during December, 1969. Consequently, extrapolation of data was necessary i n some cases, and the sedimentation rate referred to i n Figure 10 i s the average d a i l y rate of sedimentation, as determined from the weight of each sample, divided by the number of days since c o l -l e c t i o n of the previous sample. The t o t a l amount of sediment deposited from suspension during a one-year period averages about 900 grams per square meter i n Fatty Basin, and the v a r i a t i o n i n sedimentation rate throughout the year i s shown i n Figure 10 •• A maximum rate of sedimentation occurs during the period July to September, immediately preceded by a minimum i n May and June. A r e l a -t i v e l y minor increase i n the sedimentation rate can also be observed i n February and March, probably r e f l e c t i n g the increased p r e c i p i t a t i o n and resultant runoff at that time of the year. The summer maximum may be caused l a r g e l y by phytodetritus derived from the euphotic zones. During J u l y , the s t r a t i f i c a t i o n of the water column i s w e l l developed outside Fatty Basin (Figure 8 ) and may resu l t i n p a r t i c u l a r l y s i g n i f i c a n t concentrations of phytoplankton near the surface. Consequently, since only surface waters enter Fatty Basin from Rainy Bay and Useless I n l e t , the amount of debris carried into the Basin 21 22 during each upcoming tide appears to he considerable. This i n f l u x has been v i s u a l l y confirmed many times by skin diving i n the strong-current zones o f f the two guts, when during a flood t i d e the v i s i b i l i t y under water drops to very few f e e t , due to the great amounts of organic detritus suspended i n the inflowing waters. The considerable mixing of incoming waters with the entire water column of Fatty Basin re s u l t s i n less organic suspended material being swept out again during the ebb t i d e . The Basin, therefore, seems to act as a large natural trap for phytoplanktonic debris. The influence of phytoplankton upon sedimentation rates i n a shallow coastal environment was studied by Stephens, Sheldon, and Parsons (1967) during investigations i n Departure Bay on the east coast of Van-couver Island near Nanaimo. They noted an increase i n the size of sus-pended p a r t i c l e s from January through June, caused either by aggregation of d e t r i t a l p a r t i c l e s or by larger phytoplankton species. This increase could cause a higher sedimentation rate during summer, since, i f one assumes constant density and general morphology of the plankton, a doubl-ing i n p a r t i c l e size w i l l r e s u l t i n a fourfold increase i n s e t t l i n g velo-c i t y . In addition, these workers also suggested a decreased buoyancy during senescence of several species of diatoms, which then, too, would increase the sedimentation rate i n summer. Figure 10 Rates of Sedimentation in FATTY BASIN 23 2. Clay Mineralogy The clay mineralogy was determined with X-ray d i f f r a c t i o n methods, outlined i n the appendix. Representative mud samples from Rainy Bay, Useless I n l e t , and Fatty Basin were analysed and compared to g l a c i a l clayey s i l t s and the clay fractions of g l a c i a l d r i f t . Only clay mineral groups as outlined i n Grim (1968) were i d e n t i f i e d ; further d i s -t i n c t i o n of i n d i v i d u a l mineral species was not attempted. Chl o r i t e group minerals were i d e n t i f i e d "by t h e i r basal r e f l e c -tions at 1^.1 - 1*;.5, 7 -1, ^ . 7 , and 3.55 A° . Most of these peaks were d i s t i n c t i n a l l samples analysed, regardless of the sample loca t i o n and whether they were from muddy sediments, s i l t y c l a y s , or g l a c i a l d r i f t . The peaks were unaffected by IC1- - saturation, but heating to 5^0° C resulted i n an increased 1^ A° peak, a decreased 7.1 A° r e f l e c t i o n , and a disappearance of the lower-order peaks. K a o l i n i t e minerals usually break down upon heating to above 500° C. However, since the main peaks of k a o l i n i t e coincide with second and lower order c h l o r i t e peaks, and since poorly c r y s t a l l i z e d c h l o r i t e s are s i m i l a r l y unstable above 500° C, c r i t e r i a other than heating to high temperatures had to be used to i d e n t i f y k a o l i n i t e s . Several samples were treated with warm hydrochloric a c i d , which tends to dissolve c h l o r i t e s , but normally does not affect k a o l i n i t e . Subsequently, most of the c h l o r i t e peaks had disappeared; very small remnants of both the 1^ A 0 and 7-1 A° peaks remained, however, probably 2k i n d i c a t i n g an incomplete decomposition of the better c r y s t a l l i z e d c h l o r i t e s . I f k a o l i n i t e was present i n any of the analysed samples, then only i n exceed-ingly small amounts. Furthermore, an otherwise common k a o l i n i t e peak at 2.38 A° was never observed here, which also suggests the absence of k a o l i n i t e i n these samples. I l l i t e was recognized i n a l l analysed samples by the 10.1 A 0 and r a r e l y by the lower-order k.98 - 5.00 and 3.3k A° peaks. Glycolation of the samples had no effect on these peaks. Smectite minerals, which c h a r a c t e r i s t i c a l l y expand t h e i r basal f i r s t - o r d e r r e f l e c t i o n s from ik A° to 17 A° upon treatment with ethylene g l y c o l , were not detected i n any of the samples. I f present at a l l , the smectite group minerals occur only i n minor traces. Since no change of the peaks was observed after g l y c o l a t i o n , i t i s assumed that no vermiculite was present, which also expands i t s ik A° basal r e f l e c t i o n , although less so than the smectite minerals. No attempts were made to determine r e l a t i v e abundances of the clay mineral groups present, although several methods e x i s t . As Pierce and Siegel (1969) point out, these methods are exceedingly u n r e l i a b l e . Further-more, the clay mineral assemblage i n the area of interest i s monotonous and hardly warrants a quantitative evaluation. The assemblage i s dominated by c h l o r i t e minerals and minor i l l i t e . Other clay minerals, l i k e k a o l i n i t e , smectite, and verm i c u l i t e , are either absent or present only i n traces. L i t t l e doubt as to the o r i g i n 25 of these clays remains, since g l a c i a l clayey s i l t s and ov e r l y i n g g l a c i a l d r i f t , both very common i n the area, have a cla y mineral assemblage i d e n t i c a l to that of the muddy sediments throughout the area. Although present weather-ing of the Bonanza v o l c a n i c s , which contain abundant c h l o r i t e as an a l t e r a t i o n product, w i l l add to the c h l o r i t e content of the sediments, t h i s mechanism i s of minor importance as compared to erosion of the vast amounts of g l a c i a l d r i f t and clayey s i l t s , a l l w e l l exposed along much of the shoreline and i n most creek beds. I t should be noted, however, that most of the g l a c i a l deposits have o r i g i n a t e d from Bonanza and Karmutsen v o l c a n i c s , and these two rock formations probably c o n s t i t u t e the ultimate source f o r most clay minerals found i n Fa t t y Basin, Useless I n l e t , and Rainy Bay. Other l o c a l i z e d sections of Barkely Sound are dominated by c l a y groups l i k e smectite and i l l i t e (Carter, 1 9 7 0 ) , f u r t h e r i n d i c a t i n g the clay mineralogy of l o c a l areas on the west coast to be p r i m a r i l y dependent upon the a v a i l a b l e sources, which u s u a l l y are g l a c i a l deposits derived from the major rock u n i t s nearby. A d d i t i o n a l f a c t o r s , l i k e currents and d i f f e r e n t s e t t l i n g v e l o c i t i e s of the clay minerals, seem to be of minor importance i n t h i s region. 26 3. Heavy Minerals Heavy minerals were separated from 30 samples, using only the size fractions between 2.5 and k p h i , which correspond to the very f i n e sands. These fractions are used for heavy mineral analysis by most workers because ( i ) the content of heavy mineral grains i s usually greatest i n the fine sand f r a c t i o n s ; ( i i ) the fractions f i n e r than about h phi are generally too small to accurately i d e n t i f y i n d i v i d u a l mineral grains through common o p t i c a l methods ; ( i i i ) the coarser fractions contain too many rock fragments, some of which may have a s p e c i f i c gravity s i m i l a r to or s l i g h t l y greater than that of bromoform; (iv) consistent use of these fractions i s he l p f u l when comparing the heavy mineral content of di f f e r e n t samples, which i n most cases do not have the same size d i s t r i b u t i o n or content of t e r r e s t r i a l grains versus s h e l l fragments. No d i s t i n c t i o n was made between magnetic and non-magnetic opaque minerals, since finely-granular opaque material, presumably magnetite, was frequently found scattered through non-opaque grains. Because these grains usually did not react to a magnet, any percentage figures for magnetic and non-magnetic opaque minerals are inherently erroneous, i f the data are based upon separation with a simple hand magnet. The mineralogy of the opaque minerals was determined through the use of r e f l e c t e d l i g h t on t h i n sections. Magnetite appears to be the pre-27 dominant mineral, ilmenite was suspected i n a few cases. Limonite was ra r e l y observed, mostly i n g l a c i a l d r i f t samples subjected to subaerial exposure. No pyr i t e was found, despite the r e l a t i v e abundance of py r i t e i n the rocks along the i n l e t perimeters. The content of heavy minerals i n the analysed sand fractions was e n t i r e l y dependent upon the nature of the sediment. Heavy minerals were most abundant i n t e r r e s t r i a l sands and least common i n g l a c i a l clayey s i l t s and espec i a l l y i n carbonate sands, where s h e l l fragments dominate the l i g h t mineral f r a c t i o n (see Figure l l ) . Clinopyroxenes (augite) and epidote are predominant and average 32 and 3k percent of the heavy mineral s u i t e , respectively. Orthopyroxenes were found only i n very small amounts i n a few samples. Hornblende, with some exceptions, occurs i n much lower percentages, averaging only 13 percent, but no d i s t r i b u t i o n a l pattern i s apparent. Opaque minerals average 19 per-cent, with highs of 30 and lows of 5 percent. Chlorite i s very common and was observed i n most of the samples, but never i n s i g n i f i c a n t quantities. I t i s probably more abundant i n the f i n e r size fractions ( c l a y s ) . Sphenes i n small, i r r e g u l a r grains commonly occur as accessories, but other minerals such as garnet, s p i n e l , z i r c o n , and topaz are very rare. This assemblage dominates the heavy mineral fractions i n the Fatty Basin area. In other parts of Barkley Sound, amphiboles (hornblende) are the dominant heavy minerals, followed by epidote and, occasionally, c h l o r i t e (Carter, 1970). Pyroxene percentages are very low, but accessories l i k e garnets are r e l a t i v e l y abundant i n that region. The c h a r a c t e r i s t i c a l l y high pyroxene and low amphibole contents of the heavy mineral suites i n the 28 Fatty Basin area, t h e r e f o r e , appear to be a l o c a l i z e d feature. The Bonanza v o l c a n i c s and e s p e c i a l l y the mafic dykes commonly contain pyroxene (augite) phenocrysts. These weather out e a s i l y when exposed, le a v i n g behind a d i s t i n c t l y p i t t e d rock surface. Much of the hornblende seems to have been a l t e r e d to c h l o r i t e , epidote, or magnetite, a l l exceedingly abundant i n the andesites. The small d i o r i t e i n t r u s i o n s , o r i g i n a l l y hornblende d i o r i t e s (Westcoast D i o r i t e ) , a l l have undergone extensive a l t e r a t i o n s , and the hornblende often i s e n t i r e l y destroyed. Most of the heavy minerals i n the sediments are probably derived from g l a c i a l d r i f t deposits. Since the general d i r e c t i o n of i c e flows here has been towards the south-west, the o r i g i n of the d r i f t i s to the north and north-east of the area of i n t e r e s t . Extensive exposures of Bonanza v o l c a n i c s and Karmutsen b a s a l t i c lavas occur i n that region, both probably containing more pyroxenes than amphiboles among t h e i r mafic constituents. Hornblende-rich i n t r u s i v e s are r a r e i n that part of Vancouver Island. On the other hand, most remaining sections of Barkley Sound are bordered by i n t r u s i v e rocks, a l l of which have hornblende as main mafic mineral. These rock exposures are h i g h l y i r r e g u l a r and appear i n numerous islands throughout the Sound region. Present-day mass-wasting and erosion i s considerable, as i n d i c a t e d by abundant accumulations of f r e s h , angular d i o r i t e and granodiorite fragments below steep bedrock slopes (Carter, 1 9 7 0 ) . During g l a c i a t i o n , when i c e acted as an abrasive t o o l ( g l a c i a l grooves and s t r i a t i o n s ) , erosion must have been very strong. Consequently, most of the g l a c i a l gravel and the majority of l i t h i c fragments of the sands are derived 29 from the i n t r u s i v e rocks of the region (Carter), whereas i n Fatty Basin and Useless Inlet equivalent sediments contain mainly andesites and basalts. I t may be concluded, therefore, that the difference between heavy mineral suites from the l o c a l i z e d Fatty Basin area and the remaining Barkley Sound region i s l a r g e l y due to di f f e r e n t source rocks. Furthermore, sediment mixing caused by bottom and longshore currents i s considerable i n Barkley Sound, exposed to the influence of the open ocean, whereas i n Fatty Basin, Useless I n l e t , and Rainy Bay such mixing i s prohibited by shallow entrance s i l l s . FATTY BASIN USELESS INLET RAINY BAY OTHERS HEAVY MINERALS ] Accessories and Unknowns Opaques Amphibole (Hble) s ^ l Pyroxene (Aug.) Epidote QUARTZ vs. ROCK FRAGMENTS (relative percentages in light fraction ) Quartz Rock fragments ufrAi/iFc fabundance in J ncMvica fine sand fract ions j Light minerals Heavy minerals — o ^ PO rf to co r» to o to o> «-iO ~^ CM ^  ^  Sample Numbers Figure 11 30 Table 1 : Weight percentages of t o t a l heavy minerals i n f i n e sand f r a c t i o n s , and percentages from grain-count analysis of the dominant minerals within the heavy f r a c t i o n s . imple fo. T o t a l heavi es Epidote Pyroxene (Aug.) Hornblende Opaques Othe 1 .6 H5 21* 11 12 8 16 2l*.0 32 1*2 I* 20 2 21 21.2 1*1 25 9 21 1* 29 9-0 31* 26 6 28 6 38 1.6 28 39 5 23 5 1*2 2.6 38 26 11 23 2 1*8 1.8 16 32 29 21 2 60 12.8 20 25 35 20 t r 69 9-0 30 1*0 10 15 5 73 .1* 28 1*0 12 20 t r 81 20.6 22 1*1* 13 13 8 81* 12.1* 65 20 10 1* 1 85 21.0 20 25 15 30 10 87 17-8 23 31* 15 21* 1* 91 15.2 25 1*0 13 20 2 96 18.0 35 1*8 10 6 1 99 1*.8 25 1*8 10 15 2 103 17-1 1*1 32 1 25 1 109 29-6 20 25 15 30 10 111 21*. 0 37 27 3 30 3 121 13.1* 31* 37 1U 15 t r 122 .1 30 1*0 15 15 t r 123 9.2 5^ 25 10 15 5 12l* .1 1*0 30 15 15 t r Note: "Others" u s u a l l y include c h l o r i t e , sphene, and unkowns. S p i n e l , garnet, z i r c o n , topaz, and t r e m . - a c t i n o l i t e are very r a r e . Table 2 : Percentages of dominant minerals i n l i g h t f r a c t i o n s of f i n e sands. lple No. Quartz Fspar Chert Rock Frags. S h e l l Frags. Mica Unknc 1 80 10 t r 8 t r t r 16 1*0 1* 5 1*0 1* t r 21 20 5 TO 5 29 10 t r 60 30 32 30 60 5 t r t r 38 35 1*0 25 1+2 10 t r 10 65 15 1*8 10 t r 5 15 70 t r 60 35 5 5 35 15 5 69 15 6 5 70 t r 3 t r 73 15 10 70 3 81 1*0 10 10 1*0 t r 81* 60 10 30 85 50 15 25 5 5 87 1*0 5 25 30 91 75 5 10 15 t r 96 60 5 30 5 98 Uo 10 50 t r 99 1*0 5 50 5 t r 103 10 5 5 70 10 109 50 5 1*0 5 110 30 15 10 1+5 i l l 20 5 65 10 116 1*0 8 50 2 121 25 t r 65 10 122 5 15 80 123 25 • 10 20 30 t r t r 12U 5 60 35 Note: " t r " = trace (less than 1%) 32 h. Delta Developments Most of the t e r r e s t r i a l sediments of Fatty Basin and Useless Inlet are transported by streams, which are short due to a r e l a t i v e l y low t e r r a i n and the dissection of the country by i n l e t s and bays. Numerous small, seasonal creeks and t r i c k l e s occur and are responsible for a s i g -n i f i c a n t sediment transport, but only the l a r g e , permanent creeks b u i l d deltas of various sizes at t h e i r mouths, depending upon the a v a i l a b i l i t y of unconsolidated g l a c i a l material. These deltas perform a s i g n i f i c a n t r o l e i n the sedimentation processes of the area, because much of the t e r r e s t r i a l debris i n the i n l e t s i s derived from here. Study of the d e l t a i c sediments, therefore, provides a conclusive picture of the t e r r e s t r i a l material encountered elsewhere i n the i n l e t s . In Fatty Basin, the two most s i g n i f i c a n t d e l t a developments occur at the northern and southern ends, respectively. They d i f f e r d i s -t i n c t l y i n shape and sediments and represent two types of d e l t a s , repeated throughout t h i s region. Type A i s exemplified by the north d e l t a , b u i l t by a r e l a t i v e l y sluggish creek and sloping gently and uniformly towards the Basin. No clear d i s t i n c t i o n between top- and foreset-beds can be made here. Although the delta i s completely submerged at high t i d e s , i t i s exposed for about 100 feet during low t i d e s . Boulders are abundant i n the upper part, but the lower section above low-tide l e v e l i s covered largely with grey mud, intermixed with coarse pebbles and she l l s and p a r t l y over-grown with eel-grass. The grey 33 mud extends for about 250 to 300 feet into the Basin, where i t dips under-neath the ubiquitous olive-green mud. A rough s t r a t i f i c a t i o n of the grey mud was observed, and at two feet depth, a fi v e - i n c h layer of very tough, li g h t - g r e y , massive g l a c i a l clayey s i l t was encountered. This s i l t has es s e n t i a l l y the same composition as other g l a c i a l clayey s i l t deposits along the shore, constituting the dominant source for the grey muds. The creek above the delta appears graded and very mature i n most parts. I t s downdrop i s mainly i n the l a s t 100 feet of i t s course, otherwise i t sluggishly meanders through a r e l a t i v e l y wide, swampy, heavily forested v a l l e y . I t appears u n l i k e l y that the water discharge increases s i g n i f i c a n t l y even during the spring runoff. Consequently, deposition on the d e l t a i s slow and characterized by s i l t s and clays with low contents of organic matter Delta type B i s represented by the south-delta of Fatty Basin, b u i l t by a highly immature creek with rapid water flow and many small f a l l s along i t s course. About 600 feet from the Basin, three d i f f e r e n t flows combine to form the main creek of 3 to 5 feet width and 1/2 foot average depth. Erosion i s very active i n the drainage and has caused steep banks of s o f t , unconsolidated t i l l and s o i l . The delta here i s rapidly advancing, with d i s t i n c t top and foreset slopes that seem to override the green mud. Deposition i s con-centrated on the steep foreset-slope and the outer sections of the topset-slopes , where sediments are characterized by dark-brown mud and an abundance of small twigs and other coarse organic debris. Near low-tide l e v e l , a dark layer composed almost e n t i r e l y of woodchips was encountered View of the ridge south and south-east of Fatty Basin, showing logged area i n the watershed of the creek above the soutn-delta. The creek and the "notch." i n the ridge mark the p o s i t i o n of one of the large f a u l t * . 10 I View of the south-delta i n Fatty Basin. The d e l t a i s of type B, as defined i n the text, shows d i s t i n c t top- and foreset beds, and i s r a p i d l y advancing. Towards the r i g h t , a steep bouider slope can be seen, a feature common along the i n l e t perimeters. I The north-delta of Patty Basin, a good example of delta type A. Some angular boulders appear i n the foreground, derived from steep-sided bedrock ex-po sores to the l e f t of the picture. Outcrop of organic material on the upper section of Oyster Beach, consisting mainly of wood-fragments, twigs, roots, and similar debris, which was dated at almost 7000 years B.P. I t i s considered to be part of a former delta, since i t parallels deltaic s t r a t a b e l o w a n d a b o v e . at 2 feet depth. These chips originated about a dozen years ago as the waste product of a logging operation i n the drainage above the delt a (see Photograph 9 ) , and are s t i l l abundant i n t h i c k layers along several sections of the creek. Hence almost two feet of sediments have been added to the outer parts of the topset-slope i n only a dozen years, indeed a rapid rate of deposition. Most of the i n t e r t i d a l delta top i s covered by very coarse debris, with a gradation outward from the head of the delta from boulders to cobbles, pebbles, and coarse gravel. L i t t l e deposition takes place here at present, and the f i n e r debris has been winnowed out by wave- and current-action or has s e t t l e d below the cobble and pebble layer. In t h i s section of the d e l t a , the creek has cut a d i s t i n c t channel through the coarse surface sediments. At the head of the d e l t a , older d e l t a i c deposits are exposed on the banks of the creek. They consist of well-rounded boulders, pebbles, and sands i n s t r a t a l a i d down at a steeper angle than the modern topset-beds. The erosive and depositional capacities of the creek, therefore, have changed since the older delt a was f i r s t b u i l t . The change may be due i n part to the increased runoff after the logging of the watershed, but i t may also indicate re-juvenation of the creek due to u p l i f t of the land. Evidence for u p l i f t i s apparent at the so-called Oyster Beach i n Useless I n l e t , a delt a s i m i l a r to the south delta of Fatty Basin (delta type B). Here, the creek runs along a course of very steep gradient and i s choked with huge, angular boulders. Near the head of the d e l t a , 35 the creek has cut down several feet into earlier-deposited d e l t a i c s edi-ments , which slope at a s l i g h t l y greater angle than the present topset beds and form an a c t i v e l y eroding, small c l i f f above the modern de l t a . These older s t r a t a contribute abundant coarse debris to the sediments, and cobbles and pebbles accumulate as steeply sloping deposits below the unconsolidated c l i f f . Here, an exposure of a 3 - to 5-inch layer of dark brown to black organic material appears, consisting of p a r t l y decomposed wood-fragments, twigs, and pieces of tree-bark (Photograph 12). A carbon-lU age of 6820 +_ 320 years was determined for t h i s m a t e r i a l , which i n compo-s i t i o n seems to be si m i l a r to the layer of wood fragments found below the surface of the south-delta i n Fatty Basin. That layer originated from waste debris of a logging operation, was transported by the strongly increased creek flow and subsequently deposited near the low-tide l e v e l on the surface of a rapi d l y advancing delta. I f a s i m i l a r o r i g i n i s postulated for the dark organic layer at Oyster Beach, where an event l i k e a forest f i r e i n the watershed of the creek could have provided the wood debris, t h i s material now indicates an u p l i f t of at least 8 - 1 0 feet r e l a t i v e to the present l e v e l of the sea. At about 7000 years B.P. , the p o s t - g l a c i a l sea l e v e l r i s e was l a r g e l y completed to within about 10 feet of the present l e v e l , and consequently the t o t a l u p l i f t of the land here during the l a s t 7000 years may have been i n the order of 20 feet. The dark organic layer i s part of the former d e l t a , since i t p a r a l l e l s the d e l t a i c beds below and above. The l a t t e r , which o v e r l i e the peat bed to a thickness of several f e e t , are l i k e l y to have formed during the l a s t stages of sea l e v e l r i s e towards the present l e v e l . 36 U p l i f t of the land took place subsequent to the r i s e of sea level,which resulted i n the downcutting of the creek into e a r l i e r deposited d e l t a i c beds and the formation of a new d e l t a , the present Oyster Beach. The two di f f e r e n t delta-types common to t h i s region are i l l u s t r a t e d on the accompanying diagram (Figure 12). Type A occurs at the north end of Fatty Basin, at the head of Useless Inlet (Mud Bay), i n several of the many small bays along the northern perimeter of Useless I n l e t , and at the head of Oyster Bay. These deltas a l l have i n common - a sluggishly flowing creek as build i n g agent; - deposits of g l a c i a l clayey s i l t along the creek banks and adjacent shores; - grey clayey s i l t derived from these g l a c i a l s i l t deposits as the main sediment; - a very gentle gradient towards the i n l e t and a lack of d i s t i n c t foreset slopes. Type B can be observed at the south end of Fatty Basin, on the NW-shore of the Central Section of Useless Inlet (Oyster Beach), and on the NW-side of the Outer Section. A l l these deltas have i n common - a rapi d l y flowing, turbulent creek as building agent; - deposits of coarse g l a c i a l d r i f t along the creek beds and adjacent shores; - coarse debris l i k e sand, gravel, cobbles and pebbles, or wood-fragments and twigs as dominant sediment; - d i s t i n c t topset- and foreset-slopes. Green i.iud Grey Hud = dominant-| sediment Seizor as s Boulders Pebbles Gravel V 4. + * Deposits of G l a c i a l S i l t y Cla Bedrock Figure 12 A Diagrammatic cross-section of d e l t a -Type A (e.g. North-delta i n Fatty Basin) Figure 12 B Diagrammatic cross-section o f d e l t a Type B (e.g. Oyster-Beach i n Useless I n l e t ) 37 5. Sediments i n Fatty Basin, Useless Inlet,'and Rainy Bay Cumulative curves for samples analysed i n d e t a i l were plotted by computer and assembled on a single diagram. Several clusters or groups of curves were noted (Figure 13) and subsequently used f o r the d e f i n i t i o n of various sediment types. This procedure was adopted, since cumulative curves give a good graphic representation of the main s t a t i s t i c a l para-meters l i k e mean s i z e , deviation, skewness, and k u r t o s i s , a l l of which strongly influence the positions or shapes of the curves. Cumulative curves of samples with s i m i l a r parameters appear i n groups as presented i n Figure 13, which therefore provide an excellent basis for the d e f i n i -t i o n of d i f f e r e n t types of sediments. The hydraulic behaviour, a factor strongly influencing the s t a t i s t i c a l parameters of a sediment, may be s i m i l a r for shell-fragments and t e r r e s t r i a l grains, especially i n the fine size fractions (Koldijk, 1968). Consequently, the basic sediment typesas defined by the groups of cumulative curves alone had to be further subdivided according to the abundance of t e r r e s t r i a l material versus carbonate fragments. Another subdivision was necessary within the t e r r e s t r i a l pebble and gravel groups, i n order to distinguish between rounded material of g l a c i a l o r i g i n and angular fragments derived from l o c a l sources. Altogether, thi r t e e n sediment types have been defined t h i s way (see Figure ik ), and a l l the samples not analysed i n d e t a i l (see Map No. 1 for sample l o c a l i t i e s ) were then c a r e f u l l y compared with Groups of Cumulative Curves Defining Sediment Ty_pes 3 -2 -1 0 1 2 3 4 5 6 7 8 9 (phi) 3 -2 -1 0 1 2 3 4 5 6 7 8 9 (phi) 100 - 3 -2 -1 0 1 2 3 4 5 6 7 8 9 GRAIN S IZE (phi) Figure 13 Sediment groups as defined from c umul a t . c urv e s Numbers and colour representations of sediment types as shown on sediment d i s t r i b u t i o n maps Nature of sediment types © ^ 3 Angular, coarse gravel © 1 5 Coarse sand, few pebbles 6 Coarse sand, abundant pebbles 8 \ band - s h e l l mixture, coarse, muddy 12 S h e l l - d e b r i s , coarse to very coarse 4 band, medium to f i n e , l i t t l e gravel © 13 s «« « < Grey mud 15 Olive-green mud r i c h i n organic materials © — 7 Gravel and pebbles, rounded with very abundant s h e l l s © ^ 11 S h e l l debris, f i n e to very f i n e , muddy © ^ 10 S h e l l debris, medium, muddy with abundant gravel © — » 9 Angular gravel - s h e l l mixture, very coarse,muddy 14 Ym Green mud with abundant small s h e l l fragments F igure 14 13 as sediment groups that of cumulative curves, with and colour representations on the sediment d i s t r i o u x i o n sediment types, defined subdivisions of the eight re based on groups the numoers as they appear maps . 38 representative samples of each of the thi r t e e n sediment types and c l a s -s i f i e d accordingly. Sediment d i s t r i b u t i o n maps could then be prepared with considerable accuracy for Fatty Basin, less for Useless I n l e t , and least for parts of Rainy Bay, with the accuracy r a t i n g dependent upon sample spacings i n each of these areas. In r e l a t i v e l y shallow Fatty Basin, furthermore, personal observation of the sediments 'in s i t u ' was possible through extensive skin-diving and occasional Scuba-diving. The main s t a t i s t i c a l parameters are plotted i n Figures 17 and 18, i n order to v i s u a l i z e c h a r a c t e r i s t i c s and relationships that may not be r e a d i l y apparent from cumulative curves alone. Parameters used here are those defined by Folk (1965), and include the Graphic Mean, Inclusive Graphic Standard Deviation, Inclusive Graphic Skewness, and Graphic Kurtosis (Table 13 )• An attempt was also made to f i n d an areal d i s t r i b u t i o n pattern of the s t a t i s t i c a l parameters by p l o t t i n g t h e i r values at respective sample positions on a map. No d i s t i n c t i v e pattemwas apparent, however, lar g e l y because i n d i v i d u a l sediment types commonly occur i n t i n y , i s o l a t e d patches or are intermixed to various degrees. S t a t i s t i c a l parameter values are e n t i r e l y dependent upon bottom topography, water currents, and supply of sedimentary material, factors a l l exceedingly variable over short distances i n the r e s t r i c t e d environment of these i n l e t s . Only very close sample spacings over the entire area, followed by accurate analyses of a l l samples taken, could possibly produce a d i s t r i b u t i o n a l pattern as sought. Such e f f o r t s are, however, far too time-consuming to be considered here. 39 On the other hand, the plots of Figures IT and 18 permit some inferences and conclusions regarding the sediments and t h e i r depositional environments, r e f e r r i n g here only to the eight basic sediment groups as defined on Figure 13. These groups are also plotted on Figure l 6, which presents a nomenclature according to r e l a t i v e percentages of gravel, sand, and mud, but which disregards the contents of t e r r e s t r i a l versus carbonate material. The diagram, s l i g h t l y modified, was taken from Folk (1965) and provides the following c l a s s i f i c a t i o n of the eight basic sediment groups: Group 1 = Gravel to s l i g h t l y sandy gravel; Group 2 = Predominantly sandy gravel; Group 3 = Sand; Group k = Mud and sandy mud; Group 5 = Mostly sandy gravel, some gravelly sand; Group 6 = Gravelly sand, muddy sand, gravelly-muddy sand; Group T = Sandy to gravelly mud; Group 8 = Variations from muddy-sandy and muddy gravel to gravelly mud and gravelly-muddy sand. From Figure IT (A), i t i s apparent that the least sorted sedi-ment groups are those with large ranges i n mean size (notably Group 8 ) , but that the actual value of mean sizes has no influence upon the degree of sorting. The poorly sorted sediments are mixtures of coarse s h e l l s , gravel, sand, and mud, where a s l i g h t change i n abundance of any of these materials may cause d i s t i n c t s h i f t s of the mean s i z e , which then results i n a large range of mean sizes for the sediment group as a whole. 1+0 T e r r e s t r i a l sands of Group 3 and some gravels of Group 1 constitute the best sorted sediments. Mixing i s of minor importance, and both groups are f a i r l y homogeneous with only small ranges i n mean siz e . The sands are r e s t r i c t e d to the zone of r e l a t i v e l y strong currents i n the Outer Section of Useless I n l e t , and to the lower reaches of numerous small bays, where i t i s concentrated through winnowing of the near-shore gravel. These well-washed gravels are common as a t h i n sedimentary blanket on near-shore sections of small bays as we l l as on many delta tops (delta type B), but at a depth of about 2 inches below the surface, the gravel inv a r i a b l y becomes very poorly sorted due to concentrations of fine-grained material. Muds of Group k have a r e l a t i v e l y great range i n deviation, caused by the common presence of some large s h e l l fragments and by v a r i a -tions i n clay content. Figures 17 (B and C) represent only Groups 1 to It, because plots of the remaining groups, a l l predominantly mixtures of gravel, sand, and mud, have more random d i s t r i b u t i o n and tend to obscure the c l a r i t y of the diagram. I t i s apparent that most sediments- are f i n e - to strongly f i n e -skewed, whereas only t e r r e s t r i a l sands of Group 3 are symmetrical or coarse-to strongly coarse-skewed. These sands constitute a well-washed, s l i g h t l y gravelly sediment with very l i t t l e mud, whereas most of the other groups contain enough mud to cause a p o s i t i v e skewness. Even the gravels of Group 1, which are often moderately sorted, appear as a strongly f i n e -skewed sediment. Hence, even small amounts of mud seem to have a consider-able influence upon the skewness of a coarse sediment. 1+1 The s i l t y muds of Group 1+ are also strongly fine-skewed, since they contain abundant fine clay material i n the size range of less than .002 millimeter. Sediments with mean sizes intermediate between coarse gravel and fine s i l t tend to be less fine-skewed, since the grain-sizes commonly are gradational from coarse to f i n e , which subdues the effects of the c l a y - f r a c t i o n upon the skewness of a sample. Figures 18 (A, B, C) represent plots of skewness versus kurtosis. In (A) , about hal f the analysed samples are shown to be mesokurtic, 3*+ per-cent to be l e p t o k u r t i c , and 16 percent p l a t y k u r t i c . A very rough trend seems to l i n k p l a t y k u r t i c and mesokurtic samples to negative and symmetri-cal skewness, and leptokurtic to very-leptokurtic samples to pos i t i v e and strongly-positive skewness. Pl a t y k u r t i c samples, which have a better sorting i n the t a i l s than i n the central portions of t h e i r respective cumulative curves, are mostly sediment mixtures with an appreciable content of s h e l l debris. The carbonate fragments introduce a very poor sorting into a l l but the very fine size fractions of a sample, since i n the s i l t range few carbonate fragments p e r s i s t . In the cumulative curve of such a sample, therefore, the t a i l representing the s i l t and clay fractions i s better sorted than the central portion. Leptokurtic samples are d i f f i c u l t to relate to any p a r t i c u l a r pattern, but both carbonate and t e r r e s t r i a l sands with a considerable mud fr a c t i o n appear to be dominantly of leptokurtic nature. The s i l t s and clays i n these sediments are probably less sorted than the r e l a t i v e l y homogeneous coarser f r a c t i o n s . Groups o f C u m u l a t i v e Cu r ve s S e d i m e n t No. 0 Symbol s u s e d f o r S e d i m e n t Types :' 133 0° ° Sed iment No. - • • • S e d i m e n t No. S e d i m e n t No. @ ' 1 A. Sed iment No. V x- x * X; S e d i m e n t No. S e d i m e n t No. Q) ///'''' ///////. V / / ' ' // /, Sed imen t No. Figure 15 G = S = M = g = s = m = Gravel (>2mm) Sand ( .0625 to 2mm) Mud « . 06 2 5mm) gravelly sandy muddy (Modified from Polk, 1965) GRAIN SIZE NOMENCLATURE POR THE 8 SEDIMENT TYPES DEPINED PROM GROUPS OP CUMULATIVE CURVES. Figure 16 -3 -2 -1 0 1 2 3 4 5 6 Graphic Mean (phi-units) .8 .7 .6 .5 .4 i n 3 CO C D E 1 T j S 0 - E G O - 1 -.2 -.3 O "liS.2 Figure 17 & i -A • * * *, •3 -2 -1 Graphic Mean (phi-units) -.3 -.2 -.1 0 .1 .2 -3 .4 .5 Incl. Graph. Skewness 3.0 A " 2.0 1.5 1.0 0.5 ~ i — r • • • -.2 r i i r i f i .8 A l l Samples 3.0 2.5 CO 2-0 (O o tr 1-5 si i.o C L CD °-5 « * . ' o r . - - - . » f I 1 I I I 1 I I I B Groups 1 to 4 -.2 .0 .2 .4 .6 .8 3.0 2.5 2.0 1.5 1.0 0.5 ^•^'"'^•••••^•"xj I 1 I I I r I I 1 1 I Groups 5 to 8 -.4 -.2 .0 .2 .4 .6 .8 Ind. Graph. Skewness Figure 18 k2 Table 3 Limits of Some of the Main S t a t i s t i c a l Parameters (from Folk, 19&5) 1. Inclusive Graphic Standard Deviation ( i n phi-values) Less than .35 •-= very w e l l sorted .35 - • 50 = = w e l l sorted .50 - .71 -= moderately w e l l sorted • 71 - 1.00 = moderately sorted 1.00 2.00 = poorly sorted 2.00 U.00 = very poorly sorted Over h.00 = extremely poorly sorted 2. Inclusive Graphic Skewness + 1.00 to + .30 = strongly fine skewed + .30 to + .10 = fi n e skewed + .10 to - .10 = near symmetrical .10 to - .30 = coarse skewed .30 to - 1.00 = strongly coarse skewed 3. Graphic Kurtosis Less than .67 = = very p l a t y k u r t i c .67 - .90 = = p l a t y k u r t i c .90 - 1 .11 = mesokurtic 1.11 1 • 50 = = leptokurtic 1.50 3 .00 = very leptokurtic Over 3 .00 = extremely l e p t o k u r t i c Table h : Ranges and average values of s t a t i s t i c a l parameters within each of the eight groups of cumulative curves, as shown i n Figure 13. Group 1 Mean In.Gr.St. Inc. Gr. Graphic (phi) Dev.(phi) Skewness Kurtosis low - 3.19 • 71 + .130 .871 high - 2.21 2.16 + • 770 1.501+ avge - 2.77 1.32 + .415 l.Ol+l Group 2 low - 1.81 1.2"+ + .026 .710 high + .1+7 2.02 + .387 1.755 avge - .67 1.6"+ + .228 1.161+ Group 3 Group 1+ Group 5 low + 1.27 .59 - .1+09 .81+9 high + 2.67 1.53 + .198 1.81+1+ avge + 1.89 1.10 .136 1.029 low + 1+.81 1.21+ + .103 .708 high + 6.95 3.1+2 + .759 2.139 avge + 5.88 2.53 + .1+10 1.313 low 1.99 1.63 .338 .633 high + .21 2.66 + .1+97 1.023 avge - • 91 2.13 + .153 .836 Group 6 low + .22 1.1+3 - .211+ .721 high + 2.68 2.88 + .625 2.155 avge + 1.58 1.91 + .132 1.311+ Group 7 low + 3.94 2.62 + .291 .90"+ high + 5-05 I+.56 + .1+69 1.197 avge + 1+.1+8 3.65 + .1+09 1.068 Group 8 low - .85 3.06 + .107 .699 high + I+.71 5.27 + .622 1.359 avge + 1.79 1+.1+9 + .324 .974 True surface area(in m^) -Sediment Type USELESS INLET Percent of t o t a l true surface area - USELESS INLET True surface area ( i n m^) -FATTY BASIN Percent of t o t a l true surface area FATTY BASIN Bedrock Boulders 210,000 8.0 38,000 6.8 . 35,000 "1.3 19,000 3.1* 3 115,000 h.3 3,200 .6 1* 31*0,000 12.9 9,800 1.7 5 30,000 1.1 2,600 .5 6 1*5,000 1.7 15,700 2.8 7 85,000 3.2 6,800 1.2 8 - - 3,800 .7 9 30,000 • 1.1 1,100 .2 10 100,000 3.8 25,000 l*.l* 11 - - 800 .1 12 95,000 3.6 15,600 2.8 13 200,000 7.6 11,600 2.0 lk 50,000 1.9 12,1*00 2.2 15 1,280,000 1+9.5 396,600 70.6 Table 5 : True surface areas of bedrock exposures and sediments i n Useless I n l e t and Fa t t y Basin. The f i g u r e s r e f e r to areas below Low-Tide Level only. They were c a l c u l a t e d u t i l i z i n g data on width and length of exposures as w e l l as angles of slopes. 6. Sediment D i s t r i b u t i o n Thirteen sediment types have been defined f o r the Fatty Basin Useless Inlet - Rainy Bay area and are shown on two accompanying maps , where they are represented by colour symbols and numbers from 3 to 15. Their r e l a t i o n s h i p to the eight basic sediment groups defined from s t a -t i s t i c a l parameters i s presented i n Figure Ik. Accumulations of la r g e , angular boulders are regarded as an additional type of sediment and are l i s t e d as No. 2 on the d i s t r i b u t i o n maps; they are represented by a dark grey colour. Extensive exposures of bedrock occur i n the i n l e t s and appear as l i g h t pink areas on the d i s t r i -bution maps; the bedrock i s l i s t e d as No. 1 i n the legend. Sediment dispersal i s mainly effected by currents. Waves are s i g n i f i c a n t only along some gravel beaches facing an open stretch of wate espec i a l l y i f a good supply of t e r r e s t r i a l debris from g l a c i a l deposits i available. Oyster Beach i n the Central Section of Useless Inlet offers the best example of t h i s type. The sediments, as discussed i n d e t a i l below, may be roughly grouped as follows: (A) Boulders; (B) Pebbles and gravels; (C) T e r r e s t r i a l sands; (D) Shell debris; (E) Muds; (F) Coarse shell-gravel mixtures. 1+6 (A) Boulders: (Sediment No. 2): Large, angular boulders are common along the i n l e t perimeters, where they usually form steep slopes. The vast majority i s derived as primary products of mass wasting along steep sections of strongly f r a c -tured bedrock slopes. The petrology, consequently, i s always that of near-by bedrock exposures, mainly andesites of the Bonanza subgroup. Shell debris, notably barnacle p l a t e s , as w e l l as muds are commonly trapped i n protected areas between the boulders and may form considerable accumu-l a t i o n s . The t o t a l extent of these angular boulders amounts to about 3.k% and 1.3% of the t o t a l bottom surface i n Fatty Basin and Useless I n l e t , respectively. (B) Pebbles and gravels ( i ) Mostly angular, coarse gravel with few s h e l l fragments (Sediment No. 3): These gravels cover extensive areas i n Useless I n l e t , but are not very common i n Fatty Basin. Like the large boulders, they are the result of mass wasting of strongly fractured bedrock and consist predomi-nantly of Bonanza andesites. Occasionally, other gravels, derived from g l a c i a l deposits and characterized by w e l l - to subrounded shapes and variable petrology, are intermixed with the angular material. The sediment occurs most extensively on deltas of the type B, and also along the base of steep, strongly fractured bedrock faces or boulder slopes. Invariably, the well-washed gravel extends to only about 2 to 3 inches depth, where i t becomes strongly intermixed with f i n e r -grained material. The area covered by the gravels amounts to only 0.6% of the t o t a l bottom surface i n Fatty Basin, but 4.3 % i n Useless I n l e t . ( i i ) Rounded pebbles and gravel (Sediment No. 7) : This coarse material i s e s s e n t i a l l y confined to areas influenced by strong currents, notably the two guts, the mouth of Useless I n l e t , and some creek beds near the heads of deltas (Photograph 13 ). Although abrasion of angular, l o c a l l y derived fragments may be a factor here, most of the pebbles probably originated from g l a c i a l d r i f t . The petrology i s variable and ranges from granodiorites and monzonites to basalts (see rock units discussed i n chapter "Geology"), although intermediate volcanics of the Bonanza subgroup are most abundant. The assemblage i s e s s e n t i a l l y that of the coarse fractions of g l a c i a l d r i f t deposits common throughout the region. The currents generated by the t i d e as w e l l as by the head difference i n sea l e v e l (see chapter "Physical Oceanography") i n the two guts reach a speed of at least 5 to 10 knots , a figure based upon own estimations along the narrowest sections of these passages. Fine-grained material i s e a s i l y transported by these strong currents, and only the pebble and gravel fractions of the o r i g i n a l g l a c i a l d r i f t deposits remain, cons t i t u t i n g the predominant surface sediment. Accumulations of angular fragments occur only below some steep bedrock faces, where other s e d i -ments are i n short supply, and none of these pebbles showed any loss of angularity due to currents or abrasion by other sediments. Patches of medium to coarse s h e l l fragments are common between the rounded pebbles, wherever the current strength i s less severe than 48 i n the narrowest sections of the entrance passages. Due to t h e i r p l a t y shape, larger s h e l l s are not e a s i l y moved by a current, especially when the convex sides are up. Sediment No. 7 accounts for only about 1.2% of the t o t a l bottom surface area i n Fatty Basin, but 3.2% i n Useless I n l e t . (C) T e r r e s t r i a l sands: ( i ) Medium to fine sand (Sediment No. h): This sand contains very l i t t l e gravel or mud and few s h e l l f r a g -ments, and i t constitutes the best sorted sediments i n the area under con-sideration here, apart from some of the gravels of sediment No. 3. Dark grey to greenish grey i n colour, t h i s uniform sand consists mostly of andesitic rock fragments, with the Bonanza volcanics the l i k e l y source. Its greatest extent i s i n the Outer Section of Useless I n l e t , where i t forms the predominant sediment. Tidal currents here reach flow-speed maxima of over 4 knots (Herlinveaux, 1966) and keep the sediments r e l a t i v e l y free of fine-grained material, causing the better sorting as compared to most other sediments i n the area. The second common occurrence of these medium to fi n e sands i s i n the lower reaches of some bays, where they are concentrated by winnowing of the near-shore t e r r e s t r i a l sediments through surface currents and wave action. Towards depth, the sands gradually become muddier and eventually dip beneath the ubiquitous olive-green mud. Due to i t s extensive occurence i n the Outer Section, t h i s sand covers about 12.9% of the bottom surface area i n Useless I n l e t , but only l.h% i n Fatty Basin. ( i i ) Coarse sand with abundant gravel and pebbles (Sediment No. 6): This sediment i s confined usually to the near-shore zone of bays with abundant supply of t e r r e s t r i a l debris. I t appears to be the product 1*9 of winnowing action by surface currents and waves, which remove much of the medium to fine-grained sand (sediment No. h), as discussed i n the pre-vious paragraph. Considerable amounts of gravel and pebbles are always present, and a gradation between the coarser and f i n e r fractions i s common. The mud content i s usually n e g l i g i b l e , but s h e l l fragments may be abundant. The l a t t e r originate 'in s i t u ' from bivalves l i k e L i t t l e Neck Clams, Cockles, and Butter Clams, which accounts for the many unbroken s h e l l s . In petrology s i m i l a r to the f i n e r sands, t h i s sediment consists almost exclusively of andesitic rock fragments derived from Bonanza volcanics. I t covers about 2.8% of the bottom surface area i n Fatty Basin, and 1.1%> i n Useless I n l e t . ( i i i ) Coarse sand with some gravel, pebbles, and sh e l l s (Sediment No. 5): This coarse sand occurs only i n r e l a t i v e l y few l o c a l i z e d patches, usually near deposits of sediment No. 6 or of gravels of sediment No. 3. Gravel and pebbles are not abundant, and no gradations between them and sand-sized grains are apparent. The sediment represents only a l o c a l i z e d , inhomogeneous mixture between sands and gravels. S h e l l fragments here, as i n sediment No. 6, originate mostly 'in s i t u ' from sand-burrowing bivalves. This sand covers only 0.5% of the bottom surface area i n Fatty Basin, and 1.1% i n Useless I n l e t . (D) S h e l l debris: ( i ) Coarse s h e l l debris with few t e r r e s t r i a l fragments (Sediment No. 12): This coarse s h e l l debris i s common throughout the area of 50 i n t e r e s t , occurring mostly along a narrow zone at the base of steep bed-rock and boulder slopes. I t also accumulates i n numerous small patches between large boulders and i n hollows on bedrock exposures. Barnacle plates form the most common single constituent, but calcareous worm tubes are also very abundant along many sections of the i n l e t perimeters. To-gether, the s h e l l remains of these two organisms may account for more than 90 percent of the calcareous f r a c t i o n i n samples dominated by s h e l l debris. Towards depth, the coarse s h e l l material grades into medium-sized, muddy debris or green muds r i c h i n s h e l l fragments. The sediment covers about 2.8% of the bottom surface area i n Fatty Basin, and 3.6% i n Useless I n l e t . ( i i ) Medium-sized s h e l l debris, very muddy arid with abundant  t e r r e s t r i a l gravel (Sediment No. 10): This sediment commonly occurs below accumulations of coarse s h e l l debris of sediment No. 12. The l a t t e r often forms wedge-shaped deposits with r e l a t i v e l y steep surfaces along the base of bedrock and boulder slopes, and f i n e r s h e l l material probably i s removed by bottom currents and deposited at a lower l e v e l . Here, muds become abundant, and the mud content of sediment No. 10 i s always very high. T e r r e s t r i a l gravel also concentrates i n t h i s zone, since the rock fragments tend to s l i d e o f f the i n c l i n e d surface of No. 12 - deposits. Sediment No. 10 dips beneath the olive-green muds at a very low angle, and i t usually can be encountered just below the mud for a distance of several feet from the actual surface contact between the two sediment types. 51 Whenever steep bedrock and boulder slopes reach r i g h t down to the mud zone (around i s l a n d s , for example), no accumulations of coarse, we l l washed sh e l l s occur. Here, the muddy and gravelly s h e l l debris fringes the slopes d i r e c t l y , e s p e c i a l l y i f the supply of carbonate material i s l i m i t e d . Sediment No. 10 covers about k.k% of the bottom surface i n Fatty Basin, and 3.8% i n Useless I n l e t . ( i i i ) Fine to very f i n e s h e l l hash (Sediment No. l l ) : This sediment i s uncommon and was found only i n a few small patches i n Fatty Basin and Rainy Bay. The fine-grained s h e l l fragments probably were winnowed out of other carbonate deposits accumulated i n a few favorable locations near the mud zone. Consequently, the sediment always has a high mud content and grades into the muds of Sediment No. 14. The extent of the fine-grained s h e l l hash i s approximately 0.1% of the bottom surface i n Fatty Basin, and i s n e g l i g i b l e i n Useless I n l e t . (E) Muds: ( i ) Olive-green mud r i c h i n organic matter (Sediment No. 15): This mud i s the most common sediment throughout the i n l e t s under consideration here. I t consists mainly of s i l t - s i z e d p a r t i c l e s , but clay ( p a r t i c l e size below 2 microns) i s usually very abundant. Hydrogen Sulphide (H^ S ) , detected by i t s strong odour, seems to be always present, but mud dwellers l i k e B r i t t l e Stars and Mud Clams occur and may even be abundant i n places. The olive-green colour i s due mainly to the high content i n 52 organic matter. Treatment with hydrogen peroxide (H"2 0 ) , which destroys the organic carbon, caused a pronounced colour change towards a medium grey, whereas hydrochloric acid and Na-dithionite (removing the carbonate and iron) had l i t t l e or no effect on the colour. The i n f l u x and deposition of organic material i n Fatty Basin and Useless I n l e t i s considerable (see chapter "Rate of Sedimentation"). Narrow and shallow entrances cause the i n l e t s to act as large traps for p a r t i c u l a t e organic matter, which i s suspended i n the surface waters that enter during each upcoming t i d e . Furthermore, Seki (1968) showed that i n a shallow coastal area t o t a l production of organic matter i n the water column exceeds i t s destruction by bacteria during most times of the year. In the case of Fatty Basin and Useless I n l e t , l i t t l e of t h i s excess organic matter i s l i k e l y to be flushed out during an ebb-tide, and consequently most of i t s e t t l e s on the mud. Within the mud, anaerobic bacteria produce a reducing environ-ment with abundant H^S, regardless of depth and despite the fact that dissolved oxygen i s present i n the entire water column throughout most of the year (see Figure 9 ). Related l i t e r a t u r e commonly, and perhaps i n -d i s c r i m i n a t e l y , associates H^S-rich mud with stagnant, de-oxigenated bottom waters, whereas t h i s i n fact may not be true at a l l i n some of the cases. Contribution of material to the mud i s considerable and varies s l i g h t l y through the seasons (see chapter "Sedimentation Rate"), but no s t r a t i f i c a t i o n was noted i n any of the cores. This lack i s att r i b u t e d to the presence of various bottom dwellers l i k e B r i t t l e Stars and Polychaete Worms, as w e l l as to b a c t e r i a l a c t i v i t y destroying the pa r t i c u l a t e organic matter that s e t t l e s on the mud surface. Upon d i v i n g , f l u f f y layers of 53 f e a t h e r - l i k e organic debris were observed on the mud, e a s i l y s t i r r e d up by the s l i g h t e s t water movement. Below the surface, however, the mud i s of monotonous homogeneity, with no large debris other than occasional shell-fragments or twigs and leaves. The upper s i x inches are usually uncompacted and of low density, and the mud here has coagulated into t i n y (0.1 - 0.5 millimeter) b a l l s . Below t h i s surface zone, the mud i s much more viscous and sharply increases i n density with depth. In some l o c a l i t i e s (e.g. the "holes"), concentrations of f i n e -grained shell-debris may occur near the surface, but none were found below the upper few inches. The strongly reducing conditions within the mud, esp e c i a l l y i n the deepersections of the i n l e t s , probably have a di s s o l v i n g effect upon carbonate p a r t i c l e s , thus eliminating small s h e l l debris i n time. Only a few larger s h e l l fragments were found at some depth below the surface, and these always appeared soft and f r a g i l e , due to t h e i r p a r t i a l d i s i n t e g r a t i o n . T e r r e s t r i a l s i l t s and clays are brought into the i n l e t s mainly through creeks and t r i c k l e s , and they originate most l i k e l y from g l a c i a l d r i f t and clayey s i l t s , both common i n extensive deposits throughout the area. The olive-green muds are ubiquitous throughout the i n l e t s and also i n the more open Barkley Sound (Carter, 1970); they are deposited wherever bottom currents are weak to non-existent, and they usually cover e x i s t i n g i r r e g u l a r i t i e s to give the smooth, rounded bottom topography common i n fjords and i n l e t s . Along the perimeters, the mud overlaps upon other sediment (sands, s h e l l d e b r i s ) , except for the fronts of some 54 r a p i d l y advancing deltas (type B), which i n turn tend to override the mud with t h e i r foreset beds. In Fatty Basin, the mud covers an overwhelming 70.6% of the t o t a l bottom surface; i n Useless I n l e t , where the Outer Section i s domi-nated by sandy sediments, i t s extent s t i l l amounts to a large "+9.5% of the bottom surface. ( i i ) Olive-green mud with abundant small s h e l l fragments (Sediment Wo. lh): This sediment may be regarded as part of sediment No. 15, and occurs i n narrow zones below s h e l l deposits at the base of bedrock and boulder slopes along the i n l e t perimeters. I t i s simply a mixture of the olive-green mud with numerous small s h e l l fragments winnowed out of the coarse s h e l l debris. The sediment covers 2.2% of the bottom surface i n Fatty Basin, 1.9% i n Useless I n l e t . ( i i i ) Grey Mud (Sediment No. 13) : Deposits of grey mud are usually r e s t r i c t e d to bays, where g l a c i a l clayey s i l t s are exposed along the shore or on the banks of an inflowing creek (See also chapter "Delta-Developments"). The grey mud has s i m i l a r s t a t i s t i c a l parameters and the same mineralogy as the g l a c i a l clayey s i l t , from which i t i s l i k e l y derived. The action of anaerobic bacteria i s less here than i n the olive-green muds, although small amounts of I^S are commonly present. The content i n organic carbon i s characteris-t i c a l l y low i n these grey muds, and a f a i n t s t r a t i f i c a t i o n may commonly 55 be observed i n cores. This sediment covers only 2 . 0 % of the bottom surface i n Fatty Basin, but 7.6% i n Useless I n l e t , where i t occurs extensively i n Mud Bay. (F) Coarse shell-gravel mixtures: ( i ) Coarse, muddy mixture of shell s with gravel and sand (Sediment No. 8 ) : This sediment occurs i n a few is o l a t e d patches, usually near the deposits of gravelly sand. The many unbroken s h e l l s are derived from organisms inhabiting the sandy sediments, l i k e Cockles, Little-Neck Clams, and Butter Clams (see also Figure 2 1 ) , and tend to concentrate near the contact between sand and mud (Photograph No. 2 2 ). The mixture i s extremely poorly sorted. I t covers only 0 . 7 % of the bottom surface i n Fatty Basin and i s uncommon i n Useless I n l e t . ( i i ) Muddy, very coarse gravel (angular)-shell mixture (Sediment No. 9 ) : Similar to sediment No. 8 , t h i s mixture occurs i n isolat e d patches near the angular gravel deposits of sediment No. 3 , which are common i n small bays and on delta tops. The sh e l l s are largely unbroken, too, with Butter Clams, Native Oysters, and L i t t l e Neck Clams the most abundant species. The extent of t h i s mixture amounts to only 0 . 2 % of the bottom surface i n Fatty Basin, but 1 . 1 % i n Useless I n l e t , where gravel deposits are more extensive. I Rounded p e b b l e s on the u p p e r p a r t o f O y s t e r B e a c h , washed o u t o f o l d d e l t a s t r a t a , b u t u l t i m a t e l y d e r i v e d f r o m g l a c i a l d r i f t d e p o s i t s a l o n g the c r e e k bed above t h e d e l t a . Such d e p o s i t s o f r ounded p e b b l e s a r e a l s o t y p i c a l f o r s t r o n g - c u r r e n t z o n e s , s u ch as t he two g u t s and the e n t r a n c e i n t o U s e l e s s I n l e t , as d i s -c u s s e d i n t he t e x t . C o a r s e , a n g u l a r g r a v e l ana g r a v e l l y s and , expo sed a t a l o w t i d e on O y s t e r B e a c h . S h e l l s a r e common and u s u a l l y u n b r o k e n h e r e , d e r i v e d f r o m b u r r o w i n g b i v a l v e s l i v i n g b e l o w t he s u r f a c e o f the s e d i m e n t . The a n g u l a r g r a v e l i s f a i r l y t y p i c a l f o r s e d i m e n t t y p e 3-56 7- Lithdlogy of the Sediments In t h i s chapter, sediment colours, grain shape and roundness, as w e l l as surface textures of grains are b r i e f l y discussed, i n order to further r e l a t e the various sediments to t h e i r sources, to the methods of transport, and to t h e i r depositional environments. ( i ) Sediment Colours: Deposits of coarse t e r r e s t r i a l sediments, l i k e pebbles, gravel, and sand, are mostly of dark-grey to greenish-grey colours, r e f l e c t i n g the predominance of andesitic rock fragments. L o c a l l y , sands may appear lighter-grey to yellow-brownish-grey, caused by a greater abundance of quartz, feldspars, cherts, and s i m i l a r light-coloured minerals. Brownish colours are mainly due to i r o n oxides and are most common i n sediments of the i n t e r t i d a l zone. The colours of the muds are dependent upon the amount of organic matter present. Upon treatment with hydrogen peroxide, the green muds always changed t h e i r colour from olive-green to a medium grey, whereas the grey muds, which contain f a r less organic carbon, only attained a l i g h t e r hue of the same colour. Treatment with Na-dithionite and hydro-c h l o r i c acid for i r o n - and carbonate-removal resulted only i n very i n s i g -n i f i c a n t colour changes. Deposits of shell-debris appear i n various shades of very l i g h t greys, and mixtures between shells and t e r r e s t r i a l sediments may bring about numerous variations of grey colours. In the strong-current zones of the two guts and the entrance to Useless I n l e t , pebbles and gravel 57 are often overgrown with pink algae, and the entire sediment may super-f i c i a l l y appear i n t h i s colour. S i m i l a r l y , overgrowths of various other shell-secreting organisms may give l i g h t colours to an o r i g i n a l l y dark sediment. In a few areas, creeks contribute great amounts of organic detritus to the i n l e t s , and t i n y wood fragments may be abundant enough to a c t u a l l y cause colour changes i n the muds towards a dark brown. The south-delta of Fatty Basin and Oyster Beach i n Useless Inlet are good examples. ( i i ) Grain Shape and Roundness: Both sphericity and roundness of gravels and pebbles are e n t i r e l y dependent upon the origin,whether they are derived from g l a c i a l d r i f t or from l o c a l bedrock through mass wasting. The g l a c i a l l y derived coarse material i s r e l a t i v e l y well-rounded and of high s p h e r i c i t y , regardless of the rock type involved, but angular gravel and pebbles may be of very i r r e g u l a r shapes, and they consist almost exclusively of Bonanza volcanics. They have fresh surfaces, sharp edges, and even lar g e , e a s i l y weathered phenocrysts may s t i l l be preserved. In many cases, these materials can be traced to t h e i r source, usually strongly fractured bedrock exposures along the shorelines or within creek beds. Some of the debris may have been transported short distances by g l a c i a l i c e , but angular fragments are generally not found i n g l a c i a l d r i f t deposits. The angular material commonly mixes with rounded, g l a c i a l l y derived pebbles and gravels, but due to i t s greater abundance, dominates most of the coarse t e r r e s t r i a l sediments. 58 Sand-sized t e r r e s t r i a l fragments u s u a l l y have good s p h e r i c i t y , hut v a r i a b l e roundness. Both coarse and f i n e sands consist mainly of v o l c a n i c rock fragments, although the f i n e r f r a c t i o n s may have a higher percentage of monomineralic g r a i n s , which are generally h i g h l y angular. Rounded grains are scarce and consist e x c l u s i v e l y of very f i n e - g r a i n e d v o l c a n i c rock. Near outcrops of g l a c i a l clayey s i l t s , the f i n e sand f r a c t i o n s have r e l a t i v e l y abundant f r e s h , angular quartz, whereas e l s e -where the content of l i t h i c fragments i s very high (see a l s o Figure 11). The a n d e s i t i c rocks are often extremely f i n e - g r a i n e d and may p e r s i s t even i n very small fragments. Coarser-grained d i o r i t e s and g r a n o d i o r i t e s , on the other hand, d i s i n t e g r a t e r e a d i l y i n t o t h e i r con-s t i t u e n t grains of quartz, f e l d s p a r , and mafic minerals. Since these i n t r u s i v e rocks appear only i n a few small outcrops i n the immediate area of i n t e r e s t , they are a n e g l i g i b l e source f o r sediments, and v o l c a n i c rock fragments consequently dominate most sand f r a c t i o n s . Carbonate gravel and sand f r a c t i o n s are mostly h i g h l y angular and of extemely poor s p h e r i c i t y . Exceptions occur i n zones of strong currents , where t h i c k s h e l l s of b i v a l v e s l i k e oysters and s c a l l o p s may be reworked i n t o f a i r l y rounded fragments. ( i i i ) Surface Textures: Only surface textures of rounded, g l a c i a l l y derived pebbles are of i n t e r e s t , since angular fragments of l o c a l source normally show few imprints of a t r a n s p o r t i n g agent or the sedimentary environment. P i t t i n g i s very common, caused by p r e f e r e n t i a l erosion of the 59 mafic minerals i n d i o r i t e s or of phenocrysts i n some of the v o l c a n i c rocks. Percussion marks, r e s u l t i n g from c o l l i s i o n s between pebbles, are f a i r l y rare and were observed only i n a few cases on very fine-grained v o l c a n i c rocks. G l a c i a l s t r i a t i o n s may be expected as a common feature here, but were found only on very few pebbles and cobbles, even among those c o l l e c t e d d i r e c t l y from g l a c i a l d r i f t . Encrusting organisms are abundant throughout the area, with pink algae and bryozoans common i n the strong-current zones of the two guts and the mouth of Useless I n l e t , and calcareous worm tubes occurring along most rocky sections of the i n l e t perimeters and around the i s l a n d s (see Photo-graph 18 ). 60 8. Effects of the Fauna upon Sedimentation As discussed i n a previous chapter, the olive-green muds i n Fatty Basin show a lack of s t r a t i f i c a t i o n , which was attributed to the a c t i v i t i e s of burrowing organisms l i k e Ophiuroids, Pelecypods, Holothu-r i a n s , and Polychaete Worms, as wel l as to the decay processes i n i t i a t e d by bacteria within the mud. The lack of s t r a t i f i c a t i o n here seems to be i n contrast to the laminations Carter (1970) found i n the muds of Effingham I n l e t . Perhaps, the bottom waters of Effingham Inlet are t r u l y stagnant and d e f i c i e n t i n dissolved oxygen and prevent any infauna except anaerobic b a c t e r i a , which then may re s u l t i n remnants of laminations to be s t i l l preserved w i t h i n the mud. Another suggestion i s , that Carter observed the laminations only on X-ray photographs of his cores, which revealed lamina-tions otherwise hidden from observation. No such procedure was followed with the Fatty Basin cores, and i t may be w e l l possible that they also reveal remnants of laminations, i f subjected to X-ray photography. This question i s l e f t unanswered here, since more relevant importance i s seen i n the basic f a c t , that the effects of infauna and bacteria upon the s t r a t i f i c a t i o n are very strong indeed, which i s e a s i l y confirmed by o r d i -nary observation methods. Faecal p e l l e t s , believed to be the waste products of f i l t e r -feeding organisms, were found only i n two samples from Useless Inlet and Rainy Bay (92 and 122). The p e l l e t s , egg-shaped and of about 1 millimeter length, are very soft and break e a s i l y during handling, which may be one reason for t h e i r lack i n most of the collected samples. However, sim i l a r 61 faecal p e l l e t s seem to be common i n the sediments of Barkley Sound (Carter), although samples collected there have undoubtedly undergone extensive handling as w e l l . This observation suggests, therefore, that f i l t e r feed-ing organisms ac t u a l l y are far more abundant i n the open waters of the Sound than i n the r e s t r i c t e d environments of Useless I n l e t and Fatty Basin. In some areas of the Basin, notably on s h e l l deposts just o f f reef k, large s t a r f i s h e s , i n t h e i r search f o r buried clams, dig through surface sediments and turn over considerable amounts of material. The same species i s also common on sandy and gravelly sediments, wherever colonies of clams l i v e buried beneath the surface. In general, however, the effect of these starfishes upon the sedimentation may be regarded as very minor. Small hermit crabs are abundant i n Fatty Basin and Useless I n l e t . They seem to favour as t h e i r portable homes empty shells of univalves l i k e the Red Turban and the Spindle S h e l l , and consequently unbroken shells of these species are r a r e l y found i n a sediment sample. Because of t h e i r considerable abundance, the hermit crabs c l e a r l y have some influence upon the d i s t r i b u t i o n of s h e l l debris, and commonly fragments of univalve she l l s are found i n u n l i k e l y places, where they were transported by the crabs. In conclusion, i t i s apparent that the influence of s h e l l -bearing organisms upon the sedimentation i s of major importance, as has been discussed i n previous chapters on sediment d i s t r i b u t i o n , since they 62 are responsible for a large percentage of the t o t a l sediments, hut other organisms contribute only n e g l i g i b l e amounts of debris. The effects of the fauna upon d i s t r i b u t i o n of sediments are minor i n comparison to other factors l i k e currents and bottom topography, but s t r a t i f i c a t i o n of sedi-ments may be la r g e l y destroyed, as i s wel l exemplified by organisms within the olive-green mud zone. 63 9. Organic Carbon D i s t r i b u t i o n Eighteen samples (Table 6 ) were analysed f o r t h e i r t o t a l carbon contents by Can Test Laboratories of Vancouver, where the combus-t i o n furnace method was used. A l l samples had been previously treated with hydrochloric acid for carbonate removal, and organic carbon i s therefore considered to provide the t o t a l carbon content of these samples. Carbon i n the form of carbonates was disregarded i n t h i s study, since random occurrences of s h e l l fragments are often inconclusive i n reference to transporting agents and types of sediments, l a r g e l y because of the abun-dant shell-bearing fauna throughout most of the i n l e t s . The organic carbon content of a sediment i s strongly influenced by the sedimentary environment, and the dominant factors are ( i ) the p a r t i c l e size of the sediment, ( i i ) the i n f l u x of organic r e l a t i v e to t e r r e s t r i a l debris, and ( i i i ) the bottom topography and currents. Figure 19 i l l u s t r a t e s the d i s t r i b u t i o n pattern of organic carbon throughout the area of i n t e r e s t . Highest concentrations are found along the north-western shore of the Central Section i n Useless Inlet and at the south-eastern end of Fatty Basin, coinciding with locations of rap i d l y advancing deltas (type B; see chapter on "Delta Developments"). Large amounts of organic debris are transported by rapidly flowing creeks and added to the i n l e t sediments here, which results i n maxima of over 11% of organic carbon within the mud f r a c t i o n . F igure 19 Table 6 : Organic Carbon Contents (in percentages of mud fractions) Sample No. Organic Carbon (%) 1 1.85 7 1.^5 18 5.50 27 6.70 33 11.20 h9 8.75 71 5.25 75 5-1+5 87 1.95 88 2.50 90 1.25 91 1.05 92 3.35 99 1.50 102 11.10 109 1».70 125 • 5.30 R.B. o f f Small Gut 8.U5 Other high concentrations of over 8% vere found i n the "holes" of Fatty Basin and o f f the Small Gut i n Rainy Bay. Coarse organic debris, swept through the gut by strong t i d a l currents, tends to s e t t l e immediately upon entering the r e l a t i v e l y quiet-water conditions i n both Fatty Basin and Rainy Bay. Decomposition of the coarse debris then results i n high percentages of organic carbon within the mud f r a c t i o n . Most of the green mud zones are characterized by concentrations between 5 and 6%,dominantly the r e s u l t of excess production through deposi-t i o n of fine-grained phytoplanktonic debris upon the mud with i t s reducing 65 environment. pH-measurements of the water column and the near-surface mud were taken by Seki (unpubl.) on June 12, 1969. The data are p l o t t e d on Figure 20 , and i t i s evident that the mud may have e i t h e r s l i g h t l y higher or lower pH-values than the bottom waters. I f d e s t r u c t i o n of organic carbon within the mud i s exceeding i t s production through photo-synthesis i n the bottom water, the pH-value of the mud seems to be lower (more a c i d i c ) than i n the water immediately above. I f there i s more pro-duction i n the bottom water as compared to destruction of organic carbon i n the mud, the pH-value of the mud appears to be higher than that of the immediately o v e r l y i n g bottom water. S l i g h t v a r i a t i o n of organic carbon contents i n the mud may be caused by these f a c t o r s , but i s probably minor r e l a t i v e to the t o t a l q u a n t i t i e s of organic carbon produced by photosyn-t h e s i s i n the whole water column. Low concentrations of organic carbon occur i n areas dominated by grey mud, notably near deltas of type A. The water here i s generally very shallow, and deposition of organic debris i s minor compared to the vast amounts of f i n e - g r a i n e d t e r r e s t r i a l m a t e r i a l derived from g l a c i a l clayey s i l t s . Low concentrations are also found i n zones of strong currents, notably the two guts and the Outer Section of Useless I n l e t , where the sediments are without appreciable mud f r a c t i o n s . Figure 20 V a r i a t i o n of pH.- values with depth at 3 s t a t i o n s i n Patty Basin on June 1 2 , 1 9 6 9 . (Data from Seki, 1 9 6 9 ) o = bottom sediment (mud) 66 10. Nature and D i s t r i b u t i o n of the Shell-bearing Fauna The r e l a t i v e l y r e s t r i c t e d environment of Useless Inlet and espe c i a l l y Fatty Basin r e f l e c t s upon the shell-bearing fauna of these i n l e t s . The shel l s of many organisms are much smaller than those found i n the more open waters of Barkley Sound, notably molluscs such as M y t i l u s , Chlamys , Donax, Eumilaria, Astrea, Ocenabra, and Tegula. A few genera are e n t i r e l y absent (e.g. H a l i o t i s and O l i v e l l a ) , but others seem to prefer the i n l e t environment and are more common here, notably Nassarius, Saxi-domus , and a Rhynchonellid-Brachipod (genus not i d e n t i f i e d ) . A complete l i s t of the s h e l l f i s h genera found i n Fatty Basin and Useless Inlet i s presented i n Table 7. D i s t r i b u t i o n of the various genera i s e n t i r e l y dependent upon the sedimentary environments. Within the mud zone, few shell-bearing organisms are found; these are mostly bivalves such as Mya and Yoldia. Muddy sands and gravels i n bays and on d e l t a tops are inhabited by Vene-rupis , Saxidomus, Clinocardium and, occasionally, Ostrea. Only few genera occur i n the strong-current zones; they are mostly r e s t r i c t e d to that environment and include Glycimeris, Humilaria, and F e l a n i e l l a . The vast majority of shell-bearing organisms i s found on bed-rock and boulder slopes along the i n l e t perimeters and around islands. Barnacles and calcareous worm tubes are by far most abundant and provide the bulk of the s h e l l debris accumulating below the slopes , but most of the molluscan univalves (gastropods) and a l l of the brachipods are also r e s t r i c t e d to t h i s environment. 6? Table 7 : Bivalves and Univalves i n F a t t y Basin and Useless I n l e t Species or generic names are l i s t e d i n approximate order of abundance of the organisms; i n one case (Rhynchonellida) only the order was i d e n t i f i e d . Among the u n i v a l v e s , the f i r s t 8 species are common, but a l l others are very r a r e . Whenever known, popular names f o r the s h e l l s are presented i n brackets. Bivalves 1. Venerupis .iaponica ( L i t t l e Neck Neck Clam) 2. Saxidomus giganteus (Butter Clam) 3. Mytilus e d u l i s (Common Blue Mussel) 1*. Clinocardium n u t t a l l i (Cockle) 5- Ostrea l u r i d a (Native Oyster) 6. Pododesma (?) (Jingle S h e l l ) 7. Rhynchonellida (Order) 8. Mya a r e n a r i a (Mud Clam) 9- Chiamys (?) (Scallop) 10. Ostrea (?) (Japanese Oyster) 11. Donax (?) (Sunset S h e l l ) 12. Glycimeris (?) (?) 13. Humilaria (?) (?) l i t . F e l a n i e l l a (?) (?) 15- Y o l d i a (?) (?) 16. Nuculana (?) (?) 17- Solen (?) (?) 68 Table 7 Continued Univalves 1. Nassarius fossatus 2. S e a r l e s i a d i r a 3. Crepidula l i n g u l a t a k. Astrea gibberosa 5. B i t t i u m e s c h r i c h t i i 6. Acmaea persona 7. Acmaea t e s t u d i n a l i s 8. Ocenabra i n t e r f o s s a 9. Lacuna v a r i e g a t a 10. Homalopoma carpenter 11. Tegula p u l l i g o 12. L i t t o r i n a sitkana 13. M i t r e l l a gansapata 1^. Ceratostoma f o l i a t a 15. Tegula fu n e b r a l i s 16. Crepidula nummaria 17- Margaritus p u p i l l u s 18. Margaritus l i r u l a t u s 19- Thais emarginata 20. Acteocina c u l c i t e l l a 21. P o l i n i c e s (?) 22. Megatebennus bimaculatus 23. Diodora aspera 2h. Acmae mitra 25. P u n c t u r e l l a (?) (Channelled Dog Whelk) (Spindle S h e l l or Dire Whelk) (Wrinkled S l i p p e r S h e l l ) (Red Turban) (Threaded Bittium) (Mask Limpet) (Plate Limpet) (Sculptured Rock S h e l l ) (Variegated Chink S h e l l ) (Carpenter Dwarf Turban) (Dusky Turban) (Sitk a L i t t o r i n e ) (Dove S h e l l ) (Leafy Hornmouth) (Black Top S h e l l ) (White S l i p p e r S h e l l ) (Puppet Margerite) ( L i r u l a t e Margerite) (Short-spired Purple) (Pillowed Lathe S h e l l ) (Lewis Moon S n a i l ) (Spotted Keyhole Limpet) (Rough Keyhole Limpet) (Whitecap Limpet) (?) Figure 21 1§H Barnacles S I Worm Tubes Venerupis Saxidomus Clinocardium Distribution of main Shell-bearing Fauna in 69 The d i s t r i b u t i o n of the most common sh e l l - b e a r i n g organisms i s i l l u s t r a t e d on Figure 21. Foraminifera were i d e n t i f i e d by Dr. Bruce Cameron of the Geological Survey of Canada and are l i s t e d on Table 8 . No s i g n i f i c a n t d i s t r i b u t i o n a l pattern was recognized within the i n l e t s , but i n Fatty Basin, E l p h i d i e l l a hannai (Cushman, Grant) appears to strongly predominate over other species. Elphidium fax (Nicol) i s common throughout Useless I n l e t and Rainy Bay, but rare i n the Basin, and Quinqueloculina sp. seems to concentrate near the strong-current zone of the Big Gut. The f o r a m i n i f e r a population i s f a r more v a r i e d i n the more open waters of Useless I n l e t and e s p e c i a l l y Rainy Bay than i n Fa t t y Basin, and a l l species found are al s o common on r e l a t i v e l y shallow sections of the cont i n e n t a l s h e l f o f f Vancouver Island (Cameron, personal communication). The r e l a t i v e l y r e s t r i c t e d nature of Useless I n l e t , t h e r e f o r e , appears to have l i t t l e e f f e c t upon the fo r a m i n i f e r a assemblage, whereas the strongly r e s t r i c t e d environment of shallow Fatty Basin i s favoured by the shallow-water species, E l p h i d i e l l a hannai (Cushman, Grant). 70 Table 8 : Foraminifera i n Fatty Basin, Useless I n l e t , and Rainy Bay ( l i s t e d i n approximate order of abundance). 1. E l p h i d i e l l a hannai (Cushman, Grant) 2. Elphidium fax (Wicol) 3. Quinqueloculina sp. k. Discanomalina japonica (Asano) 5. C i b i c i d e s lobatulus (Walker, Jacob) 6. Eponides repandus ( F i c h t e l , Moll) 7. Cribrostomoides crassimargo (Norman) 8. F l o r i b u s basispinatus (Cushman, Moyer) 9- Cribroelphidium frigidum (Cushman) 10. G l a b r a t e l l a ornatissima (Cushman) 11. Dyocibicides b i s e r i a l i s (Cushman, Valentine) 12. R o t a l i a columbiensis (Cushman) 13. Planorbulina sp. Ik. Elphidium sp. Note: "sp." = species not i d e n t i f i e d . I d e n t i f i c a t i o n by Dr. Bruce Cameron, Geological Survey of Canada. 5 ft-wide g l a c i a l groove on reef 1 i n Patty Basin (view i s towards north-east). Photograph No« 2 0 ; Surface of olive-green mud. Pew s h e l l s of Mya. I G r a v e l l y sand o f s ed imen t t y ge 6, e xpo sed a t a v e r y l o w t i d e on the n o r t h - e a s t e r n p e r i m e t e r o f P a t t y B a s i n . G l a c i a l d r i f t d e p o s i t s o c c u r above t h e b o u l d e r zone to t h e l e f t o f t h e p i c t u r e . T y p i c a l d e p o s i t o f s h e l l d e b r i s ( s e d i m e n t t y p e 12) b e l o w b e d r o c k s l o p e s , e x -po sed d u r i n g an e x c e p t i o n -a l l y l o w t i d e . B a r n a c l e s c o v e r most o f t h e i n t e r -t i d a l r o c k f a c e s , and t h e i r s h e l l d e b r i s a c c o u n t s f o r more t h a n 80 p e r c e n t o f t h e s e d i m e n t h e r e . 16 71 SUMMARY AND CONCLUSIONS In many aspects, notably physiography and sedimentology, Useless I n l e t i s probably t y p i c a l f o r many i n l e t s with shallow s i l l s at t h e i r mouths, whereas Fatty Basin, at f i r s t observation, appears to represent an exceptional environment, because of small s i z e , shallow water, and hi g h l y r e s t r i c t e d connection with the ocean. Comparison of structures and s e d i -mentation c h a r a c t e r i s t i c s , however, reveals much s i m i l a r i t y i n the geology of these two i n l e t s , and i n t h i s study, Fatty Basin.is considered to be a small-scale model of many i n l e t s with r e s t r i c t e d entrances on a mountainous, g l a c i a t e d coast. Because of ready a c c e s s i b i l i t y of most sections of the Basin, accuracy i n d e t a i l i s beli e v e d to be good, notably with respect to the d i s t r i b u t i o n of sediments, and general conclusions regarding the g e o l o g i c a l environment may be appli c a b l e to many s i m i l a r , i f la r g e r i n l e t s on t h i s type of coast. 1. The S e t t i n g Useless I n l e t c o n s i s t s of three d i f f e r e n t p a r t s , the ( i ) Outer Section, a s t r a i g h t channel with i r r e g u l a r bottom topography, sandy s e d i -ments, steep s i d e s , and a r e l a t i v e l y r e s t r i c t e d entrance with a shallow, rocky s i l l ; the wide ( i i ) Central Section with strongly embayed shore-l i n e s and muddy sediments on a smooth bottom topography; and the ( i i i ) Inner Section, which i s shallow and narrow and has a highly i r r e g u l a r bottom topography. Fatty Basin appears as an elongate, shallow bowl of 72 10k f t (32 m) maximum depth, with two very narrow and shallow entrance passages, the "guts". The bottom topography i s generally smooth and dominated by muddy sediments, but several bedrock exposures r i s e up above the Low-tide Level. The geology of the area i s dominated by the Bonanza Subgroup (Upper T r i a s s i c to Lower J u r a s s i c ) , which consists mainly of dark-greenish to reddish, andesite flows, and by sporadic occurrences of massive lime-stones or limestone b r e c c i a s of the Quatsino Formation (Upper T r i a s s i c ) . Hornblende d i o r i t e (West Coast D i o r i t e ) i s found i n extensive exposures on Tzartus Island, but only i n two small outcrops i n Fatty Basin and at the mouth of Uchucklesit I n l e t . Granodiorites of the Island Intrusions (Middle to Late J u r a s s i c ) occur west of the area of i n t e r e s t , where they are widespread throughout the c e n t r a l s e c t i o n of the Barkley Sound Region. North of Uchucklesit I n l e t , b a s a l t i c lavas of the Karmutsen Formation (Lower to Upper T r i a s s i c ) form very extensive exposures; they are probably a major source f o r the g l a c i a l sediments found i n the Fatty Basin area. Although t h e i r present shapes are l a r g e l y the r e s u l t s of scouring by g l a c i a l i c e flows, both F a t t y Basin and Useless I n l e t are thought to be of s t r u c t u r a l o r i g i n , because d i r e c t i o n a l trends of the many f a u l t s and fr a c t u r e zones are also followed by the major shorelines. On the west coast of Vancouver Island and the B.C. mainland, f j o r d s commonly trend at large angles to the general d i r e c t i o n s of Pleistocene i c e flow, and s i m i l a r to the l i m i t e d area under consideration i n t h i s study, i n l e t s i n most regions of t h i s coast tend to follow two preferred d i r e c t i o n s . A s t r u c t u r a l 73 o r i g i n , with subsequent erosion by water and i c e , i s therefore suggested f o r most of the c o a s t a l depressions i n B r i t i s h Columbia. Si m i l a r views were presented by Peacock i n 1935, and i t i s proposed here that s t a t i s t i c a l evaluation of a t t i t u d e s of a l l known major f a u l t s on the B.C. coast and of d i r e c t i o n a l trends of f j o r d s and i n l e t s be undertaken, i n order to p o s s i b l y confirm t h i s suggestion. U p l i f t of the land, probably due to i s o s t a t i c response a f t e r g l a c i a t i o n , was at l e a s t 20 f t here during the l a s t 7000 years, i f a e u s t a t i c sea l e v e l r i s e of about 10 f t i s assumed. This l a t t e r f i g u r e , however, represents a minimum, and much l a r g e r values have been proposed by some workers (e.g. Kennedy, Hopkins; from diagram by Mathews, 1970, page 694). Obviously, the evidence i n d i f f e r e n t l o c a l i t i e s i s c o n f l i c t i n g , and the true amount of e u s t a t i c sea l e v e l r i s e i s s t i l l l a r g e l y uncertain. Consequently, the value of 20 f t f o r u p l i f t of the land i n t h i s area i s t e n t a t i v e , and any excess over 10 f t i n absolute r i s e of the sea l e v e l during the l a s t 7000 years w i l l increase the t o t a l u p l i f t by the same amount. Within Fatty Basin, the p h y s i c a l oceanography i s strongly a f f e c t e d by the r e s t r i c t e d nature of the entrance passages, where currents generated by t i d a l exchange and head d i f f e r e n c e i n water l e v e l are e x c e p t i o n a l l y strong. As a r e s u l t , s t r a t i f i c a t i o n of inflowing waters i s destroyed, and good exchange of the e n t i r e water column takes place during most of the year. S a l i n i t y and temperature gradients are consequently always l e s s i n the Basin than i n the outside waters, and stagnant, de-oxigenated bottom water appears t o be r a r e , even i n the deepest sections. The water entering the Basin over the shallow s i l l s i s mostly surface water from the euphotic zones, where concentration of phytoplankton i s much higher than i n deeper waters. Great amounts of organic debris are therefore swept in t o F atty Basin during each upcoming t i d e and are w e l l d i s t r i b u t e d throughout the e n t i r e water column by the strong currents. Outgoing water during the ebb t i d e c a r r i e s only part of t h i s phytoplank-t o n i c d e b r i s , and as a r e s u l t , F a t t y Basin appears to be a large trap f o r suspended organic matter. I n l e t s with r e s t r i c t e d entrances are common on the B.C. coast, because g l a c i a l scour tends t o be more intense i n the upper sections of a f j o r d than near i t s mouth, which r e s u l t s i n entrance s i l l s of bedrock or g l a c i a l d r i f t . In many such i n l e t s , t i d a l f l u s h i n g i s probably very e f f e c t i v e i n preventing development of t r u l y stagnant waters during most of the year, but f j o r d s of great length and depth may have extensive sections .entirely unaffected by the strong t i d a l currents generated over the shallow entrance s i l l . 75 2. The Sediments Rate of Sedimentation Deposition of t e r r e s t r i a l and organic debris from suspension i s i n the order of 900 grams per square meter and year i n Fatty Basin, but d a i l y rates of sedimentation may vary considerably with the seasons. They reach a maximum of over 10 g/m^/day during l a t e summer, when phytoplank-to n i c debris from the euphotic zone i s deposited i n great q u a n t i t i e s , and minima of l e s s than 2 g/m^/day i n f a l l and spring. In l a t e winter, a small increase i n sedimentation rate to about 3 g/m^/day i s probably caused by increased p r e c i p i t a t i o n and r e s u l t a n t runoff during that time of the year. These v a r i a t i o n s i n sedimentation r a t e s , l a r g e l y caused by abundance or l a c k of phytoplankton i n the water column, demonstrate the great influence of fine-g r a i n e d organic debris upon the muds i n Fatty Basin. These are therefore always r i c h i n organic matter, except when g l a c i a l clayey s i l t s i n nearby shore deposits provide abundant fine- g r a i n e d t e r r e s t r i a l m a t e r i a l . Clays and Heavy minerals The clay minerals i n Fatty Basin and Useless I n l e t are almost e x c l u s i v e l y members of the c h l o r i t e group, associated with only minor amounts of i l l i t e . Other minerals, such as k a o l i n i t e , smectite, and v e r m i c u l i t e , are e i t h e r absent or present only i n traces not detectable by ordinary X-ray d i f f r a c t i o n methods. 76 The heavy mineral s u i t e i s generally dominated by epidote, clinopyroxene (augite), and abundant opaque minerals (magnetite). Horn-blende, which i s widespread i n sediments of most of the Barkley Sound region (Carter, 1970), was common only i n few of the samples, and acces-sory minerals, mostly sphenes, are rare. C h l o r i t e was always present, but never i n s i g n i f i c a n t q u a n t i t i e s , and appears to concentrate i n the s i l t and clay f r a c t i o n s rather than i n the f i n e sand f r a c t i o n s used f o r heavy mineral a n a l y s i s . Both clays and heavy minerals c l e a r l y r e f l e c t the nature of the source rocks, which are mainly Bonanza andesites and Karmutsen b a s a l t s . These u n i t s are very r i c h i n c h l o r i t e , and both, e s p e c i a l l y the Karmutsen b a s a l t s , contain abundant clinopyroxene and epidote. No other rock u n i t i n the c e n t r a l section of Vancouver Island c a r r i e s a l l these minerals i n s i m i l a r abundances, or i s exposed t o any s i g n i f i c a n t extent i n the proba-ble g l a c i a l passage from the Henderson Lake region to Fa t t y Basin. Kar-mutsen and Bonanza v o l c a n i c s , t h e r e f o r e , c o n s t i t u t e the ultimate source f o r the f i n e sands, s i l t s , and clays within the area under consideration, where these materials are derived from g l a c i a l d r i f t and clayey s i l t deposits. Nature and D i s t r i b u t i o n of Sediments Least sorted sediments are u s u a l l y mixtures of s h e l l s , t e r r e s -t r i a l g r a v e l , sand, and mud. Such assemblages may vary g r e a t l y i n mean s i z e , even i f other s t a t i s t i c a l parameters are s i m i l a r , because s l i g h t changes i n abundance of any one of these i n d i v i d u a l materials may r e s u l t i n d i s t i n c t s h i f t s of the mean s i z e of the sediment as a whole. Best s o r t i n g , on the other hand, i s found i n well-washed t e r r e s t r i a l sand and 77 g r a v e l s , where mixing of d i f f e r e n t sedimentary materials i s i n s i g n i f i c a n t . Since most of the sediments contain at l e a s t some mud, p o s i t i v e ( f i n e ) skewness i s very common, except f o r some of the t e r r e s t r i a l sands, where strong currents have removed most of the mud f r a c t i o n . Even i f present i n only small amounts, s i l t s and clays strongly influence the skewness of any sediment. S h e l l fragments commonly introduce a.poor s o r t i n g i n t o coarse and medium s i z e - f r a c t i o n s , but are rare i n the s i l t - s i z e range. Mixtures of s h e l l s and t e r r e s t r i a l m a t e r i a l , t h e r e f o r e , are u s u a l l y p l a t y k u r t i c , because of l e s s s o r t i n g i n the coarse f r a c t i o n s as compared to the f i n e s i l t s and c l a y s . R e l a t i v e l y homogeneous carbonate or t e r r e s t r i a l sands with appreciable mud f r a c t i o n s , however, are gener a l l y l e p t o k u r t i c , be-cause here the bulk of the coarse debris i s b e t t e r sorted than the f i n e -grained m a t e r i a l . Eight groups of sediments were defined on the basis of s t a t i s t i -c a l parameters. Further s u b d i v i s i o n as to r e l a t i v e contents of carbonate versus t e r r e s t r i a l debris and of rounded versus angular m a t e r i a l r e s u l t e d i n r e c o g n i t i o n of t h i r t e e n d i f f e r e n t sediment types , which are shown on two accompanying d i s t r i b u t i o n maps. T o t a l bottom surface areas f o r each of these sediment types, as well as for bedrock exposures and angular boulders, which are regarded as an a d d i t i o n a l sediment type, are presented on Table 5. These f i g u r e s r e f e r t o true surface areas, determined from width and length of exposures and from the approximate angle of slopes. Below, short d e s c r i p t i o n s of the sediments, t h e i r general mode of occurrence wi t h i n the i n l e t s , and t h e i r extent i n percentages of t o t a l 78 bottom surface i n F a t t y Basin and Useless I n l e t are presented. They may be roughly grouped i n t o (A) boulders,( B) pebbles and g r a v e l s , (C) t e r -r e s t r i a l sand, (D) s h e l l d e b r i s , (E) muds, and (F) coarse g r a v e l - s h e l l mixtures. (A) Boulders(Sediment No. 2): Large, angular boulders form steeply sloping accumulations along extensive sections of the i n l e t perimeters, u s u a l l y below h i g h l y f r a c t u r e d bedrock. (3.4% i n Fatty Basin, 1.3% i n Useless I n l e t ) (B) Pebbles and Gravels ( i ) Mostly angular, coarse gravel with few s h e l l  fragments (Sediment No. 3): This gravel i s common on some d e l t a tops i n the near-shore zone of some bays, and o c c a s i o n a l l y below strongly f r a c t u r e d bedrock faces. (0.6% i n F a t t y Basin, k.3% i n Useless I n l e t ) ( i i ) Rounded pebbles and gravel (Sediment No. 7) This coarse, rounded m a t e r i a l i s c h a r a c t e r i s t i c f or the strong-current zones of the two guts and the mouth of Useless I n l e t ; i t i s mostly derived from g l a c i a l d r i f t deposits. (1.2% i n F a t t y Basin, 3.2% i n Useless I n l e t ) (C) T e r r e s t r i a l Sands ( i ) Medium to f i n e sand (Sediment No. U): These sands occur i n zones of medium-strong currents (velo-c i t y up t o 5 knots) and are p a r t i c u l a r l y extensive i n the Outer Section of Useless I n l e t . They are also found i n many bays below the near-shore gr a v e l s , from which they were removed through winnowing by surface currents and, to a l e s s e r degree, waves. (1.4% i n F a t t y Basin, 12.9% (•) i n Useless I n l e t ) 79 ( i i ) Coarse sand with abundant gravel arid pebbles (Sediment No. 6 ) : This sediment i s u s u a l l y confined to the near-shore zone of bays with abundant sediment supply, as the r e s u l t of winnowing a c t i o n that removes the f i n e and medium sands. (2 .8% i n Fatty Basin, 1.7% i n Useless I n l e t ) ( i i i ) Coarse sand with some g r a v e l , pebbles, arid s h e l l s (Sediment No. 5): R e l a t i v e l y uncommon, t h i s sediment occurs near g r a v e l or sand deposits and i s ev i d e n t l y a mixture of both. No size-gradation as i n sediment No. 6 between the coarse and the f i n e r f r a c t i o n s was observed. (0.5% i n Fatty Basin, 1.1% i n Useless I n l e t ) (D) S h e l l Debris ( i ) Coarse s h e l l debris with few t e r r e s t r i a l fragments (Sediment No. 12): These s h e l l deposits occur mostly i n a narrow zone along the base of steep bedrock and boulder slopes, and i n hollows between boulders and on bedrock. Most of the debris i s derived from barnacles, which are very abundant i n the i n t e r t i d a l zone. (2.8% i n Fa t t y Basin, 3.6% i n Useless I n l e t ) ( i i ) Medium-sized s h e l l d e b r i s , very muddy and with abundant  t e r r e s t r i a l gravel (Sediment No. 10): The sediment i s u s u a l l y found below deposits of coarse s h e l l debris (No. 12), or where steep rock slopes reach down d i r e c t l y to the mud zone. (k.h% i n Fatty Basin, 3.8% i n Useless I n l e t ) 80 ( i i i ) Fine to very f i n e s h e l l hash (Sediment No. l l ) : This sediment i s rare and occurs only i n few patches below coarser s h e l l deposits near the mud zone, where the fine-g r a i n e d s h e l l fragments were concentrated a f t e r winnowing of the coarser s h e l l m a t e r i a l . (0.1% i n Fa t t y Basin, uncommon i n Useless I n l e t ) (E) Muds ( i ) Olive-green mud r i c h i n organic matter (Sediment No. 15): This mud i s the most common sediment throughout the i n l e t s , and accumulates i n areas of weak bottom currents, u s u a l l y the c e n t r a l parts of the i n l e t s . I t i s gene r a l l y r i c h i n organic carbon (average 5 - 6%) and recei v e s abundant organic matter i n the form of phytodetritus from the euphotic zone. (70.6% i n Fa t t y Basin, 49.5% i n Useless I n l e t ) ( i i ) Olive-green mud with abundant small s h e l l fragments (Sediment No. ik): This sediment i s a mixture of green mud with numerous small s h e l l fragments, which are winnowed out of deposits of coarse s h e l l d ebris. It u s u a l l y occurs i n narrow zones below s h e l l deposits along the base of rocky slopes. (2.2% i n Fa t t y Basin, 1.9% i n Useless I n l e t ) ( i i i ) Grey Mud (Sediment No. 13): This mud i s mostly derived from g l a c i a l clayey s i l t s , and i t i s r e s t r i c t e d to bays with exposures of these s i l t s on the shore or on the banks of an inflowing creek. (2.0% i n Fa t t y Basin, 7-6% i n Useless I n l e t ) (F) Coarse Shell-Gravel Mixtures ( i ) Coarse, muddy mixture of s h e l l s with gravel arid sand (Sediment No. 8): This sediment occurs i n a few i s o l a t e d areas near deposits 81 of g r a v e l l y sand and i s never very extensive. (0.7% i n Fatty Basin, uncommon i n Useless I n l e t ) ( i i ) Muddy, very coarse angular gravel - s h e l l mixture (Sediment Wo. 9): This mixture i s s i m i l a r to sediment No. 8 and i s found near deposits of angular g r a v e l . (0.2% i n F a t t y Basin, 1.1% i n Useless I n l e t ) Bedrock occurs extensively along the i n l e t perimeters, around the i s l a n d s , and i n s e v e r a l exposures that r i s e only s l i g h t l y above the muddy bottom. About h0% of i t i s strongly f r a c t u r e d , whereas 60% i s without s i g n i f i c a n t j o i n t s and has g l a c i a l l y smoothened, rounded surfaces. Bedrock exposures amount to about 6.8% of the bottom surface area i n F a t t y Basin, and 8.0% i n Useless I n l e t . Sedimentary Environments From the d i s t r i b u t i o n of sediments, f i v e sedimentary environ-ments are defined f o r Useless I n l e t and Fatty Basin; they are the mud zone, the rock slopes, the beaches, the d e l t a s , and the strong-current zones, a l l the r e s u l t s of v a r i a t i o n s i n currents, topography, and a v a i l a -b i l i t y of sediments; wave act i o n i s g e n e r a l l y of minor in f l u e n c e . R e l a t i v e importance of these f a c t o r s v a r i e s with each of the sedimentary environ-ment s. The mud zone i s characterized by olive-green muds with a reducing environment and r e l a t i v e l y high contents of organic carbon. I t i s r e s t r i c -t e d to areas with weak bottom currents, and most of the organic debris i s derived from phytoplankton i n the euphotic surface waters. The infauna 82 consists of a few genera of mud dwellers, such as polychaete worms, ophiuroids , y o l d i a , and mya, which may he l o c a l l y common. Steep bedrock and boulder slopes are extensive along the p e r i -meters and around the i s l a n d s . Sedimentation here i s dominated by s h e l l d e b r i s , notably barnacle plates and calcareous worm tubes, which accumu-l a t e along the base of the slopes and i n hollows on bedrock and between boulders. The zone i s generally well-washed by currents and hosts most of the i n l e t fauna. Beaches here include a l l sections of the i n l e t perimeters not dominated by bedrock and boulder slopes or by d e l t a developments. They are g e n e r a l l y l o c a t e d i n bays with shore exposures of g l a c i a l d r i f t , where the inflow c o n s i s t s only of small t r i c k l e s . Pebbly sediments characterize the i n t e r t i d a l zone, and gravels or g r a v e l l y sands are found at and below low-tide l e v e l . Towards depth, a gradation to f i n e sand occurs as the r e s u l t of winnowing of the near-shore gravels. The sand f i n a l l y dips beneath the ubiquitous green mud of the mud zone. The fauna here c o n s i s t s dominantly of sand-burrowing b i v a l v e s , such as venerupis, saxidomus, and clinocardium. Abundant unbroken s h e l l s of these genera accumulate near the contact with the mud zone, where they cause extremely poorly sorted mixtures of sediments. Deltas are common i n the area under co n s i d e r a t i o n , and two types may be di s t i n g u i s h e d . Type A i s b u i l t by sluggish creeks, where abundant fi n e - g r a i n e d m a t e r i a l i s derived from g l a c i a l clayey s i l t deposits. The dominant sediment i s a grey, s i l t y mud, and top- and foreset slopes are i n d i s t i n c t because of slow deposition. Type B, on the other hand, i s b u i l t by turbulent creeks of steep gradient, and abundant coarse debris 83 i s provided from g l a c i a l d r i f t deposits. These deltas have a r a p i d rate of advance, and top- and foreset slopes are w e l l developed. Strong-current zones with very high flow v e l o c i t i e s are found i n the two guts and at the mouth of Useless I n l e t . Fine-grained m a t e r i a l i s removed, and the dominant surface sediment consists of rounded gravel and pebbles, probably the coarse, immobile f r a c t i o n of g l a c i a l d r i f t . In areas of medium-strong currents (about h knots), most notably the Outer Section of Useless I n l e t , t e r r e s t r i a l sands form the predominant surface sediment. The l i m i t e d s h e l l - b e a r i n g infauna i n these zones con-s i s t s of genera such as g l y c i m e r i s , h u m i l a r i a , and f e l a n i e l l a . L i t h o l o g y of the Sediments The colours of t e r r e s t r i a l sediments coarser than very f i n e sands are dominated by dark-grey to greenish hues, caused by the great abundance or exclusive presence of a n d e s i t i c rock fragments. Fine-grained sediments, notably those of the mud zone i n the c e n t r a l parts of the i n l e t s , are mostly of dark olive-green colours , due to high concentrations of organic matter. Grey muds are derived from shore exposures of g l a c i a l clayey s i l t of the same colour and mineralogy. Deposits of s h e l l debris appear i n various shades of very l i g h t grey, and overgrowths by s h e l l -s e c r e t i n g organisms commonly give l i g h t colours to otherwise dark, coarse t e r r e s t r i a l p a r t i c l e s . S p h e r i c i t y and roundness values for t e r r e s t r i a l pebbles and gravel are dependent upon the o r i g i n of the m a t e r i a l , whether i t i s derived from l o c a l bedrock exposures or from g l a c i a l d r i f t . Coarse g l a c i a l debris 81+ i s u s u a l l y rounded and of good s p h e r i c i t y , whereas fragments from l o c a l sources are h i g h l y angular and of i r r e g u l a r shapes. The angular material appears to be much more abundant among the coarse f r a c t i o n s , and a predomi-nant i n f l u e n c e of l o c a l l y derived debris i s suggested. Coarse fragments, t h e r e f o r e , are mostly of l o c a l o r i g i n , whereas f i n e sands, s i l t s , and clays are derived dominantly from g l a c i a l deposits, as was discussed e a r l i e r . P i t t i n g i s the most common feature i n regard to surface textures of rounded pebbles; percussion marks and g l a c i a l s t r i a t i o n s are rare. Encrusting organisms are very abundant on the coarse sediments of the strong-current zones, but may also be found along most rocky sections of the i n l e t perimeters. Organic carbon Organic carbon contents of the mud f r a c t i o n s i n sediments reach maxima of over 11% near the mouths of turbulent creeks , where abundant fin e - g r a i n e d organic debris i s deposited on d e l t a f r o n t s . Throughout most of the c e n t r a l sections of the i n l e t s , however, where the sediments are dominated by olive-green mud, the content i n organic carbon i s between 5 and 6%. S i m i l a r values for r e l a t e d sediments throughout the Barkley Sound region were reported by Carter (1970), and a content of 5 to 6 % appears to be a. c h a r a c t e r i s t i c value f o r most of the green muds. The organic matter i n these sediments i s p r i m a r i l y derived from phytoplankton i n the euphotic zone. Low values of l e s s than 2% of the mud f r a c t i o n were found i n the grey muds on deltas of type A, where the supply of t e r r e s t r i a l s i l t s and 85 clays g r e a t l y exceeds that of organic d e b r i s . The organic carbon content w i t h i n a sediment i s d i r e c l y r e l a t e d to the s i z e of the mud f r a c t i o n , which i s a function of the current strength, and to the supply of organic debris. Because of i t s molecular nature, most of the organic carbon i s associated only with very f i n e - g r a i n e d sediment f r a c t i o n s and i s uncommon i n sands and coarser m a t e r i a l s , unless s i l t s and clays are present as w e l l . Consequently, zones of medium and strong currents, where the mud f r a c t i o n i s l a r g e l y removed, have c h a r a c t e r i s t i c a l l y low contents of organic carbon, whereas high contents are commonly found i n muddy sediments. Within the muds, the d i s t r i b u t i o n of organic carbon i s p r i m a r i l y dependent upon the supply of organic d e t r i t u s , as was shown above f o r F a t t y Basin and Useless I n l e t . Shell-bearing fauna Most of the s h e l l - b e a r i n g fauna of the west coast of Vancouver Island i s also found i n Useless I n l e t and Fatty Basin. The r e l a t i v e l y quiet water conditions i n these r e s t r i c t e d i n l e t s , however, r e s u l t i n s h e l l -s i z e reduction of many genera. A few species of s h e l l f i s h e s , which require the strongly agitated waters of the open coast, are e n t i r e l y absent, whereas others appear to favour the i n l e t environment. Apart from a few mud dwellers, such as mya and y o l d i a , the mud zone i s sparsely inhabited by s h e l l f i s h e s . Sand-burrowing b i v a l v e s , mostly venerupis, saxidomus, and clinocardium, predominate the beaches and some of the d e l t a s , and only few genera, such as glycimeris and h u m i l a r i a , occur i n the zones of strong currents. The majority of the s h e l l - b e a r i n g fauna i s found i n the rock-slope environment along the i n l e t perimeters, where currents and steep gradients prevent s i g n i f i c a n t accumulations of mud. Barnacle p l a t e s , derived from the i n t e r t i d a l zones, and calcareous worm tubes are the predominant constituents of the s h e l l debris deposited on and below the slopes. 87 3. General Conclusions The f j o r d s and i n l e t s on the west coast of Vancouver Island and the B r i t i s h Columbia mainland are mostly of s t r u c t u r a l o r i g i n ; t h e i r present shapes are the r e s u l t s of subsequent erosion by water and i c e . U p l i f t of the land i n the F a t t y Basin area was i n excess of 20 f t during the l a s t 7000 years, probably due to i s o s t a t i c response; upward movements appear to continue at present at a very slow r a t e . Useless I n l e t and e s p e c i a l l y Fatty Basin act as traps f o r phyto-planktonic debris because of shallow entrance s i l l s . Phytoplankton i s p a r t i c u l a r l y abundant during summer, when i t constitutes most of the f i n e -grained m a t e r i a l deposited from suspension, and o r g a n i c - r i c h sediments are consequently widespread within the i n l e t s . The strong currents generated over the shallow s i l l s cause good exchange of the e n t i r e water column, and stagnant water conditions are very rare i n the i n l e t s . Despite well-oxigenated bottom waters, the organic-r i c h muds always form a strongly reducing environment. Fine-grained t e r r e s t r i a l debris i s derived mainly from g l a c i a l deposits, whereas l o c a l bedrock exposures provide the majority of coarse sands, g r a v e l , and pebbles. The source area for most of the g l a c i a l s e d i -ments i s to the north of F a t t y Basin, i n the Henderson Lake region, where the geology i s dominated by Karmutsen b a s a l t s . A wide, U-shaped v a l l e y extends from that area to Uchucklesit I n l e t and Fatty Basin; i t probably was a major g l a c i a l passage during the Pleistocene. 88 F i v e sedimentary environments i n Fatty Basin and Useless I n l e t determine the d i s t r i b u t i o n of sediments. They are defined as the mud zone, "bedrock and "boulder slopes, beaches , d e l t a s , and strong-current zones. The mud zone i s the most extensive environment and accounts f o r about 73% and 57% of the t o t a l bottom surface i n Fatty Basin and Useless I n l e t , r e s p e c t i v e l y . I t i s characterized by olive-green muds and occurs i n the c e n t r a l parts of the i n l e t s , where bottom currents are weak. T e r r e s t r i a l sands, g r a v e l , and pebbles predominate the beach environment (5% of the bottom surface i n Fa t t y Basin, h% i n Useless I n l e t ) , the deltas (3% i n Fatty Basin, 5% i n Useless I n l e t ) , and the strong-current zones ( l % i n Fatty Basin, a large 16% i n Useless I n l e t ) . The rock-slope environ-ment i s characterized by deposition of s h e l l d e b r i s , notably barnacle p l a t e s , along the base of the slopes, and i t accounts f o r approximately 18% of the bottom surface i n both F a t t y Basin and Useless I n l e t . The t h i c k s h e l l deposits are s t e a d i l y buried by mud and may p o s s i b l y be pre-served i n the geologic record, r e s u l t i n g i n lenses of a rather unusual barnacle limestone. Accumulations of boulders as w e l l as exposures of strongly f r a c t u r e d bedrock provide s h e l t e r f o r large crustaceans, such as lo b s t e r s and crabs, and sections of the rock-slope environment therefore c o n s t i t u t e a p r e f e r r e d habitat f o r these organisms. Beaches o f f e r l i t t l e s h e l t e r , but may provide s u f f i c i e n t food, whereas the e n t i r e mud zone, the d e l t a s , and the strong-current zones are e s s e n t i a l l y unfavorable environments f o r crustaceans. 89 On the basis of these assumptions, the bottom surface area s u i t a b l e as a l o b s t e r habitat i n F a t t y Basin amounts to about 7% (38,000 m 2) of the t o t a l area, with an a d d i t i o n a l 13% (70,000 m 2) a v a i l a b l e to the search f o r food. In Useless I n l e t , the f i g u r e s are 5% (135,000 m2) f o r the favorable l o b s t e r h a b i t a t , and 11% (300,000 m ) f o r the a d d i t i o n a l areas. BIBLIOGRAPHY B l a t t , H.; 1967: "Provenance Determinations and Recycling of Sediments" J . Sed. Petr. , v. 37, pp. 1031-1044. Bremner, J.M.; 1970: "The Geology of Wreck Bay, Vancouver I s l a n d " MSc-Thesis, U n i v e r s i t y of B r i t i s h Columbia. B r i n d l e y , G.W.; 1961: "The X-Ray I d e n t i f i c a t i o n and C r y s t a l Structures of Clay Minerals" Mineralog. Soc. Great B r i t a i n Carter, L.; 1970: " S u r f i c i a l sediments i n Barkley Sound, Vancouver Is l a n d , B r i t i s h Columbia" PhD-Thesis, U n i v e r s i t y of B r i t i s h Columbia. Clapp, C.H.; 1912: "Southern Vancouver Island" Geological Survey of Canada, Mem. 13. Cockbain, A.E.-, I963: " D i s t r i b u t i o n of Foraminifera i n Juan de Fuca and Georgia S t r a i t s , B r i t i s h Columbia" Contr. Cushman Found, f o r Foram. Research, v. XIV, Part 2. Cushman, J.A.; 1947: "Foraminifera From The Coast of Washington" Cushman Lab. f o r Foram. Research, Spec. Publ. No. 21 " ; 1959: "Foraminifera - Their C l a s s i f i c a t i o n and Economic Use" Harvard U n i v e r s i t y Press, Cambridge, Mass. Curray, J.R.; I965: "The Quaternary H i s t o r y , Continental Shelves of the United States", i n "The Quaternary of the United State Princeton U n i v e r s i t y Press, pp. 723 - 735. Deer, W.A., Howie, R.A., Zussman, J . ; 1967: "An Introduction to the Rock Forming Minerals" Wiley, New York, 528 p. Mathews, W.H., F y l e s , J.G. , Nasmith, H.W.; 1970: " P o s t g l a c i a l C r u s t a l Movements i n Southwestern B r i t i s h Columhia and Adjacent Washington State" Can. J . Earth Science, v. 7, pp. 690 - 702. Muller, J.E., Carson, D.J.T.; 1969: "Geology and Mineral Deposits of Al b e r n i Map Area, B r i t i s h Columbia" Geological Survey of Canada, Paper 68 - 50. Peacock, M.H.; 1935: "Fjord-Land of B r i t i s h Columbia" Geol. Sock. Am. B u l l . , v. U6, pp.633 - 696. P e t t i j o h n , F.J.; 1957: "Sedimentary Rocks" Harper, New York, 718 p. P i e r c e , J.W., S i e g e l , F.R.; 1969: " Q u a n t i f i c a t i o n i n Clay Mineral Studies of Sediments and Sedimentary Rocks" J . Sed. Petr., v. 39, PP- I 8 7 - 193. Prokopovich, N.P.; 1969: "Deposition of C l a s t i c Sediments by Clams" J . Sed. Pet r . , v. 39, pp. 891 - 901. Quayle, D.B.; I960: "The I n t e r t i d a l Bivalves of B r i t i s h Columbia" Handbook No. 17, B.C. Prov. Museum, lOh p. Seki, H.; 1968: "Relation Between Production and M i n e r a l i z a t i o n of Organic Matter i n Aburatsubo I n l e t , Japan" J . F i s h . Res. Bd. Canada, v. 25, pp. 625 - 637-Shepard, F.P.; 1963: "Submarine Geology" Harper & Row, N.Y., 557 p. Stephens, K. , Sheldon, R.W., Parsons, T.R.; 1967: "Seasonal V a r i a t i o n s i n the A v a i l a b i l i t y of Food f o r Benthos i n a Coastal Environment" Ecology, v. hQ, No. 5. Sutherland-Brown, A.; I966: "Tectonic History o f the Insular Belt of B r i t i s h Columbia", i n "Tectonic History and Mineral Deposits of the Western C o r d i l l e r a " Canadian Inst. Mining and Metallurgy, pp. 83 - 100. Degens, E.T.; ±965: "Geochemistry of Sediments" P r e n t i c e - H a l l , N.J., 342 p. Douglas, R.J.W. ( e d i t . ) ; 1970: "Geology and Economic Minerals of Canada" Geological Survey of Canada, Economic Geology Report No. 1. Folk, R.L.; 1965: "Petrology of Sedimentary Rocks" Hemphill's, Texas, 159 P-F y l e s , J.G.; 1963: " S u r f i c i a l Geology of Horne Lake and P a r k s v i l l e Map Area. Vancouver Island" Geological Survey of Canada, Mem. 318 G r i f f i t h , L.M.; 1967: "The I n t e r t i d a l Univalves of B.C." Handbook No. 26, B.C. Prov. Museum, 101 p. Grim, R.E. ; 1968: "Clay Mineralogy" McGraw - H i l l , Toronto, 596 p. Herlinveaux, R. H.; 1966: "Oceanographic Phase of the Fatty Basin Study for a Lobster Transplant" Manuscript Report S e r i e s , No. 228, F i s h e r i e s Research Board of Canada. Holland, S.S.; I96U: "Land forms of B.C. - A Physiographic Ou t l i n e " B.C. Dept. Mines Petr. Res., B u l l . No. 48. Keen, M.A.; 1963: "Marine Molluscan Genera of Western North America" Stanford U n i v e r s i t y Press, C a l i f . K o l d i j k , W.S.; 1968: "On Environment-Sensitive Grain-Size Parameters" Sedimentology, v. 10, pp. 57-69-" ; 1968: "Bottom Sediments of the Ria de Arosa" PhD-Thesis at R i j k s - U n i v e r s i t y , Leiden, Netherland. Krumbein, W.C., PettiJohn, F.J.; 1938: "Manual of Sedimentary Petrography" Appleton-Century-Crofts , N.Y. , 549 p. 93 9h Appendix 1 - Laboratory Methods Methods used f o r ana l y s i s of the sediment and rock samples are b r i e f l y o u t l i n e d . D e t a i l s of the procedures followed are discussed i n standard textbooks, a l l l i s t e d i n the bibliography. ( i ) Size a n a l y s i s 125 sediment samples from Fatty Basin, Useless I n l e t , and Rainy Bay were analysed, using s i e v i n g and hydrometer methods f o r the coarse and the f i n e f r a c t i o n s , r e s p e c t i v e l y ( f i n e f r a c t i o n s = s i l t and c l a y ) . Sieve i n t e r v a l s of 1/2 phi were considered s u f f i c i e n t f o r most samples, except when the bulk of a sediment appeared to be concentrated i n a few s i z e f r a c t i o n s ; l A phi i n t e r v a l s were then used f o r those f r a c t i o n s . Wet-sieving was done on muddy sediments, i n order to separate most of the f i n e f r a c t i o n s from the coarse m a t e r i a l before d r y - s i e v i n g . S i l t s and clays were analysed by standard hydrometer methods. Previous to a n a l y s i s , a l l samples were t r e a t e d with hydrogen peroxide f o r removal of organic carbon, because i n water, the untreated muds always coagulated into t i n y " b a l l s " , despite the use of dispersant. Size analysis of those muds, t h e r e f o r e , would give r e s u l t s t o t a l l y i r r e l e v a n t to the true s i z e d i s t r i b u t i o n of suspended p a r t i c l e s at the time of deposition. Errors induced by omission of the organic m a t e r i a l are therefore considered l e s s severe than those inherent i n an analysis of untreated, o r g a n i c - r i c h muds. Results from t h e - s i z e analysis were processed by an IBM 360/67 computer, which c a l c u l a t e d s t a t i s t i c a l parameter values and also drew cumulative and frequency curves. 95 ( i i ) Heavy minerals The f i n e sand f r a c t i o n s between 2.5 and k phi of 30 samples were analysed f o r t h e i r heavy mineral content, using bromoform ( s p e c i f i c g r a v i t y = 2.89) as separating agent. Thin sections f o r heavy and l i g h t grains were prepared, and r e l a t i v e percentages of i n d i v i d u a l minerals were determined by grain-count methods. ( i i i ) Clay minerals Clays were analysed using a P h i l l i p s d i f f ractometer with N i -f i l t e r e d r a d i a t i o n . Preparation of the samples involved s e v e r a l steps, i n c l u d i n g - removal of CaCO^ with hydrochloric a c i d , - removal of organic carbon with hydrogen peroxide, - removal of i r o n with sodium d i t h i o n i t e , - Mg- and K-saturation of some of the samples. A d d i t i o n a l treatment of c l a y s , i n order to determine i n d i v i d u a l mineral groups, included - heating to 200° C and 5^0° C, to recognize the presence of v e r m i c u l i t e and k a o l i n i t e , - exposure t o ethylene g l y c o l fumes , to expand smectite and v e r m i c u l i t e l a t t i c e s , and - washing i n warm hydrochloric a c i d , to remove c h l o r i t e minerals. ( i v ) Organic carbon Mud .samples selected f o r organic carbon analysis were f i r s t t r e a t e d with hydrochloric a c i d , i n order to remove a l l carbonates. Due 96 to prolonged equipment-breakdown i n the laboratory, the carbon analyis was done by Can Test Ltd. i n Vancouver, where the combustion furnace method was used. (v) Rocks Rock samples from a l l major u n i t s exposed i n the area under con-s i d e r a t i o n were studied i n pol i s h e d and t h i n sections. Grain count methods were used to determine r e l a t i v e percentages of the main constituent minerals. ( v i ) Shell-bearing Fauna Sh e l l s were c o l l e c t e d and i d e n t i f i e d , using reference volumes l i s t e d i n the bibliography. Foraminifera t e s t s were separated from the sediments with carbon t e t r a c h l o r i t e and i d e n t i f i e d by Dr. B. Cameron of the Geological Survey of Canada. Appendix 2 Tables 98 Table 9 : Dates of exchange of sampling bowls (positions shown on Map No. l ) , dry weight of samples (a f t e r removal of CaCO ), and rates of sedimentation as c a l c u l a t e d . 3 Samples bowls were f i r s t put i n t o p o s i t i o n on J u l y 15, 1969. Date P o s i t i o n Dry Weight Rate of Sed. (g) (g/m2/day) Aug. 15, '69 1 1.890 lU .60 2 1.000 7.65 3 1.095 8.43 1+ .170 1.33 Sept. 16, '69 1 l o s t 2 .330 2.1+6 3 .663 1+.91+ k .190 1.1+3 Oct. 15, '69 1 .052 .1+3 2 .121 1.00 3 .091 .74 h .320 2.63 Nov. 15, '69 1 .107 .81 2 l o s t -3 .311 2.39 k .209 1.60 December samples not c o l l e c t e d Jan. T, '69 1 1+.1+35 (?) 2 .150 .69 3 .512 2.36 k .269 1.21+ Feb. 13, '69 1 .252 1.62 . 2 .198 1.29 3 18.1+10 (?) -1+ l o s t — 9 9 Table 9 Continued Date P o s i t i o n Dry Weight Rate of Sed. (g) (g/m /day) Mar. 2 U , ' 6 9 1 . 1 * 3 8 2 . 7 5 2 . 1 7 1 1 . 0 8 3 . 2 8 6 1 . 7 9 1* 6.502 (?) -Apr. 1 5 , ' 6 9 1 . 0 1 3 . 1 1 * 2 . 1 2 2 1 . 1 * 3 3 . 0 9 1 . 9 8 1* . 1 9 1 2 . 0 8 May 20, ' 6 9 1 .103 . 6 9 2 1 7 . 1 * 0 1 * ( ? ) -3 .11*1* . 9 8 1+ l o s t — June 1 7 , ' 6 9 1 2 . 5 6 2 2 1 . 8 0 2 l o s t -3 l o s t -1* l o s t — J u l y 1 8 , ' 7 0 1 . 5 7 2 1*.1*2 2 1 . 0 6 U 8 . 1 9 3 . 1 1 8 . 9 1 . 0 3 8 . 2 9 Note: (?) r e f e r s to abnormally large samples, which probably were contaminated with bottom mud during r e t r i e v a l . 1 0 0 Table 10: S t a t i s t i c a l parameters and percentages of g r a v e l , sand, and mud. The samples are arranged i n groups defined from cumulative curves (see chapter "Types of Sediments") Sample Graph. Inc. Gr. Inc. Gr. Graph. Gravel Sand Mud No. Mean Std. Dev. Skewn. Kurt. (phi) (phi) (*) {%) Group 2 - 2 . 9 4 7 1.116 . 3 6 7 1 .501+ 91 8 1 No. 1 2 6 - 2 . 3 9 5 1.1+38 .1+08 • 977 96 1+ -1+1+ - 2.990 .711 . 1 2 7 . 8 7 1 9 8 2 -58 - 2.8U0 I.6I+9 . 6 3 9 . 9 6 8 99 1 -81* - 3.192 2 . 1 5 7 • 770 1 . 0 2 5 81 17 2 1 0 0 - 2 . 6 0 6 1.086 . 2 3 0 . 9 1 2 90 1 0 -Ilk - 2.658 1.321* .51+6 • 995 86 Ik -119 - 2 . 2 1 2 1.504 .1+52 .939 77 22 1 Group 3 - 1.150 1.828 . 3 8 7 1 . 2 9 0 66 3 1 3 No. 2 8 - 1 . 0 9 5 1 . 3 5 9 . 1 3 1 1.1+66 57 1+2 1 1 7 - 1 . 3 0 8 1.635 .304 1 . 0 5 3 5 9 3 8 3 2 0 .1+71 1.21+1+ . 0 2 6 . 9 2 8 1 2 87 1 2 3 - . 8 3 8 1.31+1+ .331 1 . 3 9 6 54 1+1+ 2 2k - 1.1+29 1.365 . 1 9 7 1 . 2 3 1 70 30 -2 5 - . 9 1 3 1.532 . 2 1 6 1 . 2 6 1 5 8 1+1 1 39 - . 6 3 3 1.769 . 2 2 1 1 . 0 7 2 1+5 5 2 3 U5 .1+09 1.521 . 0 8 6 1.11+7 1 5 8 2 3 5 1 . 0 3 8 I . 89 I + . 0 6 3 1 . 1 0 1 28 6 9 3 6 l - 1.812 1 . 4 5 3 .363 1 . 7 3 5 79 18 3 6 2 - .1+52 1.1+86 . 2 3 9 l . l i l+ 3 9 5 9 2 6 5 - .01+1 I . 6 9 2 .11+3 . 9 1 6 3 2 6 5 3 76 - . 7 7 4 2.024 .11+1 1.135 1+8 1+8 k 83 - . 3 9 6 1 . 7 6 3 . 2 1 5 1 . 0 5 8 1+0 5 7 3 8 9 - . 8 9 5 1 . 8 5 6 . 1 8 5 . 9 0 2 51 1+7 2 9 2 - .905 1.81+7 .342 1 . 1 2 9 5 3 1+6 1 103 - . 9 7 0 1 . 9 4 7 .333 . 7 1 0 54 1+5 1 104 - .920 1 . 6 1 9 . 3 5 9 1.1+1+8 5 6 1+3 1 101 Table 10 Continued Sample No. Graph. Mean Inc. Gr. Std. Dev. Inc. Gr. Skewn. Graph. Kurt. Gravel Sand Mud Group No. 3 Group No. h (phi) (phi) (%) (% 112 - .71*+ 1.1*5U .300 1.239 1*6 53 l 117 - .367 1.727 .113 1.1+55 33 66 l 122 - .383 1.612 .328 .933 1+3 55 2 12 1* - 1.275 1.709 .281 1.050 62 37 1 Ik 2.1+02 1.21*3 - .012 1.2l*3 _ 91 9 19 1.273 1.160 .030 l.l+ll* 5 92 3 86 2.1+81 • 775 - .265 1.203 1 98 1 90 2.539 .890 - .21*0 .901 1+ 91+ 2 96 1.718 1.535 - .292 .81*9 5 93 2 98 2.679 1.319 .198 1.81*1* - 91 9 101 1.715 1.570 - .187 .863 3 96 1 105 1.776 1.260 - .179. .923 3 95 2 107 1.898 .982 - .179 .963 - 99 1 111 1.565 1.1*32 - .198 .937 6 93 1 113 1.72U • 992 - .11*8 .981* 1 98 1 115 2.010 .911+ - .21*2 .958 1 99 -116 1.9^1 1.160 - .1*09 1.177 1* 95 1 121 1.1*65 .991+ - .050 .901* 1 98 1 1 5-021* 3.132 .291* 1.903 2 27 71 6 5.738 3.ll*3 .392 1.063 1 15 81* 7 5.11+5 1.1*1*1* .1*1*7 1.1*35 - 12 88 10 6.521 2.1*55 .321 .857 - 2 98 l l 5.782 1.569 .271 .708 - - 100 18 5.780 2.037 .1*06 .931 - 1 99 19 6.950 2.680 .311 .81*7 - - 100 27 1*.981* 3.010 .287 • 953 2 6 92 31 5.139 1.739 .315 .868 - I* 96 102 Table 10 Continued Sample Graph. No. Mean (phi) 3k 5 - 9 8 1 36 5.074 37 6.063 41 5.378 47 5-842 49 5.739 71 5.061 72 U.808 75 6.037 82 6.705 85 5.686 91 6.342 93 U.982 123 5.671 k - .103 12 - .033 21 - .026 22 - 1.638 28 .035 29 - 1.433 32 - I.563 38 .063 k2 .205 50 - 1.593 52 - 1.120 53 - 1.038 54 - 1.686 56 - 1.579 66 - .277 Group No. 5 Inc. Gr. Inc. Gr. Graph. Gravel Sand Mud Std. Dev. Skewn. Kurt. (phi) (*) 2.074 .299 • 795 - 2 98 3.148 .287 1.923 - 15 85 3.349 .661 2.147 - 12 88 1.935 .289 .713 - k 96 3.245 .103 1.125 1 2k 75 2.683 .326 .853 - 3 97 2.489 .427 1.383 2 11 87 1.239 .647 1.983 - 17 83 1.870 .294 1.864 - 9 91 2.959 .512 .985 - 5 95 3.141 .439 1.151 - 29 71 3.424 • 759 2.139 - Ik 86 3.145 .268 I.836 - l l 89 2.096 .305 1.695 1 8 91 1.900 .036 .691 35 62 3 1.862 .122 .967 32 66 2 I.876 .124 .959 34 63 3 2.198 .383 .698 63 36 1 1.712 - .230 .919 26 73 1 2.127 .419 .912 6k 33 3 2.493 .428 .782 63 34 3 2.257 .313 .919 37 57 6 2.663 - .008 .945 30 63 7 2.282 - .034 .633 54 45 1 2.313 .140 .811 62 35 3 2.174 .175 .714 53 46 1 I.960 .233 • 903 67 32 1 2.1U8 .303 .951 65 33 2 2.111 .079 .944 45 52 3 103 Table 10 Continued Sample Graph. No. Mean (phi) 68 - 1.615 69 - .37*+ 11 - 1.992 118 - 1.706 125 .211+ Group 5 2.385 No. 6 13 1.888 15 .696 35 2.038 1+3 2.275 55 2.002 57 .805 60 I.76U 78 1.595 95 1.100 97 1.880 99 2.687 106 .221+ 108 .593 109 2.509 120 I.0U3 Group 33 1+.31+0 No. 7 87 3.936 88 1+.836 102 5-051 Inc. Gr. Std. Dev. (phi) Inc. Gr. Skewn. Graph. Kurt. Gravel (%) Sand Mud (*) 2.06l .1+18 .929 61 31 2 2.1+18 - .338 .751 32 65 3 2.201+ .1+97 .681 69 30 1 1.627 - .065 .716 59 1+0 1 1.887 .036 1.023 2.6 70 1+ 1.883 .207 .898 1 71+ 25 1.61+8 .087 1.121+ 3 86 11 1.502 .012 .721 19 80 1 1.603 .277 1.583 2 79 19 2.312 .1+33 2.155 1 82 17 2.879 .21+1+ I.7I+8 8 73 19 2.721 .625 1.611 22 63 16 2.105 .01+7 1.093 3 89 8 1.867 .263 1.718 6 82 12 1.855 - .211+ 1.158 11+ 82 1+ 2.228 .055 1.189 8 78 ll+ 1.652 - .111 1.070 2 77 21 1.61+0 .01+8 .91+6 23 75 2 1.576 - .018 .999 15 81+ 1 1.830 .027 1.931 2 85 13 1.1+39 .081+ .926 7 90 3 3.738 .31+1 1.192 7 1+5 1+8 I+.56U .291 1.197 12 1+3 1+5 2.89I+ .1+36 1.178 - 1+7 53 2.620 .1+39 .906 1 36 63 104 Table 10 Continued Sample Graph. Inc. Gr. No. Mean Std. Dev. (phi) (phi) Group 9 3.628 4.739 No. 8 30 .833 4.207 kG 2.972 5.242 48 3.710 4.838 59 2.308 4.839 63 2.873 .397 6k 1.822 4.670 67 .232 4.060 70 - .847 3.063 73 1.826 5.271 74 4.833 4.717 80 4.714 4.668 94 1.005 4.131 Inc. Gr. Graph. Gravel Sand Mud Skewn. Kurt. (%) (*) .341 1.043 18 k6 36 .352 1.273 41 3k 25 .374 .813 27 33 40 .319 1.063 21 39 ko .573 1.033 2k 37 39 .377 .984 19 43 38 .318 .928 32 39 29 .622 1.109 53 26 21 .162 • 935 50 40 10 .358 .699 kk 17 39 .518 .993 14 3k 52 .107 1.359 12 28 60 Ml 1.193 35 38 27 FATTY BASIN Sample Locations +00 = Number and location of sample analysed in detail ® = Location of sample not analysed in detail 1./= Low-tide l ir ie ® = Location of Sedimentation bowls .84 UUUIJJ-U USELESS INLET RAINY BAY +w= Number and location of sample analysed in detail ® = Location of sample not analysed in detail 0 .500 1000 1500 2000 2500 3000 asnn f e e t 0 100 J00 m 500 m e t e r s 700 900 YM ET RY 200 400 Feet 100 Meters Contour Interval = 6feet — High-tide line — Low-tide I in* U S E L E S S I N L E T B A T H Y M E T R Y Contour interval = 2 fathoms FATTY BASIN SCALE = 1 .2000 DISTRIBUTION OF SEDIMENTS LEGEND 1 2 3 5 6 [ 71 8 9 1 0 ^ 12 H 13 wezz 15 [ZD Bedrock Boulders, mostly large, angular Angular, coarse gravel; few shell-fragments Sand, medium to fine ; little gravel Sand, mostly coarse; some pebbles and shells Sand,coarse; abundant pebbles Gravel and pebbles, rounded; shells very abundant Sand-shell debris mixture, coarse, muddy Gravel (angular)-shell mixture, very coarse, muddy Shell-debris, medium, muddy; abundant gravel Shell-debris, fine to very fine, muddy Shell-debris, coarse to very coarse Mud,gray Mud, greenish, abundant small shell fragments Mud, green, very high organics content = Low-tide line 1^= High-tide line NOTE : Colours apply to sediments below low-tide level only U S E L E S S I N L E T TRIBUTION OF S E D I M E N T S LEGEND Bedrock Boulders, mostly large, angular •• Angular, coarse gravel; few shell-fragments 1 1 Sand, medium to fine; little gravel C D Sand, mostly coarse; some pebbles and shells 1 I Sand, coarse; abundant pebbles •1 Gravel and pebbles, rounded; shells very abundant 1 1 Sand - shell mixture, coarse, muddy WM Gravel (angular ) - shell mixture, very coarse, muddy V7A Shell • debris, medium , muddy; abundant gravel I H Shell - debris, fine to very fine, muddy Shell-debris, coarse Ea Mud, gray E S S Mud, greenish, abundant small shell fragments 1 1 Mud, green, very high organics content 's \ Low-tide line High-tide line NOTE: Colours apply to sediments below low tide levol — ZQO _ ___400 _ METERS 8QO 1600 FEET 

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