@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Science, Faculty of"@en, "Earth, Ocean and Atmospheric Sciences, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Rahmani, Riyadh Abdul-Rahim"@en ; dcterms:issued "2011-07-15T21:37:15Z"@en, "1968"@en ; vivo:relatedDegree "Master of Science - MSc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """The Upper Cretaceous (Campanian) Cedar District Formation of the Gulf Islands and adjacent areas is composed of shale and sandstone, which are present as thick sequences of shale, which may or may not be fossiliferous, and as alternating rhythmic sandstone-shale sequences of the flysch-type. Presence of graded bedding, ripple and convolute laminations, and sole marks in the latter suggest a turbidity current origin. The internal structures of the individual turbidite units correspond largely to the C-E divisions of Bouma (1962) and other authors, and indicate that their deposition took place largely within the lower flow regime. Convolute lamination in the sandstones was formed by oversteepening and deformation of pre-existing ripple lamination and by the deformation of pre-existing plane-parallel lamination by the drag of the overpassing currents. Flute and groove casts and frondescent marks were only found in beds thicker than a foot and a half. Calcareous concretions, most abundant in the shales and occasionally phosphatic, are crossed by organic borings and burrows which are filled with sediments of the surrounding beds. Host rocks of the calcareous concretions tend to thicken around them. The concretions show deformation when present in beds involved in soft-sediment deformation. All these observations suggest their formation in the early stage of diagenesis, probably shortly after, burial. Sandstones of the Cedar District Formation show a gradation from arenites that lack matrix and have a cal-cite cement, to wackes rich in fine-grained matrix. The majority of the wackes and the arenites are feldspathic and arkosic, using the classification of Gilbert (1954). Their composition indicates that the major source was acidic to intermediate igneous and/or low to medium grade metamorphic rock , sedimentary and volcanic rocks were a secondary source. The major source area was possibly a region of high relief that had undergone rapid uplift and erosion, and experienced mainly mechanical weathering. Paleocurrents and lithologic lateral variation indicate that the major source area for the coarse elastics was situated to the east and southeast of the study area. The pre-Jurassic low grade metamorphic rocks of the Cascade Mountains to the east, and the pre-Carboniferous- crystalline rocks of the San Juan Islands to the southeast served as possible source areas for the coarse elastics. Deposition of shaley, fossilif erous parts, of the formation in the southeastern part, of the study area, took place in littoral to upper neritic depths. Turbidite (flysch-type) sequences were deposited in deeper water, below the wave base. The unfossiliferous shale of the central and northern parts of the study area was deposited either at about the same depths as the turbidites, or in deeper water, since thin, delicate, horizontal and-cross laminations are preserved in these rocks. Paleontologic evidence suggests that deposition took place in a somewhat restricted basin having a narrow connection with the open ocean to the west. Paleontologic and mineralogic data suggest that the bottom conditions of the central and northern parts of the basin of deposition were stagnant and reducing. Facies relationships suggest that the basin of deposition had its longest dimension trending SE-NW. Its eastern, southeastern, and southern boundaries were situated between the mainland of British Columbia-Washington and the Gulf-San Juan Islands. Its northern and northwestern boundaries were possibly near the city of Nanaimo and Gabriola Island. To the west, it was connected at least partially to the open ocean. In the southeastern part of the study area, alternation of thick, fossiliferous shale sequences, and sequences which are predominantly turbidites suggests fluctuations in the depth of the basin floor, either due to changes in sea level or to tectonic movements."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/35989?expand=metadata"@en ; skos:note "SEDIMENTOLOGY AND PETROLOGY OF THE CEDAR DISTRICT FORMATION, LATE CRETACEOUS, SOUTHWESTERN BRITISH COLUMBIA by RIYADH ABDUL-RAHIM RAHMANI B.Sc.j U n i v e r s i t y o f Baghdad, 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department o f Geology We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA JULY, 1968 In presenting this thesis in pa r t ia l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i sh Columbia, I agree that the Library sha l l make i t f ree ly ava i lab le for reference and Study. I further agree that permission for extensive copying of this thesis for scholar ly purposes may be granted by the Head of my Department or by hils representat ives. It is understood that copying or publ icat ion of th is thesis for f inanc ia l gain shal l not be allowed without my wri t ten permission. Department of The Univers i ty of B r i t i sh Columbia Vancouver 8, Canada ( i ) ABSTRACT The Upper C r e t a c e o u s (Campanian) Cedar D i s t r i c t F o r -m a t i o n o f the G u l f I s l a n d s and a d j a c e n t a r e a s i s composed o f s h a l e and sandstone, w h i c h a r e p r e s e n t as t h i c k se-quences o f s h a l e , w h i c h may o r may not be f o s s i l i f e r o u s , and as a l t e r n a t i n g r h y t h m i c s a n d s t o n e - s h a l e sequences o f t h e f l y s c h - t y p e . Presence o f graded b e d d i n g , r i p p l e and c o n v o l u t e l a m i n a t i o n s , and s o l e marks i n t h e l a t t e r sug-g e s t a t u r b i d i t y c u r r e n t o r i g i n . The i n t e r n a l s t r u c t u r e s o f t h e i n d i v i d u a l t u r b i d i t e u n i t s c o r r e s p o n d l a r g e l y t o the C-E d i v i s i o n s o f Bouma (1962) and o t h e r a u t h o r s , and i n d i c a t e t h a t t h e i r d e p o s i t i o n t o o k p l a c e l a r g e l y w i t h i n the l o w e r f l o w regime. C o n v o l u t e l a m i n a t i o n i n the sandstones was formed by o v e r s t e e p e n i n g and d e f o r m a t i o n o f p r e - e x i s t i n g r i p p l e l a m i n a t i o n and by t h e d e f o r m a t i o n of p r e - e x i s t i n g p l a n e -p a r a l l e l l a m i n a t i o n by t h e d r a g o f the o v e r p a s s i n g c u r -r e n t s . F l u t e and groove c a s t s and f r o n d e s c e n t marks were o n l y found i n beds t h i c k e r t h a n a f o o t and a h a l f . C a l c a r e o u s c o n c r e t i o n s , most abundant i n the s h a l e s and o c c a s i o n a l l y p h o s p h a t i c , a r e c r o s s e d by o r g a n i c b o r i n g s and burrows w h i c h are f i l l e d w i t h 1 sediments o f t h e s u r -r o u n d i n g beds. Host r o c k s o f the c a l c a r e o u s c o n c r e t i o n s t e n d t o t h i c k e n around them. The c o n c r e t i o n s show ( i i ) d e f o r m a t i o n when p r e s e n t i n beds i n v o l v e d i n s o f t - s e d i -ment d e f o r m a t i o n . A l l t h e s e o b s e r v a t i o n s s u g g e s t t h e i r f o r m a t i o n i n t h e e a r l y s tage o f d i a g e n e s i s , p r o b a b l y s h o r t l y a f t e r , b u r i a l . Sandstones o f the Cedar D i s t r i c t F o r m a t i o n show a g r a d a t i o n from a r e n i t e s t h a t l a c k m a t r i x and have a c a l -c i t e cement, t o wackes r i c h i n f i n e - g r a i n e d m a t r i x . The m a j o r i t y o f the wackes and t h e a r e n i t e s a r e f e l d s p a t h i c and a r k o s i c , u s i n g the c l a s s i f i c a t i o n o f G i l b e r t (1954). T h e i r c o m p o s i t i o n i n d i c a t e s t h a t tfye. major so u r c e was a c i d i c t o i n t e r m e d i a t e igneous and/or l o w t o medium grade metamorphic r o c k , s e d i m e n t a r y and v o l c a n i c r o c k s were a s e c o n d a r y s o u r c e . The major so u r c e a r e a was p o s s i b l y a r e g i o n of h i g h r e l i e f t h a t had undergone r a p i d u p l i f t and erosion-, and e x p e r i e n c e d m a i n l y m e c h a n i c a l \"weathering. Paleoc.urrehts. and l i t h o l o g i c 1 l a t e r a l v a r i a t i o n i n d i c a t e t h a t the major so u r c e a r e a f o r the c o a r s e e l a s t i c s was s i t u a t e d t o t h e e a s t and 'southeast o f the s t u d y a r e a v The p r e - J u r a s s i c low grade metamorphic. r o c k s o f - the. Cascade Mountains, to., the east.-, and t h e p r e - C a r b o n i f e r o u s - c r y s t a l -l i n e r o c k s of. t h e San Juan I s l a n d s , to. the s o u t h e a s t s e r v e d as p o s s i b l e source areas, f o r t h e c o a r s e e l a s t i c s ' . D e p o s i t i o n o f s h a l e y , f o s s i l i f erous p a r t s , o f t h e f o r m a t i o n i n the s o u t h e a s t e r n p a r t , of- t h e st u d y a r e a , ( i i i ) t o o k p l a c e i n l i t t o r a l t o upper n e r i t i c d e p t h s . T u r b i d i t e ( f l y s c h - t y p e ) sequences were d e p o s i t e d i n deeper w a t e r , below the wave base. The u n f o s s i l i f e r o u s s h a l e o f the c e n t r a l and n o r t h e r n p a r t s o f t h e s t u d y a r e a was d e p o s i -t e d e i t h e r a t about the same depths as the t u r b i d i t e s , o r i n deeper w a t e r , s i n c e t h i n , d e l i c a t e , h o r i z o n t a l a n d -c r o s s l a m i n a t i o n s a r e p r e s e r v e d i n t h e s e r o c k s . P a l e o n t o -l o g i c e v i d e n c e s u g g e s t s t h a t d e p o s i t i o n t o o k p l a c e i n a somewhat r e s t r i c t e d b a s i n h a v i n g a narrow c o n n e c t i o n w i t h t h e open ocean t o t h e west. P a l e o n t o l o g i c and minera-l o g i c d a t a suggest t h a t t h e bottom c o n d i t i o n s o f t h e c e n t r a l and n o r t h e r n p a r t s o f t h e b a s i n o f d e p o s i t i o n were s t a g n a n t and r e d u c i n g . Fac'ies r e l a t i o n s h i p s suggest t h a t t h e b a s i n o f d e p o s i t i o n had i t s l o n g e s t d i m e n s i o n t r e n d i n g SE-NW. I t s e a s t e r n , s o u t h e a s t e r n , and s o u t h e r n b o u n d a r i e s were s i t u -a t e d between the m a i n l a n d o f B r i t i s h Columbia-Washington and t h e G u l f - S a n Juan I s l a n d s . I t s n o r t h e r n and n o r t h -w e s t e r n b o u n d a r i e s were p o s s i b l y near the c i t y o f Nanaimo and G a b r i o l a I s l a n d . To t h e west, i t was connected a t l e a s t p a r t i a l l y t o the open ocean. I n t h e s o u t h e a s t e r n p a r t o f the s t u d y a r e a , a l t e r n a t i o n o f t h i c k , f o s s i l i f e r o u s s h a l e sequences, and sequences w h i c h are p r e d o m i n a n t l y t u r b i d i t e s s u g g e s t s f l u c t u a t i o n s i n t h e depth of t h e b a s i n f l o o r , e i t h e r due to changes i n sea l e v e l o r t o t e c t o n i c movements. (v) Page 6. SEDIMENTARY STRUCTURES 62 A. I n t e r n a l S t r u c t u r e s w i t h i n T u r b i d i t e U n i t s 63 a. Graded D i v i s i o n ( A - d i v i s i o n ) 64 b. Lower D i v i s i o n o f P l a n e - P a r a l l e l L a m i n a t i o n ( B - d i v i s i o n ) 67 c. D i v i s i o n o f R i p p l e and C o n v o l u t e L a m i n a t i o n ( C - d i v i s i o n ) 6$ d. I n t e r t u r b i d i t e D i v i s i o n ( D E - d i v i s i o n ) 73 B. S o l e Marks 75 a. F l u t e C a s t s 77 b. F r o n d e s c e n t Marks 7# c. Groove C a s t s S O d. Bounce C a s t s S3 e. O r g a n i c B o r i n g s and Burrows $4 C. S o f t - S e d i m e n t D i s t u r b e d B edding 84 D. . Sandstone D i k e s and M i s c e l l a n e o u s F e a t u r e s 90 7. PETROGRAPHY OF THE SANDSTONE 96 A. Quartz 96 B. F e l d s p a r 9# C ,. Rock Fragments 99 D. M i c a 100 E. C h l o r i t e 100 F. P o l y c r y s t a l l i n e Q uartz 101 G. Ch e r t 101 H. Other M i n e r a l s 101 I . Unknown M i n e r a l s 103 J . Cement 103 K. M a t r i x 104 L. Sandstone C l a s s i f i c a t i o n 106 8. GRAIN SIZE DISTRIBUTION 108 9. DIRECTIONAL STRUCTURES AND PALEOCURRENTS 110 A. Methods 110 B. P r e s e n t a t i o n and I n t e r p r e t a t i o n o f Data 111 10. PALEOGEOGRAPHY 114 A. B a s i n Geometry 114 B. D i s p e r s a l 117 C. Provenance 119 D. Environment o f D e p o s i t i o n 121 (vi) P a g e 1 1 . SUMMARY AND CONCLUSIONS- 124 12. B I B L I O G R A P H Y 128 13. APPENDIX; 135 ( v i i ) ILLUSTRATIONS F i g u r e s Page 1 Index Map 2 2 S t r u c t u r e and d i s t r i b u t i o n o f t h e Nanaimo Group i n t h e G u l f I s l a n d s and V i c i n i t y 5 ' 3 I n t e r s e c t i n g j o i n t s i n s ands tone 10 4 I n t e r s e c t i n g j o i n t s i n s h a l e 10 5 V a r i a t i o n i n s p a c i n g o f j o i n t s 10 6 T u r b i d i t e u n i t and i t s d i v i s i o n s 15 7 Co lumnar s e c t i o n s o f t he Cedar D i s t r i c t F o r m a t i o n 19 8 P e b b l y mudstone o f S a t u r n a I s l a n d 31 9 Cong lomera t e o f S a t u r n a I s l a n d 3 1 10 C o n t a c t o f t h e Cedar D i s t r i c t F o r m a t i o n and t h e P r o t e c t i o n F o r m a t i o n , V e s u v i u s B a y , Salt S p r i n g I s l a n d 31 11 Sands tone beds a t t h e base o f DeCourcy F o r m a t i o n , V e s u v i u s B a y , S a l t S p r i n g I s l a n d 33 12 C o n t a c t between t h e DeCourcy F o r m a t i o n and the u n d e r l y i n g Cedar D i s t r i c t F o r m a t i o n , Dodd N a r r o w s , V a n c o u v e r I s l a n d 33 13 C o n c e n t r i c c o n c r e t i o n a r y w e a t h e r i n g i n t h e s h a l e o f t h e Ceda r D i s t r i c t F o r m a t i o n , B e d w e l l H a r b o u r , N o r t h Pender I s l a n d 33 14 Sands tone d i k e c u t t i n g s h a l e sequence 33 15 T y p i c a l t u r b i d i t e sequence o f i n t e r b e d d e d s h a l e and s ands tone beds 33 16 L o g a r i t h m i c p r o b a b i l i t y p l o t s o f t h i c k n e s s e s o f B , C , and DE d i v i s i o n s , V e s u v i u s B a y , S a l t S p r i n g I s l a n d . 36 ( v i i i ) F i g u r e s - Page 17 L o g a r i t h m i c ' P r o b a b i l i t y p l o t s o f t h i c k n e s s e s o f B , C, and DE d i v i s i o n s , V e s u v i u s Bay, S a l t S p r i n g I s l a n d 37 18 L o g r a i t h m i c p r o b a b i l i t y p l o t s o f t h i c k n e s s e s o f B - , C, and DE d i v i s i o n s , B e d w e l l Harbour s e c t i o n , North Pender I s l a n d . 38 19 K a o l i n i t e / I l l i t e r a t i o c o n t o u r map o f the s h a l e o f t h e Cedar D i s t r i c t F o r m a t i o n 41 20 S h a l e y p a r t o f t h e V e s u v i u s Bay s e c t i o n 43 21 T u r b i d i t e sequence o f h i g h sandstone p e r c e n -tage 43 22 A l t e r n a t i n g sandstone beds w i t h t h i c k e r s h a l e beds. Low sandstone p e r c e n t a g e 43 23 T h i c k massive sandstone bed w i t h sandstone d i k e i n j e c t e d from below 43 24 • T u r b i d i t e sequence showing l a t e r a l u n i -. f o r m i t y i n bed t h i c k n e s s 43 25 T u r b i d i t e bed showing r e p e t i t i o n o f i t s d i v i s i o n s 43 26 T h i c k bed o f sandstone e n c l o s e s a deformed t h i n l y bedded sandstone c l a s t ( d e r i v e d from t h e u n d e r l y i n g beds?) 27 T h i c k bed o f sandstone e n c l o s e s a t h i n l y l a m i n a t e d c l a s t o f sandstone 50 28 P e b b l e s from t h e S a t u r n a I s l a n d p e b b l y mudstone 50 29 Specimen from t h e upper p a r t o f the S a t u r n a I s l a n d p e b b l y mudstone 50 30 N o r t h P e n d e r • I s l a n d b r e c c i a bed 50 31 Specimen from the N o r t h Fender I s l a n d b r e c c i a 50 ( i x ) F i g u r e s Page 32 C a l c a r e o u s c o n c r e t i o n e n c l o s e d by s a n d -s tone bed 53 33 C a l c a r e o u s c o n c r e t i o n embedded i n s h a l e 53 34 C a l c a r e o u s c o n c r e t i o n c r o s s e d by f i n e -g r a i n e d t h i n s ands tone bed 53 35 C a l c a r e o u s c o n c r e t i o n s f o r m i n g d i s c o n t i -nuous bed 53 36 C a l c a r e o u s c o n c r e t i o n s w i t h i t s l o n g e s t d i m e n s i o n c u t t i n g s h a l e l a m i n a t i o n 53 37 C a l c a r e o u s c o n c r e t i o n e n c l o s i n g a b i v a l v e d s h e l l 53 38 P h o t o m i c r o g r a p h o f a c a l c a r e o u s c o n c r e t i o n showing m i c r o f o s s i l s f i l l e d w i t h c a l c i t e and p y r i t e 55 39 P h o t o m i c r o g r a p h o f a c a l c a r e o u s c o n c r e t i o n s h o w i n g d e t r i t a l g r a i n s 55 40 P h o t o m i c r o g r a p h o f a c a l c a r e o u s c o n c r e t i o n s h o w i n g p l a n k t o n i c f o r a m i n i f e r (?) 55 41 P h o t o m i c r o g r a p h o f a c a l c a r e o u s c o n c r e t i o n s h o w i n g g e n e r a l v i e w o f p h o s p h a t i c p e l l e t s 55 42 P h o t o m i c r o g r a p h o f a c a l c a r e o u s c o n c r e t i o n s h o w i n g d e t a i l s o f a p h o s p h a t i c p e l l e t 55 43 E l e c t r o n m i c r o g r a p h s h o w i n g m i c r o t e x t u r e s o f a c a l c a r e o u s c o n c r e t i o n 57 44 E l e c t r o n m i c r o g r a p h showing m i c r o t e x t u r e s o f a c a l c a r e o u s e o n c r e t i o n 57 45 E l e c t r o n m i c r o g r a p h s h o w i n g m i c r o t e x t u r e s o f a c a l c a r e o u s c o n c r e t i o n 59 46 Deformed f a l c a r e o u s c o n c r e t i o n 59 47 T u r b i d i t e bed w i t h A - d i v i s i o n g rades g r a d u -a l l y upward i n t o E - d i v i s i o n 59 Figures Page 48 T u r b i d i t e bed w i t h A - d i v i s i o n having a sharp contact w i t h the o v e r l y i n g B - d i v i s i o n 65 49 Thick sandstone bed showing sole marks 65 50 Specimen of sandstone showing p l a n e - p a r a l l e l l a m i n a t i o n 65 51 Specimen of sandstone showing c l i m b i n g r i p p l e laminae 65 52 Asymmetrical branching r i p p l e marks on upper bedding plane of a sandstone bed 65 53 T u r b i d i t e bed showing two superimposed C - d i v i s i o n s 65 54 Specimen of sandstone showing grading of s t r u c t u r e s i n the B- and C - d i v i s i o n s 71 55 Specimen of sandstone showing convolute l a m i n a t i o n 71 56 Convolute l a m i n a t i o n on upper bedding plane of a sandstone bed 71 57 Organic borings i n shale 71 58 Organic borings on the s o l e of a sandstone bed 71 59 Loaded f l u t e cast and a groove cast on the so l e of a t h i c k sandstone bed 71 60 Frondescent marks p a r t i a l l y o b l i t e r a t e groove casts on the s o l e of a t h i c k sandstone bed 79 61 A close-up of the frondescent marks of f i g u r e 60 79 62 Scour marks on the base of a t h i c k sandstone bed 79 63 Loaded scour marks on the base of a t h i c k sandstone bed 79 ( x i ) F i g u r e s Page 64 Three g e n e r a t i o n s o f groove c a s t s on the s o l e o f a t h i c k sandstone bed 79 65 Groove c a s t s o f d i f f e r e n t shapes and s i z e s 82 66 Two g e n e r a t i o n s o f i n t e r s e c t i n g groove c a s t s w i t h superimposed r i d g e s 82 67 C l a s t s o f l a m i n a t e d sandstone embedded i n c o a r s e - g r a i n e d , t h i c k sandstone bed 82 68 Deformed c l a s t of l a m i n a t e d sandstone em-bedded i n c o a r s e - g r a i n e d , t h i c k sandstone bed 82 69 C l a s t o f l a m i n a t e d sandstone showing recumbent f o l d i n g , embedded i n a t h i c k bed o f sandstone 82 70 C l a s t s o f sandstone and s h a l e embedded i n t h i c k sandstone bed, t h e f o r m e r s t i l l c o n nected w i t h t h e u n d e r l y i n g u n d i s t u r b e d beds 82 71 C l a s t s o f l a m i n a t e d sandstone showing s l i g h t d e f o r m a t i o n , embedded i n a t h i c k bed of sandstone 85 72 C l a s t s o f f i n e - g r a i n e d sandstone and s h a l e showing a s y m m e y r i c a l f o l d i n g , e n c l o s e d i n a t h i c k bed o f sandstone 85 73 Recumbent f o l d i n g i n sandstone and s h a l e c l a s t s w h i c h are embedded i n a t h i c k bed o f sandstone. 85 74 Complex d e f o r m a t i o n i n sandstone c l a s t s em-bedded i n a t h i c k bed o f sandstone 85 75 Sandstone d i k e c u t t i n g t h r o u g h s h a l e #5 76 V e r y t h i n d i s c o n t i n u o u s sandstone d i k e cutting through ehale #5 77 Thi«k sandstone d i k e c u t t i n g t h r o u g h s h a l e 89 ( x i i ) Figures Page 78 Branching sandstone dike 89 79 Sandstone dike showing contorted lamination $9 80 Exotic block of sandstone embedded i n shale. Shale lamination bends below and terminating against the block #9 Si Exotic block of sandstone embedded in shale * Shale lamination bends around the block.. 89 &2 Deformed, laminated sandstone clasts enclosed in shale 89 #3 Photomicrograph of a sandstone showing the replacement of a quartz grain by the c-.lcite cement 97 84 Photomicrograph of a sandstone showing the replacement of quartz and feldspar .grains by the clay-size matrix 97 85 Photomicrograph of a sandstone showing-the replacement of a feldspar grain by the calcite cement 97 86 Photomicrograph of arkosic wacke showing a volcanic rock fragment 102 87 Photomicrograph of l i t h i c wacke showing shale rock fragments 102 88 Photomicrograph of feldspathic arenite showing siliceous cement 102 89 Classification triagnle of arenite sand-stones 105a 90 Classification triangle of wacke sandstones 105b 91 Photomicrograph of quartz arenite 107 92 Photomicrograph of feldspathic arenite 107 93 Photomicrograph of arkosic arenite 107 ( x i i i ) Figures Page 94 Photomicrograph of a r k o s i c wacke showing chert rock fragment 109a 95 Photomicrograph showing the replacement of grains by the surrounding c l a y - s i z e matrix 109a 96 Histograms of the g r a i n s i z e d i s t r i b u t i o n of the sandstones ,109b 97 T i l t compensator 109a 98 Paleoeurrents map 112 99 T r i a n g l e of Walker's t u r b i d i t e grouping 118 Tables Page 1 L i s t of the Nanaimo Group formations 8 2 Composition of the Cedar D i s t r i c t Formation sandstones 95 1. Ii PRODUCTION A> Purpose and Scope o f the Present Investigation. The area of study Is situated on the Gulf Islands an e part of the southeastern coast of Vancouver Island in the southwestern part of the Province of B r i t i s h Columbia in Canada (fig- 1). In a N'v-SK direction this area extends from just south of the ci t y of Nanaimo on Vancouver Island to the southern part of Saturna Island, a distance of about 43 miles. In a KE-ST:J direction, It extends from Mayne Island to the western part of Salt Spring Island, a distance of about 15 miles ( f i g . 2). Currently a study of the Upper Cretaceous Nanaimo Group i s being carried out by the Department of Geology in the University of B r i t i s h Columbia, supported by The Br i t i s h American O i l Company Ltd. The author's part of this project concerns one unit in the Nanaimo Group, the Cedar Dist r i c t Formation, and the objective of the present investigation was t o study the detailed petrological, sedimentological, and paleogeographica1 aspects of that particular formation. Because turbidites form an impor-tant part of the Cedar Dist r i c t Formation, a large part of this investigation w i l l be concerned with this type o f rock. . -2-3 B. Acknowledgements To Dr. Robert E. G a r r i s o n t h e a u t h o r w i s h e s t o e x p r e s s h i s deepest t h a n k s f o r c o n s i s t e n t l y e x c e l l e n t a d v i c e , con-s t r u c t i v e c r i t i c i s m , s t i m u l a t i o n , s u p p o r t , and c o n s o l a t i o n . Dr. G a r r i s o n ' s p o s i t i o n as a t h e s i s a d v i s o r c o u l d not have been f i l l e d more a d e q u a t e l y . Thanks a r e due t o Mr. M i c h a e l P u l l e n f o r h i s h e l p i n t r i p s among the i s l a n d s by boat and f o r d i s c u s s i o n s i n the f i e l d . To t h o s e i n h a b i t a n t s of t h e f i e l d a r e a , and p a r t i c u l a r l y t o Mr. and Mrs. Hindmarch, goes the a u t h o r ' s e x p r e s s g r a t i t u d e f o r generous h e l p and accomodation w h i l e c a r r y i n g out the f i e l d work on S a t u r n a I s l a n d . T h i s work was s u p p o r t e d by a g r a n t from The B r i t i s h American O i l Company Ltd., C. G e n e r a l Geology of the Nanaimo Group T h i s d i s c u s s i o n w i l l be a b r i e f account o f the g e o l o g y of t h e Nanaimo Group, drawn m a i n l y from p r e v i o u s s t u d i e s o f t h e s e r o c k s . a. S t r a t i g r a p h y The Nanaimo Group rang e s i n age f r o m the S a n t o n i a n t o M a e s t r i c h t i a n ( M u l l e r and J e l e t z k y , 1 9 6 7 ) . I t o u t c r o p s on the e a s t c o a s t o f Vancouver I s l a n d and the a s s o c i a t e d i s l a n d s t h a t f r i n g e t h e c o a s t . I t o c c u r s i n two main a r e a s 4 of outcrop, a smaller area around, the town of Suquash in the northeastern part of the island, and a large area ex-tending from Campbell River on the east coast of Vancouver Island in the north to the San Juan Islands in Washington State to the south. On the east, the outcrop areas are bounded by the waters of the Queen Charlotte and the Georgia Straits, on the west by the mountain ranges of mid-Vancouver Island. The Nanaimo - Comox and the Suquash basins, in which the Nanaimo Group has been deposited, were part of the Insular Belt of Br i t i s h Columbia (A. Sutherland Brown, 1966, f i g s . 6-2 to 6 - 1 0 ) . This area has been a site of tectonism and deposition from Late Paleozoic to the present time. During Late Paleozoic to Jurassic time, several suc-cessive eugeosynclinal basins developed. During Late Cre-taceous time, a downwarped or dpwnfaulted trough, the Georgia Seaway developed in the southeastern part of the Insular Belt and was the site of the Nanaimo Group deposi-tion (Sutherland Brown, 1966, p. 8 4 ) . The Nanaimo Group comprises a thick sequence of clas-t i c rocks consisting of conglomerates, shales, and some coal of mixed continental and marine origin (Usher, 1952). In general, the group i s thickest in the southeastern part of the Nanaimo basin, where i t reaches 10,000 feet and thins toward northwest edge of the basin to about 7,500 feet. 6 I n t h e Comox b a s i n t o t h e n o r t h w e s t o f t h e N a n a i m o b a s i n , t h e N a n a i m o G r o u p m e a s u r e s b e t w e e n 5,000 a n d 6,000 f e e t . J . E . M u l l e r a n d J e l e t z k y ( 1967, f i g . 1, p . 3 £ ) , d i v i d e d t h e N a n a i m o G r o u p r o c k s i n t o \" f o u r c o m p l e t e t r a n s -g r e s s i v e a n d r e g r e s s i v e c y c l e s o f s e d i m e n t a t i o n \" ; e a c h c y c l e \" s t a r t i n g w i t h n o n - m a r i n e b e d s a n d g r a d i n g u p t o a m a r i n e f o r m a t i o n \" . T h e n o n - t u r b i d i t e ( s h a l e y ) p a r t o f t h e C e d a r D i s t r i c t F o r m a t i o n i s c o n s i d e r e d b y t h e m as' a l i t t o r a l f a c i e s ( \" H a s l a m - t y p e f a c i e s \" ) o f t h e s e c o n d c y c l e o f s e d i -m e n t a t i o n ; t h e y c o n s i d e r t h e t u r b i d i t e p a r t o f t h e f o r m a t i o n t o r e p r e s e n t d e e p e r w a t e r d e p o s i t i o n . T h e l i t h o l o g y i s m a r k e d b y b o t h v e r t i c a l a n d l a t e r a l v a r i a t i o n , a n d o n l y a f e w o f t h e f o r m a t i o n s h a v e a w i d e l a t e r a l e x t e n t ; a m o n g t h e l a t t e r , t h e m a r i n e s h a l e s a n d t h e r h y t h m i c s a n d s t o n e - s h a l e s e q u e n c e a r e t h e b e s t e x a m p l e s . T h e N a n a i m o G r o u p r e s t s u n c o n f o r m a b l y a b o v e L a t e P a l e o z o i c ( E a r l y P e r m i a n ) m e t a m o r p h o s e d v o l c a n i c a n d s e d i m e n t a r y r o c k s o f t h e S i c k e r G r o u p , T r i a s s i c - J u r a s s i c v o l c a n i c s o f t h e V a n c o u v e r G r o u p a n d L a t e J u r a s s i c a n d / o r E a r l y C r e t a -c e o u s a c i d i c i n t r u s i o n s . E r o s L o n a l r e l i e f a l o n g t h i s u n c o n -f o r m a b l e s u r f a c e i s l o c a l l y v e r y l a r g e ; C l a p p (1914) r e p o r t e d r e l i e f o f u p t o 2,000 f e e t , a n d B u c k h a m ( i n W.B. H o e n , 1958) r e c o r d e d a b o u t 440 f e e t o f r e l i e f i n t h e n o r t h -e r n p a r t o f t h e a r e a . T h e N a n a i m o G r o u p o c c u r s i n f i v e s e p a r a t e a r e a s , 7 interpreted by Hqen (195$) as representing separate sedimen-tary basins. These \"basins\" are the Nanaimo, Comox, Cowichan, Alberni, and Suquash basins, of which the Nanaimo and the Comox basins are the largest in area. A prominent . ridge of volcanic rocks of the Vancouver Group separates the southern basins (Nanaimo and the Cowichan) from the northern basins (Comox and Alberni). This ridge l i e s across Nanoose Bay, about 10 miles northwest of the city of Nanaimo. J.D. Mackenzie 1922 ( in Hoen, 1958) believed that the Comox and Alberni basins were originally a single basin-. Usher (1952) placed a l l of the formations included in the Nanaimo Group into two major basins, the Nanaimo south of basin /\\ 'Mannose Bay, and the Comox basin to the north. Hence, he grouped the Comox and the Alberni basins ( he did not consider the Suquash basin) in one basin he called the Comox basin, and the Nanaimo and the Cowichan basins into another basin which he termed the Nanaimo basin. These two major basins have in general similar faunal and lit h o l o g i c a l successions,' and during times of maximum marine flooding must have been connected. However, a separate set of names has been applied to each of the two basins by Usher (1952). The following are the reasons presented by Usher for the separate terminology in the two basins: - ( l ) Lack, in the Comox basin, of formations equivalent to some of the lowest in the Nanaimo basin; (2) differences AGE NANAIMO BASIN FORMATION THICKNESS IN FEET LITH0L0GY itian G a b r i o l a 2,000-3,000 Sandstone Maestricl-Northumberland 2,000-2,700 Shale Sandstone Maestricl-Shale De Courcy 800-1,000 Sandstone Cedar D i s t r i c t 333(?)-158fc Shale & Sandstone nian P r o t e c t i o n 6 5 0 • ' Sandstone Gampa iges N ewcastle 215-400 ' Sandstone,Shale; Newcastle & Doug-l a s c o a l seams a o Cranberry 2 0 0 - 6 0 0 Sandstone, , Conglomerate rer Campanian _ or Santonian E x t e n s i o n 600-800 Conglomerate, Sandstone rer Campanian _ or Santonian E a s t W e l l i n g t o n member 35 Sandstone{Wellin-gton c o a l seam rer Campanian _ or Santonian Haslam 600-1,500 Shale rer Campanian _ or Santonian $ —» o C- Benson 100 Conglomerate J Table 1: L i s t of the Nanaimo Group formations in the . Nanaimo \"basin. Modified from Usher (1952) & Wynne (1959). 9 i n the coal horizons i n the two areas; (3) d i s t i n c t i o n s between the respective faunas;- and (4) d i f f i c u l t i e s encoun-tered i n t r y i n g to apply formational names over a; consider-able distance to stratigraphic units that show a pronounced l a t e r a l v a r i a t i o n i n l i t h o l o g y . The f i r s t reason proved to be incorrect as w i l l be seen l a t e r . Table 1 l i s t s the formations i n the Nanaimo basin (adopted from Usher, 1952 with minor modifications). More recent work based on detailed microfaunal and macrofaunal investigations has shown that the lowest formations i n the Comox basin are as old as those of the lowest i n the Nanaimo basin (McGugan, 1962 , and 1964 , f i g . 2 , and Muller and Jeletzky, 1967 , table 2 ) , J.E. Muller (personal communications) i s i n c l i n e d to think of two major basins of deposition: (1) the Nanaimo-Comox basin which includes the Nanaimo, Cowichan, Comox, and the Alberni basins; (2) the Suquash basin. b. Structure Discussion of the structure of the Nanaimo Group w i l l be confined to the Nanaimo basin since t h i s research was carried out i n the Nanaimo basin only. The general structure of the Nanaimo Group i n the Gulf Islands and v i c i n i t y i s a northeast dipping monocline 10 F i ^ . 3: Two sets of i n t e r s e c t i n g j o i n t s , i n sandstone B e d w e l l Harbour, North Pender I s l a n d ; F i g . 4: Two sets of i n t e r s e c t i n g j o i n t s i n s h a l e . B e d w e l l Harbour, North Pender I s l a n d . F i g l 5 V a r i a t i o n i n spac ing of j o i n t s w i t h v a r i a t i o n i n bed t h i c k n e s s , J o i n t s i n t h i c k sandstone beds are wider spaced than j o i n t s i n the t h i n n e r beds. Bedwel l Harbour, North Pender I s l a n d . 11 w i t h n u m e r o u s NV/-SE t r e n d i n g f o l d s a n d a s s o c i a t e d f a u l t s . T o w a r d t h e n o r t h , f o l d s a r e b r o a d e r w i t h f e w f a u l t s b u t b e c o m e m o r e t i g h t l y f o l d e d w i t h n u m e r o u s f a u l t s s o u t h w a r d (Wynne 1959), f i g u r e 2. L i m b s o f f o l d s i n t h e n o r t h e r n p a r t o f t h e b a s i n h a v e a v e r a g e d i p s r a n g i n g f r o m 12° t o 20°, a n d a v e r a g e t r e n d s r a n g i n g f r o m N30°W t o M55°W. To t h e s o u t h , o n S a l t S p r i n g a n d N o r t h P e n d e r I s l a n d s , d i p s a s h i g h a s 60°and 7 S°were r e c o r d e d . J o i n t i n g h a s n o t b e e n m e n t i o n e d b y t h e p r e v i o u s w o r k e r s e x c e p t f o r C l a p p (1914) who i n d i c a t e d t h e i r i r r e g u l a r i t y , a n d , i n a f e w p l a c e s , t h e p r e s e n c e o f p a r a l l e l s h e e t j o i n -t i n g . F r o m t h e p r e s e n t a u t h o r ' s e x p e r i e n c e w i t h t h e r o c k s o f t h e C e d a r D i s t r i c t F o r m a t i o n , i t w a s o b s e r v e d t h a t t h e r e a r e a t l e a s t t w o s e t s o f j o i n t s i n t e r s e c t i n g a t a n a n g l e w h i c h v a r i e s f r o m a p p r o x i m a t e l y 90° t o a b o u t 50°. T h e s e j o i n t s a r e p r e s e n t i n t h e s a n d s t o n e s a n d t h e s h a l e s o f t h e f o r m a t i o n ( f i g s . 3 a n d 4 ) . I t w a s a l s o o b s e r v e d t h a t t h e s e j o i n t s t e n d t o b e m o r e w i d e l y s p a c e d i n t h e t h i c k b e d s a n d c l o s e l y s p a c e d i n t h e t h i n n e r o n e s ( f i g . 5). c . P r e v i o u s W o r k o n t h e N a n a i m o G r o u p N o t h i n g h a s b e e n p u b l i s h e d p r i o r t o t h i s t h e s i s o n t h e d e t a i l e d s e d i m e n t o l o g i c a l a n d p a l e o g e o g r a p h i c a l a s p e c t s o f 12 the Nanaimo Group rocks. Most previous work has focused on the s t r a t i g r a p h y and paleontology of these rocks. For d e t a i l e d review of t h i s previous work, the reader i s r e f e r r e d t o Usher (1952, p.2 - 6 ) , and t h i s s e c t i o n w i l l deal the only w i t h the major c o n t r i b u t i o n s t o understanding of the geology of the Nanaimo Group, drawn mainly from Usher (1952) and from more recent p u b l i c a t i o n s . The e a r l i e s t work on the rocks of Late Cretaceous age along the southeastern coast of Vancouver I s l a n d began ne a r l y a century ago. I n t e r e s t i n these rocks began w i t h the d i s c o v e r y of extensive c o a l deposits i n them i n 1#35. Their age remained unknown u n t i l 1&57 when Newberry ( i n Usher, 1952) s t a t e d that they belonged to the. Cretaceous System. James Richardson made the f i r s t systematic s t r a t i -g r a p h i c a l , s t r u c t u r a l , and p a l e o n t o l o g i c a l studies of the Nanaimo Group c o a l f i e l d s ( J . Richardson, 1871 -72 , 1872-73, and 1876-77). He d i v i d e d the succession i n t o many rock-s t r a t i g r a p h i c u n i t s that he c a l l e d \" D i v i s i o n s \" , which l a t e r came to be known as formations. G.M. Dawson, i n the course of g e o l o g i c a l e x p l o r a t i o n of B r i t i s h Columbia between 1875 and 1$90, d i d extensive work on the c o a l f i e l d s of Vancouver I s l a n d . He named a l l Cretaceous rocks on eastern Vancouver I s l a n d the \"Nanaimo Group\" (Dawson, 1#90). The f i r s t comprehensive work on i 3 the i n v e r t e b r a t e f o s s i l s of the group was c a r r i e d out by Whiteaves i n 1$79 ( i n Usher, 1952). Clapp made f u r t h e r i n -v e s t i g a t i o n s of the Upper Cretaceous, as w e l l as of the ol d e r , and younger rocks of the east coast of Vancouver Is l a n d i n the years between 190$ and 1917. He has been cre-d i t e d f o r naming the formations of the Nanaimo Group i n the Nanaimo map-area (Clapp 1911, and 1914) . In the years 1945 and 194$, Usher made a d e t a i l e d p a l e -o n t o l o g i c a l i n v e s t i g a t i o n i n the Comox and the Nanaimo basins (Usher, 1952). He introduced a fo r m a t i o n a l s u b d i v i -s i o n of the Nanaimo Group which was s l i g h t l y modified from Clapp's (1914). Usher's p u b l i c a t i o n (1952) has an e x c e l l e n t d e s c r i p t i o n of the formations, i n c l u d i n g a systematic des-c r i p t i o n of the enclosed macrofauna, R i c h f i e l d O i l Corpora-t i o n ^ c a r r i e d out mapping of the Gulf Islands i n 195$, and assembled a g e o l o g i c a l map w i t h a scale of 2 miles to the inc h (Wynne, 1959)• McGugan, i n the years 195$ and 1959 made extensive sampling of the shaley formations i n the Nanaimo and Comox basins, and studied, t h e i r f o r a m i n i f e r a l assemblages. He subdivided the Nanaimo Group i n t o three zones based on f o r a -m i n i f e r a (McGugan, 1962 and 1964). J.E. M u l l e r i n the course of h i s r e g i o n a l mapping on Vancouver I s l a n d f o r the Geologi-c a l Survey of Canada, which s t a r t e d i n 1963 and Is s t i l l i n *4-p r o g r e s s , remapped t h e Nanaimo Group. M u l l e r ' s and J.A. J e l e t z k y ' s work has r e s u l t e d i n i n t r o d u c i n g a b i o c h r o n o -l o g i c a l - l i t h o l o g i c a l r e l a t i o n s h i p bet\\^een t h e f o r m a t i o n s i n t he Nanaimo, Comox, and the Suquash b a s i n s ( M u l l e r and J e l e t z k y , 1967). D.L. S c o t t (1967) has p r e s e n t e d the f i r s t d e s c r i p t i o n o f the se d i m e n t a r y s t r u c t u r e s e x h i b i t e d by some f o r m a t i o n s i n t h e Nanaimo Group, e s p e c i a l l y graded b e d d i n g and the presence o f t u r b i d i t e s . He a l s o s u g g e s t e d , t h a t some more d e t a i l e d work s h o u l d be done on the p e t r o l o g i c a l , s e d i m e n t o l o g i c a l , and paleoe n v i r o n m e n -t a l a s p e c t s o f t h e s e f o r m a t i o n s . D. Te r m i n o l o g y A p p l i e d t o T u r b i d i t e Sequences The f o l l o w i n g g e n e r a l d i s c u s s i o n w i l l s e r v e t o i n t r o d u c e t h e r e a d e r t o c e r t a i n a s p e c t s o f t u r b i d i t e t e r -m i n o l o g y , and t o d e s c r i b e t h e pr o c e d u r e s f o l l o w e d by t h e a u t h o r i n s t u d y i n g the r o c k s w h i c h a r e t h e s u b j e c t o f t h i s i n v e s t i g a t i o n . By d e f i n i t i o n t u r b i d i t e s are the r o c k s o r sediments d e p o s i t e d by t u r b i d i t y c u r r e n t s . S i n c e t h e p o s t u l a t i o n , by Kuenen and M i g l i o r i n i (1950), t h a t t u r b i d i t y c u r r e n t s a r e a l i k e l y mechanism f o r t r a n s p o r t i n g sandy m a t e r i a l s t o deep w a t e r , and f o r the f o r m a t i o n o f graded b e d d i n g , many r o c k s o f t h i s n a t u r e have been s t u d i e d i n d i f f e r e n t -15-^ ^ ^ ^ ^ 4 P E L I T I C DIVISION ^E-division^ UPPER DIVISION OF P L A N E -P A R A L L E L LAMINATION ( WITH S M A L L CURRENT RIPPLES) (^D-divisionj DIVISION OF CURRENT RIPPLE AND C O N V O L U T E LAMINATION ^C-divisionj LOWER DIVISION OF P L A N E . PARALLEL LAMINATION ^B-division^ G R A D E D DIVISION ^A-divisior^ F i g . 6: A complete t u r b i d i t e u n i t and i t s d i v i s i o n s i n an id e a l t u r b i d i t e . Modified from Bouma (1962), Walker (196?), & Hubert (1967). Thicknesses of the ind i v i d u a l units may range from a few inches to a few feet. 16 p a r t s o f the w o r l d and i n d i f f e r e n t p a r t s o f the g e o l o g i c column. Bouma (1962), i n h i s s t u d y o f the f l y s c h d e p o s i t s o f the A l p M a r i t i m e s i n Europe, observed t h a t i n a. complete t u r b i d i t e u n i t ( f i g . 6) (a u n i t here might r e p r e s e n t one or more beds, o f t h i c k n e s s v a r y i n g from an i n c h t o a few f e e t ) t h e r e a r e f i v e d i v i s i o n s , c a l l e d i n t e r v a l s by Bouma (1962) and d i v i s i o n s by Walker (1965). These d i v i s i o n s a r e as f o l l o w s from the bottom t o t h e t o p of the t u r b i d i t e u n i t ( reproduced from Bouma 1962, p. 49 w i t h some m o d i f i -c a t i o n ) . : a. Graded D i v i s i o n ( A - d i v i s i o n ) : - The bottom p a r t o f t h i s d i v i s i o n c o n s i s t s o f sand, showing more or l e s s d i s t i n c t graded b e d d i n g . T h i s g r a d i n g may be i n d i s t i n c t o r even absent i f t h e m a t e r i a l i s w e l l s o r t e d . The t e x -t u r e o f t h i s d i v i s i o n i s sandy and sometimes g r a n u l e s and pebble's may be f o u n d . O c c a s i o n a l l y s o l e markings are p r e s e n t a t the lo w e r c o n t a c t of t h i s d i v i s i o n , and t h e y range from l o a d c a s t s t o s c o u r marks. b. Lower D i v i s i o n o f P l a n e - P a r a l l e l L a m i n a t i o n (B- d i v i s i o n ) : - I n t h i s d i v i s i o n p a r a l l e l l a m i n a t i o n due t o an a l t e r n a t i o n o f more and l e s s c l a y e y sand laminae p r e -dominates. G r a d i n g may be p r e s e n t , but l a m i n a t i o n predo-m i n a t e s . The c o n t a c t between the A- and B- d i v i s i o n s i s g e n e r a l l y g r a d a t i o n a l . 17 c. Division of Current Ripple and Convolute Lamination (C-division;:- This division consists of cur-rent ripples, which are in most cases less than 5 cm thick. A distinct fore-set lamination i s often v i s i b l e . Sometimes the ripples are more or less oversteepened or convoluted; convolute lamination, i f present in the turbidite unit, i s restricted to this division. The contact between the B-and C- divisions i s either sharp or gradational. d. Upper Division of Plane-Parallel Lamination (D-division):- An indistinct lamination is characteristic of this division, but i f the layer i s weathered or defor-med the lamination becomes inv i s i b l e . The material con-sists of a very sandy to s i l t y clay. Sometimes an upward decrease in sand content i s v i s i b l e . The contact between the C-division and this division i s usually very distinct. e. P e l i t i c Division (E-division):- The upper d i v i -sion of the turbidite unit shows no visi b l e sedimentary structures. A small upward decrease in grain size and . sand content may be found. Often, a rapid upward increase in the lime content i s found. Foraminifera may be found in this p e l i t i c division. Their number generally i n -creases with increase of lime content and decrease of grain size. The contact between the upper two divisions generally i s completely gradational. Because the a u t h o r has not been a b l e t o d i s t i n g u i s h i a between the upper two divisions in the f i e l d , in the present study the upper two divisions have been grouped under one division which i s called interturbidite d i v i -sion (DE-division) (Walker, 1 9 6 ? ) * The term interturbi-dite i s suitable for the upper f-wo divisions because they represent deposition of sediments by normal gravity settling between two periods of turbidity current deposi-tion. In discussing the f i e l d techniques and the use of the logging chart, the author w i l l refer to the divisions by their respective letters (e.g. graded division i s the A-division, lower division of parallel lamination i s the B-division .... etc. ). The reader should be aware that the above descrip-tion of the different divisions might not be representive of turbidites in general a l l over the world, but they des-cribe the turbidites of the Alpe Maritimes in Europe (Bouma, 1 9 6 2 ) , and they show agreement to a large extent with the turbidites of the present study. A number of workers have related the various divisions to flow condi-tions within a turbidite current, as w i l l be discussed subsequently. E . Methods of Study The f i e l d phase of this investigation focused on . •• - 1 9 -D O D D N A R R O W S V A N C O U V E R I S L A N D V E S U V I U S B A Y S A L T S P R I N G I S L A N D DE COURCY FORMATION O \\ \\ 7. ? ? l O W E H C O N T A C T U N E X P O S E D L E G E N D Sondstone C o k o r « « C o „ c r . h o o , S o f t . Sediment D e f o r m a t i o n In Sandstone Sandstone Dikes In Shale V,ojy^° «*«<'»tone £ 0 5 = ^ ? Conglomerate L S I - i r e d Intervals D€ COURCY FORMATION C E D A R D I S T R I C T F O R M A T I O N S C A L E K » l l N O R M A t C O N TA C T B E D W E L L Hbr. N O R T H P E N D E R I S L A N D 2 m i l e s COLUMNAR SECTIONS OF THE CEDAR DISTRICT FORMATION BRITISH COLUMBIA, CANADA S A T U R N A I S L A N D DE COURCY FORMATION ? C E D A R D I S T R I C T F O R M A T I O N Q U E S T I O N A B L E C O N T A C T FAULTED C O N T A C T 20 d e t a i l e d measurements o f s e c t i o n s o f the Cedar D i s t r i c t F o r m a t i o n i n d i f f e r e n t p a r t s of the a r e a . Because o f the s c a r c i t y o f o u t c r o p s f a v o r a b l e f o r t h i s k i n d o f s t u d y , two complete s e c t i o n s , , one q u e s t i o n a b l y complete s e c t i o n - , and one p a r t i a l s e c t i o n , ( r e p r e s e n t i n g o n l y the upper p a r t of the f o r m a t i o n ) v/ere measured ( f i g . 7 ) . F i e l d work was conducted m a i n l y on the wave cu t c l i f f s , s i n c e t h e s e e x h i b i t the b e s t o u t c r o p s . I n l a n d , the r o c k s t e n d t o be covered e i t h e r by s o i l and v e g e t a t i o n o r by g l a c i a l d e p o s i t s , and a t b e s t , o n l y p a r t i a l s e c t i o n s are exposed; The b e s t s e c t i o n s are found a l o n g s h o r e l i n e s a p p r o x i m a t e l y p e r p e n d i c u l a r t o t h e s t r i k e o f the f o r m a t i o n . a. F i e l d Techniques S y s t e m a t i c l o g g i n g o f the measured s e c t i o n s has been c a r r i e d i n two ways depending on the p e r c e n t a g e and d i s -t r i b u t i o n o f the sandstone beds, as f o l l o w s : (1 ) I n p a r t s o f s e c t i o n s where sandstone beds a r e few and s h a l e dominates, 5 - f o o t i n t e r v a l s v/ere measured by Jacob's s t a f f , and the p e r s e n t a g e o f the sandstone was c a l c u l a t e d w i t h i n each 5 - f o o t i n t e r v a l . (2) I n o t h e r p a r t s o f s e c t i o n s where sandstone beds ar e abundant, d e t a i l e d i n c h - b y - i n c h l o g g i n g was conducted. T h i s l o g g i n g included.measurements of the t h i c k n e s s , c o l o r , g r a i n s i z e , and s e d i m e n t a r y s t r u c t u r e s f o r each d i v i s i o n 21 within each separate turbidite unit. Paleocurrent direc-tions were measured from directional sedimentary structu-res within the turbidite units and along bedding planes, along with sampling, sketching and photography. A l l of these data v/ere recorded in a tabulated form in the f i e l d on a graph paper r o l l . The appendix at the end of this thesis shows a sample of a logging chart and i t s explanation, the properties measured and their symbols. b. Laboratory Techniques Microscopic: Petrographic examination of the different rocks was conducted, with special emphasis on the sand-stones. Quantitative compositional analysis of 26 sand-stone samples was done by point counting which included counting from 400 to 700 counts per thin section depend-ing on the grain size, the least counts being made on fine-grained sandstones. The size of 100 grains was measured in 15 sandstone thinsections to determine the size distribution; no attempt was made to convert the thin-section size d i s t r i -bution (number) into the sieve-size distribution (weight) as was done previously by Friedman (195$, and 1962) , since he delt with well sorted sandstones. Qualitative 22 m i c r o s c o p i c e x a m i n a t i o n o f 8 s h a l e s a m p l e s a n d 1 1 c a l c a -r e o u s c o n c r e t i o n s a m p l e s w a s d o n e f o r t h e p u r p o s e o f d e -t e r m i n i n g t h e i r c o m p o s i t i o n * F e l d s p a r S t a i n i n g ; -T h i n s e c t i o n s o f 12 s a n d s t o n e s a m p l e s , c h o s e n f r o m d i f f e r e n t l e v e l s w i t h i n t h e s e c t i o n i n f i v e l o c a l i t i e s , w e r e s t a i n e d f o r f e l d s p a r . T h e m e t h o d c o n -s i s t s o f e t c h i n g t h e t h i n s e c t i o n s f o r a p p r o x i m a t e l y 4 0 s e c o n d s w i t h h y d r o f l u o r i c a c i d f u m e s a n d t h e n d i p p i n g t h e m i n t o s o d i u m c o b a l t i n i t r i t e s o l u t i o n f o r 4 0 s e c o n d s . T h e K - f e l d s p a r s a r e s t a i n e d y e l l o w , p l a g i o c l a s e f e l d s p a r s w h i t e , a n d q u a r t z i s u n a f f e c t e d . N e x t , t h e p e r c e n t a g e o f K - f e l d s p a r v/as d e t e r m i n e d b y p o i n t c o u n t i n g u n d e r t h e m i c r o s c o p e . X - R q y A n a l y s i s : F i v e s h a l e s a m p l e s w e r e a n a l y s e d b y x - r a y d i f f r a c t i o n f o r s e m i - q u a n t i t a t i v e c l a y m i n e r a l o g y a n d d e t e r m i n a t i o n o f K a d i r i t e / I l l i t e r a t i o . F o u r s a n d s t o n e s a m p l e s v / e r e a n a l y s e d s e l e c t i v e l y f o r t h e m i n e r a l o g i c c o m p o s i t i o n o f t h e c l a y - s i z e m a t r i x . T h i s w a s d o n e b y c r u s h i n g e a c h r o c k s a m p l e , s i e v i n g t h e m t h r o u g h a 2 3 0 m e s h s c r e e n ( U . S . S t a n d a r d ) , a n d c o l l e c t i n g t h e p o r t i o n o f t h e s a m p l e w h i c h p a s s e d t h r o u g h t h i s s c r e e n ; A l l t h e s a m p l e s w e r e t r e a t e d t o g e t r i d o f t h e c a l c i u m c a r b o n a t e , 23 o r g a n i c m a t t e r , a n d i r o n o x i d e s i n o r d e r t o m i n i m i z e a n y p o s s i b l e e f f e c t s o f f l o u r e s c e n c e f r o m t h e s e m a t e r i a l s d u r i n g t h e p r o c e s s o f x - r a y i n g . T h e s a m p l e s w e r e n e x t c e n t r i f u g e d i n o r d e r t o r e c o v e r t h a t p o r t i o n o f t h e s a m p l e l e s s t h a n o r e q u a l t o t w o m i c r o n s , w h i c h w a s t h e n x - r a y e d . E l e c t r o n M i c r o s c o p y : T h r e e c a l c a r e o u s c o n c r e t i o n s a m p l e s w e r e e x a m i n e d u n d e r t h e e l e c t r o n m i c r o s c o p e a f t e r m a k i n g r e p l i c a s o f p a r t o f t h e s a m p l e s ' s u r f a c e s b y t h e t w o -s t a g e r e p l i c a m e t h o d ( H o n j o a n d F i s c h e r , 1965). P u r p o s e o f t h i s p a r t o f t h e i n v e s t i g a t i o n w a s t o s t u d y m i c r o -t e x t u r e s a n d r e c o g n i z e a n y f o s s i l n a n n o p l a n k t o n . 2, D I S T R I B U T I O N , T H I C K N E S S , AND STRUCTURE • OF THE CEDAR D I S T R I C T FORMATION T h e o u t c r o p a r e a o f t h e C e d a r D i s t r i c t F o r m a t i o n e x -t e n d s f r o m t h e m o u t h o f t h e N a n a i m o R i v e r d e l t a o n V a n c o u v e r I s l a n d o n t h e n o r t h w e s t , t o S u c i a I s l a n d i n W a s h i n g t o n S t a t e o n t h e s o u t h e a s t ( f i g * 2). S u c i a I s l a n d i s s i t u a t e d 5 m i l e s s o u t h e a s t o f S a t u r n a I s l a n d , b u t i s n o t s h o w n o n t h e map o f f i g u r e 2. On V a n c o u v e r I s l a n d , t h e f o r m a t i o n u n d e r l i e s a w i d e v a l l e y w i t h a n e a r l y n o r t h - s o u t h t r e n d e x t e n d i n g f r o m t h e 24 m o u t h o f t h e N a n a i m o R i v e r t o L a d y s m i t h H a r b o u r a n d p a s -s i n g t h r o u g h t h e C e d a r D i s t r i c t a r e a ( w h e r e t h e f o r m a t i o n w a s f i r s t d e f i n e d b y C H . C l a p p , 1914). W i t h i n t h i s v a l l e y t h e f o r m a t i o n i s c o v e r e d l a r g e l y b y d r i f t , b u t t h e r e a r e s e v e r a l s m a l l s c a t t e r e d o u t c r o p s , a n d p o r t i o n s o f t h e f o r m a t i o n a r e f a i r l y w e l l e x p o s e d a t a f e w p l a c e s a l o n g t h e N a n a i m o R i v e r ( C l a p p , 1914). I t i s a l s o e x -p o s e d 2 t o 3 m i l e s t o t h e e a s t , o n t h e s h o r e s o f V a n c o u v e r a n d M u d g e I s l a n d s s u r r o u n d i n g t h e D o d d N a r r o w s , o c c u r r i n g o n t h e l i m b s o f a p l u n g i n g a n t i c l i n e ( o n l y t h e u p p e r p a r t o f t h e f o r m a t i o n i s e x p o s e d h e r e ) . I n t h e l a t t e r a r e a t h e b e d s d i p a t a n a n g l e w h i c h v a r i e s f r o m 11° t o 3 2 ° , a n d t h e s t r i k e c h a n g e s r a p i d l y w i t h i n a s h o r t d i s t a n c e d u e t o t h e f a c t t h a t t h e b e d s a r e l o c a t e d n e a r t h e n o s e o f a p l u n g i n g a n t i c l i n e , a n d b e c a u s e o f s o f t s e d i m e n t d e f o r m a t i o n . T h e a u t h o r d i d n o t a t t e m p t o m e a s u r e t h e s e c t i o n i n t h i s a r e a b e c a u s e o f t h e com-p l e x i t i e s m e n t i o n e d a b o v e . B u t a t h i c k n e s s o f 1010 f e e t h a s b e e n m e a s u r e d b y J . E . M u l l e r i n 1967 o f t h e G e o l o g i -c a l S u r v e y o f C a n a d a ( p e r s o n a l c o m m u n i c a t i o n ) , t h i s t h i c k n e s s r e p r e s e n t i n g t h e u p p e r p a r t o f t h e f o r m a t i o n . T h e b a s e i s n o t e x p o s e d h e r e ( f i g . 2 ) . On S a l t S p r i n g I s l a n d , t h e f o r m a t i o n o u t c r o p s i n t w o b e l t s , o n e o n t h e n o r t h e r n a n d n o r t h e a s t e r n p a r t o f t h e 25 i s l a n d where i t forms s e v e r a l minor f o l d s w i t h d i p s f rom 11° t o 6 2 ° ; i n t h i s a r e a o n l y t h e upper p a r t o f the f o r -m a t i o n i s exposed. The second b e l t extends from V e s u v i u s Bay on t h e n o r t h w e s t c o a s t of t h e i s l a n d t o Ganges Har-bour on t h e s o u t h e a s t c o a s t . A l o n g t h i s b e l t , t h e f o r -m a t i o n i s w e l l exposed o n l y on the beaches and t h e ad-j a c e n t low c l i f f s o f Ganges Harbour and V e s u v i u s Bay. I n V e s u v i u s Bay, t h e beds d i p v e r y s t e e p l y t o the n o r t h -east,- t h e d i p a n g l e v a r y i n g from 71° t o $ 0 ° . A t h i c k -ness o f 1503 f e e t has been measured i n Ves v i u s Bay, where o n l y 19% o f the sequence was c o v e r e d by beach g r a v e l and sand,- I n the Ganges H a r b o u r - r e g i o n t h e beds d i p s t e e p l y , assuming a v e r t i c a l a t t i t u d e and o c c a s i o n a l -l y b e i n g o v e r t u r n e d , ( f i g . 2 ) . The upper 150-200 f e e t of the f o r m a t i o n a l s o o u t -c r o p s on the n o r t h and n o r t h e a s t c o a s t o f P r e v o s t I s l a n d , f o r m i n g a narrow s t r i p a l o n g the beach and the nearby c l i f f s . I t i s exposed here on the s o u t h w e s t e r n l i m b o f the T r i n c o m a l i A n t i c l i n e , the a x i s o f w h i c h l i e s i n t h e w a t e r s o f t h e T r i n c o m a l i C h a n n e l . Beds on P r e v o s t I s l a n d d i p from 2$° t o 47° t o t h e southwest, ( f i g . 2 ) . I t a l s o o c c u r e s as a narrow b e l t on the s o u t h e r n c o a s t o f Mayne I s l a n d , f o r m i n g the beach and t h e nearby c l i f f s w h i c h range from 40 t o about 100 f e e t h i g h . 2 6 About t h e upper 2 0 0 f e e t o f the f o r m a t i o n are exposed here, l y i n g on the n o r t h e a s t e r n l i m b of t h e T r i n c o m a l i A n t i c l i n e and d i p p i n g w i t h a n g l e s from 3 3 ° t o 4 5 ° n o r t h e a s t ( f i g , 2 ) . . The f o r m a t i o n forms the core o f the T r i n c o m a l i A n t i c l i n e i n the L y a l l V a l l e y o f S a t u r n a I s l a n d , t h u s t h e base, of the f o r m a t i o n i s not exposed. On the same i s l a n d , the f o r m a t i o n i s exposed a l o n g the beaches and t h e nearby c l i f f s on t h e s o u t h e r n c o a s t , where i t l i e s on.the n o r t h -e a s t e r n l i m b o f t h e f a u l t e d N o r t h Pender A n t i c l i n e , and .• d i p s n o r t h e a s t w i t h a n g l e s v a r y i n g from 2 4 ° t o 31 ° . I n the l a t t e r a r e a , i f ' t he conglomerate ( f i g . 7) a t the base of the exposed s e c t i o n does not b e l o n g t o the Cedar D i s t r i c t F o r m a t i o n , t h e t h i c k n e s s t h e n i s - 333 f e e t , w i t h about 37% c o v e r e d by v e g e t a t i o n , s o i l , and b l o c k s of sandstone from t h e o v e r l y i n g DeCourey F o r m a t i o n ( f i g . 2 ) . But i f t h i s conglomerate b e l o n g s to the Cedar D i s t r i c t F o r m a t i o n (as B r e i t s p r e c h e r , 1 9 6 2 , c o n c l u d e d i n h i s s t u d y of the f o r m a t i o n i n S u e i a I s l a n d ) , the t h i c k n e s s of the Cedar D i s t r i c t F o r m a t i o n w i l l be more t h a n 333 f e e t . The p r e s e n t a u t h o r f e e l s t h a t t h i s eonglemerate (which i s t h i c k e r t h a n 2 0 f e e t j and hsg e h a r a e t e r l i t i e f s o f a beach . conglomerate) does not b e l o n g t o the Cedar D i s t r i c t Ft)r1ft&> t i o n expo.sed he,re,, -wh&gh 2fcs 'ailment ,:'9h^r*e^y % ^H$bi?ci'&Ce 27 On N o r t h P e n d e r I s l a n d t h e f o r m a t i o n o u t c r o p s ' i n t h r e e b e l t s . T h e f i r s t l i e s o n t h e s o u t h w e s t e r n l i m b o f t h e T r i n c o m a l i A n t i c l i n e a t t h e n o r t h e r n c o a s t o f t h e i s l a n d , a n d t h e s e c o n d f o r m s t h e c o r e o f t h e N o r t h P e n d e r A n t i c l i n e a r o u n d P o r t B r o w n i n g . T h e t h i r d b e l t e x t e n d s f r o m t h e B e d w e l l H a r b o u r s o u t h e a s t t o t h e w e s t c o a s t o f t h e i s l a n d . I n t h i s l a t t e r l o c a l i t y a t h i c k n e s s o f 15 #4 f e e t h a s b e e n m e a s u r e d ; b u t a f a u l t e d l o w e r c o n t a c t m i g h t o b s c u r e a g r e a t e r t h i c k n e s s . On B e d w e l l H a r b o u r , t h e f o r -m a t i o n d i p s a t a n g l e s f r o m 5 1 ° t o 6 0 ° n o r t h e a s t . On S o u t h P e n d e r I s l a n d i t f o r m s o n e b e l t a l o n g t h e n o r t h -e a s t e r n l i m b o f a n a n t i c l i n e ( f i g . 2 ) . T h e a u t h o r h a s v i s i t e d a l l t h e a b o v e o u t l i n e d l o c a l i t i e s , e x c e p t f o r t h e a r e a a l o n g t h e N a n a i m o R i v e r a n d t h e e x p o s u r e s o n S o u t h P e n d e r I s l a n d , 3. F O S S I L S , A G E , AND C O R R E L A T I O N M o s t o f t h e f o s s i l s t h a t h a v e b e e n r e c o v e r e d f r o m t h e C e d a r D i s t r i c t F o r m a t i o n came o u t f r o m t h e s h a l e y p a r t o f t h e f o r m a t i o n ; a n d a l m o s t a l l o f t h e s e f o s s i l s w e r e f o u n d o n S a t u r n a a n d S u c i a I s l a n d s , b u t t h e r e a r e some s p a r s e o c c u r r e n c e s o n t h e o t h e r i s l a n d s , ( U s h e r 1 9 5 2 , M c G u g a n 1962 a n d 1 9 6 4 , B r e i t s p r e c h e r 1 9 6 2 , a n d M u l l e r a n d J e l e t z k y 1967) . T h e C e d a r D i s t r i c t F o r m a t i o n m a c r o f a u n a i s c o m p o s e d 2 8 a l m o s t e n t i r e l y o f m o l l u s k s , o f w h i c h t h e c e p h a l o p o d s , p e l y c e p o d s , a n d g a s t r o p o d s a r e t h e m o s t i m p o r t a n t . S c a p h o p o d s a n d s h a r k t e e t h h a v e b e e n r e p o r t e d b y B r e i t -s p r e c h e r (1962) o n S u c i a I s l a n d . R e g a r d i n g t h e m i c r o -f a u n a , b e n t h o n i c f o r a m i n i f e r s a r e t h e d o m i n a n t t y p e , ( M c G u g a n , 1962 a n d 1964, a n d B r e i t s p r e c h e r , 1 9 6 2 ) , w i t h a f e w t o r a r e o c c u r r e n c e s o f o s t r a c o d s . T h e a u t h o r h a d h o p e d t o f i n d c o c c o l i t h s i n t h e s h a l e s a n d t h e c a l c a r e o u s c o n c r e t i o n s . F i v e s a m p l e s o f s h a l e w e r e s e n t t o t h e U n i t e d S t a t e s G e o l o g i c a l S u r v e y m a r i n e l a b o r a t o r y i n L a J o l l a , C a l i f o r n i a t o r e c o v e r c o c c o l i t h s , b u t a l l t h e s a m p l e s \" p r o v e d t o b e c o n s p i c u o u s l y b a r r e n \" , ( D a v i d B u r k y , 1968, w r i t t e n c o m m u n i c a t i o n ) . T h r e e s a m p l e s o f c a l c a r e o u s c o n c r e t i o n s w e r e e x a m i n e d u n d e r t h e e l e c t r o n m i c r o s c o p e , b u t t h e y a l s o c o n t a i n n o v i s i b l e c o c c o l i t h s i T h e C e d a r D i s t r i c t F o r m a t i o n h a s b e e n c o n s i d e r e d t o b e o f L a t e C a m p a n i a n a g e b y a l l t h e p r e v i o u s w o r k e r s who i n v e s t i g a t e d t h e p a l e o n t o l o g y o f t h e f o r m a t i o n . T h i s a g e w a s i n d i c a t e d b y some a m m o n i t e s a n d b e n t h o n i c f o r a m i n i -f e r s , ( U s h e r , 1952, B r e i t s p r e c h e r , 1962, M c G u g a n , 1962 a n d 1964, a n d M u l l e r a n d J e l e t z k y , 1967), s e e t a b l e 1. T h e s t r a t i g r a p h i c s e c t i o n s m e a s u r e d o n S a t u r n a , N o r t h P e n d e r , S a l t S p r i n g , a n d V a n c o u v e r I s l a n d s a r e s h o w n i n f i g . 7 . On S a t u r n a I s l a n d , c o n s i d e r i n g t h e c o n g l o m e r a t e 29 and t h e u n d e r l y i n g r o c k s (the l a t t e r a re covered by w a t e r ) as p a r t o f the Cedar D i s t r i c t F o r m a t i o n , as B r e i t s p r e c h e r (1962) d i d on S u c i a I s l a n d , and assuming t h a t the minimum t r u e t h i c k n e s s o f the Cedar D i s t r i c t F o r m a t i o n measured by B r e i t s p r e c h e r on S u c i a I s l a n d i s 800 f e e t i n s t e a d o f 1200 f e e t (the l a t t e r t h i c k n e s s i s q u e s t i o n a b l e because o f s t r u c t u r a l c o m p l i c a t i o n s ) , t h e n the t h i c k n e s s of the Cedar D i s t r i c t F o r m a t i o n on S a t u r n a I s l a n d may r e a c h as much as 800 f e e t . A c c o r d i n g l y , t h e t h i c k n e s s of t h e Cedar D i s -t r i c t F o r m a t i o n appears t o i n c r e a s e f r o m S u c i a and S a t u r n a I s l a n d s toward N o r t h Pender and S a l t S p r i n g I s l a n d s , i n o t h e r words from s o u t h e a s t t o n o r t h w e s t . I t i s unknown whether t h e f o r m a t i o n becomes t h i c k e r o r t h i n n e r towards Dodd Narrows i n t h e n o r t h w e s t e r n margin of the study a r e a , s i n c e o n l y the upper 1010 f e e t are exposed. There i s no way t o d i v i d e the f o r m a t i o n i n t o members t h a t c o u l d be c o r r e l a t e d l a t e r a l l y t h r o u g h o u t the s t u d y a r e a , w i t h the p o s s i b l e e x c e p t i o n o f the upper 250 t o 300 f e e t i n t h e N o r t h Pender and S a l t S p r i n g I s l a n d s s e c t i o n s w h i c h are composed o f s i m i l a r a p p e a r i n g t u r b i d i t e sequences. But towards th e northwest i n the Dodd Narrows, t h i s sequence i s not p r e s e n t , and the e n t i r e s e c t i o n t h e r e i s composed o f s h a l e . S i m i l a r t u r b i d i t e sequences are a l s o p r e s e n t i n o t h e r s t r a t i g r a p h i c l e v e l s 30 o f t h e S a l t S p r i n g , N o r t h Pender, and S a t u r n a I s l a n d s s e c -t i o n s , but t h e y are u s u a l l y t h i n n e r t h a n the t u r b i d i t e i n t e r v a l a t the top of t h e f o r m a t i o n on S a l t S p r i n g and N o r t h Pender I s l a n d s . On t h e s t r a t i g r a p h i c s e c t i o n s ( f i g . 7 ) , t h e c o n t a c t between t h e Cedar D i s t r i c t and the DeCourcy F o r m a t i o n s i s as used a r e f e r e n c e l i n e . T h i s i s not meant t o be a time l i n e , s i n c e t h e r e i s no p a l e o n t o l o g i c a l c o n t r o l a v a i l a b l e , but i s used because t h i s c o n t a c t was exposed i n a l l s e c -t i o n s , whereas the lower c o n t a c t w i t h t h e P r o t e c t i o n F o r -m a t i o n i s f a u l t e d on N o r t h Pender I s l a n d and unexposed i n the Dodd Narrows s e c t i o n , and p o s s i b l y a l s o i n the S a t u r n a I s l a n d s e c t i o n . 4. LOWER AND UPPER CONTACTS The Cedar D i s t r i c t F o r m a t i o n l i e s between two sand-stone f o r m a t i o n s , t h e DeCourcy F o r m a t i o n a t i t s t o p , and the P r o t e c t i o n F o r m a t i o n a t i t s bottom. C o n t a c t s w i t h t h e s e u n d e r l y i n g and o v e r l y i n g u n i t s appear to be g r a d a -t i o n a l , and t h e sandstone beds i n t h e Cedar D i s t r i c t F o r -m a t i o n i n c r e a s e i n t h i c k n e s s and number b o t h upwards and downwards toward the a d j a c e n t u n i t s . 31 F i g , .8: . P e b b l y mudstone of S a t u r n a I s l a n d . Dark o b j e c t s (arrows) a r e s l a t e c l a s t s and p e b b l e s o f b a s i c i gneous r o c k s . M ^ l k y q u a r t z p e b b l e s can be seen a t the 'center o f the l e f t h a l f o f t h e p i c t u r e . Note c o n c e n t r i c c o n c r e t i o n a r y w e a t h e r i n g o f the s h a l e m a t r i x (upper r i g h t c o r n e r ) . The s c a l e i s 3 i n c h e s l o n g . F i g . 9: P o r t i o n o f a conglomerate l a y e r t h a t under-l i e s t h e p e b b l y mudstone i n f i g . S . Note the abundance o f m i l k y q u a r t z p e b b l e s . Other p o r t i o n s o f t h i s l a y e r have c o a r s e r p e b b l e s ' a n d c o b b l e s . S a t u r n a I s l a n d . F i g . 10: C o n t a c t o f t h e Cedar D i s t r i c t F o r m a t i o n ( t o the l e f t o f t h e hammer), and t h e P r o t e c t i o n F o r m a t i o n (to t h e r i g h t o f the hammer). Beds d i p a t 78° t o t h e l e f t . V e s u v i u s B a y . - S a l t S p r i n g Island... F i 3 . 10 32 A. L o w e r C o n t a c t T h e l o w e r c o n t a c t o f t h e C e d a r D i s t r i c t F o r m a t i o n i s e x p o s e d a t t h e f o l l o w i n g l o c a l i t i e s : (1) A l o n g t h e s o u t h e r n c o a s t o f S a t u r n a I s l a n d , a s -s u m i n g t h e c o n g l o m e r a t e a t t h e b a s e o f t h e s e c t i o n d o e s n o t b e l o n g t o t h e C e d a r D i s t r i c t F o r m a t i o n , t h e l o w e r c o n t a c t i s w e l l e x p o s e d f o r a d i s t a n c e o f a m i l e a n d a h a l f ; a n d l i e s b e t w e e n a p e b b l y m u d s t o n e s e q u e n c e ( f i g . 8 ) o f 4# f e e t t h i c k n e s s , w h i c h b e l o n g s t o t h e C e d a r D i s t r i c t F o r m a t i o n ; a n d a p e b b l e - c o b b l e c o n g l o m e r a t e ( f i g . 9 ) , w h i c h t h e a u t h o r a s s i g n s t o t h e u n d e r l y i n g f o r m a t i o n . (2) I n B e d w e l l H a r b o u r o f N o r t h P e n d e r I s l a n d , t h e l o w e r c o n t a c t i s f a u l t e d , a n d d a r k g r e y , s i l t y s h a l e b e d s o f t h e l o w e r p a r t o f t h e C e d a r D i s t r i c t F o r m a t i o n l i e w i t h s t r u c t u r a l d i s c o n t i n u i t y a g a i n s t a v e r y t h i c k - b e d d e d s a n d s t o n e o f t h e P r o t e c t i o n F o r m a t i o n . (3) I n V e s u v i u s B a y o n S a l t S p r i n g I s l a n d , t h e l o w e r p a r t o f t h e f o r m a t i o n c o n s i s t s o f i n t e r b e d d e d s a n d -s t o n e ( b e d t h i c k n e s s r a n g e s f r o m 0.3 t o 5 .7 i n c h e s , w i t h a n a v e r a g e o f 1.7 i n c h e s ) a n d s h a l e ( b e d t h i c k n e s s r a n g e s f r o m a f r a c t i o n o f a n i n c h t o 33 i n c h e s a n d a v e r a g e s 5 i n c h e s ) . T h e c o n t a c t w i t h t h e u n d e r l y i n g P r o t e c t i o n F o r -m a t i o n i s d r a w n a t t h e p o i n t w h e r e t h e t h i c k n e s s o f t h e s a n d s t o n e b e d s i n c r e a s e s a b r u p t l y t o m o r e t h a n 3 f e e t ( f i g . 1 0 ) . 33 F i g . 11: S a n d s t o n e b e d s a t t h e b a s e o f t h e D e C o u r c y F o r m a t i o n , n e a r t h e c o n t a c t w i t h t h e u n d e r -l y i n g C e d a r D i s t r i c t F o r m a t i o n . V e s u v i u s B a y . S a l t S p r i n g I s l a n d . F i g . 12: C o n t a c t ( j u s t a b o v e t h e h a m m e r ) b e t w e e n t h e D e C o u r c y F o r m a t i o n a n d t h e u n d e r l y i n g C e d a r D i s t r i c t F o r m a t i o n . D o d d N a r r o w s , V a n c o u v e r I s l a n d . F i g , 13: C o n c e n t r i c c o n c r e t i o n a r y w e a t h e r i n g i n t h e s h a l e o f t h e C e d a r D i s t r i c t F o r m a t i o n . B e d w e l l H a r b o u r , N o r t h P e n d e r I s l a n d . F i g . U : S h a l e s e q u e n c e c u t b y i r r e g u l a r s a n d s t o n e d i k e . N o t e t h e l i g h t c o l o r e d c a l c a r e o u s c o n -c r e t i o n s i n d i c a t e d b y t h e a r r o w s . D o d d N a r r o w s , V a n c o u v e r I s l a n d , F i g . 1 5 : T y p i c a l t u r b i d i t e s e q u e n c e o f i n t e r b e d d e d s h a -l e a n d s a n d s t o n e b e d s , w i t h h i g h s a n d s t o n e p e r -c e n t a g e . S c a l e o n t h e r i g h t i s 3 f e e t l o n g . B e d w e l l H a r b o u r , N o r t h P e n d e r I s l a n d . 34 B. Upper C o n t a c t I n t h e t h r e e l o c a l i t i e s mentioned above, t h i s c o n t a c t i s t y p i c a l l y more g r a d a t i o n a l t h a n t h e lo w e r c o n t a c t . Sandstone beds u s u a l l y i n c r e a s e i n t h i c k n e s s upward. Where t h e s e sandstone beds r e a c h a t h i c k n e s s o f more t h a n 3 f e e t , and where t y p i c a l t u r b i d i t e s t r u c t u r e s a re no l o n g e r f o u n d , t h e upper c o n t a c t of t h e f o r m a t i o n w i t h the o v e r l y i n g De Courcy F o r m a t i o n i s drawn ( f i g . 1 1 ) . On Mayne I s l a n d , i n c o n t r a s t , t h i s c o n t a c t i s s h a r p . Sandstone beds change a b r u p t l y from t h i n - b e d d e d (about 6 i n c h e s t h i c k ) i n the topmost Cedar D i s t r i c t F o r m a t i o n t o v e r y t h i c k - b e d d e d ( o v e r 3 f e e t t h i c k ) i n the l o w e r -most De Courcy F o r m a t i o n . A l o n g t h e e a s t c o a s t o f Vancouver I s l a n d around the Dodd Narrows, t h e upper c o n t a c t i s e x t r e m e l y s h a r p . Here, dark g r e y s i l t y s h a l e , w h i c h composes almost t h e e n t i r e exposed p a r t o f t h e Cedar D i s t r i c t F o r m a t i o n , l i e s d i r e c t l y below m a s s i v e , v e r y t h i c k - h e d d e d sandstone o f the De Courcy F o r m a t i o n ( f i g . 1 2 ) . 5. GROSS LITHOLOGY , The Cedar D i s t r i c t F o r m a t i o n i s a r e l a t i v e l y t h i c k sequence o f a l t e r n a t i n g marine s h a l e s and sandstones.-S h a l e c o m p r i s e s a p p r o x i m a t e l y 73% by t h i c k n e s s o f the 35 measured p o r t i o n s . Sandstone i s second i n abundance. Calcareous concretions occur throughout most of the sec-t i o n , commonly ass o c i a t e d w i t h shale but a l s o found asso-c i a t e d w i t h sandstones. A bed of pebble-breccia, averag-i n g f i v e inches t h i c k , i s found only i n North Pender Is l a n d s e c t i o n . The b a s a l 4$ f e e t of the Saturna I s l a n d s e c t i o n i s composed of pebbly mudstone that contains.a range of very angular to w e l l rounded pebbles,and cobbles of v a r y i n g composition along w i t h sandstone c l a s t s of v a r y i n g shape and s i z e . A. Shale The Cedar D i s t r i c t shales are grey, b l u i s h grey to brownish grey when f r e s h and dry. G e n e r a l l y they are s i l t y to sandy, and t h i n s e c t i o n s contain black spots of p y r i t e and carbonaceous matter. They are h i g h l y indu-r a t e d , p o s s i b l y due to the very f i n e - g r a i n e d s i l i c e o u s cement. They show f i n e l a m i n a t i o n , and commonly.posses concentric concretionary weathering ( f i g . 13)• I n t e r v a l s of shale range i n t h i c k n e s s from continuous s e c t i o n s hundreds f e e t i n thickness.., w i t h no c l e a r bedding except f o r the l a m i n a t i o n ( f i g . 14), to w e l l defined l a y e r s interbedded w i t h sandstones ( f i g . 15), to mere pa r t i n g s separating succesive sandstone beds. The cumulative frequency of the t h i c k n e s s of 7 2 7 . -36- .. C u m u l a t i v e P e r c e n t a g e PROBITS F i g . 16 39 s h a l e b e d s ( i . e ; D E - d i v i s i o n ) f r o m S a l t S p r i n g a n d N o r t h P e n d e r I s l a n d s , g r o u p e d i n t o o n e i n c h c l a s s i n t e r v a l s ^ i s p l o t t e d o n l o g a r i t h m i c p r o b a b i l i t y p a p e r ( f i g s . l6 j 17, a n d IS).- T h e r e a r e a l s o a f e w s h a l e b e d s r e a c h i n g a t h i c k n e s s o f a b o u t t h r e e f e e t ; b u t t h e y a r e n o t a b u n d a n t e n o u g h t o b e p l o t t e d o n a c u m u l a t i v e f r e q u e n c y c u r v e . T h e t h r e e p l o t s o f t h e s h a l e s s h o w t h a t t h e d i s t r i b u t i o n i s a p p r o x i m i a t e l y l o g n o r m a l . A l o g n o r m a l r e l a t i o n -s h i p h a s a l s o b e e n r e p o r t e d f o r s h a l e s i n t e r b e d d e d w i t h g r a d e d b e d s b y B o k m a n (1953), N e d e r l o f (1959, i n H u b e r t , 1967), M c B r i d e (1962), S c o t t (1966), a n d H u b e r t (1967). P e t t i j o h n (1957, p . l 6 l ) - , a f t e r a c o m p r e h e n s i v e s u r v e y of. t h e t h i c k n e s s v a r i a t i o n s s h o w n b y s e d i m e n t a t i o n u n i t s o f d i f f e r e n t o r i g i n s ( e . g . ' t u r b i d i t e s , v a r v e s , l o e s s e t c . ) , s t a t e d : ' ! I t i s a p p a r e n t , t h e r e f o r e , t h a t m a n y s e d i m e n t a t i o n u n i t s o f u n l i k e o r i g i n s t e n d t o s h o w t h i c k -n e s s f l u c t u a t i o n s t h a t a r e l o g n o r m a l . \" T h e m i n e r a l o g y o f t h e c o u r s e f r a c t i o n s ( s a n d t o s i l t s i z e ) o f t h e s h a l e s h a s b e e n d e t e r m i n e d s e m i q u a n t i t a t i v e l y u n d e r t h e p e t r o g r a p h i c m i c r o s c o p e . M i c a s .are t h e m o s t a b u n d a n t c o n s t i t u e n t s , q u a r t z a n d f e l d s p a r s a r e s e c o n d i n a b u n d a n c e , a n d , i n some s a m p l e s , c h l o r i t e i s a s a b u n d a n t a s q u a r t z a n d f e l d s p a r s . P y r i t e a n d c a r b o n a c e o u s m a t t e r a r e p r e s e n t i n a l m o s t a l l s a m p l e s a n d g i v e t h e d a r k g r e y 40 c o l o r t o t h e s h a l e . F r a c t i o n s o f t h e s h a l e s f i n e r t h a n 2 m i c r o n s h a v e b e e n x - r a y e d , a n d t h e r e s u l t s s h o w t h a t i l l i t e r a n g e s f r o m 23 t o 59 p e r c e n t , k a o l i n i t e f r o m 9 t o 35 p e r c e n t , m o n t -m o r i l l o n i t e f r o m 4 t o 32 a n d c h l o r i t e f r o m 7 t o 24. T h e m e t h o d u s e d f o r d e t e r m i n i n g t h e s e p e r c e n t a g e s w a s a d o p -t e d f r o m n o t e s g i v e n i n a c l a y m i n e r a l o g y c o u r s e a t D u k e U n i v e r s i t y , N o r t h C a r o l i n a i n 1965-1966, ( s u m m a r i z e d f r o m F r e a s 1962, K u n z e 1959, W a r s h a w , R o s e n b e r g , a n d R o y i 9 6 0 , a n d W a r s h a w a n d R o y 1 9 6 l ) . T h e s e p e r c e n t a g e s w e r e o b t a i n e d b y m e a s u r i n g t h e i n t e n s i t i e s o f t h e 001 p e a k s o f t h e i l l i t e , m o n t m o r i l l o n i t e , k a o l i n i t e , a n d c h l o r i t e i n e a c h s a m p l e . T h e i n t e n s i t i e s o f t h e p e a k s w e r e o b t a i n e d b y m e a s u r i n g t h e p e a k h e i g h t a b o v e a b a s e l i n e a n d t h e p e a k w i d t h a t h a l f h e i g h t . T h e s e m e a s u r e m e n t s w e r e m u l t i -p l i e d a s f o l l o w s : (1) F o r m o n t m o r i l l o n i t e , m u l t i p l y p e a k h e i g h t b y p e a k w i d t h a t h a l f h e i g h t b y 0.71. (2) F o r c h l o r i t e a n d i l l i t e , f o l l o w s t e p o n e b u t m u l t i p l y b y 2.7. (3) F o r k a o l i n i t e , f o l l o w s t e p o n e b u t m u l t i p l y b y 1.0 . T h e s e r e s u l t s w e r e a d d e d f o r e a c h s a m p l e , a n d t h e p e r c e n t a g e o f e a c h m i n e r a l o u t o f t h e a b o v e f o u r m i n e r a l s w a s d e t e r m i n e d . . K a o l i n i t e / i l l i t e r a t i o contour map of. -the shale of the Cedar D i s t r i c t Formation.,;y:^Lfj;: 42 The x-ray diffraction data also indicate that the k a o l i n i t e / i l l i t e ratio decreases from the Dodd Narrows; Saturna Island, North Pender Island, and Mayne Island toward Vesuvius Bay on Salt Spring Island ( f i g . 1 9 ) . This ratio has been used by Parham and Austin (196?) in their study of the shales of the Glonwood Formation, South-eastern Minnesota to determine the direction of the source area which supplied the clays in this unit. Their work was based on previous work by Parham (1966) on the clay mineral assemblages in modern and ancient sediments, where he showed that \"in basins of sediment accumulation kaolinite i s concentrated closer to shore with respect to i l l i t e , and i l l i t e reaches maximum abundance seaward of kaolinite\". If the above i s true, f i g . 19 suggests that Vesuvius Bay area on Salt Spring Island was the most distant area from the paleo-shoreline relative to the other l o c a l i t i e s where k a o l i n i t e / i l l i t e ratio is higher. B. Sandstone Sandstone comprises the bulk of the non-shale portion of the Cedar Dist r i c t Formation. It has a grey to greenish color, and varies from coarse grained to very fine grained sandstone, occasionally becoming s i l t y , especially in the C-division of the turbidite units. This section of the thesis deals largely with f i e l d occurence 43 Fig..20: Shaley part of the Vesuvius Bay section just below the middle of the section. Sandstone percentage i s about 5%. Vesuvius Bay, Salt Spring Island. Fig. 21 : Turbidite sequence of alternating sandstone beds with thinner shale beds. High sandstone percentage. Vesuvius Bay-, Salt Spring Island. Fig. 22: Alternating sandstone beds with thicker shale beds. Low sandstone percentage. Bedwell Harbour, North Pender Island. Fig. 23: Thick massive sandstone bed. Note a sandstone dike injected from below the sandstone bed • and cutting through the underlying shale. Dodd Narrows, Vancouver Island. Fig, 24: Turbidite sequence of alternating shale and sandstone. Note the la t e r a l uniformity in bed thickness. Bedwell Harbour, North Pender Island. Fig. ...2 5: Turbidite bed showing repetition of i t s d i v i - -sions.. B-division (Bj at the lower half of the bed i s followed by thin G-division (C), then a second B-division (B), and the rest of the bed i s composed of C-division (C). Bedwell HarbourNorth Pender Island. u and d i s t r i b u t i o n of sandstones; discussion of sedimentary structures and detailed petrographic data are presented i n following sections. The percentage of sandstone varies both v e r t i c a l l y throughout the formation and h o r i z o n t a l l y throughout the outcrop area, • In the Vesuvius Bay section, sandstone comprises about 44% by thickness of the measured part. Within one 350 foot i n t e r v a l just below the middle of t h i s section, sandstone averages 5% ( f i g . 20); i n other i n t e r v a l s , e s p e c i a l l y the top 800 fe e t , sandstone aver-ages about 70% by thickness, with thick sandstone beds alte r n a t i n g with thinner shale beds ( f i g s . 21 and 26)., In the Bedwell Harbour section of North Pender Island, the sandstone averages 25% by thickness of the measured part,, and, as i n Vesuvius Bay section, the percentages varies v e r t i c a l l y ( f i g s . 15 and 22)* On the southern part of Saturna Island, sandstone comprises 20% by thickness of the measured part, with the basal 48 feet lacking.sand-stone beds (except f o r exotic sandstone c l a s t s ) . Along Dodd Narrows on Vancouver Island, with only the top 1010 feet of the formation exposed, sandstone forms only 5% by thickness (sandstone dikes are not con-sidered i n t h i s f i g u r e ) . There are only a few thick beds (3 to 6 feet thick) of sandstone present i n t h i s section, ) 45 t h u s t h e t y p i c a l a l t e r n a t i o n o f s a n d s t o n e a n d s h a l e b e d s p r e s e n t i n o t h e r s e c t i o n s i s n o t p r e s e n t h e r e ( f i g s . 1 4 a n d 2 3 ) . On M a y n e I s l a n d , t h e p e r c e n t a g e o f s a n d s t o n e h a s n o t b e e n m e a s u r e d , b u t t h e o u t c r o p a p p e a r a n c e i s s i m i -l a r t o t h a t o f t h e u p p e r p a r t o f t h e B e d w e l l H a r b o u r s e c t i o n o n N o r t h P e n d e r I s l a n d ( f i g . 15 ) . I n d i v i d u a l s a n d s t o n e b e d s h a v e a r e m a r k a b l y e v e n t h i c k n e s s l a t e r a l l y and. a r e c o n t i n u o u s w i t h i n t h e a r e a ' o f t h e o u t c r o p w h i c h i s u s u a l l y o f n o m o r e t h a n 300 t o 500 f e e t i n w i d t h ( f i g . 24 ) . No l a t e r a l p i n c h i n g o u t o f t h e s e b e d s h a v e b e e n o b s e r v e d , e v e n w h e n t h e y h a v e a t h i c k n e s s o f a f r a c t i o n o f a n i n c h , a l t h o u g h m a n y o f t h e m h a v e i r r e g u l a r l o w e r b e d d i n g p l a n e s d u e t o l o a d i n g a n d o t h e r s o l e m a r k s * T h e t h i c k n e s s e s o f s u c c e s s i v e b e d s s h o w a l a r g e v a r i a t i o n , f r o m t h i n s a n d s t o n e l a m i n a e w i t h i n a t h i c k s e q u e n c e o f s h a l e , t o b e d s h a v i n g t h i c k n e s s o f a b o u t 7 f e e t , t o b e d s a b o u t 9 f e e t t h i c k , t h e l a t t e r d u e t o t h e a m a l g a m a t i o n o f t w o t h i c k b e d s . B e d t h i c k n e s s c a n b e c l a s s i f i e d i n t o 3 t y p e s : (1) I n f l y s c h - l i k e s e q u e n c e s o f r h y t h m i c a l l y a l t e r -n a t i n g s h a l e a n d s a n d s t o n e b e d s , s a n d s t o n e b e d s g e n e r a l l y h a v e a n a v e r a g e t h i c k n e s s o f a b o u t 4 t o 5 i n c h e s , w i t h a r a n g e f r o m a f r a c t i o n o f a n i n c h t o a b o u t 2 f e e t ( f i g s . 5, 15, 21 , 24, a n d 25 ) . 46 (2) In some intervals of the section where sand-stone percentage i s very low and shale i s the dominating lithology, sandstone bed thickness averages about an inch, and varies from thin laminae to 5 inches (figs. 20 and 22). (3) Beds that have a range i n thickness from 2 to 7 feet are also present. They are found at the middle and top of the formation, especially at Vesuvius Bay. In the Vesuvius Bay section, of Salt Spring Island, there i s also a 330 feet interval of very thick bedded sandstone (up to 7 feet thick), which commonly shows soft sediment de-formation (figs. 26 and 27). Very thick beds of sand-stone (average of 5 feet in thickness) are also found in the Dodd Narrows section of Vancouver Island, and are usually associated with sandstone dikes ( f i g . 23)'. Regarding thicknesses of the A through E divisions within turbidite units, the cumulative frequency of the thicknesses of 163 B-divisions and 704 C-divisions from 728 turbidite units from Salt Spring and North Pender Islands sections,- grouped into one inch class interval, i s plotted on logarithmic probability paper ( f i g . 16, 17, and 18). There are also a few B-divisions reaching a thickness of a foot and a half, but they are not abundant enough to be plotted on a cumulative frequency curve. hi Distribution of the C-division i s closer to log normal than that Of the B-division. A log normal relationship of the B- and C-divisions i s reported by Hubert (1967). These sandstone beds exhibit a variety of primary sedimentary structures which are discussed in detail in a following section. C. Pebbly Mudstone on Saturna Island. The lowermost 4$ feet of the Cedar District Forma-tion on southern Saturna Island i s a chaos of clastic materials of a l l sizes and compositions embedded in a shale matrix ( f i g . 8 ) , The lower 25 feet of this interval consist of shale which contains isolated pebbles and cobbles of different shapes, varying from very angular to very well rounded. Milky quartz and basic igneous pebbles and cobbles tend to be well rounded, the angular fragments are metamorphic rocks which are commonly dark blueish-grey slates. Also scattered throughout this interval are sand and granule-size fragments of the same composition as the larger frag-ments. Sandstone clasts of varying size and shape (size varying from a sandstone lump a fraction of an inch in diameter to blocks a few feet across) are present, showing no localization to a certain horizon; they are commonly intr i c a t e l y folded, the result of soft sediment deformation, 48 a n d r e s e m b l e t h e \" t h e s l u m p o v e r f o l d s \" o f C r o w e l l (1957). A l s o p r e s e n t a r e c a l c a r e o u s c o n c r e t i o n s o f t h e s ame t y p e f o u n d i n t h e o t h e r p a r t s o f t h e f o r m a t i o n . T h e r e i s n o s i z e s o r t i n g ( f i g s . 2$ a n d 2 9 ) , a n d no i m b r i c a t e s t r u c -t u r e s , w h i c h a r e t y p i c a l o f c o n g l o m e r a t i c , d e l t a i c , f o r e -s e t b e d s , w e r e o b s e r v e d . T h e s h a l e m a t r i x s h o w s l a m i n a -t i o n a n d c o n c r e t i o n a r y w e a t h e r i n g . A t t h e same l o c a l i t y , t h e t o p 23 f e e t o f t h i s I n t e r -v a l i s m o r e s a n d y a n d f o s s i l i f e r o u s . F O S s i l s a r e b r o k e n f r a g m e n t s o f p e l e c y p o d s , g a s t r o p o d s , a n d p o s s i b l y c e p h a -l o p o d s s h e l l s . - I n t h e t o p 6 t o 8 i n c h e s , t h e s e b r o k e n s h e l l f r a g m e n t s b e c o m e c o n c e n t r a t e d t o f o r m a c o q u i n a b e d . A m i l e a n d a h a l f t o t h e n o r t h w e s t a n d a l o n g t h e s t r i k e , t h i s i n t e r v a l o f p e b b l y m u d s t o n e b e c o m e s 25 f e e t t h i c k . A c c o m p a n y i n g t h i s t h i c k n e s s d e c r e a s e i s t h e d i s -a p p e a r a n c e o f t h e a n g u l a r a n d r o u n d e d p e b b l e s a n d f o s s i l f r a g m e n t s . T h e c r i t e r i a u s e d t o c o r r e l a t e i t w i t h t h e 48 f e e t i n t e r v a l t o t h e s o u t h e a s t a r e i t s s t r a t i g r a p h i c p o s i t i o n a n d t h e p r e s e n c e o f c h a o t i c a n d f o l d e d c l a s t s o f s a n d s t o n e e m b e d d e d i n t h e s h a l e m a t r i x . T h e c o m p o s i t i o n o f t h e r o u n d e d p e b b l e s a n d c o b b l e s p r e s e n t i n t h i s i n t e r v a l i s c l o s e l y i d e n t i c a l t o t h e com-p o s i t i o n o f t h e p e b b l e s a n d c o b b l e s o f t h e d i r e c t l y u n d e r -l y i n g c o n g l o m e r a t e , e s p e c i a l l y t h e a b u n d a n c e o f m i l k y 49-quartz pebbles and cobbles ( f i g . 9). Crowell (1957) has described several sequences with characteristics very similar to those of the Saturna Island pebbly mudstone. He ascribed their emplacement to \"a downslope movement under gravity 1'. The present author-concurs with Crowell's hypothesis for the mechanism of emplacement, that i s slumping due to gravity, which resul-ted in the absence of sorting and the great contrast in size and shape of the pebbly mudstone constituents'. The following i s a model for the emplacement of the pebbly mudstone of Saturna Island, modified from Crowell (1957), Pebbles and cobbles of contrasting shape and compo-sit i o n were carried by a high density turbidity current and deposited on a sloping, muddy bottom. Some of the pebbles and cobbles sank into the underlying mud.- This loading of the mud by the coarse elastics and the occur-rence of a slope in i t i a t e d a gravity movement of the mud and overlying coarse elastics. The flow.was viscous enough to prevent any size sorting, but not viscous enough to prevent complete mixing of the different size fractions. During the course of this gravity mass movement, clasts of sandstone from the underlying sediments were peeled off, rolled up, and incorporated with the flow, and formed the folded sandstone clasts. 50 Fig. 2 6 : Thick bed of sandstone encloses a deformed thin-ly bedded sandstone clast (derived from the underlying beds?). The sandstone clast gra-des in grain size from coarser at the bottom of the hammer to finer toward the head of the hammer. Vesuvius Bay, Salt Spring Island. Fig. 2 7 : Thick bed of sandstone encloses a thinly lami-nated clast of sandstone. The sca.le i s one foot long, Vesuvius Bay, Salt Spring Island. Fig. 28: Pebbles of different shape, size, and compo-sit i o n , from the pebbly mudstone .of Saturna Island. Fig. 2 9 : : Specimen from the upper part of the pebbly mud-stone where sand percentage increases. It contains fragments of a l l sizes of organic shells (arrows). Saturna Island; Fig. 30: Turbidite bed with i t s basal A-division compo-sed of breccia. Note the sharp contact between A and B-divisions to the l e f t of the hammer head. Bedwell Harbour, N nrth Pender Island. Fig. 31: Polished specimen of the turbidite breccia of f i g . 30, Two graded cycles are present; their approximate contact i s indicated by the clashed l i n e , Bedwell Harbour, North Pender Island. 51 D. Turbidite Breccia A breccia bed with granule and pebble size clasts was found at the base of a turbidite unit (i.e. A-divi-sion) in the Bedwell Harbour section of North Pender Island, It was found to be continuous along strike within the outcrop area for a distance of about 3 0 0 to 4 0 0 feet* It i s covered with the B-division of parallel lamination, but the contact between these two divisions i s irregular ( f i g . 3 0 ) . Breccia thickness averages about 5 inches. The constituent fragments are very angular ranging in shape from equidimensional to rodlike ( f i g . 31). Color is mainly buff grey and brownish grey. The breccia clasts are composed of a great variety of rock fragments and minerals. Rock fragments, which are the dominant consti-tuent, are shale, limestone, chert, and volcanic, grani-t i c , and metamorphic rocks. Mineral identified i s quartz. Also present are fragments of organic shells. The breccia shows an overall grading in grain size from i t s bottom to i t s top, with a sudden decrease in size as the B-division of parallel lamination i s reached ( f i g . 3 0 ) , however, size grading also continues through the B-division, Within the overall grading of the breccia, at least two cycles of grading are observed ( f i g . 3 1 ) . Fragments show no preferred imbrication. 52 A p o s s i b l e mode o f e m p l a c e m e n t o f t h i s b r e c c i a , i s i t A t r a n s p o r t a t i o n a s a t r a c t i o n c a r p e t ( t r a c t i o n c a r p e t d e f i n e d b y D z u l y n s k i a n d S a n d e r s , 1962 a s : \" T h e d e n s e s a l t a t i o n z o n e .,. w h i c h i s n o t i n v a d e d b y t u r b u l e n t e d d i e s o f a n y s i z e f r o m t h e o v e r l y i n g t u r b u l e n t f l o w \" ) b e l o w a m a t u r e t u r b i d i t y c u r r e n t ; t h e l a t t e r i s d e f i n e d b y W a l k e r (1965) a s a t u r b i d i t y c u r r e n t w i t h v e r t i c a l a n d h o r i z o n t a l g r a d i n g i n g r a i n s i z e . I n t h i s t y p e o f f l o w , t h e t r a c t i o n c a r p e t c a r r i e s t h e c o a r s e r m a t e r i a l s o f t h e l o a d a n d f l o w s s l o w e r t h a n t h e o v e r l y i n g s e d i m e n t s w h i c h move a s a t u r b i d i t y c u r r e n t . C o n s e q u e n t l y , t h e f i n e r m a t e r i a l i n t h e t a i l o f t h e o v e r l y i n g t u r b i d i t y c u r r e n t w i l l e v e n t u a l l y o v e r t a k e t h e t r a c t i o n c a r p e t a n d d e p o s i t i t s l o a d o n t o p o f t h e c o a r s e s e d i m e n t o f t h e t r a c t i o n c a r p e t , p r o d u c i n g t h e s h a r p , n o n - g r a d a t i o n a l c o n t a c t b e t w e e n A- a n d B - d i v i s i o n s i l l u s t r a t e d i n f i g . 3 0 . E . C a l c a r e o u s C o n c r e t i o n s C a l c a r e o u s c o n c r e t i o n s w e r e f o u n d t o b e v e r y common t h r o u g h o u t t h e f o r m a t i o n i n a l l t h e l o c a l i t i e s s t u d i e d , e x c e p t f o r t h e b a s a l 1 1 8 f e e t e x p o s e d a t V e s u v i u s B a y . T h e y a r e n o t r e s t r i c t e d t o a s p e c i a l t y p e o f r o c k , a n d a r e f o u n d a s s o c i a t e d w i t h b o t h s a n d s t o n e a n d s h a l e ' ( f i g s . 32 a n d 3 3 ) . T h e i r l o n g e s t d i m e n s i o n r a n g e s f r o m a f e w i n c h e s t o s e v e r a l f e e t , a n d o c c a s i o n a l l y t h e y f o r m a 53 Fig. 32: Calcareous concretions (outlined by dashed lines) enclosed in a sandstone bed. Note thickening of the sandstone bed around the concretions. Vesuvius Bay, Salt Spring Island. Fig. 33: Calcareous concretion embedded in shale. 0 n e foot scale. Vesuvius Bay, Salt Spring Island. Fig. 34: Calcareous concretion with a thin very fine-grained sandstone bed crossing i t (sandstone bed indicated by arrows). Scale i s one foot long. Vesuvius Bay, Salt Spring Island. Fig. 35: • Calcareous concretions joined to form a discon-tinuous bed. Bedwell Harbour, North Pender Island. Fig. 36: • Calcareous concretion with i t s long dimension cutting shale lamination. Note organic borings (indicated by arrows). Vesuvius Bay, Salt Spring Island. Fig. 37: Calcareous concretion enclosing a bivalved she l l . Pencil points to a broken shell fragment.- Vesuvius Bay, Salt Spring Island. 54 d i s c o n t i n u o u s bed o f j o i n e d c o n c r e t i o n s ( f i g s . 33 , 34, and 3 5 ) . They e x h i b i t a wide range of shapes, from b i c o n v e x d i s c - s h a p e d , to g l o b u l a r , t o t u b e - l i k e ' ; o t h e r s a r e l e n s -shaped as seen i n t h e o u t c r o p i n two dimen s i o n s ( f i g s . 33, 34, and 3 6 ) . They have two modes o f o c c u r r e n c e r e l a t i v e t o t h e s u r r o u n d i n g beds. The f i r s t and most common i s t h e type whose l o n g d i m e n s i o n s a r e always p a r a l l e l and concordant t o t h e s u r r o u n d i n g b e d d i n g o r l a m i n a t i o n ( f i g s . 32>, 33 , 34j and 3 5 ) . The second i s t h e ty p e t h a t has a random o r i e n t a t i o n o f t h e l o n g d i m e n s i o n s , c u t t i n g t h r o u g h and . d i s t u r b i n g the s u r r o u n d i n g b e d d i n g and l a m i n a t i o n (fig.3 6 ) * B o t h t y p e s c o n t a i n a n i m a l burrows o r b o r i n g s t h a t a re f i l l e d w i t h sand and s i l t o f t h e e n c l o s i n g beds, s u g g e s t -i n g b u r r o w i n g t o o k p l a c e w h i l e the c o n c r e t i o n s and t h e s u r r o u n d i n g sediments were s o f t ; a l t e r n a t i v e l y , t h e s e might be b o r i n g s i n t o an a l r e a d y l i t h i f i e d c o n c r e t i o n l y i n g on or near the sea f l o o r . I n e i t h e r c a s e , t h i s . o b s e r -v a t i o n and o t h e r e v i d e n c e s mentioned beloxv i n d i c a t e e a r l y d i a g e n e t i c f o r m a t i o n o f the' c o n c r e t i o n s . Some o f t h e con-c r e t i o n s c o n t a i n s h e l l s o f b i v a l v e d i n v e r t e b r a t e s ( p o s s i b l y Inoc.eramus). ( f i g . 3 7 ) , o t h e r s have t a b u l a r s h e l l s ( p o s s i b l y ammonites), and some o t h e r s c o n t a i n f r a g -ments o f br o k e n s h e l l s . They f r e q u e n t l y c o n t a i n laminae 55 Fig. 38: Fig. 3 9 : Fig. 4 0 : Fig. 41: Fig. 42 Photomicrographs of Calcareous Concretions (Sample numbers at end of captions) Fossil foraminifers(?) in calcareous concre-tion, f i l l e d with pyrite (black) and sparry calcite (white). Crossed nicols. Vesuvius Bay, Salt Spring Island. (V12). Detrital grains of quartz, feldspar, mica, and clay minerals, in a calcareous concre-tion. Crossed nieals. Vesuvius Bay, Salt Spring Island. (V21). Planktonic foraminifer (?) (in the center) surrounded by other f o s s i l foraminifers(?). The matrix (or cement) i s composed of fine-grained (micritic) calcite. Crossed nicols. Vesuvius Bay, Salt Spring Island. (Vl6). Phosphatic pellets (indicated by arrows) in calcareous concretion. The matrix i s com-posed mainly of micritic calcite and detri-t a l quartz and feldspar. Note how the pel-lets are bent around a foraminifer (?) test, Plane polarized l i g h t . Vesuvius Bay, Salt Spring Island. (V21). Photomicrograph to show, in de t a i l , part of one of the phosphatic pellets in f i g . 4 1 . White grain in the center i s quartz. Dark grains are phosphatic materials, the light grains are clay minerals. Crossed nicols. Vesuvius Bay, Salt Spring Island (V2l). 56 which continue into the surrounding shale or sandstone; these iaminae exhibiting the same sedimentary structures as in the surrounding rocks ( f i g . 3 4 ) . The concretions are grey in color and are composed mostly of calcite with some clay minerals and pyrite ( f i g . 33 ) . When crossed or surrounded by s i l t y shale or sand-stone beds, they usually have a high percentage of the same d e t r i t a l quartz, feldspar, and other minerals that constitute the surrounding rocks ( f i g . 3 9 ) . They common-ly contain circular and e l l i p t i c a l tests of microfossils (possibly foraminifers) which arc usually f i l l e d with sparry calcite, and occasionally by pyrite (figs. 3$ and 40). Phosphatic pellets v/ere observed in two concretions. They are globular to elongate and have a size range from 5 to 2. mm (f i g . 4 1 ) . Their colour i s light brown under polarized l i g h t , and greenish brown under crossed nicols. Phosphatic material i s also found disseminated throughout the concretions around the pellets. Detrital quartz, feldspars, and clay minerals within the concretions are also found enclosed in the pellets mixed with the phospha.-t i c material ( f i g . 4 2 ) . In concretions that have been intersected by s i l t y or sandy laminae, the pellets are confined to the very fine grained calcite-rich parts of 57 F i g . 43: E l e c t r o n micrograph of a calcareous c o n c r e t i o n . M i n e r a l s w i t h high r e l i e f are d e t r i t i a l quartz, s i l i c a t e m i n e r a l s , or rock fragments. Rodlike grains are probably micaceous miner-a l s . The l o w - r e l i e f grains are c a l c i t e matrix (or cement). Black g r a i n s are possib-l y i l l i t e . . Note replacement of the d e t r i t a l grains by the c a l c i t e cement along t h e i r i r -r e g u l a r boundaries. Bedwell Harbour, North Pender I s l a n d . ( P 3 1 ) . F i g , 44: • E l e c t r o n micrograph showing d e t r i t a l grains embedded i n c a l c i t e cement of v a r i a b l e g r a i n s i z e and shape. Vesuvius Bay, S a l t Spring I s l a n d . (VSE7). 56* t h e c o n c r e t i o n . I n o n e t h i n s e c t i o n , a p e l l e t w a s o b -s e r v e d t o b e b e n t a r o u n d a f o r a r a i n i f e r t e s t ( f i g . 41), s u g g e s t i n g t h a t t h i s p e l l e t s e t t l e d o n t h e t e s t w h i l e t h e f o r m e r w a s s o f t . S t u d y o f e l e c t r o n m i c r o g r a p h s o f t h e c a l c a r e o u s c o n -c r e t i o n s r e v e a l s some i n f o r m a t i o n r e g a r d i n g t h e d e t a i l e d t e x t u r e s o f t h e c a l c i t e c e m e n t a n d t h e e n c l o s e d d e t r i t a l g r a i n s . T h e d e t r i t a l g r a i n s ( q u a r t z , s i l i c a t e m i n e r a l s , o r r o c k f r a g m e n t s ) s t a n d u p w i t h h i g h e r r e l i e f t h a n t h e s u r r o u n d i n g c a l c i t e c e m e n t ( f i g s . 43 a n d 44), b e c a u s e t h e y a r e l e s s a f f e c t e d b y t h e a c i d e t c h i n g d u r i n g p r e p a r a t i o n o f t h e r e p l i c a . T h e d e t r i t a l g r a i n s c o m m o n l y a r e p a r t i a l -l y r e p l a c e d a l o n g t h e i r b o u n d a r i e s b y t h e c a l c i t e c e m e n t ( f i g s . 43 a n d 44) > I n some g r a i n s t h e r e p l a c e m e n t i s c o n -f i n e d t o o n l y a p a r t o f t h e g r a i n b o u n d a r y ( f i g . 43). G r a i n b o u n d a r i e s s h o w i n g r e p l a c e m e n t a r e g e n e r a l l y h i g h l y i r r e g u l a r a n d s h o w i n t e r l o c k i n g o f t h e c a l c i t e c e m e n t w i t h t h e d e t r i t a l g r a i n s . T h e c e m e n t i s c o m p o s e d o f c a l c i t e g r a i n s o f i r r e g u l a r a n d v a r i a b l e s h a p e s w i t h t h e i r b o u n d a r i e s h i g h l y e m b a y e d . T h e s i z e i s v a r i a b l e a n d r a n g e s f r o m a b o u t 0,1 m i c r o r t t o ' a b o u t 9.0 m i c r o n s ( f i g s . 43, 44 a n d 45). T h e s u r f a c e - o f t h c a l c i t e g r a i n s a p p e a r q u i t e h u m m o c k y a n d i r r e g u l a r w i t h n u m e r o u s s m a l l i n c l u s i o n s . 59 Fig.. 45: F i g . 46: F i g / 47: E l e c t r o n m i c r o g r a p h showing b r a n c h i n g r o d -l i k e g r a i n s w i t h c a l c i t e g r a i n s (low r e l i e f g r a i n s ) between them. V e s u v i u s Bay, S a l t S p r i n g I s l a n d . (VSE7). Deformed c a l c a r e o u s c o n c r e t i o n ( i n d i c a t e d by arrows) e n c l o s e d i n a sandstone bed t h a t un-derwent s o f t - s e d i m e n t d e f o r m a t i o n . V e s u v i u s Bay-, S a l t S p r i n g I s l a n d , A - d i v i s i o n (A) grades g r a d u a l l y upward, i n t o B - d i v i e i o n ( B ) . The d a r k r i n d i s caused by seepage of sea w a t e r i n t o t h e sandstone a l o n g f r a c t u r e s . V e s u v i u s Bay, S a l t S p r i n g I s l a n d i 66 The b l a c k g r a i n s ( f i g s . 43 , 44, and 45) are p r o b a b l y e x t r a c t e d c l a y m i n e r a l s and have shapes somewhat s i m i l a r t o what Grim (1953, p.120 and 121) has i d e n t i f i e d as i l l i t e . The r o d - l i k e g r a i n s t h a t s t a n d up w i t h h i g h r e l i e f r e l a t i v e t o the s u r r o u n d i n g c a l c i t e cement ( f i g s . 43 , 44, and e s p e c i a l l y 45) a r e perhaps s e c t i o n s o f micaceous mine-r a l s c u t p e r p e n d i c u l a r t o t h e 001 p l a n e . I n f i g . 45 t h e s e g r a i n s a r e connected i n a manner w h i c h s u g g e s t s f o r c e f u l s e p a r a t i o n a l o n g 001 c l e a v a g e p l a n e s by c r y s t a l l i z a t i o n o f c a l c i t e between t h e s e p l a n e s d u r i n g d i a g e n e s i s , ( R. E . G a r r i s o n , 196$, p e r s o n a l c ommunication). R e g a r d i n g the g e n e s i s o f t h e c a l c a r e o u s c o n c r e t i o n s , the a u t h o r s u g g e s t s an e a r l y d i a g e n e t i c o r i g i n ( v e r y e a r l y b u r i a l s t a g e ) d u r i n g w h i c h , c a r b o n a t e s p r e c i p i t a t e d from i n t e r s t i t i a l s o l u t i o n s , a r e l o c a l i z e d around a n u c l e u s (e.g. o r g a n i c s h e l l s o r d e t r i t a l g r a i n s ) t h a t may o r may not l e a v e a r e l i c ( f i g s . 33 and 3 7 ) . D u r i n g t h i s p r e c i p i -t a t i o n t h e r e was a p p a r e n t l y e x t e n s i v e replacement o f d e t r i t a l g r a i n s by sec o n d a r y c a l c i t e . Some o f th e s e con-c r e t i o n s a r e found w i t h i n sandstone beds ( f i g . 3 2 ) ; the bed t e n d s t o be t h i c k e r around them s u g g e s t i n g t h a t t h e c o n c r e t i o n and the e n c l o s i n g sandstone hardened e a r l i e r t h a n t h e s u r r o u n d i n g s a n d s tone, t h e r e f o r e escaped s t r o n g c o m p a c t i o n . I n summary, t h e f o l l o w i n g c r i t e r i a suggest 61 an early diagenetic origin for these concretions: 1. Organic borings and burrows f i l l e d with sediment of the surrounding beds. 2. Thickening of beds where concretions occur. 3. Their deformation when present in beds showing soft sediment deformation, ( f i g . 46). 4. Undeformed r e l i c s (bivalvecl shells) enclosed in the concretions ( f i g . 37)• G. Mill Ier (1967, p. 154), in a discussion of the car-bonate contretions enclosed in mudstones and shales poor in carbonates, stated \"It seems probable that most of the concretions started to form i n the shallow burial (and early) stage of diagenesis, because the enveloped r e l i c s of organisms are commonly not deformed.\" Lippmann (1955, in G. Mttller 1967, p. 154) explained the genesis of calcareous concretions as follows: \"Ammonia resulting from the decomposition of organisms or amines gives rise to a strongly alkaline reaction in the v i c i n i t y of the animal (or plant) embedded in the sedi-ment, and the pH i s increased. As the s o l u b i l i t y of the carbonates decreases with increasing pH, they are preci-pitated on the f o s s i l from the i n t e r s t i t i a l solutions, which have been saturated with carbonates by dissolving the disseminated calcareous material (also present in 62 predominantly a rg i l l aceous sediments). Thus here the car -bonate concentrat ion of the pore so lu t ion decreases in comparison to the surrounding environment, and because of the d i f ference in concentrat ion, more carbonate i s con-s tan t ly d i f fused to the f o s s i l . This process, accompanied by a constant growth of the concret ion , continues u n t i l the production of ammonia stops, or u n t i l there are no more d isso lved carbonates a v a i l a b l e i n the v i c i n i t y . , \" The pyr i te present in these concretions and the host rocks , i s probably the r e s u l t of the reducing condit ions prevalent in the v i c i n i t y of the decomposing organisms. The s i g n i f i c a n c e of the rare phosphatic mater ia l noted above i s not known. The author has not observed i t to be associated with other types of rocks i n the formation.' Phosphatic mater ia l i n sediments i s t y p i c a l l y a product of slow deposi t ion or non-deposi t ion; i t s assoc ia t ion with the calcareous concret ions may ind ica te the l a t t e r formed during i n t e r v a l s of reduced sedimentation r a t e s . 6 . SEDIMENTATY STRUCTURES The sandstones and shales of the Cedar D i s t r i c t Forma-t i o n exhibi t a wide range of sedimentary s t ruc tures . They range from primary st ructures formed e i ther by the f i l l i n g 63 o f m a r k s made b y a n e r o s i v e c u r r e n t o n a m u d d y b o t t o m ( e . g . d i f f e r e n t k i n d s o f s o l e m a r k s ) , a n d / o r d u r i n g t h e s e t t l i n g o f t h e s e d i m e n t s o u t o f t h e t r a n s p o r t i n g c u r r e n t ( e . g . g r a d e d b e d s , ' p a r a l l e l l a m i n a t i o n , \" c u r r e n t r i p p l e l a m i n a t i o n , e t c . - ' ) ; t o s t r u c t u r e s f o r m e d a f t e r d e p o s i t i o n a n d b e f o r e b u r i a l clue e i t h e r t o g r a v i t a t i o n a l m o v e m e n t s ( e . g . s l u m p s t r u c t u r e s ) , o r d r a g b y s e d i m e n t l o a d e d c u r -r e n t s f l o w i n g o v e r s o f t s e d i m e n t s ( e . g . d e f o r m a t i o n a l s t r u c t u r e s r e s u l t i n g f r o m h i g h d e n s i t y t u r b i d i t y c u r r e n t s ) ; t o s t r u c t u r e s d u e t o f o r c e f u l i n j e c t i o n o f s o f t s e d i m e n t s t h r o u g h f i s s u r e s ( e . g . c l a s t i c d i k e s ) . A. I n t e r n a l S t r u c t u r e s W i t h i n T u r b i d i t e . U n i t s W i t h i n i n d i v i d u a l t u r b i d i t e u n i t s , a l i m i t e d n u m b e r o f s e d i m e n t a r y s t r u c t u r e s h a v e b e e n o b s e r v e d . T h e s e s t r u c t u r e s t e n d t o e x i s t a l w a y s i n a f i x e d o r d e r o r s u c -c e s s i o n ( e x c e p t f o r o c c a s i o n a l r e p e t i t i o n o f a c e r t a i n s t r u c t u r e w i t h i n t h e same t u r b i d i t e u n i t , f i g . 25) w i t h i n t h e u n i t f r o m i t s b o t t o m t o t o p . T e r m i n o l o g y o f t h e d i f -f e r e n t s t r u c t u r e s h a s b e e n d i s c u s s e d e a r l i e r i n t h i s p a p e r . Some o f t h e t u r b i d i t e u n i t s s h o w a l l t h e p o s s i b l e s t r u c t u r e s ( d i v i s i o n s ) , b u t t h e m a j o r i t y t e n d t o l a c k o n e o r m o r e o f t h e m . T h e s e s t r u c t u r e s h a v e b e e n d e s c r i b e d i n d i f f e r e n t p a r t s o f t h e w o r l d , a n d i n s e d i m e n t s r a n g i n g i n a g e f r o m 64 the P r e c a m b r i a n to present (see PH. H. Kuc-nen and F . L . Humbert b i b l i o g r a p h y , 1964; the reader may a l s o r e f e r to K»0. Emery, 1964 f o r d i s c u s s i o n of t u r b i d i t e s from P r e -cambrian t o p r e s e n t ) . Walker (1965) has a t t r i b u t e d the v a r i a t i o n i n the nature of the graded d i v i s i o n (e.g. w e l l d e f i n e d or crude g r a d i n g i n A - d i v i s i o n ) to the type of t u r b i d i t y c u r r e n t from which g r a d i n g has formed. He a l s o r e l a t e s the v a r i a -t i o n i n the nature of the o t h e r d i v i s i o n s ( e . g . v a r i a t i o n i n types of c u r r e n t r i p p l e l a m i n a t i o n i n C - d i v i s i o n ) to the hydrodynamic c o n d i t i o n s of the c u r r e n t . He has (Walker, 1967) i n t e r p r e t e d the hydrodynamics o f the d i f -f e r e n t d i v i s i o n s by analogy w i t h the f low regimes of Simons and others ,(1965)* In h i s view* the A- and B-d i v i s i o n s were formed w i t h i n the Upper f i o w regimej the C - , D--, and E - d i v i s i o h s w i t h i n the lower f l o w regime. a . Graded D i v i s i o n ( A - d i v i s i o n ) Out o f the i n d i v i d u a l 746 t u r b i d i t e u n i t s measured i n the upper 1$5 f e e t and the lower 118 f e e t of the Vesu-v i u s Bay s e c t i o n of S a l t S p r i n g I s l a n d , and the upper 174 f e e t of the Bedwel l Harbour s e c t i o n of Pender I s l a n d , o n l y 20 graded d i v i s i o n s were r e c o r d e d . A d d i t i o n a l u n i t s , w i t h A - d i v i s i o n occur i n o ther p a r t s of the s e c t i o n s where s y s -temat ic measurements of the d i f f e r e n t d i v i s i o n s were not 65 Fig. 48: Fig. 49: Fig. 50: Fig. 51: Fig. 52 Fig. 53: Massive A-division (bottom of the pencil) lies below laminated B-division with a sharp con-tact. Vesuvius Bay, Salt Spring Island. Thick, f a i n t l y laminated, graded sandstone bed. with i t s sole showing flute casts (a), bounce casts (b), and fine, closely spaced groove casts (c). Current from l e f t to right. Bedwell Harbour, North Pender Island. Plane-parallel lamination (B-division) caused by alternating dark, thin, fine-grained and li g h t , thick, coarse-grained sand laminae. The top i inch shows cross lamination (C-division). Note organic reworking. Bedwell Harbour, North Pender Island. Climbing ripple laminae of McKee (1965), (C-division). Vesuvius Bay, Salt Spring Island, Upper bedding plane of sandstone bed showing sli g h t l y asymetrical branching ripple marks. Mayne Island. Two superimposed C-division. Note the' differ-ence i n thickness and types of structures between the lower thin, and the upper thicker • C-divisions. Vesuvius Bay, Salt Spring Island, 66 made;\" thes e a re m a i n l y v e r y t h i c k beds (average t h i c k n e s s about 3 t o 4 f e e t ) w i t h crude g r a d i n g , and u s u a l l y c o n t a i n l a r g e c l a s t s o f deformed s h a l e and sandstone ( f i g . 26 and 27).- Other t h a n t h e s e v e r y t h i c k , graded beds, two t y p e s o f g r a d i n g have been o b s e r v e d : (1) A - d i v i s i o n grades upward g r a d u a l l y w i t h o u t a sharp c o n t a c t i n t o t h e o v e r l y i n g B - d i v i s i o n ( f i g . . 4 7 ) . ( 2 ) A - d i v i s i o n l i e s below B - d i v i s i o n w i t h a sharp w e l l d e f i n e d c o n t a c t ( f i g . 4$) . I n b o t h c a s e s , t h e A-»division has a sharp lower con-t a c t w i t h the u n d e r l y i n g D E - d i v i s i o n . W a lker (1965, p. 13) suggested p o s s i b l e mechanisms t o e x p l a i n t h e s e two t y p e s of g r a d i n g . The f i r s t t y p e , he s u g g e s t s , has been formed by the r e w o r k i n g o f the upper p a r t o f a p r e - e x i 5 t i n g A - d i v i s i o n . T h i s r e w o r k i n g , r e s u l -t e d i n t h e f o r m a t i o n o f a p l a n e - p a r a l l e l d i v i s i o n (B-d i v i s i o n ) a t the top o f A - d i v i s i o n , The second t y p e o f g r a d i n g i n h i s view has been formed by p r i m a r y d e p o s i t i o n o f A- and B - d l v i s i o n s from t h e t u r b i d i t y c u r r e n t , w i t h no r e w o r k i n g . I n b o t h c a s e s , the t u r b i d i t y c u r r e n t r e s p o n s i -b l e f o r t h e i r f o r m a t i o n has no t r a c t i o n c a r p e t . F o r t h i c k graded beds ( f i g . 49), where t h e r e i s f a i n t l a m i n a t i o n w i t h i n the A - d i v i s i o n , Walker (1965, p.11) has p o s t u l a t e d d e p o s i t i o n from t u r b i d i t y c u r r e n t w i t h a t r a c -t i o n c a r p e t . I n h i s o p i n i o n t h e shear a p p l i e d by t h e 67 c u r r e n t i s t o o l o w t o m a i n t a i n c o n t i n u o u s m o t i o n w i t h i n t h e c o a r s e s e d i m e n t s a t t h e b o t t o m o f t h e c u r r e n t . b . L o w e r D i v i s i o n o f P l a n e - P a r a l l e l L a m i n a t i o n ( B - d i v i s i o n ) T h i s d i v i s i o n a l w a y s o v e r l i e s t h e A - d i v i s i o n w h e n t h e . l a t t e r i s p r e s e n t . L a m i n a t i o n i s c a u s e d b y t h e a l t e r n a -t i o n o f c o a r s e - g r a i n e d , t h i c k , l i g h t c o l o r e d l a m i n a e a n d f i n e - g r a i n e d , t h i n , d a r k c o l o r e d l a m i n a e c o n t a i n i n g b i o -t i t e ( f i g . 50 ) . T h i s k i n d o f l a m i n a t i o n w a s a l s o r e p o r t e d b y B o uma (1962, p . 6 3 ) , a n d S a n d e r s (1965, p . 199) . O c c a s i o n a l l y t h e s i z e o f t h e c o a r s e f r a c t i o n a t t h e b a s e o f t h i s d i v i s i o n i s l a r g e r t h a n t h e s i z e o f t h e c o a r s e f r a c t i o n a t i t s t o p , i n d i c a t i n g some d e g r e e o f s i z e g r a -d i n g . Some u n i t s s h o w p a r t i n g l i n e a t i o n a l o n g l a m i n a t i o n p l a n e s w i t h i n t h i s d i v i s i o n u p o n s p l i t i n g . ' ' 166 B - d i v i s i o n s w e r e r e c o r d e d i n t h e 746 t u r b i d i t e u n i t s m e a s u r e d o n S a l t S p r i n g I s l a n d a n d N o r t h P e n d e r I s l a n d . O n l y a f e w (20) o f t h e 166 B - d i v i s i o n s a r e u n d e r -l a i n b y A - d i v i s i o n . T h e r e s t (146) f o r m t h e b a s e o f 146 t u r b i d i t e u n i t s ( i . e . a b o u t 20$ o f t h e 746 t u r b i d i t e u n i t s h a v e B - d i v i s i o n s a t t h e i r b a s e ) . T h e y l i e w i t h a s h a r p , a l m o s t p l a n a r l o w e r c o n t a c t o v e r t h e u n d e r l y i n g DE-d i v i s i o n ( w h e n A - d i v i s i o n i s a b s e n t ; f i g . 25 ) . K u e n e n (1953, p . 1049) a n d S a n d e r s (1965, p . 199) 68 suggested that par a l l e l lamination was formed by the fluc-tuation or pulsation of the current velocity. Walker (196$, p. 13) thought they were formed i n the \"plane bed with movement\" part of the current regime of Simons et al. (1961), either by primary deposition from the current ( f i g . 48), or by reworking of previously deposited sedi-ments ( f i g . 47). c. Division of Current Ripple and Parallel Lamination (C-division) This division i s very abundant i n the turbidite units of the Cedar Dist r i c t Formation. It was recorded in 707 out of the 746 turbidite units measured, and forms the basal part of 77$ of the measured turbidite units (i.e. 77$ of the units start with the C-division at their base). Thickness of this division varies from a fraction of an inch to 10 inches, averaging about an inch and a half. Figures 16, 17, and 18 show the cumulative frequency of the thicknesses of 707 C-divisions measured in the Vesu-vius Bay section of Salt Spring Island, and the Bedwell Harbour section of North Pender Island. The three lines approach log normal distribution, with a marked deviation at the 5-7 inch interval i n the North Pender section (fig. 18), indicating thet C-divisions with this thickness range are rare. 69 G r a i n s c o m p r i s i n g the sediments o f t h i s d i v i s i o n a re t • \" . m o s t l y i n t h e c o a r s e s i l t t o the v e r y f i n e sand c l a s s e s , and show a crude g r a d i n g from c o a r s e a t the base o f the d i v i s i o n t o f i n e a t i t s t o p . S t r u c t u r e s observed i n t h i s d i v i s i o n i n c l u d e : (1) C u r r e n t r i p p l e s and t h e i r a s s o c i a t e d c r o s s l a m i -n a t i o n . ( 2 ) C o n v o l u t e l a m i n a t i o n . Most o f the C - d i v i s i o n s e x h i b i t e i t h e r one o f the above s t r u c t u r e s , but some of them have b o t h s t r u c t u r e s a s s o c i a t e d t o g e t h e r * Almost a l l t h e c r o s s l a m i n a t i o n found ,in t h i s d i v i -s i o n i s o f the t y p e c a l l e d by McKee ( 1 9 6 5 , p« 7 6 , f i g s . 4c and d) \"pseudobeds\"± o f b o t h h i g h and low a n g l e . T h i s k i n d o f c r o s s l a m i n a t i o n has r e s u l t e d from t h e m i g r a t i o n o f the r i p p l e s accompanied by d e p o s i t i o n o f sediments from above, r e s u l t i n g i n what i s c a l l e d by McKee -(1965) \" c l i m b i n g r i p p l e l a m i n a e \" , ( f i g . 5 1 ) . Only one t h i n bed, w h i c h c o n s i s t s e n t i r e l y o f C - d i v i s i o n , shows r i p p l i n g i n t h r e e d i m e n s i o n s ( f i g . 5 2 ) . These c u r r e n t r i p p l e s range i n w a v e l e n g t h from two i n c h e s t o about a f o o t , t h e i r a m p l i t u d e ranges f r o m a f r a c t i o n o f an i n c h t o about two i n c h e s . They o c c u r e i t h e r i n a s i n g l e s e t f o r m i n g a t h i n C - d i v i s i o n ( f i g . 53, l o w e r C - d i v i s i o n ) and u s u a l l y form s i n g l e s e t s o f c r o s s 70-l a m i n a t i o n \"suggesting no f a l l - o u t of sediments during r i p p l i n g \" , (Walker, 196$, p.15). They may a l s o occur i n s e v e r a l sets on top of each other ( F i g . 53, upper C - d i v i -s i o n ) , or i n the form of c l i m b i n g sets of r i p p l e d r i f t cross l a m i n a t i o n ; the l a t t e r \"suggests a f a l l out of sediments during or immediately a f t e r the i n i t i a l forma-t i o n of r i p p l e s \" , (Walker, 1 9 6 5 , p.15), ( f i g * 51). The l a s t two forms tend to make a r e l a t i v e l y t h i c k C - d i v i s i o n * Convolute lam i n a t i o n may a l s o occur i n one or more s e t s . In cases where r i p p l e and convolute l a m i n a t i o n both occur i n the same d i v i s i o n , there i s a c o n s i s t e n t v e r t i -c a l arrangement of these s t r u c t u r e s . The C - d i v i s i o n s t a r t s w i t h very broad r i p p l i n g at the bottom which grades upward i n t o narrower r i p p l e s w i t h greater amplitude, and, at the top of the d i v i s i o n , the r i p p l e s tend to show con v o l u t i o n , (fig.- 53, upper C - d i v i s i o n ; and f i g ; 54). In a d d i t i o n to t h i s v e r t i c a l sequence, i t was a l s o observed t h a t one s t r u c t u r e could grade h o r i z o n t a l l y along the s t r i k e of the bed i n t o another s t r u c t u r e (e.g. current r i p p l e l a m i n a t i o n may grade l a t e r a l l y to convo-l u t e d lamination) . Walker,(1965, p.12) suggested that convoluted l a m i n a t i o n forms i n cohesive bottom sediments; when the sediments l a c k such cohesiveness, current r i p p l e l a m i n a t i o n w i l l be formed. I f t h i s i s the case, the 71 G r a d i n g o f s t r u c t u r e s f r o m p l a n e - p a r a l l e l l a m i -n a t i o n w i t h s m a l l a m p l i t u d e , t o r i p p l e l a m i -n a t i o n w i t h l a r g e r a m p l i t u d e s h o w i n g s l i g h t c o n v o l u t i o n t h a t h a s b e e n r e w o r k e d b y o r g a -n i s m s . B e d w e l l H a r b o u r , N o r t h P e n d e r I s l a n d . T h e u p p e r h a l f o f t h e s p e c i m e n c o n t a i n s c o n v o -l u t e l a m i n a t i o n . L a m i n a e i n v o l v e d i n t h e l o -w e r \\ i n c h o f t h e c o n v o l u t i o n a r e p a r a l l e l t o e a c h O t h e r , b u t a b o v e t h i s t h e l a m i n a e s h o w c r o s s l a m i n a t i o n , V e s u v i u s Bay., S a l t S p r i n g I s l a n d . C o n v o l u t e l a m i n a t i o n o n a b e d d i n g p l a n e . T h e p e n c i l l i e s o n t h e u p p e r b e d d i n g p l a n e s u r -f a c e o f a s a n d s t o n e b e d t h a t d i p s s t e e p l y t o -w a r d t h e b o t t o m o f t h e p h o t o g r a p h . N o t e s i m i -l a r i t y o f c o n v o l u t e l a m i n a t i o n t o l i n g u o i d r i p p l e s , V e s u v i u s B a y , S a l t S p r i n g I s l a n d . O r g a n i c . . b o r i n g s i n s h a l e a t h i g h a n g l e t o t h e l a m i n a t i o n . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . O r g a n i c b o r i n g s o n t h e s o l e o f a s a n d s t o n e b e d o b l i t e r a t e q u e s t i o n a b l e l o a d e d f l u t e c a s t s ( a ) . N o t e a n a r r o w g r o o v e c a s t ( i n d i c a t e d b y a r r o w s ) . C u r r e n t d i r e c t i o n f r o m l o w e r r i g h t t o u p p e r l e f t a s i n d i c a t e d b y t h e f l u t e a n d g r o o v e c a s t s . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . L o a d e d f l u t e c a s t ( a ) a n d a w i d e g r o o v e c a s t ( b ) . C u r r e n t d i r e c t i o n i s f r o m l o w e r r i g h t t o u p p e r l e f t . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . 72 presence of convoluted and current ripple lamination in the same bed suggests either: (1) the cohesiveness of the grains of the bottom sedi-ments was not uniform during their deposition, resulting in the formation of both current ripple and convoluted l a -mination; or (2) that current ripple lamination formed f i r s t in cohesionless sediments, then local l y the cohesion increased, and the overlying current deformed the ripple lamination convolute into/1 lamination (this phenomenon of increase in cohesion was called the \"Hjulstrbm effect\" by Sanders (1963, p.178). Both assumptious seem valid, since i t was observed that there are two types of convolute lamination present. The f i r s t type, i n which the convoluted laminae are parallel to each other ( f i g . 5 5 , the laminae of the basal g inch of convolute lamination are par a l l e l to each other), ind-?->-tes that these laminae were originally plane parallel and not current ripple laminae, and were deformed due to the shear applied by the overpassing current on cohesive sedi-ments. In the second type, convolution was developed after rippling since ripple cross lamination i s s t i l l pre-served in the convolute lamination ( f i g . 5 4 ) • Convolute lamination could not be observed in three dimensions, except for one bed where the upper bedding 7 3 plane i s exposed ( f i g . 5 6 ) . From this picture it, seems that the original structure before convolution was a be:l of linguoid ripples* Regarding the origin cf convolute lamination, Keener ( 1 9 5 3 , p. 1057; attributed their formation to \" i n t e n s i f i -cation of ripple mark by hydrodynamic pressure combined with loading in the troughs'1: Ten Raaf ( 1956, in McBride 1 9 6 2 , p. 52) modified this mechanism slig h t l y and proposed , ;that the action of accelerated deposition in troughs o i 1 probable incipient ripple marks combined with the expul-sion of water through the crests was the cause\". Sanders (1963 and 1965) and Walker ( 1 9 6 5 ) , pointed out the impor-tance of cohesiveness of the bottom sediments in their formation. Other workers feel they may be post-depositio-nal, deformational structures, formed by \"Lateral intra-stratal flow of l i q u i f i e d beds\" (Williams, I960), cr b y \"creep when sedimentation took place on a slope.'' (Holland, 1 9 5 9 ) . d. Interturbidite Division (DE-division) Because i t was d i f f i c u l t to differentiate between the upper division of plane-parallel lamination (D-divi-sion), and the p e l i t i c division (E-division) in the f i e l d , the author has called the laminated shale overlying the sandy part of the turbidite unit the \"interturbidite Ik division\" (Walker,, 1967) , (figs. 5, 15, and 3 6 ) . But the reader should not think of them as entirely non-turbidite in origin, since they show some grading from s i l t to clay size, suggesting deposition from a current suspended load (Sanders 196$, and Walker, 196$) . The main structure i n this division i s plane-parallel domination. This lamination was believed by Walker (1965, p. 19) to be formed by the alternation of coarse-grained and finer-grained laminae. ' Occasional laminae of light colored, very fine-grained sandstone were found to con-tain foreset lamination. This division varies in thickness from a fraction of an inch to 33 inches and averages about 2.$ inches. : Figures 16,. 17, and 18 show the cumulative frequency of the thicknesses of 727 interturbidite divisions measured in Vesuvius Bay section of Salt Spring Island, and the Bedwell Harbour section of North Pender Island. These also show log normal distribution. The shale of this division contains accasional animal burrows, oriented in various directions. Some are paral-l e l to the bedding, others are inclined at different angles to the bedding plane,, (figs. 36 and $7 ) . 75 B. S o l e M a r k s . T h e s e a r e m a r k s p r e s e n t o n t h e b o t t o m s i d e o f s a n d -s t o n e a n d s i l t s t o n e b e d s . M a n y o f t h e m h a v e b e e n u s e d -f o r d e t e r m i n i n g d i r e c t i o n s o f p a l e o c u r r e n t s s i n c e t h e y h a v e b e e n f o r m e d a s f i l l i n g s o f d e p r e s s i o n s c a u s e d b y t h e d r a g a n d s c o u r i n g o f c u r r e n t s a n d t h e i r l o a d s a l o n g a m u d d y b o t t o m . D z u l y n s k i a n d S a n d e r s (1962, p . 6 l ) h a v e c l a s s i f i e d s o l e m a r k s i n t o t h e f o l l o w i n g g r o u p s : a . M a r k s made p r i o r t o t h e a r r i v a l o f t h e c u r -r e n t - w h i c h d e p o s i t e d t h e c o v e r i n g bed:: 1 i . O r g a n i c . t r a c k s a n d b u r r o w s . -2. S t r u c t u r e s made b y \" c r e e p o r s l u m p o f t h e mud b e f o r e t h e c u r r e n t c a r r y i n g t h e m a t e r i a l f o r t h e - c o v e r i n g b e d a r r i v e d . b . . C u r r e n t m a r k s made i n t h e mud b y t h e p a s s a -g e o f t h e c u r r e n t w h i c h c a r r i e d t h e s e d i -m e n t , f o r m i n g t h e c o v e r i n g b e d : 1. S c o u r m a r k s ( f l u t e c a s t s , c h a n n e l s , a n d f r o n d e s c e n t m a r k s ) . 2. T o o l m a r k s : m a r k s w h i c h a r e made b y t h e c o n t a c t o f some o b j e c t ( t h e t o o l ) a n d t h e b o t t o m ( e . g . g r o o v e c a s t s a n d b o u n c e m a r k s ) . 7 6 c . M a r k s made a t t h e i n t e r f a c e b e t w e e n t h e mud a n d c o v e r i n g b e d a f t e r d e p o s i t i o n o f c o v e r -i n g b e d . 1. O r g a n i c t r a c k s a n d b u r r o w s . 2. S t r u c t u r e s made b y d e f o r m a t i o n d u e t o f l o w a g e , c r e e p , o r s l u m p i n g o f t h e s e d i -m e n t m a s s . L o a d c a s t s f a l l i n t h i s c a t e g o r y . R e l a t i v e l y f e w s o l e s o f s a n d s t o n e b e d s a r e w e l l e x -p o s e d i n t h e s t u d y a r e a , b u t a l m o s t a l l t h e d i f f e r e n t m a r k s t h a t b e l o n g t o t h e s e c o n d a n d t h i r d m a j o r g r o u p s o f t h e a b o v e c l a s s i f i c a t i o n h a v e b e e n o b s e r v e d i n t h e C e d a r D i s t r i c t F o r m a t i o n . I t w a s o b s e r v e d t h a t c u r r e n t m a r k s ( s c o u r a n d t o o l m a r k s , e s p e c i a l l y f l u t e c a s t s a n d g r o o v e c a s t s w i t h o c -c a s i o n a l c h a n n e l s ) a r e p r e s e n t o n l y o n t h e s o l e s o f s a n d -s t o n e b e d s t h i c k e r t h a n a f o o t a n d a h a l f . O r g a n i c b u r -r o w s o f t h e t y p e made a f t e r t h e d e p o s i t i o n o f t h e c o v e r -i n g b e d , a r e p r e s e n t i n b e d s o f v a r i a b l e t h i c k n e s s a n d a r e n o t r e s t r i c t e d o n l y t o t h i c k b e d s . B u r r o w s w h i c h c r o s s l o a d e d f l u t e c a s t s ( f i g . 58) c l e a r l y i n d i c a t e t h e i r p o s t - d e p o s i t i o n a l o r i g i n . 77 a . F l u t e C a s t s T h e s e a r e f i l l i n g s o f s c o u r m a r k s j made b y a t u r -b i d i t y c u r r e n t i n t h e u n d e r l y i n g mud. T h e f l u t e c a s t s p r o t r u d e f r o m t h e s o l e ; t h e y a r e o b l o n g w i t h t h e l o n g d i -m e n s i o n p a r a l l e l t o t h e c u r r e n t d i r e c t i o n . A t t h e u p -c u r r e n t e n d t h e f l u t e c a s t i s n a r r o w e r a n d p r o t r u d e s f u r -t h e r f r o m t h e s o l e t h a n i n t h e d o w n - c u r r e n t d i r e c t i o n ; ( B o u m a , 1 9 6 2 , p . 1 3 8 ) . W e l l d e v e l o p e d f l u t e c a s t s a r e f o u n d o n l y i n t h e s e c t i o n o f B e d w e l l H a r b o u r o f N o r t h P e n d e r I s l a n d . H e r e , o n l y t w o b e d s w e r e o b s e r v e d w i t h f l u t e c a s t s o n t h e i r s o l e s , a n d t h e s e b e d s w e r e t h i c k e r t h a n a f o o t a n d a h a l f . T h e s e f l u t e c a s t s a r e l e s s t h a n f i v e i n c h e s i n l e n g t h , a n d h a v e a w i d t h a v e r a g i n g a n i n c h a n d a h a l f , ( f i g . 4 9 ) . On t h e s o l e o f t h e same b e d c o n t a i n i n g t h e f l u t e c a s t s , f i n e , c l o s e l y s p a c e d g r o o v e c a s t s a n d b o u n c e m a r k s a r e a l s o f o u n d . A s l i g h t l y b i g g e r f l u t e c a s t w h i c h s h o w s some l o a d i n g , v/as - o b s e r v e d o n t h e s o l e o f a t h r e e f e e t t h i c k b e d i n V e s u v i u s B a y s e c t i o n , ( f i g . 5 9 ) . Q u e s t i o -n a b l e f l u t e c a s t s , w e r e o b s e r v e d i n t h e V e s u v i u s B a y s e c t i o n , e x t e n s i v e l y m o d i f i e d b y l o a d i n g a n d o r g a n i c b u r -r o w i n g ; t h e y s h o w p a r a l l e l i s m t o a g r o o v e c a s t p r e s e n t o n t h e same s o l e , ( f i g . $ 8 ) . 73 b. Frondescent_Marks ? Scour marks that are f i l l e d with coarse grained sand-stone containing scattered granules, have been observed on the sole of a thick sandstone bed in the uppermost part of the Vesuvius Bay section of Salt Spring Island; they are associated with and pa r t i a l l y obliterate gigantic groove, casts, indicating their formation subsequent to the formation of the groove casts ( f i g i 6 0 ) . They have a dendritic lobate form'j the average length of the i n d i v i -dual lobe i s four inches and average width i s about two inches* The down-currertt end of each lobe protrudes from the sole more than the up-current end ( f i g . 6 l ) i Scour marks of a similar nature have been produced experimentally, and called frondescent marks by Dzulynski and Walton (I962j p. 291, plate XXb and XXIa), and Dzulynski (1965, p» 198j f i g * 7)» Similar marks have been called \"cabbage leaf cast\" by Ten Haaf (1959), and \"fondescent furrow flute casting\" by Mclver (1961), in Potter and Pettijohn (1962, p. 126-127, f i g . 5-10)-. Scour marks that cut the underlying lamination in shale have been observed in one lo c a l i t y in Vesuvius Bay in Salt Spring Island. They are f i l l e d with coarse-grained sandstone and scattered granules, and a few of them show some loading, (figs. 62 and 6 3 ) . Due to 79 F i g . 6 0 : F r o n d e - s c e n t m a r k s ( a ) p a r t i a l l y o b l i t e r a t e g r o o v e c a s t s ( b ) o n t h e s o l e o f a t h i c k s a n d -s t o n e ' b e d t h a t d i p s s t e e p l y a w a y f om t h e o b -s e r v e r . C u r r e n t d i r e c t i o n f r o m l o w e r r i g h t t o u p p e r l e f t . T h e s c a l e i s 3 f e e t l o n g . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . F i g . 6 1 : A c l o s e - u p o f t h e f r o n d e s c e n t m a r k s o f t h e same b e d i n f i g . 6 0 . C u r r e n t d i r e c t i o n f r o m r i g h t t o l e f t . S c a l e i s a b o u t 8 i n c h e s l o n g . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . F i g . 6 2 : S c o u r m a r k s o n t h e b a s e o f a t h i c k s a n d s t o n e b e d u n d e r l a i n b y a t h i n b e d o f s h a l e . V e s u -v i u s B a y , S a l t S p r i n g I s l a n d , F i g ; 6 3 : L o a d e d s c o u r m a r k s o n t h e b a s e o f t h e same s a n d s t o n e b e d a s i n F i g . 6 2 . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . F i g . 6k: A s o l e o f a t h i c k s a n d s t o n e b e d ( s a m e a s i n f i g s . 6 0 a n d 6 1 ) , s h o w i n g a t l e a s t 3 g e n e r a -t i o n s o f g r o o v e c a s t s ; some s h o w c h a n g e i n d i r e c t i o n . C u r r e n t f r o m l o w e r r i g h t t o u p -p e r l e f t ( m e a s u r e d f r o m t h e f r o n d e s c e n t m a r k s t o t h e l e f t o f t h e s e g r o o v e c a s t s ) . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . 80 i n c o m p l e t e e x p o s u r e s , i t w a s n o t p o s s i b l e t o t e l l w h e t h e r t h e y a r e f l u t e c a s t s o r c h a n n e l s . c . G r o o v e C a s t s T h e s e s t r u c t u r e s a r e f o r m e d b y t h e f i l l i n g u p o f l o n g g r o o v e s s c o u r e d i n t h e u n d e r l y i n g mud b y some o b j e c t c a r r i e d i n a t u r b i d i t y c u r r e n t . T h e g r o o v e s a r e p a r a l -l e l t o t h e c u r r e n t d i r e c t i o n . T h e g r o o v e c a s t s t h e m -s e l v e s r e v e a l o n l y t h e l i n e o f c u r r e n t , b u t p r e s e n c e o f o t h e r m a r k s s u c h a s f l u t e c a s t s p r o v i d e i n f o r m a t i o n o n t h e c u r r e n t d i r e c t i o n . G r o o v e c a s t s a r e a l s o o b s e r v e d i n b e d s t h i c k e r t h a n a f o o t a n d a h a l f . I n o n e l o c a l i t y ( f i g . 4 9 ) , t h e y a r e v e r y n a r r o w , a m a t t e r o f a f r a c t i o n o f a n i n c h i n w i d t h , e x t e n d a l o n g t h e w h o l e e x p o s e d s o l e , a r e s t r i k i n g l y c l o s e l y s p a c e d , a n d a p p e a r t o h a v e b e e n f o r m e d b y c o a r s e g r a i n e d s a n d o r g r a n u l e s d r a g g e d o r p u s h e d a l o n g t h e m u d d y b o t t o m a t t h e b a s e o f a t r a c t i o n c a r p e t . I n t h e u p p e r m o s t s a n d s t o n e b e d s o f t h e C e d a r D i s t r i c t F o r m a t i o n , j u s t b e l o w t h e D e C o u r c y F o r m a t i o n a t V e s u v i u s B a y , a t h i c k b e d o f s a n d s t o n e h a s a t l e a s t t h r e e g e n e r a -t i o n s o f g r o o v e c a s t s o n i t s s o l e , a l l h a v i n g d i f f e r e n t s i z e s a n d o r i e n t a t i o n s , ( f i g . 64 a n d 6 5 ) . T h e same b e d a b o u t 50 f e e t t o t h e n o r t h w e s t h a s t w o g e n e r a t i o n s o f g r o o v e c a s t s i n t e r s e c t i n g a t a n a n g l e v a r y i n g f r o m 1 1 t o * 3 1 3 0 d e g r e e s ( f i g . 6 6 ) . Some o f t h e s e g r o o v e s a r e v e r y n a r r o w a n d s t r a i g h t ( f i g . 6 5 ) , o t h e r s a r e w i d e r a n d r a i s e d h i g h e r a b o v e t h e s o l e s u r f a c e a n d s h o w s u p e r i m p o s e d r i d g e s ( f i g s . 6 4 , 6 5 , a n d 6 6 ) . Some o f t h e l a t t e r g r o u p o f g r o o v e c a s t s s h o w a c h a n g e i n d i r e c t i o n ( f i g . 6 5 ) . T h e s h a p e o f t h e w i d e g r o o v e c a s t s w i t h t h e s u p e r i m -p o s e d r i d g e s s u g g e s t s t h e y may h a v e b e e n f o r m e d b y t h e d r a g o f a w a t e r - l o g g e d t r e e , t h e m a i n b r a n c h o r t r u n k o f w h i c h made t h e m a i n g r o o v e c a s t , t h e s u p e r i m p o s e d r i d g e s b e i n g f o r m e d f r o m t w i g s i n t h e t r u n k . T h e n a r r o w e r g r o o v e c a s t s w e r e o b v i o u s l y f o r m e d b y s m a l l e r t o o l s , s u c h a s p e b b l e s , w o o d f r a g m e n t s , o r s h a l e f r a g m e n t s , b u t n o n e o f t h e s e t o o l s h a v e b e e n f o u n d w i t h t h e c a s t s . T h e s t r a i g h t n e s s , c o n t i n u i t y , a n d u n i f o r m i t y o f h e i g h t a n d s t r u c t u r e o f g r o o v e c a s t s i n g e n e r a l l e d H s u (1959, p . 5 3 4 ) t o p o s t u l a t e l a m i n a r f l o w w i t h i n t h e c u r r e n t c a r r y i n g t h e t o o l s . D z u l y n s k i a n d S a n d e r s , ( 1 9 6 2 , p . 6 3 ) c o n s i d e r e d t h e i r f o r m a t i o n n o t a s a r e s u l t o f \" s e d i m e n t -l o a d e n t u r b u l e n t e d d i e s .... b u t r a t h e r t h e c u r r e n t c a u s e d l a r g e r o b j e c t s ( t o o l s ) , w h i c h t r a v e l i n l i n e a r p a t h s a s a r e s u l t o f i n e r t i a , t o s t r i k e t h e b o t t o m i n v a r i o u s w a y s \" , a n d c o n c l u d e d t h a t t h e y \" a r e t h e r e s u l t o f t r a n s p o r t a t i o n o f g r a i n s i n t h e t r a c t i o n m e c h a n i s m ( i n t h i s c a s e t h e d o m i n a n t a c t i v i t y i s s a l t a t i o n ) \" . S2 Fig. 6 $ : Groove casts of different shapes and sizes. Note the change in direction of the wide grooves with the superimposed ridges (a). Same bed as in f i g . 64 . Hammer indicated by an arrow. Vesuvius Bay, Salt Spring Island* Fig. 66 i ; Two generations of intersecting groove casts with superimposed ridges. Vesuvius Bay, Salt Spring Island. Fig. 67: , Clasts of laminated, fine-grained sandstone (at both ends of pencil) embedded in coarse-grained, thick sandstone bed. Vesuvius Bay, Salt Spring Island. F i g i 68: Deformed clast of laminated, fine-grained sand-stone embedded in thick bed of coarse-grained sandstone. Vesuvius Bay, Salt Spring Island. Fig. 69: Clast of fine-grained, laminated sandstone showing recumbent folding, embedded i n a thick bed of coarse-grained sandstone. Vesuvius Bay, Salt Spring Island. Fig. 70: Thinbeds of sandstone and their interlayered shale (at head of the hammer) involved i n soft-sediment deformation and engulfed by the over-lying thick sandstone bed. Note how these thin beds are s t i l l connected with the underlying .undisturbed beds. Vesuvius Bay, Salt Spring Island. Fi3-^ 9 F-,3-70 $3 T h e v a r i a t i o n i n d i r e c t i o n o f g r o o v e c a s t s o n a s i n g l e s o l e ( e . g . f i g s . 64 a n d 65) h a s b e e n a t t r i b u t e d b y T e n H a a f (1959, i n D z u l y n s k i a n d S a n d e r s , 1 9 6 2 , p.86) n o t t o c h a n g e i n t h e d i r e c t i o n o f t h e e n t i r e c u r r e n t , b u t t o t h e c r i s s - c r o s s i n g o f l o b a t e f r o n t s o f t h e c u r r e n t . D z u l y n s k i a n d S a n d e r s (1962, p.91) s u g g e s t e d t h a t t h i s c h a n g e i n d i r e c t i o n o f t h e t o o l m a r k s i s t h e r e s u l t o f c h a n g e i n d i r e c t i o n o f m o v e m e n t w i t h i n t h e t r a c t i o n c a r p e t . d . B o u n c e C a s t s T h e s e s t r u c t u r e s a r e d e f i n e d b y Bouma (1962, p.135) a s \" s o l e m a r k i n g s , v a r y i n g u p t o 5 cm i n l e n g t h a n d s o m e -w h a t l e s s i n w i d t h , r u n n i n g p a r a l l e l t o t h e c u r r e n t d i r e c t i o n . T h e s e s h o r t g r o o v e s w e r e p r e s u m a b l y p r o d u c e d b y o b j e c t s g r a z i n g t h e b o t t o m a n d r e b o u n d i n g , l e a v i n g b e h i n d a s h a l l o w g r o o v e w h i c h f a d e s o u t g r a d u a l l y a t b o t h e n d s . \" I n t h e C e d a r D i s t r i c t F o r m a t i o n s u c h c a s t s w e r e o n l y o b s e r v e d o n t h e s o l e o f a s a n d s t o n e b e d i n B e d w e l l H a r b o u r i n N o r t h P e n d e r I s l a n d ( f i g . 49). . . T h e y a r e a b o u t o n e i n c h l o n g , a n d a f r a c t i o n o f a n i n c h w i d e , a n d t e n d t o b e p a r a l l e l t o t h e a s s o c i a t e d f l u t e a n d g r o o v e c a s t s . T h e y i n d i c a t e t h e t r a c k o f t h e c u r r e n t b u t n o t i t s d i r e c t i o n , s i n c e t h e y f a d e e q u a l l y o n b o t h e n d s . • $4-e. O r g a n i c B o r i n g s and Burrows B e s i d e t h e b o r i n g s and burrows t h a t a re found t o p r o t r u d e i n t o s h a l e and the c a l c a r e o u s c o n c r e t i o n s , t h e r e a r e a l s o some sandstone beds w i t h o r g a n i c b o r i n g s and burrows on t h e i r s o l e s ( f i g . 58)» That t h e s e b o r i n g s and burrows p r o b a b l y o r i g i n a t e d a f t e r the f o r m a t i o n and l o a d -i n g o f t h e s c o u r marks i s suggested by the f a c t t h a t , i n some c a s e s , t h e y p a r t i a l l y o b l i t e r a t e s c o u r marks on t h e same s o l e ( f i g ' . 5 8 ) . C. .Soft-Sediment D i s t u r b e d Bedding. S t r u c t u r e s (slump o v e r f o l d s ) t h a t a r e t h e r e s u l t o f sl u m p i n g on S a t u r n a I s l a n d , were d i s c u s s e d i n a p r e v i o u s s e c t i o n on p e b b l y mudstone. An i n t e r v a l o f about 3 3 0 f o o t i n the middl e o f t h e V e s u v i u s Bay s e c t i o n on S a l t S p r i n g I s l a n d , i s c h a r a c t e r -i z e d by abundant t h i c k beds o f sandstone (up t o 7 f e e t t h i c k ) . These beds are i n t e r n a l l y s t r u c t u r l e s s except f o r \"rude g r a i n s i z e g r a d i n g from g r a n u l e s and c o a r s e -g r a i n e d sand, a t t h e bottom t o medium and f i n e - g r a i n e d sand a t t h e top.-. I n t e r b e d d e d w i t h t h e s e t h i c k beds,' are t h i n -ner bedded, l a m i n a t e d sandstone (B- and C - d i v i s i o n ) , and s h a l e ( D E - d i v i s i o n o f i n t e r t u r b i d i t e ) . These t h i c k beds o f sandstone almost always e n c l o s e 6*5 F i g . 71 : C l a s t s o f f i n e - g r a i n e d , l a m i n a t e d s a n d s t o n e s h o -w i n g s l i g h t d e f o r m a t i o n , e n c l o s e d i n a t h i c k b e d o f c o a r s e - g r a i n e d s a n d s t o n e . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . F i g . 72: C l a s t s o f f i n e - g r a i n e d s a n d s t o n e a n d s h a l e s h o w i n g a s y m e t r i c a l f o l d i n g , e n c l o s e d i n a t h i c k b e d o f s a n d s t o n e . W h i t e o b j e c t s a r e en-c r u s t i n g b a r n a c l e s . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . F i g . 73: F i g . 74: F i g . 75 : R e c u m b e n t f o l d i n g i n s a n d s t o n e a n d s h a l e c l a s t s w h i c h a r e e n c l o s e d i n a t h i c k b e d o f s a n d s t o n e . V e s u v i u s . B a y , S a l t S p r i n g I s l a n d . C l a s t s o f f i n e - g r a i n e d s a n d s t o n e b e d s e n c l o -s e d i n c o a r s e - g r a i n e d t h i c k s a n d s t o n e b e d . T h e s e c l a s t s s h o w c o m p l e x d e f o r m a t i o n . B e d s d i p s t e e p l y t o t h e l e f t . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . S a n d s t o n e d i k e c u t t i n g t h r o u g h s h a l e . M a y n e I s l a n d . F i g . 76: V e r y t h i n d i s c o n t i n u o u s s a n d s t o n e d i k e c u t t i n g t h r o u g h s h a l e . M a y n e I s l a n d , 86 clasts and pieces of beds composed of coarse-grained sand-stone, laminated fine to medium-grained sandstone, or shale, or a combination.of two or three of them. These clasts occur either in the form of small, angular chips a few inches in length ( f i g . 6 ? ) , or large, gently or tightly folded clasts ranging in length from a few feet (figs. 27, 68, and 69 ) , to several feet ( f i g . 26 ) . Some of these deformed layers can be traced l a t e r a l l y and ob-served to connect with the underlying undisturbed beds (f i g . 7 0 ) , This kind of bedding and the associated en-closed clasts are also present intermittently in the upper part of the Vesuvius Bay section* These enclosed clasts are fragments of beds that seem to have been stripped from originally coherent layers. They represent fragments of beds belonging to the B, C, and DE divisions. Beds underlying the thick sandstone beds are composed essentially of B, C, and DE divisions. • These clasts exhibit a wide range of structures. Some are gently folded (figs. 27 and 71) , others show a symetrical folding ( f i g . 72 ) , the majority show recumbent folding (figs. 26, 69, and 73 ) , and s t i l l others are thrown into a complex pattern of folding ( f i g . 7 4 ) . The last type of folding involves clasts that can be traced l a t e r a l l y into the underlying undisturbed beds. 37 The disturbed layers are always seen i n only.two dimensions. The strike of their fold axes appears to • have a general preferred orientation of northwest- ,t southeast, but precise measurement is not possible, be- • cause of lack of three dimensional outcrops. By using graded bedding and the v e r t i c a l succession of the d i f -ferent turbidite divisions, the author v/as able to deter-mine top-bottom relationships in the disturbed, layers and thus could differentiate between anticlines and .synclines in tne case df recumbent folds ( f i g . 2 6 ) . In the case of thin-bedded, laminated,- complexly folded clasts, howeyer, i t was not possible to determine top-bottom relationships, hence i t v/as not possible to determine'whether the: folds are synclines or anticlines. Certain limitations can be placed on 'the processes which deformed these beds. Since the beds overlying and underlying the deformed beds are undisturbed, this defor-mation must have been syndepositional. The thick sand-stone host beds were soft enough to engulf the underlying thinner sandstone and shale beds; the latter must have been also soft, but they were cohesive enough to be plas-t i c a l l y deformed and not dispersed into a cohesionless mass!'' The fact that some deformed clasts, in. the thick C58\" sandstone beds, are s t i l l connected to the underlying un-deformed beds suggests that they were deformed and en-gulfed without late r a l transport during the emplacement of the overlying sand. Other clasts in the thick sand-stone beds, which are disconnected from the underlying undeformed beds , may or may have not undergone appreci-able late r a l transport. From the above i t can be concluded that the enclo-sed cxasts were originally parts of soft, undisturbed, s t r a t i f i e d beds on the sea bottom. They subsequently became disturbed and broken up during passage of a current carrying a dense slurry of sand which engulfed them. This slurry was later deposited as a thick sand bed. Dzulynski and Radomski (1966)'experimentally repro-duced nearly identical structures by introducing a heavcy suspension into a flume tank whose bottom was covered with s t r a t i f i e d soft layers. The bottom layers were interlayered clay beds, deposited by normal settling in the flume, and beds of mixed plaster of Paris and coal dust deposited t. an a r t i f i c i a l turbidity current. The introduced heavey suspension was composed of a mixture of plaster of Paris, cement, sand, and occasionally small pebbles dispersed i n water. 'When this heavey suspension $9 F i g . 77: F i g . 78: F i g . 79 : F i g . ;80: F i g . 81: F i g . 82' T h i c k sandstone d i k e c u t t i n g s h a l e sequence. Dodd Narrows, Vancouver I s l a n d . B r a n c h i n g sandstone d i k e (hammer a t p o i n t of b r a n c h i n g ) . Dodd Narrows, Vancouver I s l a n d . Sandstone d i k e c u t t i n g s h a l e . Note c o n t o r t e d l a m i n a t i o n w i t h i n the d i k e . Dodd Narrows, Vancouver I s l a n d . E x o t i c b l o c k o f sandstone embedded i n s h a l e , Note the b e n d i n g o f s h a l e l a m i n a t i o n below the b l o c k , and t h e a b r u p t t e r m i n a t i o n of l a -minae a g a i n s t l e f t s i d e o f t h e b l o c k . Dodd Narrows, Vancouver I s l a n d . E x o t i c b l o c k o f sandstone embedded i n s h a l e , A l s o note the ben d i n g o f s h a l e l a m i n a t i o n around the b l o c k , and the absence o f o t h e r e x o t i c m a t e r i a l s * Dodd Narrows, Vancouver I s l a n d . Deformed, l a m i n a t e d sandstone c l a s t s enclosed i n s h a l e . N o t e fragmented sandstone bed above the c l a s t s . Mayne I s l a n d . 90 w a s a l l o w e d t o f l o w o v e r t h e s o f t , s t r a t i f i e d b o t t o m s e d i -m e n t s i n t h e f l u m e , c o n s i d e r a b l e d e f o r m a t i o n o f t h e s t r a t i -f i e d d e p o s i t s o c c u r e d . T h e l a t t e r b e d s w e r e b r o k e n u p i n t o c l a s t s a n d e n g u l f e d i n t o t h e h e a v e y s u s p e n s i o n . O n c e t h e h e a v e y s u s p e n s i o n h a d c o m p l e t e l y s e t t l e d a s a \" t h i c k \" s a n d l a y e r , t h e e n c l o s e d c l a s t s a s s u m e d a w i d e r a n g e o f d e f o r m a t i o n a l p a t t e r n s ( D z u l y n s k i a n d R a d o m s k i , 1966; p h o t o s : 1 t o 5 ) . T h e s i m i l a r i t y o f some o f t h e s e d e f o r m e d c l a s t s t o w h a t ' h a v e b e e n c a l l e d \" s l u m p o v e r f o l d s \" , \" p s e u d o - n o d u l e s \" , a n d \" b a l l - a n d p i l l o w \" s t r u c t u r e s , l e d t h e a u t h o r s t o p o s t u l a t e s u c h a m e c h a n i s m f o r t h e f o r m a -t i o n o f t h e s e s t r u c t u r e s . L i k e w i s e , t h e s i m i l a r i t y b e t w e e n t h e s e e x p e r i m e n t a l l y p r o d u c e d s t r u c t u r e s a n d t h o s e o b s e r v e d i n t h e V e s u v i u s B a y s e c t i o n l e a d s t h e p r e s e n t a u t h o r t o p o s t u l a t e a s i m i -l a r m e c h a n i s m ; i . e . i m p a c t o f a h e a v e y s u s p e n s i o n u p o n h o r i z o n t a l s o f t s e d i m e n t a r y l a y e r s . T h i s c o u l d i n v o l v e f l o w o f a t u r b i d i t y c u r r e n t w i t h a t r a c t i o n c a r p e t m o v i n g o v e r s o f t , p r e v i o u s l y d e p o s i t e d t u r b i d i t e b e d s . D. S a n d s t o n e D i k e s a n d M i s c e l l a n e o u s F e a t u r e s S a n d s t o n e d i k e s w e r e f o u n d o n l y i n t w o l o c a l i t i e s t h r o u g h o u t t h e o u t c r o p a r e a o f t h e C e d a r D i s t r i c t F o r m a -t i o n . I n t h e D o d d N a r r o w s a r e a o f V a n c o u v e r I s l a n d , w h e r e t h e u p p e r 1010 f e e t o f t h e f o r m a t i o n i s e x p o s e d , s a n d s t o n e 91 dikes quite commonly cut a shale sequence containing a few thick sandstone beds ( f i g . 1 4 ) . Also on Mayne Island, where the upper 200 feet of the formation are exposed on the- south coast 3 the lower 50 to 70 feet of this section contains occasional sandstone dikes cutting shale beds (f i g . 7 5 ) . Thus in both l o c a l i t i e s , the sections cut by dikes are mainly shale with a few thick sandstone inter-beds . The sandstone dikes are tabular bodies, ranging in thickness from a fraction of an inch ( f i g . 76) to about 3 feet ( f i g . 77)* In general they have sharp walls, and they may cut the host beds either at right angles, high angles, or very low angles. Their shapes vary from straight, regular, thick dikes ( f i g . 77) , to irregular thin dikes ( f i g . 14) . Most of the dikes can be traced for only relatively short distances, either because they are discontinuous or because of lack of exposures. In one case ( f i g . 2 3 ) , a sandstone dike was observed to extend downward from a thick sandstone bed for a distance of a foot and a half through laminated shale before i t disappears into the shale bedding plane. One of the thick dikes i s observed to branch into an offshot that runs at a low angle across the bedding planes of the host rocks ( f i g . 78)• 92 The thick dikes seem to be structureless as observed by the nacked eye in the f i e l d . Some of the thin dikes show distinct lamination, which i s commonly wavey and occa-sionally contorted, roughly resembling current ripple and convolute lamination ( f i g . 79). Whenever the host rocks are faulted, the associated sandstone dikes are also faulted, indicating that the sand injection took place before faulting. In the same shale intervals where the sandstone dikes are present, are clasts and blocks of rocks, either of lithology foreign to the host rocks ( f i g . SO and S i ) , or of the same lithology as some beds overlying the host rocks ( f i g . 82). Blocks of the former type are observed only in the Dodd Narrows area on Vancouver Island. Shale-lamination overlying and. underlying these blocks curves around the blocks ( f i g . S i ) , while l a t e r a l l y adjacent lamination ends abruptly against steep sides of the blocks ( f i g . SO). Because only two or three of these blocks, which are widely spaced i n the- horizontal direction, have been observed within this shale interval, and because of the fact that they are surrounded by well laminated, un-disturbed shale, with no other exotic clasts or pebbles and sand i n the v i c i n i t y , the pos s i b i l i t y of their intro-duction as a mass slump o r slide seems improbable, since 93 one would expect to find a mixture of elastics of d i f f e r -ent sizes and shapes, as in a pebbly mudstone. Their origin i s problematical, but two po s s i b i l i t i e s exist: (1) They may represent isolated sand-filled channels. The wedge-like shape of some blocks ( f i g . 81) and the fact that adjacent shale laminae terminate abruptly against the sandstone ( f i g . 80) tend to support this interpretation. But the overall shape of other blocks (fig.. 80) do not in any way resemble channels. (2) They may represent blocks of sandstone transported individually from elsewhere; the fact that the blocks are not folded would indicate their introduction as highly consolidate!1., or cemented, masses, otherwise they would have been deformed. One poss i b i l i t y i s that the blocks were detached from shoreline c l i f f s or sea bottom outcrops by gravity and/or seismic shocks and s l i d or rolled down into the basin of shale deposition, truncating some laminae during f i n a l emplacement. Sub-sequent burial and compaction around the coherent blocks would, produce the curving laminae above and below ( f i g . 8 l ) . Although the exact origin remains unclear, the author i s inclined to favor the second p o s s i b i l i t y , or some variant of i t . Clasts of this latter type occur in one l o c a l i t y as deformed sandstone clasts, which show no preferred 9h orientation, and are embedded in a shale host rock ( f i g . 82). Just above this shale ami i t s enclosed clasts i s a bed of sandstone with characteristics similar to those of the underlying sandstone clasts. This sandstone bed i s fragmented just above the sandstone clasts, as i f these clasts were once part of the sandstone bed. This kind of feature seems to have been formed when a sand bed was deposited on a soft muddy bottom; later this bed may have been fragmented into clasts which were then folded and sank into the underlying mud. The disruption of this sand bed into sand clasts could be accounted for by some kind of a shock (e.g.. an earthquake). The formation of sandstone dikes has been accounted for as a result of \"earthquake shock, momentary l i q u i f i -cation of watersaturated sand, and injection into fissures opened by the shock. The driving force i s the pressure of the overlying strata.\", (Potter and PettiJohn, 1963, p. 165). From the above, i t could be inferred that during deposition of the shale sequence with occasional sandstone beds, the site of deposition and adjacent areas were tec-h n i c a l l y active and suffered a period of intermittent earthquakes. These caused l i q u i f i c a t i o n of the soft sand and i t s injection into fissures opened in the surrounding S e r i a l Hoo 1 2 3 4 5 6 8 9 i o 1 12 r 1 4 1 5 16 17 18 1 9 2 0 - 21 2 2 2 3 2 4 2 5 26 ^taCnvrfv-vmTiTirra= j - Specimen Wo0 V 1 0 3 C V l l V26 V30 V34 V 3 9 VSA3 V S C 6 VS18 P 3 4 P I 5 p i ' 2 5 P B 2 4 P B 4 PA? P B 1 0 P A 1 2 PB13 PC 15 S ? Sa Sb C l C 6 M4 I Quartz 3 6 e 5 2 7 * 5 4 5 o 8 3 5 o 5 2 6 0 0 3 3 * 7 2 8 o 0 44 a 7 3 9 o 2 2 9 o 7 4 4 o 3 5213 1 • 2 8 , 4 5 0 o 0 48 08 5 7 o 4 3 9 . 0 5 1.0 4 5 . 2 4 3 . 3 4 9 . 0 4 2 . 2 3 1 . 4 3 4 . 7 3 6 . 3 3 5 . 5 i K=»feldspar 9 c 2 4 c 9 4 o 7 7 o l 7 * 0 1 2 . 6 9 o 3 2 0 o 6 5 o 3 4 . 6 J 3 J 3 j i ' 5 . 1 8 . 0 8 . 1 7.7 17.7 10.0 5 . 2 4 . 7 9 . 3 8 . 3 7.0 4 . 7 9 . 0 6.1 Plagioclase 6 o 5 4 o 0 2 0 , 5 l l » 5 17 .1 I 2 J 5 1 9 c 5 14 . 7 5 . 8 1 5 . 6 1 8 . 6 12.1 Mica 9 o 2 5 o 3 l o d 4 o 9 3 o 8 2 o 9 8„0 13 0 6 2 o 4 2 O 0 4 o 3 4 . 0 ! 4 . 7 12 . 4 5 . 5 3 . 0 1 . 4 5 . 6 8.0 10.0 6.0 7 . 3 2 . 9 4 . 7 2 . 3 2 e !L C h l o r i t e 0 o 7 0 .7 c=e= l o 2 4 o 4 0 o 7 i j o 0 . 9 0.2 0 . 8 1 . 6 1 . 3 0 . 4 0 . 8 0 .7 1 . 0 - 0 . 3 0 . 2 0 . 7 Volcanic rock fragments C D 0 e 2 1 * 7 2»8 5 d 6 o l 4 o 5 =, 1 1 0 0 0 0 2 1O 6 2 i l J t 0.4 1.0 ens 0 . 8 4 . 7 6 . 6 0.2 0 . 8 Sedimentary rock fragments 0 o 2 0 o 2 0 o 2 l o 5 2 i o 6 «— 2.1 4 o 8 0 o 7 1 P 7 < L « 2 i 1 . 0 . 4 0 . 5 1 . 9 1 . 6 6.0 ex» 1.4 0 o 2 - 0 .3 C D 0 . 8 Metam©rphic rock fragments = l o 4 0 o 4 — 0 o2 0 o 3 3 o 3 1I2-t •= 0 . 4 0 . 3 e a 0 0.2 CO 0 . 9 0 .6 0 . 3 Polycryst a llin« quarts i o o 0 o 2 3 o 4 0 o 8 0 o 5 7 o 7 l o d 5 . 0 i 1 ~ 0 . 4 0 .4 0 . 8 1 . 2 0 . 6 0 . 8 G> 1 . 0 0 . 3 1 . 3 Chert l o 4 0 o 2 0 o 3 4 c 3 4 o 2 1 P 3 2o0 0 o 4 4 o 4 0 o 9 0 o 3 2 J 7 0 ; 1 . 8 2 . 5 1 . 3 3 . 6 4 . 0 2 . 6 1 .5 0 . 5 2 . 9 0 .7 0 . 3 C a l c i t e cement 2 4 o 6 4 9 o 6 3 4 * 5 3 3 o 9 2 9 o 7 2 0 7 2 6 o 8 4 o 0 4 « 6 ( 1 2 1 . 0 1 3 o 3 1 2 . 8 2 3 . 3 1 8 . 5 2 6 o 2 1 2 . 3 8 . 5 2 9 . 2 7.4 0 . 9 1 4 . 9 42.1 S i l i c e o u s cement => as 4.0 4 I j - = 6 0 4 •- - I » Matrix 7 o 2 2 . 0 5 . 3 3 . 4 2 7 o 5 6 P 3 l 6 o l 2 7 c 7 13 * 9 8 0 3 1 4 o l 6 d 2 1 5 6 . 0 1 . 8 5.0 6 . 6 7 . 6 9 . 6 2 . 2 2 4 . 3 3 . 7 2 . 2 2 3 . 1 2 5 . 4 4.0 6 . 3 Unkn@wn 1 * 6 2 00 1 * 8 l o 2 3 . 8 2 o 9 0 . 6 2 o 7 l - o 2 2 © 2 2 . 1 i 2 o 7 0 . 4 2 , 4 2 . 8 1 . 7 1 . 2 1 . 3 1.6 2 . 2 1 . 7 1 . 3 0 . 7 2 . 1 2.0 Others 3 » 6 4 c 2 3 o 2 2.0 l o 7 1 O 6 1 0 3 2 o 4 0 o 3 4 o 6 0 o 6 0 o 8 2 . 2 2 • 2 3 . 2 6 . 0 O r» 1 . 8 2 . 6 - 1 . 2 .—4 2 . 5 L1 1 , 8 2.0 I 0 6 1 . 0 3 . 6 J r — _ Table 2s • ,• Composition ©f the Cedar D i s t r i c t sandst@nes 0 j * 5 i l C r 1 8 t 5 1 Q n * e q u a r t z 0 8 ^ a r t s i t e i n c l a s s i f i c a t i o n t r i a n g l e s 96 coherent mud. These shocks may have also resulted in the disruption of some thin beds of soft but cohesive sand into clasts that sank into the underlying soft mud, for-ming what are observed now as sandstone clasts embedded in shale host rock with a r e l i c of the ,:mother\" sandstone bed underlying them ( f i g . $2). At the same time, i t i s possible that these shocks affected the shore line or sea bottom outcrops, resulting in the detachment of some sandstone blocks which s l i d or rolled \\own across the basin slope as individual blocks. Such downslope trans-portation may have been intermittent, requiring a series of such shocks. 7. PETROGRAPHY OF THE SANDSTONE The composition of twenty six sandstone samples was determined quantitatively by the method of point-count. Twelve of these samples were stained with sodium coba l t i n i t r i t e for potash feldspar determination. Table 2 shows the results of these determinations. A. Quartz: This i s the most abundant mineral component of the Cedar Di s t r i c t sandstone, varying from 26.0 to 57.4 per-cent and averaging 39.8 percent. No attempt was made to 97 F i g * 83: P h o t o m i c r o g r a p h s h o w i n g t h e r e p l a c e m e n t o f a q u a r t z g r a i n b y t h e c a l c i t e c e m e n t a l o n g f r a c t u r e s ( i n d i c a t e d b y a r r o w s ) . C r o s s e d n i c o l s . V e s u v i u s B a y , S a l t S p r i n g I s l a n d ( V 3 9 ) . F i g . - 84: P h o t o m i c r o g r a p h s h o w i n g t h e r e p l a c e m e n t o f a q u a r t z g r a i n (Q, i n d i c a t e d b y a r r o w s ) a n d a f e l d s p a r g r a i n ( F ) b y t h e c l a y - s i z e m a t r i x . ' C r o s s e d n i c o l s . V e s u v i u s B a y , S a l t S p r i n g I s l a n d . ( V S 1 8 ) . F i g . ' 8 5 : P h o t o m i c r o g r a p h s h o w i n g t h e r e p l a c e m e n t o f a f e l d s p a r g r a i n ( F , i n d i c a t e d b y a r r o w s ) b y t h e c a l c i t e c e m e n t a l o n g f r a c t u r e s . C r o s s e d n i c o l s . • V e s u v i u s B a y , S a l t S p r i n g I s l a n d . (V39). F.3- 8 3 F»3 85\" 96\" classify tho quartz into the different types based on the external morphology, internal features, and extinction characteristics. The work by Blatt and Christie (1963) has cast doubt on using the above mentioned properties for the purpose of relating the quartz to i t s parent rocks. Size of the quartz grains varies from fine s i l t to very coarse sand, but they most commonly occur as fine to medium grained sand. Roundness shows wide variation,-ranging from very angular to rounded, with the majority of the grains being subangular to subrounded. This var i -ation in roundness i s believed by the author to be large-ly due to the replacement of the grains by the calcite cement and by the matrix (figs. S3 and S 4 ) . B. Feldspar: Several varieties of feldspars are present. In the twelve thin sections that have been stained with sodium co b a l t i n i t r i t e , potash feldspars (orthoclase and few-microcline) show an average of 6.8 percent of the entire assemblages, with a range from 3-3 to 9.3 percent. Plagioclase feldspars have an average of 12.4 percent and range from 4 .0 to 20.5 percent. In a l l twenty six thin sections, feldspars .(both potash and plagioclase) show an average of 13.6 percent, with a range of 4 .7 to 27.5%. 99 The plagioclase feldspars, based on their optical proper-t i c s , are mainly oligoclase and andesine; albite and labradorite are very rare* The majority of these feldspars are fresh and easi-l y identified, but some show considerable alteration and can be recognized only by twinning. As i s the case with the quartz, the feldspars show wide variation in size and roundness, and also show replacement by the calcite cement and the clay matrix (figs. $4 and 85). C. Rock Fragments Rock fragments include, volcanic, sedimentary, and metamorphic rock fragments'in that order of abundance.. . They have an average abundance of 4.1 percent, and range from zero to 26.1 percent. They are most abundant in the coarser fractions of the .sandstones, and when the coarsest fractions are finer than medium-grained sand, rock fragments become very rare or absent. Volcanic rock fragments compose an average of 1.9 percent, ranging rorn zero (nine thin sections) to 11.1 percent. The majority of the volcanic rock fragments are porphyritic, with a fine grained matrix of plagioclase laths and phenocrysts of plagioclase and/or quartz ( f i g . $6). Under plane polarized l i g h t , these fragments are greyish in appearance due to the scattered iron oxides 100 dust, p r e s e n t as i n c l u s i o n s J\" S edimentary r o c k fragments are almost e n t i r e l y composed o f s h a l e ( f i g , S7), w h i c h i s o c c a s i o n a l l y s i l t y ; they average 1.8 p e r c e n t , and range from z e r o (seven t h i n s e c t i o n s ) to 21.6 p e r c e n t . Meta-morphic r o c k fragments ( e x c l u d i n g m e t a q u a r t z i t e itfhich i s i n c l u d e d w i t h the p o l y C r y s t a l l i n e q u a r t z ) c o n s t i t u t e a minor f r a c t i o n o f the r o c k s C o m p o s i t i o n * They have an average o f 0.4 p e r c e n t , and range from z e r o (14 t h i n s e c t i o n s ) t o 3.3 p e r c e n t . They c o n s i s t o f s l a t e , p h y l l i -t e , s c h i s t , arid some u n i d e n t i f i e d , C h l o r i t e - ' r i e h meta-r morphic r o c k f r a g m e n t s . P. M-ica M i c a s a r e u b i q u i t o u s . They have an average o f 5.3 percent,- and range from 1.4 t o 12 <4 p e r c e n t . About 90.1 p e r c e n t o f t h e micas are b i o t i t e , t h e remainder m u s c o v i t e . They a r e observed t o be more abundant i n t h e l a m i n a t e d sandstones ( p l a n e - p a r a l l e l , c o n v o l u t e , and r i p p l e l a m i n a -t i o n ) where t h e y c o n s t i t u t e t h e d a r k e r laminae ( f i g s . 50, 51, 54, and 55). Most commonly t h e s e sandstones have a mean g r a i n s i z e r a n g i n g from v e r y f i n e t o f i n e - g r a i n e d sand. E. C h l o r i t e C h l o r i t e o c c u r s i n o n l y minor amounts i n t h e s e sand-101 s t o n e s . I t has an average o f 0.7 p e r c e n t and ranges from z e r o ( s i x t h i n s e c t i o n s ) t o 4.4 p e r c e n t . Most o f t h i s c h l o r i t e seems t o be i n the p r o c e s s o f a l t e r a t i o n e i t h e r from b i o t i t e o r t o b i o t i t e ; i t i s u s u a l l y found g r a d i n g i n t o the a d j a c e n t b i o t i t e w i t h o u t a w e l l d e f i -ned boundary. F. P o l y c r y s t a l l i n e Q u a r t z : A l l t h e p o l y c r y s t a l l i n e q u a r t z o f d i f f e r e n t o r i g i n s have been c l a s s i f i e d under t h i s c a t e g o r y . They i n c l u d e s e d i m e n t a r y q u a r t z i t e , m e t a q u a r t z i t e , and p o s s i b l y some p l u t o n i c p o l y c r y s t a l l i n e q u a r t z * They have an a v e r a g e o c c u r r e n c e o f 1.0 p e r c e n t , and rage from z e r o ( t e n t h i n s e c t i o n s ) t o 7.7 p e r c e n t . G. C h e r t : A l l t h e m i c r o c r y s t a l l i n e and c h a l c e d o n i c q u a r t z i s c l a s s i f i e d as c h e r t ( f i g . 94). T h e i r average abun-dance i s 1.7 p e r c e n t , and rage from z e r o t o 4.4 p e r c e n t . H. Other M i n e r a l s : These a r e t h e a c c e s s o r y m i n e r a l s and t h e c a r b o n a -ceous m a t t e r , w i t h an average abundance o f 2.3 p e r c e n t , and range from 0.3 t o 6.0 p e r c e n t . The a c c e s s o r y mine-r a l s a r e as f o l l o w s i n d e c r e a s i n g o r d e r o f abundance as 102 Fig. 86: Photomicrograph of arkosic wacke showing a volcanic rock fragment (V), Crossed nicols, Vesuvius Bcay, Salt Spring Island. (V34-). Fig. 87: Photomicrograph of l i t h i c wacke showing shale rock fragments (S). Crossed nicols. Vesuvius Bay, Salt Spring Island, (VSA3). Fig. 8$: Photomicrograph of feldspathic arenite sho-wing siliceous cement (S). Crossed nicols. Bedwell Harbour, North Pender Island (PB13). 1C3 identified with the petrographic microscope: Pyrite, epidote, apatite- hematite, garnet, and zircon. The carbonaceous matter i s as abundant as the pyrite, and i s present in almost a l l the thin sections that have been examined. I. Unknown Minerals: These are the minerals that are unidentifyable due to their high degree of alteration. They range from zero to 3 . 6 percent) and have an average of 1.8 percent. J. Cementt Cement is an important constituent in most of the thin sections studiedj ranging from zero to 42.1 percent and averaging 17.4 percent; of the latter calcite cement makes up 17.0 percent and siliceous cement 0.4 percent. Calcite cement occurs as micrite and sparite> and i t i s commonly found to replace the surrounding grains (figs. 83 and 8 5 ) , changing their size and shape. It i s also found to replace the matrix minerals. The siliceous cement, when present, has the texture of chert, but i t could be differentiated from chert by i t s form. Chert occurr always as grains with definite boundaries, while the siliceous cement occurs as f i l l i n g of pore spaces ( f i g . 8 8 ) . / 104 K . M a t r i x : The m a t r i x r anges f rom 1.8 t o 5 6 . 0 p e r c e n t , and a v e r -ages 1 2 . 1 p e r c e n t . C o n s t i t u e n t s c l a s s i f i e d as m a t r i x a r e a l l g r a i n s l e s s t h a n 30 m i c r o n s i n s i z e . M a t r i x c o m p o s i t i o n i s c o n s i s t e n t i n a l l s a m p l e s , c o n s i s t i n g m a i n l y o f c l a y m i n e r a l s , m i c a , f e l d s p a r , and q u a r t z . The f i n e s t c o n s t i t u e n t s o f t h e m a t r i x ( e . g . c l a y m i n e r a l s and the f i n e l y d i v i d e d m i c a ) commonly r e p l a c e the s u r r o u n d i n g g r a i n s ( f i g . 84) c h a n g i n g t h e i r s i z e and-shape* O b s e r v a t i o n s on the m a t r i x - g r a i n r e l a t i o n s h i p s i n the s ands tone o f t he Cedar D i s t r i c t F o r m a t i o n , i n d i c a t e t h a t a t l e a s t p a r t o f t h e m a t r i x i s o f d i a g e n e t i c o r i g i n (R . Rahmani , 1 9 6 $ ) . F i n e l y d i v i d e d m i c a and c l a y m i n e r a l s a r e observed, t o r e p l a c e the s and - . s i z e g r a i n s , t h u s p r o d u c i n g f i n e - g r a i n e d m a t e r i a l and c o n t r i b u t i n g t o t h e volume o f the m a t r i x ( f i g s . 8 4 and 9 5 ) . P e t t i J o h n (1957 , p . 3 0 5 ) i n a d i s c u s s i o n o f t he o r i g i n o f m a t r i x o f greywacke sands tones , s t a t e d : \" I t seems most p r o b a b l e t h a t a l l t h e m a t r i x m i n e -r a l s a r e , i n d e e d , a u t h i g e n i c and a r e the r e s u l t o f r e o r g a -n i z a t i o n o f an i n t e r s t i t i a l m u d . \" Cummins (1962) sugges -t e d i n h i s s t u d y o f the greywacke p r o b l e m t h a t m a t r i x o f g reywacke i s no t o f a p r i m a r y o r i g i n , s u b s t a n t i a t i n g h i s s u g g e s t i o n by c o m p a r a t i v e s i z e a n a l y s i s o f a n c i e n t g r e y - ... wackes and o f Recen t and e x p e r i m e n t a l t u r b i d i t e s . He showed t h a t Recen t and e x p e r i m e n t a l t u r b i d i t e s have n e g l i g i b l e -105a- / Fig.89: C l a s s i f i c a t i o n of pure sandstones, or arenites. After G i l b e r t (195^). Small numbers r e f e r to specimens l i s t e d i n Table 2 i & ( S T A B L E G R A I N S ) Quartz , Chert , Quartzi te 10\"/ \\10 50. 25 A E I D S P A T H I C 18 / / / A ( K / O S I C A t E N I T E 75, / / / / \\ \\ \\ \\ \\ A \\ I I T H I C A R E N I T E .50 Id spars ( U N S T A B L E G R A I N S ) Unstable Fi ne — Grair.e Rock Fragments -105b-( S T A B L E G R A I N S ) F i g . 9 0 : Q u a r t z y C h e r t , Q u a r t z i t e F e l d s P a r s U n s t a b l e F i n e _ G r a i n e R o c k F r a g m e n t s ( U N S T A B L E G R A I N S ) 106 amounts of matrix, while ancient equivalents (the grey-wackes) have a high matrix content. For discussion of t h i s problem,the reader should refer to Dott,Jr. (I964K L. Sandstone C l a s s i f i c a t i o n : For the purpose of c l a s s i f i c a t i o n , G i l b e r t ' s (1954) scheme was adopted. B r i e f l y , t h i s scheme f i r s t c l a s s i f i e s sandstones into two major groups accourding to the percen-tage of matrix present i n the rocks. Rocks with less than 10 percent matrix are c a l l e d arenites, those con-t a i n i n g 10 to 50 percent matrix are calle d wackes (when matrix exceeds 50 percent, the rock i s then called a mudstone). Further subdivisions are based on some selec-ted e s s e n t i a l components. These components form the corners of the c l a s s i f i c a t i o n triangles ( f i g s . 89 and 90). Quartz, chert, ; and p o l y c r y s t a l l i n e quartz (the \"stable grains\") are grouped i n one corner, feldspars and un-stable fine-grained rock fragments i n the other two cor-ners (the \"unstable grains\"). Therefore, these essen-t i a l components were recalculated to 100 percent for each sample. According to Gi l b e r t ' s c l a s s i f i c a t i o n , seventeen samples are arenites and nine are wackes. Out of the seventeen arenite samples, nine samples are feldspathic arenite, f i v e are arkose, two are quartz arenite, and one i s l i t h i c arenite ( f i g s . 91, 92, and 93). Out of the nine wacke samples, four samples are arkose, two are feldspathic 107 F i g , 91: Photomicrograph of quartz a r e n i t e . Crossed n i c o l s . Vesuvius Bay, S a l t Spring I s l a n d , (V26). F i g . 92: ' Photomicrograph of f e l d s p a t h i c a r e n i t e . Cros-sed n i c o l s . Vesuvius Bay, S a l t Spring Island, (5a). F i g . 93: Photomicrograph of a r k o s i c a r e n i t e . K i s st a i n e d potash f e l d s p a r . Crossed n i c o l s . Mayne I s l a n d . (M4-). 108 wacke, one i s a r k o s i c wacke, one i s l i t h i c wacke, and one i s quartz wacke ( f i g s . 86, 87, and 94). There was no s i g n i f i c a n t v a r i a t i o n i n composition of the sandstones w i t h s t r a t i g r a p h i c p o s i t i o n i n the forma-t i o n . Also such v a r i a t i o n has not been observed l a t e r a l -l y throughout the study area. $. GRAIN SIZE DISTRIBUTION Grain s i z e d i s t r i b u t i o n of f i f t e e n sandstone samples were determined i n t h i n s e c t i o n w i t h the petrographic microscope. The long dimensions of 100 grains were mea-sured i n each of the 1$ t h i n s e c t i o n s . Excluded from these measurements are the g r a i n s f i n e r than 0.03 mm ( i . e . the m a t r i x ) * Figure 96 shows histograms of the g r a i n s i z e d i s t r i b u t i o n of these samples. No attempt was made to convert the t h i n - s e c t i o n s i z e d i s t r i b u t i o n (number) i n t o the s i e v e - s i z e d i s t r i b u t i o n (weight) as was done by Friedman (1958 and 1962), since he d e a l t w i t h w e l l sorted,, q u a r t z - r i c h sandstones. Most of the samples have f a i r s o r t i n g , and the majo-r i t y have the f i n e admixture dominating. Mean g r a i n s i z e of samples taken from A - d i v i s i o n are i n the medium-grained sand range,'those from B-d.ivision samples i n the f i n e -grained sand range, and those from C - d i v i s i o n samples i n the very f i n e - g r a i n e d sand range, ( f i g . 96). 109 a F i g . 94: Photomicrograph of arkosic wacke showing chert rock fragment (C). Crossed n i c o l s . Vesuvius Bay, Salt Spring Is land . F i g . 95: Photomicrograph showing the replacement of grains by the surrounding c l a y - s i z e matr ix. Crossed n i c o l s . Vesuvius Bay, Sa l t Spring Is land. ( 5 c ) . F i g . 97: T i l t compensator used for measurements of paleocurrent d i r e c t i o n s . The scale i s i n inches. Grain Count Per Cent o o o o o o o I I I tt). 5' 3* 3 1 F 5 S e o g o o I I ! I 'I I I I I I T i i i i i i i i i i i i i i r i i I I i i i i i i i O vO cr i IT i r Fig. 9 6 : Histograms of the thin-section frequency d i s t -r i b u t i o n of sandstone framework grains calculated from grain KHMHS size counts i n t h i n section. Numerals r e f e r to specimen numbers. 110 9. D I R E C T I O N A L S T R U C T U R E S AND P A L E O C U R R E N T S A. M e t h o d s T h e o r i e n t a t i o n s o f a l l t h e a v a i l a b l e d i r e c t i o n a l s e d i m e n t a r y s t r u c t u r e s v/ere m e a s u r e d i n t h e f i e l d i n o r d e r t o d e t e r m i n e t h e r e g i o n a l p a l e o c u r r e n t p a t t e r n . B e c a u s e t h e b e d s a r e t i l t e d , c o r r e c t i o n f o r d i p o f t h e m e a s u r e d o r i e n t a t i o n s w a s n e c c e s s a r y t o o b t a i n t h e p r e - t e c t o n i c o r i g i n a l c u r r e n t d i r e c t i o n . T h i s w a s d o n e d i r e c t l y i n t h e f i e l d d u r i n g m e a s u r e m e n t . A t i l t c o m-p e n s a t o r ( f i g . 97) t h a t w a s d e v e l o p e d b y P o u m a (1962, p.25) w a s u s e d i n t h e p r e s e n t s t u d y f o r i n s t a n t r e o r i e n -t a t i o n a n d r e a d i n g o f t h e o r i g i n a l o r i e n t a t i o n o f t h e d i r e c t i o n a l s e d i m e n t a r y s t r u c t u r e s . T h i s c o m p e n s a t o r i s c o m p o s e d o f t w o w o o d e n a r m s ( B o u m a u s e d a n o n - m a g n e t i c m e t a l ) h i n g e d a t o n e e n d . T h e d i m e n s i o n s o f e a c h a r m a r e 6 X 2/3 X 1/3 i n c h . A s p i r i t l e v e l i s m o u n t e d t o o n e a r m . T h e c o m p e n s a t o r i s k e p t h o r i z o n t a l w i t h t h e a r m t h a t h a s t h e s p i r i t l e v e l h e l d a g a i n s t t h e l o w e r b e d d i n g p l a n e ( s o l e o f t h e b e d ) . T h e a r m w i t h t h e s p i r i t l e v e l now i n d i c a t e s t h e s t r i k e o f t h e b e d . T h e n t h e c o m p e n s a t o r i s r o t a t e d u s i n g t h e s p i r i t l e v e l a r m a s a h i n g e l i n e u n t i l t h e o t h e r a r m c o m e s i n c o n t a c t w i t h t h e b e d d i n g p l a n e . N e x t , t h e o t h e r a r m i s a l i g n e d t o c o i n c i d e w i t h o r p a r a l -l e l t o t h e p a l e o c u r r e n t i n d i c a t o r ( e . g . g r o o v e c a s t s , I l l f l u t e c a s t , ... e t c . ) . Then the compensator i s swung back to the h o r i z o n t a l p o s i t i o n using the s p i r i t l e v e l arm as a hinge l i n e . The other arm now i n d i c a t e s the o r i e n t a t i o n of the current i n d i c a t o r before t i l t . Then, using a Brunton compass, t h i s d i r e c t i o n i s measured. The s t r u c t u r e most commonly measured was the f o r e -set l a m i n a t i o n associated w i t h the current ripple, lamina-t i o n of the C - d i v i s i o n . In other p l a c e s , where d i r e c t i -onal sole marks were a v a i l a b l e (e.g. f l u t e casts,- groove c a s t s , and bounce c a s t s ) , the- current d i r e c t i o n , was r e -corded from them and compared with that recorded from the f o r e s e t l a m i n a t i o n w i t h i n the bed. U s u a l l y one reading per bed was recorded by t a k i n g the average d i r e c t i o n of the current i n d i c a t o r s i f there i s any v a r i a t i o n . How-ever, I f the v a r i a t i o n exceeds 2 0 ° , two readings were taken per bed. Due to the s c a r c i t y of w e l l exposed lower bedding surfaces, few measurements of sole markings are-a v a i l a b l e from the study area. B. P r e s e n t a t i o n and I n t e r p r e t a t i o n of Data Rose diagrams of the current d i r e c t i o n s were made f o r the Vesuvius Bay area on S a l t Spring I s l a n d , and i n the Bedwell Harbour area on North Pender I s l a n d ( f i g . c S ) . The numbers w i t h i n the c i r c l e s of the rose diagrams i n d i -cate the number of readings taken i n that p a r t i c u l a r area. Pig. 98 1 1 3 I n t h e o t h e r l o c a l i t i e s s h o w n o n t h e map o f f i g u r e 9 8 , r o s e d i a g r a m s w e r e n o t c o n s t r u c t e d s i n c e o n l y o n e r e a d i n g w a s a v a i l a b l e i n e a c h o f t h e s e l o c a l i t i e s . F i g u r e 98 s h o w s t h a t t h e c u r r e n t s w e r e f l o w i n g f r o m t h e n o r t h w e s t , n o r t h e a s t , stsa±±feh, a n d s o u t h e a s t . T h e c o -i n c i d e n c e i n o r i e n t a t i o n o f t h e t u r b i d i t e ' s d i r e c t i o n a l s t r u c t u r e s a n d t h e o r i e n t a t i o n o f t h e g r a v i t y c o n t r o l l e d s t r u c t u r e s ( s o f t - s e d i m e n t d e f o r m a t i o n s t r u c t u r e s ) w h i c h p r e s u m a b l y m o v e d d o w n s l o p e , s u g g e s t s t h a t t h e t u r b i d i t y c u r r e n t s w e r e a l s o f l o w i n g d o w n t h e p a l e o s l o p e . A n e x a m p l e i s t h e c o i n c i d e n c e i n o r i e n t a t i o n o f t h e f o r e s e t l a m i n a t i o n a s s o c i a t e d w i t h t h e t u r b i d i t e s , a n d t h e o r i e n -t a t i o n o f t h e m i n o r f o l d s o f t h e s o f t s e d i m e n t d e f o r m a -t i o n c a u s e d b y t h e - d r a g o f a t r a c t i o n c a r p e t w h i c h i s g r a v i t y c o n t r o l l e d , - . . A n o t h e r e x a m p l e i s f o u n d , .on t h e s o u t h e r n p a r t o f S a t u r n a I s l a n d , w h e r e t h e o r i e n t a t i o n , o f t h e t u r b i d i t e f o r e s e t l a m i n a t i o n c o i n c i d e s w i t h t h e d i r e c -t i o n o f t h e t h i n n i n g o f t h e p e b b l y m u d s t o n e s e q u e n c e , t h e l a t t e r p r o b a b l y r e s u l t i n g f r o m d o w n s l o p e s l u m p i n g . 114 10,. PALEQGEOGRAPHY A. B a s i n George t r y ; S i n c e t h e t u r b i d i t y c u r r e n t s w e r e a p p a r e n t l y f l o w i n g d o w n t h e s l o p e o f t h e b a s i n , a s c o n c l u d e d i n t h e p r e v i o u s s e c t i o n , i t c a n b e i n f e r r e d t h a t s o m e w h e r e w i t h i n t h e b a s i n t h e r e w e r e s l o p e s w i t h c o n t o u r l i n e s a p p r o x i m a t e l y a t r i g h t a n g l e s t o t h e m e a s u r e d c u r r e n t d i r e c t i o n . T h e c u r r e n t s a s m e a s u r e d o n S a l t S p r i n g , S a t u r n a a n d N n r t h P e n d e r I s l a n d s w e r e f l o w i n g f r o m t h e n o r t h w e s t , n o r t h e a s t , e a s t , a n d s o u t h e a s t , t h e r e f o r e t h e p a l e o s l o p e s o n t h e n o r t h w e s t e r n , n o r t h e a s t e r n , e a s t e r n , a n d s o u t h e a s t e r n p a r t s o f t h e s t u d y a r e a , w e r e d i p p i n g t o t h e s o u t h e a s t , s o u t h w e s t , w e s t , a n d n o r t h w e s t r e s p e c t i v e l y . I f t h e l i n e s o f t h e c u r r e n t d i r e c t i o n s w e r e p r o j e c t e d e a s t w a r d t o t h e o u t e r i s l a n d s , a n d ' n o r m a l s d r a w n -to t h e m , a s l o p e c o n t o u r l i n e t r e n d i n g s o u t h e a s t - n o r t h w e s t w i l l r e s u l t . T h i s c o n t o u r l i n e m i g h t i n d i c a t e t h e s h a p e o f t h e e a s t e r n b o u n d a r y o f t h e b a s i n b u t n o t t h e e a s t e r n l i m i t s , ( i . e . i n d i c a t e s t h e t r e n d o f t h e s h o r e - l i n e , P e t t i J o h n , 1957 , p . 6 0 7 ) . T h i s s l o p e c o n t o u r c o i n c i d e s a p p r o x i m a t e l y i n s h a p e w i t h t h e c o n t o u r s o b t a i n e d f r o m t h e K a o l i n i t e / I l l i t e r a t i o s , ( f i g . 1 9 ) , a n d i t s t r e n d a l s o c o i n c i d e s w i t h t h e s o u t h e a s t - n o r t h w e s t t r e n d o f t h e o u t c r o p s a n d s t r u c t u r e s o f t h e f o r m a t i o n ^ T h e n o r t h e r n a n d s o u t h e r n 115 parts of the basin may be delineated by the termination of the outcrops just south of Nanaimo City to the north-west, and on Sucia and the Orcas Islands to the south and southeast. The Late Cretaceous age of the lower part of the non-marine Chuckanut Formation, (W.S. Hopkins, Jr.., 1966), which was possibly a continental equivalent to the marine Cedar Dist r i c t Formation,, suggests that the shore line of the southeastern part of the basin was somewhere between the mainland of northwestern Washington State and Sucia Island. Paleontological evidence • (J.E. Muller and J.-A. Jeletzky, 1967, and J.E. Muller 1968, personal com-munications) suggests that the basin was opened on i t s western boundaries to the Pacific Ocean. Absence of cur-rents flowing from the west and the south might be due to one or both of the following reasons; (1) there were no turbidity currents flowing from these directions, (2) the regional dip of the basin was to the west,, south-west, and south, therefore turbidity currents.could not flow up the regional dip. From the above, some tentative conclusions may be made regarding the shape and. dimensions of the Cedar Dis-t r i c t basin of deposition. But i t must be emphasized that the available evidence i s sparse and scattered, thus these conclusions' are open to further discussion and 116 m o d i f i c a t i o n . The b a s i n had an e l o n g a t e shape w i t h i t s l o n g e s t a x i s t r e n d i n g s o u t h e a s t - n o r t h w e s t . I t s n o r t h e r n and n o r t h w e s t e r n b o u n d a r i e s may have been l o c a t e d j u s t s o u t h o f t h e c i t y o f Nanaimo and G a b r i o l a I s l a n d , w h i l e t h e s o u t h e r n and s o u t h e a s t e r n b o u n d a r i e s were p r o b a b l y somewhere on the San Juan I s l a n d s between Washington S t a t e n o r t h w e s t e r n c o a s t , and S u c i a and t h e G u l f I s l a n d s . To t h e west i t was open t o t h e P a c i f i c Ocean t h r o u g h t h e p a l e o - Y a n c o u v e r I s l a n d ( s ) . The l o c a t i o n o f t h e e a s t e r n boundary o f the b a s i n i s not known, but i n d i c a t i o n s * o f t h e Nanaimo Group have been t r a c e d on c o n t i n u o u s s e i s m i c p r o f i l e s t o about th e m i d d l e o f t h e S t r a i t o f G e o r g i a , (D.L. T i f f i n , p e r s o n a l communication); a l s o , non-marine Upper C r e t a c e o u s r o c k s were encountered i n two deep w e l l s beneath t h e F r a s e r D e l t a , (W.S, H o p k i n s , J r . , 1 9 6 6 ) . T h e r e f o r e t h e e a s t e r n boundary o f the Cedar D i s t r i c t ba-s i n c o u l d be somewhere between th e B r i t i s h Columbia main-l a n d and Saturna-Mayne-Galiono V a l d e s I s l a n d s i n t h e p r e s e n t day S t r a i t o f G e o r g i a . W.H. Mathews (1958) has r e p o r t e d a t l e a s t 20,000 f e e t o f marine s e d i m e n t a r y r o c k s i n t h e Mount G a r i b a l d i map a r e a o f B r i t i s h C o lumbia, He has d a t e d t h e . l o w e s t and o l d e s t f o r m a t i o n (the Cheakamus Formation) o f t h i s s e -quence as \"mid-Upper C r e t a c e o u s \" . T h e r e f o r e , a t l e a s t 117 parts of the Mount Garibaldi sequence may be correlative with the Cedar Di s t r i c t Formation. It i s not known whether these were deposited i n a separate basin or in a possible northeastward extension of the Nanaimo Basin. B. Dispersal The following facts suggest that the major source area for the sandstone and the coarser elastics was situated to the east and southeast of the study area: (1) Paleocurrent measurements indicate turbidity currents were flowing mainly from the eastern and south-eastern parts of the study area ( f i g . 98). (2) The high percentage of sandstone i n the central, southern, and . southeastern parts of the area relative to i t s very low percentage i n the northern part of the study area. (3) Restriction of the North Pender Island breccia (figs. 30 and 31) and the Saturna Island pebbly mudstone (figs. S and 28) to the south and southeast, and the wedging .out. of the pebbly mudstone toward the northwest, suggest a source from the east, and southeast. The distance to the source area i s d i f f i c u l t to determine, but the occurence of breccia on North Pender Islamd, and the very poorly sorted pebbly mudstone on Saturna Island might Indicate the closeness of the source -118* C 50 A Fig.99: Each group of t u r b i d i t e s i s p l o t t e d on the diagram according to the percentage of beds i n the group begining w i t h A - d i v i s i o n , B - d i v l s i o n , & C - d i v i s i o n . F i e l d 1 corresponds roughly w i t h the lower f l o w regime of Simons & others (1965), and f i e l d s 2 & 3 correspond w i t h the upper f l o w regime, 3 represent-i n g a higher regime than 2. 119 a r e a t o t h e s e p a r t s o f t h e s t u d y a r e a . I n p a r t s o f t h e s e c t i o n s w h i c h w e r e m e a s u r e d i n d e t a i l , a n d i n w h i c h t h e f r e q u e n c y o f o c c u r r e n c e * o f t h e d i f f e r e n t t u r b i d i t e d i v i s i o n s w a s r e c o r d e d , i t w a s f o u n d t h a t 77% of t h e t u r b i d i t e u n i t s s t a r t w i t h C - d i v i s i o n a t t h e i r b a s e ( i . e . t h e s e a r e C t o E t u r b i d i t e u n i t s ) . A d o p t i n g W a l k e r ' s s c h e m e (1967, p . 24, f i g . 4 ) , t h e t u r -b i d i t e s o f t h e C e d a r D i s t r i c t F o r m a t i o n a p p a r e n t l y h a v e b e e n d e p o s i t e d l a r g e l y i n t h e l o w e r f l o w r e g i m e o f S i m o n s e t a l (1965), a s i n d i c a t e d i n f i g . 99. W a l k e r , (1967) c o n s i d e r s t h a t t u r b i d i t e s f o r m e d i n t h e l o w e r f l o w r e g i m e w e r e d e p o s i t e d i n d i s t a l a r e a s r e l a t i v e t o t h e s o u r c e a r e a f o r t h e t u r b i d i t y c u r r e n t s , clue t o t h e r e d u c t i o n i n c u r r e n t v e l o c i t y a w a y f r o m t h e s o u r c e . T h e a u t h o r f e e l s , h o w e v e r , t h a t a n a l t e r n a t i v e i n t e r p r e t a t i o n i s p o s s i b l e ; i f t h e v e l o c i t y o f m o s t . . t u r b i d i t y c u r r e n t s i n a g i v e n a r e a v/ere l o w , t h e n d e p o s i t i o n f r o m t h e m w o u l d b e l a r g e l y w i t h i n t h e l o w e r f l o w r e g i m e , e v e n i n p r o x i m a l a r e a s , . C. P r o v e n a n c e T h e c o m p o s i t i o n o f t h e s a n d s t o n e f r a m e v / o r k i n d i c a t e s v a r i e d r o c k t y p e s i n t h e s o u r c e a r e a . A b u n d a n c e o f q u a r t z , f e l d s p a r ( a n d e s i n e , o l i g o c l a s e , o r t h o c l a s e , a n d m i c r o -c l i n e ) , a n d b i o t i t e i n d i c a t e a c i d i c t o i n t e r m e d i a t e \" p l u -t o n i c a n d / o r \" l o w t o m e d i u m g r a d e m e t a m o r p h i c r o c k s a s 1 2 0 m a j o r s o u r c e r o c k s . T h e common o c c u r r e n c e o f r o c k f r a g -m e n t s , e s p e c i a l l y s e d i m e n t a r y ( s h a l e ) a n d v o l c a n i c r o c k f r a g m e n t s , i n d i c a t e s t h e p r e s e n c e o f s e d i m e n t a r y a n d v o l -c a n i c r o c k s a s s o c i a t e d w i t h t h e a b o v e m e n t i o n e d c r y s t a l -l i n e r o c k s . I t w a s s u g g e s t e d i n t h e p r e v i o u s s e c t i o n t h a t t h e s o u r c e a r e a f o r t h e s a n d s t o n e s w a s t o t h e e a s t a n d s o u t h e a s t . L o o k i n g a t t h e g e o l o g i c map ( G e o l o g i c M ap o f W a s h i n g t o n , 196l) , t h e n e a r e s t l a n d t o t h e e a s t o f t h e s t u d y a r e a i s now l a r g e l y c o v e r e d w i t h p o s t C r e t a c e o u s , r o c k s ( t h e a r e a a r o u n d t h e c i t y o f B e l l i n g h a m ) w h i c h o b s c u r e a p o s s i b l e c r y s t a l l i n e s o u r c e a r e a i H o w e v e r , t h e u l t i m a t e s o u r c e c o u l d b e s t i l l f u r t h e r e a s t , w h e r e p r e -J u r a s s i c l o w g r a d e m e t a m o r p h i c r o c k s a r e e x p o s e d i n t h e C a s c a d e M o u n t a i n s . T o t h e s o u t h e a s t , i n t h e S a n J u a n I s l a n d s , some c r y s t a l l i n e r o c k s a r e e x p o s e d a n d d a t e d a s p r e - C a r b o n i f e r o u s ( G e o l o g i c - Map o f W a s h i n g t o n , 196l) ; t h e s e r o c k s , c o m p o s e d m a i n l y o f q u a r t z d i o r i t e s a n d g n e i s s e s , q u i t e p o s s i b l y y i e l d e d some s e d i m e n t s t o t h e C e d a r D i s t r i c t s a n d s t o n e s . T h e l a r g e t h i c k n e s s o f - t h e f o r m a t i o n , t h e h i g h p e r -c e n t a g e o f s a n d s t o n e ( i . e . l a r g e v o l u m e s o f t h e s a n d -s t o n e ) i n t h e c e n t r a l , s o u t h e r n , a n d s o u t h e a s t e r n p a r t s o f t h e s t u d y a r e a , a n d t h e a n g u l a r i t y o f t h e g r a i n s a l l s u g g e s t t h a t t h e s o u r c e a r e a w a s a n a r e a o f h i g h r e l i e f 121 t h a t h a d u n d e r g o n e r a p i d u p l i f t a n d e r o s i o n * F r e s h n e s s o f t h e f e l d s p a r s f u r t h e r s u g g e s t s a r i d i t y o f t h e s o u r c e a r e a . , w h e r e m e c h a n i c a l w e a t h e r i n g w a s t h e i m p o r t a n t f a c t o r i n b r e a k d o w n o f t h e s o u r c e r o c k s . To t h e n o r t h a n d n o r t h -w e s t , w h e r e s h a l e c o m p o s e s a b o u t 95% o f t h e e x p o s e d s e c -t i o n , i t w a s a s s u m e d t h a t t h e s o u r c e a r e a t o t h e n o r t h w a s a l o w r o l l i n g m u d d y c o a s t a l p l a i n w h e r e t h e r e w e r e n o l a r g e r i v e r s o r e l e v a t e d s o u r c e a r e a s t o s u p p l y c o a r s e m a t e r i a l s ; a l t e r n a t i v e l y , t h e s e p a r t s o f t h e s t u d y a r e a m i g h t h a v e b e e n a d e e p e r p a r t o f t h e b a s i n , m o r e d i s t a n t f r o m t h e s h o r e l i n e s t o t h e e a s t a n d s o u t h e a s t . D i E n v i r o n m e n t o f D e p o s i t i o n T h e f a u n a o f t h e C e d a r D i s t r i c t F o r m a t i o n i n d i c a t e s d e p o s i t i o n i n a m a r i n e e n v i r o n m e n t . A l m o s t a l l p r e v i o u s w o r k e r s h a v e s u g g e s t e d a l i t t o r a l e n v i r o n m e n t f o r i t s d e p o s i t i o n , B r e i t s p r e c h e r ( 1 9 6 2 ) , • c o n c l u d e d , o n t h e b a s i s o f t h e s t u d y o f t h e f o r a m i n i f e r a a n d t h e m e g a f o s s i l f a u n a i n S u c i a I s l a n d , t h a t t h e C e d a r D i s t r i c t F o r m a t i o n w a s d e p o s i t e d i n \" l i t t o r a l t o u p p e r n e r i t i c d e p t h i n t r o p i c a l t o s u b t r o p i c a l w a t e r t e m p e r a t u r e \" . J . E . M u l l e r a n d J . A . J e l e t z k y (1967) s u g g e s t e d n e a r - s h o r e s h a l l o w d e p t h s o f d e p o s i t i o n f o r t h e s h a l e y , f o s s i l i f e r o u s p a r t s o f t h e f o r -m a t i o n , a n d c a l l e d t h e m t h e l i t t o r a l f a c i e s . T h e a b o v e c o u l d b e v a l i d f o r t h e f o s s i l i f e r o u s s h a l e y 122 p a r t s o f t h e f o r m a t i o n , b u t i n o t h e r p a r t s o f t h e s e c t i o n w h e r e t u r b i d i t e s a r e a b u n d a n t , d e p o s i t i o n m u s t h a v e t a k e n p l a c e a t g r e a t e r t h a n l i t t o r a l d e p t h s , i . e . a t d e p t h s b e l o w w a v e b a s e , w h e r e , l a m i n a t i o n a n d c o n v o l u t i o n o f t h e s a n d s t o n e c o u l d b e p r e s e r v e d , ( M u l l e r a n d J e l e t z k y , 1967) T h e u n f o s s i l i f e r o u s s h a l e o f t h e c e n t r a l a n d n o r t h -e r n p a r t s o f t h e s t u d y a r e a w a s d e p o s i t e d . e i t h e r a t a b o u t t h e same d e p t h s a s t h e t u r b i d i t e s , o r i n d e e p e r w a t e r , s i n c e t h i n , - d e l i c a t e , h o r i z o n t a l a n d c r o s s l a m i n a -t i o n s a r e p r e s e r v e d i n t h e s e r o c k s . P a r t i a l s t a g n a n t c o n d i t i o n s a n d r e d u c i n g e n v i r o n -m e n t s i n t h e b o t t o m w a t e r s o f t h e c e n t r a l a n d n o r t h e r n p a r t s o f t h e b a s i n a r e s u g g e s t e d b y t h e a l m o s t c o m p l e t e a b s e n c e o f f o s s i l s i n t h e s e p a r t s o f t h e b a s i n , a n d b y t h e a b u n d a n c e o f p y r i t e a n d c a r b o n a c e o u s m a t t e r i n t h e s h a l e s , s a n d s t o n e s , a n d t h e c a l c a r e o u s c o n c r e t i o n s . Com-p l e t e s t a g n a t i o n a n d t h e d e v e l o p m e n t o f e u x e n i c e n v i r o n -m e n t s w e r e p r o b a b l y p r e v e n t e d b y t w o f a c t o r s . One w a s t h e p e r i o d i c i n t r o d u c t i o n i n t o t h e c e n t r a l p a r t o f t h e b a s i n o f t u r b i d i t y c u r r e n t s w h i c h may h a v e t r a n s p o r t e d o x y g e n a t e d w a t e r i n t o t h i s a r e a . T h e s e c o n d f a c t o r i s t h a t t h e r e w a s a p p a r e n t l y a c o n n e c t i o n b e t w e e n t h e C e d a r D i s t r i c t b a s i n a n d t h e o p e n o c e a n t o t h e w e s t ( U s h e r , 1952; B r e i t s p r e c h e r , 196?; M u l l e r a n d J e l e t z k y , 1967, 123 a n d M u l l e r , 1968^ p e r s o n a l c o m m u n i c a t i o n ) w h i c h m i g h t h a v e s e r v e d t o i n t r o d u c e new w a t e r s t o t h e b a s i n f r o m t h e o p e n o c e a n d u r i n g t i d a l f l u c t u a t i o n s a n d s t o r m s . I n s u m m a r y , t h e n a t u r e a n d a b u n d a n c e o f f o s s i l s , i n t h e l o w e r s h a l e y i n t e r v a l s o f t h e s o u t h e r n a n d s o u t h -e a s t e r n p a r t s o f t h e b a s i n s u g g e s t l i t t o r a l t o u p p e r n e r i t i c d e p t h s , w h e r e w a t e r c o n d i t i o n s w e r e f a v o u r a b l e t o a n i m a l l i f e . . T h e s c a r c i t y o f t h e s e f o s s i l s i n t h e s h a l e y f a c i e s - o f t h e c e n t r a l a n d n o r t h e r n p a r t s d f t h e b a s i n w a s p r o b a b l y d u e t o u n f a v o r a b l e l i v i n g c o n d i t i o n s r e s u l t i n g f r o m p a r t i a l s t a g n a t i o n a n d t h e f o r m a t i o n o f r e d u c i n g e n v i r o n m e n t s ' . T h e o c c u r e n c e o f a b u n d a n t t u r b i -d i t e s i n t h e u p p e r p a r t o f t h e f o r m a t i o n , i n t h e c e n t r a l a n d s o u t h e a s t e r n p a r t s s u g g e s t s a d e e p e n i n g o f t h e b a s i n . 124 11. SUMMARY AND CONCLUSIONS 1. Shale composes about 73% by t h i c k n e s s of the Cedar D i s t r i c t F o r m a t i o n . Sandstone makes the b u l k of the non-shale p a r t . Calcareous c o n c r e t i o n s . a r e present s c a t t e r e d i n the sha les and the sandstones . 2. Two types of shale occurrences are p r e s e n t : a . Continuous sequences of more than 100 f e e t i n t h i c k n e s s , which may or may not be f o s s i l i f e r o u s . b , T h i n beds interbedded w i t h sandstone beds ( i . e . f l y s c h - t y p e s h a l e ) . 3. Among sha les of type (a) above, f o s s i l i f e r o u s s h a l e s are r e s t r i c t e d t o the southeastern p a r t of the study area (Sucia and Saturna I s l a n d s ) , where t h e y . a r e v e r t i c a l l y a s s o c i a t e d w i t h t u r b i d i t e sequences. The un-f o s s i l i f e r o u s shales occur toward the west and northwest (North Pender, S a l t S p r i n g , Mayne, and Vancouver I s l a n d s ) and are l i k e w i s e v e r t i c a l l y a s s o c i a t e d w i t h t u r b i d i t e sequences, except on Vancouver I s l a n d at the northwestern end of the study a r e a , where no t u r b i d i t e s are p r e s e n t . 4'. In the f l y s c h - l i k e sequences, the rhythmic i n t e r b e d d i n g of sandstone and shale beds, and the t y p i c a l t u r b i d i t e s t r u c t u r e s e x h i b i t e d by the sandstones of the Cedar D i s t r i c t F o r m a t i o n , a l l i n d i c a t e t h a t d e p o s i t i o n of 125 the rhythmic (flysch-like) sequences took place by tur-bidity currents* 5. Dominance of the C-E turbidite units, indicates that the deposition of these turbidites took place large-l y within the lower flow regime, 6. Calcareous concretions, most abundant in the shalesj have features suggesting they were formed in the early stages of diagenesis, probably shortly after burial. 7. Paleocurrents, and lithologic l a t e r a l variation indicate that the major source area for the coarse elastics in the Cedar Dist r i c t Formation was situated to the, east and southeast of the study area, 8. Mineral assemblages of the sandstones suggest that the major source rocks were acidic to intermediate plutonic and/or low to medium grade metamorphic rocks. 9. Pre-Jurassic low grade metamorphic rocks of the Cascade Mountains to the east, and the pre-Carboni-ferous crystalline rocks of the San Juan Islands to the -southeast served as possible source areas for the coarse elastics. 10. Composition of the sandstones suggests the major source areas were possibly regions of high r e l i e f that had undergone rapid u p l i f t and erosion. 126 11. Rocks i n the s o u r c e a r e a appear t o have ex-p e r i e n c e d m a i n l y m e c h a n i c a l w e a t h e r i n g . 12. D e p o s i t i o n of t h e s h a l e y , f o s s i l i f e r o u s p a r t s o f t h e f o r m a t i o n t o o k p l a c e i n l i t t o r a l t o upper n e r i t i c d e p t h s . T u r b i d i t e sequences of the f o r m a t i o n were depo-s i t e d i n deeper w a t e r , below the wave base; The un-f o s s i l i f e r o u s s h a l e o f the c e n t r a l and n o r t h e r n p a r t s o f t h e s t u d y a r e a was d e p o s i t e d e i t h e r a t about t h e same depths as the t u r b i d i t e s , o r i n deeper w a t e r , s i n c e t h i n , d e l i c a t e , h o r i z o n t a l and c r o s s l a m i n a t i o n s a r e p r e s e r v e d i n t h e s e r o c k s * 13* P a l e o n t o l o g i c e v i d e n c e s u g g e s t s t h a t d e p o s i t i o n t o o k p l a c e i n a somewhat r e s t r i c t e d b a s i n h a v i n g a narrow c o n n e c t i o n w i t h the open ocean t o t h e west. 14. P a l e o n t o l o g i c and m i n e r a l o g i c e v i d e n c e s sug-g e s t s t h a t t h e bottom c o n d i t i o n s o f the c e n t r a l and n o r t h e r n p a r t s o f the b a s i n o f d e p o s i t i o n were s t a g n a n t and r e d u c i n g , 15* F a c i e s r e l a t i o n s h i p s suggest the b a s i n o f depo-s i t i o n had i t s l o n g e s t d i m e n s i o n t r e n d i n g SE-NW. I t s e a s t e r n , s o u t h e a s t e r n , and s o u t h e r n b o u n d a r i e s were s i t u a t e d between the m a i n l a n d of B r i t i s h Columbia-Washing-t o n and t h e G u l f - S a n Juan I s l a n d s . I t s n o r t h e r n and n o r t h w e s t e r n b o u n d a r i e s were p o s s i b l y near th e c i t y of 127 Nanaimo and G a b r i o l a I s l a n d , To. the west i t was connec-t e d a t l e a s t p a r t i a l l y t o t h e open ocean. 16. I n the s o u t h e a s t e r n p a r t o f t h e s t u d y a r e a , a l t e r n a t i o n o f t h i c k , f o s s i l i f e m u s s h a l e seauenees, and sequences w h i c h a r e p r e d o m i n a n t l y t u r b i d i t e s s u g g e s t s f l u n c t u a t i o n s i n the depth o f the b a s i n f l o o r , e i t h e r due t o changes i n sea l e v e l o r t o t e c t o n i c movements. 17. The Nanaimo Group i n c l u d e s c o a l - b e a r i n g , non-marine r o c k s w h i c h would be c a l l e d a t y p i c a l \"molasse\" by many g e o l o g i s t s . The Cedar D i s t r i c t F o r m a t i o n , how-e v e r , c o n t a i n s t u r b i d i t e sequences w h i c h a re thought by some g e o l o g i s t s t o be t y p i c a l o f \" f l y s c h \" . T h i s j u x t a -p o s i t i o n of u n l i k e f a e i e s r e s u l t s from f 1 u c t u a t i o n s i n wat e r d e p t h d u r i n g d e p o s i t i o n of the Nanaimo Group.-128 12. 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F I R S T COLUMN ( U n i t t h i c k n e s s ) T h i c k n e s s o f e a c h i n d i v i d u a l t u r b i d i t e u n i t i n i n c h e s w a s m e a s u r e d a n d t a b u l a t e d u n d e r t h i s c o l u m n . S i n c e t h e u n i t s h a v e s u r p r i s i n g l y c o n s t a n t t h i c k n e s s l a t e r a l l y , n o a t t e m p t w a s made t o m e a s u r e t h e t h i c k n e s s a l o n g t h e s t r i k e t o o b t a i n a n a v e r a g e t h i c k n e s s . SECOND COLUMN ( T u r b i d i t e u n i t d i v i s i o n s ) T h i s c o l u m n h a s b e e n d i v i d e d i n t o f o u r s u b c o l u m n s , e a c h s u b c o l u m n r e c o r d i n g t h e p r o p e r t i e s o f a s i n g l e d i -v i s i o n . F o r A - d i v i s i o n , t h i c k n e s s , g r a i n s i z e , c a r b o n a t e p r e s e n c e , a n d c o l o r w e r e r e c o r d e d . G r a i n s i z e m e a s u r e m e n t s w e r e made u s i n g a h a n d l e n s ( x l O ) a n d r e c o r d e d a s f o l l o w s : c S : C o a r s e - g r a i n e d s a n d s t o n e mS: M e d i u m - g r a i n e d s a n d s t o n e f S : F i n e - g r a i n e d s a n d s t o n e 136 c Z : C o a r s e - g r a i n e d s i l t s t o n e s Z : S a n d y s i l t C o l o r w a s r e c o r d e d b y u s i n g t h e f o l l o w i n g s y m b o l s : G I G r e y mG: M e d i u m g r e y 1 G : L i g h t g r e y b G : B r o w n i s h g r e y g n G : G r e e n i s h g r e y F o r B - d i v i s i o n , t h e same p r o p e r t i e s a s f o r A - d i v i -s i o n w e r e m e a s u r e d . F o r C - d i v i s i o n , a n e x t r a s u b c o l u m n w a s a d d e d t o r e c o r d t h e t y p e o f s t r u c t u r e e x h i b i t e d b y t h a t d i v i s i o n ; t h e f o l l o w i n g c a t e g o r i e s w e r e l o g g e d : y - F o r e s e t l a m i n a t i o n y / r x A - O v e r s t e e p e n e d f o r e s e t l a m i n a t i o n -\"\"\"^ C u r r e n t r i p p l e l a m i n a t i o n C o n v o l u t e l a m i n a t i o n F o r t h e i n t e r t u r b i d i t e d i v i s i o n ( D E - d i v i s i o n ) , t h i c k n e s s , c a r b o n a t e p r e s e n c e , c o l o r , a n d s t r u c t u r e s w e r e r e c o r d e d ; No a t t e m p t w a s made t o m e a s u r e g r a i n s i z e i n t h e f i e l d , s i n c e a l m o s t a l l o f t h e i n t e r t u r b i d i t e s h a v e s i l t y t o s a n d y - c l a y s i z e . U n d e r s t r u c t u r e s , o n l y o n e s t r u c t u r e w a s r e c o r d e d , t h a t i s p l a n e - p a r a l l e l l a m i n a t i o n ; i t s s y m b o l i s : c 13 7 T H I R D COLUMN ( S e d i m e n t a r y s t r u c t u r e s ) S e d i m e n t a r y s t r u c t u r e s h a v e b e e n d i v i d e d i n t o t w o t y p e s : 1 . B e d d i n g p l a n e s t r u c t u r e s T h e y a r e s e d i m e n t a r y s t r u c t u r e s p r e s e n t o n t h e -b e d d i n g p l a n e . T h e s e w e r e d i v i d e d i n t o p r i m a r y a n d s e c o n d a r y s t r u c t u r e s : a . P r i m a r y s t r u c t u r e s = ^ • 2 = = C h a n n e l l i n g O — z z - F l u t e C a s t s ( l o a d e d ) - r ^ ^ ' G r o o v e C a s t s b . S e c o n d a r y s t r u c t u r e s — ' L o a d C a s t s d-^-* B u r r o w s 7.... B e d i n t e r n a l s t r u c t u r e ( A b e d u s u a l l y i n c l u d e s o n e o r m o r e t u r b i d i t e d i v i s i o n ) . T h e s e s t r u c t u r e s a r e f o u n d w i t h i n t h e b e d , ( e . g . g r a d e d b e d d i n g , d i s t u r b e d b e d d i n g , e t c . ) . ' T h e y a r e c l a s s i f i e d a s p r i m a r y s t r u c t u r e s ( i . e . d e p o s i t i o n a l s t r u c t u r e s ) ; a n d s e c o n d a r y s t r u c t u r e s ( i . e . p o s t - d e p o s i -t i o n a l s t r u c t u r e s ) . T h e f o l l o w i n g s y m b o l s w e r e u s e d : 138 a. P r i m a r y . S t r u c t u r e s D i s t u r b e d b e d d i n g ( c a u s e d b y h i g h d e n s i t y t u r b i d i t y c u r r e n t s ) D e t a c h e d c l a s t s A s a b o v e b u t b e n t C o m b i n a t i o n o f t h e f i r s t a n d s e c o n d C o m b i n a t i o n o f t h e f i r s t , s e c o n d , a n d t h i r d G r a d e d b e d d i n g b . S e c o n d a r y s t r u c t u r e s B u r r o w s C a l c a r e o u s c o n c r e t i o n s w i t h r a n d o m o r i e n t a t i o n W i d e l y s e p a r a t e d c a l c a r e o u s c o n c r e t i o n s e l o n g a t e p a r a l l e l t o b e d d i n g A s a b o v e b u t u s u a l l y i n s t r i n g s m o r e t h a n o n e <£z£> D i s c o n t i n u o u s b e d o f j o i n e d c a l c a r e o u s c o n c r e t i o n s FOURTH COLUMN ( P a l e o c u r r e n t d i r e c t i o n s ) U n d e r t h i s c o l u m n t h e d i r e c t i o n o f p a l e o c u r r e n t s m e a s u r e d f r o m d i r e c t i o n a l s e d i m e n t a r y s t r u c t u r e s w a s r e -c o r d e d . F I F T H COLUMN ( U n i t n u m b e r ) T u r b i d i t e u n i t s w e r e n u m b e r e d i n t h e f i e l d , s t a r t i n g f r o m t h e b a s e o f t h e s e c t i o n w i t h n u m b e r o n e ; t h e n u m b e r s 139 i n c r e a s e u p w a r d i n t h e s e c t i o n . S I X T H C O L U M N ( S p e c i m e n n u m b e r ) T h i s c o l u m n w a s u s e d t o r e c o r d t h e n u m b e r o f t h e s p e c i m e n o r s p e c i m e n s t a k e n f r o m e a c h s e p a r a t e u n i t . S E V E N T H C O L U M N ( P h o t o g r a p h n u m b e r ) T h i s i s t o r e c o r d t h e p h o t o g r a p h n u m b e r t a k e n a t a n y p a r t i c u l a r p o s i t i o n i n t h e m e a s u r e d s e c t i o n . E I G H T H C O L U M N ( N a t u r e o f b e d d i n g ) ' T h e f o l l o w i n g s y m b o l s w e r e u s e d t o d e s c r i b e t h e n a t u r e o f b e d d i n g : N I N T H C O L U M N ( R e m a r k s ) T h i s c o l u m n r e c o r d s o b s e r v a t i o n s o t h e r t h a n t h o s e m e n t i o n e d a b o v e . S u c h o b s e r v a t i o n s i n c l u d e t e c t o n i c s t r u c t u r e s , b e d a t t i t u d e , s k e t c h e s w h e r e p h o t o s p r o v e d t o b e i n a d e q u a t e , a n d t h e r e c o r d i n g o f s o m e p r e l i m i n a r y f i e l d i n t e r p r e t a t i o n s o f t h e m e a s u r e d p r o p e r t i e s . B e d s w h e r e u p p e r a n d l o w e r p l a n e s a r e a l m o s t s t r a i g h t . B e d s w h e r e t h e l o w e r b e d d i n g p l a n e i s u n d u l a t i n g ( d u e t o r i p p l i n g , l o a d i n g o r s o l e m a r k s ) . B e d s w h e r e u p p e r a n d l o w e r b o u n d a r i e s a r e u n d u l a t i n g . S f i H p L E OF T O R B ) * D I T ^ S E Q U E N C E L O S G J U S C H A R T tv c '£ u t> tf c 0 k o 0 0 1 0 a) rt c cl o >-> c J 'E v» <_ s s «-> c Q u u o IG u C -u • t f c 0 -Q L. * J L 0 L. IS •s L. u .e oE 7-N L. tf -o