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UBC Theses and Dissertations

Structural relations between the Shuswap Terrane and the Cache Creek Group in Southern British Columbia. Preto, Vittorio Annibale Giuseppe 1964

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STRUCTURAL RELATIONS BETWEEN THE SHUSWAP TERRANE AND THE CACHE CREEK GROUP IN SOUTHERN BRITISH COLUMBIA t>y VITTORIO ANNIBALE PRETO B.A.Sc., The U n i v e r s i t y of B r i t i s h Columbia, 1962 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n t h e Department of Geology We accept t h i s t h e s i s as conforming t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1964-I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree that p e r -m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s unders tood that c o p y i n g or p u b l i -c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d without my w r i t t e n p e r m i s s i o n . Department of ffieo-^O-~~7T The U n i v e r s i t y of B r i t i s h C o l u m b i a , Vancouver 8, Canada - i i -ABSTRACT The r o c k s of the Shuswap t e r r a n e have been the s u b j e c t of c o n t r o v e r s y f o r more t h a n 65 y e a r s . Jones (1959) r e c e n t l y p r e s e n t e d evidence t h a t i n the Vernon map-area th e o r i g i n a l r o c k s and the superimposed metamorphism are a l l pre-Permian i n age and p r o b a b l y pre-Cambrian. Jones a l s o d e s c r i b e d (1959, pp. 47-4-9 and pp. 28-29) f i v e d i f f e r e n t l o c a l i t i e s where u n c o n f o r m i t i e s s e p a r a t e Shuswap r o c k s o f the Monashee and Chapperon groups from r o c k s of the Cache Creek group o f Permian age. The p r e s e n t w r i t e r mapped i n d e t a i l t h r e e o f t h e s e l o c a l i t i e s , near L a v i n g t o n , at B.X. Creek and at Salmon, R i v e r . Near L a v i n g t o n the c o n t a c t d e s c r i b e d by Jones as an u n c o n f o r m i t y i s c o n s i d e r e d t o be a f a u l t . However, the r e l a t i o n s between metamorphic and non-metamorphic r o c k s are compatible w i t h t h e e x i s t e n c e of an u n c o n f o r m i t y which, i f i t e x i s t s , i s not exposed. At B.X. Creek, the a r c u a t e p a t h d e s c r i b e d by Jones as marking an u n c o n f o r m i t y was found t o f o l l o w a n e a r l y -s t r a i g h t l i n e i n a n o r t h e r l y d i r e c t i o n and t o c o i n c i d e w i t h two p a r a l l e l , s t e e p l y - d i p p i n g and n o r t h - t r e n d i n g f a u l t s which t r u n c a t e t h e non-metamorphic r o c k s . At Salmon R i v e r the evidence f o r an u n c o n f o r m i t y i s s t r o n g . The r o c k s below the u n c o n f o r m i t y are c h l o r i t i c - i i i -and a r g i l l a c e o u s s c h i s t s of t h e Chapperon group and s t r i k e n o r t h e a s t w i t h s t e e p d i p s t o the southeast and northwest. The r o c k s above the u n c o n f o r m i t y a r e c a l c a r e n i t e s , f e l d -s p a t h i c v o l c a n i c wackes and t u f f s g r a d i n g upward i n t o a r g i l l i t e s , and have been d e s c r i b e d by Jones as p a r t of the Cache Creek group; t h e y s t r i k e n o r t h or s l i g h t l y east of n o r t h and d i p g e n t l y t o the west or west-northwest. - x i -ACKNOWLEDGMENT The w r i t e r wishes t o acknowledge a l l the h e l p r e c e i v e d i n the p r e p a r a t i o n o f t h i s t h e s i s . Dr. W.H. White suggested the problem and out-l i n e d t he work t o be done. Dr. J.V. Ross and Dr. W.R. Danner a s s i s t e d and h e l p e d the w r i t e r on v a r i o u s o c c a s i o n s . The Department o f Geology o f the U n i v e r s i t y o f B r i t i s h Columbia p r o v i d e d s u f f i c i e n t funds needed f o r f i e l d expenses, a e r i a l photographs and r o c k s e c t i o n i n g . S p e c i a l thanks are due t o Dr. K.C. McTaggart, who c o n s t a n t l y a s s i s t e d i n the work, v i s i t e d the w r i t e r i n the f i e l d , r e a d the m a n u s c r i p t , and p r o v i d e d much c o n s t r u c t i v e c r i t i c i s m . - i v -TABLE OF CONTENTS Page ACKNOWLEDGMENT CHAPTER I - INTRODUCTION I L o c a t i o n 1 I I C l i m a t e and V e g e t a t i o n 3 I I I P r e v i o u s G e o l o g i c a l Work 3 IV G e n e r a l Geology 4 V The Shuswap Problem 6 VI Purpose o f the Pr e s e n t I n v e s t i g a t i o n 10 V I I Methods Used 10 V I I I D i f f i c u l t i e s E n c o u n tered 11 CHAPTER I I - KEEFER GULCH AREA I G e n e r a l D e s c r i p t i o n 12 I I Metamorphic Rocks. Sub-areas 1 and 2 .... 13 (a) L i t h o l o g y ... .• 13 (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s 20 (1) S t r a t i g r a p h y 20 (2) P l a n a r s t r u c t u r e s 21 (3) L i n e a r s t r u c t u r e s 22 ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s 22 (d) T e n t a t i v e C o r r e l a t i o n 25 I I I I n t r u s i v e Rocks . 26 (a) P o r p h y r i t i c b i o t i t e m i c r o d i o r i t e ... 26 (b) F e l d s p a r p o r p h y r y 28 ( c ) Lamprophyre 29 (d) Diabase 29 (e) A p l i t e and q u a r t z - f e l d s p a r pegmatite 29 XV Non-Met amorphic Rocks 30 (a) Sub-area 3 31 (1) L i t h o l o g y 31 (2) I n t e r n a l s t r u c t u r a l r e l a t i o n s 35 (b) Sub-area 4 38 (1) L i t h o l o g y 38 (2) I n t e r n a l s t r u c t u r a l r e l a t i o n s 41 - V -TABLE OP CONTENTS (Continued) Page ( c ) Sub-area 5 4-2 (1) L i t h o l o g y 42 (2) I n t e r n a l s t r u c t u r a l r e l a t i o n s 4-5 (d) E x t e r n a l s t r u c t u r a l r e l a t i o n s .... 46 (e) C o r r e l a t i o n and Age 48 V The " K e e f e r G u l c h Unconformity" 48 CHAPTER I I I - B.X. CREEK AREA I G e n e r a l D e s c r i p t i o n 50 I I Metamorphic r o c k s 51 (a) L i t h o l o g y 51 (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s .... 52 ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s .... 55 (d) C o r r e l a t i o n 53 I I I Non-met amorphic r o c k s 53 (a) L i t h o l o g y 53 (b) I n t e r n a l s t r u c t u r a l . r e l a t i o n s .... 55 ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s .... 56 (d) C o r r e l a t i o n and Age 56 IV I n t r u s i v e r o c k s 56 V The "B.X. Creek Unconformity" 57 CHAPTER IV - SALMON RIVER AREA I G e n e r a l D e s c r i p t i o n 59 I I Metamorphic r o c k s 59 (a) L i t h o l o g y 59 (1) Chapperon group 59 (2) O l d Dave I n t r u s i v e s 63 (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s ......, 64 ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s .... . 64 (d) C o r r e l a t i o n . a n d Age 66 - v i -TABLE OP CONTENTS (Continued) Page I I I Non-met amorphic r o c k s 66 (a) L i t h o l o g y 66 (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s .... 72 ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s .... 73 (d) T e n t a t i v e C o r r e l a t i o n and Age .... 74-IV Young I n t r u s i v e Rocks 77 (a) L i t h o l o g y 77 (1) Hornblende M i c r o d i o r i t e .... 78 (2) L a t i t e Porphyry "78 (3) . A l a s k i t e 79 (b) Age 81 CHAPTER V - SUMMARY AND CONCLUSIONS 82 BIBLIOGRAPHY 84--r v i i - -ILLUSTRATIONS F i g u r e Page 1. Salmon R i v e r Unconformity "between r o c k s of the Ghapperon and Cache Creek groups F r o n t i s p i e c e 2. Index showing l o c a t i o n of the areas mapped 3 3. K e e f e r G u l c h , sub-area 1. Quartz b o u d i n i n h i g h l y - d e f o r m e d a r g i l l a c e o u s s c h i s t . P i c t u r e t a k e n l o o k i n g n o r t h -west 14 4-. K e e f e r G u l c h , sub-area 2. Hornblende p o r p h y r o b l a s t i n q u a r t z - b i o t i t e -hornblende s c h i s t . C r o s s e d n i c o l s (X 15) 15 5. K e e f e r G u l c h , sub-area 2. Composi-t i o n a l l a y e r i n g p a r a l l e l i n g s c h i s t o s i t y i n h o r n b l e n d e - b i o t i t e - q u a r t z s c h i s t . P.P.L. (X 15) 16 6. K e e f e r G u l c h , sub-area 1. S c h i s t o s i t y i n c h l o r i t e - h o r n b l e n d e s c h i s t . P.P.L. (X 4-5) 17 7. E q u a l - a r e a lower-hemisphere p r o j e c t i o n of p o l e s t o s c h i s t o s i t y and of l i n e -a t i o n s i n sub-area 1 a t K e e f e r G u l c h 18 8. E q u a l - a r e a lower-hemisphere p r o j e c t i o n of p o l e s t o s c h i s t o s i t y and of l i n e -a t i o n s i n sub-area 2 at K e e f e r G u l c h 19 9. K e e f e r G u l c h , M y l o n i t e from the f a u l t s e p a r a t i n g sub-areas 1 and 3. 1/20 i n c h s c a l e 23 10. K e e f e r G u l c h , sub-area 1. Myrmekite s u r r o u n d i n g a l a b r a d o r i t e p henocryst i n p o r p h y r i t i c b i o t i t e m i c r o d i o r i t e . C r o s s e d n i c o l s (X 45) 27 - v i i i -ILLUSTRATIONS (Continued) F i g u r e Page 11. K e e f e r G u l c h , sub-area 3- C r i n o i d fragment i n gray l i m e s t o n e . Needle i s yi i n c h l o n g 32 12. K e e f e r G u l c h , sub-area 3. Rock fragment c o n t a i n i n g d e v i t r i f i e d shards i n l i t h i c v o l c a n i c wacke. P.P.L. X 45 33 13. K e e f e r G u l c h , sub-area 3. V o l c a n i c conglomerate. Needle i s 1 i n c h l o n g .... 34 14. K e e f e r G u l c h , sub-area 3. V o l c a n i c conglomerate. 1/20 i n c h s c a l e 35 15. E q u a l - a r e a lower-hemisphere p r o j e c t i o n o f bedding a t t i t u d e s i n sub-area 3 at K e e f e r G u l c h 37 16. K e e f e r G u l c h , sub-area 4 . I n t e r g r o w i n g a c t i n o l i t e c r y s t a l s i n micaceous a c t i n o l i t e p o r p h y r y . C r o s s e d n i c o l s (X 15) 38 17. K e e f e r G u l c h , sub-area 5* Bent f e l d s p a r c r y s t a l i n v o l c a n i c wacke. C r o s s e d n i c o l s (X 4 5 ) . 43 18. K e e f e r G u l c h , sub-area 5« Graded bedding i n v o l c a n i c wacke. Paper c l i p i s 1 i n c h l o n g 44 19. B.X. Creek. Sheared f e l d s p a t h i c v o l c a n i c wacke. P.P.L. (X 15) 54-20. B.X. Creek. Sheared f e l d s p a t h i c v o l c a n i c wacke. P.P.L. (X 15) 55 21. B.X. Creek. Quartz phenocryst w i t h r e s o r b e d b o r d e r s i n s e r i c i t i z e d a l a s k i t e p o r p h y r y . C r o s s e d n i c o l s (X 15). 57 0 - i x -ILLUSTRATIONS (Continued) F i g u r e Page 22. Salmon R i v e r U nconformity. Blue p e n c i l p a r a l l e l s d i p d i r e c t i o n of s c h i s t o s i t y i n Chapperon r o c k s ; r e d p e n c i l p a r a l l e l s d i p d i r e c t i o n of e r o s i o n s u r f a c e 60 23. Salmon R i v e r . H i g h l y deformed . s i l i c e o u s a r g i l l a c e o u s s c h i s t . Paper c l i p i s 1 i n c h l o n g . 61 24. Salmon R i v e r . Quartz l e n s e s i n ...... s i l i c e o u s s c h i s t . C r o s s e d n i c o l s (X 15) 62 25. Salmon R i v e r . S t r a i n - s l i p c l e a v a g e i n m i c a c e o u s - a r g i l l a c e o u s s c h i s t . P.P.L. (X 15). 63 26. E q u a l - a r e a lower-hemisphere p r o -j e c t i o n of p o l e s t o s c h i s t o s i t y and of minor f o l d axes i n Chapperon group r o c k s at Salmon R i v e r 65 27. Salmon R i v e r . C r i n o i d p l a t e s i n c a l c a r e n i t e . . P.P.L. (X 45) 67 28. Salmon R i v e r . V i t r i c c r y s t a l t u f f , P.P.L. (X 15) 69 29. E q u a l - a r e a lower-hemisphere p r o -j e c t i o n of p o l e s t o ..bedding i n non-metamorphic r o c k s at Salmon R i v e r . ... 71 30. Salmon R i v e r . .Twinned hornblende phe n o c r y s t r e p l a c e d by c a l c i t e and e p i d o t e i n hornblende m i c r o d i o r i t e . C r o s s e d n i c o l s . ( X 4 5 ) . 77 31. Salmon R i v e r . Combination t w i n n i n g of andesine p h e n o c r y s t s a c c o r d i n g t o t h e c a r l s b a d law i n l a t i t e p o r phyry. C r o s s e d n i c o l s (X 15) 79 - X -ILLUSTRATIONS (Continued) F i g u r e Page 32. Salmon R i v e r . Quartz p h e n o c r y s t s w i t h embayed b o r d e r s , and myrme-k i t i c groundmass i n p o r p h y r i t i c a l a s k i t e . C r o s s e d n i c o l s . (X 45) 80 P l a t e I Map of K e e f e r G u l c h a r e a I n pocket I I Map o f B.X. Creek a r e a I n pocket I I I Map of Salmon R i v e r a r e a I n pocket 1 Salmon R i v e r Unconformity "between r o c k s of the Chapperon and Cache Creek groups - 1 -CHAPTER I - INTRODUCTION I Location Jones (1959, pp. 28-29 and pp. 47-49) describes unconformities between Shuswap and younger rocks at five different l o c a l i t i e s . The present writer has mapped three of these l o c a l i t i e s on a large scale. The Keefer Gulch area i s located approximately two miles west of Lavington, on the north side of Coldstream Valley, which runs east from Vernon to Lumby. More precisely, the area comprises both sides of a small valley, which descends into Coldstream Valley from the north and i s l o c a l l y known as "Keefer Gulch". The area covers about three square miles. The B.X. Creek area l i e s three miles northeast of Vernon, on the northwest side of B.X. Creek, and covers about 2.3 square miles, on and around a low h i l l , henceforth referred to as B.X. H i l l . The l o c a l i t y can be reached from Vernon by the Silver Star Mountain road. The Salmon River area, 12.2 miles west of Westwold and approximately 30 miles northwest of Vernon, covers about one square mile. It l i e s on both sides of the Salmon River Valley, where the motor road that joins Westwold to Douglas Lake crosses the Salmon River on two bridges that are about a quarter of a mile apart. - 3 -I I C l i m a t e and V e g e t a t i o n The K e e f e r G u l c h and B.X. Creek areas are l o c a t e d i n t h e immediate v i c i n i t y o f Okanagan Lake and are i n c l u d e d i n the "dry "belt" of C e n t r a l B r i t i s h Columbia. Y e a r l y p r e c i p i t a t i o n i s meager h e r e , summers are hot and d r y , and w i n t e r s are c o l d . The lower p o r t i o n s of t h e v a l l e y s , where not i r r i g a t e d and c u l t i v a t e d , are e i t h e r d e v o i d of t i m b e r or s p a r s e l y d o t t e d w i t h ponderosa p i n e ( w e s t e r n y e l l o w p i n e ) . The low v e g e t a t i o n i s c h a r a c t e r i z e d by patches of low bushes, sagebrush, t h o r n s and s m a l l c a c t u s . The upper p o r t i o n s of t h e v a l l e y s and t h e upper p l a t e a u s are c o v e r e d by dense t i m b e r , i n c l u d i n g Douglas f i r , l o d g p o l e p i n e and aspen. The Salmon R i v e r a r e a i s l o c a t e d immediately t o the west o f the "dry b e l t " , i n a m o i s t e r r e g i o n . V e g e t a t i o n i s c h a r a c t e r i z e d by dense c o n i f e r f o r e s t w i t h patches o f aspen and w i l l o w . I I I P r e v i o u s G e o l o g i c a l Work The t h r e e areas mapped are w i t h i n the Vernon map sheet (see G.S.C. map 1059A). E a r l i e s t accounts of g e o l o g i c a l mapping i n t h i s g e n e r a l r e g i o n are by G.M. Dawson (1878, 1879) and by R.A. D a l y (1911, 1915). More r e c e n t work was begun i n 194-5 by H.M.A. R i c e , and completed i n 1951 by A.G. Jones who i n 1959 summarized - 3 -(From B . C . Dept. of L a n d s a n d Forests Topo. M a p ) F i g . 2 Index showing l o c a t i o n of the areas mapped. - 4- -h i s s t u d i e s i n G.S.C. Memoir 296, the most r e c e n t r e p o r t a v a i l a b l e on t h i s a r e a . IV G e n e r a l Geology About t w o - t h i r d of the Vernon map sheet i s under-l a i n by a s e r i e s o f g e n e r a l l y high-grade metamorphic r o c k s which were f i r s t named "Shuswap S e r i e s " by Dawson i n 1877-78. T h i s term was l a t e r extended by D a l y (1911, p. 167) t o i n c l u d e a l l " P r e - B e l t i a n r o c k s i n the a r e a " . D a l y a l s o s t a t e d t h a t metamorphism i n the s e r o c k s had been produced by "deep b u r i a l under Pre-Cambrian sediments o r v o l c a n i c s " . I n h i s r e c e n t account, Jones (1959, p. 9) used "the term 'Shuswap' as a s t r a t i g r a p h i c unit....much as Dawson i n t e n d e d i t " . Jones a s s i g n e d t o the Shuswap r o c k s a pre-Oambrian and p o s s i b l y pre-Windermere age, and d i v i d e d them i n t o t h r e e major groups whose s t r a t i g r a p h i c r e l a t i o n t o one another i s u n c e r t a i n . A t the bottom of h i s s t r a t i g r a p h i c column, Jones put the Monashee group, composed l a r g e l y o f high-grade g n e i s s and s c h i s t and a s m a l l amount o f marble, d o l o m i t e , s l a t e and p h y l l i t e . The group u n d e r l i e s p r a c -t i c a l l y a l l the e a s t e r n h a l f o f the Vernon map-sheet, and was e s t i m a t e d t o be at l e a s t 50,000 f e e t t h i c k . The Mount Ida group, a p p r o x i m a t e l y 60,000 f e e t t h i c k and s u b d i v i d e d i n t o s i x f o r m a t i o n s , was thought t o o v e r l i e t h e Monashee group. Mount Ida r o c k s u n d e r l i e most o f the n o r t h w e s t e r n q u a r t e r of the Vernon sheet and i n c l u d e - 5 -sedimentary and v o l c a n i c r o c k s which had g e n e r a l l y "undergone low-grade metamorphism, r e s u l t i n g i n t h e development of c h l o r i t e and s e r i c i t e s c h i s t s from v o l c a n i c and c e r t a i n sedimentary r o c k s " ( J o n e s , 1959» p. 18). The Chapperon group, which i n the southwestern c o r n e r of t h e map-area forms a northward t r e n d i n g b e l t o f r o c k s a p p r o x i m a t e l y $0 m i l e s l o n g and one t o s i x m i l e s wide, was p r o v i s i o n a l l y a s s i g n e d by Jones t o t h e t o p of t h e Shuswap T e r r a n e . T h i s group, at l e a s t 5»000 f e e t t h i c k , c o n s i s t s of a r g i l l i t e , low-grade s c h i s t , q u a r t z i t e and l i m e s t o n e . Jones remarks (op. c i t . , p. 30) t h a t the r o c k s of t h e Chapperon group have " l i t h o l o g y and metamorphism s i m i l a r t o t h o s e o f the E a g l e Bay f o r m a t i o n " , t h e uppermost f o r m a t i o n of t h e Mount Ida group, and t h a t (op. c i t . , p. 28) "the t o p of the group i s marked i n two p l a c e s by an u n c o n f o r m i t y at which Permian r o c k s of t h e Cache Creek group o v e r l i e Chapperon group r o c k " . The u n c o n f o r m i t y mentioned above i s s t a t e d by Jones t o mark th e top o f the Shuswap T e r r a n e and, i n the w e s t e r n h a l f of the Vernon map-area, t o s e p a r a t e Shuswap r o c k s of Archaean age from Cache Creek group r o c k s o f Permian age. - 6 -V The Shuswap problem G.M. Dawson (1879, pp. 96B-101B), d e s c r i b e d t h e r o c k s of t h e Shuswap t e r r a n e as p a r t o f an Archaean meta-morphic complex, t h e r e l a t i o n s of which t o the o v e r l y i n g s t r a t a were not c l e a r . He mentioned a remarkable p a r a l l e l i s m i n t r e n d between the s e r o c k s and the o v e r l y i n g s t r a t a , but he s u s p e c t e d t h a t t h i s apparent c o n f o r m i t y might have been produced by i n t e n s e f o l d i n g . I n 1904 R.G. McConnell and R.W. Brock p u b l i s h e d an account of t h e geology o f t h e West Kootenay Map Sheet and suggested t h a t i n t h i s a r e a t h e r o c k s t h e y mapped as Shuswap s e r i e s were " h i g h l y metamorphosed members of the P a l e o z o i c f o r m a t i o n s o c c u r r i n g i n t h i s d i s t r i c t " . T h i s c o n c e p t i o n was c h i e f l y due t o t h e f a c t t h a t the authors noted a g r a d a -t i o n from high-grade metamorphic r o c k s i n t o lower-grade r o c k s and f i n a l l y i n t o p r a c t i c a l l y unmetamorphosed s t r a t a , thought t o be o f P a l e o z o i c age. I t was h e r e , t h e n , t h a t t h e s u g g e s t i o n was f i r s t made t h a t the metamorphism of "Shuswap Rocks" might have been i n d u c e d by i n t r u s i o n s o f any age and t h a t such r o c k s are not n e c e s s a r i l y Archaean. I n 1911-1912, R.A. D a l y v i s i t e d t h e a r e a and examined r o c k s a l o n g the Canadian P a c i f i c R a ilway near Shuswap Lakes. He d e s c r i b e d a l o c a l i t y at A l b e r t Canyon where "...the o l d e s t f o r m a t i o n of the B e l t i a n system i s a q u a r t z i t i c sandstone, r e s t i n g unconformably on t h e - 7 -Shuswap T e r r a n e . . . " (1915, p. 6 2 ) . A few l i n e s f u r t h e r , however, he a l s o s t a t e d t h a t "...the b a s a l sandstone i s f e l d s p a t h i c and has been changed i n t o a s c h i s t o s e , mica-ceous r o c k which resembles the u n d e r l y i n g o r t h o g n e i s s r a t h e r c l o s e l y . . . t h e sand becomes more and more qu a r t z o s e f u r t h e r up from t h e g n e i s s . . . " . From a s u i t e o f specimens t a k e n by t h a t w r i t e r at v a r i o u s p o i n t s i n the s e c t i o n , i t appears t h a t the t r a n s i t i o n from o r t h o g n e i s s t o q u a r t z i t e (80 p e r c e n t q u a r t z , 13 p e r c e n t f e l d s p a r , 5 p e r c e n t b i o t i t e ) o c c u r s over a s t r a t i g r a p h i c d i s t a n c e o f 300 t o 350 f e e t . I n one of h i s r e p o r t s , D a ly a l s o d e s c r i b e s the metamorphism of the Shuswap r o c k s as " s t a t i c " o r " l o a d metamorphism", produced by deep b u r i a l under pre-Oambrian sediments (1911, p. 168). In 1913 S . J . S c h o f i e l d ( p . 136) d e s c r i b e d B e l t i a n s t r a t a at Crawford Bay, on Kootenay Lake, and s t a t e d t h a t at Crawford Creek t h e y "...appear t o pass conformably underneath the Shuswap s e r i e s . I f t h i s be t r u e , t h i s a r e a o f so c a l l e d Shuswap r o c k s does not b e l o n g t o the p r e -B e l t i a n , but i s a metamorphosed d i v i s i o n o f B e l t i a n r o c k s . . . " He l o c a l l y d e s c r i b e d t he metamorphism t o be connected t o i n t r u s i o n s o f the West Kootenay (Nelson) B a t h o l i t h o f pr o b a b l e J u r a s s i c age. I n 1928 H.C. Gunning v i s i t e d D a l y ' s l o c a l i t y o f the A l b e r t Canyon u n c o n f o r m i t y and r e p o r t e d : " . . . F r e s h g r a n i t e dykes t h a t c u t the g n e i s s e s , a l s o c u t the o v e r l y i n g sediments. No u n c o n f o r m i t y - 8 -was noted. The g n e i s s e s a re e x a c t l y s i m i l a r t o those encountered elsewhere i n t h e g r a n i t e -gneiss- s e d i m e n t complex. The i n t i m a t e manner i n which t h e g n e i s s e s a re i n t e r b e d d e d w i t h the sediments i n d i c a t e s t h a t t h e y have been formed by replacement and i n j e c t i o n of the sediments by a g r a n i t i c magma..." (op. c i t . , p. 150A). I n 1929, 1930 and 1931 C E . C a i r n e s (1932, pp. 66-109) worked i n the n o r t h e r n Okanagan r e g i o n , where he found Cache Creek and u n d e r l y i n g K i s c o n l i t h beds ( t h e l a t t e r had p r e v i o u s l y been t e n t a t i v e l y c l a s s e d as Cambrian by Dawson and as p r e - B e l t i a n o r Archaean by D a l y ) t o be e q u a l l y deformed and t o be a f f e c t e d by metamorphic p r o c e s s e s i n t h e v i c i n i t y of c o n t a c t s w i t h Shuswap-type r o c k s . C o n t a c t s o f the above s t r a t a w i t h the g n e i s s e s appeared t o the auth o r t o be m o s t l y g r a d a t i o n a l , except i n p l a c e s where the Shuswap c o n s i s t e d o f massive g r a n i t i c r o c k s , which appeared t o be i n t r u s i v e . I n 1934- B.B. Brock (pp. 673-699) examined a r e l a t i v e l y s m a l l a r e a immediately south o f Kelowna, on t h e east shore o f Okanagan Lake. There he found e v i d e n c e o f doming of Shuswap g n e i s s e s by an i n t r u s i v e g r a n i t i c body. From h i s i n v e s t i g a t i o n he concl u d e d t h a t t h e metamorphism of Shuswap r o c k s has been caused by upward t h r u s t i n g o f g r a n i t i c magma en-masse, which produced doming of t h e s t r a t a , alinement of m i n e r a l s p a r a l l e l t o t h e d i r e c t i o n o f s t r e t c h i n g , and i n j e c t i o n o f innumerable s i l l s of o r t h o -g n e i s s i n the invaded r o c k s . He c o n s i d e r e d the metemorphism - 9 -to be a dynamic process, and related i t to igneous intrusions of possible post-Triassic age. The suggestion of dynamic metamorphism was supported by G i l l u l y (1934), whose contri-bution i s based on a petro-fabric study carried out on two specimens, one of schist and one of gneiss, from Daly's unconformity l o c a l i t y at Albert Canyon. In 1939, C E . Cairnes, i n summarizing his inv e s t i -gations on the problem, concluded that the metamorphism of the Shuswap rocks i s "a relatively recent event i n the geological history of this terrane". He stated (1939, p. 269) that the metamorphic changes are connected to the intrusion of Mesozoic plutons. These intrusions were char-acterized by "a process of gradual soaking of the superin-cumbent rocks", so as to produce, i n most places, relatively mild deformation. By such a process he explained the generally e l l i p t i c a l shape of bodies of Shuswap gneisses and their gradational contacts with overlying rocks. Regarding the age of the gneisses he stated (op. c i t . , p. 270) that near Shuswap Lakes the formations affected by the metamorphism are probably of pre-Cambrian (Beltian) age, but that i n other areas the metamorphism extended, even i f i n a milder form, into Late Paleozoic and probably Triassic formations. In 1959 A.G. Jones presented evidence that i n the Vernon map-area the Shuswap rocks, the superimposed meta-- 10 -morphism, and the accompanying minor g r a n i t i c i n t r u s i o n s are a l l o f pre-Permian and p o s s i b l y o f pre-Cambrian age. He s u b d i v i d e d the Shuswap T e r r a n e i n t o t h r e e groups the Monashee, the Mount Ida and the Chapperon group, which he c o n s i d e r e d t o be s e p a r a t e d by an u n c o n f o r m i t y from the o v e r l y i n g Cache Creek s t r a t a of Permian age* VI Purpose o f the p r e s e n t i n v e s t i g a t i o n I t i s the purpose of t h i s i n v e s t i g a t i o n t o d e s c r i b e i n d e t a i l t h r e e areas where the u n c o n f o r m i t y between Shuswap and Cache Creek r o c k s was d e s c r i b e d by Jones. V I I Methods Used The t h r e e areas mapped were chosen from Jones' d e s c r i p t i o n s of the l o c a l i t i e s at which the u n c o n f o r m i t y had been found. F i e l d mapping was c a r r i e d out by t h i s w r i t e r between May 6 and May 30, 1963, u s i n g a e r i a l photographs at a s c a l e of a p p r o x i m a t e l y f o u r i n c h e s e q u a l one m i l e and two i n c h e s e q u a l one m i l e . Base maps of the areas at a s c a l e of one i n c h equal 1,000 f e e t and one i n c h e q u a l 500 f e e t and w i t h 100-foot c o n t o u r i n t e r v a l s were a l s o used, and the e l e v a t i o n s o f most p o i n t s were checked w i t h an a l t i m e t e r k i n d l y l o a n e d by the U n i v e r s i t y of B r i t i s h Columbia, De-partment of Geography. - 11 -V I I I D i f f i c u l t i e s encountered The main d i f f i c u l t y encountered w h i l e mapping was t h e s c a r c i t y and s p o t t i n e s s o f exposures. T h i s problem was most acute at B.X. Creek. Here the low h i l l , around which t h e mapping was done, i s l a r g e l y c o v e r e d by g l a c i a l d r i f t and the few exposures are v e r y s m a l l , low, and s c a t t e r e d . The g e o l o g i c a l i n f o r m a t i o n t h a t c o u l d be g a t h e r e d was t h e r e f o r e inadequate and too s p o t t y t o permit a c o n v i n c i n g s y n t h e s i s of the s t r u c t u r a l p i c t u r e . Exposures were a l s o s c a r c e i n p l a c e s a t K e e f e r G u l c h , but the problem here was not as acute,as at B.X. Creek. At the Salmon R i v e r l o c a t i o n r o c k exposures were found t o be common along the r i v e r , i n r o a d c u t s , and on s t e e p b l u f f s , but a s h o r t d i s t a n c e away from the v a l l e y bottom, t o , t h e northwest and s o u t h e a s t , they are masked by a t h i c k c o v e r of u n c o n s o l i d a t e d g l a c i a l and f l u v i o - g l a c i a l m a t e r i a l . - 12 -CHAPTER I I - KEEPER GULCH AREA I G e n e r a l D e s c r i p t i o n The a r e a i s l o c a t e d two m i l e s west of L a v i n g t o n , and comprises b o t h s i d e s of a s m a l l v a l l e y which descends i n t o C o l d s t r e a m V a l l e y from t h e n o r t h , and which i s l o c a l l y known as " K e e f e r G u l c h " . A network of l o g g i n g r o a d s , which c o v e r s the n o r t h e r n p o r t i o n o f the a r e a , i s connected w i t h highway No. 6 t o the south by a jeep r o a d which runs a l o n g the bottom o f the g u l c h . The s o u t h e r n p a r t of the a r e a c o n s i s t s o f b a r r e n open s l o p e s , s p a r s e l y d o t t e d w i t h p i n e and aspen, but the bottom of t h e g u l c h and the n o r t h e r n p a r t o f the ar e a are h e a v i l y t i m b e r e d w i t h p i n e , f i r and c e d a r , and c o v e r e d by dense unde r b r u s h . G l a c i a l and f l u v i a t i l e d r i f t c o v e r i s e x t e n s i v e . Rock exposures are common on s t e e p s l o p e s , e s p e c i a l l y i n the s o u t h e r n p o r t i o n o f the a r e a , but are s m a l l and w i d e l y s c a t t e r e d on t h e g e n t l e upper s l o p e s and i n the h e a v i l y t i m b e r e d n o r t h e r n p o r t i o n of the a r e a . The w e s t e r n and s o u t h e r n p a r t o f the a r e a (see p l a t e I ) are u n d e r l a i n by low-grade s c h i s t s , the f o l i a t i o n o f which s t r i k e s e a s t e r l y and d i p s moderately t o the so u t h . S e v e r a l dykes cut these metamorphic r o c k s . The n o r t h -e a s t e r n p o r t i o n o f the ar e a i s u n d e r l a i n by unmetamorphosed v o l c a n i c wackes and b r e c c i a s w i t h i n t e r b e d s o f l i m e s t o n e , of p r o b a b l e Upper P a l a e o z o i c age. - 13 -Jones (1959) suggested t h a t an u n c o n f o r m i t y s e p a r a t e s metamorphic and non-metamorphic r o c k s . The p r e s e n t w r i t e r mapped the a r e a i n d e t a i l and found t h a t the two groups of r o c k s are s e p a r a t e d by a s e r i e s of s t e e p l y d i p p i n g f a u l t s which s t r i k e n o r t h e a s t e r l y and e a s t e r l y . F i v e f a u l t b l o c k s have been d i s t i n g u i s h e d and w i l l be con-s i d e r e d s e p a r a t e l y . I I Metamorphic Rocks Sub-areas 1 and 2 (a) L i t h o l o g y Metamorphic r o c k s u n d e r l i e sub-areas 1 and 2. They c o n s i s t of a conformahle sequence of low-grade micaceous and p h y l l i t i c s c h i s t s , a l l b e l o n g i n g t o t h e g r e e n s c h i s t f a c i e s , q u a r t z - a l b i t e - e p i d o t e - a l m a n d i n e sub-f a c i e s . The most common of th e s e r o c k s a re c a l c a r e o u s b i o t i t e - m u s c o v i t e s c h i s t s . These, i n hand specimen, are dark g r a y , b l u i s h gray o r brownish g r a y , f i n e g r a i n e d , and have a s t r o n g f o l i a t i o n produced by s e g r e g a t i o n of m i n e r a l s i n t o i r r e g u l a r l a y e r s and l e n s e s . S c h i s t o s i t y and l i n e a t i o n are w e l l developed and are marked by the alinement of p l a t y and p r i s m a t i c m i n e r a l s a l o n g p l a n e s p a r a l l e l t o t h e g e n e r a l l a y e r i n g o f the r o c k . I n t h i n s e c t i o n t h e s e s c h i s t s are seen t o c o n s i s t m a i n l y o f c a l c i t e , b i o t i t e , m u s c o v i t e , q u a r t z and a l i t t l e a l b i t e . A few s m a l l s c a t t e r e d c r y s t a l s of e p i d o t e are a l s o p r e s e n t . The t e x t u r e i s l e p i d o b l a s t i c w i t h g r a n o b l a s t i c l a y e r s o f q u a r t z and f e l d s p a r . The - 14 -m i n e r a l assemblage of the s e s c h i s t s suggests t h a t they formed from c a l c a r e o u s p e l i t i c sediments. Two t y p e s o f hornblende-mica s c h i s t u n d e r l i e t h e c e n t r a l p a r t of the western h a l f o f the a r e a . The more b a s i c t y p e , composed almost e n t i r e l y of hornblende and F i g . 3 K e e f e r G u l c h , sub-area 1. Quartz b o u d i n i n h i g h l y - d e f o r m e d a r g i l l a c e o u s s c h i s t . P i c t u r e t a k e n l o o k i n g northwest. b i o t i t e ( i s g r e e n i s h i n c o l o u r and medium g r a i n e d , w i t h numerous l a r g e p o r p h y r o b l a s t s of hornblende. The s c h i s t o s i t y i n t h i s r o c k i s v e r y w e l l developed owing t o t h e abundance of mica. I n t h i n s e c t i o n the r o c k i s seen t o c o n t a i n a p p r o x i m a t e l y 60 p e r c e n t p a l e - g r e e n hornblende, - 15 -25 p e r c e n t b i o t i t e , 10 p e r c e n t q u a r t z and s m a l l e r amounts o f c h l o r i t e , c a l c i t e and s o d i c p l a g i o c l a s e . The t e x t u r e i s s t r o n g l y l e p i d o b l a s t i c w i t h l a r g e p o r p h y r o b l a s t s of hornblende. A more s i l i c e o u s t y p e c o n t a i n i n g i n p l a c e s o n l y 15 t o 20 p e r c e n t m a f i c m i n e r a l s , i s g r e e n i s h gray i n F i g . 4 K e e f e r G u l c h , sub-area 2. Hornblende p o r p h y r o b l a s t i n q u a r t z - b i o t i t e - h o r n b l e n d e s c h i s t . C r o s s e d n i c o l s (X 15) ' c o l o u r , has a p o o r e r s c h i s t o s i t y and, i n p l a c e s , somewhat resembles an impure q u a r t z i t e . I n t h i n s e c t i o n t h i s r o c k i s seen t o c o n t a i n up t o 60 p e r c e n t q u a r t z , 10 p e r c e n t a l b i t e , 15 p e r c e n t b i o t i t e and 10 t o 15 p e r c e n t g r e e n hornblende and c h l o r i t e . The t e x t u r e i s l e p i d o - g r a n o b l a s t i c - 16 -and the f o l i a t i o n i s v e r y c l e a r l y marked "by i r r e g u l a r l a y e r s o f g r a n o b l a s t i c q u a r t z which shows a s t r o n g o p t i c a l o r i e n -t a t i o n . These s c h i s t s are of the same metamorphic grade as the p e l i t i c s c h i s t s d e s c r i b e d above, but d e r i v e d from more b a s i c , p o s s i b l y v o l c a n i c r o c k s . F i g . 5 K e e f e r G u l c h , sub-area 2. C o m p o s i t i o n a l l a y e r i n g p a r a l l e l i n g s c h i s t o s i t y i n h o r n b l e n d e - b i o t i t e - q u a r t z s c h i s t . P.P.L. (X 15) A sequence o f g r e e n c h l o r i t i c p h y l l i t e s and f i n e -g r a i n e d s c h i s t s c r o p s out i n the s o u t h e a s t e r n c o r n e r of the map area and extends out of i t t o the e a s t . I n hand specimen th e s e r o c k s commonly, i f not everywhere, have a - 17 -w e l l marked s c h i s t o s i t y and l i n e a t i o n , and appear t o be composed of a f i n e - g r a i n e d , c h l o r i t i c , q u a r t z o - f e l d s p a t h i c groundmass w i t h o r i e n t e d p l a t e s o f b i o t i t e and i r r e g u l a r p o r p h y r o b l a s t s of amphibole. I n t h i n s e c t i o n the r o c k s appear t o be c h i e f l y composed o f c h l o r i t e , a l b i t e , q u a r t z , F i g . 6 K e e f e r G u l c h , sub-area 1. S c h i s t o s i t y i n c h l o r i t e - h o r n b l e n d e s c h i s t . P.P.L. (X 45) b i o t i t e and hornblende, w i t h s c a t t e r e d p atches of z o i s i t e and c a l c i t e . The t e x t u r e i s l e p i d o b l a s t i c w i t h g r a n o b l a s t i c l a y e r s of q u a r t z and f e l d s p a r . The above m i n e r a l assemblage suggests t h a t t h e s e r o c k s were formed by low-grade r e g i o n a l - 18 -* L i n e a t i o n 20 plotted F i g . 7 E q u a l - a r e a lower-hemisphere p r o j e c t i o n of p o l e s t o s c h i s t o s i t y and l i n e a t i o n s i n sub-area 1 at K e e f e r G u l c h . G r e a t c i r c l e r e p r e s e n t s average a t t i t u d e of s c h i s t o s i t y . - 19 -. F o l i a t i o n 19 p l o t t e d X L i n e a t i o n F i g . 8 -Equal-area lower-hemisphere p r o j e c t i o n of p o l e s t o s c h i s t o s i t y and of l i n e a t i o n s i n sub-area 2 at K e e f e r G u l c h . G r e a t c i r c l e s r e p r e s e n t average a t t i t u d e s o f s c h i s t o s i t y . - 20 -metamorphism of b a s i c v o l c a n i c r o c k s , p r o b a b l y a n d e s i t i c l a v a s . These p h y l l i t e s and s c h i s t s , which have been d e s c r i b e d by Jones (1959, P» 4-8) as non-metamorphosed a n d e s i t i c l a v a s , are grouped by the p r e s e n t w r i t e r w i t h t h e metamorphic r o c k s i n the w e s tern h a l f of the a r e a . T h i s c o r r e l a t i o n i s based m a i n l y on the conformable s c h i s t -o s i t y and e q u a l metamorphic grade of the r o c k s . (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s (1) S t r a t i g r a p h y - The metamorphic r o c k s d e s c r i b e d above form a conformable se-quence, i n which s t r i k e s are a p p r o x i m a t e l y e a s t e r l y and d i p s are moderate t o the south and southwest. An a n t i f o r m , a l s o t r e n d i n g e a s t e r l y , i s p r e s e n t i n the n o r t h e r n p a r t of the a r e a . The f o l l o w i n g t a b l e i s a summarized d e s c r i p t i o n of t h e v a r i o u s t y p e s of s c h i s t s i n s t r a t i g r a p h i c s u c c e s s i o n from n o r t h t o s o u t h . Approximate t h i c k n e s s i n f e e t L i t h o l o g y 7 • C h l o r i t e - b i o t i t e - h o r n b l e n d e and c h l o r i t e -b i o t i t e p h y l l i t e ; g r e e n i s h ; p r o b a b l y meta-a n d e s i t e . 7 • B i o t i t e - m u s c o v i t e c a l c a r e o u s s c h i s t ; brownish-gray. - 21 -Approximate t h i c k n e s s i n f e e t L i t h o l o g y 700 M u s c o v i t e - b l o t i t e a r g i l l a c e o u s s c h i s t ; l i m e y ; b l u i s h - g r a y t o b l a c k . 900 H o r n b l e n d e - b i o t i t e - q u a r t z s c h i s t ; g r e e n i s h . 700 Q u a r t z - b i o t i t e - h o r n b l e n d e s c h i s t ; green.. ? A r g i l l a c e o u s - m i c a c e o u s p h y l l i t e ; d a r k - g r a y . (2) P l a n a r s t r u c t u r e s - Both s c h i s t o s i t y and l a y e r i n g are w e l l d e v e l -oped i n t h e s c h i s t s o f sub-areas 1 and 2. I n o u t c r o p t h e ro c k s s p l i t e a s i l y along c l o s e l y - s p a c e d p l a n e s of s c h i s t o s i t y which are p a r a l l e l t o any c o m p o s i t i o n a l banding or l a y e r i n g t h a t i s p r e s e n t . A p l o t o f p o l e s t o s c h i s t o s i t y and l a y e r i n g i n sub-area 1 (see f i g . 7) r e v e a l s a g e n e r a l s c a t t e r i n g o f p o i n t s along a g r e a t c i r c l e which has an approximate a t t i t u d e of 060/50N.W. T h i s w r i t e r s u s p e c t s t h a t the a r e a under c o n s i d e r a t i o n has undergone at l e a s t two, or p o s s i b l y more, phases of f o l d i n g . A l l t h a t c a n be s a i d about t h e s e r o c k s i s t h a t at the p r e s e n t time the g e n e r a l a t t i t u d e o f t h e i r s c h i s t o s i t y i s 060A0S.E. and t h a t they p o s s i b l y r e p r e s e n t t h e f a u l t e d and r e - f o l d e d s o u t h e r n limb o f an a n t i f o r m t r e n d i n g a few degrees n o r t h of east (see below). - 22 -A s i m i l a r p l o t of the poles to s c h i s t o s i t y and la y e r i n g f o r sub-area 2 (see f i g . 8), also reveals a general eastwest trend, with an appreciable s c a t t e r i n g of p o i n t s . In the extreme northern p o r t i o n of the map-area the s c h i s t -o s i t y of hornblende-mica s c h i s t s dips to the north and suggests an east-trending antiformal axis near the northern border of the map. (3) Linear structures - Planes of s c h i s t o s i t y bear one prominent l i n e a t i o n marked by elongated b i o t i t e f l a k e s , hornblende c r y s t a l s , and ridges of quartz or f e l d s p a r . Axes of small f o l d s which occur on the planes of s c h i s t o s i t y are also more or l e s s p a r a l l e l to t h i s l i n e a t i o n . Most of the l i n e a t i o n s were found i n sub-area 1, and are p l o t t e d i n f i g . 7» As shown on p l a t e I, the conformity of at t i t u d e s of s c h i s t o s i t y and l i n e a t i o n i n metamorphic rocks on eit h e r side of Keefer Gulch should be noted. This f a c t does not support the existence of a north-trending f a u l t along Keefer Gulch. Linear structures i n general plunge moderately to the southeast, an average f i g u r e f o r such a t t i t u d e being 136/38°. (c) External s t r u c t u r a l r e l a t i o n s The metamorphic rocks at Keefer Gulch appear to be divided i n two blocks by at l e a s t one branching f a u l t - 23 -which t r e n d s n o r t h e a s t and passes through the c e n t r e o f the map-area. The two b l o c k s are r e f e r r e d t o as sub-areas 1 and 2. The f a u l t i s assumed on the b a s i s of sharp l i t h o l o g i c a l and s t r u c t u r a l d i s c o r d a n c e between r o c k s of sub-areas 2, $ and 5, as shown on the e n c l o s e d map. The P i g . 9 K e e f e r G u l c h . M y l o n i t e from the f a u l t s e p a r a t i n g sub-areas 1 and 3« 1/20 i n c h s c a l e f a u l t i s a l s o marked by a s t r o n g lineament which i s c l e a r l y v i s i b l e i n a e r i a l photographs of the a r e a . I n sub-area 1, t o t h e east of K e e f e r G u l c h , the c o n t a c t between green c h l o r i t i c s c h i s t s and unmetamorphosed sedimentary r o c k s i s a l s o marked by a f a u l t which was - 24 -observed at two l o c a t i o n s . I n the immediate v i c i n i t y o f t h i s f a u l t , i n t e n s e f r a c t u r i n g o c c u r s i n b o t h w a l l s . The f a u l t i s marked by an i r r e g u l a r band of r e d d i s h - w e a t h e r i n g , s t r o n g l y s l i c k e n s i d e d and f o l i a t e d q u a r t z - s e r i c i t e m y l o n i t e which v a r i e s i n t h i c k n e s s from s i x i n c h e s t o two f e e t . An a t t i t u d e of t h i s m y l o n i t e band was t a k e n at the e a s t e r n end of the f a u l t as marked on p l a t e I . Above the m y l o n i t e zone, i n the hanging w a l l o f the f a u l t , t h e r e i s a zone of i n t e n s e b r e c c i a t i o n and l e a c h i n g r a n g i n g from f i v e t o 15 f e e t i n t h i c k n e s s . Rock fragments i n t h i s zone range from l e s s t h a n one i n c h t o one o r more f e e t i n diameter and c o n s i s t o n l y o f white and g r a y l i m e s t o n e and of g r a y , s i l i c e o u s v o l c a n i c wacke. The a c t u a l f a u l t p l a n e appears t o u n d u l a t e and branch somewhat and c u t s i n t o the w h i t e hanging w a l l l i m e s t o n e , making i t d i s -c o n t i n u o u s and c a u s i n g a g r e a t d e a l of f r a c t u r i n g and r e c r y s t a l l i z a t i o n . On t h e western s i d e of K e e f e r G u l c h , t h e c o n t a c t between c a l c a r e o u s s c h i s t s of sub-area 1 and r o c k s of sub-a r e a 4 i s a l s o marked by a f a u l t , p r o b a b l y the same d e s c r i b e d above, but d i p p i n g more s t e e p l y . An exposure o f t h e f a u l t c o n t a c t was never observed, but i t appears t h a t the two sub-areas are here s e p a r a t e d by a few f e e t of r e d d i s h w e a t h e r i n g , l e a c h e d , and sheared b r e c c i a . Only one s m a l l o u t c r o p of t h i s b r e c c i a was found, and specimens c o l l e c t e d from i t and examined i n t h i n s e c t i o n appear t o - 25 -c o n s i s t of a f i n e l y g r a n u l a r mass of r e c r y s t a l l i z e d q u a r t z and s e r i c i t e , i d e n t i c a l t o t h e m y l o n i t e which was d e s c r i b e d i n the p r e c e d i n g paragraphs as marking the f a u l t on the e a s t e r n s i d e of the g u l c h . The f a u l t i s marked by a s t r a i g h t and v e r y steep g u l l y which runs down i n t o K e e f e r G u l c h and which i s w e l l i n l i n e w i t h the p r o j e c t i o n of t h e f a u l t from the e a s t . (d) T e n t a t i v e c o r r e l a t i o n A l t h o u g h the e x p e r i e n c e of t h i s w r i t e r w i t h r o c k s of the Shuswap T e r r a n e i s l i m i t e d t o l i t t l e more t h a n f o u r weeks of f i e l d work c o n c e n t r a t e d i n the t h r e e areas de-s c r i b e d i n t h i s t h e s i s , the f o l l o w i n g remarks c a n be made r e g a r d i n g t h e c o r r e l a t i o n of the metamorphic r o c k s at K e e f e r G u l c h : 1. A l l t h e r o c k s b e l o n g t o the g r e e n s c h i s t f a c i e s . 2 . D e f o r m a t i o n was s t r o n g and p r o b a b l y p o l y p h a s e . 3. The r o c k s were produced by low-grade r e g i o n a l meta-morphism of p e l i t e s and of b a s i c sedimentary and v o l c a n i c r o c k s . 4. The t y p i c a l Monashee group r o c k s as d e s c r i b e d by Jones (1959, pp. 10-1?) are of much h i g h e r metamorphic grade t h a n the s c h i s t s at K e e f e r G u l c h . Even the low-grade metamorphic r o c k s of s u b d i v i s i o n 1A-C i n G.S.C. Map 1059A (I960) do not match w e l l w i t h t h e s c h i s t s d e s c r i b e d above. - 26 -5. Because of t h e i r metamorphic grade and m i n e r a l assem-b l a g e , a c o r r e l a t i o n of t h e s e s c h i s t s w i t h r o c k s o f the E a g l e Bay f o r m a t i o n ( J o n e s , 1959, pp. 22-27) seems more a p p r o p r i a t e t h a n a c o r r e l a t i o n w i t h r o c k s o f t h e Monashee group. I l l I n t r u s i v e Rocks At l e a s t f i v e d i f f e r e n t t y p e s o f dyke r o c k s cut the low-grade metamorphic r o c k s which have been d e s c r i b e d above. U n f o r t u n a t e l y no c r o s s - c u t t i n g r e l a t i o n s have been observed among t h e s e dykes, so t h a t t h e i r r e l a t i v e ages are unknown. Absence of any of t h e s e i n t r u s i v e s i n t h e unmetamorphosed Permian r o c k s which u n d e r l i e the n o r t h -e a s t e r n p a r t o f the map-area, suggests t h a t the dykes may a l l be pre-Permian i n age. (a) P o r p h y r i t i c b i o t i t e m i c r o d i o r i t e Two l a r g e dykes o f p o r p h y r i t i c b i o t i t e m i c r o -d i o r i t e , v a r y i n g i n t h i c k n e s s from 50 t o 80 f e e t , have been mapped i n the we s t e r n p a r t o f t h e a r e a . One o f the dykes s t r i k e s r o u g h l y n o r t h e a s t and d i p s moderately t o the s o u t h e a s t , the o t h e r s t r i k e s s l i g h t l y s o u th o f e a s t and d i p s , a l s o m o d erately, t o t h e south. The cou r s e o f each dyke, and e s p e c i a l l y t h a t o f the n o r t h e a s t t r e n d i n g one, i s somewhat s i n u o u s , and i n p l a c e s the t r e n d i s almost - 27 -conformable t o the s c h i s t o s i t y o f the c o u n t r y r o c k s . A t h i r d dyke of s i m i l a r c o m p o s i t i o n and a p p r o x i mately 25 f e e t t h i c k was found c u t t i n g through the b a s i c p h y l l i t i c s c h i s t s i n the s o u t h e a s t e r n c o r n e r of the map a r e a . The t r e n d of t h i s dyke i s a l s o n o r t h e a s t e r l y and the d i p i s ste e p t o the s o u t h e a s t . P i g . 10 K e e f e r G u l c h , sub-area 1. Myrmekite s u r r o u n d i n g a l a b r a d o r i t e p henocryst i n p o r p h y r i t i c b i o t i t e m i c r o d i o r i t e . C r o s s e d n i c o l s (X 4-5) The dyke rock i s m e l a n o c r a t i c , medium g r a i n e d and p o r p h y r i t i c . I n t h i n s e c t i o n i t i s seen t o be composed c h i e f l y o f s t r o n g l y a l t e r e d p h e n o c r y s t s of a u g i t e up t o 3.5 mm. i n diameter, of f r e s h p h e n o c r y s t s o f andesine-- 28 -l a b r a d o r i t e (An 48-54) w i t h a t h i n a l b i t i c r i m , and of s u b h e d r a l t o e u h e d r a l c r y s t a l s of b i o t i t e , u s u a l l y not more t h a n 1.5 mm. i n d i a m e t e r . The groundmass, which forms a p p r o x i m a t e l y 40 p e r c e n t by volume of the r o c k , c o n s i s t o f s u b h e d r a l t o a n h e d r a l masses of p e r t h i t e , of s m a l l patches of q u a r t z and o f a n h e d r a l g r a p h i c i n t e r g r o w t h s o f q u a r t z and o r t h o c l a s e . G a l c i t e , s e r i c i t e , c h l o r i t e , magnetite and c l a y m i n e r a l s are common a l t e r a t i o n p r o d u c t s . A p a t i t e , an u n u s u a l l y abundant a c c e s s o r y m i n e r a l , o c c u r s i n s u b h e d r a l t o e u h e d r a l g r a i n s up t o 0.7 mm. i n d i a m e t e r , and i s a s s o c i a t e d w i t h pyroxene. The t e x t u r e i s hypautomorphic i n e q u i g r a n u l a r . (b) F e l d s p a r porphyry One o u t c r o p of a sheared and broken f e l d s p a r -b i o t i t e p orphyry was found a l o n g the bottom of K e e f e r G u l c h , i n the n o r t h e r n p a r t of the map-area. No o t h e r o u t c r o p of t h i s r o c k was found. Except f o r a f a i n t l y d e v e l o p e d f o l i a t i o n , more o r l e s s conformable w i t h the s c h i s t o s i t y o f the s u r r o u n d i n g metamorphic r o c k s , no o t h e r i n f o r m a t i o n as t o the c o n t a c t r e l a t i o n s of t h i s p orphyry w i t h the c o u n t r y r o c k s i s a v a i l a b l e . The r o c k i s however b e l i e v e d t o be of i n t r u s i v e o r i g i n and p r o b a b l y t o r e p r e s e n t a dyke. - 29 -( c ) Lamprophyre S e v e r a l b i o t i t e lamprophyre dykes were observed i n the-extreme southwestern c o r n e r of the map-area. The dykes range i n t h i c k n e s s from two t o 12 f e e t , s t r i k e n o r t h -east and d i p moderately t o s t e e p l y t o the northwest. No t h i n s e c t i o n of the dyke r o c k was examined. (d) Diabase Two d i a b a s e dykes were found c u t t i n g through p e l i t i c s c h i s t s i n the southwestern p a r t of the map a r e a . One dyke, a p p r o x i m a t e l y s i x f e e t t h i c k , s t r i k e s s l i g h t l y west of n o r t h and d i p s s t e e p l y t o the west. The o t h e r i s a p p r o x i m a t e l y 15 f e e t t h i c k , s t r i k e s e a s t e r l y , has a moderate s o u t h e r l y d i p and i s i n t u r n cut by a s t e e p l y d i p p i n g band of q u a r t z - f e l d s p a r pegmatite which s t r i k e s 1 1 5 °• T h i n s e c t i o n s of the d i a b a s e dykes were not made. (e) A p l i t e and q u a r t z - f e l d s p a r pegmatite S e v e r a l s m a l l b o d i e s of a p l i t i c q u a r t z p o r p h y r y and of q u a r t z - f e l d s p a r pegmatite cut through the s c h i s t s i n the western h a l f of the map-area. S t r i k e s are n o r t h -w e s t e r l y and s l i g h t l y south of e a s t . As mentioned above, one body of pegmatite was found c u t t i n g t hrough a d i a b a s e dyke. At the bottom of K e e f e r G u l c h , a s m a l l dyke of r e d d i s h - w e a t h e r i n g , p y r i t i f e r o u s q u a r t z porphyry was found - 30 -to have "been emplaced along the f o l i a t i o n of some badly broken p e l i t i c s c h i s t s . The a p l i t e and pegmatite dykes are probably among the youngest i n t r u s i v e s i n the area. At any r a t e , they are younger than the diabase dykes which they cut. IV Non-Metamorphic Rocks Non-metamorphic rocks are confined to the eastern and northeastern part of the map-area. They consist c h i e f l y of massive green volcanic conglomerate, volcanic wackes containing lenses or large pods of gray f o s s i l i f e r o u s limestone, green massive andesit i c lava and sheared and l o c a l l y strongly leached andesite b r e c c i a . ^ These rocks are believed to be part of one f a u l t block which was downdropped i n post-Permian time so that i t i s now i n contact with the h i g h l y deformed metamorphic rocks described previously. During f a u l t i n g , t h i s l a r g e r block, which i s roughly rectangular i n shape with the long side pointing to the northeast, was broken in t o three smaller blocks which were rotated with respect to one another. No ready c o r r e l a t i o n can be made between the pieces of t h i s f a u l t block; a t t i t u d e s of bedding, although more or l e s s constant w i t h i n each block, are commonly very 1 For the c l a s s i f i c a t i o n used i n naming these and other volcanic sedimentary rocks i n t h i s t h e s i s , r e f e r to Williams, Turner and G i l b e r t , "Petrography", Ch. 16, 1954-. - 31 -d i f f e r e n t between one b l o c k and another. F o r s i m p l i c i t y of d e s c r i p t i o n t h e s e t h r e e f a u l t b l o c k s w i l l be r e f e r r e d t o as sub-areas 3, 4- and 5 (see p l a t e I ) . (a) Sub-Area 3 (1) L i t h o l o g y - Sub-area 3 i s t h e l a r g e s t of the t h r e e f a u l t b l o c k s mentioned above, and o c c u p i e s the e a s t - c e n t r a l p a r t o f the map a r e a . To the south the b l o c k i s i n f a u l t c o n t a c t w i t h the g r e e n p h y l l i t e s of sub-area 1. To the n o r t h and northwest i t i s s e p a r a t e d from sub-area 5 by a n o r t h e a s t - t r e n d i n g f a u l t . To the west i t i s s e p a r a t e d from sub-area 4 by K e e f e r G u l c h . The lowermost u n i t of sub-area 3 i s a w h i t e , sugary l i m e s t o n e a p p r o x i m a t e l y 15 t o 20 f e e t t h i c k . The l i m e s t o n e i s b a d l y broken and l a r g e l y r e c r y s t a l l i z e d so t h a t no measurements of bedding a t t i t u d e c o u l d be t a k e n . Some fragments of c r i n o i d s are p r e s e n t i n the r o c k , but t h e age of the u n i t c o u l d not be determined from them. A l a y e r of l i g h t - g r a y , s t r o n g l y l e a c h e d p y r i t i f e r o u s , h a r d , v o l c a n i c conglomerate and b r e c c i a l i e s conformably above the l i m e s t o n e . The u n i t i s a p p r o x i m a t e l y 80 t o 100 f e e t t h i c k and c o n t a i n s one l e n s of g r a y , f i n e l y c r y s t a l l i n e , f r a c t u r e d l i m e s t o n e which i s l o c a l l y r i c h i n c r i n o i d a l d e b r i s . The l i m e s t o n e l e n s i s a p p r o x i m a t e l y 20 f e e t t h i c k , at l e a s t 300 t o 400 f e e t - 32 -l o n g and appears t o "be conformable w i t h the g r o s s l a y e r i n g i n the b r e c c i a , which d i p s moderately t o the northwest. A bed of gray and medium-gray a r k o s i c v o l c a n i c wacke, ap p r o x i m a t e l y 80 f e e t t h i c k , o v e r l i e s conformably the v o l c a n i c b r e c c i a and i s i n t u r n o v e r l a i n , a p p a r e n t l y P i g . 11 K e e f e r G u l c h , sub-area 3 . C r i n o i d fragment i n gray l i m e s t o n e . Needle i s >& i n c h l o n g . conformably, by two beds of sandy v o l c a n i c sediments. The lower of t h e s e i s a g r a y t o dark-gray s i l t s t o n e a p p r o x i m a t e l y 60 f e e t t h i c k w i t h a r g i l l a c e o u s bands and f i n e l y d i s s e m i n a t e d p y r i t e . The r o c k i s i n p l a c e s h i g h l y f r a c t u r e d and c o n t a i n s at l e a s t one l e n s of g r a y , t h i n l y - 35 -bedded l i m e s t o n e , l o c a l l y r i c h i n c r i n o i d p l a t e s . The o t h e r bed i s a c o a r s e r g r e e n i s h - g r a y l i t h i c v o l c a n i c wacke app r o x i m a t e l y 150 f e e t t h i c k , a l s o b r o k e n i n p l a c e s and which c o n t a i n s at l e a s t two l e n s e s of l i m e s t o n e , v e r y s i m i l a r t o those mentioned above, but p o o r e r i n c r i n o i d a l d e b r i s . F i g . 12 K e e f e r G u l c h , sub-area 3« Rock fragment c o n t a i n i n g d e v i t r i f i e d shards i n l i t h i c v o l c a n i c wacke. P.P.L. X 45. The wacke i s o v e r l a i n , a p p a r e n t l y conformably, by a green, massive, hard v o l c a n i c b r e c c i a which c o n s i s t s of fragments of micaceous p h y l l i t e , s c h i s t , q u a r t z i t e , v o l c a n i c and g r a n i t i c r o c k s s e v e r a l i n c h e s l o n g and s e t i n a g r e e n m a t r i x composed of r o c k c h i p s and o t h e r - 54 -d e t r i t u s . The r o c k i s v e r y p o o r l y s o r t e d and was formed "by r a p i d d e p o s i t i o n of r u b b l e from a v o l c a n i c t e r r a n e . Fragments of metamorphic r o c k s were p r o b a b l y brought up through a diatreme w i t h o t h e r v o l c a n i c r u b b l e . At l e a s t one l a r g e l e n s of gray, t h i n l y bedded, f i n e l y c r y s t a l l i n e , n o n - f o s s i l i f e r o u s l i m e s t o n e , 500 t o 600 f e e t l o n g and more F i g . 15 K e e f e r G u l c h , sub-area 3. V o l c a n i c conglomerate. Needle i s 1 i n c h l o n g . t h a n 100 f e e t t h i c k i s i n t e r b e d d e d w i t h t h e conglomerate. The upper l i m i t o f the b r e c c i a i s not known due t o heavy d r i f t c o ver and w i d e l y s c a t t e r e d exposures. W i d e l y spaced o u t c r o p s of a g r e e n i s h - g r a y l i t h i c v o l c a n i c wacke, o c c u r i n the n o r t h e r n h a l f of sub-area 3. Dips are not c l e a r o r v e r y marked, but seem t o be moderate t o the northwest. - 35 -S c a t t e r e d exposures of g r a y l i m e s t o n e , v e r y s i m i l a r t o t h a t forming some o f the l e n s e s d e s c r i b e d above were a l s o found i n t h i s a r e a . E l o n g a t i o n of these exposures p a r a l l e l t o t h e t r e n d i n the wacke, and a s s o c i a t i o n have l e d t o the i n t e r p r e t a t i o n of t h e l i m e s t o n e as forming l e n s e s w i t h i n the wacke. F i g . 14 K e e f e r G u l c h , sub-area 3 . V o l c a n i c conglomerate. 1/20 i n c h s c a l e . (2) I n t e r n a l s t r u c t u r a l r e l a t i o n s - The r o c k s i n sub-area 3 are b e l i e v e d t o form a conformable sequence which has an approximate minimum t h i c k n e s s of 400 t o 500 f e e t . The t a b l e below i s a summarized d e s c r i p t i o n of the r o c k t y p e s - 36 -described above as they appear i n s t r a t i g r a p h i c succession. Approximate thickness i n feet Lithology ? L i t h i c v o l c a n i c wacke; light-greenish-gray; limestone and b r e c c i a interbeds. ? Volcanic b r e c c i a ; massive, greenish; contains fragments of s c h i s t , q u a r t z i t e and volcanic rocks; large limestone lens. 150 L i t h i c volcanic wacke; greenish-gray, broken; lenses of f r a c t u r e d limestone. 60 S i l t s t o n e ; gray to dark-gray; lenses of gray limestone. 80 Arkosic volcanic wacke, gray. 100 S i l i c e o u s v o lcanic conglomerate and b r e c c i a ; l i g h t - g r a y , p y r i t i f e r o u s ; reddish-weathering; lenses of gray limestone. 20 Limestone; white, sugary; broken. Bedding dips are approximate to the north, north west and north-northeast as shown i n f i g . 15. The appre-c i a b l e s c a t t e r i n g of a t t i t u d e s noticeable i n t h i s diagram may have been produced by deformation which accompanied f a u l t i n g . The rocks, e s p e c i a l l y i n the lowermost u n i t s , are broken and f r a c t u r e d , with the cracks f i l l e d by l a t e c a l c i t e . F i g . 15 E q u a l - a r e a lower-hemisphere p r o j e c t i o n o f "bedding a t t i t u d e s i n sub-area 3 at K e e f e r G u l c h . - 3 8 -(b) Sub-Area 4 (1) Lithology - Sub-area 4 i s the smallest of the three f a u l t blocks of non-meta-morphic rocks and i s exposed only along a small steep ridge which runs up the western side of Keefer Gulch. The F i g . 16 Keefer Gulch, sub-area 4. Intergrowing a c t i n o l i t e c r y s t a l s i n micaceous a c t i n o l i t e porphyry. Crossed n i c o l s (X 15) rocks at the top of the ridge are s t r a t i g r a p h i c a l l y lowest, as dips are believed to be to the east at moderate angles. The lowermost unit i n t h i s sequence i s considered to be separated from rocks of sub-area 1 to the south by a f a u l t which i s marked by a zone of reddish-weathering - 39 -m y l o n i t i z e d b r e c c i a , v e r y s i m i l a r t o t h e one found a l o n g the f a u l t which s e p a r a t e s sub-area 1 from sub-area 3. I n hand specimen t h e rock appears t o be a g r e e n i s h , micaceous pyroxene po r p h y r y . I n t h i n s e c t i o n however, the r o c k i s seen t o have undergone a good d e a l of r e c o n s t i t u t i o n , p o s s i b l y d e u t e r i c a l t e r a t i o n , and c o n s i s t s of l a r g e pheno-c r y s t s of p a l e - g r e e n a c t i n o l i t e , p o s s i b l y pseudomorphous a f t e r pyroxene, and s e t i n a medium-grained b i o t i t e -a c t i n o l i t e groundmass. (See f i g . 16). S m a l l amounts of q u a r t z , p o o r l y twinned a l b i t e - o l i g o c l a s e ( A n 1 0 _ i 2 ) > z o i s i t e and c a l c i t e are a l s o v i s i b l e . The r o c k i s p r o b a b l y an a l t e r e d p o r p h y r i t i c a n d e s i t i c l a v a i n which t h e o r i g i n a l pyroxene has changed t o a c t i n o l i t e . An o l i v e - g r e e n , f i n e - g r a i n e d a r k o s i c wacke, not more t h a n 1G o r 12 f e e t t h i c k o v e r l i e s conformably t h e l a v a and i s i n t u r n o v e r l a i n by a massive, sugary, white l i m e s t o n e , a p p r o x i m a t e l y 25 t o 30 f e e t t h i c k . I n t h i n s e c t i o n the l i m e s t o n e i s seen t o be s t r o n g l y r e c r y s t a l l i z e d , t o c o n s i s t e x c l u s i v e l y of a n h e d r a l c a l c i t e g r a i n s 2 t o 3 mm. i n diameter and t o be c o m p l e t e l y d e v o i d of any f o s s i l remains. The s i m i l a r i t y between t h i s l i m e s t o n e and t h a t found i n sub-area 3 i s s t r i k i n g and i t may w e l l be t h a t t h e y are the same u n i t . The d i f f e r e n t appearance and c o m p o s i t i o n o f t h e two l a y e r s of v o l c a n i c b r e c c i a which, as w i l l be mentioned below, r e s p e c t i v e l y o v e r l i e t h e two - 4-0 -beds of white l i m e s t o n e on e i t h e r s i d e o f K e e f e r G u l c h , c o u l d be e x p l a i n e d by changes a l o n g the s t r i k e . The white l i m e s t o n e i s succeded conformably by a sequence of green, massive v o l c a n i c b r e c c i a and conglomerate which c o n t a i n s i r r e g u l a r l e n s e s and pods of broken and somewhat r e c r y s t a l l i z e d g ray l i m e s t o n e . The r o c k i s massive and v e r y p o o r l y bedded, but a t t i t u d e s o f l i m e s t o n e l a y e r s and of i r r e g u l a r , more a r e n i t i c l a y e r s , suggest a moderate e a s t e r l y d i p , i n ke e p i n g w i t h the rough l a y e r i n g o b s erved i n t h e u n d e r l y i n g u n i t s . Fragments of p h y l l i t e and q u a r t z i t e are common i n t h e c o n g l o m e r a t i c p o r t i o n s , but are g r e a t l y outnumbered by l a r g e fragments o f v o l c a n i c -r o c k s , o f a m p h i b o l i t e , and o f c o a r s e hornblende c o n t a i n i n g f i n e l y d i s s e m i n a t e d m a g n e t i t e . These r o c k fragments are se t i n a green, a m p h i b o l i t i c m a t r i x c o n s i s t i n g o f s m a l l e r r o c k c h i p s and of broken c r y s t a l s o f hornblende u s u a l l y 3 t o 5 mm. i n l e n g t h . I n t h i n s e c t i o n the b r e c c i a i s seen t o c o n t a i n up t o 50 o r 60 p e r c e n t h o r n b l e n d e , e i t h e r as broken c r y s t a l s i n the groundmass or as a major component of a m p h i b o l i t e fragments. Sphene i s a common a c c e s s o r y m i n e r a l and o c c u r s as l a r g e , w e l l f a c e t t e d c r y s t a l s s c a t t e r e d i n the groundmass or i n fragments o f a m p h i b o l i t e . I t i s p o s s i b l e t h a t t h e amphibole p r e s e n t i n t h i s b r e c c i a , r a t h e r t h a n b e i n g o f metamorphic o r i g i n was produced by - 41 -quenching o f a hydrous " b a s a l t i c magma i n t h e manner d e s c r i b e d by Yoder and T i l l e y (1962). These a u t h o r s o b t a i n e d a m i x t u r e of amphibole, sphene, p l a g i o c l a s e , m a g n e t i t e and g l a s s by h o l d i n g an o x i d i z e d h a w a i i t e at temperatures r a n g i n g from 750 t o 800° C f o r p e r i o d s of 66 t o 24 hours r e s p e c t i v e l y , and at a water p r e s s u r e of 5000 b a r s ( o p . c i t . , p. 444). The a u t h o r s a l s o s t a t e d t h a t "...most r u n s , when quenched above the l i q u i d u s , gave charges c o n s i s t i n g almost w h o l l y o f amphibole w i t h minor amounts o f magnetite and some g l a s s . . . " (op. c i t . , p. 445). I t i s c o n c e i v a b l e t h a t , a f t e r quenching, t h e b l o c k s of hornblende and a m p h i b o l i t e were brought t o t h e s u r f a c e by v o l c a n i s m t o be i n c l u d e d i n the b r e c c i a . (2) I n t e r n a l s t r u c t u r a l r e l a t i o n s - S t r u c t u r a l i n f o r m a t i o n i n sub-area 4 i s v e r y s c a r c e as no a c t u a l measurement of bedding can be made i n t h e massive and non-bedded r o c k s . A rough a t t i t u d e can however be deduced by o b s e r v i n g the t r a c e o f c o n t a c t between u n i t s , and by t r a c i n g l e n s e s of l i m e s t o n e i n t h e v o l c a n i c b r e c c i a d e s c r i b e d above; such o b s e r v a t i o n s suggest t h a t d i p s are t o the e a s t at moderate a n g l e s . The f o l l o w i n g t a b l e i s a summary of the r o c k t y p e s d e s c r i b e d above as t h e y appear i n s t r a t i g r a p h i c s u c c e s s i o n . - 42 -Approximate t h i c k n e s s i n f e e t L i t h o l o g y • (more t h a n 100) V o l c a n i c "breccia; g reen, massive; c o n t a i n s b o u l d e r s of h o r n b l e n d i t e , q u a r t z i t e , s c h i s t , v o l c a n i c r o c k s ; some gr a y l i m e s t o n e . 30 Limestone; w h i t e , sugary. 10 A r k o s i c v o l c a n i c wacke; o l i v e - g r e e n . 40 Micaceous a c t i n o l i t e porphyry; g r e e n i s h . ( c ) Sub-Area 5 (1) L i t h o l o g y - The lowest exposed member o f the sequence i n sub-area 5 i s a d a r k -g r a y t o y e l l o w i s h - g r a y a n d e s i t i c b r e c c i a , l o c a l l y l e a c h e d and s t r o n g l y sheared. The e x t e n t and n ature of t h i s b r e c c i a are unknown because of v e r y poor exposures. The b r e c c i a i s o v e r l a i n by a sequence of l i g h t -g r e e n , massive, medium-grained, p o r p h y r i t i c a n d e s i t i c l a v a s , 250 t o 300 f e e t t h i c k . I n t h i n s e c t i o n the r o c k has a h o l o c r y s t a l l i n e p o r p h y r i t i c t e x t u r e and c o n s i s t s of a groundmass of minute l a t h s of p l a g i o c l a s e i n which are s e t l a r g e p h e n o c r y s t s and c l u s t e r s of a l b i t i c p l a g i o c l a s e c r y s t a l s up t o 1.5 mm. i n d i a meter, and a few subrounded and s t r o n g l y c h l o r i t i z e d r o c k fragments. A l l the f e l d s p a r i s s t r o n g l y s a u s s u r i t i z e d and has been reduced t o a l b i t e - 4 3 -(An^_g). C h l o r i t e , s e r i c i t e and c a l c i t e are abundant a l t e r a t i o n p r o d u c t s and are p r e s e n t everywhere as i r r e g u l a r a n h e d r a l masses. A sequence of l i g h t - g r e e n , h a r d and f r e s h - l o o k i n g v o l c a n i c wacke, a p p r o x i m a t e l y 350 f e e t t h i c k , o v e r l i e s the F i g . 17 K e e f e r G u l c h , sub-area 5» Bent f e l d s p a r c r y s t a l i n v o l c a n i c wacke. C r o s s e d n i c o l s (X 45). l a v a s . The bedding i n t h i s u n i t i s graded and i n d i c a t e s t h a t the s t r a t a f a c e n o r t h e a s t . The beds range i n t h i c k -ness from a few i n c h e s t o a few f e e t and grade from c o a r s e c o n g l o m e r a t i c bands c o n t a i n i n g fragments of v o l c a n i c r o c k s - 44 -s e v e r a l i n c h e s l o n g , t o v e r y f i n e - g r a i n e d s i l t y hands r i c h i n a r g i l l a c e o u s m a t t e r . Towards the t o p of the u n i t , exposures become few and s c a t t e r e d , but the wacke appears t o be o v e r l a i n by a l a y e r of g r e e n i s h - g r a y v o l c a n i c b r e c c i a and conglomerate, v e r y s i m i l a r t o t h a t o f sub-area 4 and l a r g e l y composed of P i g . 18 K e e f e r G u l c h , sub-area 5» Graded bedding i n v o l c a n i c wacke. Paper c l i p i s 1 i n c h l o n g . s l i g h t l y rounded pebbles and c o b b l e s o f metamorphic, sedimentary and v o l c a n i c r o c k s . The top of t h i s u n i t i s i l l - d e f i n e d , but seems t o be marked by a s t e e p l y d i p p i n g shear zone which t r e n d s s o u t h e a s t . Above the shear zone, exposures are t o t a l l y l a c k i n g , but f u r t h e r t o the n o r t h , - 4-5 -and p r o b a b l y a c r o s s a n o r t h e a s t - t r e n d i n g f a u l t , a few s c a t t e r e d exposures of hornblende-mica s c h i s t were found a l o n g a l o g g i n g r o a d . (2) I n t e r n a l s t r u c t u r a l r e l a t i o n s - Sub-area 5 i s an e l o n g a t e d f a u l t segment w i t h the l o n g s i d e o r i e n t e d n o r t h e a s t e r l y a c r o s s the c e n t r e o f the map-area. S t r i k e s are s o u t h -e a s t e r l y and d i p s are moderate to s t e e p t o the n o r t h e a s t . Graded bedding i n t h e v o l c a n i c wacke i n d i c a t e s a normal upward sequence w i t h beds f a c i n g n o r t h e a s t . T h i s sequence i s shown i n the t a b l e below. Approximate t h i c k n e s s i n f e e t L i t h o l o g y ? V o l c a n i c b r e c c i a and conglomerate; g r e e n i s h -g r a y , c o n t a i n s p e b b l e s and c o b b l e s of q u a r t z , p h y l l i t e , l i m e s t o n e and v o l c a n i c r o c k s . 550 V o l c a n i c wacke; l i g h t - g r e e n , w e l l bedded, l o c a l l y graded bedded. 300 P o r p h y r i t i c a n d e s i t i c l a v a ; l i g h t - g r e e n , , m a s sive, c h l o r i t i z e d . ? A n d e s i t i c b r e c c i a ; d a r k - g r a y t o y e l l o w i s h -g r a y . - 46 -(d) E x t e r n a l s t r u c t u r a l r e l a t i o n s Sub-areas 3 , 4- and 5 are u n d e r l a i n by unmeta-morphosed, sedimentary and v o l c a n i c r o c k s , whereas the r e s t of the map area i s u n d e r l a i n by low-grade metamorphic r o c k s , cut by s e v e r a l t y p e s of dykes. By a s e p a r a t e examination of sub-areas 3 , 4 and 5 , i t has been attempted t o show t h a t t h e s e t h r e e sub-areas r e p r e s e n t t h r e e d i f -f e r e n t f a u l t segments, a l l p a r t of a f a u l t b l o c k which was brought i n c o n t a c t w i t h the h i g h l y deformed metamorphic r o c k s of sub-areas 1 and 2, some time a f t e r they had been i n t r u d e d by the dykes. A t t i t u d e s w i t h i n each f a u l t segment are f a i r l y c o n s t a n t , but are g r e a t l y d i f f e r e n t i n each segment. T h i s i s b e l i e v e d t o be the r e s u l t of independent r o t a t i o n a l movement of the t h r e e s l i c e s as f a u l t i n g o c c u r r e d . The k i n d o f d e f o r m a t i o n t h a t was imposed on the metamorphic r o c k s of sub-areas 1 and 2 i s a l s o d i f f e r e n t from t h a t shown by the unmetamorphosed s t r a t a of sub-areas 3 , 4 and 5» The former r o c k s have been s t r o n g l y deformed and p r o b a b l y have undergone more t h a n one phase of f o l d i n g . Metamorphic m i n e r a l assemblages, w e l l d e veloped f o l i a t i o n and l i n e a t i o n suggest t h a t f o l d i n g was accompanied by low-grade metamorphism and t h a t i t o c c u r r e d at a depth of a p p r o x i m a t e l y 4 m i l e s ( T u r n e r and Verhoogen, I960, Ch. 18). The l a t t e r group of r o c k s , on the c o n t r a r y , i s l e s s i n t e n s e l y deformed and i s v i r t u a l l y unmetamorphosed. Most - 4-7 -of the d e f o r m a t i o n i n these r o c k s o c c u r r e d at a much s h a l l o w e r depth and was of the b r i t t l e t y p e , r e s u l t i n g i n f a u l t i n g . The f a u l t s t h a t hound sub-areas 3 , 4- and 5 are shown on t h e e n c l o s e d map. The e a s t - t r e n d i n g f a u l t t h a t s e p a r a t e s sub-areas 3 and 4 from sub-area 1 was observed at two p o i n t s t o t h e east o f K e e f e r G u l c h and was found t o d i p m o d e r a t e l y t o s t e e p l y t o the n o r t h . To the west of the g u l c h , the f a u l t i s p r o b a b l y v e r y n e a r l y v e r t i c a l . V e r y l i t t l e o r no d i s p l a c e m e n t o f the f a u l t o c c u r s as i t c r o s s e s K e e f e r G u l c h , and t h i s f a c t throws some doubt on the e x i s t e n c e o f a n o r t h t r e n d i n g f a u l t a l o n g the g u l c h as d e s c r i b e d by Jones (1959, p. 4-8), but does not n e c e s s a r i l y d i s p r o v e i t . The n o r t h e a s t - t r e n d i n g b r a n c h i n g f a u l t t h a t c u t s t h r o u g h the c e n t r e o f the map a r e a and which bounds sub-ar e a 5, was never observed, but i t s e x i s t e n c e was in v o k e d t o e x p l a i n s t r u c t u r a l and l i t h o l o g i c a l d i s c r e p a n c i e s between sub-areas 2, 3 and 5» Near t h e c e n t r e o f the map a r e a , t h e branches of the f a u l t are shown t o converge and t o c o n t i n u e as one f a u l t t o the southwest, bounding sub-ar e a 4-. The o n l y evidence f o r assuming the f a u l t e x i s t s and has such a course i n t h i s p a r t o f t h e map a r e a , i s the presence on a e r i a l photographs of a s t r o n g lineament which i s on the p r o j e c t i o n o f the assumed branches of t h e f a u l t from the n o r t h e a s t . Along the n o r t h e r n boundary of - 48 -sub-area 4, r o c k exposures are c o m p l e t e l y absent, and the t h i c k c o v e r o f overburden would have t o be removed i n o r d e r t o o b t a i n any i n f o r m a t i o n about t h i s c r i t i c a l p a r t of t h e map a r e a . (e) C o r r e l a t i o n and Age The r o c k s t h a t u n d e r l i e sub-areas 3 , 4 and 5 were a s s i g n e d by Jones a " C a r b o n i f e r o u s ( ? ) and Permian" age, and p r e s e n t l y are c o n s i d e r e d t o be p a r t of the Cache Creek group. V The " K e e f e r G u l c h Unconformity" I n h i s r e p o r t on the a r e a , Jones (1959> pp. 47-48) d e s c r i b e s the Cache Creek group r o c k s as l y i n g uncon-f o r m a b l y on "micaceous p h y l l i t e s , c a l c a r e o u s q u a r t z i t e s , mica s c h i s t s and pegmatite b e l o n g i n g t o the Shuswap T e r r a n e " . I n the map accompanying h i s r e p o r t he s p e c i f i e s t h a t t h e s e metamorphic r o c k s b e l o n g t o the Monashee group. I n t h e same paragraph he s t a t e s : "...The u n c o n f o r m i t y l i e s on the west s l o p e of a s m a l l valley...known l o c a l l y K e e f e r G u l c h ...A c o n s o l i d a t e d b r e c c i a o f the u n d e r l y i n g p h y l l i t e marks the c o n t a c t and i s p a r t l y l e a c h e d and a l t e r e d t o a w h i t e , r u s t y w e a t h e r i n g , v e s i c u l a r r o c k composed of q u a r t z and s e r i c i t e . L y i n g immediately above the weathered b r e c c i a i s a massive, r a t h e r f r e s h - l o o k i n g l a v a of g r e e n , a n d e s i t i c a u g i t e porphyry c o m p r i s i n g a more o r l e s s f l a t - l y i n g f l o w about 10 f e e t t h i c k . . . " . - 49 -The p r e s e n t w r i t e r i d e n t i f i e s the " r e d d i s h b r e c c i a " w i t h the m y l o n i t e which s e p a r a t e s sub-areas 1 and 4, and the " f r e s h - l o o k i n g l a v a " w i t h the micaceous a c t i n o -l i t e porphyry of sub-area 4. The f o l l o w i n g p o i n t s are t o be noted: 1. There i s a sudden change i n metamorphic grade and s t r u c t u r e between r o c k s of sub-areas 1 and 2 and r o c k s of sub-areas 3 , 4- and 5* 2. Numerous dykes cut the metamorphic r o c k s , but are absent i n the non-metamorphic r o c k s . 3 . Rocks u n d e r l y i n g sub-area 1 and 2 are h i g h l y deformed and of low r e g i o n a l metamorphic grade b e l o n g i n g t o t h e g r e e n s c h i s t f a c i e s . Metamorphism p r o b a b l y o c c u r r e d at an approximate depth of 4 m i l e s . 4. Rocks of sub-areas 3> 4 and 5 are unmetamorphosed and l e s s i n t e n s e l y deformed t h a n t h e metamorphic r o c k s . 5» Wherever the c o n t a c t between metamorphic and non-meta-morphic r o c k s was observed, i t was found t o be marked by a zone of m y l o n i t e , d e n o t i n g a f a u l t . A b a s a l b r e c c i a , marking an u n c o n f o r m i t y was nowhere observed. P o i n t s 1 , 2 , 3 and 4 above, are compatible w i t h the e x i s t e n c e of an unconformable r e l a t i o n between meta-morphic and non-metamorphic r o c k s . The c o n t a c t d e s c r i b e d by Jones as an u n c o n f o r m i t y i s c o n s i d e r e d by t h i s w r i t e r t o be a f a u l t . Thus the u n c o n f o r m i t y , i f i t e x i s t s , i s not exposed and the q u e s t i o n must be l e f t open. - 50 -CHAPTER I I I - B.X. CREEK AREA I G e n e r a l D e s c r i p t i o n The a r e a l i e s a p p r o x i m a t e l y t h r e e m i l e s n o r t h -e a s t of Vernon, on the n o r t h s i d e of B.X. Creek. More p r e c i s e l y i t c o v e r s a p p r o x i m a t e l y 2.3 square m i l e s on and around B.X. H i l l , a low, rounded h i l l , b a r r e n i n i t s lower p a r t s but c o v e r e d by sparse c o n i f e r s at i t s t o p . The a r e a can be reached from Vernon by f o l l o w i n g the S i l v e r S t a r Mountain ro a d f o r a p p r o x i m a t e l y t h r e e m i l e s and t h e r e t u r n i n g n o r t h on a c o u n t r y r o a d . Most of the a r e a i s c o v e r e d by an e x t e n s i v e l a y e r of g l a c i a l and f l u v i a t i l e outwash and thus r o c k exposures are v e r y few and w i d e l y s c a t t e r e d . Metamorphic r o c k s of the Monashee group, c o n s i s t i n g m a i n l y of impure q u a r t z i t e and of g n e i s s cut by s m a l l b o d i e s of pegmatite crop out on e i t h e r s i d e of B.X. H i l l . They s t r i k e n o r t h e r l y w i t h g e n t l e t o steep e a s t e r l y and w e s t e r l y d i p s . A c e n t r a l s t r i p t h a t i n c l u d e s the t o p o f the h i l l i s u n d e r l a i n by sheared and broken v o l c a n i c wackes which s t r i k e e a s t e r l y and d i p moderately t o the n o r t h and t o the s o u t h . The c o n t a c t between metamorphic and non-metamorphic r o c k s i n t h i s a r e a has been d e s c r i b e d by Jones (1959, p. 4-8) as an u n c o n f o r m i t y and as f o l l o w i n g an a r c u a t e p a t h around the s l o p e s o f B.X. H i l l . The p r e s e n t w r i t e r found t h i s con-t a c t t o be n e a r e r s t r a i g h t t h a n a r c u a t e and b e l i e v e s i t t o - 51 -c o n s i s t of two a p p r o x i m a t e l y p a r a l l e l , s t e e p l y d i p p i n g and n o r t h - t r e n d i n g f a u l t s which t r u n c a t e the non-metamorphic r o c k s . I I Metamorphic r o c k s (a) L i t h o l o g y Metamorphic r o c k s i n the a r e a c o n s i s t m a i n l y of b i o t i t e - q u a r t z - f e l d s p a r g n e i s s e s , r a n g i n g i n c o l o u r from brownish gray t o l i g h t g r ay, and of medium t o d a r k - g r a y impure q u a r t z i t e . The g n e i s s e s are cut by many s m a l l , d i s c o n t i n u o u s , i r r e g u l a r b o d i e s of l i g h t - c o l o u r e d m u s c o v i t e -q u a r t z - f e l d s p a r pegmatite, which are i n g e n e r a l p a r a l l e l t o t h e l a y e r i n g of the h o s t - r o c k . L a y e r i n g i n the g n e i s s e s i s w e l l developed, w i t h a l t e r n a t i n g dark- and l i g h t - c o l o u r e d s t r a t a , r a n g i n g from a few i n c h e s t o s e v e r a l f e e t i n t h i c k -ness and almost c e r t a i n l y r e f l e c t i n g the d i f f e r e n t c o m p o s i t i o n of the o r i g i n a l sedimentary r o c k s from which the g n e i s s e s d e r i v e d . I n t h i n s e c t i o n the r o c k appears as a medium-grained, g r a n o b l a s t i c mass of q u a r t z , f e l d s p a r and b i o t i t e . The f o l i a t i o n i s w e l l marked by l e n s - l i k e concen-t r a t i o n s of q u a r t z g r a i n s , commonly s t r o n g l y o p t i c a l l y o r i e n t e d , and by a l i n e d p l a t e s of b i o t i t e . K - f e l d s p a r i s p r e s e n t i n v a r i a b l e amounts. P l a g i o c l a s e ranges i n c o m p o s i t i o n from An£Q t o A n ^ , but i n most r o c k s i t i s o l i g o c l a s e ( A ^ ^ ) . A c c e s s o r y m i n e r a l s are z i r c o n , a p a t i t e and m a g n e t i t e . - 52 -Impure q u a r t z i t e was found o n l y i n the s o u t h e r n p a r t of the a r e a , where i t i s i n t e r b e d d e d w i t h g n e i s s . The r o c k i s everywhere s t r o n g l y weathered and i n p l a c e s v e r y a r g i l l a c e o u s . A m a ssive, l i g h t - g r e e n t o g r a y - g r e e n t r e m o l i t e r o c k i s exposed o n l y on the e a s t e r n s l o p e s o f B.X. H i l l , where i t forms ste e p c l i f f s t r e n d i n g n o r t h e r l y . Metamorphic r o c k s i n the s o u t h e r n p a r t of the map a r e a are cut by v e i n s of white q u a r t z , two t o f i v e f e e t t h i c k , which s t r i k e n o r t h e a s t and d i p s t e e p l y t o the northwest. (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s S t r i k e s of f o l i a t i o n i n the metamorphic r o c k s range from n o r t h e r l y t o n o r t h w e s t e r l y w i t h g e n t l e t o moderate d i p s t o the e a s t and n o r t h e a s t . Some d i p s , however, are t o the southwest, s u g g e s t i n g a s o u t h e a s t -t r e n d i n g f o l d a x i s . I n t h e s o u t h e r n p a r t o f the a r e a , a l t h o u g h a t t i t u d e s are s c a r c e and exposures s c a t t e r e d , t h e r e i s an a l t e r n a t i o n o f g n e i s s and q u a r t z i t e t r e n d i n g more o r l e s s n o r t h e r l y . Minor f o l d axes plunge moderately t o the s o u t h -ea s t i n the n o r t h e r n and s o u t h e r n p a r t o f the a r e a . - 53 -( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s Jones (1959, p. 4-8) d e s c r i b e d an unconformity-s e p a r a t i n g metamorphic and non-metamorphic r o c k s i n the a r e a . A d e t a i l e d d i s c u s s i o n of t h i s p o i n t w i l l be g i v e n l a t e r i n t h i s c h a p t e r , where the e x t e r n a l s t r u c t u r a l r e l a t i o n s of the non-metamorphic r o c k s are d e s c r i b e d . (d) C o r r e l a t i o n Jones (1959, p. 48) d e s c r i b e s the metamorphic r o c k s i n the a r e a as "mica g n e i s s and marble of the Monashee group, c u t by pegmatite and g r a n i t e of the S i l v e r S t a r i n t r u s i o n s " . I l l Non-metamorphic Rocks (a) L i t h o l o g y The most common non-metamorphic r o c k i s a medium-gr a y , r e d d i s h - w e a t h e r i n g , medium- t o f i n e - g r a i n e d , f e l d -s p a t h i c v o l c a n i c wacke w i t h i n t e r b e d s of l i t h i c wacke, b r e c c i a and a r g i l l i t e . A medium-gray, r e d d i s h - w e a t h e r i n g , l i t h i c v o l c a n i c wacke, u s u a l l y sheared and l e a c h e d , c r o p s out on the n o r t h e r n and s o u t h e r n s l o p e s of B.X. H i l l . The rock c o n t a i n s s m a l l fragments of d a r k - g r a y t o b l a c k p h y l l i t i c r o c k s and of g r a y , l e a c h e d v o l c a n i c r o c k s s e t i n a f e l d s p a t h i c m a t r i x . E u h e d r a l cubes of p y r i t e up t o t h r e e o r f o u r mm. on the s i d e , are s c a t t e r e d throughout. I n o u t c r o p the r o c k does not show any conspicuous compo-- 54 -s i t i o n a l l a y e r i n g , but i t has w e l l d e v e l o p e d , w i d e l y spaced p l a n e s of s c h i s t o s i t y , which were a p p a r e n t l y developed by s h e a r i n g p a r a l l e l t o the bedding. The s c h i s t o s i t y s t r i k e s e a s t e r l y and d i p s t o the n o r t h and t o the south as shown on p l a t e I I , thus s u g g e s t i n g an e a s t - t r e n d i n g synform. A r e d d i s h w e a t h e r i n g , dark-gray t o b l a c k , t u f f a c e o u s a r g i l -P i g . 19 B.X. Creek. Sheared f e l d s p a t h i c v o l c a n i c wacke. P . P . L . (X 15) l i t e c r ops out w i t h i n f e l d s p a t h i c wacke at the top of B.X. H i l l . The r o c k i s massive and forms o n l y a few s m a l l exposures. Some l i g h t - t o dark - g r e e n , massive, s t r o n g l y l e a c h e d v o l c a n i c pebble and b o u l d e r conglomerate, v e r y s i m i l a r t o the v o l c a n i c conglomerates and b r e c c i a s o f - 55 -K e e f e r G u l c h i s a l s o found on the s o u t h e r n s l o p e s of B.X. H i l l . (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s The r o c k s d e s c r i b e d above s t r i k e e a s t e r l y w i t h moderate d i p s t o t h e n o r t h and south, and a p p a r e n t l y form F i g . 20 B.X. Creek. Sheared f e l d s p a t h i c v o l c a n i c wacke. P.P.L. (X 15) a broad e a s t - t r e n d i n g synform. I n the s o u t h e r n p a r t of the a r e a , a t t i t u d e s are v e r y i n c o n s i s t e n t because of f r a c t u r i n g and f a u l t i n g r e l a t e d t o the n o r t h - t r e n d i n g f a u l t which s e p a r a t e s t h e s e r o c k s from g n e i s s of the Monashee group t o the west. - 56 -( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s As shown on p l a t e I I , non-metamorphic r o c k s s t r i k e e a s t e r l y and u n d e r l i e o n l y t h e c e n t r a l p a r t of the a r e a . These r o c k s are t r u n c a t e d t o the e a s t and t o the west by g n e i s s o f the Monashee group which s t r i k e n o r t h e r l y and n o r t h w e s t e r l y . The c o n t a c t s between t h e s e two u n i t s f o l l o w n e a r l y s t r a i g h t l i n e s and are b e l i e v e d t o be f a u l t s which s t r i k e n o r t h e r l y and d i p s t e e p l y . (d) C o r r e l a t i o n and Age The non-metamorphic r o c k s d e s c r i b e d above are v e r y s i m i l a r i n l i t h o l o g y t o the non-metamorphic r o c k s a t K e e f e r G u l c h which are c o n s i d e r e d t o be of Cache Creek age. IV I n t r u s i v e r o c k s I n t h e s o u t h e r n p a r t o f the a r e a , non-metamorphic r o c k s are c u t by a body of a l a s k i t e p o r p h y r y . I t appar-e n t l y s t r i k e s e a s t e r l y and p r o b a b l y i s a dyke. The r o c k i s r e d d i s h w e a t h e r i n g , l i g h t g r a y t o almost w h i t e , f i n e g r a i n e d , p o r p h y r i t i c , and sheared. A f o l i a t i o n , produced by s h e a r i n g , s t r i k e s e a s t e r l y and d i p s s t e e p l y t o the n o r t h . - 57 -I n t h i n s e c t i o n the r o c k has a s t r o n g l y p o r p h y r i t i c t e x t u r e . Large, e u h e d r a l c r y s t a l s o f s t r o n g l y s e r i c i t i z e d o r t h o c l a s e and of a l b i t i z e d p l a g i o c l a s e ( A n 0 - A n t 3 ) , p r e s e n t i n r o u g h l y equal amounts, and a n h e d r a l q u a r t z g r a i n s w i t h s t r o n g l y r e s o r b e d b o r d e r s are s e t i n a v e r y f i n e - g r a i n e d groundmass of q u a r t z and s e r i c i t e . P i g . 21. B.X. Creek. Quartz phenocryst w i t h r e s o r b e d b o r d e r s i n s e r i c i t i z e d a l a s k i t e p orphyry. C r o s s e d n i c o l s (X 15) V The "B.X. Creek Unconformity" Jones d e s c r i b e d the a r e a as b e i n g the s i t e of the B.X. Creek u n c o n f o r m i t y , t h e o u t c r o p o f which " . . . t r e n d s i n an a r c u a t e p a t h around the s l o p e s of a c o n i c a l bare h i l l (B.X. H i l l ) and l i e s i n a p o s i t i o n - 58 -midway between th e base and the c r e s t at a more or l e s s c o n s t a n t e l e v a t i o n . . . " ( 1 9 5 9 , p. 4 8 ) . A d e t a i l e d e x a m i n a t i o n by the p r e s e n t w r i t e r r e v e a l e d a sharp change i n l i t h o l o g y , s t r u c t u r a l t r e n d s , and grade of metamorphism between metamorphic and non-meta-morphic r o c k s i n the a r e a . Exposures of the l i t h i f i e d r e g o l i t h which, a c c o r d i n g t o Jones, marks the u n c o n f o r m i t y were not found, and the c o n t a c t s between metamorphic and non-metamorphic r o c k s are b e l i e v e d t o be f a u l t s . T h i s p i c t u r e , s i m i l a r t o t h a t produced f o r K e e f e r G u l c h , i s compatible w i t h the e x i s t e n c e o f an u n c o n f o r m i t y which, i f i t e x i s t s , i s not exposed. Thus the q u e s t i o n must be l e f t open. - 59 -CHAPTER IV - SALMON RIVER AREA I G e n e r a l D e s c r i p t i o n The a r e a mapped, a p p r o x i m a t e l y 2000 f e e t wide and 7000 f e e t l o n g , l i e s a l o n g Salmon R i v e r V a l l e y . I t may he reached by f o l l o w i n g the Douglas Lake r o a d f o r a p p r o x i m a t e l y 12.2 m i l e s westward from Westwold. Exposures are moderately common alo n g the v a l l e y bottom and on t h e lower s l o p e s , but at h i g h e r l e v e l s bed-r o c k i s c o m p l e t e l y covered by a t h i c k b l a n k e t o f g l a c i a l and f l u v i o - g l a c i a l d e b r i s . The e a s t e r n s l o p e of the v a l l e y i s u n d e r l a i n m o s t l y by h i g h l y deformed metamorphic r o c k s o f the Chapperon group, which s t r i k e s l i g h t l y e a s t o f n o r t h and d i p s t e e p l y t o t h e northwest and s o u t h e a s t . The w e s t e r n s l o p e i s c h i e f l y u n d e r l a i n by f r e s h , undeformed sedimentary r o c k s b e l o n g i n g t o e i t h e r the Cache Creek o r N i c o l a group. These s t r i k e n o r t h e a s t e r l y w i t h g e n t l e n o r t h w e s t e r l y d i p s and are b e l i e v e d t o o v e r l i e unconformably the metamorphic r o c k s . I I Metamorphic Rocks (a) L i t h o l o g y ( 1 ) Chapperon group - Rocks o f the Chapperon group are h i g h l y deformed, v e r y f i n e -g r a i n e d , brownish-green t o almost b l a c k , micaceous p h y l l i t i c s c h i s t s which s t r i k e e a s t - n o r t h e a s t and d i p s t e e p l y . Even - 60 -i n the hand specimen l a y e r i n g i s v e r y d i s c o n t i n u o u s , and s m a l l l e n s e s and knots of v e r y f i n e - g r a i n e d q u a r t z are much more common t h a n c o n t i n u o u s l a y e r s . I n t h i n s e c t i o n the r o c k s are seen t o c o n t a i n 5 0 t o 60 p e r c e n t q u a r t z , and 30 t o 4-0 p e r c e n t b i o t i t e , commonly accompanied by s m a l l e r amounts of a l b i t e and e p i d o t e . F i g . 22 Salmon R i v e r Unconformity. Blue p e n c i l p a r a l l e l s d i p d i r e c t i o n o f s c h i s t o s i t y i n Chapperon r o c k s ; r e d p e n c i l p a r a l l e l s d i p d i r e c t i o n o f e r o s i o n s u r f a c e . C h l o r i t e , c a l c i t e , sphene and magnetite are common a c c e s s o r y m i n e r a l s . The t e x t u r e i s u s u a l l y f i n e l y l e p i d o b l a s t i c t o g r a n o b l a s t i c w i t h i r r e g u l a r l e n s e s o f q u a r t z . The q u a r t z g r a i n s do not show obvious p r e f e r r e d o p t i c a l o r i e n t a t i o n . - 61 -The s c h i s t o s i t y i s v e r y w e l l marked by o r i e n t e d p l a t e s of mica and by the e l o n g a t i o n of l e n s e s o f q u a r t z , and i s commonly c r o s s e d , at a n g l e s r a n g i n g from 60° t o 9 0 ° , by c l o s e l y spaced, p o s t - c r y s t a l l i n e s - s u r f a c e s of s t r a i n - s l i p c l e a v a g e ( W i l l i a m s , T u r n e r and G i l b e r t , 1953, p. 213). F i g . 23 Salmon R i v e r . H i g h l y deformed s i l i c e o u s a r g i l l a c e o u s s c h i s t . Paper c l i p i s 1 i n c h l o n g . A l t h o u g h the s c h i s t s are commonly h i g h l y deformed, no c l e a r evidence of r e t r o g r a d e metamorphism was found. The m i n e r a l assemblages mentioned above, and the t e x t u r e suggest t h a t these r o c k s are low-grade p e l i t i c s c h i s t s which p r o b a b l y b e l o n g t o the q u a r t z - a l b i t e - e p i d o t e -- 62 --almandine subfacies of the greenschist f a c i e s (Turner and Verhoogen, I960, p. 540). Interbedded with the s c h i s t s are layers of highly contorted "ribbon chert", ranging i n thickness from a few feet to several hundreds of f e e t . Such layers are p a r a l l e l to the general s c h i s t o s i t y and are believed to represent F i g . 24 Salmon River. Quartz lenses i n s i l i c e o u s s c h i s t . Grossed n i c o l s (X 15). o r i g i n a l beds of chert within the shales from which the s c h i s t s were formed. A few quartz veins, 5 to 10 feet wide and trending northerly with steep e a s t e r l y dips, cut the s c h i s t s . - 63 -(2) O l d Dave I n t r u s i v e s - S e v e r a l s e r p e n t i n i z e d dykes b e l o n g i n g t o the O l d Dave I n t r u s i v e s ( J o n e s , 1959? p. 34) cut the r o c k s o f the Chapperon group. The dykes s t r i k e n o r t h w e s t e r l y and d i p e i t h e r v e r y s t e e p l y o r v e r t i c a l l y . The two l a r g e s t dykes are more th a n 300 f e e t t h i c k and crop out near the F i g . 25 Salmon R i v e r . S t r a i n - s l i p c l e a v a g e i n m i c a c e o u s - a r g i l l a c e o u s s c h i s t . P.P.L. (X 15). middle of the map-area. They are p a r a l l e l e d t o the n o r t h by t h r e e s m a l l e r b o d i e s of s e r p e n t i n e . The r o c k ranges i n c o l o u r from apple g r e e n t o r e d d i s h brown and almost b l a c k , and i s a s t r o n g l y b r e c c i a t e d s e r p e n t i n e w i t h i r r e g u l a r v e i n l e t s and pods of t a l c y o r c a l c a r e o u s m a t e r i a l . - 64- -I n t h i n s e c t i o n the r o c k appears as a f e l t e d mass of s e r p e n t i n e and t a l c , w i t h i r r e g u l a r p a t c h e s o f carbonate and d i s s e m i n a t e d minute e u h e d r a l t o s u b h e d r a l c r y s t a l s o f m a g n e t i t e . (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s The metamorphic r o c k s d e s c r i b e d above s t r i k e n o r t h e a s t e r l y and d i p s t e e p l y t o the northwest. F i g u r e 25 i s a lower-hemisphere e q u a l - a r e a p r o j e c t i o n o f p o l e s t o t h e s c h i s t o s i t y i n t h e s e r o c k s . From t h i s diagram i t i s e v i d e n t t h a t : 1. The r o c k s form e i t h e r a warped h o m o c l i n a l sequence w i t h an average a t t i t u d e o f 060/96°N.W., o r a sequence of i s o c l i n a l f o l d s , the a x i a l p l a n e s o f which have the above a t t i t u d e . 2 . The a t t i t u d e s o f few minor f o l d axes t h a t c o u l d be o b t a i n e d , produce a wide s c a t t e r o f p o i n t s , most of which l i e near the g r e a t c i r c l e w i t h a t t i t u d e 060/96° N.W. ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s The metamorphic r o c k s d e s c r i b e d are b e l i e v e d t o u n d e r l i e unconformably t h e sedimentary r o c k s which occupy th e w e s t e r n h a l f o f the a r e a . A more d e t a i l e d d e s c r i p t i o n o f the u n c o n f o r m i t y w i l l be g i v e n l a t e r . - 65 -5.0 plotted 3 0 J ] 15-30 10-15 X L i n e a t i o n II plotted 5-10 5 percent per I percent area P i g . 26 E q u a l - a r e a lower-hemisphere p r o j e c t i o n of p o l e s t o s c h i s t o s i t y and of minor f o l d axes i n Chapperon group r o c k s at Salmon R i v e r . Great c i r c l e r e p r e s e n t s average a t t i t u d e of s c h i s t o s i t y . - 66 -(d) C o r r e l a t i o n and Age The s c h i s t s d e s c r i b e d above are low-grade meta-morphic r o c k s o f p e l i t i c o r i g i n . I n metamorphic grade and l i t h o l o g y t h e y are s i m i l a r t o some of t h e metamorphic r o c k s at K e e f e r G u l c h . Jones (1959) has mapped t h e s e r o c k s as p a r t of t h e Chapperon group, which he c o n s i d e r e d pre-Cambrian i n age and v e r y s i m i l a r i n l i t h o l o g y and metamorphic grade t o the E a g l e Bay f o r m a t i o n , a p o r t i o n of the Mt. Ida group. The O l d Dave I n t r u s i v e s which c u t the Chapperon group r o c k s were not found anywhere c u t t i n g the younger sedimentary r o c k s , and are t h e r e f o r e c o n s i d e r e d to be p r e -u n c o n f o r m i t y i n age. T h e i r h i g h l y b r o k e n p r e s e n t appearance suggests t h a t they were p r o b a b l y a f f e c t e d by some of the l a t e r phases of d e f o r m a t i o n which a f f e c t e d the Chapperon r o c k s . I l l Non-metamorphic r o c k s (a) L i t h o l o g y The lowest u n i t of the non-metamorphic r o c k s i s a b a s a l conglomerate which v a r i e s from 25 t o 50 f e e t i n t h i c k n e s s , i s p o o r l y bedded and c o n t a i n s sub-angular t o p o o r l y rounded p e b b l e s , c o b b l e s and b o u l d e r s of l i g h t - g r a y q u a r t z i t e , g r e e n s t o n e , - c h e r t , l i g h t - g r a y l i m e s t o n e , q u a r t z and p h y l l i t e , s e t i n a brownish-green, c a l c a r e o u s , s l i g h t l y r e c r y s t a l l i z e d b i o t i t i c m a t r i x . The r o c k a l s o c o n t a i n s - 67 -i r r e g u l a r f i n e - and c o a r s e - g r a i n e d l e n s e s and l a y e r s o f c a l c a r e n i t e , which, t o g e t h e r w i t h a rough l a y e r i n g and alinement of the p e b b l e s , mark a crude bedding. I n o u t c r o p the h a r d , s i l i c e o u s fragments weather d i f f e r e n t i a l l y from t h e m a t r i x and s t a n d out, thus p r o d u c i n g a v e r y rough, i r r e g u l a r s u r f a c e . The rough l a y e r i n g i n the r o c k i s F i g . 27 Salmon R i v e r . C r i n o i d p l a t e s i n c a l c a r e n i t e . P.P.L. (X 4 5 ) . conformable w i t h t h a t of more c l e a r l y bedded u n i t s h i g h e r i n the sequence. I n two p l a c e s exposures were found i n which bo t h s c h i s t and o v e r l y i n g conglomerate are v i s i b l e . The c o n t a c t between the two u n i t s i s sharp, unconformable and g e n t l y u n d u l a t i n g . - 68 -Conformably o v e r l y i n g the conglomerate i s a l a y e r of medium- t o d a r k - g r a y , c o a r s e c a l c a r e n i t e , a p p r o x i m a t e l y 10 f e e t t h i c k . I n t h i n s e c t i o n t h e r o c k i s seen t o c o n s i s t c h i e f l y o f subrounded fragments of l i m e s t o n e , and t o c o n t a i n abundant c r i n o i d a l and o t h e r o r g a n i c d e b r i s (see f i g . 27) . Subrounded p e b b l e s of c h e r t and q u a r t z i t e are a l s o p r e s e n t i n moderate amounts. The c o a r s e c a l c a r e n i t e grades upwards i n t o a f i n e r - g r a i n e d , d a r k e r - g r a y t o almost b l a c k , t u f f a c e o u s and commonly a r g i l l a c e o u s c a l c a r e n i t e , a p p r o x i m a t e l y 25 t o 30 f e e t t h i c k . The r o c k c o n t a i n s few c h e r t y and some f o s s i l fragments. A 2.5 t o 3-foot l a y e r o f l i g h t - g r e e n t o g r e e n i s h -g r a y , t h i n l y bedded, s i l i c i f i e d v i t r i c c r y s t a l t u f f o v e r l i e s the c a l c a r e n i t e . T h i s u n i t , a l t h o u g h t h i n , was found t o be v e r y c o n t i n u o u s and prove d t o be an e x c e l l e n t marker bed. I n t h i n s e c t i o n (see f i g . 28) the r o c k appears t o c o n s i s t m a i n l y o f a v e r y f i n e - g r a i n e d , s i l i c e o u s m a t r i x , r i c h i n s e r i c i t e , c h l o r i t e and c a r b o n a t e , and p r o b a b l y r e p r e s e n t i n g a l t e r e d g l a s s . S m a l l amounts of a l b i t i z e d f e l d s p a r , q u a r t z , mica, c h l o r i t i z e d hornblende and some a l t e r e d fragments of c h e r t a re s e t i n the m a t r i x . The d e l i c a t e b edding, the t e x t u r e , and t h e e x t e n s i v e a l t e r a t i o n suggest t h a t the r o c k i s a w a t e r - l a i n t u f f . Above the g r e e n t u f f i s a band of massive, brownish-gray t o almost b l a c k f e l d s p a t h i c graywacke a p p r o x i -m a tely 10 f e e t t h i c k . I n t h i n s e c t i o n the r o c k i s seen t o - 69 -be v e r y p o o r l y s o r t e d and t o c o n s i s t m a i n l y of subangular g r a i n s of s e r i c i t i z e d f e l d s p a r and q u a r t z , 1.5 t o 2 mm. i n diameter and s e t i n a m a t r i x of b i o t i t e , c a l c i t e and a r g i l l a c e o u s m a t e r i a l . C h l o r i t e , a p a t i t e and p y r i t e are common a c c e s s o r y m i n e r a l s . Very few h i g h l y a l t e r e d f r a g -ments of a r g i l l a c e o u s r o c k s are a l s o p r e s e n t . A bed o f F i g . 28 Salmon R i v e r . V i t r i c c r y s t a l t u f f . P.P.L. (X 15). medium-grained, massive, green, a n d e s i t i c r o c k , a p p r o x i -mately 25 t o 30 f e e t t h i c k o v e r l i e s the graywacke. I n hand specimen the r o c k has the appearance of a b a s i c i n t r u s i v e r o c k , but i n t h i n s e c t i o n i t i s seen t o c o n s i s t c h i e f l y of s u b h e d r a l , ragged c r y s t a l s of a c t i n o l i t e set i n a f e l t e d - 70 -groundmass of c l i n o z o i s i t e , c h l o r i t e and c a l c i t e p r a c t i c a l l y -d e v o i d of q u a r t z and f e l d s p a r . The a c t i n o l i t e c r y s t a l s commonly c o n t a i n patches of c a l c i t e and c l i n o z o i s i t e . I n t h r e e exposures, more t h a n 2500 f e e t a p a r t , t h i s u n i t was found i n c o n t a c t w i t h the graywacke or w i t h o v e r l y i n g a r g i l l i t e . The c o n t a c t s do not show any evidence of c h i l l i n g o r any o t h e r f e a t u r e t h a t might suggest the r o c k t o he a b a s i c s i l l . The c o n s t a n t s t r a t i g r a p h i c p o s i t i o n and t h i c k n e s s , t o g e t h e r w i t h m i n e r a l c o m p o s i t i o n and t e x t u r e suggest t h a t the r o c k i s an a l t e r e d , a n d e s i t i c c r y s t a l t u f f o r p o s s i b l y a l a v a f l o w . Conformably o v e r l y i n g t h i s u n i t i s a b l a c k , t h i n l y bedded c a l c a r e o u s a r g i l l i t e w i t h some t h i n , t u f f a c e o u s bands. The r o c k i s h a r d and has a marked s u b c o n c o i d a l f r a c t u r e , but where weathered i t i s v e r y f i s s i l e and f r i a b l e . The t h i c k n e s s of t h e u n i t , a l t h o u g h i t c o u l d nowhere be measured i n a co n t i n u o u s exposure, i s p r o b a b l y i n t h e o r d e r of 60 t o 70 f e e t . A second bed of a l t e r e d , a n d e s i t i c c r y s t a l t u f f , o r a n d e s i t i c l a v a , a p p r o x i m a t e l y 20 f e e t t h i c k , o v e r l i e s the a r g i l l i t e . I n the hand specimen t h e r o c k i s massive, f i n e g r a i n e d p o r p h y r i t i c and brownish g r e e n i n c o l o u r . I n t h i n s e c t i o n i t c o n s i s t o f s u b h e d r a l , b r o k e n c r y s t a l s o f p a l e - g r e e n hornblende, of s e r i c i t i z e d and b r o a d l y twinned f e l d s p a r , and of q u a r t z showing embayed c r y s t a l f a c e s , s e t i n a m a t r i x r i c h i n b i o t i t e , h ornblende, c a l c i t e , c h l o r i t e , > 50 3 0 - 5 0 15-30 5-15 <• 5 percent per I percent area . F i g . 29 E q u a l - a r e a lower-hemisphere p r o j e c t i o n of p o l e s t o bedding i n non-metamorphic r o c k s at Salmon R i v e r . Great c i r c l e r e p r e s e n t s average a t t i t u d e o f bedding. - 72 -f i n e - g r a i n e d q u a r t z and a r g i l l a c e o u s m a t e r i a l . A few a l t e r e d fragments o f b a s i c r o c k s are s t i l l d i s c e r n i b l e as c l u s t e r s of f e l d s p a r s , e p i d o t e , c a l c i t e and b i o t i t e . A p p a r e n t l y conformably o v e r l y i n g t h i s u n i t i s a brownish-g r a y , massive, f e l d s p a t h i c graywacke v e r y s i m i l a r t o t h a t d e s c r i b e d above. The t h i c k n e s s o f t h i s u n i t i s unknown as o n l y s m a l l s c a t t e r e d exposures were found surrounded by a t h i c k cover o f d r i f t . (b) I n t e r n a l s t r u c t u r a l r e l a t i o n s The r o c k s d e s c r i b e d i n the p r e c e d i n g paragraphs s t r i k e n o r t h e r l y t o n o r t h e a s t e r l y and d i p moderately t o g e n t l y t o the west and northwest. F i g u r e 29 i s a lower-hemisphere e q u a l - a r e a p r o j e c t i o n o f p o l e s t o bedding, and shows a f a i r c o n c e n t r a t i o n o f p o i n t s , t h e c e n t r e o f which g i v e s an average a t t i t u d e o f 031/30°N.W. The f o l l o w i n g t a b l e i s a summarized d e s c r i p t i o n of the ro c k s d e s c r i b e d i n the p r e c e d i n g pages, as the y occur i n s t r a t i g r a p h i c s u c c e s s i o n . Approximate t h i c k n e s s i n f e e t L i t h o l o g y • F e l d s p a t h i c graywacke; brownish-gray; t u f f a c e o u s ; massive. 20 A l t e r e d b a s i c c r y s t a l t u f f o r l a v a ; d a r k -brownish-green; v e s i c u l a r ; f i n e - g r a i n e d ; p o r p h y r i t i c . - 73 -Approximate t h i c k n e s s i n f e e t L i t h o l o g y 70 B l a c k a r g i l l i t e , c a l c a r e o u s ; thin-bedded; t u f f a c e o u s bands. 30 A l t e r e d b a s i c c r y s t a l t u f f or l a v a ; medium-t o l i g h t - g r e e n ; medium-grained, p o r p h y r i t i c , m assive. 10 F e l d s p a t h i c graywacke; brownish-gray. M a s s i v e . 3 V i t r i c c r y s t a l t u f f ; l i g h t - g r e e n ; t h i n -bedded, s i l i c i f i e d . 30 O a l c a r e n i t e , f i n e g r a i n e d , t u f f a c e o u s ; d a r k - g r a y , l o c a l l y a r g i l l a c e o u s . 10 O a l c a r e n i t e , c o a r s e ; medium- t o dark-gray; c o n t a i n s c r i n o i d a l d e b r i s , c h e r t and q u a r t z i t e fragments. 25-50 B a s a l conglomerate; g r e e n i s h - t o brownish-gray; c a l c a r e o u s ; c o n t a i n s c o b b l e s o f c h e r t , q u a r t z i t e , l i m e s t o n e and p h y l l i t e . ( c ) E x t e r n a l s t r u c t u r a l r e l a t i o n s The sedimentary and v o l c a n i c r o c k s d e s c r i b e d above are s e p a r a t e d from the u n d e r l y i n g metamorphic r o c k s of t h e Chapperon group by an u n c o n f o r m i t y which i s marked by a b a s a l conglomerate of v a r i a b l e t h i c k n e s s . The uncon-formable c o n t a c t was observed at s i x d i f f e r e n t and w i d e l y s e p a r a t e d exposures (see F r o n t i s p i e c e and F i g . 2 6 ). I n - 74 -every i n s t a n c e the c o n t a c t was found t o be sharp, u n d u l a t i n g , and marking a d i s c o r d a n c e o f a t t i t u d e of as much as 90 degrees. I n two exposures the s c h i s t o s i t y of the metamorphic r o c k s was found to c o n t i n u e i n t o the o v e r l y i n g conglomerate as a s e t of c l o s e l y spaced shear p l a n e s o r i e n t e d at a l a r g e angle t o the bedding. T h i s f e a t u r e i s b e l i e v e d t o have been produced by l a t e d e f o r m a t i o n which caused f u r t h e r movement al o n g the s c h i s t o s i t y i n the metamorphic r o c k s , and which c o n t i n u e d upwards p r o d u c i n g shear i n the younger sediments. A d d i t i o n a l evidence f o r the u n c o n f o r m i t y i s : 1. Rock fragments i n the b a s a l conglomerate are e x c l u s i v e l y of metamorphic r o c k s i n p a r t s i m i l a r t o those u n d e r l y i n g the e a s t e r n h a l f of the a r e a . 2. Dykes of the O l d Dave I n t r u s i o n s a r e a p p a r e n t l y t r u n c a t e d a t the c o n t a c t w i t h the non-metamorphic r o c k s . 3. There i s a sharp d i f f e r e n c e i n metamorphic grade between Chapperon group and younger r o c k s . (d) T e n t a t i v e C o r r e l a t i o n and Age Jones (1959, p. 29) c o r r e l a t e d the r o c k s o v e r l y i n g the Salmon R i v e r u n c o n f o r m i t y w i t h the Cache Creek group "...because o f t h e i r s t r i k i n g s i m i l a r i t y i n l i t h o l o g y and because, where th e y extend i n t o the a d j a c e n t N i c o l a map-a r e a , t h e y have been mapped as Cache Creek by C o c k f i e l d - 75 -(1948) f o r l i t h o l o g i c a l and s t r a t i g r a p h i c reasons". C o c k f i e l d , when describing the contact r e l a t i o n s between Cache Creek and Nicola rocks (1948, p. 8) r e f e r s to a supposed unconformity previously mapped by Daly (1915, pp. 122-123) i n the v i c i n i t y of Campbell Creek, on the north shore of the South Thompson River. At t h i s l o c a l i t y , the basal bed of the Nicola rocks i s a conglomerate, 150 feet t h i c k and containing rounded and angular fragments of rocks resembling those of the Cache Creek group. In h i s l a t e r examination of the Cache Creek-Nicola r e l a t i o n s , C o c k f i e l d states that since " . . . t h i s conglomerate...was discovered at several places i n close a s s o c i a t i o n with rocks that are l i t h o l o g i c a l l y i d e n t i c a l with other members of the Cache Creek group..." i t s i d e n t i f i c a t i o n as a basal con-glomerate has become extremely doubtful. Regarding the Nicola-Cache Creek contact, he continues "...the contact was, therefore, drawn where the rocks became preponderantly of volcanic o r i g i n , that i s , at the base of the massive Nicola greenstone...". In the same paragraph, C o c k f i e l d also states that the contact seemed to separate p e r f e c t l y conformable rocks, although greater changes i n l i t h o l o g y characterized the Cache Creek type rocks, as compared to the Nicola rocks. D.N. Hillhouse (Address to the Vancouver Geologi-c a l Discussion Club, Feb. 4, 1964) while mapping i n the Douglas Lake Plateau, just west of the area that i s now 1 - 76 -b e i n g d e s c r i b e d , found no evidence of u n c o n f o r m i t y between N i c o l a and Cache Creek r o c k s . Prom the above summary of the l i t e r a t u r e , the f o l l o w i n g p o i n t s emerge: 1. Jones c o r r e l a t e d the non-metamorphic r o c k s i n t h e a r e a w i t h the Cache Creek group because of s i m i l a r i t y w i t h o t h e r Cache Creek r o c k s and because t h e y are e x t e n s i o n s of areas u n d e r l a i n by r o c k s mapped by C o c k f i e l d as Cache Creek. 2. C o c k f i e l d a r b i t r a r i l y p l a c e d the Cache C r e e k - N i c o l a boundary at the bottom of the massive N i c o l a g r e e n s t o n e , but d i d not admit the presence of t h e u n c o n f o r m i t y suggested by D a l y . 3. N e i t h e r C o c k f i e l d (1948) nor Jones (1959) had any d e f i n i t e p a l e o n t o l o g i c a l or s t r u c t u r a l evidence on which t o base the s e p a r a t i o n of Cache Creek r o c k s from N i c o l a r o c k s i n the Douglas Lake P l a t e a u , o r by which t o c o r r e l a t e the r o c k s o v e r l y i n g t h e Salmon R i v e r u n c o n f o r m i t y w i t h the Cache Creek group. 4. More r e c e n t i n v e s t i g a t o r s a p p a r e n t l y f i n d no d e f i n i t e change from Cache Creek r o c k s i n t o N i c o l a r o c k s i n the Douglas Lake r e g i o n . T h i s w r i t e r d i d not f i n d any f o s s i l s t h a t c o u l d be used i n d a t i n g the r o c k s which o v e r l i e the u n c o n f o r m i t y at Salmon R i v e r , and p r o v i s i o n a l l y c o n s i d e r s them to be " C a r b o n i f e r o u s o r l a t e r " i n age, and p o s s i b l y as young as Upper T r i a s s i c . - 77 -IV Young I n t r u s i v e Rocks (a) L i t h o l o g y (1) Hornblende m i c r o d i o r i t e - Dykes of hornblende m i c r o d i o r i t e range i n t h i c k n e s s from 3 t o 15 f e e t and s t r i k e n o r t h e r l y and e a s t e r l y w i t h v e r t i c a l o r v e r y s t e e p d i p s . F i g . 30 Salmon R i v e r . Twinned hornblende phenocryst r e p l a c e d by c a l c i t e and e p i d o t e i n hornblende m i c r o d i o r i t e . C r o s s e d n i c o l s (X 4-5). In the hand specimen the r o c k c o n s i s t s of p a r t l y c h l o r i t i z e d s u b h e d r a l t o e u h e d r a l p h e n o c r y s t s of hornblende as much as 2 cm. l o n g , s e t i n a l i g h t - g r e e n , a p h a n i t i c t o f i n e l y c r y s t a l l i n e groundmass. - 78 -I n t h i n s e c t i o n the t e x t u r e i s n o n c r y s t a l l i n e , hypautomorphic p o r p h y r i t i c . The p h e n o c r y s t s form 15 p e r c e n t of t h e r o c k and are sub h e d r a l c r y s t a l s o f greenish-brown hornblende commonly twinned on the (100) p l a n e , and e x t e n s i v e l y r e p l a c e d by p i s t a c i t e and p e n n i n i t e (see f i g . $ 0 ) . The groundmass i s f i n e g r a i n e d and c o n s i s t s m a i n l y o f p o o r l y developed c r y s t a l s o f s a u s s u r i t i z e d p l a g i o c l a s e , some g r a i n s o f q u a r t z , s e r i c i t e and c a l c i t e . (2) L a t i t e porphyry - Two dykes of l a t i t e p orphyry r a n g i n g i n t h i c k n e s s from 10 t o 25 f e e t and s t r i k i n g n o r t h e r l y and n o r t h e a s t e r l y w i t h steep w e s t e r l y and s o u t h e a s t e r l y d i p s , were found i n the a r e a . I n hand specimen the r o c k i s brownish-gray, f i n e g r a i n e d p o r p h y r i t i c w i t h s u b h e d r a l t o e u h e d r a l c r y s t a l s o f p l a g i o c l a s e up t o 3 mm. i n diam e t e r . I n t h i n s e c t i o n the r o c k i s seen t o c o n t a i n 70 p e r c e n t s u b h e d r a l t o e u h e d r a l p h e n o c r y s t s o f p l a g i o c l a s e , 10 p e r c e n t g r e e n hornblende and l e s s t h a n 10 p e r c e n t a n h e d r a l q u a r t z g r a i n s s e t i n a f i n e - g r a i n e d m a t r i x of an h e d r a l f e l d s p a r and q u a r t z . The p l a g i o c l a s e i s s t r o n g l y zoned i n an o s c i l l a t o r y f a s h i o n , and averages An^j?; some c r y s t a l s are c l o u d y and e x t e n s i v e l y r e p l a c e d by s e r i c i t e , whereas o t h e r are c l e a r and f r e s h . Combination t w i n n i n g o f p l a g i o c l a s e c r y s t a l s a c c o r d i n g t o the a l b i t e and c a r l s b a d laws i s s t r i k i n g i n t h i s r o c k (see P i g . 31). - 79 -Hornblende c r y s t a l s are u s u a l l y c o r r o d e d , s u b h e d r a l l a t h s , commonly e n c l o s e d by l a r g e r p l a g i o c l a s e g r a i n s and r e p l a c e d by c a l c i t e , s e r i c i t e and c h l o r i t e . Quartz p h e n o c r y s t s are s c a r c e , i n v a r i a b l y a n h e d r a l , and w i t h s t r o n g l y rounded b o r d e r s . Common a c c e s s o r y m i n e r a l s are c a l c i t e , c h l o r i t e , a p a t i t e and p y r i t e . F i g . 31 Salmon R i v e r . Combination t w i n n i n g o f andesine p h e n o c r y s t s a c c o r d i n g t o t h e c a r l s b a d law i n l a t i t e p o rphyry. C r o s s e d n i c o l s (X 1 5 ) • (3) A l a s k i t e - Two a l a s k i t e dykes, a p p r o x i m a t e l y 2 5 f e e t wide and s t r i k i n g e a s t e r l y w i t h s t e e p n o r t h e r l y d i p s , were found i n the a r e a . I n hand specimen the r o c k i s v e r y l i g h t g r a y t o almost white and medium t o f i n e g r a i n e d p o r p h y r i t i c w i t h - 80 -s m a l l s u b h e d r a l p h e n o c r y s t s of q u a r t z and f e l d s p a r . I n t h i n s e c t i o n the t e x t u r e i s markedly p o r p h y r i -t i c , as s l i g h t l y zoned and s e r i c i t i z e d s u h h e d r a l p h e n o c r y s t s of andesine ( A n ^ ) , s t r o n g l y s e r i c i t i z e d K - f e l d s p a r and a n h e d r a l g r a i n s of q u a r t z w i t h rounded b o r d e r s s t a n d out F i g . 3 2 Salmon R i v e r . Quartz p h e n o c r y s t s w i t h embayed b o r d e r s , and myrmekitic groundmass i n p o r p h y r i t i c a l a s k i t e . C r o s s e d n i c o l s . (X 4-5). i n a f i n e - g r a i n e d groundmass of myrmekitic q u a r t z and K - f e l d s p a r (see F i g . 3 2 ) . Some s u b h e d r a l p l a t e s o f muscovite are a l s o p r e s e n t . A c c e s s o r y and a l t e r a t i o n m i n e r a l s are a p a t i t e , p y r i t e , l i m o n i t e , c a l c i t e and c h l o r i t e . - 81 -(b) Age The t h r e e t y p e s o f dykes d e s c r i b e d above c u t b o t h metamorphic and non-metamorphic r o c k s i n the map a r e a . They are p o s s i b l y r e l a t e d t o t h e Coast i n t r u s i o n s ( J o n e s , 1959, p. 7) which are r e p r e s e n t e d a few m i l e s t o the n o r t h of the map-area by a b a t h o l i t h i c mass. - 82 -CHAPTER V - SUMMARY AND CONCLUSIONS Jones (1959, pp. 4-7, 48 and 28) d e s c r i b e d u n c o n f o r m i t i e s between Shuswap and Cache Creek r o c k s at K e e f e r G u l c h , near L a v i n g t o n , a t B.X. Creek and at Salmon R i v e r . The p r e s e n t w r i t e r mapped thes e t h r e e areas i n d e t a i l . H i g h l y deformed r e g i o n a l metamorphic r o c k s and r e l a t i v e l y undeformed and unmetamorphosed sedimentary r o c k s , c h i e f l y v o l c a n i c wacke and b r e c c i a , w i t h some a r g i l l i t e and l i m e s t o n e , were found i n a l l t h r e e of t h e s e a r e a s . At K e e f e r G u l c h an u n c o n f o r m i t y c o u l d not be demonstrated or r e f u t e d . The exposed c o n t a c t between metamorphic and non-metamorphic r o c k s was found t o be a s t e e p l y d i p p i n g f a u l t , the amount of d i s p l a c e m e n t a l o n g which i s unknown. E v i d e n c e compatible w i t h the e x i s t e n c e of an u n c o n f o r m i t y i s t h e sharp d i f f e r e n c e i n grade of metamorphism, l i t h o l o g y , and s t r u c t u r e t h a t e x i s t s between metamorphic and non-metamorphic r o c k s , and the f a c t t h a t dykes c u t o n l y the metamorphic r o c k s . At B.X. Creek, as at K e e f e r G u l c h , an uncon-f o r m i t y c o u l d not be demonstrated or r e f u t e d . The c o n t a c t between metamorphic and non-metamorphic r o c k s was nowhere found exposed. The non-metamorphic r o c k s s t r i k e e a s t e r l y - 83 -and occupy the c e n t r a l part of the area. They are truncated to the east and to the west by gneiss of the Monashee group which s t r i k e northerly and northwesterly. As shown on plate I I , the contacts between these two u n i t s are believed to be two f a u l t s which s t r i k e northerly and dip steeply. At Salmon River strong evidence of the angular unconformity postulated by Jones was found. The uncon-formity separates highly deformed s c h i s t of the Chapperon group from r e l a t i v e l y undeformed and f r e s h sedimentary rocks which presumably belong to the Cache Creek or the Nicola group. I f these rocks are part of the Cache Creek group, then the underlying Chapperon rocks are pre-Permian. In t h i s case the metamorphism of the Chapperon group could be r e l a t e d to the Cariboo orogeny of post-Ordovician to pre - M i s s i s s i p p i a n time (White, 1959)» or to some e a r l i e r period of deformation. I f the rocks overlying the uncon-formity are part of the Nicola group, which i s at the present time regarded as r e s t i n g disconformably on the Cache Creek group ( C o c k f i e l d , 1948, p. 8), i t i s possible that the Chapperon group i s a part of the Cache Creek group. Metamorphism could then be r e l a t e d to the Cas s i a r orogeny of post-Upper Permian to pre-Upper T r i a s s i c time (White, 1959). - 84- -BIBLIOGRAPHY B a n c r o f t , M.F. 1921: Lardeau Map-Area, B r i t i s h Columbia; G e o l . Surv., Canada, Sum. Rept. 1921. B l o k h i n a , L . J . et a l . 1959: P r i n c i p l e s of c l a s s i f i c a t i o n and nomenclature  of the A n c i e n t V o l c a n i c C l a s t i c Rocks; I n t . G e o l . Rev., Dec. 1959. Brock, B.B. 1954-: The Metamorphism of the Shuswap T e r r a n e of B r i t i s h Columbia; J . G e o l . , V o l . 4^, pp. 675-C a i r n e s , C E . 1952: M i n e r a l Resources of N o r t h e r n Okanagan V a l l e y ,  B r i t i s h Columbia; G e o l . Surv., Canada, Sum. Kept. 1931, P t . A, pp. 66-109. 1956: K e t t l e R i v e r West H a l f ; Map, G e o l , Surv., Canada, Paper 57-21. 1959: The Shuswap Rocks of S o u t h e r n B r i t i s h Columbia;. P r o c , S i x t h P a c i f i c S c i e n c e Congress, V o l . 1, pp. 259-272. C o c k f i e l d , W.E. 194-8: Geology and M i n e r a l D e p o s i t s o f N i c o l a Map-Area,  B r i t i s h Columbia; G e o l . Surv., Canada, Mem. 24-9. D a l y , R.A. 1911: G e o l . Surv., Canada, Sum. Rept. 1911, pp. 167-T7D~: 1915: A G e o l o g i c a l Reconnaissance between G o l d e n and Kamloops, B r i t i s h Columbia; G e o l . Surv., Canada, Mem. 68. Dawson, G.M. 1878: E x p l o r a t i o n s i n B r i t i s h Columbia; G e o l . Surv., Canada, Kept. P r o g . ltf'/b-yy, pp. 16-14-9. 1879: P r e l i m i n a r y Report of the P h y s i c a l and G e o l o g i - c a l F e a t u r e s o f the S o u t h e r n P o r t i o n or tne  I n t e r i o r of B r i t i s h Columbia; G e o l . Surv., Canada, Rept. Prog. 1877-78, pp. 96B-101B. - 85 -BIBLIOGRAPHY (Continued) 1891: Note on the G e o l o g i c a l S t r u c t u r e o f the S e l k i r k Range; B u l l . G e o l . Soc. Amer.- V o l . 2, pp. 165-1%. 1898: Shuswap Sheet; G e o l . Surv., Canada, Map 604. F i s h e r , R.V. 1961: Proposed C l a s s i f i c a t i o n of V o l c a n i c l a s t i c Sediments and Rocks; G e o l . Soc. Amer., B u l l . 72, pp. 1409-1414. F i s k e , R.S. 1963: Subaqueous p y r o c l a s t i c f l o w s i n the Ohanapecosh  For m a t i o n , Washington; G e o i . Soc. Amer. B u l l . , v o l . ' / 4 , No. 4, A p r i l 1963, pp. 391-406. F o l k , R.L. 1954: The D i s t i n c t i o n Between G r a i n S i z e and M i n e r a l  C o m p o s i t i o n i n Sedimentary Rock Nomenclature; J o u r . G e o l . , V o l . bki, No. 4, July 1954, pp. 344-359. G i l l u l y , J . 1934: M i n e r a l O r i e n t a t i o n i n Some Rocks o f the Shuswap  T e r r a n e as a C l u e t o t h e i r Metamorphism; Amer. J . Sc., F i f t h S e r i e s , V o l . 28, pp. 182-201. Gunning, H.C. 1928: Geology and M i n e r a l D e p o s i t s o f the B i g Bend Map-Area, B r i t i s h Columbia; G e o l . Surv., Canada, Sum. Kept. i y * 8 . Harker, A. 1939: Metamorphism; B.P. Du t t o n and Co. I n c . , Second ET: Hay, R.L. 1952: The Terminology o f F i n e G r a i n e d D e t r i t a l V o l c a n i c  Rocks; J . Sed. P e t . , V o l . 22, No. 2, pp. 119-120. Hess, H.H. 1941: Pyroxenes of Common M a f i c Magmas; Amer. Min., V o l . 26, pp. 515-535, 573-595. 1949: Chemical C o m p o s i t i o n and O p t i c a l P r o p e r t i e s o f  Common G l l i P a r t 1, pp, C i n o p y r o x e n e s ; Amer. Min., V o l . 34, V21-666. - 86 -BIBLIOGRAPHY (Continued) Jones, A.G. 1959: Vernon Map-Area, B r i t i s h Columbia; Geol. Surv., Canada, Mem. 296. Kerr, P.P. 1959: O p t i c a l Mineralogy; McGraw-Hill Book Company Inc., T h i r d e d i t i o n . McConnell, R.G. and Brock, R.W. 1904: West Kootenay Sheet; Geol. Surv., Canada, Mag. Nasmith, H. 1962: Late G l a c i a l History and S u r f i c i a l Deposits of  the Okanagan V a l l e y , B r i t i s h Columbia; BriTj": C o l . DeptT of Mines and Pet. Res. B u l l . 46. Pe t t i j o h n , P.J. 1954: C l a s s i f i c a t i o n of Sandstones; J . Geol., V o l . 62, No. 4, July 19b4, pp. 360-365. 1956: Sedimentary Rocks; Harper and Bros., New York. Second e d i t i o n . Rice, H.M.A., and Jones, A.G. 1948: Salmon Arm, B r i t i s h Columbia; Geol. Surv., Canada, Paper 48-4. Ross, J.V. 1957: Combination Twinning i n Plagioclase Feldspars; Amer. Jour. Sc. V o l . 255, Nov. 1957, pp. fc>50-655-S c h o f i e l d , S.J. 1913: Geol. Surv., Canada, Sum. Rept. Turner, F.J. and Verhoogen, J . I960: Igneous and Metamorphic Petrology; McGraw-Hill Book Co. Inc.; Second Edxtion. Walker, J.F., Bancroft, M.F. and Gunning, H.C. 1929: Lardeau Map-Area, B r i t i s h Columbia; Geol. Surv., Canada, Mem. 161. Williams, H., Turner, F.J., and G i l b e r t , CM. 1953: Petrography; W.H. Freeman and Co. - 87 -BIBLIOGRAPHY (Continued) White, W.H. 1959: C o r d i l l e r a n T e c t o n i c s i n B r i t i s h Columbia: Am. As s . P e t . G e o l . V o l . 43, No. 1, Jan. 1959, pp. 60-100. W i n c h e l l , A.N. and W i n c h e l l , H. 1951: Elements of O p t i c a l M i n e r a l o g y ; John W i l e y and Sons, I n c . , London, F o u r t h E d i t i o n , P a r t 11. Yoder, H.S., and T i l l e y , C E . 1962: O r i g i n o f b a s a l t magmas: e x p e r i m e n t a l study  of n a t u r a l and s y n t h e t i c r o c k systems; J o u r , of P e t . V o l . 3, No. 3, Oct. 1962; C l a r e n d o n P r e s s , O x f o r d . 4 0 0 0 3 0 0 0 2 0 0 0 K E E F E R G U L C H 4 0 0 0 3 0 0 0 2 0 0 0 4 0 0 0 . 30 Q 0 : 2 0 0 0 K E E F E R G U L C H 4 0 0 0 Ck. ——;—Ti?;' ' ' A * » V Oft <l \ 3 0 0 0 2 0 0 0 4 0 0 0 3 0 0 0 2 0 0 0 4 0 0 0 3 0 0 0 2 0 0 0 B e s t mon compiled bv t h t B C Topoqroahto Division. ADDTCX. maa, d i d . 23° E. PLATE I KEEFER GULCH LEGEND CENOZOIC Pleistocene and Recent 1 1 G l a c i a l and l a c u s t r i n e sediment. UPPER PALAEOZOIC OR LATER Carboniferous ( ?) and Permian Cache Creek Group Green, dark-gray and buff volcanic breccia Green volcanic wacke . Mass ive to well - bedded. Green andesitic lava Gray to white limestone. Massive to thinly bedded. L o c a l l y f o s s i l i f e r o u s . PRE- UPPER PALAEOZOIC Pre- Carboniferous Mt. Ida Group (?) Dyke rocks : (a) Aplite and pegmatite, (b) O iabase. (c) Lamprophyre (d) Feldspar porphyry, (e) Biot i te mic rod io r i te . Green chlorite- biotite - hornblende phylllte. Pelitic micaceous schist (A) Brownish, ca lcareous . (B) B l u i s h - g r a y , a rg i l laceous 1 C lp 1 Green hornblende i c h i s t . (C) Siliceous (0) Micaceous . D a r k , gray a rg i l l aceous phyllite B e d d i n g , tops known. Inclined, vertical. B e d d i n g , tops unknown. Incl ined, v e r t i c a l . Jo int ing, inc l fned , vert ical . Schietoei ty , i n c l i n e d , ver t ica l . L ineat ion , plunging. Geological boundary, def in i te , indefinite. WW rt/vvwA ^ v ^ w , Fault , def ined , assumed. Shear zone. 3 ) (F) Foss i l local i ty . Outcrop a r e a . J L Highway. Country r o a d . Geology by V. Preto, 1963 Drawn by V P . P L A T E II B.X. C R E E K LEGEND C E N O Z O I C Pleistocene and Recent I I Glacial outwash U P P E R P A L A E O Z O I C OR L A T E R Post - Permian Alaskite porphyry, quartz veins Carboniferous ( ? ) and Permian Cache Creek Group Volcanic wacke (a) feldspathic ; (b) lithic Interbeds of breccia(br) and argillite (ag) P R E - U P P E R P A L A E O Z O I C P r e - Carboniferous Monashee Group Biotite-quartz - feldspar gneiss, hornblende gneiss. Cut by muscovite- quartz-feldspar pegmatite and quartz veins Impure quartzite (q ) ; tremolite rock (tr^  Bedding, tops unknown. Inclined, vertical Jointing; inclined, vertical Foliation; inclined, vertical 4 Lineation, plunging Geological boundary; definite, indefinite ivwvwv <\A A/V Fault J def ined, assumed O ' J t c r o p area ' ' Well- travelled road - - - — — Secondary road Flume H Building Base map by B . C . Topographic Division. Approx. mag. decl. 2 3 ° E Geology by V. Preto, 1963 Drawn by V. P 3 5 0 0 3 5 0 0 3 0 0 0 2 5 0 0 2 0 0 0 3 5 0 0 3 0 0 0 2 5 0 0 2 0 0 0 mm 3 0 0 0 2 5 0 0 2 0 0 0 B 3 5 0 0 3 0 0 0 2 5 0 0 2 0 0 0 P L A T E S A L M O N L E G E N D CEN0Z0IC Pleistocene and Recent G l a c i a l a n d f l uv ia t i l e o u t w a s h MESOZOIC Jurassic a n d / o r Cretaceous Dyke r o c k s ; (a) Hornb lende m ic rod io r i t e , (b) L a t i t e , (c) A lask i te , (d ) Quar tz ve ins UPPER PALAEOZOIC Permian or Upper Triassic Cache Creek or Nicola Group F e l d s p a t h i c g r a y w a c k e Al tered c rys ta l t j f f or lava . T n i n - b e d d e d / i t r i c - c r y s t a l tuff T h i n - b e d d e d , b l a c k a rg i l l i t e F i n e - to c o a r s e - g r a i n e d c a l c a r e n i t e B a s a l cong lomera te PRE-UPPER PALAEOZOIC Pre-Upper Triassic Old Dave Intrusions S e r p e n t i n i z e d u l t r ama f i c dykes Chapperon Group D a r k - g r a y to b lack m i c a c e o u s s c h i s t R i b b o n c h e r t R I V E R ~ \ B e d d i n g , t o p s k n o w n } i n c l i n e d , v e r t i c a l S c h i s t o s i t y ; i n c l i n e d , v e r t i c a l L ine a t i o n , p l u n g i n g - G e o l o g i c a l b o u n d a r y ; d e f i n e d , a s s u m e d y s 1 1 Z o n e of s h e a r i n g O u t c r o p a r e a 0 F o s s i l l o c a l i t y — — — — — S e c o n d a r y r o a d ^ ' B r i d g e B a s e m a p by T o p o g . Div. C a n a d a D e p t . of M i n e s and T e c h . Surveys Aporox. m a g . d e c l . 2 3 ° L. G e o l o g y t y V. P r e t o , I i>b3 D r a w n by V . P. 

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