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UBC Theses and Dissertations

Geology of the Crawford Bay map-area. Livingstone, Kent Wayne 1968

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GEOLOGY OF THE CRAWFORD BAY MAP-AREA by Kent Wayne L i v i n g s t o n e B . S c . j C a r l e t o n U n i v e r s i t y , 1 9 6 6 A t h e s i s s u b m i t t e d i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r t h e degree o f master o f s c i e n c e i n the Department o f Geology We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA May 1 9 6 8 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I ag r e e t h a t 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 Study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y p u rposes may be g r a n t e d by the Head o f my Department or by hits r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada - i -- i i -ABSTRACT The C r a w f o r d Bay map-area i s f i f t y square m i l e s on the e a s t s i d e o f Kootenay Lake, s o u t h e a s t e r n B r i t i s h C olumbia, and i s p a r t o f a r e g i o n a l s t r u c t u r a l b e l t , the Kootenay A r c , ( H e d l e y , 1955)• I t i s u n d e r l a i n by s t r o n g l y deformed and metamorphosed s t r a t a o f L a t e P r o t e r o z o i c t o p o s s i b l e M i d d l e P a l e o z o i c age. S i l l - l i k e b o d i e s and b o u d i n s o f metamorphosed a m p h i b o l i t e , and s u b o r d i n a t e p o s t -k i n e m a t i c g r a n i t i c i n t r u s i o n s and b a s i c dykes o f p r o b a b l e M e s o z o i c age a r e p r e s e n t i n the west p a r t o f t h e map-area. L i t h o l o g i c s u c c e s s i o n was det e r m i n e d by use> o f p r i m a r y s t r u c t u r e s i n t h e e a s t p a r t o f the map-area and by l i t h o l o g i c c o r r e l a t i o n i n the more h i g h l y metamorphosed w e s t e r n p a r t . H o r s e t h i e f Creek Group, Lower H a m i l l Group, Upper H a m i l l Group, Mohican and Badshot F o r m a t i o n s , and L a r d e a u Group comprise an apparent c o n f o r m a b l e s u c c e s s i o n . Rock-u n i t n o m e n c l a t u r e i s t h e same as u s e d f o r s i m i l a r s t r a t a i n the Kootenay A r c o f t h e L a r d e a u and Salmo a r e a s . However, f a u l t - b o u n d Upper H a m i l l i s composed o f s t r a t a w h i c h do n o t have d e f i n e d l i t h o l o g i c e q u i v a l e n t s o u t s i d e t h e map-area and more d e t a i l e d s t u d y o f t h i s p a r t o f the s u c c e s s i o n i s suggested. The sequence i s u n f o s s i l i f e r e o u s and - i i i -and age o f the s t r a t a i s based on c o r r e l a t i o n o f Badshot F o r m a t i o n w i t h Badshot o u t s i d e the map-area t h a t has y i e l d e d A r c h e o c y a t h i d s o f l a t e Lower Cambrian age. Three phases o f d e f o r m a t i o n , o f v a r i a b l e i n t e n s i t y , a r e r e c o g n i z e d w i t h i n the map-area. Phase one f o l d s a r e the e a r l i e s t t e c t o n i c event and d e l i n e a t e the main s t r u c t u r a l t r e n d . Three major f o l d s , o u t l i n e d by s t r a t i g r a p h i c mapping, the P l a i d Lake s y n c l i n e , t h e Washout Creek s y n c l i n e , and the C r a w f o r d Bay synform, a r e b e l i e v e d t o be phase one s t r u c t u r e s . E a r l y phase f o l d s a r e i s o c l i n a l " s i m i l a r " w i t h a x i a l p l a n e s p a r a l l e l t o g r o s s l i t h o l o g i c l a y e r i n g . F o l d axes and r e l a t e d p e n e t r a t i v e m i n e r a l l i n e a t i o n p l u n g e up t o 20° n o r t h w a r d e x c e p t where l o c a l l y deformed by subsequent s t r u c t u r e s . Only s m a l l s c a l e phase two f o l d s a r e r e c o g n i z e d . These a r e asymmetric " s i m i l a r " f o l d s w i t h s o u t h e a s t t r e n d i n g a x i a l p l a n e s w h i c h d i p m o d e r a t e l y t o the southwest, and westward p l u n g i n g f o l d axes. M a j o r f a u l t s may have formed d u r i n g e i t h e r phase o f d e f o r m a t i o n . K i n k s and r e l a t e d q u a r t z v e i n s formed d u r i n g phase t h r e e d e f o r m a t i o n . F o l d i n g o f b e d d i n g by phase t h r e e k i n k s i s c o n s i d e r e d t o be f l e x u r a l - s l i p . R e g i o n a l metamorphism i s s y n k i n e m a t i c w i t h phase one and two d e f o r m a t i o n . C u l m i n a t i o n o f - i v -metamorphism appears t o be p o s t - f a u l t i n g and p o s t -phase two d e f o r m a t i o n . Phase t h r e e d e f o r m a t i o n i s post-metamorphic. C h l o r i t e , b i o t i t e , g a r n e t , d i o p s i d e , and s i l l i m a n i t e zones d e l i n e a t e an i n c r e a s i n g metamorphic g r a d i e n t from e a s t t o west. D i s t r i b u t i o n c o e f f i c i e n t s , IC, = Mg/Fe , / ' D D / g a r n e t / M g / F e - b i o t i t e , o f Mg and Fe i n c o e x i s t i n g g a r n e t and b i o t i t e p a i r s i n Mohican F o r m a t i o n , a r e l a r g e r w i t h i n c r e a s i n g metamorphic grade from the e a s t l i m b t o the west l i m b o f the Cr a w f o r d Bay synform. - V -TABLE OF CONTENTS CHAPTER ONE INTRODUCTION 1 A. G e n e r a l Statement 1 B. P r e v i o u s Work 3 C. G e n e r a l Geology 4 D. Acknowledgments 6 CHAPTER TWO STRATIGRAPHY 8 A. G e n e r a l Statement 8 B. R o c k - u n i t D e s c r i p t i o n 11 1. H o r s e t h i e f Creek Group 11 2. Lower H a m i l l Group 11 3- Upper H a m i l l Group 14 4. Mohican F o r m a t i o n 15 5- Badshot F o r m a t i o n 17 6 . L a r d e a u Group 18 7. A m p h i b o l i t e 19 C. Age and C o r r e l a t i o n 21 CHAPTER THREE STRUCTURE 27 A. G e n e r a l Statement 27 B. Phase One 30 C. Phase Two 44 D. Phase Three 49 E. F a u l t s 57 CHAPTER FOUR METAMORPHISM 60 - v i -Ta b l e o f c o n t e n t s c o n t i n u e d CHAPTER FIVE CHAPTER SIX' INTRUSIVE ROCKS SUMMARY 76 82 FIGURES F i g u r e 1 F i g u r e 2 F i g u r e 3 F i g u r e 4 F i g u r e 5 F i g u r e 6 F i g u r e 7 F i g u r e 8 F i g u r e 9 F i g u r e 10 F i g u r e 11 Index map showing t h e s i s a r e a . 2 Map - Geology o f t h e Cr a w f o r d Bay Map-area. ( i n p o c k e t ) Stereogram, P l a i d Lake s y n c l i n e . 32 Stereogram, Washout Creek s y n c l i n e . 37 Schematic c r o s s - s e c t i o n o f t h e 38 map-area. Stereogram, Badshot F o r m a t i o n and ^2 Mohican F o r m a t i o n , e a s t l i m b o f Cr a w f o r d Bay synform. Stereogram, Mohican F o r m a t i o n , 42 o v e r t u r n e d s y n c l i n e below Mohican-Badshot c o n t a c t , e a s t l i m b o f Cr a w f o r d Bay synform. Stereogram, L a r d e a u A, h i g h ^3 e l e v a t i o n s on r i d g e west o f P r e a c h e r Creek, e a s t l i m b o f Cr a w f o r d Bay synform. Stereogram, L a r d e a u Group, o v e r t u r n e d ^3 west l i m b o f Cra w f o r d Bay synform a r e a , west o f C r a w f o r d Bay. Stereogram, phase two a x i a l p l a n e s ^5 and f o l d a x e s , C r a w f o r d Bay synform, e a s t l i m b . Stereogram, phase t h r e e k i n k f o l d , 55 L a r d e a u A, C r a w f o r d Bay synform, e a s t l i m b . - v i i T a b l e o f c o n t e n t s c o n t i n u e d F i g u r e 12 F i g u r e 13 F i g u r e 14 F i g u r e 15 F i g u r e 16 F i g u r e 17 Stereogram, phase t h r e e k i n k f o l d , 56 Mohican F o r m a t i o n , e a s t l i m b o f Cra w f o r d Bay synform. Stereogram, phase t h r e e k i n k f o l d , 56 Mohican F o r m a t i o n , e a s t l i m b o f Cra w f o r d Bay synform. M i n e r a l assemblages r e c o g n i z e d i n 66 h i g h grade p e l i t i c s c h i s t and c a l c - s i l i c a t e g n e i s s , C r a w f o r d Bay synform. C o m p o s i t i o n o f g a r n e t s i n p e l i t i c 70 s c h i s t o f Mohican F o r m a t i o n I n the C r a w f o r d Bay synform. Mg/Mg + Fe i n c o e x i s t i n g g a r n e t - 73 b i o t i t e p a i r s , Mohican F o r m a t i o n , C r a w f o r d Bay synform. ( A n d r a d i t e c o n s i d e r e d t o be minor component o f g a r n e t ) . Mg/Mg + Fe i n c o e x i s t i n g g a r n e t - 74 b i o t i t e p a i r s , Mohican F o r m a t i o n , C r a w f o r d Bay synform. ( G r o s s u l a r i t e c o n s i d e r e d t o be minor component o f g a r n e t ) . TABLES T a b l e 1 T a b l e o f f o r m a t i o n s . T a b l e 2 L i t h o l o g i c c o r r e l a t i o n o f se d i m e n t a r y r o c k s . T a b l e 3 Metamorphic m i n e r a l assemblages i n t he Cr a w f o r d Bay map-area. T a b l e 4 R e f r a c t i v e i n d i c e s and c e l l edge d e t e r m i n a t i o n s o f g a r n e t , Mohican F o r m a t i o n . T a b l e 5 D e t e r m i n a t i o n o f Mg/Mg + Fe i n b i o t i t e , Mohican F o r m a t i o n . 9 22 61 68 69 - v i i i -Table of contents continued Table 6 Distribution coefficients of Mg 72 and Pe i n coexisting b i o t i t e and garnet pairs, Mohican Formation. PLATES Frontispiece Mount Crawford, elevation 7 6 7 5 feet. i Plate 1 Cross-bedding, Three Sisters 12 Formation. Plate 2 Amphibolite s i l l - l i k e bodies. 20 Plate 3 Phase one minor folds, Mohican 28 Formation, Riondel peninsula. Plate 4 Rotated boudin of ca l c - s i l i c a t e 29 gneiss, Lardeau A, west limb of Crawford Bay synform. Plate 5 Phase one minor folds i n 33 adjacent outcrops, Upper Hamill Group, east limb of Plaid Lake syncline near core zone. Plate 6 Phase one minor folds, Upper 35 Hamill Group, west limb of Washout Creek syncline. Plate 7 Phase one antiform, Mohican 40 Formation, Riondel peninsula. Plate 8 Phase one synform, Mohican 40 Formation, Riondel peninsula. Plate 9 Phase two minor folds and phase 46 one minor folds, Mohican Formation, east limb of Crawford Bay synform. Plate 10 Phase two minor folds and related 46 cleavage and boudinage, Mohican Formation, Crawford Creek. Plate 11 Phase one synform, Lardeau A, west limb of Crawford Bay synform. 49 - i x -T a b l e o f c o n t e n t s c o n t i n u e d P l a t e 12 P l a t e 13 P l a t e 14 P l a t e 15 P l a t e 16 P l a t e 17 P l a t e 18 P l a t e 19 P l a t e 20 P l a t e 21 Phase t h r e e k i n k , Mohican F o r m a t i o n , R i o n d e l p e n i n s u l a . Phase one minor synform, Mohican F o r m a t i o n , R i o n d e l p e n i n s u l a . Phase one synform deformed b y phase t h r e e k i n k . Phase t h r e e k i n k , F o r m a t i o n . Mohican Phase t h r e e k i n k , q u a r t z i t e i n Lard e a u A. T r e m o l i t e p o r p h y r o b l a s t s I n m a r b l e , Mohican F o r m a t i o n , n e a r e a s t side" o f C r a w f o r d Bay. F i n e - g r a i n e d g r a n i t i c dyke i n t r u d i n g L a r d e a u A s t r a t a w h i c h i s deformed by phase t h r e e k i n k s . F i n e - g r a i n e d g r a n i t i c dyke i n t r u d i n g f o l i a t e d p e g m a t i t e s i l l i n L a r d e a u A s t r a t a . Augens o f w h i t e p e g m a t i t e i n Larde a u B, a x i a l zone o f C r a w f o r d Bay synform. B a s i c dyke i n t r u d i n g Mohican F o r m a t i o n , R i o n d e l p e n i n s u l a . 51 52 52 53 53 74 77 77 79 80 CHAPTER ONE INTRODUCTION A. GENERAL STATEMENT T h i s t h e s i s d e s c r i b e s t h e g e o l o g y o f f i f t y square m i l e s i n t h e C r a w f o r d Bay a r e a on t h e e a s t s i d e o f Kootenay Lak e , s o u t h e a s t e r n B r i t i s h Columbia ( F i g u r e 1). The a r e a i s a s m a l l p a r t o f a r e g i o n a l s t r u c t u r a l s a l i e n t known as t h e Kootenay A r c ( H e d l e y , 1955). A c c e s s i n t h e a r e a i s p r o v i d e d by P r o v i n i c i a l Highway 3A a l o n g t h e e a s t s h o r e l i n e o f Kootenay Lake t o R i o n d e l , B r i t i s h Columbia. I n a d d i t i o n , a good g r a v e l l o g g i n g r o a d a l o n g t h e n o r t h s i d e o f C r a w f o r d Creek p r o v i d e s easy a c c e s s t o t h e i n t e r i o r o f t h e map-area. Some l o g g i n g roads r e q u i r i n g f o u r - w h e e l d r i v e v e h i c l e s a r e p r e s e n t t o h i g h e r e l e v a t i o n s . The map-area i s p a r t o f t h e P u r c e l l M o u n t a i n s . R e l i e f i s h i g h l y v a r i a b l e , r i s i n g r a p i d l y from about 1745 f e e t e l e v a t i o n a t Kootenay Lake t o 7000 f e e t about t h r e e m i l e s i n l a n d . Most o f t h e mountain s i d e s a r e ste e p and f o r e s t e d . Outcrop i n f o r e s t e d a r e a s i s l i m i t e d t o r i d g e s and c r e e k beds. Ourcrop i s p r e s e n t on t h e n o r t h s l o p e s o f u p l a n d r i d g e s and pe a k s , a l o n g t h e l a k e s h o r e , and r o a d c u t s on t h e l a k e s h o r e highway. Rocks i n t h e map-area comprise s t r o n g l y deformed and metamorphosed s t r a t a and a s s o c i a t e d p l u t o n i c r o c k s r a n g i n g i n age from P r o t e r o z o i c t o p r o b a b l e M i d d l e P a l e o z o i c , and g r a n i t i c i n t r u s i o n s o f p r o b a b l e M e s o z o i c age. The gure 1 Index map showing t h e s i s a r e a . - 3 -t h e s i s a t t e m p t s t o d e s c r i b e the s t r a t i g r a p h y , s t r u c t u r e and metamorphism o f t h e s e r o c k s . F i e l d work was c a r r i e d out d u r i n g June, J u l y and p a r t s o f August and September, 196j. Mapping was done a t a s c a l e f o u r i n c h e s p e r m i l e w i t h t h e a i d o f 1958 B r i t i s h Columbia Government a i r p h o t o s . The base map i s an enlargement o f 1:50,000 N a t i o n a l T o p o g r a p h i c maps o f t h e a r e a . F i e l d d a t a was l o c a t e d by d i r e c t a i r p h o t o o b s e r v a t i o n , b a r o m e t r i c r e a d i n g s f o r e l e v a t i o n and compass b e a r i n g s where n e c e s s a r y . S t a t i o n s were t r a n s f e r e d f r o m a i r p hotos by r a d i a l l i n e p l o t t i n g and e l e v a t i o n d e t e r m i n a t i o n s by barometer. B. PREVIOUS WORK The s t u d y a r e a ( F i g u r e 2, i n p o c k e t ) , l i e s w i t h i n t h e Kootenay A r c , a br o a d a r c u a t e s t r u c t u r e i n s o u t h e a s t B r i t i s h Columbia w h i c h was o u t l i n e d by He d l e y (1955). Gross s t r a t i g r a p h i c r e l a t i o n s h i p s o f t h e Kootenay A r c r o c k s were f i r s t e s t a b l i s h e d by Walker, (1928), and Walker and B a n c r o f t , (1929), w o r k i n g i n t h e Lar d e a u map-area, f i f t y m i l e s t o t h e n o r t h o f t h e p r e s e n t a r e a . More r e c e n t l y , R i c e (194-1) d e s c r i b e d t h e ge o l o g y i m m e d i a t e l y e a s t and west o f Kootenay Lake i n t h e N e l s o n , e a s t - h a l f , map-area. D e t a i l e d work by F y l e s and Eastwood, (1962) r e s u l t e d i n s u b d i v i s i o n o f t h e l a r g e r o c k - u n i t s i n t o f o r m a t i o n s . To the s o u t h , i n t h e Salmo a r e a , the - 4 -f i r s t s t r a t i g r a p h i c s t u d y o f Kootenay A r c r o c k s was made "by Walker (1934). Subsequent r e v i s i o n s and s u b d i v i s i o n s were made i n s t u d i e s by Mathews (1953)> P y l e s and H e w l e t t , (1959), and L i t t l e , ( i960). U n p u b l i s h e d s t u d i e s o f p o r t i o n s o f t h e map-area have been made by Cominco L i m i t e d a t v a r i o u s t i m e s and P. Crosby, PhD. t h e s i s , H a r v a r d U n i v e r s i t y , i960. Because o f s i m i l a r i t i e s i n s t r a t i g r a p h y between t h e Cr a w f o r d Bay a r e a , t h e L a r d e a u map-area t o t h e n o r t h and t h e Salmo a r e a t o t h e s o u t h , r o c k -u n i t n o m e n c l a t u r e e s t a b l i s h e d i n t h e s e a r e a s i s u s e f u l and a p p l i c a b l e i n t h e C r a w f o r d Bay a r e a . C. GENERAL GEOLOGY The C r a w f o r d Bay a r e a c o n t a i n s h i g h l y deformed s t r a t a r a n g i n g i n age from l a t e P r o t e r o z o i c t o p o s s i b l e M i d d l e P a l e o z o i c . I n g e n e r a l , t h e s u c c e s s i o n d i p s west w i t h t h e r e g i o n a l s t r a t i g r a p h i c top t o t h e west. The o l d e s t r o c k s a r e H o r s e t h i e f Creek Group w h i c h c r o p out i n t h e e a s t e r n p a r t o f t h e map-area. Three r o c k - u n i t s a r e r e c o g n i z e d w i t h i n t h e c o n f o r m a b l y o v e r l y i n g H a m i l l Group, t h e Three S i s t e r s F o r m a t i o n , Q u a r t z i t e Range F o r m a t i o n and Upper H a m i l l Group. Cross-bedded sandstone o f t h e Three S i s t e r s F o r m a t i o n s i s c o n f o r m a b l y o v e r l a i n b y q u a r t z i t e o f Q u a r t z i t e Range F o r m a t i o n . A p r o b l e m a t i c r o c k - u n i t w h i c h o v e r l i e s t h e Q u a r t z i t e Range i s r e f e r r e d t o as Upper H a m i l l Group. L i t h o l o g i e s c o m p r i s i n g t h e Upper H a m i l l a r e micaceaus q u a r t z i t e , m i n o r p h y l l i t e , s c h i s t , and m a r b l e . The top o f t h e Upper H a m i l l i s n o t r e c o g n i z e d i n t h e map-area. I t s w e s t e r n c o n t a c t i s t h e P r e a c h e r Creek f a u l t where d i s t i n c t i v e m a s s i v e m a r b l e forms t h e l o w e s t member o f t h e Mohican F o r m a t i o n . I n t e r b e d d e d m a s s i v e m a r b l e , g r a n i t i c and c a l c - s i l i c a t e g n e i s s , s c h i s t , and minor micaceous q u a r t z i t e comprise t h e Mohican. The Badshot F o r m a t i o n forms an apparent c o n f o r m a b l e marker f o r m a t i o n o f medium g r e y marble. A r c h e o c y a t h i d s o f l a t e Lower Cambrian age a r e found i n t h e Badshot o u t s i d e the. map-area. Two r o c k - u n i t s , r e c o g n i z e d i n t h e o v e r l y i n g L a r d e a u Group a r e d i s t i n g u i s h e d on t h e b a s i s o f c a l c - s i l i c a t e m i n e r a l s . L a r d e a u D i v i s i o n A ( h e r e i n a f t e r , L a r d e a u A ) , w h i c h o v e r l i e s Badshot i n a p p a r e n t c o n f o r m i t y , i s composed o f c a l c - s i l i c a t e g n e i s s , s c h i s t , m i n or miceaceous q u a r t z i t e , and m a r b l e . L a r d e a u B i s g r e y s c h i s t , miceaceous q u a r t z i t e , and g r a n i t i c g n e i s s . S i l l s and b o u d i n s o f metamorphosed a m p h i b o l i t e a r e p r e s e n t i n t h e L a r d e a u Group, Mohican F o r m a t i o n , and Upper H a m i l l Group. M i n o r s m a l l g r a n i t i c s t o c k s , g r a n i t e p e g m a t i t e s i l l s and dykes, and b a s i c dykes a r e p r e s e n t i n t h e west p a r t o f t h e map-area. Three phases o f d e f o r m a t i o n a r e r e c o g n i z e d i n t h e map-area. The p r e s e n t form o f t h e e a r l y phase f o l d s i s i s o c l i n a l s i m i l a r f o l d s w i t h a x i a l p l a n e s p a r a l l e l t o g r o s s l i t h o l o g i c l a y e r i n g . M i n e r a l l i n e a t i o n and - 6 -q u a r t z r o d d i n g i s commonly p a r a l l e l t o t h e axes o f t h e s e f o l d s . B o t h l a r g e and s m a l l s c a l e f i r s t phase f o l d s a r e p r e s e n t . Only s m a l l s c a l e second phase f o l d s have "been r e c o g n i z e d i n t h e map a r e a . A x i a l p l a n e s o f second phase s i m i l a r f o l d s g e n e r a l l y t r e n d s o u t h e a s t and have a moderate t o steep southwest d i p . M a j o r f a u l t s p r e s e n t i n t h e map-area may have formed d u r i n g e i t h e r phase o f d e f o r m a t i o n . Much o f t h e movement may have been d u r i n g c l o s u r e .of t h e f i r s t phase f o l d s by second phase d e f o r m a t i o n . The t h i r d phase i s post-metamorphic. K i n k s and q u a r t z v e i n s a r e r e l a t e d t o t h i s phase o f d e f o r m a t i o n . R e g i o n a l rnetamorphism i s s y n k i n e m a t i c w i t h t h e f i r s t phase o f d e f o r m a t i o n and i s pre-phase t h r e e d e f o r m a t i o n . C h l o r i t e , b i o t i t e , g a r n e t , d i o p s i d e and s i l l i m a n i t e zones a r e r e c o g n i z e d w i t h t h e h i g h e s t grade t o t h e west. Zone b o u n d a r i e s appear t o be p a r a l l e l t o major s t r u c t u r a l t r e n d s . R e t r o g r a d e rnetamorphism i s l o c a l l y a s s o c i a t e d w i t h t h e emplacement o f g r a n i t e p e g m a t i t e dykes and s i l l s , and p o s s i b l y w i t h phase t h r e e d e f o r m a t i o n . D. ACKNOWLEDGMENTS The m a n u s c r i p t was c r i t i c a l l y r e v i e w e d by Dr. J . V . Ross. F i e l d work was f i n a n c e d by p a r t o f N a t i o n a l R e s e a r c h C o u n c i l Grant awarded t o Dr. Ross. A d d i t i o n a l s u p p o r t f o r s t u d y came from t h e C o n s o l i d a t e d M i n i n g and S m e l t i n g Graduate R e s e a r c h F e l l o w s h i p and Chevron S t a n d a r d L i m i t e d Graduate F e l l o w s h i p Award. - 7 -C e d r i c Hughes p r o v i d e d a b l e a s s i s t a n c e w i t h f i e l d work. S t r u c t u r a l i n f o r m a t i o n u s e d i n F i g u r e 2 ( i n p o c k e t ) f o r the r i d g e n o r t h w e s t o f B l u e b e l l M o u n t a i n , the upper p a r t o f I n d i a n Creek a r e a , and f o r two m i l e s s o u t h o f R i o n d e l p e n i n s u l a a l o n g t h e l a k e s h o r e , i s t a k e n f r o m an u n p u b l i s h e d r e c o n n a i s s a n c e f i e l d map b y J . T. F y l e s w i t h h i s p e r m i s s i o n . R e s p o n s i b i l i t y f o r l i t h o l o g i c d i v i s i o n i n t h e s e a r e a s i s assumed by t h e a u t h o r . - 8 -CHAPTER TWO STRATIGRAPHY' A. GENERAL STATEMENT The t h e s i s c o m p r i s e s a s t u d y o f r e g i o n a l l y metamorphosed s t r a t a o f P a l e o z o i c and p r o b a b l e l a t e :.• P r o t e r o z o i c age. L i t h o l o g i c s u c c e s s i o n i s e s t a b l i s h e d i n t h e e a s t e r n p a r t o f t h e map-area by use o f p r i m a r y s e d i m e n t a r y s t r u c t u r e s . I n t h e more h i g h l y metamorphosed w e s t e r n p a r t , p r i m a r y s t r u c t u r e s a r e absent and t h e s u c c e s s i o n i s det e r m i n e d by c o r r e l a t i o n w i t h s i m i l a r r o c k - u n i t s o u t s i d e t h e map-area. Gross s t r u c t u r e i s o u t l i n e d by r e p e t i t i o n o f d i s t i n c t i v e f o r m a t i o n s . H o r s e t h i e f Creek Group, H a m i l l Group, Mohican and Badshot F o r m a t i o n s , and L a r d e a u Group comprise an app a r e n t conformable s u c c e s s i o n ( T a b l e 1). The sequence i s u n f o s s i f e r o u s ; however, t h e Badshot F o r m a t i o n i s c o n s i d e r e d Lower Cambrian on t h e b a s i s o f c o r r e l a t i o n w i t h Badshot F o r m a t i o n o u t s i d e t h e map-area w h i c h c o n t a i n s A r c h e o c y a t h i d s ( L i t t l e , i960, Wheeler, 1963). R e l a t i o n s h i p between o r i g i n a l and o b s e r v e d t h i c k n e s s i s u n c e r t a i n because o f i n t e n s e d e f o r m a t i o n . D e f o r m a t i o n m a i n l y c o n s i s t s o f s i m i l a r i s o c l i n a l f o l d i n g i n w h i c h a s s o c i a t e d m i n o r f o l d s d i s p l a y c o n s i d e r a b l e l o c a l r e p e t i t i o n , t h i n n i n g and t h i c k e n i n g o f s t r a t a . O l d e s t s t r a t a a r e t h e H o r s e t h i e f Creek Group - 9 -TABLE 1 TABLE OF FORMATIONS GROUP FORMATION OR LITHOLOGY DIVISION Basic dykes Intrusive contact.. Granite pegmatite s i l l s and dykes. Intrusive contact. Granitic stocks. Intrusive contact. Amphibolite s i l l - l i k e bodies, minor dykes Probable intrusive contact. LARDEAU Lardeau B grey schist and granitic gneiss, minor micaceous quartzite. Probable conformity Lardeau A mainly c a l c - s i l i c a t e gneiss and granitic gneiss and schist, minor marble, massive quartzite. Apparent conformity-contact not exposed in. map area. Badshot limy and dolomitic marble, subordinate garnet schist and micaceous quartzite. Probable conformity - 10 -TABLE OP FORMATIONS c o n t i n u e d P r o b a b l e c o n f o r m i t y . Mohican l i m y and d o l o m i t i c m a r b l e , t r e m o l i t i c m a r b l e , w h i t e q u a r t z i t e , g r a n i t i c and c a l c -s i l i c a t e g n e i s s , g a r n e t s c h i s t , and q u a r t z o s e s c h i s t . F a u l t c o n t a c t . UPPER HAMILL Upper p a r t , Washout Creek s y n c l i n e m a i n l y g r e y micaceous q u a r t z i t e , and- q u a r t z o s e s c h i s t , m i n or m a r b l e , d i s t i n c t i v e marker o f h o r n b l e n d e - c h l o r i t e s c h i s t . F a u l t c o n t a c t . Lower p a r t , P l a i d Lake s y n c l i n e m a i n l y c h l o r i t i c s c h i s t and impure q u a r t z i t e , m i n or brown l a m i n a t e d sandstone, g r e y l a m i n a t e d l i m e s t o n e and c a l c e r e o u s s c h i s t . A p p arent c o n f o r m i t y - c o n t a c t n o t exposed i n map a r e a . LOWER HAMILL Q u a r t z i t e Range l i g h t c o l o u r e d q u a r t z i t e , minor p h y l l i t e and impure q u a r t z i t e . G r a d a t i o n a l c o n t a c t . Three S i s t e r s j g r e y a r k o s i c sandstone, minor p h y l l i t e . A pparent c o n f o r m i t y - c o n t a c t n o t exposed i n map a r e a . HORSETHIEF CREEK Upper p a r t green and brown p h y l l i t e and sandy p h y l l i t e . Lower l i m i t o f mapping. - 11 -i n t h e e a s t p a r t o f t h e map-area. I n g e n e r a l , t h e s u c c e s s i o n i s younger t o t h e west, a l t h o u g h r e p e t i t i o n i s r e c o g n i z e d i n t h r e e major f o l d s . B. ROCK-UNIT DESCRIPTION 1. HORSETHIEF CREEK GROUP H o r s e t h i e f Creek Group, named by Walker (193^), i s a t h i c k s e c t i o n o f m a i n l y a r g i l l a c e o u s r o c k s . I n t h e map-area, o n l y H o r s e t h i e f Creek n e a r t h e upper c o n t a c t Ttfas examined. Here, l i t h o l o g i e s a r e t h i n - b e d d e d green p h y l l i t e and sandy p h y l l i t e . 2. LOWER HAMILL GROUP THREE SISTERS FORMATION Three S i s t e r s F o r m a t i o n was named and d e s c r i b e d b y Walker (193*0 i n t h e Salmo a r e a . I n t h e map-area, t h e f o r m a t i o n i s found o n l y on t h e e a s t l i m b o f t h e P l a i d Lake s y n c l i n e . Sedimentary s t r u c t u r e s i n sandstone i n d i c a t e a c o n t i n u o u s s e c t i o n f a c i n g west. L i t h o l o g i e s o f t h e f o r m a t i o n a r e medium gr e y a r k o s i c s a n d s t o n e , l o c a l l y c o n g l o m e r a t i c , w i t h i n t e r b e d s o f g r e y p h y l l i t e . Sandstone beds v a r y i n t h i c k n e s s up t o t h r e e f e e t and u s u a l l y c o n t a i n c r o s s -beds and s c o u r - a n d - f i l l s t r u c t u r e s . ( P l a t e l ) . - 12 -PLATE 1. C r o s s - b e d d i n g , Three S i s t e r s F o r m a t i o n ; d i h e d r a l a n g l e i s 49°; viewed s o u t h west; hammer i s 15 i n c h e s . C r o s s - b e d d i n g d i h e d r a l a n g l e s v a r y from 27° t o 57° and a r e thus o v e r s t e e p e n e d by f o l d i n g . Most c r o s s - b e d s i n the l o w e r p a r t o f the f o r m a t i o n i n d i c a t e a d i r e c t i o n o f t r a n s p o r t from the west. B o t h e a s t and west d i p p i n g f o r e s e t beds a r e p r e s e n t i n the m i d d l e and upper p a r t , s u g g e s t i n g o s c i l l i a t i o n o f d e p o s i t i o n s ! c o n d i t i o n s . The base o f the Three S i s t e r s F o r m a t i o n i s n o t exposed i n the map-area. I n t h i s t h e s i s , t h e base o f the f o r m a t i o n i s mapped where ma s s i v e sandstone a b r u p t l y c r o p s out above a s e c t i o n o f p o o r exposure presumably u n d e r l a i n by sandy p h y l l i t e o f the H o r s e t h i e f Creek Group. R i c e (19^1) c o n s i d e r s t h i s f o r m a t i o n to c o n f o r m a b l y o v e r l i e p h y l l i t e o f h i s H o r s e t h i e f Creek - 13 -S e r i e s . The top o f t h e f o r m a t i o n i s g r a d a t i o n a l where Three S i s t e r s sandstone i s i n t e r b e d d e d w i t h q u a r t z i t e and p h y l l i t e o f Q u a r t z i t e Range F o r m a t i o n . The uppermost bed o f c o a r s e sandstone i s us e d t o d e f i n e t h e top o f t h e Three S i s t e r s F o r m a t i o n i n t h e map-area. T h i s usage f o l l o w s L i t t l e ( I 9 6 0 , p. 22). QUARTZITE RANGE FORMATION Walker (193*0, i n t h e Salmo a r e a , o r i g i n a l l y named and d e s c r i b e d t h e Q u a r t z i t e Range F o r m a t i o n . S u b s e q u e n t l y i t has been s t u d i e d i n d e t a i l by Mathews (1953)5 who r e c o g n i z e d members w i t h i n t h e f o r m a t i o n , and a l s o by F y l e s and H e w l e t t , (1959)* and L i t t l e ( i960). Q u a r t z i t e Range F o r m a t i o n i s b e s t exposed on Mount C r a w f o r d , t h e h i g h e s t peak i n t h e map-area (see F r o n t i s p i e c e ) . Here, t h e f o r m a t i o n i s p a r t o f t h e e a s t l i m b o f t h e P l a i d Lake s y n c l i n e . L o c a l c r o s s - l a m i n a t i o n i n d i c a t e s t r a t a f a c e n o r t h w e s t . E l s e w h e r e , t h e upper p a r t o f t h e f o r m a t i o n forms a pr o m i n e n t southwest r i d g e n e a r P r e a c h e r Creek. A t t h i s l o c a t i o n t h e f o r m a t i o n appears t o be i n f a u l t c o n t a c t w i t h younger Upper H a m i l l s t r a t a t o t h e e a s t and c o n f o r m a b l y o v e r l a i n by s i m i l a r s t r a t a t o t h e west. V a r i c o l o r e d q u a r t z i t e and s u b o r d i n a t e p h y l l i t e a r e t h e main l i t h o l o g i e s w h i c h comprise t h e f o r m a t i o n . I n t h e l o w e r p a r t , q u a r t z i t e i s f l a g g y bedded w i t h - 14 -p h y l l i t i c p a r t i n g s and minor t h i n i n t e r b e d s . S i x t y t o e i g h t y f e e t o f m a i n l y p h y l l i t e , l o c a l l y c a l c a r e o u s , and micaceous g r e y q u a r t z i t e , form a d i s t i n c t i v e member i n th e l o w e r m i d d l e p a r t o f the f o r m a t i o n . E l s e w h e r e , Q u a r t z i t e Range c o n s i s t s p r i m a r l y o f l i g h t c o l o r e d f l a g g y t o m a s s i v e q u a r t z i t e . Cross l a m i n a t i o n and r i p p l e marks a r e l o c a l l y p r e s e n t . The base o f t h e Q u a r t z i t e Range F o r m a t i o n i s d e f i n e d above. M a s s i v e w h i t e q u a r t z i t e , w h i c h forms a p r e c i p i t o u s d i p s l o p e on t h e n o r t h w e s t f a c e o f Mount C r a w f o r d , i s t h e top o f t h e f o r m a t i o n . 3. '• UPPER HAMILL GROUP Two d i s t i n c t a r e a s a r e u n d e r l a i n by r o c k s o f Upper H a m i l l Group. The l a r g e r a r e a i s Washout Creek s y n c l i n e w h i c h i s b o r d e r e d on t h e west by Q u a r t z i t e Range F o r m a t i o n i n f a u l t c o n t a c t , and on t h e e a s t by t h e O r e b i n Creek f a u l t . Upper H a m i l l a l s o forms t h e c o r e o f t h e P l a i d Lake s y n c l i n e . Q u a r t z i t e and s c h i s t w h i c h o v e r l y t h e Q u a r t z i t e Range F o r m a t i o n i m m e d i a t e l y e a s t o f t h e P r e a c h e r Creek f a u l t may a l s o be Upper H a m i l l Group. I n t h e l o w e r p a r t o f t h e P l a i d Lake s y n c l i n e s e c t i o n , l i t h o l o g i e s c o n s i s t o f s t r o n g l y deformed, t h i n i n t e r b e d d e d s c h i s t and impure q u a r t z i t e w i t h minor w h i t e q u a r t z i t e ( P l a t e 5 ) - The c o r e o f t h e s y n c l i n e and upper p a r t o f t h e s e c t i o n c o n t a i n s v a r i a b l e l i t h o l o g y w h i c h - 15 -includes a laminated grey limestone, 25 feet thick, c h l o r i t i c s c h i s t , minor brown laminated sandstone, quartzite, and calcareous s c h i s t . Washout Creek syncline s t r a t a do not appear to correlate with s t r a t a elsewhere i n the map-area and are interpreted to be Upper Hamill, which i s younger than rocks comprising the Pla i d Lake syncline. This youngest Upper Hamill i s bounded by f a u l t s and thus some of the Upper Hamill Group may be missing. C h l o r i t e - s c h i s t , found on the west side of the Orebin Creek f a u l t and adjacent to the Quartzite Ridge f a u l t , i s the oldest s t r a t a i n the Washout Creek syncline. Younger l i t h o l o g y consists of mainly grey micaceous quartzite and schi s t with minor micaceous marble. Pure white quartzite i s noteably subordinate. Upper Hamill Group overlies Quartzite Range Formation i n apparent conformity i n the Pl a i d Lake syncline. Upwards, the Upper Hamill i s i n f a u l t contact with the Mohican Formation along the Preacher Creek f a u l t . Upper Hamill Group i s highly deformed i n t e r n a l l y . Minor structures are abundant and l o c a l r e p e t i t i o n may be common. 4. MOHICAN FORMATION Mohican Formation, named by Fyles and Eastwood, (1962), is.present on both limbs of the Crawford Bay synform. On the eastern limb i t underlies - 16 -t h e Badshot F o r m a t i o n and i s i n f a u l t c o n t a c t w i t h Upper H a m i l l Group t o t h e e a s t a l o n g t h e P r e a c h e r Creek f a u l t . E x t e n s i v e d e f o r m a t i o n by i m b r i c a t e f a u l t i n g and i s o c l i n a l f o l d i n g w h i c h may i n v o l v e Badshot F o r m a t i o n i s s u s p e c t e d i n t h i s a r e a . The upper p a r t o f t h e Mohican F o r m a t i o n i s exposed on t h e west s i d e o f R i o n d e l p e n i n s u l a where i t i s p a r t o f t h e i n v e r t e d l i m b o f t h e C r a w f o r d Bay synform. The base o f t h e Mohican F o r m a t i o n i n t h e map-area i s d e f i n e d by brown w e a t h e r i n g t r e m o l i t i c m a r b l e w h i c h forms t h e west boundary o f t h e P r e a c h e r Creek f a u l t . I n t h e l o w e r p a r t o f t h e f o r m a t i o n , b e s t exposed i n C r a w f o r d Creek, l i t h o l o g i e s c o n s i s t o f i n t e r b e d d e d w h i t e q u a r t z i t e , s c h i s t , g r a n i t i c and c a l c -s i l i c a t e g n e i s s w i t h m a s s i v e l i m y and d o l o m i t i c m a r ble up t o f i f t y f e e t t h i c k . L o c a l l y , g r e y w e a t h e r i n g marble resembles Badshot F o r m a t i o n . Some o f t h e s e a r e i s o l a t e d o u t c r o p s where d e t a i l s o f s t r a t i g r a p h y a r e : unknown and may be i n f o l d s o f Badshot. I n t h e upper p a r t o f t h e f o r m a t i o n , s t r a t a a r e m a i n l y i n t e r b e d d e d g r e y g a r n e t - s c h i s t and q u a r t z o s e s c h i s t , w h i t e f l a g g y - b e d d e d q u a r t z i t e w i t h s c h i s t p a r t i n g s , and m i n o r marble. P r e a c h e r Creek f a u l t o u t l i n e s t h e base o f t h e Mohican F o r m a t i o n i n t h e map-area. Badshot F o r m a t i o n p r o b a b l y c o n f o r m a b l y o v e r l i e s Mohican on t h e R i o n d e l p e n i n s u l a . On t h e e a s t e r n l i m b o f t h e C r a w f o r d Bay - 17 -synform, however, t h e c o n t a c t may be a f a u l t w i t h m i n o r movement. Mohican F o r m a t i o n , i m m e d i a t e l y below t h e c o n t a c t , on t h e s l o p e west o f t h e j u n c t i o n o f C r a w f o r d and P r e a c h e r c r e e k s , forms a t i g h t i s o c l i n a l o v e r t u r n e d synform w i t h p o s s i b l e s h e a r i n g on t h e o v e r t u r n e d l i m b ( F i g u r e 7 ) . 5. BADSHOT FORMATION Walker and B a n c r o f t (1929) named t h e Badshot F o r m a t i o n from Mount Badshot i n t h e L a r d e a u map-area. The f o r m a t i o n forms a d i s t i n c t i v e g r e y band on t h e r i d g e - s i d e n o r t h o f C r a w f o r d Creek where i t i s p a r t o f t h e e a s t l i m b o f t h e C r a w f o r d Bay synform. I t i s l o c a l l y c a l l e d t h e B l u e b e l l l i m e s t o n e on t h e west l i m b where i t c r o p s out on R i o n d e l p e n i n s u l a . A l t h o u g h r a r e l y g r e a t e r t h a n a few hundred f e e t t h i c k , t h e Badshot i s a marker h o r i z o n i n t h e map-area and i s a b a s i s f o r c o r r e l a t i o n o u t s i d e t h e map-area. M a s s i v e and t h i n - b e d d e d members o f l i m y and d o l o m i t i c marble comprise t h e main p a r t o f t h e f o r m a t i o n . D o l o m i t i c m a r b le i s commonly l a m i n a t e d and i s u s u a l l y f i n e r - g r a i n e d and t h i n n e r - l a y e r e d t h a n t h e l i m y v a r i e t y . T r e m o l i t e and p h l o g o p i t e a r e common i n t h e Badshot on t h e e a s t l i m b o f t h e synform. Other l i t h o l o g i e s c o n s i s t o f l o c a l l e n t i c u l a r beds and b o u d i n s o f l e u c o - g r a n i t i c g n e i s s and, 20-25 f e e t o f g a r n e t -- 18 -s c h i s t and micaceous q u a r t z i t e . A p e l i t i c member o f comparable t h i c k n e s s i s not d e s c r i b e d i n the Badshot F o r m a t i o n e l s e w h e r e . S t r a t i g r a p h i c d e t a i l o f t h e p e l i t i c member does n o t s u p p o r t i n t e r p r e t a t i o n as an i n f o l d . Thus, e i t h e r i t i s h i t h e r t o u n r e c o g n i z e d Badshot l i t h o l o g y , o f p r o b a b l e l o c a l e x t e n t , o r i t i s a f a u l t s l i c e o f Mohican F o r m a t i o n and Badshot F o r m a t i o n i s r e p e a t e d i n t h e r i d g e - s i d e s e c t i o n . The base o f t h e Badshot F o r m a t i o n i s n o t exposed on t h e e a s t l i m b o f t h e Crax-zford Bay synform and on t h e Cr a w f o r d r i d g e s e c t i o n t h e c o n t a c t w i t h t h e u n d e r l y i n g Mohican F o r m a t i o n may be a l o c a l f a u l t as d e s c r i b e d above. On t h e west l i m b , on t h e s o u t h t i p o f R i o n d e l p e n i n s u l a , t h e c o n t a c t appears c o n f o r m a b l e a l t h o u g h c o n t a c t r e l a t i o n s a r e o b s c u r r e d by m a s s i v e p y r r h o t i t e m i n e r a l i z a t i o n . C o n t a c t w i t h t h e La r d e a u Group i s n o t exposed i n t h e map-area. However F y l e s ( p e r s o n a l communication) r e p o r t s L a r d e a u Group carbonaceous s t r a t a i n t h e mine s e c t i o n a t t h e B l u e b e l l M i ne, R i o n d e l , w h i c h s t r a t i g r a p h i c a l l y o v e r l i e s Badshot and i s s i m i l a r t o t h e Duncan Lake a r e a ( F y l e s , 1964). On t h e b a s i s o f c o r r e l a t i o n , t h e c o n t a c t between Badshot F o r m a t i o n and younger L a r d e a u Group i s p r o b a b l y c o n f o r m a b l e . 6. LARDEAU GROUP LARDEAU A Lar d e a u A c r o p s out i n two bands i n t h e - 19 -C r a w f o r d Bay synform. I t s t r u c t u r a l l y u n d e r l i e s t h e Badshot F o r m a t i o n a t R i o n d e l P e n i n s u l a on t h e west l i m b . On t h e e a s t l i m b , i t forms much o f t h e r i d g e e a s t o f Kootenay Lake. Outcrop o f L a r d e a u A i s n o t abundant. I n g e n e r a l , L a r d e a u A i s composed o f c a l c -s i l i c a t e g n e i s s , g r a n i t i c g n e i s s , s c h i s t , and minor m a r b l e . M a s s i v e g r e y q u a r t z i t e w h i c h o u t c r o p s on t h e r i d g e west o f t h e s o u t h p a r t o f P r e a c h e r Creek may be a l o c a l f a c i e s i n t h e map-area. S i m i l a r q u a r t z i t e does n o t o u t c r o p on t h e west l i m b o f t h e synform. L a r d e a u A o v e r l i e s t h e Badshot F o r m a t i o n w i t h p r o b a b l e c o n f o r m i t y . Upwards L a r d e a u A i s o v e r l a i n by L a r d e a u B. P r e s e n c e o f c a l c - s i l i c a t e g n e i s s and marble i n L a r d e a u A and i t s absence i n L a r d e a u B d e f i n e s t h e c o n t a c t . The c o n t a c t may be g r a d a t i o n a l and i s h i g h l y f a c i e s dependent. LARDEAU B Lard e a u B forms t h e c o r e o f t h e C r a w f o r d Bay synform and i s t h e youngest s t r a t i g r a p h i c u n i t i n t h e map-area. Grey s c h i s t and g r a n i t i c g n e i s s i s t h e main l i t h o l o g y . Impure q u a r t z i t e i s minor. Outcrop i s n o t abundant and b e s t exposures a r e seen i n r o a d - c u t s . 7. AMPHIBOLITE S i l l - l i k e b o d i e s and minor dykes o f - 20 -a m p h i b o l i t e a r e abundant i n the west p a r t o f the map-a r e a where t h e y a r e p r e s e n t i n the L a r d e a u Group and Mohican F o r m a t i o n . I n t h i n - s e c t i o n , the a m p h i b o l i t e i s a mosaic o f h o r n b l e n d e , p l a g i o c l a s e and s u b o r d i n a t e c h l o r i t e , c i n o z o i s i t e , and g a r n e t . P e n e t r a t i v e l i n e a t i o n o f h o r n b l e n d e , and i n t e n s e boudinage r e l a t e d t o phase one d e f o r m a t i o n , s u g g e s t s the a m p h i b o l i t e i s pre-metamorphic. C o n t a c t s w i t h the h o s t s t r a t a a r e s h a r p . S i l l - l i k e b o d i e s a r e l o c a l l y a n a s t i m o s i n g ; t h i c k n e s s i s v a r i a b l e up t o t w e n t y f e e t w i t h common p i n c h i n g and s w e l l i n g due t o boudinage ( P l a t e 2 ) . PLATE 2. A m p h i b o l i t e s i l l - l i k e body; deformed by phase one boudinage; i n L a r d e a u B; a x i a l zone o f C r a w f o r d Bay synform; v i e w e d n o r t h . - 21 -c- AGE AND CORRELATION R o c k - u n i t n o m e n c l a t u r e i n t h i s t h e s i s i s as u sed i n e a r l i e r s t u d i e s i n s i m i l a r s t r a t a n o r t h and s o u t h o f t h e map-area. The a u t h o r ' s e x p e r i e n c e w i t h t h e s e s t r a t a i s l i m i t e d and heavy r e l i a n c e on s t r a t i g r a p h i c d e s c r i p t i o n i n t h e l i t e r a t u r e was n e c e s s a r y . C o r r e l a t i o n o f r o c k - u n i t s o u t s i d e t h e map-a r e a i s made on l i t h o l o g i c b a s i s o n l y . No f o s s i l s were found i n t h e map-area and i n d e e d , s i m i l a r s t r a t a e l s e w h e r e y i e l d f o s s i l s o n l y l o c a l l y . Age o f s t r a t a i n t h e map-area i s d e t e r m i n e d by l i t h o l o g i c c o r r e l a t i o n w i t h s uch s t r a t a . T a b l e 2 summarizes t h e r e g i o n a l c o r r e l a t i o n o f s e d i m e n t a r y r o c k s . Where c o r r e l a t i o n i s thought t o r e q u i r e e x p l a n a t i o n , i t i s d i s c u s s e d below. Three S i s t e r s F o r m a t i o n i s r e c o g n i z e d i n t h e map-area because o f i t s d i s t i n c t i v e l i t h o l o g y and t h i c k n e s s . I t i s b e l i e v e d t o c o n f o r m a b l y o v e r l y t h e H o r s e t h i e f Creek Group. However, R i c e (1941, p. 19) does n o t s e p a r a t e s t r a t a e q u i v a l e n t t o t h e Three S i s t e r s F o r m a t i o n i n t h e N e l s o n e a s t - h a l f map-area because..."as t h e Three S i s t e r s beds a r e t r a c e d n o r t h e a s t e r l y from t h e Salmo a r e a t h e y l o s e t h o s e f e a t u r e s t h a t d i s t i n g u i s h them from t h e H o r s e t h i e f Creek beds and i n f a c t , seem t o merge a l o n g t h e s t r i k e i n t o normal - 22 -TABLE 2 LITHOLOGIC CORRELATION OP SEDIMENTARY ROCKS SALMO AREA CRAWFORD BAY LARDEAU AREA AREA Emerald F o r m a t i o n L a r d e a u B Lardeau A Index F o r m a t i o n * Reeves Member Badshot F o r m a t i o n Badshot F o r m a t i o n Truman Member Mohican F o r m a t i o n Mohican F o r m a t i o n Reno F o r m a t i o n \ Upper H a m i l l Group Upper H a m i l l Group -? Marsh-Adams F o r m a t i o n Q u a r t z i t e Range F o r m a t i o n Q u a r t z i t e Range F o r m a t i o n Mount G a i n e r F o r m a t i o n Three S i s t e r s F o r m a t i o n Three S i s t e r s F o r m a t i o n / H o r s e t h i e f Creek Group Monk F o r m a t i o n H o r s e t h i e f Creek Group R e f e r e n c e s : Salmo a r e a : F y l e s (1964), L i t t l e (I960). L a r d e a u a r e a : F y l e s (1964), Walker and B a n c r o f t (1929). Dashed l i n e i n d i c a t e s b r e a k i n s u c c e s s i o n . * A r c h i o c y a t h i d s o f p r o b a b l e l a t e Lower Cambrian age a r e found I n the Reeves Member. - 23 -H o r s e t h i e f Creek s t r a t a " . B u t , R i c e o m i t s d e s c r i p t i o n o f Three S i s t e r s type s t r a t a , w h i c h a r e r e c o g n i z e d by t h e a u t h o r and Walker (1928, p. 125) c l o s e t o t h e same a r e a o f h i s d e t a i l e d measured s e c t i o n s o f H a m i l l ( R i c e , 1941, p. 20) and H o r s e t h i e f Creek (p. 19). Three S i s t e r s F o r m a t i o n appears t o be a u s e f u l r o c k - u n i t i n t h e map-area. Northward i t s u t i l i t y may d i m i n i s h . C o r r e l a t i o n o f Upper H a m i l l Group w i t h s t r a t i g r a p h y o u t s i d e the map-area i s d i f f i c u l t a l t h o u g h t h e o v e r l y i n g Mohican F o r m a t i o n and u n d e r l y i n g Q u a r t z i t e Range F o r m a t i o n resemble e q u i v a l e n t s t r a t a i n t h e Salmo and Lardea u map-areas. D i f f i c u l t y a r i s e s because l i t h o l o g y p r e s e n t i n the Upper H a m i l l l i s n o t p r e s e n t by d e f i n i t i o n i n s t r a t a b e l i e v e d t o be e q u i v a l e n t o u t s i d e the map-area. C o n s i d e r a b l e t h i c k e n i n g o f s t r a t a n o r t h from the Salmo a r e a i s ap p a r e n t . I n t h e Salmo a r e a , Mathews (1953) and more r e c e n t l y , F y l e s and H e w l e t t (1959)* r e c o g n i z e the Reno F o r m a t i o n between t h e top o f t h e Q u a r t z i t e Range F o r m a t i o n and t h e f i r s t c a l c a r e o u s bed ( l i m e s t o n e , l o c a l l y 60 f e e t t h i c k ) . B o t h s t u d i e s i n d i c a t e an apparent t h i c k n e s s i n t h e o r d e r 600 f e e t , r a n g i n g from 300 t o 1000 f e e t . T h i s c o r r e l a t e s w e l l w i t h the l o w e r p a r t o f the Upper H a m i l l i n the P l a i d Lake s y n c l i n e . L a i b F o r m a t i o n , w h i c h o v e r l i e s the Reno, - 24 -i s correlated with Badshot and Mohican Formations by Fyles (1964, p. 35). However, limestone i n the Upper Hamill i s d i f f e r e n t from the carbonate beds i n the Mohican and Badshot Formations. Also an estimated apparent thickness of Upper Hamill i s f i v e to s i x times the apparent thickness of the Reno Formation. North of the map-area, i n the Ferguson area, Fyles and Eastwood (1962) describe the Marsh-Adams Formation, apparent thickness 1500-2000 feet, which i s bound by the Mohican Formation above and Quartzite Range Formation equivalent below. Fyles (1964) i n the Duncan Lake area describes l o c a l brown weathering lenses of buff limestone i n the Marsh-Adams Formation which may be equivalent to the carbonate i n the Upper Hamill. However, Fyles (1964), and Fyles and Eastwood (1962) do not describe a possible equivalent to the d i s t i n c t i v e c h l o r i t e s c h i s t which occurs i n the Upper Hamill. Possible equivalents are mapped by Wheeler (1963, and 1965) as greenstone i n the Hamill Group of the Big Bend and Rogers Pass map-areas over 100 miles north. Thus, s t r a t a of the Upper Hamill Group do not p r e c i s e l y correlate with formations to the north and south as they are defined. Except f o r d e t a i l s of minor l i t h o l o g y , Upper Hamill appears to best correlate with Marsh-Adams Formation. There i s an - 25 -a p p a r e n t c o r r e l a t i o n between t h e l o w e r p a r t o f t h e Upper H a m i l l and Reno F o r m a t i o n i n t h e Salmo a r e a . More d e t a i l e d s t u d y i n t h e map-area and a more p r e c i s e d e f i n i t i o n o f f o r m a t i o n s i n t h e H a m i l l Group n o r t h o f the map-area i s r e q u i r e d f o r f a s t i d i o u s c o r r e l a t i o n . Badshot F o r m a t i o n i s the o n l y r o c k - u n i t w h i c h i s d a t e d b y c o r r e l a t i o n w i t h f o s s i l i f e r o u s s t r a t a e l s e w h e r e . A r c h e o c y a t h i d s a r e p r e s e n t i n th e Badshot i n t h e Rogers Pass a r e a (Wheeler, 196j5), and i n t h e l i t h o l o g i c a l l y s i m i l a r Reeves Member o f the L a i b F o r m a t i o n ( L i t t l e , i 9 6 0 , F y l e s and H e w l e t t , 1959). Based on f o s s i l i d e n t i f i c a t i o n by V. J . O k u l i t c h , L i t t l e s t a t e s t h a t t h e l o w e r p a r t o f the L a i b F o r m a t i o n i s p r o b a b l y l a t e Lower Cambrian. Lard e a u s t r a t a were o r i g i n a l l y d e s c r i b e d by W a l k e r and B a n c r o f t , (1929, p. 11) and named the Lar d e a u S e r i e s a f t e r the La r d e a u map-area. F y l e s and Eastwood (1962), i n the F e r g u s o n a r e a , d e f i n e d s e v e r a l f o r m a t i o n s i n the Lardea u Group. The a u t h o r r e c o g n i z e s two r o c k - u n i t s i n t h e map-area w h i c h a r e s i m i l a r t o t h e Index F o r m a t i o n as d e s c r i b e d b y F y l e s and Eastwood. C o r r e l a t i o n o f La r d e a u s t r a t a w i t h t h e Salmo a r e a i s d i f f i c u l t (see F y l e s , 1964). O u t s i d e t h e map-area, on t h e e a s t s i d e o f Kootenay Lake, t h e M i l f o r d Group o f M i s s i s s i p p i a n age ( F y l e s and Eastwood, 1962) o v e r l i e s t h e Lardea u - 26 -Group i n possible disconformity. Lardeau Group i s thus post-late Lower Cambrian and pre-Mississippian age. - 27 -CHAPTER THREE STRUCTURE A. GENERAL STATEMENT Po l y p h a s e d e f o r m a t i o n o f v a r i a b l e i n t e n s i t y i s p r e s e n t on a l l s c a l e s . D u r i n g l i t h o l o g i c mapping, t h e mesoscopic s t r u c t u r a l f a b r i c o f o u t c r o p s was measured and, i n s e l e c t a r e a s , d e t a i l e d s t r u c t u r a l a n a l y s i s was made. S e v e r a l phases o f d e f o r m a t i o n a r e r e c o g n i z e d i n t h e map-area by the p r e s e n c e o f r e l a t e d m i n or s t r u c t u r e s , and f o r phase one, t h e p r e s e n c e o f major f o l d s . B o t h p l a n a r and a x i a l s t r u c t u r e s were measured. The e a r l i e s t p l a n a r s t r u c t u r e i s c o m p o s i t i o n a l l a y e r i n g w h i c h v a r i e s i n t h i c k n e s s from a few m i l l i m e t r e s t o a metre o r more. Gross l a y e r i n g i s commonly d e v e l o p e d by l a y e r s o f c o n t r a s t i n g l i t h o l o g y and i s c o n s i d e r e d t o be p r i m a r y l a y e r i n g o r b e d d i n g . A second f o l i a t i o n i s p a r a l l e l t o the a x i a l s u r f a c e s o f e a r l i e s t f o l d s . A x i a l s t r u c t u r e s c o n s i s t o f minor f o l d s , k i n k s , m i n e r a l l i n e a t i o n , boudinage and b e d d i n g / a x i a l s u r f a c e i n t e r s e c t i o n s . Three phases o f f o l d i n g a r e i n f e r r e d on the b a s i s o f minor s t r u c t u r e s o f d i f f e r e n t geometry and s t y l e , and d e f o r m a t i o n o f e a r l i e r f o l d s and l i n e a t i o n s by younger s t r u c t u r e s . M i n o r s t r u c t u r e s c o n s i s t o f minor f o l d s - 28 -( P l a t e 3 ) w h i c h a r e r e l a t e d t o phase one and phase two f o l d i n g , and phase t h r e e k i n k s ( P l a t e 1 2 ) . K i n k s and phase one minor f o l d s a r e u b i q u i t o u s . Phase two minor f o l d s a r e n o t w e l l developed. M i n o r f o l d s and k i n k s a r e r a r e l y l a r g e r than a few tens o f f e e t i n w a v e l e n g t h and commonly o n l y a few i n c h e s . S t r o n g l y p e n e t r a t i v e m i n e r a l l i n e a t i o n i s PLATE 3 . Phase one m i n o r f o l d s , Mohican F o r m a t i o n , R i o n d e l p e n i n s u l a , viewed n o r t h ; compass i s 2 - 3 / 4 1 ' i n c h e s wide. de v e l o p e d by e l o n g a t e o r i e n t a t i o n o f amphibole, m i c a , and q u a r t z g r a i n s , i n w h i c h the d i r e c t i o n o f e l o n g a t i o n i s p a r a l l e l t o a d j a c e n t minor f o l d - 29 -axes and b o u d i n s , r e l a t e d to phase one d e f o r m a t i o n . Boudins a r e common i n h i g h grade metamorphites, n o t e a b l y i n t h e Craw f o r d Bay synform. Boudins up to s e v e r a l f e e t i n d i a m e t e r a r e developed i n a m p h i b o l i t e , c a l c - s i l i c a t e g n e i s s and q u a r t z i t e s t r a t a . Long axes o f b o u d i n s appear t o be p a r a l l e l t o phase one f o l d axes. Subsequent d e f o r m a t i o n l o c a l l y caused r o t a t i o n o f b o u d i n s ( P l a t e 4) and sheared c o n t a c t s around some a m p h i b o l i t e b o u d i n s . Three major synforms a r e o u t l i n e d by g r o s s s t r a t i g r a p h i c r e l a t i o n s . A l l a r e phase one s t r u c t u r e s and each i s f u r t h e r d e s c r i b e d below and d e l i n e a t e d on f i g u r e 2 ( i n p o c k e t ) . PLATE 4 . R o t a t e d b o u d i n o f c a l c - s i l i c a t e g n e i s s , L a r d e a u A, west l i m b o f Crawford Bay synform; o u t c r o p viewed n o r t h ; hammer i s 15 i n c h e s . - 30 -Three major faults are indicated by stratigraphic relations. These faults are about parallel to the main structural trend and appear, in gross aspects, to be pre™culmination of the main metamorphism i n the area. Movement on these faults may be complex, with possible components of movement during phase one and phase two deformation. Other faults are minor and only of local extent. B. PHASE ONE Phase one folds are the earliest tectonic event recognized and delineate the main structural trend i n the map-area. Three major folds, outlined by stratigraphic mapping, the Plaid Lake"syncline, the Washout Creek syncline, and the Crawford Bay synform, are believed to be phase one structures. Each i s described below. Phase one structures are cylindroidal, i s o c l i n a l , similar folds. Related fold axes and axial structures plunge gently to the north, except where l o c a l l y deformed by subsequent structures. Plaid Lake syncline, i n the eastern part of the map-area, i s the lowest phase one structure recognized. I t i s i s o c l i n a l i n the core zone and sligh t l y overturned to the west. The east limb consists of Horsethief Creek Group, Three Sisters - 31 -F o r m a t i o n , and Q u a r t z i t e Range F o r m a t i o n . Sedimentary s t r u c t u r e s i n the two l a t t e r f o r m a t i o n s i n d i c a t e an u p r i g h t s u c c e s s i o n . Upper H a m i l l Group forms the c o r e and west l i m b o f t h e s y n c l i n e t o where the O r e b i n Creek f a u l t d e l i n e a t e s i t s w e s t e r n e x t e n t . M i n o r f o l d s i n the s y n c l i n e a r e s i m i l a r , commonly i s o c l i n a l , and a s s y m e t r i c w i t h g e n t l y n o r t h p l u n g i n g f o l d axes. These f o l d s a r e b e l i e v e d t o be phase one s t r u c t u r e s because o f s i m i l a r geometry and s t y l e t o e a r l i e s t f o l d s i n the C r a w f o r d Bay snyform w h i c h a r e r e c o g n i z e d t o be deformed by subsequent f o l d s ( d e s c r i b e d b e l o w ) . F i g u r e 3 i s a s t e r e o g r a m a n a l y s i s o f p o l e s t o b e d d i n g and c l e a v a g e , phase one minor f o l d a xes, m i n e r a l l i n e a t i o n , and c l e a v a g e - b e d d i n g i n t e r s e c t i o n s i n t h e P l a i d Lake s y n c l i n e . S t r u c t u r a l d a t a used i n t h i s t h e s i s i s p l o t t e d on t h e l o w e r hemisphere o f an e q u a l - a r e a s t e r e o n e t . Three S i s t e r s F o r m a t i o n d i s p l a y s c l o s e -s e t c l e a v a g e and abundant s e d i m e n t a r y s t r u c t u r e s . No m inor f o l d s were o b s e r v e d i n the f o r m a t i o n . The c l e a v a g e i s i n t e r p r e t e d t o be r e l a t e d t o t h e f o r m a t i o n o f the P l a i d Lake s y n c l i n e because o f approximate p a r a l l e l i s m o f c l e a v a g e - b e d d i n g i n t e r s e c t i o n s w i t h o t h e r a x i a l s t r u c t u r e s r e l a t e d t o the s y n c l i n e ( F i g u r e 3), and o f c l e a v a g e w i t h - 52 -F i g u r e 3. Stereogram, P l a i d Lake s y n c l i n e - 33 -PLATE 5. Phase one minor folds i n adjacent outcrops, Upper Hamill Group, east limb of Plaid Lake syncline near core zone; outcrops are viewed north; hammer i s 15 inches. axial planes of minor phase one folds i n the core zone of the syncline (Plate 5 ) . The average cleavage i s 013-80SE with a cleavage-bedding intersection of 0 2 0 / 0 5 ° . Three Sisters Formation has an average bedding, 024-45N¥. Quartzite i n Quartzite Range Formation and Upper Hamill Group i n the Plaid Lake syncline commonly display quartz rodding and elongate muscovite on the bedding planes. These linear structures are paral l e l to phase one minor fold axes i n the p e l i t i c member of the Quartzite Range _ 34 . F o r m a t i o n and i n the c o r e o f the s y n c l i n e , ( F i g u r e J>) • P l a t e 5 shows phase one minor f o l d s on the e a s t l i m b o f the s y n c l i n e n e a r the c o r e zone i n Upper H a m i l l Group s t r a t a . The ir f o l d a x i s o f the s y n c l i n e i s 0 1 5 / 1 0 ° . Much o f the n o r t h - s o u t h d i s p e r s i o n of; p o l e s t o b e d d i n g from t h e mean TT g i r d l e and d i s p e r s i o n o f m i n e r a l l i n e a t i o n and minor f o l d a x e s , i s caused by younger d e f o r m a t i o n d e s c r i b e d below. P l a i d Lake s y n c l i n e i s b e l i e v e d t o be homoaxial and c y l i n d r o i d a l w i t h l o c a l v a r i a t i o n i n f o l d a x i s due t o subsequent d e f o r m a t i o n . The Washout Creek s y n c l i n e i s bound by th e O r e b i n Creek f a u l t on the e a s t and the Q u a r t z i t e Ridge f a u l t on the west. As d e s c r i b e d p r e v i o u s l y , I n c h a p t e r two, S t r a t i g r a p h y , s t r a t a i n the Washout Creek s y n c l i n e cannot be c o r r e l a t e d w i t h o t h e r s t r a t a i n the map-area and a r e c o n s i d e r e d t o be Upper H a m i l l Group, younger than s t r a t a i n the P l a i d Lake s y n c l i n e , and o l d e r than s t r a t a west o f t h e P r e a c h e r Creek f a u l t . S t r a t a i n the f a u l t bound a r e a a r e b e l i e v e d t o comprise a s y n c l i n e . The o p p o s i n g a p p a r e n t sense o f vergence o f minor f o l d s ( P l a t e 6) on o p p o s i t e l i m b s suggest a s y n f o r m a l s t r u c t u r e . The second l i n e o f e v i d e n c e i s s t r a t i g r a p h i c , b ased on c o r r e l a t i o n o f h o r n b l e n d e - c h l o r i t e s c h i s t - 35 -and marble, and to a l e s s e r extent, q u a r t z i t e and s c h i s t , from the east limb to the west limb. S t r a t a i n the core of the f o l d are considered younger than the c h l o r i t e s c h i s t u n i t which occurs at the f a u l t boundaries, and thus the f o l d i s b e l i e v e d to be a s y n c l i n e . The b a s i s of age d i s t i n c t i o n i s c o r r e l a t i o n of the c h l o r i t e s c h i s t u n i t w i t h a greenstone member i n the Hamill Group no r t h of the map-area (described above). This evidence i s not c o n c l u s i v e and more d e t a i l e d mapping may be r e q u i r e d . PLATE 6. Phase one minor f o l d s , Upper Hamil l Group, west limb of Washout Creek s y n c l i n e ; outcrop viewed north; p e n c i l Is f i v e inches. Minor f o l d s are not abundant and no sedimentary s t r u c t u r e s were observed i n the - 36 -Washout Creek s y n c l i n e . Where p r e s e n t , m i n o r f o l d s a r e s i m i l a r , i s o c l i n a l w i t h a x i a l s u r f a c e s almost p a r a l l e l t o the c o m p o s i t i o n a l l a y e r i n g . These f o l d s a r e c o n s i d e r e d t o be phase one s t r u c t u r e s by a n a l o g y w i t h comparable minor f o l d s i n the Cr a w f o r d Bay synform. Because o f the l a c k o f s t r u c t u r a l d a t a , due t o p o o r o u t c r o p , a n a l y s i s o f the Washout Creek s y n c l i n e i s based p r i n c i p a l l y on phase one minor s t r u c t u r e s . P o l e s t o b e d d i n g and minor f o l d axes measured i n the s y n c l i n e a r e shown i n stereogram f i g u r e 4. The ir f o l d a x i s and phase one minor f o l d axes a r e a p p r o x i m a t e l y c o a x i a l , about 0 1 6 / 1 0 ° , and t h e r e f o r e , the Washout Creek s y n c l i n e i s b e l i e v e d t o be a phase one s t r u c t u r e . A t h i g h e l e v a t i o n s , as i n the above a n a l y s i s , the s y n c l i n e i s o v e r t u r n e d t o the west. However, e q u i v a l e n t Upper H a m i l l s t r a t a , on s t r i k e i n the C r a w f o r d Creek v a l l e y , d i p u n i f o r m l y t o the n o r t h w e s t . The a x i a l s u r f a c e may be c u r v e d and t h u s , o v e r t u r n e d to the e a s t a t low e l e v a t i o n s ( F i g u r e 5). S t r u c t u r a l and s t r a t i g r a p h i c r e l a t i o n s i n the Washout Creek s y n c l i n e a r e not w e l l known i n t h e p r e s e n t s t u d y and f u r t h e r i n v e s t i g a t i o n i s suggested. The h i g h e s t and b e s t documented o f the major s t r u c t u r e s , i s the C r a w f o r d Bay synform. F i g u r e 4 . Stereogram, Washout Creek s y n c l i n e . - 39 -A l t h o u g h g r o s s s t r a t i g r a p h i c r e l a t i o n s and i n t e r n a l s t r u c t u r a l f e a t u r e s ( o u t l i n e d below) i n d i c a t e the major s t r u c t u r e i s a s y n c l i n e , the term synform i s a p p l i e d t o a l l o w p o s s i b l e i n t e r p r e t a t i o n o f p r e s e n t s t r a t i g r a p h i c r e l a t i o n s by f a u l t i n g . The n a t u r e o f f a u l t i n g i n t h e map-area i s d i s c u s s e d below. U s i n g i n f o r m a t i o n w i t h i n the bounds o f the map-area, the f o l d i n t e r p r e t a t i o n i s f a v o u r e d . T h i s s t r u c t u r e w i l l be d i s c u s s e d i n two p a r t s , f i r s t i n t e r n a l s t r u c t u r a l and s t r a t i g r a p h i c r e l a t i o n s o f map-a r e a e x t e n t and second, r e g i o n a l r e l a t i o n s w i t h s t r u c t u r e s more e v i d e n t o u t s i d e the map-area. The l a t t e r p a r t i s d e s c r i b e d w i t h phase two d e f o r m a t i o n below. Geometry and s t y l e o f the synform i s o u t l i n e d by g r o s s s t r a t i g r a p h y and by abundant a s s o c i a t e d minor s t r u c t u r e s ( P l a t e 7 and 8 ) . The e a s t e r n boundary o f the C r a w f o r d Bay synform i n the map-area i s the P r e a c h e r Creek f a u l t . M ohican F o r m a t i o n , Badshot F o r m a t i o n and L a r d e a u Group ar e r e c o g n i z e d on b o t h l i m b s . The synform i s o v e r t u r n e d t o the west and p l u n g e s n o r t h w a r d about 1 0 - 1 5 ° w i t h l o c a l v a r i a t i o n . M i n o r f o l d s a r e u b i q u i t o u s . I s o c l i n a l " s i m i l a r " minor f o l d s w i t h a x i a l p l a n e s s u b p a r a l l e l t o g r o s s l i t h o l o g i c l a y e r i n g a r e c o n s i d e r e d phase one s t r u c t u r e s based on - 40 -PLATE 8 . Phase one synform, Mohican Formation, Riondel peninsula; viewed north. - 41 -d e f o r m a t i o n by younger s t r u c t u r e s d e s c r i b e d below. F i g u r e 6 i s a stereogram o f p o l e s t o b e d d i n g , phase one minor f o l d a x e s , and m i n e r a l l i n e a t i o n measured i n t h e Badshot and Mohican F o r m a t i o n s on t h e u p r i g h t e a s t l i m b o f the s y n c l i n e i n the v i c i n i t y n o r t h w e s t o f the j u n c t i o n o f P r e a c h e r and Cr a w f o r d Creek. F i g u r e 7 i s a d e t a i l e d a n a l y s i s o f a l o c a l o v e r t u r n e d s y n c l i n e i n the same a r e a w i t h i n t h e Mohican F o r m a t i o n n e a r the c o n t a c t w i t h the Badshot F o r m a t i o n . The 7r f o l d a x e s , minor f o l d axes and m i n e r a l l i n e a t i o n s a r e c o a x i a l , 000 / 1 0 ° , and d i s p l a y the same geometry as the major synform. On t h i s b a s i s t h e synform i s c o n s i d e r e d a phase one s t r u c t u r e . S i m i l a r stereograms a r e i n c l u d e d f o r o t h e r p a r t s o f the major f o l d . F i g u r e 3 d e s c r i b e s the s t r u c t u r e i n Lardea u A a t h i g h e l e v a t i o n s on the e a s t l i m b o f the synform on the r i d g e west o f P r e a c h e r Creek. S t r a t a a t h i g h e r e l e v a t i o n s d i p 60-65° west compared w i t h e q u i v a l e n t s t r a t a a l o n g s t r i k e t o the s o u t h a t low e l e v a t i o n s , w h i c h d i p 30-40° west. The f o l d a x i s i n t h i s area, i s the same as i n the Badshot and Mohican F o r m a t i o n s t o the e a s t ( F i g u r e s 6 and 7 ) . On the o v e r t u r n e d l i m b west o f Craw f o r d Bay a t low e l e v a t i o n , t h e d i p o f the s t r a t a i s l e s s , about 20-30° west. M i n e r a l l i n e a t i o n i s v a r i a b l e i n a t t i t u d e w i t h an average p l u n g e o f - 42 -.N F i g u r e 6. Stereogram, Badshot F o r m a t i o n and Mohican F o r m a t i o n , e a s t l i m b o f C r a w f o r d Bay synform. N w s F i g u r e 7- Stereogram, Mohican F o r m a t i o n , o v e r t u r n e d s y n c l i n e below Mohican-Badshot c o n t a c t , e a s t l i m b o f C r a w f o r d Bay synform. - 43 -N S Stereogram, L a r d e a u A, h i g h e l e v a t i o n s on r i d g e west o f P r e a c h e r Creek, e a s t l i m b o f C r a w f o r d Bay synform. N E S Stereogram, L a r d e a u Group, o v e r t u r n e d west l i m b o f C r a w f o r d Bay synform, a r e a west d f C r a w f o r d Bay. - 4 4 -10-20° towards n o r t h e r l y d i r e c t i o n s ( F i g u r e 9 ) -C o n s i d e r a b l e l o c a l f o l d i n g by l a t e r phase t h r e e k i n k s causes the d i s p e r s i o n o f p o l e s t o b e d d i n g and m i n e r a l l i n e a t i o n s i n the o v e r t u r n e d l i m b as i n f i g u r e 9 > T h i s a s p e c t i s d i s c u s s e d below. C. PHASE TWO Phase two f o l d s a r e p r e s e n t i n the map-area as minor f o l d s w h i c h a r e r e c o g n i z e d and d i s t i n g u i s h e d from phase one minor f o l d s on the b a s i s o f geometry and c o r r e l a t i o n w i t h minor f o l d s e t s d e s c r i b e d o u t s i d e the map-area by F y l e s ( 1 9 6 4 ) . I n the map-area phase two f o l d s a r e s i m i l a r , a s s y m e t r i c , o v e r t u r n e d t o u p r i g h t . Seven a x i a l p l a n e measurements, m o s t l y i n c a l c -s i l i c a t e and marble beds o f t h e Mohican F o r m a t i o n have an average o r i e n t a t i o n 145-60SW ( F i g u r e 10). The west l i m b o f a n t i f o r m s d i p m o d e r a t e l y t o t h e west and the e a s t l i m b i s v a r i a b l e , from moderate e a s t - d i p p i n g t o o v e r t u r n e d and s t e e p l y w e s t - d i p p i n g . ( P l a t e s 9 and 10). Phase two f o l d axes p l u n g e m o d e r a t e l y t o t h e west and n o r t h w e s t . A l t h o u g h phase one and phase two minor f o l d s have d i f f e r e n t geometry, c o n c l u s i v e age r e l a t i o n s o f the two f o l d s e t s was n o t determined i n t h e map-area. M i n e r a l l i n e a t i o n r e l a t e d t o F i g u r e 10. Stereogram, phase two a x i a l p l a n e s and f o l d a x e s , C r a w f o r d Bay synform, e a s t l i m b . - 46 -PLATE 9 . Phase two minor f o l d s (upper l e f t ) and phase one minor f o l d s ( l o w e r r i g h t ) , Mohican F o r m a t i o n , e a s t l i m b o f C r a w f o r d Bay synform; C r a w f o r d Creek, viewed n o r t h w e s t ; a x i a l t r a c e o f phase two f o l d s i s s u b - p a r a l l e l t o hammer handle and o f phase one f o l d s , t o g r o s s l i t h o l o g i c l a y e r i n g . PLATE 10. Phase two minor f o l d s and r e l a t e d c l e a v a g e and boudinage, Mohican F o r m a t i o n , C r a w f o r d Creek; viewed n o r t h ; p e n c i l i s 4.5 i n c h e s . - 47 -phase one f o l d s was n o t o b s e r v e d on l i m b s o f phase two minor f o l d s . However, phase two f o l d s a r e n o t abundant i n t h e map-area and a r e u s u a l l y p r e s e n t i n l e s s competent beds. They a r e commonly o u t l i n e d by t h i n i n t e r c o l a t e d c a l c - s i l i c a t e beds i n m a r b l e w h i c h a r e l o c a l l y s h e a r e d w i t h i n t h e e n c l o s i n g m a r b le ( P l a t e 10). Phase two a x i a l p l a n e s l o c a l l y a r e f a u l t s and remnants o f shea r e d l i m b s form a crude c l e a v a g e and boudinage i n the ma r b l e . I n such beds, phase one m i n e r a l l i n e a t i o n i s a b s e n t , presumably o b l i t e r e d by phase two d e f o r m a t i o n . D ecollement o r b e d d i n g p l a n e s l i p p a g e may a l s o a ccount f o r some l a c k o f i n t e r a c t i o n between phase one and two minor f o l d s . Age r e l a t i o n s o f t h i s f o l d s e t i s i n t e r p r e t e d by c o r r e l a t i o n w i t h a f o l d s e t o f the same geometry o u t s i d e the map-area. F y l e s , i n t he Duncan Lake map-area d e s c r i b e s two phases o f f o l d i n g on t h e b a s i s o f s t r a t i g r a p h i c mapping and the p r e s e n c e o f r e l a t e d minor f o l d s ( F y l e s , 1964, p. 4 l ) . The two phases d e s c r i b e d by F y l e s have s i m i l a r geometry and s t y l e as those o f the f o l d s e t i n the map-area. F y l e s , : P l a t e XVI shows i s o c l i n a l f o l d s deformed b y a "phase two" a n t i f o r m . On the b a s i s o f c o r r e l a t i o n , phase two i s younger than phase one. - 48 -Phase two m i nor f o l d s were o n l y r e c o g n i z e d i n the L a r d e a u A and Mohican F o r m a t i o n on the e a s t l i m b o f the C r a w f o r d Bay synform. The e f f e c t o f phase two d e f o r m a t i o n on the west l i m b i s l e s s e v i d e n t . Phase one m i nor f o l d s i n t h e west l i m b a r e commonly s t r o n g l y a t t e n u a t e d and l o c a l l y f o l d f a u l t s a r e p r e s e n t ( P l a t e 11). The a t t e n u a t i o n i s b e l i e v e d t o be caused by shear i n the a x i a l zones o f phase one f o l d s r e s u l t i n g from phase two f o l d i n g . I n t h e C r a w f o r d Bay synform, phase one a x i a l p l a n e s o f minor f o l d s a r e almost p a r a l l e l t o g r o s s c o m p o s i t i o n a l l a y e r i n g and, as d e s c r i b e d above, s t r a t a i n t h e e a s t l i m b a t h i g h e l e v a t i o n s have s t e e p e r west d i p s t h a n e q u i v a l e n t s t r a t a a t low e l e v a t i o n s . I f t h e a x i a l s u r f a c e o f the major synform i s a l s o p a r a l l e l t o g r o s s s t r a t i g r a p h y as i s i n d i c a t e d by mapping, th e n t h e phase one a x i a l s u r f a c e i s c u r v e d , and i s t h e r e f o r e , f o l d e d . Thus, some event appears t o p o s t - d a t e phase one d e f o r m a t i o n and deforms the s t r a t a on a major s c a l e . A p l a u s i b l e s u g g e s t i o n i s phase two d e f o r m a t i o n , i n w h i c h case the C r a w f o r d Bay synform i s a l i m b on a m a jor phase two s t r u c t u r e . - 49 -PLATE 11. Phase one synform, L a r d e a u A, west l i m b o f Cra w f o r d Bay synform; viewed n o r t h ; p e n c i l i s 4 i n c h e s . D. PHASE THREE Phase t h r e e d e f o r m a t i o n i s c o n f i n e d t o m i nor s t r u c t u r e s i n the map-area and c o n s i s t s o f w i d e s p r e a d development o f k i n k s . Wavelength o f the k i n k s i s r a r e l y g r e a t e r than a few tens o f f e e t and u s u a l l y much l e s s . The i n t e n s i t y o f phase t h r e e d e f o r m a t i o n i n c r e a s e s toward t h e w e s t e r n p a r t o f the map-area. I n g e n e r a l , k i n k s have round h i n g e zones i n a n t i f o r m s and a n g u l a r h i n g e zones i n synforms - 50 -w i t h q u a r t z v e i n s l o c a l l y c o n c e n t r a t e d i n the l a t t e r ( P l a t e 12). Phase one minor s t r u c t u r e s a r e deformed by k i n k s ( P l a t e s 14 and 15). L a r g e k i n k s a r e b e s t d e v e l o p e d and a r e abundant i n o u t c r o p a l o n g Kootenay Lake. F o l d axes o f the k i n k s a r e dependent on t h e o r i e n t a t i o n o f the b e d d i n g a t the time o f f o r m a t i o n o f the k i n k . Thus, v a r i a t i o n i n k i n k f o l d axes e x i s t s due t o a n i s o t r o p y caused by e a r l i e r d e f o r m a t i o n . I n g e n e r a l , a x i a l p l a n e s o f l a r g e k i n k s i n t h e west p a r t o f the map-area t r e n d southwest and a r e s u b v e r t i c a l t o s t e e p l y s o u t h e a s t d i p p i n g , and r e l a t e d f o l d axes p l u n g e m o d e r a t e l y t o t h e southwest. I n d i v i d u a l k i n k s a r e o n l y l o c a l i n e x t e n t and the amount o f d e f o r m a t i o n v a r i e s a l o n g the a x i a l p l a n e . K i n k s a r e s i n u s o i d a l a l o n g t h e i r axes. I n the l a r g e r k i n k s , d e t a i l e d a n a l y s i s o f t h e d e f o r m a t i o n o f phase one l i n e a t i o n i s p o s s i b l e . F i g u r e s 11, 12 and 13 a r e stereograms o f such a n a l y s i s on the a n t i f o r m s o f l a r g e i n d i v i d u a l k i n k s i n d i f f e r e n t p a r t s o f the map-area. The deformed phase one l i n e a t i o n c o n s i s t s o f q u a r t z r o d d i n g and m i n e r a l e l o n g a t i o n shown above t o be c o a x i a l w i t h phase one m i nor f o l d axes. The a n g l e between each k i n k f o l d a x i s and the phase one - 51 -PLATE 12. Phase three kink, Mohican Formation, Riondel peninsula; round antiformal hinge, angular synformal hinge (bottom center l e f t ) , viewed northwest. - 52 -PLATE 13. Phase one minor synform, Mohican Formation, Riondel peninsula; viewed north; close-up of fold deformed by phase three i n Plate 14 below. PLATE 14. Phase one synform deformed by phase three kink; viewed northwest, area of Plate 13 i s outlined; pencil i s 5 inches. - 55 -PLATE 1 5 . Phase three kink, Mohican Formation; phase one lineation i s deformed; Riondel peninsula, viewed east. PLATE 1 6 . Phase three kink, quartzite i n Lardeau A; 5 0 0 0 feet elevation, north of Crawford Bay; viewed northwest, hammer Is 15 inches. - 54 -l i n e a t i o n i s " b e l i e v e d t o be c o n s t a n t such t h a t the l i n e a t i o n i s deformed on a s m a l l c i r c l e l o c u s about the k i n k f o l d a x i s . Thus, f o l d i n g o f the b e d d i n g by phase t h r e e k i n k s i s c o n s i d e r e d t o be f l e x u r a l - s l i p . An e x a c t s m a l l c i r c l e l o c u s about t h e rr f o l d a x i s o f the k i n k i s drawn on each stereogram ( F i g u r e s 1 1 , 12 and 1 3 ) . Phase two minor s t r u c t u r e s were n o t o b s e r v e d t o have been deformed by phase t h r e e k i n k s . Age r e l a t i o n i s b ased on d i f f e r i n g t y p e s o f d e f o r m a t i o n and by c o r r e l a t i o n o u t s i d e the map-area. Phase two f o l d s a r e " s i m i l a r " and phase t h r e e k i n k f o l d s a r e f l e x u r a l - s l i p , b e l i e v e d t o be younger because t h e y a r e b r i t t l e s t r u c t u r e s and o b s e r v e d t o deform o t h e r " s i m i l a r " f o l d s r e l a t e d t o phase one d e f o r m a t i o n . Ross ( i n p r e s s ) i n the R e v e l s t o k e a r e a t o the n o r t h , d e s c r i b e s young f l e x u r a l - s l i p f o l d s superposed on s i m i l a r f o l d s i n an a r e a o f p o l y p h a s e f o l d i n g o f s t r a t a w h i c h c o r r e l a t e w i t h map-area s t r a t a . Thus, n u m e r a t i o n o f phases used i n the t h e s i s i s b e l i e v e d t o be i n o r d e r o f age. - 55 -mineral l i n e a t i o n pole to bedding TT g i r d l e \ * V T T r, kink f o l d - 56 -N v 3 59° .* mineral l i n e a t i o n N J ^ • pole to bedding ^ \ •\ -TTV kink f o l d F3 E Figure 12. Stereogram, phase three kink f o l d Mohican Formation, east limb of Crawford Bay synform. Figure 13. Stereogram, phase three kink f o l d , Mohican Formation, east limb of Crawford Bay synform. - 5 7 -E. FAULTS Three major f a u l t s a r e r e c o g n i z e d i n the map-area. T h e i r l o c a t i o n i s shown i n f i g u r e 2 ( i n p o c k e t ) and t h e y a r e the O r e b i n Creek f a u l t , t h e Q u a r t z i t e R i dge f a u l t , and the P r e a c h e r Creek f a u l t . The O r e b i n Creek f a u l t forms the boundary between the P l a i d Lake s y n c l i n e and the Washout Creek s y n c l i n e . I t i s a shear zone i n c h l o r i t e s c h i s t and s e p a r a t e s younger s t r a t a o f t h e Upper H a m i l l Group i n t h e Washout Creek s y n c l i n e from o l d e r Upper H a m i l l Group s t r a t a i n the P l a i d Lake s y n c l i n e t o the west. The o r i e n t a t i o n o f t h e f a u l t s u r f a c e o r zone i s unknown, b u t s h e a r i n g i n the s c h i s t o s e s t r a t a i s p a r a l l e l t o s u b v e r t i c a l b e d d i n g de v e l o p e d by q u a r t z i t e . The Q u a r t z i t e R i dge f a u l t i s o u t l i n e d by the w e s t e r n o u t c r o p o f the Q u a r t z i t e Range F o r m a t i o n and d e f i n e s t h e w e s t e r n e x t e n t o f Upper H a m i l l Group i n Washout Creek s y n c l i n e . E x i s t e n c e o f t h e f a u l t i s I n t e r p r e t e d on s t r a t i g r a p h i c b a s i s where Q u a r t z i t e Range F o r m a t i o n s t r u c t u r a l l y o v e r l i e s younger Upper H a m i l l s t r a t a . The f a u l t i s b e l i e v e d t o be p a r a l l e l t o the s t r u c t u r a l base o f t h e Q u a r t z i t e Range s t r a t a w h i c h d i p 6 0 - 7 5 ° t o t h e west ( F i g u r e 5 ) . - 58 -D i s t i n c t i v e m a s s i v e brown w e a t h e r i n g d o l o m i t i c m a r b le i n the Mohican F o r m a t i o n has an o u t c r o p p a t t e r n w h i c h converges w i t h the Q u a r t z i t e Range F o r m a t i o n i n the v i c i n i t y o f t h e j u n c t i o n o f P r e a c h e r and C r a w f o r d Creeks. Much o f the Upper H a m i l l s t r a t a i s n o t r e c o g n i z e d between t h e marble and t h e Q u a r t z i t e Range F o r m a t i o n . On the b a s i s o f absence o f s t r a t a and c o n v e r g i n g c o n t a c t s o f c o n t r a s t i n g l i t h o l o g y , the P r e a c h e r Creek F a u l t i s s u g g e sted a t t h e base o f t h e marble. Dip o f s t r a t a i n t h i s v i c i n i t y i n c r e a s e s l o c a l l y t o g r e a t e r t h a n 80° west. The P r e a c h e r Creek f a u l t and the Q u a r t z i t e Ridge f a u l t converge a t low e l e v a t i o n i n t h e C r a w f o r d Creek v a l l e y and a t depth may be t h e same f a u l t . P r e c i s e age o f the major f a u l t s i s n o t d e t e r m i n e d a l t h o u g h c e r t a i n l i m i t s a r e e v i d e n t . S e v e r a l f e a t u r e s a r e common t o t h e s e major f a u l t s . B edding i n the v i c i n i t y o f the f a u l t tends t o be p a r a l l e l t o the f a u l t p l a n e and major f a u l t s a r e p a r a l l e l t o the main s t r u c t u r a l t r e n d s o u t l i n e d by the major phase one f o l d s . Thus, i n g r o s s a s p e c t s , the geometry o f the major f o l d s and f a u l t s appears t o be t h e same. No major a n t i c l i n e s a r e r e c o g n i z e d i n t h e map-area and the major f a u l t s s e p a r a t e a r e a s o f s y n c l i n a l f o l d s . I t appears t h a t the f a u l t s a r e r e l a t e d to phase one - 59 -f o l d s and i t i s i n f e r r e d t h a t movement was i n i t i a t e d d u r i n g the f o r m a t i o n o f these phase one f o l d s . M a j o r f a u l t s do n o t appear t o d i s t u r b the metamorphic i s o g r a d s and a r e , t h e r e f o r e , c o n s i d e r e d pre-metamorphic. P a r t o f t h e r e g i o n a l rnetamorphism ( d e s c r i b e d below) i s a l s o c o n s i d e r e d t e m p o r a l w i t h phase two d e f o r m a t i o n . Thus some movement on p r e - e x i s t i n g f a u l t p l a n e s o r development o f new f a u l t s may have o c c u r r e d d u r i n g phase two d e f o r m a t i o n p r e v i o u s t o the c u l m i n a t i o n o f r e g i o n a l rnetamorphism. No d i s t i n c t i o n between f a u l t s r e l a t e d t o phase one d e f o r m a t i o n from th o s e r e l a t e d t o phase two can be made. S e v e r a l phases o f movement may e x i s t f o r some o f t h e f a u l t s . P r e s e n t s t r a t i g r a p h i c r e l a t i o n s i n d i c a t e r e s u l t a n t n e t movement on the Q u a r t z i t e R i d g e f a u l t i s r e v e r s e and i s normal on the O r e b i n Creen f a u l t and P r e a c h e r Creek f a u l t . O ther s i m i l a r f a u l t s may e x i s t i n the map-area b u t a r e n o t i n d i c a t e d by g r o s s s t r a t i g r a p h i c r e l a t i o n s . - 60 -CHAPTER POUR METAMORPHISM Metamorphism accompanied much o f t h e d e f o r m a t i o n i n the map-area. Gross a s p e c t s o f t h e metamorphism a r e d e s c r i b e d and some problems a r e mentioned i n t h i s s t u d y . F i e l d o b s e r v a t i o n o f metamorphic e f f e c t s was supplemented by e x a m i n a t i o n o f t w e n t y t h i n - s e c t i o n s and d e t e r m i n a t i o n o f Mg/Mg + Fe i n s i x c o e x i s t i n g g a r n e t - b i o t i t e p a i r s . A metamorphic g r a d i e n t i s . r e c o g n i z e d by the o r d e r o f appearance o f metamorphic zones, and b y the i n c r e a s i n g d i s t r i b u t i o n c o e f f i c i e n t o f Mg and Fe i n g a r n e t - b i o t i t e p a i r s . M i n e r a l assemblages, d e t e r m i n e d i n t h i n - s e c t i o n , a r e i n c l u d e d i n Table 3 i n g e n e r a l sequence o f i n c r e a s i n g metamorphic grade. Some o f t h e s e a r e d i s c u s s e d below. The g e n e r a l t r e n d o f metamorphic i s o g r a d s appears t o be p a r a l l e l t o major phase one s t r u c t u r e s w i t h i n c r e a s i n g grade from e a s t t o west. D i p o f the i s o g r a d s i s u n c e r t a i n . Metamorphic zones, w h i c h a r e r e c o g n i z e d i n g r o s s a s p e c t s b u t n o t d e l i n e a t e d i n t h i s s t u d y , i n c l u d e c h l o r i t e , b i o t i t e , g a r n e t , d i o p s i d e , and s i l l i m a n i t e . C h l o r i t e and b i o t i t e zones a r e p r e s e n t i n the e a s t e r n p a r t o f t h e map-area and i n c l u d e most s t r a t a o l d e r t h a n Mohican F o r m a t i o n . The most e a s t e r l y o c c u r r e n c e o f b i o t i t e i s i n t h e c o r e o f t h e P l a i d Lake - 61 -TABLE 3 Metamorphic mineral assemblages i n Crawford Bay map-area Mineral assemblage Formation or division Location qu-fs-mu Horsethief Creek SW of Mt. Crawford. qu-mu Three Sisters 1 mile east of Mt. Crawford. qu-mu-ch-sn Quartzite Range SE Mt. Crawford, elevation 7 2 0 0 feet. qu-ch-mu-bi Upper Hamill -lower part NE of Mt. Crawford, elev. 6400 feet, core of Plaid Lake Syncline. ch-qu-mu-bi-pl Upper Hamill -upper part east of Quartzite Ridge fault, west of Plaid Lake, elev. 5500 feet. bi-qu-ac-pl Mohican Crawford Creek, NE of "bridge. qu-mu-bi-pl-or ga-cz-(ch) Mohican qu-mu-bi-ga Mohican ridge-side NE of Crawford Creek, east limb of Crawford Bay synform. ca-tm Badshot ca-ph-qu-pl-tm-(ch) Badshot qu-pl-bi-ca-di-ac-cz-myrmekite Lardeau A Indian Creek, near Riondel, west limb of Crawford Bay Synform. qu-or-pl-ac-au cz-myrmekite Lardeau A qu-or-pl-bi Lardeau B road-cut, south part of map-area, core of Crawford Bay synform. qu-or-bi-mu-pl -myrmekite Lardeau B road-cut, south part of map-area, west limb Crawford Bay synform. - 62 -T a b l e 3 c o n t i n u e d . M i n e r a l F o r m a t i o n o r L o c a t i o n assemblage d i v i s i o n qu- • o r - p l - b i L a r d e a u B r o a d - c u t , s o u t h p a r t o f map-area, c o r e o f C r a w f o r d Bay synform. qu- • o r - b i - m u - p l - L a r d e a u -myrmekite B r o a d - c u t , s o u t h p a r t o f map-area, west l i m b o f C r a w f o r d Bay synform. qu- • o r - d i - c a - b i - p l L a r d e a u •cz- (ch) A l a k e s h o r e , Kootenay Lake. qu- •mu-bi-ga-si-(ch)Mohican n o r t h p a r t o f R i o n d e l p e n i n s u l a . M i n e r a l a b b r e v i a t i o n s ac a c t i n o l i t e mu m u s c o v i t e au a u g i t e o r o r t h o c l a s e b i b i o t i t e ph p h l o g o p i t e c a c a c i t e and d o l o m i t e p i p l a g i o c l a s e c h c h l o r i t e qu q u a r t z cz c l i n o z o i s i t e s i s i l l i m a n i t e f s f e l d s p a r sn s t i l p n o m e l a n e ga g a r n e t tm t r e m o l i t e (ch) i n d i c a t e s c h l o r i t e i s i n t e r s p e r s e d i n m i c a and b e l i e v e d t o be r e t r o g r a d e metamorphic. - 63 -s y n c l i n e . On the e a s t l i m b o f the Cr a w f o r d Bay synform, t r e m o l i t e , a c t i n o l i t e , and g a r n e t a r e p r e s e n t i n Mohican F o r m a t i o n , and t r e m o l i t e i n Badshot F o r m a t i o n . These m i n e r a l s have n ot been r e c o g n i z e d t o the e a s t . Crosby (i960) c o n s i d e r s most o f the synform west o f t h e Badshot F o r m a t i o n t o be w i t h i n the s i l l i m a n i t e zone. D i o p s i d e and one o c c u r r a n c e o f s i l l i m a n i t e was n o t e d i n t h e s e r o c k s . Metamorphism i s s y n k i n e m a t i c w i t h phase one d e f o r m a t i o n . S t r o n g l y p e n e t r a t i v e m i n e r a l l i n e a t i o n o f m i c a , amphibole and q u a r t z i s common and u s u a l l y p a r a l l e l t o phase one s t r u c t u r e s . However, h i g h e r grade metamorphic m i n e r a l s such as t r e m o l i t e , l o c a l l y d i o p s i d e -a c t i n o l i t e , and s i l l i m a n i t e a r e n o t l i n e a t e d as one may expe c t i f metamorphism was e n t i r e l y s y n k i n e m a t i c ( P l a t e 17). The c u l m i n a t i o n o f metamorphism may not be s y n k i n e m a t i c . I n the Duncan Lake a r e a F y l e s (1964) r e c o g n i z e s a p e n e t r a t i v e m i n e r a l l i n e a t i o n r e l a t e d t o phase two d e f o r m a t i o n w h i c h suggests metamorphism i s s y n k i n e m a t i c w i t h t h i s d e f o r m a t i o n . However because phase two i s s u b o r d i n a t e i n the map-area, few r e l a t e d s y n k i n e m a t i c metamorphic e f f e c t s a r e p r e s e n t . Phase t h r e e d e f o r m a t i o n i s post-metamorphic. M i c a i s b e n t and bro k e n by phase t h r e e k i n k s . Phase t h r e e k i n k f o l d s deform phase one m i n e r a l l i n e a t i o n by f l e x u r a l - s l i p f o l d i n g and d i s p l a y r e l a t e d q u a r t z v e i n i n g i n a n g u l a r h i n g e zones. Thus , c u l m i n a t i o n o f the metamorphism i s - 64 -believed to be post-phase one and pre-phase three deformation. Retrograde formation of chlorite i s present i n high grade rocks. This may be attributed to younger intrusive rocks or to metamorphic effects during phase three deformation. Chloritization may have occurred during both events. Chlorite selvages along contacts between amphibolite and granitic dykes are common. PLATE 1 7 . Tremolite porphyroblasts i n marble, Mohican Formation, near east side of Crawford Bay; pencil i s 6 inches. D i f f i c u l t y i s encountered when one attempts to define a mineral isograd i n the map-area. - 65 -Metamorphism appears t o p r o g r e s s i v e l y i n c r e a s e t o t h e west i n a d i r e c t i o n p e r p e n d i c u l a r t o t h e main s t r u c t u r a l and s t r a t i g r a p h i c t r e n d . Thus o b s e r v e d m i n e r a l o g i c a l changes may be caused n o t o n l y by change i n metamorphic grade b u t a l s o b y f a c i e s changes a c r o s s t h e s t r i k e . S i l l i m a n i t e a l s o p r e s e n t s a problem because i t may form by s e v e r a l metamorphic r e a c t i o n s and s e v e r a l s i l l i m a n i t e i s o g r a d s may e x i s t each w i t h s l i g h t l y d i f f e r e n t t e m p e r a t u r e and p r e s s u r e environment. U n f o r t u n a t e l y most p e l i t e s i n t h e " s i l l i m a n i t e " zone c o n t a i n o r t h o c l a s e and do n o t have b u l k c o m p o s i t i o n s s u i t a b l e f o r the f o r m a t i o n o f s i l l i m a n i t e o f the f i r s t i s o g r a d type. One t h i n s e c t i o n o f p e l i t i c s c h i s t from R i o n d e l p e n i n s u l a c o n t a i n s s i l l i m a n i t e i n a f i n e -g r a i n e d m u s c o v i t e a g g r e g a t e . T y p i c a l m i n e r a l assemblages i n t h e " s i l l i m a n i t e zone" are; shown i n f i g u r e 14. As n o t e d above, h i g h grade p e l i t e s i n the C r a w f o r d Bay synform do n o t c o n t a i n b u l k c o m p o s i t i o n s w h i c h a r e s u i t a b l e f o r t h e f o r m a t i o n o f A l o S i 0 c d D polymorphs w h i c h may i n d i c a t e grade more p r e c i s e l y . Grade d i f f e r e n c e between t h e e a s t and west l i m b o f t h e synform i s i n d i c a t e d by d i s t r i b u t i o n c o e f f i c i e n t s , K D = ( M g / F e ) g a r n e t / ( M g / F e ) M o t . t e , o f Mg and Fe i n c o e x i s t i n g g a r n e t - b i o t i t e p a i r s i n p e l i t i c s c h i s t . S i x p a i r s were a n a l i z e d from g a r n e t i f e r o u s p e l i t i c s c h i s t i n the upper p a r t o f t h e Mohican F o r m a t i o n , f o u r ( h i g h - 66 -sillimanite 0 0.5 1.0 sillimanite A A' muscovite K orthoclase Figure 14. Mineral assemblages recognized i n high grade p e l i t i c schist and calc-s i l i c a t e gneiss, Crawford Bay synform. - 6 7 -sample numbers) from R i o n d e l p e n i n s u l a and two (low sample numbers) from the r i d g e n o r t h o f Cr a w f o r d Bay. Garnet c o m p o s i t i o n was dete r m i n e d by r e f r a c t i v e i n d e x u s i n g a J e l l y - L e i t z r e f r a c t o m e t e r and by c e l l edge u s i n g X - r a y d i f f r a c t i o n methods (CuK ) w i t h q u a r t z o ( d 1 0 1 = 3.J543A) as an i n t e r n a l s t a n d a r d . Garnet d a t a i s summarized i n t a b l e 4 and shown on f i g u r e 15-Mg/Mg + Fe r a t i o s a r e determined by p r o j e c t i o n o f g a r n e t p l o t s i n f i g u r e 15 t o t h e almandine-pyrope j o i n . The minor c o n s t i t u e n t o f t h e g a r n e t s i s assumed t o be m a i n l y e i t h e r g r o s s u l a r i t e o r a n d r a d l t e w i t h c o n s t a n t s p e s s a r t i n e c o n t e n t and two s e t s o f r a t i o s a r e det e r m i n e d by p r o j e c t i o n t h rough e i t h e r g r o s s u l a r i t e o r a n d r a d l t e t o t h e almandine-pyrope j o i n ( T a b l e 6 ) . I n b i o t i t e , Mg/Mg + Fe r a t i o s , were determined by m e a s u r i n g d Q g 0 by X- r a y d i f f r a c t i o n (CuK a) w i t h s i l i c o n (29 = 5 6 . 1 7 4 ° ) as i n t e r n a l s t a n d a r d . Wones (1963) d e t e r m i n e d r e g r e s s i o n e q u a t i o n s f o r ^ Q^Q w i t h c h a n g i n g Mg/Mg + Fe r a t i o o f b i o t i t e s on the j o i n p h l o g o p i t e - a n n i t e w h i c h were"... s y n t h e s i z e d and "ann e a l e d " under g i v e n c o n d i t i o n s o f p r e s s u r e , t e m p e r a t u r e , and oxygen f u g a c i t y " . R a t i o s f o r two l i m i t i n g b u f f e r systems used by Wones, F e-|__ x 0 - ^e^Pi+> and Fe^O^ - Fe^O^, were det e r m i n e d and a r e summarized i n t a b l e 5-D i s t r i b u t i o n c o e f f i c i e n t s f o r b o t h g a r n e t p r o j e c t i o n s and b o t h b i o t i t e b u f f e r systems a r e shown - 68 -4 R e f r a c t i v e i n d i c e s and c e l l edge d e t e r m i n a t i o n s o f g a r n e t , Mohican F o r m a t i o n . 28 d a Q R.I. 3 1 . 0 2 2 . 8 8 3 1 1 . 5 3 ( 1 ) 1 .8o4 + .004 3 4 . 7 7 2 . 5 8 0 1 1 . 5 3 ( 8 . 3 0 . 7 9 2 . 9 0 4 1 1 . 6 1 ( 7 ) 1 . 8 0 1 + .004 3 4 . 5 7 2 . 5 9 4 1 1 . 6 0 ( 3 ) 3 0 . 9 4 2 . 8 9 0 1 1 . 5 6 ( 1 ) 1.786 + .004 3 4 . 6 9 2.584 1 1 . 5 5 ( 5 ) 3 1.00 2 . 8 8 5 1 1 . 5 4 ( 1 ) 1 .786 + .004 3 4 . 7 5 2 . 5 8 2 1 1 . 5 4 ( 6 3 0 . 9 5 2 . 8 9 0 1 1 . 5 5 ( 8 ) 1 .785 + .004 3 4 . 7 0 2 . 5 8 3 1 1 . 5 5 ( 3 ) 30.97 2.887 1 1 . 5 5 ( 0 ) 1.785 + .004 3 4 . 7 2 2.582 1 1.54(7 - 69 -TABLE 5 D e t e r m i n a t i o n o f Mg/Mg + Pe i n b i o t i t e , Mohican F o r m a t i o n Sample 29 d o 6 o Mg/Mg + Fe (1) FegO^ - Pe^O^ (2) FeO - Pe^O^ b u f f e r b u f f e r 21 59-899 1.5444 .45 .59 13 60.024 1.5413 .63 .72 269-1 59.994 1.5420 .59 .69 269-2 59.999 1.5418 .60 .70 291 59.999 1.5418 .60 .70 343 59-924 1.5436 .50 .62 ( l ) r e g r e s s i o n e q u a t i o n Fe^O^ ~ ^ e 3 ^ 4 b u f f 6 1 , d n6n = - - 5 3 4 8 + O . O I 7 6 Fe/Pe + Mg (Wones, 1963, p . 1307) (2) r e g r e s s i o n e q u a t i o n ^er-x® ~ ^ e3^4 b u f f e r .. 1306) d 060 = ! - 5 3 4 8 + 0.0234 Fe/Fe + Mg (Wones, 1965. - 70 -a n d r a d i t a pyrope 11.50 11.70 11.90 o C e l l edge A F i g u r e 15. C o m p o s i t i o n o f g a r n e t s i n p e l i t i c s c h i s t o f Mohican F o r m a t i o n i n the C r a w f o r d Bay synform. l o w e r metamorphic grade h i g h e r metamorphic grade - 7 1 -i n t a b l e 5 « Dodds ( 1 9 6 5 ) a n a l i z e d e i g h t g a r n e t s from s c h i s t s i n the c e n t r a l Kootenay Lake a r e a and found them t o be almandine-pyrope w i t h m a i n l y a n d r a d i t e m o l e c u l e as minor c o n s t i t u e n t . F o r t h i s r e a s o n , perhaps c o e f f i c i e n t s b a sed on g a r n e t p l o t s p r o j e c t e d t h r o u g h a n d r a d i t e s h o u l d be f a v o u r e d . However, because c o n s t i t u e n t s o t h e r t h a n Mg and Fe end members a r e s m a l l , d i f f e r e n c e s i n the g a r n e t s a r e l a r g e l y a f u n c t i o n o f Mg/Fe r a t i o . An e x c e p t i o n i s sample 1 3 ( c f . F i g u r e 1 5 ) w h i c h i s s i g n i f i c a n t l y removed from the almandine-pyrope j o i n . F o r t h i s r e a s o n , i t i s n o t c o n s i d e r e d when comparing d i s t r i b u t i o n c o e f f i c i e n t s from low t o h i g h grade. A s i g n i f i c a n t d i f f e r e n c e between g a r n e t -b i o t i t e p a i r s i n l o w grade r o c k s on the e a s t l i m b on the C r a w f o r d Bay synform and h i g h grade r o c k s on the west l i m b , i s shown by l a r g e r d i s t r i b u t i o n c o e f f i c i e n t s i n h i g h e r grade r o c k s ( T a b l e 5 * F i g u r e 1 6 , and 1 7 ) . T h i s f i n d i n g i s c o m p a t i b l e w i t h t h a t o f Al b e e ( 1 9 6 5 ) who showed i n c r e a s i n g c o e f f i c i e n t s w i t h i n c r e a s i n g grade. I n summary, i t i s found t h a t rnetamorphism, w i t h m i n or r e t r o g r a d e e f f e c t s , i n c r e a s e s from e a s t t o west a c r o s s t h e map-area i n a d i r e c t i o n n e a r l y normal t o t h e main s t r u c t u r a l and s t r a t i g r a p h i c t r e n d . W i t h i n a map d i s t a n c e o f seven m i l e s , rnetamorphism changes from c h l o r i t e zone t o - 72 -TABLE 6 D i s t r i b u t i o n c o e f f i c i e n t s o f Mg and Pe i n c o e x i s t i n g b i o t i t e and g a r n e t p a i r s , Mohican F o r m a t i o n . Sample [Mg/Mg + F e J g a r [Mg/Mg + F e ] M o K D 1 K D 2 1.* 2. 21 (1)1 .250 .205 .45 (2) .250 .205 .59 13 .432 .63 (2) .432 .72 291 i1} .477 • 330 .60 (2) .477 .330 .70 269-1 .466 .318 .59 (2) .466 .318 .69 269-2 .500 .341 .60 (2) .500 .341 .70 .466 • 330 • 50 2 .466 • 330 .62 .40(7) .31(5) .23! [2) •17(9) .441 .291 .601 .32(8] • 391 i i ) •21(1) .601 •32(4) • 391 !2) .21(0) .66( •34(5) .4l( !9) .22(2) .871 •49(3) • 53< 5 .30(2) 1* - r a t i o d e t e r m i n e d by p r o j e c t i o n from a n d r a d i t e t o almandine-pyrope j o i n i n f i g u r e 2* - r a t i o d e t e r m i n e d by p r o j e c t i o n from g r o s s u l a r i t e t o almandine-pyrope j o i n i n f i g u r e ( l ) * - r a t i o d e t e r m i n e d u s i n g r e g r e s s i o n e q u a t i o n f o r d,v~ f o r b u f f e r system Fe_0-, - Pe-,0., (Wones _PpQv j 2 3 3 4 1963)• 1 > (2)* - f o r b u f f e r system F e - ^ O - Fe^O^ (Wones, 1963) 1 - 75 -.7 0 .1 .2 .3 .4 .5 .6 .7 .8 Mg/Mg + Fe b i o t i t e • F i g u r e 16. Mg/Mg + Fe i n c o e x i s t i n g g a r n e t -b i o t i t e p a i r s , Mohican F o r m a t i o n , C r a w f o r d Bay synform. ( A n d r a d i t e ' c o n s i d e r e d t o be minor component .of g a r n e t ) . (1) - f o r b u f f e r system F e 20^ - Fe^O^ (Wones, 1963). (2) - f o r b u f f e r system F e - ^ O - Fe^O^ (Wones, 1963). - n -.5 0 .1 .2 • .3 .4 .5 .6 .7 .8 .9 Mg/Mg + Fe b i o t i t e F i g u r e 1J. Mg/Mg + Fe i n c o e x i s t i n g g a r n e t -b i o t i t e p a i r s , Mohican F o r m a t i o n , C r a w f o r d Bay synform. , ( G r o s s u l a r i t e c o n s i d e r e d t o be minor component o f g a r n e t ) . (1) - f o r b u f f e r system FegO^ - Fe^O^ (Wones, 1963). (2) - f o r b u f f e r system F e 1 _ x O - Fe^O (Wones, 1963). - 7 5 -s i l l i m a n i t e zone. M i n e r a l l i n e a t i o n r e l a t e d t o phase one d e f o r m a t i o n i s b e l i e v e d t o be caused b y s y n k i n e m a t i c rnetamorphism. These s t r u c t u r e s a r e deformed by phase t h r e e k i n k s . High grade metamorphic m i n e r a l s a r e p o s t - k i n e m a t i c and t h u s , c u l m i n a t i o n o f rnetamorphism i s p o s t - p h a s e one and pre-phase t h r e e d e f o r m a t i o n . Phase two d e f o r m a t i o n i s n o t w e l l d e v e l o p e d i n the map-area and s i g n i f i c a n t r e l a t e d metamorphic e f f e c t s were n o t obs e r v e d . Thus r e l a t i o n between i t and t h e peak o f rnetamorphism i s n o t determined. D i s t r i b u t i o n c o e f f i c i e n t s , K D = ( M g / F e ) g a r n e t / ( M g / F e ) M o t i t e , f o r c o - e x i s t i n g g a r n e t - b i o t i t e p a i r s , i n c r e a s e w i t h i n c r e a s i n g grade o f rnetamorphism i n t h e C r a w f o r d Bay synform. - 76 -CHAPTER FIVE INTRUSIVE ROCKS Most i n t r u s i v e r o c k s i n the map-area a r e post-metamorphic and younger than the main s t r u c t u r a l d e f o r m a t i o n . S m a l l g r a n i t i c s t o c k s , dykes and s i l l s o f g r a n i t e p e g m a t i t e , and b a s i c dykes a r e p r e s e n t i n t h e west p a r t o f t h e map-area. Some p e g m a t i t e may be a s s o c i a t e d w i t h t h e rnetamorphism. Metamorphic and s t r u c t u r a l e f f e c t s a s s o c i a t e d w i t h t h e s e i n t r u s i v e r o c k s does n o t appear t o be e x t e n s i v e . The m i n o r development o f r e t r o g r a d e c h l o r i t e i n the h i g h grade metamorphites may be r e l a t e d t o emplacement o f the i n t r u s i v e r o c k s . 1. GRANITIC STOCKS Two b o d i e s o f medium-grained w h i t e i n t r u s i v e r o c k l i e i n the southwest c o r n e r o f the map-area. Crosby (i960) c o n s i d e r s them t o be v a r i a b l e c o m p o s i t i o n r a n g i n g from q u a r t z monzonite t o g r a n o d i o r i t e . The s t o c k a d j a c e n t t o Kootenay Lake i s p r o b a b l y n o t l a r g e r t h a n a few hundreds o f f e e t i n di a m e t e r ; a t Cr a w f o r d Bay the s t o c k extends s e v e r a l m i l e s s o u t h o f the map-area and o n l y the n o r t h c o n t a c t was mapped. Medium t o f i n e g r a i n e d l e u c o c r a t i c g r a n i t i c - 77 -PLATE 1 8 . F i n e - g r a i n e d g r a n i t i c dyke i n t r u d i n g L a r d e a u A s t r a t a w h i c h i s deformed by phase t h r e e k i n k s ; l a k e s h o r e , Kootenay Lake; viewed n o r t h e a s t . PLATE 19- F i n e - g r a i n e d g r a n i t i c dyke i n t r u d i n g f o l i a t e d p e g m a t i t e s i l l i n Lard e a u A s t r a t a ; l a k e s h o r e , Kootenay Lake; viewed n o r t h . - 78 -dykes w i t h c h i l l e d m argins I n t r u d e L a r d e a u A s t r a t a exposed on the s h o r e l i n e o f Kootenay Lake i n t h e s o u t h p a r t o f map-area. These a r e p r o b a b l y r e l a t e d t o the s t o c k i n the v i c i n i t y . F i n e - g r a i n e d dykes c r o s s - c u t phase t h r e e s t r u c t u r e s ( P l a t e 18) and f o l i a t e d p e g m a t i t e s i l l s ( P l a t e 19). These r o c k s i n t r u d e s t r a t a o f v a r i a b l e l i t h o l o g y , w h i c h were p r e v i o u s l y metamorphosed. Metamorphic e f f e c t r e l a t e d t o i n t r u s i v e r o c k s was no t s t u d i e d i n t h i s t h e s i s ; however, j u d g i n g by f i e l d o b s e r v a t i o n , i t does n o t appear t o be e x t e n s i v e . 2. GRANITE PEGMATITE White p e g m a t i t e i s u b i q u i t o u s i n t h e west p a r t o f the map-area i n the C r a w f o r d Bay synform where i t forms s i l l s o r s i l l - l i k e i n t r u s i o n s up t o , a hundred f e e t t h i c k . More commonly p e g m a t i t e forms s i l l s and minor dykes a few f e e t t h i c k ( P l a t e 19). L a r d e a u Group s t r a t a c o n t a i n augens and t h i n s i l l - l i k e l e n t i c u l a r b o d i e s o f p e g m a t i t e r a r e l y g r e a t e r than a few i n c h e s i n l e n g t h ( P l a t e 20). B o t h f o l i a t e d and n o n - f o l i a t e d p e g m a t i t e i s r e c o g n i z e d and may be o f d i f f e r e n t ages. A l l p e g m a t i t e i s e s s e n t i a l l y composed o f f e l d s p a r , q u a r t z , m u s c o v i t e , minor b i o t i t e , and l o c a l l y , - 79 -subordinate tourmaline. F o l i a t e s tend to be sma l l e r , more l e n t i c u l a r and anastimosing, whereas the n o n - f o l i a t e d pegmatites are more t a b u l a r i n t h e i r aspect. Long axes of augens appear to p a r a l l e l phase one f o l d axes although measurement PLATE 2 0 . Augens of white pegmatite i n Lardeau B, a x i a l zone of Crawford Bay synform; road-cut exposure; viewed north. i s d i f f i c u l t and in a c c u r a t e . Contact r e l a t i o n s of f o l i a t e d pegmatite may be sharp or g r a d a t i o n a l w i t h the host rock. N o n - f o l i a t e s have sharp contacts and l o c a l l y c h i l l e d margins. D i f f e r e n c e i n age of pegmatite i s suggested by n o n - f o l i a t e pegmatite which i n t r u d e s the Kootenay Lake g r a n i t i c stock and probable a s s o c i a t e d dykes. - 80 -3 . BASIC DYKES Subvertical dark colored basic dykes are present along the shoreline of Kootenay Lake. These dykes are fine-grained with phenocrysts of inc l u s i o n - f i l l e d plagioclase and fine crystal aggregates of mafic minerals. Locally inclusions of the country rock are contained i n the dyke (Plate 21). PLATE 21. Basic dyke intruding Mohican Formation, Riondel peninsula; inclusion i s white pegmatite; hammer i s about 1 foot. These dykes may be the latest intrusive phase i n the map-area. They are not observed to - 8 1 -i n t r u d e t h e g r a n i t i c s t o c k s o r r e l a t e d dykes. However, they do c r o s s - c i a t u n f o l i a t e d p e g m a t i t e s i l l s . I n t r u s i v e r o c k s , u b i q u i t o u s i n the w e s t e r n p a r t o f the map-area, c o n s i s t o f s m a l l l e u c o c r a t i c g r a n i t i c s t o c k s and dykes, w h i t e p e g m a t i t e s i l l s and b a s i c dykes. Emplacement o f i n t r u s i v e r o c k s , except f o r some p e g m a t i t e w h i c h may be r e l a t e d t o rnetamorphism, i s subsequent t o rnetamorphism and d e f o r m a t i o n o f s t r a t a i n t h e Cr a w f o r d Bay a r e a . Metamorphism and d e f o r m a t i o n a s s o c i a t e d w i t h t h e i n t r u s i o n s i s minor. The g r a n i t i c b o d i e s a r e b e l i e v e d t o be s a t e l l i t i c i n t r u s i o n s a s s o c i a t e d w i t h the N e l s o n b a t h o l i t h nearby. K/Ar i s o t o p i c d a t i n g o f the n o r t h e r n p a r t o f N e l s o n b a t h o l i t h b y Nguyen e t . a l . ( i n p r e s s ) , i s about 160 m i l l i o n y e a r s ( M i d d l e J u r a s s i c ) . - 8 2 -CHAPTER SIX SUMMARY The C r a w f o r d Bay a r e a c o m p r i s e s a s m a l l p a r t o f t h e Kootenay A r c , on t h e e a s t s i d e o f Kootenay L a k e , s o u t h e a s t e r n B r i t i s h Columbia. I t i s u n d e r l a i n by metamorphosed and s t r o n g l y deformed s t r a t a , r a n g i n g i n age from l a t e P r o t e r o z o i c t o M i d d l e P a l e o z o i c , and a l s o by mi n o r i n t r u s i v e r o c k s . The s t r a t i g r a p h i c s u c c e s s i o n , d e t e r m i n e d u s i n g s e d i m e n t a r y s t r u c t u r e s i n t h e e a s t p a r t o f the map-area and l i t h o l o g i c c o r r e l a t i o n o u t s i d e t h e map-area i n t h e west p a r t , c o n s i s t s o f H o r s e t h i e f Creek Group, Lower H a m i l l Group, i n c l u d i n g Three S i s t e r s F o r m a t i o n , and Q u a r t z i t e Range F o r m a t i o n , Upper H a m i l l Group, Mohican F o r m a t i o n , Badshot F o r m a t i o n , and L a r d e a u Group, i n c l u d i n g L a r d e a u A and L a r d e a u B, a l l i n apparent c o n f o r m i t y . The o l d e s t r o c k - u n i t i s H o r s e t h i e f Creek Group, w h i c h o c c u r s i n the e a s t p a r t o f the map-area and s t r a t a , g e n e r a l l y , a r e younger towards t h e west. L i t h o l o g i e s a r e m a i n l y q u a r t z i t e , p e l i t e , and marble w i t h i n c r e a s i n g development o f s c h i s t and g n e i s s towards more h i g h l y metamorphosed a r e a s . Badshot F o r m a t i o n i s b e l i e v e d t o be l a t e Lower Cambrian age because o f - 83 -l i t h o l o g i c c o r r e l a t i o n w i t h Badshot F o r m a t i o n and Reeves Member w h i c h c o n t a i n A r c h e o c y a t h i d s . Thus most o f the s e c t i o n i s o l d e r t h a n l a t e Lower Cambrian and t h e l o w e r p a r t may be l a t e P r o t e r z o i c i n age. Upwards, Larde a u Group i s o v e r l a i n by s t r a t a o f M i s s i s s i p p i a n age on t h e e a s t s i d e o f Kootenay Lake. Three phases o f d e f o r m a t i o n a r e r e c o g n i z e d . The main s t r u c t u r a l t r e n d i s o u t l i n e d by t h r e e major phase one s t r u c t u r e s , t h e P l a i d Lake s y n c l i n e , the Washout Creek s y n c l i n e , and t h e C r a w f o r d Bay synform. These s t r u c t u r e s a r e i s o c l i n a l and o v e r t u r n e d w i t h f o l d axes p l u n g i n g g e n t l y t o the n o r t h e x c e p t where l o c a l l y deformed by subsequent s t r u c t u r e s . Abundant r e l a t e d m i n or s i m i l a r f o l d s and p e n e t r a t i v e m i n e r a l l i n e a t i o n a r e p r e s e n t . Phase two d e f o r m a t i o n c o n s i s t s o f m i n o r f o l d s w h i c h a r e o n l y l o c a l l y developed. These f o l d s a r e s i m i l a r , a s s y m e t r i c , u p r i g h t t o o v e r t u r n e d t o t h e west, w i t h moderate west and n o r t h w e s t p l u n g i n g f o l d axes. Phase t h r e e d e f o r m a t i o n i s e v i d e n c e d i n t h e u b i q u i t o u s development o f k i n k s w i t h i n c r e a s i n g i n t e n s i t y towards the w e s t e r n p a r t o f t h e map-area. The s t r a t a a r e k i n k e d i n t o open a n t i f o r m s and a n g u l a r synforms w i t h q u a r t z v e i n s i n t h e l a t t e r . Geometry o f the d e f o r m a t i o n o f phase one m i n e r a l l i n e a t i o n - 84 -on t h e a n t i f o r m s i n d i c a t e s f o l d i n g i s f l e x u r a l -s l i p . Numeration o f the phases i s i n o r d e r o f age based on d e f o r m a t i o n o f e a r l i e r s t r u c t u r e s by younger. Three major f a u l t s a r e i n d i c a t e d b ased on s t r a t i g r a p h i c mapping, O r e b i n Creek f a u l t , Q u a r t z i t e R i d g e f a u l t , and P r e a c h e r Creek f a u l t . These f a u l t s a r e p a r a l l e l t o the main s t r u c t u r a l t r e n d o u t l i n e d by major phase one s t r u c t u r e s and s e p a r a t e a r e a s o f s y n c l i n a l f o l d s . F o r m a t i o n o f t h e s e f a u l t s i s pre-metamorphic and b e l i e v e d t o be r e l a t e d t o phase one and e a r l y phase two d e f o r m a t i o n . Metamorphism i s r e c o g n i z e d w i t h i n c r e a s i n g grade from e a s t t o west from c h l o r i t e zone t o s i l l i m a n i t e zone. I t i s s y n k i n e m a t i c w i t h phase one d e f o r m a t i o n and pre-phase t h r e e i n age. C u l m i n a t i o n o f metamorphism i s p o s t -k i n e m a t i c . D i s t r i b u t i o n c o e f f i c i e n t s o f Mg and Fe i n c o - e x i s t i n g b i o t i t e and g a r n e t i n c r e a s e s w i t h i n c r e a s i n g grade o f metamorphism. S m a l l b o d i e s o f i n t r u s i v e r o c k s a r e common i n the w e s t e r n p a r t o f the map-area. Two l e u c o c r a t i c g r a n i t i c s t o c k s a r e p r e s e n t i n the s o u t h . Other i n t r u s i o n s comprise l e u c o c r a t i c g r a n i t i c dykes a s s o c i a t e d w i t h the Kootenay Lake s t o c k , w h i t e s i l l - l i k e b o d i e s and minor dykes o f g r a n i t e p e g m a t i t e , and b a s i c dykes. I n t r u s i o n o f - 85 -l e u c o c r a t l c g r a n i t i c r o c k s and b a s i c dykes i s subsequent t o rnetamorphism and d e f o r m a t i o n . Two ages o f p e g m a t i t e a r e p r e s e n t , syn-metamorphic and post-metamorphic. S t r u c t u r a l and metamorphic e f f e c t s o f t h e i n t r u s i v e r o c k s i s minor. I n t r u s i v e s t o c k s i n t h e map-area a r e c o n s i d e r e d t o be s a t e l l i t i c b o d i e s r e l a t e d t o th e N e l s o n B a t h o l i t h l o c a t e d 10 m i l e s t o the e a s t . A maximum K/Ar i s o t o p i c age d e t e r m i n a t i o n o f the N e l s o n i n t r u s i o n i s 171 m i l l i o n y e a r s based on 10 d e t e r m i n a t i o n s by Leech e t a l . (1963). Thus, age o f d e f o r m a t i o n and rnetamorphism i n the Cra w f o r d Bay a r e a i s c o n s i d e r e d sometime d u r i n g Lower M e s o z o i c and Upper P a l e o z o i c . - 86 -CITED REFERENCES ALBEE, A. L., I965*. D i s t r i b u t i o n o f Fe, Mg, and Mn Between Garnet and B i o t i t e i n N a t u r a l M i n e r a l Assemblages: J o u r . G e o l . , v o l . 73* no. 1, p. 155-164. CROSBY, P e r c y , i960: S t r u c t u r e and P e t r o l o g y o f the C e n t r a l Kootenay Lake A r e a , B r i t i s h C olumbia: U n p u b l i s h e d PhD. t h e s i s , H a r v a r d U n i v e r s i t y , Cambridge, Mass. DODDS, C. J . , 1965: A Study o f Garnets and Host Rocks from the C e n t r a l Kootenay Lake A r e a , S o u t h e a s t e r n B r i t i s h Columbia: MSc. T h e s i s , U n i v e r s i t y o f A l b e r t a : a b s t r a c t i n Can. Min. J o u r . FYLES, J . T., 1964: Geology o f the Duncan Lake A r e a , L a r d e a u D i s t r i c t , B r i t i s h Columbia: B.C. Dept. o f M i n e s , b u l l . no. 49. FYLES, J . T., and EASTWOOD, G. E. P., 1962: Geology o f t h e Ferguson A r e a , L a r d e a u D i s t r i c t , B r i t i s h Columbia: B.C. Dept. o f M i n e s , b u l l , no. 45. FYLES, J . T., and HEWLETT, C. G., 1959: S t r a t i g r a p h y and S t r u c t u r e o f the Salmo Lead-Z i n c A r e a : B.C. Dept. o f M i n e s , b u l l . no. 4 l . HEDLEY, M. S., 1955: L e a d - Z i n c D e p o s i t s i n the Kootenay A r c : Western M i n e r and O i l Review, v. 28, no. 7. LEECH, G.B., LOWDON, J . A., STOCKWELL, C. H., and WANLESS, R. K., 1963: Age D e t e r m i n a t i o n s and G e o l o g i c a l S t u d i e s : G e o l . Surv. Can., paper 63-17, p. 20-24. LITTLE, H. W., I960: N e l s o n Map-area, West H a l f , B r i t i s h Columbia: Geol. Surv. Can., mem. 308. - 87 -MATHEWS, W. H., 1953: Geology of the Sheep Creek Camp: B.C. Dept. of Mines, b u l l . no. 31. NGUYEN, K. K., SINCLAIR, A. J., and LIBBY, W. G., (in press): Age of the Northern Part of the Nelson Batholith: Can. J. Earth S c i . RICE, H. M. A., 1941: Nelson Map-area, East Half, B r i t i s h Columbia: Geol. Surv. Can., mem. 228. ROSS, J . V., (in press): Structural Relations of the Sushwap Complex near Revelstoke, Southeastern B r i t i s h Columbia: Can. J. Earth S c i . WALKER, J . P., 1928: Kootenay Lake D i s t r i c t , B r i t i s h Columbia: Geol. Surv. Can., sum. rept. pt. A, p. 119-135. 1934: Geology and Mineral Deposits of Salmo Map-area, B r i t i s h Columbia: Geol. Surv. Can., mem. I 7 2 . WALKER, J . F., and BANCROFT, M. F., 1929: Lardeau Map-area, General Geology: Geol. Surv. Can. mem. 161. WHEELER, J. 0 . , 1963: Rogers Pass Map-area, B r i t i s h Columbia and Alberta: Geol. Surv. Can., paper 62-32. I965: Big Bend Map-area, B r i t i s h Columbia: Geol. Surv. Can., paper 64-32. WINCHELL, H., 1958: The Composition and Physical Properties of Garnet: Am. Min., v o l . 43? p. 595-600. WONES, D. R., 1963: Physical Properties of Synthetic B i o t i t e s on the Join Phlogopite-Annite: Am. Min., v o l . 48, p. 1300-1321. CRAWFORD BAY MAP-AREA -4945 L E G E N D Granite and granodiorite LARDEAU GROUP Lardeau B Lardeau A Badshot Formation Mohican Formation HAMILL GROUP Upper Hamill Group 3 | Quartzite Range Formation Three Sisters Formation Horsethief Creek Group S Y M B O L S Geological contact; position defined, approximate, inferred. Fault. Compositional layering; inclined, vertical Cleavage; inclined, v e r t i c a l . Synform axial trace; overturned fold. Heavy shading delineates local observation of outcrop. Geology by K.W. Livingstone, 1967-M I L E S 10001 I 1 1 I I I I I I T ] IOOO M E T R E S 

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