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The structure of the Eastern belt of the Cordillera in Canada Smith, Alexander 1933

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THE STRUCTURE OF THE EASTERN BEIT OF THE CORDILLERA IN CANADA by Alexander Smith. A Thesis submitted f o r the Degree o f MASTER OF ARTS i n the Department o f GEOLOGY The U n i v e r s i t y o f B r i t i s h Columbia A p r i l , 1533. .Table.;of Contents. Page INTRODUCTION ..••..•••••»«••••••««»«»»•••»••»•••»»•••» I Chapter I . GEOGRAPHY AND TOPOGRAPHY Nomenclature of the C o r d i l l e r a i n Canada . 1 l o c a t i o n and Topography of the Various Mountain Ranges and I n t e r v e n i n g Trenches . •• 3 The S e l k i r k Ranges 3 The Rocky Mountain Trench 4 The E a s t e r n B e l t 7 The Rocky Mountains .............. 7 The F o o t h i l l s . . . . . .... 13 The Porcupine H i l l s 13 The Northern Mountains ........... 13 Drainage • .. 17 Chapter I I . GENERAL GEOLOGY Present extent o f the Formations of the d i f f e r e n t eras £0 O u t l i n e of G e o l o g i c a l H i s t o r y 21 Sedimentation 23 Character of the sediments ................. 24 The competency of the d i f f e r e n t f o r m a t i o n s . . 24 The o r i g i n of the Mesozoic sediments........ 25 The m i g r a t i o n of the geosyncl ine.... * 29 T o t a l t h i c k n e s s e s f o r s t r a t a deposited i n • . ~ v a r i o u s p a r t s of the g e o s y n c l i n e . . . . . . . . . 31 The age of moun t a i n ^ h u i l d i n g . 34 Table of Contents ( c o n t i n u e d ) . Page Chapter I I I . THE STRUCTURE OF THE EASTERN CORDILLERA General statement .............*..•........ 36 S e c t i o n I . The S e l k i r k - P u c e I I Ranges 37 Cranbrook Map-area 37 Windermere Map-area 41 Summary ........................ 44 S e c t i o n I I . The Rocky Mountain Trench. 4 9 t h P a r a l l e l 43 Cranbrook .. 47 Canal F l a t s 48 Lake Windermere 48 Steamboat Mountain 49 GrO X C L 6 H • • * • • « • • • • * « « • • • 0 0 s « * • * • • • « • • • • • * • • « • • « 51. Between Golden and P r i n c e George 34 P r i n c e George to F i n d l a y Forks ... 37 F i n d l a y R i v e r 58 Summary ................... 39 S e c t i o n I I I . The Rocky Mountains Proper. S t r u c t u r e along the I n t e r n a t i o n a l Boundary. 60 General d e s c r i p t i o n 61 Western s t r u c t u r a l area 61 C e n t r a l s t r u c t u r a l area 62 E a s t e r n s t r u c t u r a l a r e a . . . . . . . . . . 63 S t r u c t u r e i n the F l a t h e a d a r e a . . . . . . . . . . . . . . . . 63 The Lewis Thrust ..... 64 S t r u c t u r e i n T y p i c a l F o o t h i l l s areas between the I n t e r n a t i o n a l Boundary and Smoky R i v e r . The D i s t u r b e d B e l t of southwestern A l b e r t a . . • • 69 The Porcupine H i l l s . 69 The D i s t u r b e d B e l t proper. 70 The Lewis o v e r t h r u s t 74 S t r u c t u r e i n the Crowsnest Goal Area, A l b e r t a . 73 The Bighorn and Mountain Park B a s i n s . . . . . . . . . . 79 S t r u c t u r e i n the F o o t h i l l s Region to the east o f the Bi g h o r n , H i k a n a s s i n and Brazeau Ranges 83 Smoky R i v e r .................................. 87 S p e c i a l cases of s t r u c t u r e i n the F o o t h i l l s B e l t encountered i n the t r a c i n g and mining of c o a l seams ........... 88 Table of Contents ( c o n t i n u e d ) * ( S e c t . I I I . , Page The Rocky Mountains Proper) S t r u c t u r e along the main l i n e o f the C.P.R. and adjacent areas from the P l a i n s to the S e l k i r k Mount a i n s . 91 F o o t h i l l s , Bow R i v e r s e c t i o n ................ 91 Moose Mountain area 92 Rocky Mountain s e c t i o n ( K i c k i n g Horse and Bow R i v e r s ) .... 96 E a s t e r n B e l t of Thrusts 96 G e n t l y Folded B e l t 99 Western B e l t o f Thrusts 101 F i e l d Map-area 102 B e a v e r f o o t - B r i s c o Ranges .................... 109 S e l k i r k and Pur c e l l Mountains • • 113 Summary ............. 113 S t r u c t u r e a l o n g the main l i n e of the C.N.R.. 116 E a s t e r n B e l t of Thrusts I l 6 Gently Folded B e l t 119 Western B e l t (?) ............................ 119 Summary 119 S t r u c t u r e i n the Peace R i v e r Area 120 F o o t h i l l s area 121 The Rocky Mountains 123 Rocky Mountain Trench ....................... 123 Summary 124 Se c t i o n I V . S t r u c t u r e i n the Northern Mountains. I n t r o d u c t i o n ........... ... 124 Ranges east o f the Mackenzie ..................... 126 The F r a n k l i n Mountains 126 The Norman Mountains 127 Ranges west of the Mackenzie 128 The L i a r d Mountains 128 Mackenzie Mountains .. 129 Nahanni R i v e r s e c t i o n ................ 129 Root R i v e r s e c t i o n ................... 130 Dahadihni-Redstone area 131 l i t t l e Bear & Carcajou R i v e r areas ... 131 Richardson Mountains 132 Summary 132 g l i g g - X * S t r u c t u r e i n the A l b e r t a g a n a ^ i i 133 Table of Contents ( c o n t i n u e d ) . Summary o f S t r u c t u r e i n E a s t e r n C o r d i l l e r a .. . 1 3 4 Chapter IV. THEORIES OJT ORIGIN AND DEVELOPMENT OP FOLD MOUNTAIN SYSTEMS AND THEIR APPLICATION TO THE ROCKY MOUNTAINS Theories o f M o u n t a i n - B u i l d i n g 13& L a t e r a l Compression ..».» ..........•..»...•. 137 Theories of o r i g i n o f l a t e r a l compression... 138 Manner o f a c t i o n o f l a t e r a l compression 139 The d i r e c t i o n of the s t r e s s e s . . . . . . . . . . 140 I s o s t a s y and i t s r e l a t i o n to mountain-b u i l d i n g and ge o s y n c l i n e s «... 142 The s t r e n g t h of the e a r t h 1 s c r u s t 142 Peneplanation of mountain ranges 142 I s o s t a s y and g e o s y n c l i n e s . . . . . 142 The Substratum Geosynclines, t h e i r c h a r a c t e r i s t i c s , o r i g i n and development .««••«»•»»•»••«•«•••»»»»«•••«••»••••••••••• 144 C h a r a c t e r i s t i c s o f geosynclines . •. 145 Development of ge o s y n c l i n e s • 146 O r i g i n o f geosynclines 146 Types of deformation found i n the Rockies 132 Normal f a u l t i n g near the axes of F o l d Mountain systems lj>2 High-angle t h r u s t f a u l t s ........................ 13» The Development of The Development of The Development of The Development of 137 160 163 167 A b b r e v i a t i o n s B i b l i o g r a p h y . • PLATES « Page I , The Nomenclature of the Canadian C o r d i l l e r a . . 3 I I . The G e o l o g i c a l H i s t o r y of the Canadian Cor-d i l l e r a , ( a f t e r S.J. S c h o f i e l d ) . . . 21 I I I . I l l u s t r a t i n g the m i g r a t i o n and asymmetry of the C o r d i l l e r a n Geosyncline. ( a f t e r L i n k ; 30 IV. Cranbrook Map Area. 38 V. Windermere Map Area. 41 V I . S t r u c t u r e s e c t i o n s , Rocky Mountain Trench.... 46 V I I . S t r u c t u r a l areas of the southernmost Rockies i n Canada. 60 V I I I . S t r u c t u r e s e c t i o n across Rockies along 4 9 t h p a r a l l e l . 62 IX. Blairmore Map Area. 76 X. F o o t h i l l s S t r u c t u r e between the Saskatchewan and Smoky r i v e r s . 80 X I . S t r u c t u r e s e c t i o n s between Saskatchewan and Smoky r i v e r s . 83 Turner V a l l e y S t r u c t u r e . 92 Moose Mountain Region 93 XIV. S t r u c t u r e s e c t i o n s , Moose Mountain. Map Area. „ . » . . . « . . . . 9 5 XV. S t r u c t u r e s e c t i o n across Rocky Mountains, C . P i R . s e c t i o n , ( a f t e r Raymond).... 9 5 XVI. S t r u c t u r e s e c t i o n across Rocky Mountains, C.P.R. s e c t i o n , ( a f t e r A l l a n ) i n pocket, XVII . F i e l d Map Area 103 X V I I I , B e a v e r f o o t - B r i s c o Ranges* 110 XIX* S t r u c t u r e s e c t i o n , Athabasca r i v e r . ......... 117 XX. S t r u c t u r e section,, Mount Robson. . * 1 1 9 X I I . X I I I . PLATBS (continued) Page XXI. Peace R i v e r area. ........................... 121 X X I I . The A l b e r t a g e o s y n c l i n e . ............... *.... 134 X X I I I . The Caledonian wedge. F i g u r e s . 1. Diagrammatic shape o f C o r d i l l e r a n Geosyn-c l ine i n Canada. 33 2. S t r u c t u r e section,Cranbrook area. .„......,;. 38 3 . S t r u c t u r e s e c t i o n , Windermere area. ......... 41 4. Gen e r a l i z e d s t r u c t u r e , Rocky Mountain Trench. 3/ 3 . M o n o c l i n a l f a u l t b l ock, F l a t h e a d area. ...... 64 6. S t r u c t u r e s e c t i o n s i n the D i s t u r b e d B e l t . ... 71 7a . S t r u c t u r e s e c t i o n , Blairmore map area. 79 7b* S t r u c t u r e s e c t i o n , Bighorn Coal B a s i n . ...... .80 8. S t r u c t u r e s e c t i o n , F i e l d map a r e a . ........... 103 9 . S t r u c t u r e section,, B e a v e r f o o t - B r i s c o Range... 110 10. Redwall B r e c c i a , B e a v e r f o o t - B r i s c o Range..... 112 11. S t r u c t u r e s e c t i o n , P u r c e l l and S e l k i r k s , C.P.R. s e c t i o n . ........... 114 12. S t r u c t u r e s e c t i o n , Peace R i v e r area. ........ 121 13. S t r u c t u r e s e c t i o n , Cap Mountain. 127 14. S t r u c t u r e s e c t i o n , Nahanni r i v e r . ........... 130 13. Wedge Theory diagrams. 141 16 . A i r y ' s t h e o r y o f i s o s t a s y . .................. 147 17. P r a t t ' s theory o f i s o s t a s y . ................. 147 F i g u r e s (continued) Page 18. I s o s t a t i c adjustment and compression. ......... 149 X ^ o X S 0 S l » 8 . t } J L C 8.(1 ^ U.S t i l l l Q I l t j e e e o « e « a * e « « . 0 « e « A « e o e 0 O 4 « 6 X4- ^ 2 0 . R e l a t i v e movement of f a u l t blocks i n R o c k i e s . , . 1^4 2 1 . High-angle t h r u s t s , Rockies type, ............ 137 2 2 . High-angle t h r u s t s , F o o t h i l l s t y p e . ..,....<>.. 137 23-27, i n c l u s i v e . Stages i n the development of f o l d mountain systems .161-164 28* Generalized cross s e c t i o n of Rocky Mountain Table8. 1. M i g r a t i o n of the v a r i o u s g e o s y n c l i n e s . ........ 30 2 . V a r i a t i o n s i n t o t a l t h i c k n e s s of s t r a t a , ...... 34 3 . Thrust f a u l t s i n E a s t e r n B e l t along C.P.R. .... 98 INTRODUCTION Since the "beginning o f g e o l o g i c a l time many mountain ranges have appeared on the face of the e a r t h . Most of the a n c i e n t systems o c c u r r i n g i n the " S h i e l d " areas of the con-t i n e n t s have s u f f e r e d so from e r o s i o n t h a t only the r o o t s and cores o f the mountains remain on t h e i r now peneplaned s u r f a c e s . Other systems of more recent g e o l o g i c a l age, such as the Rock-i e s , the A l p s and the Himalayas, have undergone r e l a t i v e l y l i t t l e e r o s i o n and stand towering above the g e n e r a l l e v e l of the c o n t i n e n t s , mute and magnificent testimony to the mighty f o r c e s t h a t upheaved them. Many t h e o r i e s have been propounded to e x p l a i n the o r i g i n and a c t i o n of the f o r c e s of d i a s t r o p h i s m but none are s a t i s f a c t o r y . Orogeny i s shrouded i n the same mystery t h a t mocks human endeavour i n a l l i t s attempts to solve the workings of the u n i v e r s e . S c i e n c e , i n pushing back the v e i l , r e v e a l s a few t r u t h s and an ever-widening boundary of the unknown. Theories r i s e and f a l l as new g e o l o g i c a l data - i s - accumulated but as our s t o r e of knowledge i n c r e a s e s i t seems only to l e a d us f a r t h e r from any simple s o l u t i o n of the problem. The ancient mountain systems are now so eroded t h a t only t h e i r cores remain. These r o c k s , once b u r i e d deep beneath great t h i c k n e s s e s of sediments, have undergone compression, heating and igneous i n t r u s i o n . They are now so metamorphosed and complex that i n t e r p r e t a t i o n of orogenic f o r c e s from them i s extremely d i f f i c u l t , i f not i m p o s s i b l e ? f o r the g e o l o g i s t s of the present day. I t i s i n the younger and more impressive mountain ranges t h a t a s o l u t i o n o f the problem i s sought. There the evidences of great o r u s t a l s h o r t e n i n g and v e r t i c a l u p l i f t are to be found. E r o s i o n has not yet erased these s u r f a c e express-ions o f d i a s t r o p h i s m which enable one to see and a p p r e c i a t e the tremendous e a r t h movements. The s t r u c t u r e of these younger mountains, showing a l l the r e s u l t s of an orogenic movement, i s then a f a s c i n a t i n g study. In working on such a problem t h e r e i s no monotony. Although each b e l t i n the system has c e r t a i n c h a r a c t e r i s t i c s , every area has an i n d i v i d u a l i t y o f i t s own. Because o f d i f f e r e n c e s i n the type and t h i c k n e s s of the rock i n v o l v e d d i f f e r e n t s t r u c t u r e s may r e s u l t from a common f o r c e . To understand the s t r u c t u r e f a i r l y d e t a i l e d work must be done. The s t r a t i g r a p h y must be c a r e f u l l y worked out f o r i t i s e s s e n t i a l that the g e o l o g i s t know$ the r e l a t i v e p o s i t i o n s of the v a r i o u s formations i n the g e o l o g i c a l column. In the Rockies only w i d e l y separated areas have been mapped i n d e t a i l . This work has o f t e n r e v e a l e d s t r u c t u r e s e n t i r e l y d i f f e r e n t from those p r o v i s i o n a l l y mapped by the e a r l y e x p l o r -a t o r y workers. As the s t r u c t u r e v a r i e s i n the d i f f e r e n t areas the w r i t e r has not t r i e d to c o r r e l a t e the s t r u c t u r e s a c r o s s the gaps but d e s c r i b e s each area i n some d e t a i l to emphasize the t y p i c a l s t r u c t u r e s of each b e l t . Because of the great gaps between the areas s t u d i e d , a s t r u c t u r e map of the Rockies compiled from present knowledge would have l i t t l e s i g n i f i c a n c e . Maps of t y p i c a l areas i n each s t r u c t u r a l province are i n c l u d e d - I I I -i n t h i s t h e s i s . No a t t e m p t a t g e n e r a l i z a t i o n has been made, f o r the g r e a t e r the number o f f o r m a t i o n s i n t o w h i c h the s e d i -ments a r e d i v i d e d on t h e map, the b e t t e r w i l l t h e s t r u c t u r e be shown. S h o r t c h a p t e r s o r s e c t i o n s on t h e Geography and G e n e r a l G eology are i n c l u d e d . Such s e d i m e n t a r y problems a s a f f e c t t h e r e s u l t a n t s t r u c t u r e are d i s c u s s e d . I n the r e m a i n -i n g c h a p t e r s the S t r u c t u r e o f the R o c k i e s and a d j a c e n t r a n g e s i s d e s c r i b e d , the v a r i o u s t h e o r i e s o f m o u n t a i n - b u i l d i n g o u t l i n e d and t h e i r a p p l i c a t i o n i n the E a s t e r n C o r d i l l e r a shown. As J . Cummings and H.I. Thorne a r e d e a l i n g w i t h the s e d i m e n t a t i o n o f t h e R o c k i e s and F o o t h i l l s ( T u r n e r V a l l e y ) , r e s p e c t i v e l y , the w r i t e r has c o n f i n e d h i s a t t e n t i o n t o s t r u c t u r a l p r o b l e m s . Acknowledgment i s her e made t o Dr. S . J . S c h o f i e l d , Dr. M.Y. W i l l i a m s , and Dr. V. Dolmage, o f the Department o f Geology, U n i v e r s i t y o f B r i t i s h C o l u m b i a , f o r many h e l p f u l s u g g e s t i o n s and much i n f o r m a t i o n . Chapter I . GEOGRAPHY AND TOPOGRAPHY The Rocky Mountains and a s s o c i a t e d ranges "belong to the E a s t e r n B e l t of the C o r d i l l e r a of North America. They t r e n d i n a n o r t h w e s t e r l y d i r e c t i o n from Montana to the l i a r d r i v e r ( l a t i t u d e 6 l ° N ) . Only one low range of the Rockies crosses the H a r d , the main mountain masses being o f f s e t lj>0 m iles to the east to continue northward as the Mackenzie mountains and the s u b s i d i a r y F r a n k l i n range. The Richardson range f o l l o w s n o r t h along the west s i d e of P e e l r i v e r to the Mackenzie d e l t a , then swings to the west p a r a l l e l i n g the A r c t i c coast, marking the known n o r t h e r n e x t r e m i t y of the E a s t e r n B e l t . The f o l l o w i n g o u t l i n e ( a f t e r the Geographic Board of Canada) of the b e l t s of western Canada i s g i v e n to show the r e l a t i o n of the Ea s t e r n B e l t to the r e s t of the C o r d i l l e r a i n Canada. For the l o c a t i o n of the v a r i o u s f e a t u r e s the reader i s r e f e r r e d to P l a t e I , page 3 . Nomenclature of the C o r d i l l e r a i n Canada. I . Western B e l t (Vancouver I s l a n d Ranges. (a) I n s u l a r system (Queen C h a r l o t t e I s l a n d Range. ( S t . E l i a s Range. P a c i f i c Coast Downfold. (b) P a c i f i c system (Coast Range. (Cascade Range. I I . C e n t r a l B e l t (a) I n t e r i o r system ( F r a s e r P l a t e a u or P l a t e a u (Uechako P l a t e a u (b) C a s s i a r system (c) Yukon system or P l a t e a u (Babine Mountains ( S t i k i n e 11 ( B u l k l e y " ( C a s s i a r " (Omineca " (Yukon P l a t e a u ( O g i l v i e Range (Cariboo Mountains (Monashee *• -( S e l k i r k " (d) Columbia system (• - - r ( P u r c e l l Trench (-( P u r c e l l Mountains Rocky Mountain Trench I I I . E a s t e r n B e l t (a) Rockies system (Rocky Mountain Range ( and F o o t h i l l s . (Mackenzie Range ( F r a n k l i n Range (b) A r c t i c system (Richardson Range I ? . P r a i r i e B e l t (Great P l a i n s I n t h i s t h e s i s we are concerned only w i t h the E a s t e r n B e l t , but, i n order to b r i n g out c e r t a i n s t r u c t u r a l r e l a t i o n s h i p s . there are i n c l u d e d type areas i n the A l b e r t a geosyncline to the east of the F o o t h i l l s , a n d i n the S e l k i r k and P u r c e l l ranges to the west of the Rockies. The Rocky P l a t e I . THE K p M C I A T U R E OF THE CORDTXT^A IN CANADA. - 3 -Moantain Trench i s , as w i l l be shown l a t e r , g e n e t i c a l l y -a s s o c i a t e d w i t h the E a s t e r n B e l t . L o c a t i o n and Topography of the Various Mountain Ranges and I n t e r v e n i n g Trenches, (from west to east) (See Map I i n pocket.) The S e l k i r k Ranges. The S e l k i r k and P u r c e l l mountains occupy that p o s i -t i o n of B r i t i s h Columbia and Montana enclosed by the Kootenay and Columbia r i v e r s . The Columbia r i s e s near where the Kootenay enters the Rocky Mountain Trench at Canal F l a t s ; from there i t f l o w s n o r t h i n the Trench to the B i g Bend,^where i t swings south i n t o the n o r t h e r n end of the S e l k i r k s and flows south i n t o the U n i t e d S t a t e s . The Kootenay, on the other hand, flows south i n the Trench.to Montana where i t swings around the southern end of the range and r e - e n t e r s the province south o f Kootenay Lake. From there i t flows west to j o i n the Columbia near C a s t l e g a r . The area enclosed by these r i v e r s i s occupied by the S e l k i r k and P u r c e l l ' mountains. The S e l k i r k mountains are separated on the west from the Monashee mountains by the n o r t h - s o u t h S e l k i r k depression occupied by the south-flowing Columbia r i v e r . They are d i v i d e d from the P u r e e l I s by another north-south Trench known as the P u r c e l l " Trench. Bounding these ranges on the east l i e s the great Rocky Mountain Trench which separates them from the Eastern B e l t or Rocky Mountains. Schofield^" d e s c r i b e s the topography of the S e l k i r k s as f o l l o w s : "In a view from one o f the h i g h e r peaks of the S e l k i r k Range the most s t r i k i n g f e a t u r e i s the s e r i e s of almost unbroken r i d g e s , having an approximate e l e v a t i o n o f 7,000 f e e t . The r i d g e s t r e n d i n a l l d i r e c t i o n s without r e l a -t i o n to the u n d e r l y i n g s t r u c t u r e , and e v i d e n t l y represent the remnants of an u p l i f t e d and d i s s e c t e d p e n e p l a i n . Numerous peaks.having e l e v a t i o n s of from 8,000 to 9,000 f e e t p r o j e c t above t h i s o l d land s u r f a c e and great v a l l e y s have been carved to a depth of 6,000 f e e t below i t . " The P u r c e l l mountains, l y i n g between the P u r c e l l and Rocky Mountain Trench, form an e l l i p t i c a l - s h a p e d group of mountains about 2j?Q m i l e s long by 60 m i l e s wide. In the south the P u r c e l l s c o n s i s t o f , from west to e a s t , the Moyie, Yahk and M c G i l l v r a y ranges. The Rocky Mountain Trench. This great s t r u c t u r a l f e a t u r e g i v e s a very d e f i n i t e western boundary to the Rockies. I t extends from south of the 49th p a r a l l e l at l e a s t to the l i a r d r i v e r , a d i s t a n c e of n e a r l y 1000 m i l e s . Throughout i t s l e n g t h i t i s the course of numerous r i v e r s of v a r y i n g s i z e s f l o w i n g e i t h e r northwest or southeast. Northward from the I n t e r n a t i o n a l Boundary the r i v e r s occupying the Trench and t h e i r d i r e c t i o n s of flow are -Kootenay ( s o u t h ) , Columbia ( n o r t h ) , Canoe ( s o u t h ) , F r a s e r ( n o r t h ) , Crooked ( n o r t h ) , Pack ( n o r t h ) , P a r s n i p ( n o r t h ) , F i n d l a y ( s o u t h ) , Fox ( s o u t h ) , Kechika ( n o r t h ) , and Highland ( south). The Trench forms one of the g r e a t e s t topographic f e a t u r e s of the C o r d i l l e r a . I n l e n g t h and c o n t i n u i t y i t has few equals i n the wo r l d , being comparable i n s i z e to the R i f t v a l l e y s of A f r i c a and A s i a Minor. I t bears the same r e l a t i o n -s h i p to the Rockies as the Indus-Ganges trough does t o the Himalayas. S c h o f i e l d d e s c r i b e s some of i t s o u t s t a n d i n g . • 1 c h a r a c t e r i s t i c s as f o l l o w s : r S c h o f i e l d , S.J. T.R.S.C., 1920T^t«IH» PP*b3"b4~ ~ "One of the p e c u l i a r f e a t u r e s of the t r e n c h , whose w a l l s on both s i d e s r i s e , on an average, 4300 f e e t above the v a l l e y f l o o r , i s the f a c t t h a t i t i s occupied by streams which vary g r e a t l y i n s i z e . For example, the Kootenay r i v e r e nters the Trench as a l a r g e r i v e r from the n o r t h , w h i l e l e s s than a mile away from t h i s p o i n t , the n o r t h f l o w i n g Columbia has i t s beginning i n two s m a l l l a k e s . I n the same manner, the south f l o w i n g Canoe r i s e s and continues as a very small r i v e r to j o i n the mighty Columbia i n the Trench. From these examples which might have been g r e a t l y a m p l i f i e d , i t can be seen t h a t the s i z e and depth of the v a l l e y s which u n i t e l i n e a r l y to form the Rocky Mountain Trench bear no r e l a t i o n s h i p to the s i z e of the streams which occupy them, which i s c o n t r a r y to the r e -s u l t s of normal stream e r o s i o n . " The width of the Trench averages 4 to 6 m i l e s but i n places i s much g r e a t e r . The f l o o r of the Trench i s u s u a l l y f l a t or s l i g h t l y r o l l i n g , and i s covered by the unc o n s o l i d a t e d g r a v e l s and s i l t s of the Cenozoic. The w a l l s off the Trench r i s e a b r u p t l y from the f l o o r , e s p e c i a l l y on the e a s t e r n side which i s u s u a l l y p r e c i p i t o u s . This f e a t u r e i s most n o t i c e a b l e i n the southern part of the Trench. Another remarkable f e a t u r e of the Trench i s i t s u n i -form e l e v a t i o n of between 2 9 200 and 2,6.50 f e e t - a maximum d i f f e r e n c e of 450 f e e t i n e l e v a t i o n i n the 850 mile l e n g t h of the Trench. Drainage d i v i d e s have a uniform e l e v a t i o n of 2^00 f e e t . The s t r i k e of the Trench i s remarkably uniform o (about n o r t h 33 w e s t ) , as i t p a r a l l e l s the western f r o n t of the Rockies throughout - i t s e n t i r e l e n g t h . From the I n t e r n a t i o n a l Boundary to w i t h i n 100 m i l e s southeast of the B i g Bend of the F r a s e r , the Trench i s f l a n k e d on both s i d e s by h i g h mountains. From t h i s p o i n t to the Peace r i v e r i t i s bounded on the west by the I n t e r i o r P l a t e a u . Here i t i s not such a deep trough and between the B i g Bend of the Fr a s e r and the j u n c t i o n of the Pack and P a r s n i p r i v e r s i t s course i s hard to f o l l o w , but i t i s very probably occupied by the Crooked and Pack r i v e r s . In the F i n d l a y r i v e r d i s t r i c t the mountains to the west are as h i g h , i f not h i g h e r , than the Rockies to the e a s t , but are much l e s s rugged. l i t t l e has been w r i t t e n about the c o n t i n u a t i o n o f the Trench i n the Kechika r i v e r and n o r t h e r n areas. Some be-l i e v e t h a t i t may continue even to the A r c t i c , but i t probably dies out as a topographic f e a t u r e near the l i a r d r i v e r i n the Yukon P l a t e a u , where the h e a v i l y eroded s u r f a c e shows l i t t l e r e l a t i o n to rock s t r u c t u r e . Summary. The outstanding f e a t u r e s o f the Rocky Mountain Trench are -(1) I t s great l e n g t h of ever 1000 m i l e s . (2) U n i f o r m i t y of s t r i k e along the western "boundary of the Rockies. (3) Uniform e l e v a t i o n of drainage d i v i d e s i n the Trench, 2300 f e e t . (4) An o r i g i n independent of the present drainage system. The E a s t e r n B e l t . The Rooky Mountains. The Rocky mountains proper form the e a s t e r n p a r t of the C o r d i l l e r a from the Yukon i n the n o r t h to the Colorado Plateaus i n the south. I n Canada they extend from the I n t e r -n a t i o n a l Boundary n o r t h at l e a s t some 830 m i l e s to the X i a r d r i v e r and p o s s i b l y f a r t h e r . They are bounded on the west by the Rocky Mountain Trench and on the east by the F o o t h i l l s . a n d 0 Great P l a i n s . The general trend of the B e l t i s n o r t h 33 west, that i s , roughly s u b - p a r a l l e l to. the western coast of the con-t i n e n t . Between the 4 9 t h and 33rd p a r a l l e l s the system has an average w i d t h of 30 m i l e s , e x c l u s i v e of the F o o t h i l l s . N orth-ward i t d i m i n i s h e s to 40 m i l e s at the Peace r i v e r and d i e s out towards the L i a r d f o r only one range of the Rockies crosses that r i v e r . The Rockies are made up of a number o f p a r a l l e l ranges and r i d g e s which, i n a general way, l i e "en echelon", the more n o r t h e r l y segment: being s i t u a t e d s l i g h t l y west of the one to the south. The ruggedness of the topography v a r i e s i n d i f f e r e n t l a t i t u d e s . The highest p o i n t of the e n t i r e range i s P i k e s Peak, Colorado ( e l e v a t i o n 14,14? f e e t ) , but the mo st h i g h l y s c u l p t u r e d r i d g e s and ranges occur between Crowsnest Pass and the Robson d i s t r i c t where the peaks a t t a i n an average height of about 10,000 f e e t . Mount Robson ( 12 ,792 f e e t ) i n the Yellowhead Pass, i s the highest peak of the Canadian Rockies. From Yellowhead pass t o the n o r t h the Rockies g r a d u a l l y de-crease i n height to maximums:; of 6000 f e e t near the Peace r i v e r and 4000 f e e t at the l i a r d . . The Ranges of the Rocky Mountains. Many of the numerous ranges and r i d g e s of the Rocky mountains, e s p e c i a l l y i n the n o r t h e r n p a r t , are unexplored and unnamed. G e n e r a l l y the mountain mass i s d i v i d e d i n t o d i s t i n c t ranges, by t r i b u t a r y v a l l e y s , which p a r a l l e l the s t r i k e of the mountains. A short summary of the l o c a t i o n of the best known ranges f o l l o w s . • 1 Ranges along the 49th P a r a l l e l . Here Daly has 1 Daly, R.A. ' GTS.G. Mem.387 1912, P t . l , p.29* recognized f o u r ranges. The Lewis range - the most e a s t e r l y or f r o n t range o f the Rockies i n n o r t h e r n Montana - extends i n t o Canada about 3 m i l e s . There i t t u r n s s h a r p l y west and runs i n t h a t d i r e c t i o n f o r 6 m i l e s p r e s e n t i n g a steep face to the n o r t h . There the c o n t i n u i t y of the ranges i s broken by the depression occupied by the Waterton l a k e s and r i v e r . To the west of t h i s broad v a l l e y r i s e s the C l a r k e range which forms the f r o n t range n o r t h to C a s t l e r i v e r . West of the Clarke range l i e s the F l a t h e a d v a l l e y w i t h the MacDonald range to the west of i t . This range i s separated from the G a l t o n , the most western range of the Rocky mountains. The n o r t h e r n l i m i t o f the MaoDonaId and G a I t on r a n g e s a r e p l a c e d on 1 • • Dawson*s map a t the N o r t h K o o t e n a y P a s s and E l k r i v e r • 1 Dawson,G.M. G.S.G. Ann.Rept., , P t . B , p . 2 2 , " r e s p e c t i v e l y . N o r t h w a r d f r o m C a s t l e r i v e r t h e L i v i n g s t o n e range and Highwoo.d r a n g e s f o r m t h e o u t e r r i d g e o f t h e R o c k i e s and e x t e n d t o t h e Elbow r i v e r . The f o r m e r i s s e p a r a t e d from t h e mountains t o t h e west by an i n f o l d o f M e s o z o i c r o c k s about 10 m i l e s wide showing f o o t h i l l s t o p o g r a p h y . Ranges between t h e N o r t h K o o t e n a y and K a n a n a s k i s  P a s s . The mountains become more r e g u l a r and w e l l d e f i n e d 2 Dawson, G.Ml G.S.G. Ann.Rept. , I b b ^ , P t . B , p.22. n o r t h o f Crowsnest p a s s . The L i v i n g s t o n e range and i t s n o r t h e r n c o n t i n u a t i o n a s t h e Highwood range forms t h e o u t e r r i d g e o f the mountains and e x t e n d s n o r t h t o t h e Elbow r i v e r . The F l a t -head and H i g h r o c k r a n g e s f o r m a s e c o n d l i m e s t o n e r i d g e s i m i l a r t o the L i v i n g s t o n e r a n g e . These ranges c o n t i n u e t o the s o u r c e o f the Elbow r i v e r as t h e E l k m o u n t a i n s . I n t h i s l a t i t u d e t h e M i s t y range l i e s between the E l k mountains and t h e e a s t e r n o u t e r r a n g e , w h i l e the W i - s u k i - t s a k range t o the west forms a t h i r d r o u g h l y p a r a l l e l r i d g e . Beyond t h i s a v e r y h i g h and rough range l i e s t o t h e west o f E l k r i v e r . Between t h i s and the Hughes r a n g e , b o r d e r i n g the t r e n c h , i s a wide a r e a about w h i c h l i t t l e i s known. 2 Ranges between K a n a n a s k i s P a s s and t h e Bow r i v e r . T~"li:em.~ ] Between t h e upper E l k r i v e r and the Bow r i v e r t o the n o r t h , t h e - 1 0 -mountains have not the wide v a l l e y s (composed o f Cretaceous rocks) that are found i n the southern areas. They are com-posed o f 8 or 10 ranges but have o n l y two wide i n t e r v e n i n g v a l l e y s - the f i r s t between the headwaters of Kananaskis and Spray r i v e r s ; the second, occupied by the headwaters of the Zootenay r i v e r . The p a r a l l e l i s m o f these ranges i s not l e s s w e l l marked, but t h e i r c o n t i n u i t y i s f r e q u e n t l y i n t e r r u p t e d both by t r a n s v e r s e v a l l e y s and by the echelon - l i k e arrangement of the var i o u s ranges. F i s h e r * s range here c o n s t i t u t e s the ea s t e r n f r o n t o f the mountains. Behind i t a second r i d g e i s formed by a some-what i r r e g u l a r range which ends i n Pigeon mountain on the Bow. To the west a second r i d g e i s formed by a somewhat i r r e g u l a r range which ends i n Pigeon mountain on the Bow. The Opal mountains and connecting e l e v a t i o n s ending i n Rundle mountain form a t h i r d range, w h i l e the Kananaskis and Goat ranges w i t h Terrace mountain c o n s t i t u t e a f o u r t h . "The Spray and Bourgeau mountains are the best known p o r t i o n s of a f i f t h p a r a l l e l range, and a s i x t h runs northward from P i l o t mountain but d i e s out before r e a c h i n g the White Man*s pass. The Blue mountains and connecting r i d g e s ending i n Mt. B a l l on the V e r m i l l i o n Pass, form a wide and somewhat i r r e g u l a r seventh range. Between t h i s and the important r i d g e formed by the M i t c h e l l and V e r m i l l i o n ranges there are probably two short i n t e r c a l a t e d ranges of which the ends are seen on the Cross r i v e r . The B r i s c o and Scanford ranges con-s t i t u t e the western e l e v a t i o n s o f the Hookies i n t h i s p a r t and -11-are wider and more p e r s i s t e n t than most o f the ranges mentioned above." Ranges "between the Bow and Athabasca r i v e r s . North of the Bow r i v e r and V e r m i l l i o n Pass the p a r a l l e l i s m of the c o n s t i t u e n t ranges i s continued i n the Fairholme, P a l l i s e r and Saw Back ranges. The Bow range and the Waputtehk mountains which south of the K i c k i n g Horse pass form a very massive range t o the west, i n the v i c i n i t y of the pass, become broken up i n t o r a t h e r i r r e g u l a r groups of mountains. The l o f t y O t t e r -t a i l mountains are continued to the northwest by two ranges, the Van Horne mountains and the Mt. Hunter range. The Beaver-f o o t range, r e a l l y a c o n t i n u a t i o n of the B r i s c o range, f r o n t s on the Columbia v a l l e y or Rocky Mountain t r e n c h . To the n o r t h of the areas d e s c r i b e d the w r i t e r has been unable to f i n d any systematic nomenclature o f the ranges, very l i t t l e t o p o g r a p h i c a l or g e o l o g i c a l work has been done i n the i n t e r i o r ranges. To the north of the Sawback and P a l l i s e r ranges l i e s the Bighorn range. I t i s bounded on the west by the broad d e p r e s s i o n of Mesozoic rocks c o n t a i n i n g the Bighorn and Mountain Park c o a l b a s i n s . The western boundary of t h i s b a s i n i s the N i k a n a s s i n range. On the western s i d e o f the mountain mass the Van Horne range oontinues to the n o r t h as the Spencer range. Ranges along the Athabasca. '" Prominent ranges along the Canadian N a t i o n a l Railway (Yellowhead pass and Athabasca r i v e r ) a re, from east to west, the N i k a n a s s i n range and i t s no r t h e r n c o n t i n u a t i o n as the Boule range, the C o l i n and -12-Maligne ranges. Many of the prominent ranges are not named. The mountains reach t h e i r h i g h e s t e l e v a t i o n i n Mt. JRobson (13,068 f e e t ) . To the north the mountain mass decreases g r a d u a l l y i n height and w i d t h to the l i a r d . O u t l i e r s between the I n t e r n a t i o n a l Boundary and the  Athabasca. S e v e r a l ranges o f Rocky mountain s t r u c t u r e l i e i n the F o o t h i l l s B e l t separated from the e a s t e r n f r o n t ranges by wide areas of Cretaceous r o c k s . Because of the more r e s i s t a n t nature of t h e i r s t r a t a - g e n e r a l l y Devonian limestone - these o u t l i e r s have g r e a t e r e l e v a t i o n s than the surrounding f o o t h i l l s but are not as h i g h as the f r o n t ranges. The f o l l o w i n g ranges may be c l a s s e d as o u t l i e r s T u r t l e Mountain 0 ) see map,IXy page,7b. L i v i n g s t o n e Range ) Forget-me-not Ridge ) ) see map,2111^ page 9 3 . Moose Mountain ) Brazeau Range ) N i k a n a s s i n Range ) see m©p,Xy page 80 . Bighorn Range ) The F r o n t a l Escarpment. This l i n e of demarcation between the f o o t h i l l s and 0 0 the Rockies i s even more pronounced from l a t i t u d e 49 to 33 N than the w e s t e r l y l i m i t o f the mountain system. A prominent escarpment 2 ,300 to 3000 f e e t h i g h , i n p l a c e s almost perpen-d i c u l a r , and composed l a r g e l y o f massive-bedded gray limestone s t r a t a , s h a r p l y d e f i n e s the mountain topography from the -13-round-topped r i d g e s that form the i n n e r f o o t h i l l s . T h i s almost continuous escarpment i s the r e s u l t of the o v e r t h r u s t i n g which occurred along the l e w i s and s i m i l a r t h r u s t f a u l t s . North o f the Athabasca t h i s f r o n t a l escarpment i s not so continuous or h i g h because o v e r t h r u s t i n g has been r e p l a c e d to some extent by f o l d i n g . I n the Peace r i v e r area the l i n e o f demarcation be-tween the f o o t h i l l s and the Rockies i s not so d i s t i n c t . The former are r e l a t i v e l y h i g h (3000 f e e t ) , more rounded In con-t o u r , and wooded to t h e i r caps. The l a t t e r are more rugged and t h e i r summits are bare, as v e g e t a t i o n f l o u r i s h e s b e t t e r on the f o o t h i l l s u n d e r l a i n by the s o f t e r Cretaceous rocks than i n the mountains of harder Pre-Oambrian and P a l a e o z o i c r o c k s . The F o o t h i l l s . 1 Stewart's general d e s c r i p t i o n of the F o o t h i l l r e g i o n 1 Stewart, J.S. ,G*S.C. Mem.112. 1919. P . 1 1 . ~_" i s : "The F o o t h i l l s form a b e l t , averaging 10 to 20 m i l e s i n width bordering the east s i d e of the Rockies f o r p r a c t i c a l l y t h e i r e n t i r e l e n g t h . They form a d i s t i n c t topographic f e a t u r e , though they merge g r a d u a l l y i n t o the p l a i n s to the e a s t . The mountains g e n e r a l l y r i s e a b r u p t l y from the f o o t h i l l s , but i n a few p l a c e s the two are so n e a r l y a l i k e i n height that they can be d i s t i n g u i s h e d m ainly by the l a c k of s o i l and v e g e t a t i o n on the limestones and q u a r t z i t e s forming the f r o n t range." The base l e v e l of the Rockies on the f o o t h i l l s s i d e i s much higher than on the western s i d e . On the east, as a s c e r t a i n e d by t a k i n g the average l e v e l at which the streams -14-leave the mountains proper and pass i n t o the f o o t h i l l r e g i o n i s about 4 , 3 0 0 f e e t . On the west, the average e l e v a t i o n of the Rocky Mountain Trench i s 2,300 f e e t . In consequence of t h i s d i f f e r e n c e the passes have a steep and sudden descent to the west of the watershed i n c o n t r a s t to the more gra d u a l slope to the e a s t . The F o o t h i l l s are composed of i n t e n s e l y f o l d e d and f a u l t e d s t r a t a , u s u a l l y Cretaceous, and have the g e n e r a l northwest trend p a r a l l e l to the mountains. Their present r e l i e f i s due to the d i f f e r e n t i a l e r o s i o n of the v a r i o u s f o r m a t i o n s . In the southern p a r t of the Rockies they r i s e g r a d u a l l y from the r o l l i n g p l a i n s although the l i n e of demar-c a t i o n between the n e a r l y f l a t - l y i n g s t r a t a of the p l a i n s and the f o l d e d and f a u l t e d rocks o f the f o o t h i l l s i s u s u a l l y sudden and d i s t i n c t . E l e v a t i o n s up to 3»&00 f e e t occur i n the south where the Rockies are h i g h . For 23 m i l e s n o r t h of the I n t e r n a t i o n a l Boundary the f o o t h i l l s are l a c k i n g . I t i s thought t h a t the Lewis o v e r t h r u s t block once o v e r l a y the r e g i o n and p r o t e c t e d t h i s p o r t i o n from the f o l d i n g and f a u l t i n g which a f f e c t e d the f o o t h i l l s . Since the b u i l d i n g of the mountains e r o s i o n i s supposed to have moved the f a u l t - l i n e scarp 8 m i l e s to the west, exposing the u n d e r l y i n g Cretaceous as r o l l i n g p l a i n s . The F o o t h i l l s continue to the L i a r d w i t h decreasing a l t i t u d e corresponding w i t h the decreasing a l t i t u d e o f the Rockies n o r t h of the Athabasca. However the l i n e o f demarca-- 1 5 -t i o n between the two types becomes l e s s pronounced as one t r a v e l s northward. This i s because the o v e r t h r u s t i n g and the r e s u l t a n t steep escarpment of the Front ranges i n the south decrease to the north and i s replaced to some extent by f o l d -i n g . Large r i v e r s l i k e the Bow and Athabasca have eroded wide v a l l e y s i n the F o o t h i l l s , g i v i n g them the appearance of western extensions of the P l a i n s . The Porcupine H i l l s . These extend ( t o east o f the F o o t h i l l s ; i n a b e l t between the Oldman and Highwood r i v e r s . They are composed o f f l a t - l y i n g T e r t i a r y rocks not i n v o l v e d i n the b u i l d i n g of the Rockies but made up of sediments d e r i v e d from t h e i r e r o s i o n . They are t h e r e f o r e not a part o f the C o r d i l l e r a n system but belong i n the P l a i n s B e l t . The Northern Mountains. The Rocky mountains s t r i k e the L i a r d r i v e r near o l o n g i t u d e 125 W. Here the c o n t i n u i t y of the Rockies i s i n t e r r u p t e d and they appear to die away north of the r i v e r . Under the name Mackenzie mountains, however, the C o r d i l l e r a s p r i n g s up again n o r t h of the r i v e r , but i t s e a s t e r n f r o n t i s stepped f a r to the eastward and abuts a g a i n s t the L i a r d r i v e r at F o r t L i a r d . From t h i s p o i n t the e a s t e r n boundary of the C o r d i l l e r a runs northward touching the Mackenzie r i v e r at the mouth of the Nahanni r i v e r and c o n t i n u i n g thence along the o western s i d e of the Mackenzie to l a t i t u d e 66 where i t runs i n t" -16-a broad curve and swings westward round the headwaters of Pe e l r i v e r . The Mackenzie mountains d ie out about the head of P e e l r i v e r i n much the same way as the Rockies n o r t h o f the l i a r d r i v e r , but another range, known as the Richardson moun-t a i n s , s p r i n g s up n o r t h of P e e l r i v e r and extends down to the A r c t i c c oast, i t s e a s t e r n f r o n t f o l l o w i n g c l o s e l y the v a l l e y of P e e l r i v e r and r i s i n g as an abrupt f a u l t scarp out of the d e l t a of the Mackenzie. "Mackenzie mountains extending from the L i a r d r i v e r o o i n l a t i t u d e 60 to l a t i t u d e 66 form the main n o r t h e a s t e r n d i v i s i o n of the Rocky Mountain system and are o f f s e t about 1 150 m i l e s to the east of the main trend o f i t s a x i s . " The T l . i l l i a m s . M.Y. Bull.Geol.3oc.Am., V o l . 3 5 . 1929, p.449. ~~ F r a n k l i n mountains form a s u b s i d i a r y and extreme n o r t h e a s t e r n d i v i s i o n of the system, t h e i r a x i s l y i n g 20 to 50 m i l e s east of the F ront of the Mackenzie mountains. F r a n k l i n mountains l i e east of the Mackenzie r i v e r and extend from Willow Lake r i v e r , l a t i t u d e 62 Ay n o r t h to an unknown d i s t a n c e beyond Great Bear r i v e r , p r o b a b ly to l a t i -0 tude 65 30» n o r t h . At Willow Lake r i v e r the f r a n k l i n and Mackenzie mountains are o n l y a score of m i l e s a p a r t , and i n the v i c i n i t y of W r i g l e y s m a l l mountains on both s i d e s of Mackenzie r i v e r form connecting l i n k s between the two chains. The trend of the Mackenzie mountains i s n o r t h w e s t e r l y i n the southern part and almost east and west i n the n o r t h . At the s outh they r i s e somewhat a b r u p t l y from the l o w - l y i n g l e v e l r e g i o n to he i g h t s of about 6000 f e e t and on Gravel r i v e r the -17-h i g h e s t summits r e a c h a maximum of 8000 f e e t . Keele d e s c r i b e s them as "the g r e a t e s t mountain group i n Canada and (they) appear to c o n s i s t o f two ranges, an o l d e r western range, agai n s t the e a s t e r n edge of which a newer range has been 1 p i l e d . " To the north they decrease i n e l e v a t i o n an2 appear to •1 K e e l e , J . Geol.Surv.Can.. 1910. No.1097. die but at the headwaters of P e e l r i v e r i n a comparatively low r e g i o n broken o n l y by a few f a u l t scarps and a n t i c l i n a l r i d g e s . The F r a n k l i n s reach a maximum e l e v a t i o n of 5000 f e e t i n Cap mountain to the n o r t h of which peaks o f 5000 f e e t are e x c e p t i o n a l . This range seems to be c h a r a c t e r i z e d by steep e a s t e r l y escarpments and g e n t l e slopes to the west. The Richardson mountains are c o n s i d e r a b l y lower i n e l e v a t i o n than the Mackenzie mountains. They s t r i k e n o r t h to west of the Mackenzie d e l t a and swing to the west p a r a l l e l i n g 2 the A r c t i c c oast. McConnell d e s c r i b e s them as c o n s i s t i n g 2 McConnell, R.G. G.S.C., Vol.IV. 1888-89. P.119P. e s s e n t i a l l y o f two ranges separated by a wide l o n g i t u d i n a l v a l l e y and f l a n k e d on e i t h e r side by h i g h p l a t e a u s . The higher peaks are estimated to have an a l t i t u d e of 4000 f e e t . The summits of t h i s n o r t h e r n d i v i s i o n are u s u a l l y rounded i n out-l i n e and show few sharp peaks, a f e a t u r e which may be due e i t h e r to mature e r o s i o n or to l a c k o f c l o s e f o l d i n g of the s t r a t a . Drainage. Between the 49th and 54th p a r a l l e l s the c o n t i n e n t a l d i v i d e s e p a r a t i n g the areas d r a i n i n g to the P a c i f i c from those -18-d r a i n i n g east to the Hudson's Bay l i e s w i t h i n the Rocky mountains. One would expect the P a c i f i c - A r c t i c d i v i d e to f o l l o w the Rookies from there n o r t h at l e a s t to the L i a r d . But t h i s i s not the case. The Peace r i v e r has i n some remark-able way maintained i t s channel across the Rockies and dra i n s a l a r g e p o r t i o n of n o r t h e a s t e r n B r i t i s h Columbia. Much could be w r i t t e n about the drainage o f the Rockies and i t s development. For a concise statement the reader i s r e f e r r e d to the paper by S c h o f i e l d , "The O r i g i n of 1 the Rocky Mountain Trench". 1 S c h o f i e l d , S.J. T.R.S.C.. Sec.IV. 1920, p.bb. Because the slope to the Trench i s much steeper,as w e l l as s h o r t e r , t h a n the slope to the p l a i n s , the drainage d i v i d e i s much nearer the former; hence the r i v e r d r a i n i n g i n t o the Trench are short and s w i f t , and those f l o w i n g to the p l a i n s are l o n g e r , l a r g e r and have a more gradual g r a d i e n t . The r i v e r s mentioned i n t h i s t h e s i s are shown on . o Map , page 18. The whole mountain system n o r t h o f 54 N i s drained by the Mackenzie and i t s t r i b u t a r i e s . The Peace has maintained i t s channel across the mountains w h i l e the L i a r d swings around the no r t h e r n e x t r e m i t y of the Rockies and the southern e x t r e m i t y of the Mackenzie mountains. The Canadian Rockies are remarkable f o r the number of t h e i r t r a n s v e r s e v a l l e y s o r passes. These do not cut s t r a i g h t across the mountains but f o l l o w a z i g - z a g course along l o n g i t u d i n a l v a l l e y s and around the low p o i n t s of r i d g e s . They are supposed to be formed by the drainage main-- 1 9 -t a i n i n g f o r a time i t s o l d eastward d i r e c t i o n a c r o s s the r i s i n g Hocky m o u n t a i n s . The Peace and L i a r d r i v e r s have "been a b l e to keep pace w i t h the u p l i f t and by e r o s i o n have main-t a i n e d t h e i r c h a n n e l s a c r o s s the m o u n t a i n s . - 2 0 -Chapter I I . GENERAL GEOLOGY. The mountains o f the E a s t e r n C o r d i l l e r a are formed almost e n t i r e l y of sediments, which, i n comparison to most mountain systems are r e l a t i v e l y u n d i s t u r b e d and unmetamor-phosed. The s t r a t a i n v o l v e d are remarkably conformable and no great e r o s i o n breaks are known. Present extent of the formations of the d i f f e r e n t e r a s . B e l t i a n sediments are represented mainly i n the r e g i o n contiguous w i t h the 4 9 t h P a r a l l e l and a l s o along the a x i s o f the system, wherever the Rockies have been e x p l o r e d . I n the Peace r i v e r area the M i s s i n c h i n k a s c h i s t s have been p l a c e d t e n -1 2 t a t i v e l y i n the Pre-Cambrian and W i l l i a m s has c o r r e l a t e d the 1 P.G.E. Resources Survey Report No. p. 2. W i l l i a m s , M.Y. G.S.C. Summ.Rept., 1922, Pt.B, p.72.  lowest formations outcropping i n the F r a n k l i n mountains w i t h the B e l t i a n . P a l a e o z o i c sediments occur throughout and form the bulk of the s t r a t a exposed i n the Rockies and Mackenzie moun-t a i n s . Mesozoic formations are found c h i e f l y i n the i n l i e r s and F o o t h i l l s . T e r t i a r y rocks are recorded i n the Kishenena v a l l e y of the southern R o c k i e s , i n the Rocky Mountain Trench along the F i n d l a y r i v e r , and along the Mackenzie i n the v i c i n -i t y of Norman. The s u p e r f i c i a l d e p o s i t s i n the v a l l e y s and basins are o f P l e i s t o c e n e and Recent ages. Igneous rocks are conspicuous by t h e i r s c a r c i t y and . • ' -21-are not known n o r t h o f the main l i n e of the Canadian P a c i f i c Railway. For a good account of the igneous geology and ore d e p o s i t s of the Rocky mountains the reader i s r e f e r r e d to the _ •• 1 . t h e s i s of D.F. K i d d . ~ -->• 1 K i d d , D.F.: " M i n e r a l i z a t i o n of the Rocky Mountains". T h e s i s , U.B.C., 1927* O u t l i n e of G e o l o g i c a l H i s t o r y . A l l students of North American geology know the gen e r a l o u t l i n e of events which culminated i n the b u i l d i n g of the Rocky mountains. (See P l a t e X I , page 21.) I . D e p o s i t i o n of the Pre-Cambrian sediments i n a r e l a -t i v e l y deep assymmetrical g e o s y n c l i n e connected w i t h the . . . . I P a c i f i c ocean. These sediments were d e r i v e d from Casoadia *• 2 !• whose ea s t e r n border at that p e r i o d S c h o f i e l d b e l i e v e s t o 2 S c h o f i e l d , S.J. T.R.S.C., Vol.17 • Sec.IV, 192?, P»93» have been near the present s i t e of the Arrow l a k e s . The narrow deeper part of the g e o s y n c l i n e probably l a y west o f the present Rocky mountains and c l o s e to the o l d borderland. I t i s t r u e t h a t B e l t i a n limestones are found i n the Rocky mountains and not i n the P u r c e l l s but t h i s i s probably the r e s u l t of .quieter waters f a r t h e r from the o l d l a n d mass ra t h e r than to any t h i c k e n i n g i n B e l t i a n sedimentation towards the R o c k i e s . — No. t h i c k e n i n g of other Pre-Cambrian s t r a t a towards the Rockies has been noted. The B e l t i a n g e osyncline probably d i d not extend as f a r east as the present edge of the Pre-Cambrian s h i e l d since no B e l t i a n sediments are found e i t h e r ' -22?- • on the S h i e l d o r a l o n g i t s m a r g i n s . I I . The d e p o s i t i o n o f P a l a e o z o i c s e d i m e n t s on t o p o f the P r e -Cambrian s t r a t a w i t h o u t i n t e r r u p t i o n by d i a s t r o p h i c movements o f the f i r s t o r d e r . The deeper p a r t o f t h i s b r o a d e r g e o s y n -c l i n e l a y somewhat e a s t o f t h e P r e - C a m b r i a n s i t e o f g r e a t e s t d e p o s i t i o n as i n d i c a t e d by the u n c o n f o r m a b l e c o n t a c t o f D e v o nian on B e l t i a n a l o n g t h e w e s t e r n boundary o f the Rocky M o u n t a i n T r e n c h . T h i s P a l a e o z o i c g e o s y n c l i n e was much w i d e r and e x t e n d e d f a r t o t h e e a s t t o o v e r l a p t h e C a n a d i a n S h i e l d a l o n g i t s p r e s e n t b o r d e r . The C a m b r i a n , O r d o v i c i a n , and e a r l y D e v o n i a n seaways appear t o have been much more r e s t r i c t e d i n t h e E a s t e r n C o r d i l l e r a t h a n t h a t o f the M i d d l e D e v o n i a n . W a l c o t t r e s t r i c t s the C a m b r i a n g e o s y n c l i n e to t h e a r e a now o c c u p i e d by t h e R o c k i e s . I I I . B r o a d d i f f e r e n t i a l upwarp a t t h e c l o s e o f P a l a e o z o i c t i m e . P o s s i b l y o n l y a s l i g h t i n t e r r u p t i o n o f d e p o s i t i o n i n the d e epest p a r t o f the g e o s y n c l i n e as e v i d e n c e d by t h e ab-sence o f an u n c o n f o r m i t y between t h e T r i a s s i c and P a l a e o z o i c s i n the B a n f f a r e a . The e a s t e r n o r s h a l l o w e r p a r t o f t h e P a l a e o z o i c seaways s u f f e r e d g r e a t e r e r o s i o n - w i t h o u t i n t e n s e f o l d i n g o r f a u l t i n g - as i n d i c a t e d by t h e t r u n c a t i o n o f t h e o l d e r beds e a s t w a r d f rom the mountains towards the C a n a d i a n S h i e l d . I V . Encroachment o f the T r i a s s i c and J u r a s s i c seas from the P a c i f i c s o u t h w e s t , w i t h the s i t e s o f g r e a t e s t a c c u m u l a t i o n a t , - 2 3 - • or s l i g h t l y eastward from the previous g r e a t e s t depth of P a l a e o z o i c d e p o s i t i o n . Vulcanism and s l i g h t d i a s t r o p h i c movements during t h i s p e r i o d ; these e f f e c t s were probably the fore r u n n e r s of the J u r a s s i d e R e v o l u t i o n . V. B u i l d i n g of the P u r c e l l and S e l k i r k mountains to the west at the c l o s e of the J u r a s s i c . V I . D e p o s i t i o n o f the Lower and Upper Cretaceous sediments i n a broad widespread g e o s y n c l i n e whose deepest part l a y c l o s e to the s i t e of the present Rocky mountains. Sediments d e r i v e d from the u p l i f t e d J u r a s s i d e mountains to the west. This en-croachment of the sea came from the G u l f o f Mexico and the A r c t i c . V o l c a n i c e x t r u s i o n of l o c a l s i g n i f i c a n c e as evidenced by the Crowsnest v o l c a n i c s above the Blairmore beds. V I I . The b u i l d i n g of the Rockies. D i a s t r o p h i c movements of the f i r s t order i n v o l v i n g sediments o f Pre-Cambrian, P a l a e o z o i c and Meso z o i c age, r e s u l t i n g i n the b u i l d i n g of the Rocky mountains and F o o t h i l l s . V I I I . General u p l i f t of mountain b u i l t sediments. E r o s i o n contemporaneous w i t h and subsequent to mountain b u i l d i n g . Ter-t i a r y c o n t i n e n t a l sedimentation i n the shallow A l b e r t a geosyncline l y i n g east of the F o o t h i l l s B e l t . Sedimentation. For a d e t a i l e d account of the sedimentation o f the Rocky mountains the reader i s r e f e r r e d to "Pre-Lararaide • 1 Formations of the Rocky Mountains" by J . Curamings. To b r i n g 1 T h e s i s , U.B.C. , IjJT. out the r e l a t i o n s h i p of the s t r u c t u r e to the sedimentation the f o l l o w i n g p o i n t s i n sedimentation are d i s c u s s e d below: I . The c h a r a c t e r of the sediments. I I . The competency of the d i f f e r e n t f o r m a t i o n s . I I I . The o r i g i n of the Mesozoic sediments. . IV. The m i g r a t i o n of the g e o s y n c l i n e . V. T o t a l t h i c k n e s s e s f o r s t r a t a d e p o s i t e d i n v a r i o u s p a r t s of the g e o s y n c l i n e . V I . The age of mountain b u i l d i n g . I . The Character of the sediments. The s t r a t a d e p o s i t e d i n the e a s t e r n C o r d i l l e r a n geo-s y n c l i n e from B e l t i a n to lower Gretaceous times are a l l shallow water marine sediments l a i d down at depths probably l e s s than 600 f e e t . When compared w i t h the great t h i c k n e s s o f sediments l a i d down - over 53 ,000 f e e t - the p o s s i b l e f l u c t u a t i o n s i n the depth of water are very s m a l l . This i n d i c a t e s a very c l o s e r e l a t i o n s h i p between the r a t e of d e p o s i t i o n and the rat e of s i n k i n g of the g e o s y n c l i n e . The t h e o r i e s put f o r t h to e x p l a i n t h i s phenomenon w i l l be d i s c u s s e d i n a l a t e r chapter. I I . The competency o f the d i f f e r e n t f o r m a t i o n s . The c h a r a c t e r of the sediments i n v o l v e d i n the mountain b u i l d i n g determines the r e s u l t i n g s t r u c t u r e . Compe-tent s t r a t a y i e l d to t a n g e n t i a l s t r e s s w i t h r e s u l t s d i f f e r e n t to those produced when incompetent s t r a t a are acted upon by . . -25" : t h e same f o r c e s . I n g e n e r a l , a competent s e r i e s f a i l s by f a u l t i n g , an i n c o m p e t e n t one,by c l o s e and. ove r t u r n e d , f o l d i n g f o l l o w e d by f a u l t i n g . The B e l t i a n f o r m a t i o n s , t h e Cambrian, D e v o n i a n and C a r b o n i f e r o u s l i m e s t o n e s and q u a r t z i t e s a re t h e c o n s p i c u o u s l y competent s t r a t a o f the E a s t e r n C o r d i l l e r a . They o u t c r o p i n th e P u r c e l l , and S e l k i r k mountains and a l s o i n t h e C e n t r a l B e l t o f t h e R o c k i e s . I n t h e s e a r e a s g e n t l e f o l d i n g and b l o c k f a u l t i n g i s the r u l e . The base o f t h e o v e r t h r u s t b l o c k s i s i n v a r i a b l y made up o f competent s t r a t a . The l e s s competent s a n d s t o n e s and s h a l e s a r e u s u a l l y f o l d e d and f a u l t e d . T h i c k beds of s h a l e are o f t e n s h e a r e d , making the l o c a t i o n o f f a u l t p l a n e s d i f f i c u l t . T h i s i s p a r -t i c u l a r l y t r u e o f t h e M e s o z o i c s e d i m e n t s ; t h e s e o u t c r o p i n t h e i n l i e r s and f o o t h i l l s o f t h e E a s t e r n B e l t o f c l o s e f o l d i n g and o v e r t h r u s t i n g . I I I . The o r i g i n o f the M e s o z o i c s e d i m e n t s . Recent work on t h e M e s o z o i c s e d i m e n t a t i o n o f the R o c k i e s and F o o t h i l l s has b r o u g h t f o r t h much d i s c u s s i o n on t h e . o r i g i n o f t h e s e f o r m a t i o n s . Because t h e pr o b l e m has su c h an i m p o r t a n t b e a r i n g on the development o f Rocky mo u n t a i n s t r u c t u r e each o f the f o u r h y p o t h e s e s as t o c o n d i t i o n s a t t h i s t i m e i s d i s c u s s e d b elow. The l o w e r C r e t a c e o u s f o r m a t i o n s o f s o u t h w e s t e r n A l b e r t a a r e m o s t l y c o n t i n e n t a l d e l t a i c d e p o s i t s w h i l e i n t h e n o r t h m a r i n e s e d i m e n t a t i o n was t a k i n g p l a c e . The s e d i m e n t s o f b o t h a r e a s came from t h e newly u p l i f t e d J u r a s s i d e mountains wra; - 2 6 -t o the w e s t . M e s o z o i c s e d i m e n t s are n o t f o u n d west o f a l i n e drawn a p p r o x i m a t e l y a l o n g t h e a x i s o f the R o c k i e s . N e v e r t h e -l e s s t h e y t h i c k e n r a p i d l y t o t h e w e s t . T h i s i s i n d i c a t i v e t h a t e i t h e r t h e y were c l o s e t o t h e o l d s h o r e l i n e o r t h a t tremendous t h i c k n e s s e s o f t h e s e r o c k s were once d e p o s i t e d i n what i s now the C e n t r a l and W e s t e r n B e l t s o f t h e R o c k i e s and have s i n c e been e n t i r e l y removed by e r o s i o n . The c h e r t y p e b b l e s o f the c o n g l o m e r a t e a t t h e base o f the B l a i r m o r e must have been d e r i v e d f r o m t h e e r o s i o n o f a g r e a t t h i c k n e s s o f l i m e s t o n e o r f r o m a l i m e s t o n e v e r y r i c h i n c h e r t ( s u c h as t h e Rundle f o r m a t i o n o f M i s s i s s i p p i a n a g e ) . The f o l l o w i n g e x p l a n a t i o n s have been o f f e r e d . ( a ) The f i r s t and commonly a c c e p t e d i d e a i s t h a t the C r e t a c e o u s r o c k s up t o l a n c e t i m e were d e r i v e d e n t i r e l y f r om the e r o s i o n o f t h e ne w l y u p l i f t e d P u r c e l l and S e l k i r k moun-t a i n s and were l a i d down i n a seaway s t r e t c h i n g e a s t w a r d f r o m 1 . t h e T r e n c h . W i l l i a m s has e s t i m a t e d t h a t 18,000 f e e t o f 1 W i l l l a m s , M. Y. B u l l v S e o l . S o c . A m . , V o l . 4 3 , 1932, p.998* e r o s i o n f rom t h e P u r c e l l and S e l k i r k mountains was n e c e s s a r y t o s u p p l y t h e m a t e r i a l f o r the Upper C r e t a c e o u s o f the P l a i n s . As t h e l o w e r C r e t a c e o u s i s e q u a l l y t h i c k a t l e a s t 36,000 f e e t o f s e d i m e n t s must have been e r o d e d f r o m the J u r a s s i d e moun-t a i n s i n C r e t a c e o u s t i m e s . The g r e a t d e p t h o f e r o s i o n i n d i c a t e s t h a t g r e a t t h i c k n e s s e s o f P a l a e o z o i c o r e a r l y M e s o z o i c s t r a t a must have been d e p o s i t e d i n t h e s i t e o f the J u r a s s i d e m o u n t a i n s . I n t h i s e x p l a n a t i o n the M e s o z o i c s e d i m e n t s a r e supposed t o have - 2 7 - •••••• • ' been d e p o s i t e d as f a r westward as the T r e n c h . ( b ) An a l t e r n a t i v e i d e a i s t h a t , s i n c e C r e t a c e o u s s e d i -ments a r e n o t f o u n d i n t h e b e l t between t h e a x e s o f t h e S e l k i r k and Rocky m o u n t a i n s , t h e y were not d e p o s i t e d i n t h i s a r e a . The b e l t between t h e T r e n c h and the p r e s e n t axes of t h e R o c k i e s t h e n , was a l o w l a n d a c r o s s w h i c h g r e a t r i v e r s t r a n s -p o r t e d the s e d i m e n t s f r o m th e J u r a s s i d e m ountains on t h e west t o t h e g e o s y n c l i n e on the e a s t . T h i s assumes t h a t t h e w e s t e r n p a r t o f the R o c k i e s n e v e r sank t o s e a - l e v e l a f t e r t h e u p r i s e a t the c l o s e o f the P a l a e o z o i c . T h i s a r e a had l i t t l e r e l i e f and so p r o b a b l y underwent l i t t l e e r o s i o n , a l t h o u g h the c h e r t y c o n -g l o m e r a t e may have been d e r i v e d f rom the e r o s i o n o f p a r t o f the Rundle l i m e s t o n e f r o m t h i s b e l t . These g r e a t r i v e r s were a b l e t o m a i n t a i n f o r a l o n g t i m e t h e i r c o u r s e s a c r o s s t h e s i o w l y r i s i n g Rocky mountains as t h e i r v a l l e y s f o rm the p a s s e s t h r o u g h the R o c k i e s . S e d iments o f Lance and F o r t U n i o n time were d e r i v e d , i n p a r t , f r o m t h e J u r a s s i d e mountains and, i n p a r t , from t h e • • • A • ' 1 r i s i n g Rocky m o u n t a i n s . 1 W i l l i a m s , M.Y. B u l l . G e o l . S o c . A m . , V o l . 4 2 , p.998. 2 ( c ) Raymond b e l i e v e s t h a t d u r i n g P a l a e o z o i c t i m e s t h e z Raymond, P.E. and W i l l a r d , B. J o u r , o f G e o l . , V ol . 3 9 » 195TT 107. r e g i o n now o c c u p i e d by the J u r a s s i d e mountains was, e x c e p t i n g M i s s i s s i p p i a n t i m e s , p r o b a b l y a l a n d mass f r o m the l a t e P r e -Cambrian t o the T r i a s s i c . T h i s e x p l a i n s the p r e s e n t e x t e n t o f the P a l a e o z o i c s e d i m e n t s v e r y n i c e l y but b r i n g s up a g a i n the • -28.- . p r o b l e m o f f i n d i n g a s o u r c e f o r t h e M e s o z o i c s e d i m e n t s o f the R o c k i e s and th e P l a i n s . I t n e c e s s i t a t e s t h e e r o s i o n o f 36,000 f e e t o f B e l t i a n and M i s s i s s i p p i a n s e d i m e n t s f r o m t h e S e l k i r k and P u r c e l l m o u n t a i n s . T h i s f i g u r e i s n ot e x c e s s i v e i f D a l y * s^ * f i g u r e o f 61,150 f e e t o f Pre - C a m b r i a n s t r a t a l a i d 2 • down i n t h e S e l k i r k s i s o f any s i g n i f i c a n c e . 1 D a l y , R.A. G.S.C. Mem.68, .1915, P« ! ~~ " ~ 2 Note. D a l y ' s P r e - C a m b r i a n has s i n c e been p r o v e d t o i n c l u d e some C a r b o n i f e r o u s f o r m a t i o n s but t h i s does not n e c e s s a r i l y t a k e away i t s s i g n i f i c a n c e as a measure o f the t o t a l s e d i -ments d e p o s i t e d . | T h i s means t h a t the M e s o z o i c f o r m a t i o n s o f t h e E a s t e r n R o c k i e s and the P l a i n s were d e r i v e d f rom the e r o s i o n o f the. B e l t i a n s e d i m e n t s f r o m the J u r a s s i d e m o u n t a i n s . The c h e r t y c o n g l o m e r a t e , i n t h i s case , must have come from the Rundie l i m e s t o n e o f the w e s t e r n R o c k i e s and perhaps t h a t o f the P u r -c e l l s and S e l k i r k s . The p r e s e n t westward l i m i t s o f the P a l a e o z o i c and M e s o z o i c r a t h e r s u p p o r t t h i s t h i r d po s t u l a t i o n . ( d ) D o w l i n g b e l i e v e d t h a t , as t h e C e n t r a l B e l t o f t h e R o c k i e s had undergone so much g r e a t e r e r o s i o n t h a n t h e E a s t e r n B e l t , i t i n d i c a t e d an e a r l i e r age f o r t h e w e s t e r n and c e n t r a l R o c k i e s . A t f i r s t , t h i s seems h i g h l y p l a u s i b l e when one con-s i d e r s t h a t , a l o n g t h e a x i s o f t h e m o u n t a i n s , e r o s i o n has exposed the P r e - C a m b r i a n ; but to t h e e a s t the C r e t a c e o u s has not y e t been removed. D o w l i n g a c c o u n t e d f o r t h e e a r l i e r up-l i f t i n the west by a normal f a u l t w i t h a downthrow o f 30,000 f e e t t o the e a s t , t h i s f a u l t f o r m i n g t h e boundary between the two a r e a s . Study o f the s t r u c t u r e s e c t i o n s does not r e v e a l any such f a u l t hut shows t h a t the R o c k i e s were b u i l t as a u n i t . N o r t h o f t h e A t h a b a s c a P r e - C a m b r i a n s t r a t a c o n t i n u e t o occupy the a x i s o f the s y s t e m ; h e r e the o l d e r r o c k s a r e d e f i n i t e l y exposed because o f g r e a t e r e r o s i o n a t t h e h i g h e r a l t i t u d e s . C o n c l u s i o n s . (1) The o r i g i n o f t h e M e s o z o i c s e d i m e n t s i s s t i l l u n s o l v e d . ( 2 ) The b u l k o f s e d i m e n t s were d e r i v e d f r o m g r e a t t h i c k n e s s e s o f B e l t i a n o r P a l a e o z o i c f o r m a t i o n s d e p o s i t e d i n the s i t e o f t h e S e l k i r k and P u r c e l l m o u n t a i n s . O ) The a r e a t o t h e west o f t h e T r e n c h must have been above s e a - l e v e l f o r a l o n g t i m e b e f o r e m o u n t a i n -. b u i l d i n g a t the c l o s e o f the J u r a s s i c . (4) These mountains must have undergone r e p e a t e d v e r t i c a l u p l i f t s , (j?) The w e s t e r n b e l t o f t h e R o c k i e s p r o b a b l y e x i s t e d a s a l o w l a n d f r o m t h e upwarp a t the c l o s e o f t h e P a l a e o z o i c . ( 6 ) Rocky m o u n t a i n s t r u c t u r e i n d i c a t e s t h a t t h e s y s t e m was b u i l t as a u n i t • IV. The m i g r a t i o n o f the g e o s y n c l i n e . We have seen t h a t the g r e a t e s t t h i c k n e s s e s o f s t r a t a l a i d down i n t h e v a r i o u s e r a s do not c o i n c i d e but t h e r e i s a p r o g r e s s i v e e a s t w a r d s h i f t i n g of the s i t e s o f g r e a t e s t d e p o s i -t i o n . The f o l l o w i n g t a b l e i l l u s t r a t e s t h i s e a s t w a r d m i g r a t i o n - 5 0 -o f the G o r d i l l e r a n g e o s y n c l i n e . •Table 1 . I r a . S i t e o f d e - p o s i t i o n o f the g r e a t e s t t h i c k -n e s s e s o f s e d i m e n t s . S i t e o f o r i g i n o f s e d i m e n t s . P r e - C a m b r i a n ( B e l t i a n ) S e l k i r k and P a r c e l 1 m o u n t a i n s O l d l a n d mass C a s c a d i a whose e a s t e r n b o r d e r was n e a r the Arrow l a k e s . P a l a e o z o i c W e s t e r n and c e n t r a l B e l t s o f the Rocky m o u n t a i n s . C a s c a d i a and p o s s i b l y p a r t o f the S e l k i r k -P u r c e l l a r e a . M e s o z o i c E a s t e r n B e l t o f t h e Rocky mountains P u r c e l l - S e l k i r k a r e a w i t h po s s i b l y a s m a l l p o r t i o n o r i g i n a t i n g i n the Western B e l t o f t h e R o c k i e s . T e r t i a r y A l b e r t a g e o s y n c l i n e i m m e d i a t e l y e a s t o f the F o o t h i l l s . The Rocky mountains T h i s m i g r a t i o n has c o n t i n u e d f rom P r e - C a m b r i a n t i m e s to t h e p r e s e n t . As the r a n g e s , C a s c a d i a , t h e S e l k i r k s and the R o c k i e s were b u i l t p r o g r e s s i v e l y e a s t w a r d , t h e g e o s y n c l i n a l t r o u g h has l a i n a l o n g the e a s t e r n b o r d e r o f the newly formed 1 m o u n t a i n s . P l a t e 3 (page 30: a f t e r L i n k " ) i l l u s t r a t e s t h i s 1 L i n k , T.A. B u l l . A m . A s s o c . P e t . G e o l . , V o l . 1 5 , No.5, 1931, p.505* i d e a v e r y w e l l . Grabau has " d e s c r i b e d s i m i l a r m i g r a t i o n s o~f TGrabau. A.W. BuTTTGeol.Soc.Am.,"Vol.3 0 , 1929, p . » 7 »" "~T g e o s y n c l i n e s c o n n e c t e d w i t h o t h e r g r e a t mountain ranges : (1) The M o l a s s e c h a n n e l , formed w i t h t h e f i r s t f o l d i n g -31-o f the A l p s . (2) The g e o s y n c l i n e a l o n g the o u t e r b o r d e r o f t h e newly formed C a r p a t h i a n s . (3) The l a t e T e r t i a r y g e o s y n c l i n e n o r t h o f the Caucasus. I n s o f a r as one can judge f r o m a v a i l a b l e d a t a a s i m i l a r g e o s y n -c l i n e b e l t o c c u r r e d on the f i r s t e l e v a t i o n o f (4) The A t l a s mountains o f n o r t h A f r i c a . (5) The Andes o f S o u t h A m e r i c a . I n a l l t h e s e r e g i o n s t h e r e i s e s s e n t i a l c o n c o r d a n c e o f s t r a t a , though d i s c o n f o r m i t i e s e x i s t . These b r e a k s a r e f o u n d where l a t e r o v e r l a p b r i n g s the younger f o r m a t i o n s to r e s t on the eroded p a r t s o f the f o l d e d s e r i e s , e.g. the o v e r l a p o f t h e Devonian on the B e l t i a n on the e a s t e r n f l a n k o f the P u r c e l l r a n g e . V. T o t a l t h i c k n e s s e s f o r s t r a t a d e p o s i t e d i n v a r i o u s p a r t s o f  t h e G e o s y n c l i n e . Because the maximum t h i c k n e s s e s o f the d i f f e r e n t f o r m a t i o n s a r e not c o i n c i d e n t , composite s e c t i o n s , g i v i n g t h e t o t a l t h i c k n e s s o f s e d i m e n t s d e p o s i t e d , are o f t e n i n a c c u r a t e . As the base o f t h e B e l t i a n i s nowhere exposed the depth to the bottom o f the C o r d i l l e r a n g e o s y n c l i n e i s not known. N e v e r t h e -l e s s the f o l l o w i n g f i g u r e s g i v e a good i d e a o f t h e o r d e r o f the t h i c k n e s s o f s e d i m e n t s i n v o l v e d i n the b u i l d i n g o f t h e R o c k i e s . . 1 • Warren has computed t h a t , n e a r the 31st p a r a l l e l o f I Warren, P.S. C a n T F i e l d N a t u r a l i s t , V o l . 4 3 , 192?, PP» 2 3°2T~ l a t i t u d e , 53 ,000 f e e t o f s e d i m e n t s ( i n c l u d i n g 6000 f e e t o f . • • - 3 2 - ' B e l t i a n s t r a t a ) were l a i d down i n t h e Rocky mou n t a i n geosyn-c l i n e . D a l y 1 r e p o r t e d 61,000 f e e t o f B e l t i a n i n t h e S e l k i r k s "1 D a l y , R.A. G.S.C. Mem.bo1, 19137 to the west o f the R o c k i e s . T h i s has s i n c e been shown t o i n -c l u d e some P a l a e o z o i c s . I f t h e B e l t i a n t r o u g h d i d not s h a l l o w r a p i d l y t o the e a s t y t h i s would g i v e us a t h i c k n e s s o f a p p r o x -i m a t e l y 100,000 f e e t o r 20 m i l e s o f s e d i m e n t s i n the Rocky mountain g e o s y n c l i n e . But i t i s f a r more p r o b a b l e t h a t the B e l t i a n g e o s y n c l i n e , l i k e i t s s u c c e s s o r s , w a s d e c i d e d l y asym~ m e t r i c a l , w i t h t h e s i t e o f g r e a t e s t d e p o s i t i o n i n t h e S e l k i r k s and t h a t i t t h i n n e d c o n s i d e r a b l y t o the e a s t i n the s i t e o f the R o c k i e s . N e v e r t h e l e s s , t h i s tremendous f i g u r e i s w i t h i n the bounds o f p o s s i b i l i t y . As P l a t e I I I , page 3 0 , shows, t h e C o r d i l l e r a n geo-s y n c l i n e s have a l l been d e c i d e d l y a s y m m e t r i c a l w i t h t h e s i t e s o f g r e a t e s t d e p o s i t i o n n e a r t h e i r w e s t e r n b o r d e r s . Composite s e c t i o n s a l s o show c o n s i d e r a b l e s h a l l o w i n g to the n o r t h . ( a ) V a r i a t i o n s i n t h i c k n e s s o f s t r a t a i n s e c t i o n s  n o r m a l t o the a x i s o f the g e o s y n c l i n e . The P a l a e o z o i c s e d i -mentary sheet , w h i c h amounts t o o n l y a few hundred f e e t n e a r the edge of the S h i e l d , i n c r e a s e s t o 47»0Q0 f e e t ( a p p r o x i m a t e l y 9 m i l e s ) i n the c e n t r e o f the Rocky mount a i n s . The M e s o z o i c s e d i m e n t s . r e p r e s e n t e d by a few hund r e d f e e t a l o n g the A t h a b a s c a and McMurray r i v e r s i n n o r t h e a s t e r n A l b e r t a , i n c r e a s e t o over 12,000 f e e t i n the B a n f f a r e a . S i m i l a r l y the T e r t i a r y beds t h i c k e n westward f o r , i n the p r e s e n t A l b e r t a g e o s y n c l i n e , the a x i s o r deepest p a r t l i e s w i t h i n 2-|- m i l e s o f i t s w e s t e r n - 3 3 -border at the "base of the F o o t h i l l s . An important c h a r a c t e r i s t i c of these geosynclines i s that t h e i r axes are close to t h e i r western borders and the o l d land masses from which the sediments were d e r i v e d . The same p r i n c i p l e can probably be a p p l i e d to g e o s y n c l i n e s i n g e n e r a l . F i g u r e 1 i l l u s t r a t e s d i a g r a m m a t i c a l l y the supposed shape and p o s i t i o n of the v a r i o u s C o r d i l l e r a n g e o s y n c l i n e s . (b) V a r i a t i o n s i n t h i c k n e s s e s of s t r a t a deposited along the a x i s of the g e o s y n c l i n e . The sedimentary sheet a l s o shows v a r i a t i o n s i n t h i c k n e s s a l o n g i t s a x i s . From the t h i c k e n i n g and t h i n n i n g of i n d i v i d u a l formations and from composite s e c t i o n s , i t appears t h a t the geosyncline was deepest between the Crowsnest and the A t h a b a s c a . To the south i t t h i n s somewhat i n Montana w h i l e to the north there i s a gradu-a l decrease to the Mackenzie mountains. The f o l l o w i n g com-p o s i t e s e c t i o n s i l l u s t r a t e t h i s . -34-Table 2. l o c a t i o n T o t a l Thickness Thickness of Pre-Cambrian sediments i n c l u d e d . Montana 1 37 ,000 f e e t 10,000 f e e t 51st P a r a l l e l 2 52,900 '» 6,000 " Peace R i v e r 3 22,000 » none Mackenzie Mts. 4 ( F r a n k l i n Range) 7,700 !• 375 1 Bevan, A. Bull.Geol.Soc.Am., Vol.40, 1929, p.434. 2 Warren, P.S. Can.FieId N a t u r a l i s t , Vol.43, 1929, pp.23-27. 3 P.G.E. Resources Survey Report No.2, p . 6 5 1 . 4 . W i l l i a m s , M.Y. Bull.Geol.Soc.Am., Vol.35, 1924, p.457. In the n o r t h the sediments were deposited not i n a narrow deep geosyncline but r a t h e r i n one of f a i r l y uniform depth. As the type and t h i c k n e s s of s t r a t a determine to a l a r g e extent the type of s t r u c t u r e r e s u l t i n g when f a i l u r e occurs under orogenic s t r e s s , we w i l l expect to f i n d a d i f f e r e n t type of mountain s t r u c t u r e a r i s i n g from the n o r t h e r n u n i f o r m l y shallow part of the g e o s y n c l i n e than from the deep asymmetrical trough of the southern p o r t i o n . VI. The Age of Mountain B u i l d i n g . In the mountains the o l d e s t sediments not i n v o l v e d i n the orogenic movements are of l a t e Eocene age. They are found i n the F l a t h e a d and F i n d l a y v a l l e y s and at Norman on the Mackenzie. Since the Upper Cretaceous have been caught up i n the mountain f o l d s t h i s l i m i t s the p e r i o d of mountain-building as post-Upper Cretaceous and p r e - l a t e Eocene. -25-S e v e r a l w r i t e r s have b e l i e v e d t h a t the n o r t h e r n mountains were e a r l i e r i n o r i g i n t h a n the R o c k i e s b u t t h e y can o n l y be l i m i t e d by the s e d i m e n t a r y e v i d e n c e as b e l o n g i n g t o t h e same p e r i o d as do t h e R o c k i e s to t h e s o u t h . S i n c e t h e l o w e r C r e t a c e o u s i n t h e n o r t h i s p a r t l y marine w h i l e t h a t o f t h e s o u t h , c o n t i n e n t a l , i t would seem t h a t the f o r e r u n n e r s o f the orogeny were f e l t l a t e r i n the n o r t h . F o r a complete d i s c u s s i o n o f t h e age o f m o u n t a i n b u i l d i n g t h e r e a d e r i s r e f e r r e d t o "The H i s t o r i c a l and S t r u c t u r a l Geology o f the Southernmost Rocky M o u n t a i n s i n 1 Canada" by J.D. M a c k e n z i e . 1 T.R.STC. V o l . X V I , T 9 2 2 T P P « 9 9 - l Q f e T "-36- ' C h a p t e r I I I . THE STRUCTURE OF THE EASTERN CORDILLERA Because o f the g r e a t g a p s , u n e x p l o r e d and unmapped, i t i s d i f f i c u l t , i n d e s c r i b i n g the s t r u c t u r e s o f so l a r g e an a r e a , t o a r r a n g e the m a t e r i a l t o emphasize the c h a r a c t e r i s t i c s o f the v a r i o u s s t r u c t u r a l p r o v i n c e s . I n t h i s c h a p t e r , f i v e such p r o v i n c e s a re d i s c u s s e d i n the f o l l o w i n g s e c t i o n s : S e c t i o n I - The S e l k i r k - P u r c e l l Ranges. S e c t i o n I I - The Rocky M o u n t a i n T r e n c h . S e c t i o n I I I - The Rocky m o u n t a i n s p r o p e r and the F o o t h i l l s S e c t i o n I V - The N o r t h e r n Ranges. S e c t i o n V - The A l b e r t a G e o s y n c l i n e . As has been p r e v i o u s l y m e n t i o n e d , t h e S e l k i r k - P u r c e l l r a n g e s do not b e l o n g i n t h e E a s t e r n system but were formed e a r l i e r d u r i n g t h e J u r a s s i d e R e v o l u t i o n . But a s , i n p l a c e s , Rocky mountain s t r u c t u r e e x t e n d s a c r o s s t h e Trench i n t o the P u r c e l l s and a l s o P u r c e l l s t r u c t u r e " e x t e n d s i n one l o c a l i t y i n t o t h e R o c k i e s t h e y a r e d e s c r i b e d h e r e i n t o b r i n g out t h e r e l a t i o n -s h i p o f t h e ranges t o each o t h e r and t o t h e Rocky M o u n t a i n T r e n c h . The Rocky mountains are d i v i d e d i n t o t h r e e b e l t s on the b a s i s o f s t r u c t u r e . They a r e (1) The e a s t e r n b e l t of o v e r t h r u s t s and c l o s e f o l d i n g . (2) The c e n t r a l b e l t o f open f o l d i n g and normal f a u l t i n g . (3) The n a r r o w e r w e s t e r n b e l t o f c l o s e f o l d i n g and o v e r -t h r u s t s . The a r e a s a r e d e s c r i b e d t o emphasize t h e s e c h a r a c t e r i s t i c s but • • - 3 7 -wherever a s t r u c t u r e s e c t i o n has "been worked out a c r o s s the R o c k i e s , as a l o n g t h e 4 9 t h p a r a l l e l and t h e C.P.R., t h i s i s d e s c r i b e d t o b r i n g out t h e r e l a t i o n s h i p o f the b e l t s t o one a n o t h e r , , S e c t i o n I . THE SELKIRKrPURCELL RANGES. The s o u t h e r n p a r t o f the P u r c e l l range i s a g r e a t a r c h o r a n t i c l i n e p l u n g i n g n o r t h o r n o r t h e a s t w i t h the o l d e r f o r m a t i o n s e x p o s e d i n the h e a r t o f t h e range t o t h e s o u t h and s u c c e s s i v e l y y o u n g e r f o r m a t i o n s o c c u p y i n g t h a t p o s i t i o n t o the n o r t h . S t r u c t u r e - C r a n b r o o k Map A r e a . I n the P u r c e l l range f o l d s , f a u l t s , f i s s u r e s and j o i n t s a r e v e r y abundant. "The f o l d s have a g e n e r a l n o r t h -s o u t h t r e n d . To add t o the c o m p l e x i t y , t h e f a u l t s a r e p r o b a b l y o f two a g e s , p o s t - J u r a s s i c and p o s t - C r e t a c e o u s ( L a r a m i d e ) . " 1 S c h o f i e l d , S77. G.S.C. Mem .7b, p.927 The f o l d s a r e g e n e r a l l y s i m p l e i n c h a r a c t e r and r e s u l t from c o m p r e s s i v e s t r e s s e s a c t i n g i n an e a s t - w e s t d i r e c t i o n . I n -c l i n e d c l o s e f o l d i n g and t h r u s t i n g t o w a r d s t h e Trench are not c h a r a c t e r i s t i c o f the e a s t e r n f l a n k o f the P u r c e l l s i n t h i s a r e a but s e v e r a l h i g h - a n g l e d t h r u s t s have been mapped. Scho-2 f i e l d b e l i e v e d t h a t most o f the f a u l t i n g was normal and r e s u l t e d f r o m t e n s i o n on the r e l i e f o f s t r e s s e s . I + - f CD © 1-1 SH CD - P OS 0* O •H co CO g id CO o CD < H •H P) o ,0 Jh a! o I o Pi o t> CD p ca •H &> & cd o CD u 03 CD +» 03 Ci5 a o •H 0) 43 H s4 a O H 0) o 01 CD 0) . d •H CO CO O o CO U 0) Pi fcl t>3 +» 0) nd Pi •H u P< •H •rH u rH •H rH o PH CO W o -4 Fault Syncl Ant i c Line w • <« M PH CD 05 N H o P4 o Pi pq 9 M o CD •H «M O J* o CO u <D - P <rH ca CO (-« o fa CD a •rH rH © Pi CO >s 03 Jh > rH rH •H c3 o CD a «H rH O •H +=> Pi 03 Jh CD > •H <£ +=» o P CD Pi CD •H Pi rH •rH O r H •rH O Pi >s cd M CQ 03 pq - 3 8 -G e n e r a l d e s c r i p t i o n o f s t r u c t u r e . The s t r u c t u r e o f the r e g i o n i s shown on P l a t e IV, page 38, and F i g . 2. The most w e s t e r l y mountains o f t h e P u r -c e l l g r o u p , the Moyie range i s a s i m p l e and e a s t e r l y - d i p p i n g m o n o c l i n e . T h i s i s c u t o f f on the e a s t by the Moyie f a u l t w i t h the downthrow t o t h e e a s t . The Yahk a n t i c l i n e t o t h e e a s t i s the c o n t r o l l i n g s t r u c t u r e o f the Yahk r a n g e . A l o n g the I n t e r n a t i o n a l Boundary t h i s i s f o l l o w e d on t h e e a s t by the Yahk s y n c l i n e and a s m a l l e r a n t i c l i n e . The M c G i l l v r a y range i s e s s e n t i a l l y a s h a l l o w s y n -c l i n e and i s c u t o f f on the e a s t by the C r a n b r o o k f a u l t . U n d e r l y i n g t h e K o o t e n a y v a l l e y i s a m o n o c l i n e bounded on t h e west by the C r anbrook f a u l t and on the e a s t by t h e f a u l t d e s c r i b e d by D a l y as a n o r m al f a u l t . T h i s f a u l t b l o c k c o n t a i n s the C a r b o n i f e r o u s l i m e s t o n e , the youngest s e d i m e n t a r y f o r m a t i o n i n the d i s t r i c t . F i g . 2 S c a l e 1" s 8 m i . ( F o r l e g e n d and l o c a t i o n o f s e c t i o n , see P l a t e IV.) The Goat r i v e r a n t i c l i n e e x t e n d s n o r t h o f K i t c h e n e r . I t i s one o f the s e v e r a l s m a l l n o r t h p l u n g i n g a n t i c l i n e s c h a r a c t e r -i s t i c o f the r e g i o n . G e a n t i c l i n a l s t r u c t u r e becomes more pronounced t o the n o r t h i n the v i c i n i t y of S t . Mary r i v e r . The huge a n t i c l i n e w i t h n o r t h e r l y s t r i k e i s m o d i f i e d by overturned a n t i c l i n e , smashed and f a u l t e d . T h i s i s very s i m i l a r to the s t r u c t u r e i n the Windermere area to the n o r t h . F a u l t s . A f t e r the f o l d i n g the P u r c e l l range was a f f e c t e d by f a u l t i n g . I n the Cranbrook area f a u l t i n g f o l l o w e d two systems -( l ) a northeast-southwest system, e.g. M a r y s v i l l e and Moyie f a u l t s . (2.) a northwest-southeast system, e.g. the Cranbrook f a u l t . The M a r y s v i l l e f a u l t , as shown i n P l a t e IV, page 38, s t r i k e s due west from the Kootenay v a l l e y to M a r y s v i l l e . Here there i s a t u r n i n the s t r i k e to the southwest which c a r r i e s the f a u l t to the headwaters o f Goat r i v e r . I n the e a s t e r n part the younger K i t c h e n e r and Creston formations are downthrown w i t h respect to the o l d e r A l d r i d g e q u a r t z i t e . . To the west the f a u l t i s not w e l l d e f i n e d but apparently two p a r a l l e l f a u l t s s t r i k e northwest from the headwaters of Goat r i v e r . The block of the K i t c h e n e r f o r m a t i o n between these f a u l t s i s downthrown w i t h respect to both the A l d r i d g e f o r m a t i o n to the northeast and the Creston f o r m a t i o n to the southwest. One of these n o r t h -w e s t e r l y f a u l t s i s cut by a small g r a n i t i c stock. The Moyie f a u l t s t r i k e s southwest from 1 mile south of Steele,, crosses the Moyie r i v e r at the n o r t h e r n end of Moyie l a k e s and continues i n i t s general southwesterly t r e n d to c r o s s the -40- • I n t e r n a t i o n a l Boundary a t Moyie r i v e r . A g a i n , as i n the M a r y s v i l l e f a u l t , the downthrow i s t o the s o u t h and e a s t , "bringing the o l d e r A l d r i d g e and C r e s t o n f o r m a t i o n s on the n o r t h i n c o n t a c t w i t h the y o u n g e r , C r e s t o n , K i t c h e n e r and S i y e h on the s o u t h . The C r a n b r o o k f a u l t f o l l o w s the v a l l e y o f G o l d c r e e k and has "been t r a c e d by S c h o f i e l d f rom the I n t e r n a t i o n a l Boundary t o a p o i n t 8 m i l e s s o u t h o f Cranbrook"'". T h i s f a u l t s t r i k e s 1 S c h o f i e l d , S..J. o p . c i t . , p.fti>» ~~~ ~~~~ n o r t h w e s t p a r a l l e l i n g the s t r u c t u r a l t r e n d o f t h e R o c k i e s . The downthrow s i d e i s on the w e s t . The S i y e h , w i t h the P u r e e 1 1 l a v a s and the o v e r l y i n g Gateway f o r m a t i o n , o u t c r o p on b o t h s i d e s o f the f a u l t . Age o f f a u l t i n g . I n the P u r e e l l range t h e C a r b o n i f e r o u s f o r m a t i o n s are f a u l t e d and the P l e i s t o c e n e f o r m a t i o n s u n a f f e c t e d . The f o l d i n g t o o k p l a c e b e f o r e the f a u l t i n g . I n the Cranbrook a r e a the s m a l l i g n e o u s i n t r u s i o n s a r e 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 o f the N e l s o n b a t h o l i t h . These i n t r u s i v e s are a s s o c i a t e d w i t h the n o r t h e a s t - s o u t h w e s t system o f f a u l t i n g , and cut the f a u l t s but a r e t h e m s e l v e s u n a f f e c t e d . Then, as b o t h the f o l d i n g and i n t r u s i o n a r e c o n s i d e r e d t o be J u r a s s i c , the f a u l t i n g , s i n c e i t f o l l o w e d t h e f o l d i n g and p r e c e d e d the i n t r u -s i o n , i s a l s o o f J u r a s s i c age. The n o r t h w e s t - s o u t h e a s t s y s t e m o f f a u l t i n g i s r e p r e s e n t e d i n t h i s a r e a by the Cranbrook f a u l t . S i n c e i t has the Rocky mountain t r e n d and i s g e n e t i c a l l y a s s o c i a t e d w i t h the Rocky Mountain Trench, i t i s gi v e n a laramide age by 1 S c h o f i e l d . T S c h o f i e l d , S.J. G.S.C. Mem.7b, p . 9 5 . ~ S t r u c t u r e - Windermere Map Area. Here the P u r c e l l g e a n t i c l i n e i s made up of s e v e r a l major f o l d s . The formations on the east side of the range plunge northeast under the f l o o r of the Rocky Mountain Trench while those along the western boundary d i p away towards the southeast. F i g * } - Toby conglomerate. @ (F o r l i n e of s e c t i o n see P l a t e V.) The general axes of f o l d i n g t rend northwest-southeast. These major f o l d s are tr a n s v e r s e d at r i g h t angles by minor f o l d s which give , as a r e s u l t , northwest and southeast p i t c h e s to the l a r g e r s t r u c t u r e s . Three a n t i c l i n e s w i t h i n t e r -vening s y n c l i n e s are found i n the Windermere map area ( P l a t e V, page 4 1 ) . These are i l l u s t r a t e d diagrarnrnatically i n F i g . 3 . The mo st e a s t e r l y of these a n t i c l i n e s borders the Rocky Mountain Trench and has a sharp o v e r t u r n to the northeast i n the v i c i n i t y of Lake Windermere. This o v e r t u r n f l a t t e n s out to the n o r t h -e a s t , f o r , at Law and Slade oreeks the s t r a t a are d i p p i n g g e n t l y under the Trench."^ 1 Walker7~J.F. G.S.C. Mem.148, p.39. " U p l i f t s producing open f o l d i n g occurred at the c l o s e ^X:C.:-:^''\i-.'--: • • 2 " of P u r c e l l and probably Windermere time. S c h o f i e l d dates the 2 S c h o f i e l d , S.J. G.S.C. Mem.7b, pp»93» 97, 102. the b u i l d i n g of the P u r c e l l range and the r e s u l t a n t intense 3 f o l d i n g as l a t e J u r a s s i c . This i s s u b s t a n t i a t e d by Drysdale 3 Drysdale, C.W. G.S.C. Mem.5fa, pp.61,62. who g i v e s a s i m i l a r age f o r the b a t h o l i t h i c i n t r u s i o n i n the adjacent S e l k i r k range. As shown i n F i g . 3 i t i s c l e a r that the f o l d i n g and f a u l t i n g took place before the i n t r u s i o n of the g r a n i t e s t o c k s . But, t h a t some d i f f e r e n t i a l s t r e s s s t i l l e x i s t e d a f t e r the i n t r u s i o n , i s shown by the shearing of the l a t e r lamprophyre dykes and mineral v e i n s of the r e g i o n . Whether these s m a l l e r movements were due" to the J u r a s s i c mountain-building or to the l a t e r Laramide R e v o l u t i o n i s not known. Apparently the l a t t e r orogenic p e r i o d caused u p l i f t w ithout f o l d i n g i n t h i s part of the P u r e e l I s . Rocky Mountain Trench. The Rocky Mountain Trench i n t h i s area has no true border f a u l t s . The Pre-Cambrian formations on the west side of the Trench are overturned and plunge to the northeast. In se v e r a l l o c a l i t i e s they are exposed on the east side of the Trench i n the S t a n f o r d range and are f o l d e d and f a u l t e d w i t h the P a l a e o z o i c formations outcropping t h e r e . Ho border f a u l t -i n g of any note i s found along the west s i d e of the Trench i n the Windermere map area. The s t r a t a o f the S t a n f o r d range are h i g h l y f o l d e d and overturned to the west. These f o l d s a r e , i n most cases, broken by f a u l t s undoubtedly a s s o c i a t e d w i t h the Laramide R e v o l u t i o n . South to Skookumchuck creek the Pre-Cambrian forma-t i o n s on the west s i d e continue to plunge beneath the v a l l e y f l o o r and i n places outcrop along the east side o f the Trench. Here again the re i s no apparent border f a u l t along the west side of the Trench. The s t r u c t u r e s i n the S t a n f o r d range i n -t h i s s e c t i o n are much s i m p l e r than those to the n o r t h i n the Windermere area. The s t r a t a i s no t n e a r l y so c l o s e - f o l d e d or f a u l t e d . The o v e r t u r n i n g to the west, o c c u r r i n g i n the n o r t h , has changed to open f o l d i n g w i t h g e n t l e e a s t e r l y d i p s and steeper w e s t e r l y d i p s . The western limbs of the f o l d s are s l i g h t l y broken. The f i r s t border f a u l t of any note l i e s along Sheep creek and probably connects w i t h the great f a u l t extending from W i l d Horse creek to B u l l r i v e r . I n i t s northern p o r t i o n between Sheep creek and W i l d Horse creek i t s displacement i s s m a l l , f o r the formations on the east s i d e o f the Trench t u r n over to conform w i t h those on the west side without any l a r g e displacement. F u r t h e r south the displacement i n c r e a s e s , f o r , i n the v i c i n i t y of B u l l r i v e r , t h i s f a u l t has the g r e a t e s t 1 displacement of any known i n the Rockies. "I S c h o f i e l d , S.J. Trans.Roy. Soc. Can. , Sec.IV, 19^0, pp.75 ,7bT" • -44- ' ' There i s no d e f i n i t e system of upthrow or downthrow i n the S t a n f o r d range i n the Windermere map area. Summary - S e c t i o n I : P u r o e l l and S e l k i r k ranges. Several other areas i n these ranges w i l l be de s c r i b e d i n connection w i t h the Rocky Mountain Trench and the s e c t i o n along the CP.R.. The outstanding c h a r a c t e r i s t i c s o f these ranges are (1) Defamation took place i n the order ( 1 . F o l d i n g (a) J u r a s s i d e ( 2.. F a u l t i n g R e v o l u t i o n ( 3 . Igneous i n t r u s i o n ( 4 . U p l i f t (b) laramide ( F a u l t i n g R e v o l u t i o n ( U p l i f t (2) There i s a s i m i l a r i t y between the c e n t r a l and e a s t e r n b e l t s of the P u r c e l l and Rocky mountain s t r u c t u r e s although the s t r u c t u r e s are not n e a r l y so pronounced i n the J u r a s s i d e mountains; (a) the c e n t r a l b e l t of the P u r c e l l s i s c h a r a c t e r -i z e d by open f o l d i n g and normal f a u l t i n g . (b) the eastern b e l t of the P u r c e l l s i s i n places c l o s e f o l d e d , overturned and overthrust towards the e a s t , i . e . towards the Trench. (3) The deforming s t r e s s e s of the laramide r e v o l u t i o n acted across the Trench producing the northwest trending f a u l t system, e.g. the Cranbrook f a u l t . S e c t i o n I I . STRUCTURE OF THE ROCKY MOUNTAIN TRENCH. The s t r u c t u r e of the Trench i s extremely complicated and v a r i e d . Any theory as t o i t s o r i g i n must he i n accordance wi t h a l l the d i f f e r e n t types of g e o l o g i c a l s t r u c t u r e found t h e r e i n . As the v a l l e y i s a c c e s s i b l e and of uniform e l e v a t i o n i t has formed an important route of t r a v e l , f i r s t f o r the e x p l o r e r s and now f o r the r a i l w a y s . Although much g e o l o g i c a l work has been done on the Trench l i t t l e i s known of i t s general s t r u c t u r e . The f l o o r and lower f l a n k s are covered by g l a c i a l debris and make a comprehensive study o f these p a r t s imposs-i b l e . Much of the e a r l y work i s c o n t r a d i c t o r y to the f i n d i n g s of l a t e r and more d e t a i l e d study. A short o u t l i n e of the s t r u c t u r e i n the v a r i o u s s e c t i o n s (from south to north) i s given below. P l a t e V I , page 46, i l l u s t r a t e s the best known s e c t i o n s . 4?th P a r a l l e l . I n t h i s r e g i o n the. i n f l e x i b l e nature of the B e l t i a n rocks and P a l a e o z o i c limestones has prevented the development i of f o l d s i n the western B e l t of the Rockies. Daly has mapped 1 Daly, R.AT G.S*C. Mem.15c*, p . l i b . twelve major f a u l t b l o c k s i n the f i v e m i l e s to the east of the Trench. The f i v e most w e s t e r l y of these b l o c k s , i n the Galton range show a p r o g r e s s i v e downdropping to the west, p l a c i n g s u c c e s s i v e l y younger s t r a t a i n l a t e r a l c o n tact. Thus we f i n d the Rocky Mountain Trench i n t h i s area bounded by f a u l t b locks PLATE VI Golden Canyon Creek Norman B r i s c o Shepard Steamboat Mountain P o l l o c k North end of Lake Windermere Walker Canal F l a t s Fort Steele Shepard Cranbrook S c h o f i e l d • \ 49th p a r a l l e l S c h o f i e l d , Shepard and Daly Legend Quaternary O Devono-Carboniferous O S i l u r i a n O Ordovic (Upper Lower Cambrian ^Upper Lower Pre-Cambrian O Windermere P u r c e l l S t r u c t u r e Sections - Rocky M o u n t a i n Trench. with, downthrow to the west. Daly considered these to he l"""Daly, R.A. G.S.C. Mem.13b, p . l i b . '' • \- • 2 • ' normal f a u l t s . Shepard l a t e r found the border f a u l t to be of 2 Shepard, S\P. J o u r , of Geol., Vol.34, I?2b. the high-angled t h r u s t type. I f the western Rockies were t h r u s t towards the Trench as s t r u c t u r e s to the n o r t h would seem to i n d i c a t e , then the l a t t e r i d e a i s the more reasonable. Daly assumed a f a u l t along the western border o f the Trench but S c h o f i e l d i n h i s work i n the Cranbrook area has 3 S c h o f i e l d , S.J. Trans.Roy.Soc.Can. t Sect.IV, 1920, p.75. shown that the Devonian limestone overlaps the P u r c e l l s e r i e s . T h i s c o n t a c t i s exposed on the low h i l l s between the Trench and Gold creek. The Cranbrook f a u l t , i n the v a l l e y of Gold creek p a r a l l e l s the Trench and has been t r a c e d from the Boundary to 8 m i l e s south of Cranbrook. The downthrow of a few hundred f e e t i s to the west. To quote S c h o f i e l d : "Hence the block between the f a u l t on Gold Creek and t h a t at the base of the e a s t e r n f l a n k of the Rocky Mountain Trench acted as a u n i t i n the e a r t h movements which i n i t i a t e d the Trench. The block c o n s i s t s o f a long narrow mass t i l t e d on a l o n g i t u d i n a l a x i s which was nearer the western border of the block so t h a t the i n c l i n a t i o n or d i p of the block i s to the east. Hence the normal f a u l t of l a r g e throw i s on the eastern side of the block i n the v a l l e y of Gold Creek and the small reverse f a u l t i s on the western side o f the block i n the v a l l e y of Gold Creek." Cranbrook* Devonian and Carbonfierous limestones u n d e r l i e the Trench to as f a r n o r t h as B u l l r i v e r . Between B u l l r i v e r and Canal F l a t s , the s t r u c t u r e has not been s t u d i e d but i t i s known t h a t ^ a t Canal Flats,, the Trench i s u n d e r l a i n by the Toby conglomerate..,of e a r l y Windermere or l a t e B e l t i a n times. : At Elko the Devonian-Carboniferous limestone of the eastern w a l l of the Trench p i t c h e s to the n o r t h to u n i t e near B u l l r i v e r , w i t h the Carboniferous limestone which f l o o r s the Trench. Here rocks of the P u r c e l l s e r i e s form the e a s t e r n f l a n k of the v a l l e y . Hence the throw at t h i s p o i n t must be very great as i t b r i n g s the e q u i v a l e n t of the A l d r i d g e forma-t i o n i n j u x t a p o s i t i o n w i t h Carboniferous limestone. Along the western boundary the Devono-Carboniferous limestones unconformably o v e r l i e the Gateway formation. I t i s not known whether the Cranbrook f a u l t , of small displacement, continues to the n o r t h of the t r a n s v e r s e Moyie f a u l t . Ho eastward c o n t i n u a t i o n of the t r a n s v e r s e Moyie and M a r y s v i l i e f a u l t s i n t o the Rocky mountains has been found. These f a u l t s are o l d e r than the. Laramide R e v o l u t i o n and a s s o c i a t e d f a u l t i n g i n the Trench and Rocky mountains. A study of the Hughes range might r e v e a l a c o n t i n u a t i o n there of the o l d e r n o r t h -e a s t e r l y s t r i k i n g f a u l t s and so g i v e f u r t h e r proof of the J u r a s s i d e age g i v e n these f a u l t s by S c h o f i e l d ; T S c h o f i e l d , S.J. G.S.C. Mem.16 r""p»95» Between Canal F l a t s and B u l l r i v e r S c h o f i e l d found the Trench to be f l a n k e d on both s i d e s by sediments of the -48- • P u r c e l l s e r i e s . But sin c e the rocks on the two si d e s belong to d i f f e r e n t members of the group and have d i f f e r e n t s t r i k e s he concluded that a f a u l t , c o n j e c t u r e d to have a throw o f 10,000 f e e t , u n d e r l i e s the d r i f t covered f l o o r of the Trench. At Canal F l a t s . On the western side of the Trench an overturned s y h c l i n e b r i n g s the K i t c h e n e r f o r m a t i o n of the B e l t i a n above the younger H o r s e t h i e f and Toby conglomerate of Windermere 1 ••• age. T HoTman~G-7W.K. Thesis of J.R". P o l l o c k , pp.27-25$ On the e a s t e r n f l a n k o f the Trench the sediments of the Windermere formation again outcrop at the same e l e v a t i o n and d i p eastward i n t o the Rocky mountains. Although the greater part of the f l o o r of the Trench i s d r i f t covered, Norman has found that i t i s f o l d e d i n t o a s e r i e s of small a n t i c l i n e s and s y n c l i n e s . However, i f a f a u l t does e x i s t t h e r e , I t cannot have a great throw since the Windermere s e r i e s u n d e r l i e the Trench and are exposed at the same e l e v a t i o n on both s i d e s of the v a l l e y . Lake Windermere. The P u r c e l l range b o r d e r i n g the Trench at the east continues i t s c h a r a c t e r i s t i c g e a n t i c l i n a l s t r u c t u r e . At i t s eastern margin, i . e . on the west f l a n k of the Trench, Walker l^Walker, J.F. Cf.S.'C. Mem. V pT -—— found the Windermere s e r i e s to be c l o s e l y f o l d e d and over-turned to the east suggesting that s t r u c t u r e s of t h i s part of the P u r c e l l range are a r e s u l t of a t h r u s t from the west. In the St a n f o r d range, the westernmost range of the Rocky mountains, the beds are f o l d e d i n t o a s e r i e s o f a n t i -c l i n e s and s y n c l i n e s w i t h a x i a l planes d i p p i n g to the n o r t h -east. These f o l d s are cut by two or more high angle t h r u s t f a u l t s of sm a l l displacement, the planes of which a l s o d i p northeast. These s t r u c t u r e s are those to be expected as a r e s u l t of a t h r u s t from the centre of the Rockies. The s t r u c t u r e beneath the P l e i s t o c e n e and Recent sediments of the Trench i s not d e f i n i t e l y known. The O t t e r t a i l (Upper Cambrian) and H o r s e t h i e f (Windermere) outcrop at the same e l e v a t i o n on the e a s t e r n and western f l a n k s of the Trench r e s p e c t i v e l y . S i n c e , i n t h i s a r e a , there i s no great d i s c o n -f o r m i t y between these two formations no normal f a u l t of great throw can be present i n the f l o o r of the Trench. As the H o r s e t h i e f formation outcrops on both f l a n k s of the Trench,- to the west and the southeast of the i n l e t of lake Windermere - and^as the s t r a t a immediately bordering the v a l l e y d i p away from the Trench on both s i d e s , the Trench i n t h i s area seems to be u n d e r l a i n by a small a n t i c l i n o r i u m . Steamboat Mountain. Ten m i l e s n o r t h o f lake Windermere a long narrow mountain, known as Steamboat mountain, r i s e s from the f l o o r o f the Trench and so d i v i d e s i t i n t o two v a l l e y s , the e a s t e r n , occupied by the Columbia r i v e r , the western by F o r s t e r and Francis creeks. The Columbia v a l l e y i s here bounded on the east by - £ 0 - '. the Beaverfoot range which extends northwest to the K i c k i n g Horse Pass. Along the l i n e of s e c t i o n the Upper Cambrian Goodsir formation i s exposed at the base of the Beaverfoot range. But to the south the u n d e r l y i n g O t t e r t a i l limestone outcrops. The s t r a t a i n the Beaverfoot range i n t h i s v i c i n i t y are not so c l o s e l y f o l d e d as those to the north or south but there i s s t i l l a suggestion of o v e r t u r n i n g to the southwest. Adjacent to the Trench the Goodsir and o v e r l y i n g B e a v e r f o o t - B r i s c o f o r m a t i o n d i p away from the Trench i n t o a small s y n c l i n e about 1 mile a c r o s s . This evolves i n t o an ' 1 a n t i c l i n e w i t h a n e a r l y v e r t i c a l a x i a l plane. P o l l o c k has not 1 P o l l o c k , J.R. T h e s i s , p.35* mentioned any f a u l t i n g i n t h i s part o f the Beaverfoot range. On Steamboat mountain, s t r a t a , Windermere to S i l u r i a n i n age, are exposed along the northern and higher part of the mountain. Along the l i n e o f s e c t i o n the formations are n e a r l y f l a t l y i n g . I f the d i p of"the beds.underlying the Beaverfoot range were p r o j e c t e d they would be brought up i n t o l i n e w i t h t h e i r c o n t i n u a t i o n i n Steamboat mountain. This suggests that no f a u l t of much displacement occurs but that an a n t i c l i n e c a r r i e s the formations outcropping i n the Beaverfoot range up to the e l e v a t i o n at which they are exposed i n Steamboat mountain. As Windermere s t r a t a outcrop beneath the v a l l e y f l o o r and at the same e l e v a t i o n s i n the P u r c e l l range and i n Steamboat mountain, i t i s probable that only minor s t r u c t u r e s have a f f e c t e d t h i s part of the Trench. . • . , -31-In the P u r c e l l range there i s exposed on the f l a n k of the Trench a complete s e c t i o n from the Windermere to the Devonian. These beds d i p t o the southwest. A l a r g e f a u l t w i t h southwest d i p has t h r u s t the Windermere s e r i e s over the f o s s i l -i f e r o u s Devonian beds. The P a l a e o z o i c s t r a t a u n d e r l y i n g the thrust b l o c k are crumpled f o r s e v e r a l m i l e s to the west. Thus compressive s t r e s s e s , i n the b u i l d i n g of the P u r c e l l mountains, have t h r u s t the s t r a t a to the east over younger rocks i n a manner s i m i l a r t o , though not on the same magnitude as i n , the le w i s Thrust. To the n o r t h of Steamboat mountain and occupying a s i m i l a r p o s i t i o n i n the Trench l i e s J u b i l e e mountain. Here the same formations outcrop. P o l l o c k has continued A l l a n f s s e c t i o n (see P l a t e XVII p.10J) across the Beaverfoot range to the Rocky Mountain Trench. The crest of the range i s occupied by a s y n c l i n e topped by the Bea v e r f o o t - B r i s c o formation. The lowest outcrop on the eastern w a l l of the Trench i s the Goodsir formation; t h i s i s o v e r l a i n by the Glenogle, Wonah q u a r t z i t e , and Be a v e r f o o t - B r i s c o formations. A l a r g e f a u l t has t h r u s t the Goodsir and o v e r l y i n g formations over the B e a v e r f o o t - B r i s c o . The plane of the f a u l t dips to the northeast and the t h r u s t i s to the west. This r e s u l t s i n a r e p e t i t i o n of the s t r a t a . The dip o f a l l the s t r a t a i s to the n o r t h e a s t . Golden. Although more work has been done on the Rocky Moun-t a i n Trench i n the neighbourhood of Golden than elsewhere, ' ' ' . .-52-there i s l i t t l e u n i f o r m i t y of o p i n i o n about the s t r u c t u r e s 1- . there u n d e r l y i n g the Trench. A l l a n , i n h i s admirable s e c t i o n across the Rockies, shows, i n the Beaverfoot range bordering the Trench, overturned f o l d i n g i n d i c a t i n g compression w i t h o v e r t h r u s t i n g from the n o r t h e a s t . (See P l a t e 1 A l l a n , ~ J . A . G.S.C. Guide Bk. b, P t . 2 , p . l b 7 . Daly has s t u d i e d the P u r c e l l and S e l k i r k ranges to the west of Golden and t h e i r s t r u c t u r e s are d e s c r i b e d i n d e t a i l e l s e -where i n t h i s t h e s i s . 2 Daly, R.A. G.S.C. Mem.bo", pp.bb-113. At the foot of the Beaverfoot range on the east side of the Trench the Goodsir formation i s exposed and^at the west side of the Trench„lt i s again exposed a t the foot of the eastern f l a n k of the P u r c e l l mountains. Hence the. O r d o v i c i a n outcrops at the same l e v e l on both s i d e s of the Trench. The Dogtooth mountains, the most e a s t e r l y of the P u r c e l l range, are a n t i c l i n a l i n form w i t h the d i p to the Columbia forming the e a s t e r n l i m b . Hence s u c c e s s i v e l y o l d e r formations - the O t t e r t a i l (Upper Cambrian), O l e n e l l u s zone (lower Cambrian), and q u a r t z i t e s (Pre or lower Cambrian) -outcrop: as one goes westward. Daly^ b e l i e v e d t h a t the B e l t i a n rocks of the P u r c e l l s "3 Daly~ R.A. Gr.S.G. Mem, bb, p. 113. were i n j u x t a p o s i t i o n w i t h the O r d o v i c i a n beds u n d e r l y i n g the v a l l e y . This sharp contact he e x p l a i n e d by h i s "Great F a u l t " . . • • 4 with a v e r t i c a l displacement of about 20,000 f e e t . S c h o f i e l d -53-showed t h a t , i f the Cougar q u a r t z i t e s o v e r l i e the L a u r i e formation, as Daly s t a t e d , then they must he P o s t - C a r b o n i f e r o u s , not B e l t i a n , i n age, as Daly b e l i e v e d . T h i s would b r i n g the Upper Cambrian i n contact w i t h the Upper P a l a e o z o i c and make the downthrow side on the west not on the east. But l a t e r work has shown t h a t they do not o v e r l i e the 1 L a u r i e . Walcott places the Cougar q u a r t z i t e s i n the Lower 1 Walcott, C D . S.M.C. , F o l . 7 5 . N o , l , p.39* Cambrian from the f o s s i l s and found no evidence of f a u l t i n g between them and the Cambro-Grdovician rocks u n d e r l y i n g the Trench. 2 Shepard i n w r i t i n g on the s t r u c t u r e of the Trench 2'She para, F.P. J o u r , of GeoTTT V o l . 3 0 , 1922, p.133* ' i n t h i s v i c i n i t y s t a t e s t h a t at Canyon Creek near Golden there i s no f a u l t and the formations f o l l o w each other i n normal s t r a t i g r a p h i c s u c c e s s i o n . At Beavermouth, 25 m i l e s n o r t h of Golden, Daly i n f e r r e d a normal f a u l t of 15,000 f e e t d i s p l a c e -ment sepa r a t i n g the Cougar q u a r t z i t e on the west from the Cambro-Ordovician s e r i e s on the e a s t . As Walcott has since placed the Gougar q u a r t z i t e s i n the Lower Cambrian i t i s probable that the Cambro-Ordovician beds of the f l o o r of the Trench o v e r l i e them without f a u l t i n g . No t h r u s t plane of a great f a u l t has been seen by Daly, or others i n t h i s area. I t s p o s i t i o n beneath the d r i f t - c o v e r e d f l o o r of the Trench was i n f e r r e d to account f o r the j u x t a p o s i t i o n o f sediments of apparently w i d e l y d i f f e r e n t ages. The l a t e r work of Scho-f i e l d , Shepard and Walcott has shown that these rocks are not of great d i f f e r e n c e i n age but occupy adjacent p o s i t i o n s i n the s t r a t i g r a p h i c column. Thus t h e i r present r e l a t i o n s h i p s are due to normal sedimentary sequence and not to any f a u l t s of great displacement. From the above evidence i t i s concluded that the Trench at Golden i s u n d e r l a i n , not by a "Great F a u l t " , but by a somewhat crumbled s y n c l i n a l s t r u c t u r e . S t r u c t u r e i n the Rocky Mountain Trench between Golden and  Princ e George. To the n o r t h of Golden l i t t l e g e o l o g i c a l work has been done and that of an e x p l o r a t o r y nature. The works of 1 2 3 4 Coleman , McConnell , M a l l o c h , and McEvoy are a l l e x c e l l e n t f o r that type of work but giv e few d e t a i l s of the s t r u c t u r e across the Trench. 1 Coleman, A.P. T.R.S.C., V o l . 7 , 1889, p.99 ~ 2 McConnell, R.G. G.S.C., Ann.Rept., Vol.XVI, 1900 , p.40d. 3 M a l l o c h , G.S. G.S.C, Summ.Rept., 1909, pp.120-123. 4 McEvoy, J . G.S.C., Ann.Rept., Vol.XVI, 1900, p . 3 8 . . . . For the f o l l o w i n g reasons, s t r u c t u r e s i n t h i s r e g i o n w i l l prove harder to decipher even w i t h d e t a i l e d work. (1) The s c h i s t s and gneisses u n d e r l y i n g the Trench and outcropping on the mountains wi11 be more d i f f i c u l t to c o r r e -l a t e than the unmetamorphosed sediments of the southern part of the Trench. (2) No s t r a t i g r a p h i c column showing the sequence of s e d i -mentation has yet been made. (3) S t r u c t u r e s u n d e r l y i n g the trough are more concealed by a t h i c k mantle of a l l u v i u m and d r i f t . | Surprise Rapids. j Coleman found s o f t g r e e n i s h shales and q u a r t z i t e s at i lookout P o i n t i n the Rookies. He regarded these rocks as the more i n d u r a t e d e q u i v a l e n t of those found by McConnell i n the • • 1 western part of Bow Pass and s i n c e p l a c e d by A l l a n i n the T A l l a n , J.A. G.S.CT"Guide Book, Ho.b , P t . I I . ~ Cambrian, The beds i n t h i s part of the Rockies d i p more or-l e s s s t e e p l y away from the Trench. Along the western f l a n k of the Trench at S u r p r i s e mountain are t y p i c a l horneblende and mica s c h i s t s d i p p i n g at about 40° to the southwest. As these rocks are probably Archean and outcrop at an even higher e l e v a t i o n than do the P a l a e o z o i c s of lookout P o i n t across the Trench, Coleman po s t u l a t e d a great f a u l t u n d e r l y i n g the trough. I t appears that the s t r a t a on both f l a n k s d i p away from the v a l l e y making a great f a u l t w i t h downthrow to the east necessary to b r i n g the Archean (?) and P a l a e o z o i c i n t o j u x t a p o s i t i o n , but u n t i l f u r t h e r study has d e f i n i t e l y e s t a b l i s h e d the ages of the formations i n v o l v e d t h i s f a u l t i s purely c o n j e c t u r a l . Excepting f o r a few m i l e s of f i n e l y banded s c h i s t o s e limestone, the Trench, between S u r p r i s e Rapids and Tete Jaune Cache i s f l o o r e d and f l a n k e d by s c h i s t s and g n e i s s e s , o f t e n e x c e s s i v e l y f o l d e d , crumbled and c o n t o r t e d . I t i s therefore c l e a r that the boundary between the Archean (?) and the Palaeo-z o i c s of the Rockies l i e s f o r the g r e a t e r part of t h i s • • •• • ' 2 distance to the northeast of the Trench. 2 Coleman, A.P. op. c i t . , p.100. -_56~ Tete Jaune Cache. Here McEvoy has de s c r i b e d a great s e r i e s of mica 1 McEvoy, J . op, cit«,p.89d. s c h i s t s on the southwest side of the v a l l e y . He b e l i e v e d that t h e i r true bedding p a r a l l e l e d t h a t of the Bow R i v e r s e r i e s outcropping on the eas t e r n s i d e of the Trench, but that the apparent d i p of these rocks to the southwest was due to t h e i r 2 s c h i s t o s i t y . M a l l o c h , i n l a t e r work i n the area, found the 2 op. c i t . , p.I22. ~ s t r a t a , i n an area near t h a t examined by McEvoy^to d i p to the southwest at comparatively high angles. He regarded these s c h i s t s as the metamorphosed e q u i v a l e n t s of the Shuswap s e r i e s . The Bow R i v e r s e r i e s exposed i n the western f l a n k of the Rocky mountains have a s i m i l a r general d i p to the south-west. These beds are crumpled and, to the east, f o l d over i n an a n t i c l i n e to dip under the limestones and q u a r t z i t e s of the o v e r l y i n g C astle Mountain s e r i e s . This l a t e r s e r i e s forms the mass of Mount Robson and the other h i g h mountains i n that d i r e c t i o n . The c l e a r e s t account of the geology of t h i s d i s t r i c t i s by S c h o f i e l d and h i s d e s c r i p t i o n i s as f o l l o w s : 3 S c h o f i e l d , S.J. T.R.S.C., Sect.IY, 1920, p.bl ~ "The w r i t e r ' s observations on t h i s s e c t i o n , i n 1918, showed that the rocks exposed i n the f l o o r o f the trench were badly broken and strong shearing had developed i n a d i r e c t i o n c o i n c i d i n g w i t h the trend of the t r e n c h . This shearing and crushing was l a t e r i n age than the metamorphism developed i n the Shuswap r o c k s . I t i s considered to be r e l a t e d i n age to s i m i l a r shearing and f a u l t i n g which' have been determined i n the trench to the south, although no d i r e c t evidence on t h i s point has been recorded. Before t h i s i s attempted a c r i t i c a l study of the s o - c a l l e d Shuswap s e r i e s must be completed and i t s p o s i -t i o n i n the g e o l o g i c a l column e s t a b l i s h e d . According to M a l l o c h , the Bow R i v e r s e r i e s borders on the n o r t h e a s t e r n slope of the trough from Tete Jaune Cache to the h i g h mountain opposite the mouth of Goat R i v e r . From t h i s point northwards, the C a s t l e Mountains s e r i e s crosses the r i v e r at the foot of Goat R i v e r r a p i d s . On the n o r t h e a s t e r n f l a n k , g n e i s s e s and s c h i s t s of the Shuswap s e r i e s extend northwards as f a r as Rau Shuswap R i v e r where they are succeeded by the rocks of the C a s t l e Mountain s e r i e s . At Grand Canyon, Devonian rocks outcrop and occur on both sides of the trough." P r i n c e George to F i n d l a y Forks. From i t s source t o w i t h i n 75 miles southeast of the Big Bend, the F r a s e r r i v e r f l o w s between the Rocky and Caribou mountains. From t h i s point to the F i n d l a y r i v e r i t i s bounded on the east by, the Rocky mountains and on the west by the I n t e r i o r P l a t e a u . For 75 m i l e s n o r t h of P r i n c e George the trough i s i n d i s t i n c t but probably f o l l o w s the Pack and Crooked drainage to the v a l l e y of the P a r s n i p . Although the P.G.E. Resources Survey t r a v e r s e d t h i s region i n 1929 and 1930 l i t t l e i s known of the s t r u c t u r e s e i t h e r u n d e r l y i n g or to the west of the Trench as a heavy mantle of d r i f t covers the country. To the e a s t , i n the Rocky - 3 8 -mountains, the Pre-Cambrian K i s i n c h i n k a s c h i s t s extend along the western f l a n k of the range. The only rocks outcropping through the d r i f t - c o v e r e d v a l l e y f l o o r are a remarkable b e l t of Cretaceous sandstone and conglomerate of the Bu l l h e a d mountainfformation and a small area of T e r t i a r y sediments. (See P l a t e X X I , page 121.) Fi n d l a y R i v e r Area. From F i n d l a y Forks n o r t h to the mouth of the Ingenika the Trench i s f l a n k e d on both s i d e s by the P r e -1 Cambrian s c h i s t s and g n e i s s e s . McConnell has c o r r e l a t e d these rocks w i t h the Shuswap s e r i e s to the south. As the 1 See Dolmage, V. G.S.C. Summ.Rept. 1927, Pt.A, pp.21-41. ~~ sediments are cont o r t e d and f o l d e d , and the v a l l e y f l o o r d r i f t covered, l i t t l e i s known of the' s t r u c t u r e of the Trench except that the s t r i k e of the rocks p a r a l l e l s the v a l l e y . Cambrian limestone o v e r l i e s the s c h i s t s and outcrops i n bands above the Pre-Cambrian. North o f the mouth of the Ingenika the limestone borders the Trench on the west but the Pre-Cambrian continues along the Rooky mountain f l a n k . Here the Trench i s u n d e r l a i n by the unmetamorphosed T e r t i a r y sandstones, conglomerates and shales, which have not been i n v o l v e d i n the orogenic movements. These sediments a l s o s t r i k e p a r a l l e l to the Trench and extend up the Fox r i v e r and probably f a r to the no r t h . •59-F i g . 4 S i n c l a i r Springs Summary. Canal F l a t s 4 9 t h P a r a l l e l COT The s t r u c t u r e s along the Trench i n d i c a t e i t i s the r e s u l t of compressive s t r e s s e s . Along i t s western border the deformation i n d i c a t e s a t h r u s t i n g of the P u r c e l l s to the e a s t . I t s e a s t e r n border, l a t e r i n age, was undoubtedly the r e s u l t of compression a c t i n g from the a x i s o f the Rockies. I f the f a u l t i n g at the 4 9 t h p a r a l l e l i s regarded as being of the high-angled t h r u s t type the one known ex c e p t i o n to t h i s g e n e r a l i t y i s removed. I t i s true that the Trench i s not always the l i n e of demarcation between J u r a s s i d e and Laramide s t r u c t u r e s , but nevertheless i t s present physiographic development i s the r e s u l t o f s t r u c t u r e and not of o r d i n a r y e r o s i o n . (See F i g . 4 . ) -6o-S e c t i o n I I I . STRUCTURE OF THE ROCKY MOUNTAINS PROPER. From the I n t e r n a t i o n a l Boundary to the Athabasca the Rockies can be d i v i d e d i n t o the three s t r u c t u r a l b e l t s pre-v i o u s l y mentioned. To the n o r t h , i n the Athabasca and Peace r i v e r s e c t i o n s , the western b e l t i s not so h i g h l y developed -i f present at a l l . Rocky mountain s t r u c t u r e w i l l be discussed under the f o l l o w i n g s u b - s e c t i o n s ; I . S t r u c t u r e along the I n t e r n a t i o n a l Boundary. I I . T y p i c a l F o o t h i l l s area between the I n t e r n a t i o n a l Boundary and Smoky r i v e r . I I I . S t r u c t u r e along the Main l i n e of the C.P.R. and adjacent areas from the S e l k i r k mountains to the P l a i n s . IV. S t r u c t u r e along the C.N.R. (Athabasca and Yellowhead Pass.; V. S t r u c t u r e i n the Peace r i v e r area. I . S t r u c t u r e along the I n t e r n a t i o n a l Boundary. • •" • 1' ' 2 Daly and Mackenzie have d i v i d e d the Rocky mountains 1 Daly, R.A. G.S.C. Mem.38, P t . I . ~ ' ~~~ 2 Mackenzie. J.D. T.R.S.C.. Vol.XVI, 1922. p.lo6. between the I n t e r n a t i o n a l Boundary and the Crowsnest pass i n t o three s t r u c t u r a l areas. The geographic r e l a t i o n s of these areas are shown on P l a t e V I I , page 60. Mackenzie designates them as the western, c e n t r a l , and eastern areas. From the Boundary to North Kootenay Pass the three areas are character-i s t i c a l l y developed but no r t h of t h i s the western and c e n t r a l - 6 1 -areas appear to merge. Western S t r u c t u r a l Area. • '1 • • Daly found the MacDonald and Galton ranges to be I Daly, R.A. idem., p.117« made up of homoclinal f a u l t blocks separated by l a r g e normal f a u l t s (see accompanying s t r u c t u r e s e c t i o n , P l a t e V I I I , page 6 2 ) . There are at l e a s t twelve of these major f a u l t s i n the two ranges, the f i v e most w e s t e r l y showing a p r o g r e s s i v e down dropping to the west. Not too much s t r e s s i s to be l a i d on the accuracy of t h i s work s i n c e Daly considered i t h y p o t h e t i c a l . To the n o r t h the f a u l t i n g i s replaced to a l a r g e extent by f o l d i n g . This change i n s t r u c t u r e may be caused by the appearance o f younger l e s s competent sediments to the n o r t h , f o r , whereas along the Boundary only very hard competent B e l t i a n rocks outcrop, to the north younger s t r a t a appear and Cretaceous measures are exposed i n Crowsnest Pass. This change may be due to one or a l l of three causes: (1) The Rockies may have been o r i g i n a l l y much higher along the Boundary than to the north and the consequent greater e r o s i o n may have removed the younger s t r a t a . (2) The gr e a t e s t thicknesses of B e l t i a n sediments are found i n t h i s area. But as t h e i r base i s nowhere exposed t h i s may or may not be an i n d i c a t i o n of a greater t o t a l t h i c k n e s s of B e l t i a n s t r a t a l a i d down. Again there may be a t h i n n i n g of the o v e r l y i n g P a l a e o z o i c and Mesozoic s t r a t a from the Crowsnest Pass to the Boundary which has subsequently been removed by eros i o n . These sediments i n the p a r t i a l s e c t i o n s exposed show u o Pi 03 pq t-4 09 M aJ s4 <u PS CD 03 • H O o <L> o +» CO a> 0 o > H M o3 PS I P i <P P i O 44 c5 CO 0) r-( H • H P> 03 >» O • H O 03 P i • H >5 as H +3 M CO CO pcj fH C5 • r l a o a> r-t •«i <*3 some t h i n n i n g "between the Crowsnest and the I n t e r n a t i o n a l Boundary hut not s u f f i c i e n t to account f o r t h e i r almost e n t i r e • • - 1 ' removal. 1 Cummings, J» Pers o n a l communication. (3) The younger s t r a t a were removed more completely by er o s i o n i n the south because of the nature of the s t r u c t u r e . To the no r t h these s t r a t a are caught i n the mountain f o l d s whereas along the Boundary they l a y on top of the f a u l t blocks and were t h e r e f o r e much more s u s c e p t i b l e to e r o s i o n . The C e n t r a l S t r u c t u r a l Area. This area i s a great s y n c l i n e of Pre-Cambrian r o c k s , the general s t r u c t u r e of which probably holds as f a r north as North Kootenay pass. I t i s d i v i d e d from the western s t r u c t u r a l area by the l a r g e normal f a u l t or zone f a u l t i n g along the east side of iflathead v a l l e y . These f a u l t s have a downthrow to the west g i v i n g the Clarke range or c e n t r a l area a h o r s t r e l a t i o n -s h i p to the block underneath Flathead v a l l e y . These s t r u c t u r e s are discussed i n greater d e t a i l under the heading " S t r u c t u r e i n the Flathead area", page 63. Because of the wide western swing of the Lewis t h r u s t the cen t r a l - s t r u c t u r a l area narrows con- \ s i d e r a b l y to the n o r t h . The e a s t e r n l i m b , or perhaps the whole of t h i s great s y n c l i n e of Pre-Cambrian s t r a t a , i s th r u s t over the Cretaceous rocks to the east along the Lewis t h r u s t . This enormous displacement has been traced f o r many miles i n A l b e r t a and Montana. I t s important f e a t u r e s are described on page .-63-The E a s t e r n S t r u c t u r a l Area. 1 Under t h i s heading Mackenzie i n c l u d e s the F o o t h i l l s 1 Stewart. J.S. G.S.C. Mem.112. 1919• p.11. " ' ~ and "The R o l l i n g P l a i n s " of Stewart. G e o l o g i c a l l y the whole area belongs to the D i s t u r b e d B e l t but f o r 20 miles north o f the Boundary the f o o t h i l l s are l a c k i n g and t h i s p o r t i o n i s supposed at one time to have been o v e r l a i n by the Lewis Thrust. S t r u c t u r a l l y i t i s c h a r a c t e r i z e d by numerous n e a r l y p a r a l l e l reverse s t r i k e f a u l t s , of great l e n g t h and unusual steepness. These f a u l t s are a s s o c i a t e d w i t h s t r o n g f o l d s . In the " R o l l i n g P l a i n s " near the boundary the f a u l t -i n g i s not n e a r l y so pronounced as i t i s both to the n o r t h End south. S t r u c t u r e i n the Flathead Area. "The s t r u c t u r e of the Flathead area may be s u c c i n c t -l y d e scribed as that of a downfolded, warped, monoclinal f a u l t block w i t h north-east s t r i k e s and,for the most part,south-east "•• ' 2 :• d i p s . " This downthrown bl o c k i s bounded by normal f a u l t s 2 Mackenzie, J.D. G.S.C. Mem.87. "Geology of a P o r t i o n o f the Flat h e a d Coal Area. B.C." pp.38.39. with a northwest s t r i k e , as shown i n F i g . 5 . The western up-thrown block forms limestone mountains w i t h southwestward dipping s t r a t a s i m i l a r to the MacDonald range to the west. In the c e n t r a l downthrown block younger ranges are exposed. Here the s t r a t a dip moderately from a north-south a n t i c l i n a l a x i s . To the south of the i n t e r s e c t i o n of t h i s a x i s w i t h the north-w e s t e r l y t r e n d i n g boundary f a u l t the f o l d i n g becomes l e s s -64-\ c 2 1 V ///C2 F i g . 5 (compiled from G.S.C. map) Recent - pink T e r t i a r y - y e l l o w Mesozoic - green P a l a e o z o i c - blue pronounced. In the downthrown block or graben s u c c e s s i v e l y younger formations outcrop to the east as the s t r a t a d i p s h a r p l y eastward to giv e the f a u l t b l o c k a monoclinal charac-t e r . The T e r t i a r y Kishinema formation outcropping i n the graben have been s t r o n g l y deformed, probably more than once. The l e w i s Thrust. As t h i s great o v e r t h r u s t i s of such importance i n co n s i d e r i n g the s t r u c t u r a l f e a t u r e s of the Easte r n B e l t of the Rocky mountains, i t i s here considered i n some d e t a i l . i n Montana and 85 m i l e s i n A l b e r t a ) . I t i s known to extend as f a r north as Gould Dome ( n o r t h of Kootenay pass) and Rose* 1 See Mackenzie, J.D. T.R.S.C.. Vol.XVI. 1922. p.111, s t a t e s i t may even extend 50 m i l e s f u r t h e r north to the Kananaskis r i v e r . " I f i t does not continue northward as a si n g l e t h r u s t plane, the break i s represented by other s i m i l a r planes." I t has been traced as f a r south as the southern end of G l a c i e r N a t i o n a l park i n Montana but i t s southern e x t r e m i t y The known l e n g t h of the f a u l t i s 135 miles (50 miles - 6 5 -•1. has never been mapped. 1 Campbell, M.R. U.S.G.S. Bull.bOO. 1914. p.12. i t Worth Kootenay pass there i s a d i s t i n c t change t o p o g r a p h i c a l l y i n the r e l a t i o n of the Lewis Thrust to the Front ranges of the Hookies. South of the pass the t h r u s t i s found at or near the base of the Front ranges and determines t h e i r p o s i t i o n . To the north the t h r u s t l i e s behind the Jj'ront ranges, here represented by the L i v i n g s t o n e and Highwood ranges. Mackenzie deduces from t h i s that "the Lewis Thrust i s an i n t e g r a l p a r t of the s t r u c t u r e of the mountains themselves, and i s not found only where the mountains j o i n the p l a i n s . " Throughout i t s l e n g t h o l d e r rocks have been pushed up to and over the Cretaceous s t r a t a . The break along the 2 •• " Lewis t h r u s t lessens i n magnitude to the n o r t h . Rose suggests 2 Rose, B. G.S.C. Summ.Rept. 1919, pp.l4-19C "Highwood Coal - Area. A l b e r t a . " ; t h a t the t h r u s t may be r e p l a c e d by very complex f o l d i n g and f a u l t i n g f a r t h e r n o r t h . This decreasing displacement along the f a u l t as one goes n o r t h i s w e l l shown by the s u c c e s s i v e l y younger rocks o v e r t h r u s t on the Cretaceous. In Montana and along the Bound-' ary considerable t h i c k n e s s e s of A l t y n limestone, one of the oldest Pre-Cambrian formations, r e s t s on the Cretaceous. At North Kootenay Pass the Siyeh, 7,500 f e e t s t r a t i g r a p h i c a l l y above the A l t y n , o v e r l i e s the Cretaceous Kootenay formation. In the Crowsnest area the Devonian l i e s on the B e l l y R i v e r sandstone. W i l l i s d e scribes the t h r u s t surface as warped. But -66-c o n s i d e r i n g the great extent of the "break the surf a c e i s remarkably l e v e l . The t h r u s t s u r f a c e has ve r y low westward d i p . The a c t u a l d i s t a n c e of the o v e r t h r u s t has not been measured; however, i t i s known to be at l e a s t 15 miles i n G l a c i e r N a t i o n a l Park and at l e a s t 7 mi l e s i n nor t h e r n Montana. Chief Mountain i n Montana i s an e r o s i o n a l remnant of the B e l t i a n o v e r t h r u s t . I t l i e s on the Cretaceous sediments 20 miles from the present f r o n t a l escarpment. Daly^ suggests that T Daly. H.A. G.S.C Mem.3b, pp.ll7~~and 599* ~"~" " "°~ the e n t i r e C larke range represents a g i g a n t i c block loosed from i t s ancient foundations and f o r c e d b o d i l y over the Cre-taceous or Carboniferous formations. In t h a t case the t h r u s t would have d r i v e n the block at l e a s t 40 miles across country. The displacement i s known to be at l e a s t 20 mi l e s but i n view of the great s t r a t i g r a p h i c break, the low dip of the f a u l t plane and the l e n g t h of the f a u l t an o v e r t h r u s t of 40 mil e s i s quite p o s s i b l e . S t r u c t u r e above the Thrust. To the north there i s l i t t l e disturbance of the over-t h r u s t beds to i n d i c a t e such an enormous d i s l o c a t i o n . Here the sediments are cut by r e g u l a r j o i n t s approximately at r i g h t angles to the bedding. 2' Near the 4 9 t h p a r a l l e l W i l l i s has described the 2"WTlTis. B. idem. ' breaks i n the o v e r t h r u s t b l o c k . In places the whole mass i s div i d e d i r r e g u l a r l y i n t o b l o c k s w i t h a maximum of 25 f e e t on a s i d e . The s i d e s of these blocks are s l i c k e n s i d e d and, when i n -67- • o r i g i n a l o r i e n t a t i o n , the s l i c k e n s i d e s show much r e l a t i v e h o r i z o n t a l displacement of the neighbouring fragments. In other places the limestone has r e g u l a r l i n e s of bedding and n e a r l y v e r t i c a l j o i n t s such as occur along the Lewis Thrust i n the n o r t h . In general the s t r u c t u r e i s that of the major Lewis t h r u s t - a v e r y gentle d i p to the west w i t h minor t h r u s t f a u l t s at steeper, angles e i t h e r p a s s i n g upwards to the surface or i n t e r s e c t i n g other higher f a u l t s . (See F i g . -1, page 157•) The t h i c k n e s s of the s t r a t a i n v o l v e d i n t h i s r e -1 peated o v e r t h r u s t i n g v a r i e s , b u t at yellow Mountain W i l l i s has I T w i l l i s , B.• idem. shown that not over 500 f e e t of s t r a t a have been o v e r t h r u s t 2 r e p e a t e d l y to p i l e up 2400 f e e t h i g h . Dawson describes a Fltewson. G.M. G.S.C. Ann.Rept.. V o l . 1 , 18135. p.43B. great p i l i n g up of o v e r t h r u s t segments west of Waterton l a k e s with probably l e s s than 1000 f e e t of sediments i n v o l v e d . Above t h i s zone of minor t h r u s t i n g and the upper major t h r u s t , i f any, the s t r a t a are not n o t a b l y d i s l o c a t e d on planes of o v e r t h r u s t i n g . Dawson, however, observed s t r u c t u r e planes p a r a l l e l i n g the Lewis t h r u s t but more than 8000 f e e t s t r a t i g r a p h i c a l l y above them and i n the heart of the s y n c l i n e to the west. Whether there i s movement along these planes or not i s not known. They are i n t e r e s t i n g on account of t h e i r bearing on the d i s t r i b u t i o n of the s t r e s s . S t r u c t u r e s below the Thrust. S t r u c t u r e s below the t h r u s t plane are seen onl y i n - 6 8 -th e narrow zone p a r t i a l l y covered by the t h r u s t block and i n the b e l t from which the t h r u s t block has been eroded* The extent of the zone f o r m e r l y covered by the superimposed s t r a t a cannot be deciphered a c c u r a t e l y but there i s no doubt that the overthrust mass f o r m e r l y extended f a r t h e r east than i t s present p o s i t i o n . The r e l a t i v e l y unfolded b e l t immediately east of the Clarke range suggests that the o v e r t h r u s t block extended 6 to 8 m i l e s east of the present f r o n t a l escarpment (see page 1 Stebinger , i n doing d e t a i l e d work i n northern i T s t e b i n g e f T B. U.S.G.S. Bull.621" p.129. ~ Montana, has shown that between the Rocky mountain escarpment and the D i s t u r b e d B e l t to the east there l i e s t h i s b e l t o f n e a r l y h o r i z o n t a l rocks s i m i l a r to that described i n the pre-vious paragraph. I t s s t r u c t u r e i s that of a monocline d i p p i n g g e n t l y to the southwest. But along the western edge of t h i s monocline and immediately adjacent to and u n d e r l y i n g the over-t h r u s t s t r a t a i s a narrow b e l t of d i s t u r b e d s t r a t a s t e e p l y f o l d e d as a r e s u l t of s t r e s s e s from the southwest. The change from the h o r i z o n t a l to these contorted rocks occurs a b r u p t l y w i t h i n a few f e e t without any intermediate zone o f gentle f o l d i n g . Age of the Lewis Thrust. Mackenzie concludes that as "the Laramide R e v o l u t i o n took place not e a r l i e r than the uppermost Cretaceous nor l a t e r than the l a t e s t Eocene" and as the Lewis t h r u s t was one of the l a t e s t e f f e c t s of the compressive s t r e s s e s of the Laramide - 6 9 - • • r e v o l u t i o n " the p r o b a b i l i t y of an Eocene age i s i n d i c a t e d . This subject has been discussed more f u l l y elsewhere. I I . T y p i c a l F o o t h i l l s areas between the I n t e r n a t i o n a l Boundary and Smoky R i v e r . D i s t u r b e d B e l t of Southwestern A l b e r t a . The area l i e s between the e a s t e r n esoarpment of the Rocky mountains and the f l a t - l y i n g sediments of the P l a i n s . Thrust f a u l t i n g i s c h a r a c t e r i s t i c of the western part of the area b o r d e r i n g the Rocky mountains. Here the s t r a t a are i n -c l i n e s at a l l angles. Eastward the deformation grows l e s s and 1 dies out i n the h o r i z o n t a l sediments of the P l a i n s . Stewart 1 Stewart, J.3. G*S.G, Mem.112. "Geology o f the D i sturbed B e l t of S.W. A l b e r t a . " p.47.. st a t e s that the present e l e v a t i o n of the s t r a t a , i n some cases over 6000 f e e t , i s due not to the i n t e r n a l s t r e s s e s w i t h i n the earth's c r u s t which f a u l t e d the area but to subsequent c o n t i n -e n t a l warpings or e p e i r o g e n i c movements. P r i o r to the f a u l t i n g the e n t i r e area was the e a s t e r n limb of an a n t i c l i n o r i u m whose c r e s t was i n the L i v i n g s t o n e range to the w e s t H e r e the hard P a l a e o z o i c limestones and q u a r t z i t e s are bowed i n t o an a n t i c l i n e and are o v e r l a i n , as one goes east to the Porcupine H i l l s , by s u c c e s s i v e l y younger Meso-z o i c r o c k s . The area has been d i v i d e d on the b a s i s of deform-a t i o n by Stewart i n t o ( l ) the Porcupine H i l l s , ( 2 ) the Disturbed B e l t Proper. 1. The Porcupine H i l l s . A broad s y n c l i n e extends along the e a s t e r n edge of the Disturbed B e l t from the 49th U. p a r a l l e l to the Athabasca r i v e r . In the map area t h i s s y n c l i n e i s occupied by the T e r t i a r y Porcupine H i l l s . As i s to be expected, the f o l d i s asymmetric w i t h the steeper d i p on the western limb of the s y n c l i n e next to the Disturbed B e l t proper. The s t r a t a have, 0 0 i n the west, a maximum d i p of 15 - 20 but f l a t t e n to n e a r l y h o r i z o n t a l i n the east. 2. The Dis t u r b e d B e l t proper. This b e l t i s c h a r a c t e r i z e d by a preponderance o f westward dips g e n e r a l l y at f a i r l y high angles. The t i l t i n g of the s t r a t a has been caused to a great extent by the t h r u s t f a u l t i n g and to a much l e s s e r degree by the overturned f o l d i n g . •Trend of the Rocks. There are two major bends i n the s t r i k e of the rocks are i n t h i s area. These t u r n s / a p p a r e n t l y caused by a t h r u s t from the west as the trend of the rocks f o l l o w s that of the moun-t a i n f r o n t . For 12 m i l e s n o r t h o f the Boundary the trend i s 6 ••. W 30 W. At t h i s p o i n t there i s a decided swing west to n , 0 II 50 - 60 W. (See P l a t e V I I , page 6 0 . ; In the v i c i n i t y of 0 the Crowsnest r i v e r the beds swing t o U 50 W. These bends are w e l l shown by the p o s i t i o n of the E a s t e r n Escarpment of the Rocky mountains and the B r i t i s h Columbia-Alberta boundary. Fo l d s . 1 Stewart has c l a s s i f i e d the var i o u s types of f o l d i n g 1 Stewart, J.S. G.S.C. Mem.112, pp.4b.49, beginning w i t h the s m a l l e s t , as: (I) Small open f o l d s . The minor s t r u c t u r e s do not extend to any depth nor can they he tra c e d any d i s t a n c e at the s u r f a c e . They are most common at the ea s t e r n edge of the Disturbed B e l t and probably are the easternmost v e s t i g e s of deformation. (2) Overturned f o l d s . Overturned f o l d s i n the southern part of the Disturbed B e l t are s m a l l and of l i m i t e d e x t e n t . In t h i s the r e g i o n d i f f e r s from the Moose Mountain area,occupying a s i m i l a r p o s i t i o n to the north,where there has been con s i d e r a b l e o v e r t u r n i n g . (See page 93 . ) (3) Sharp, c r e s t e d i n c l i n e d f o l d s . These N-shaped f o l d s 0 t y p i c a l l y have 60 dips on the west s i d e of the a n t i c l i n e s and ne a r l y v e r t i c a l east l i m b s . Several f o l d s of t h i s type occur between the Crowsnest and Oldman r i v e r s . (4) Unsymmetrical open f o l d s . They are perhaps the most common type. U s u a l l y these f o l d s have steep d i p s . The f o l l o w i n g f o l d s of t h i s type are i n d i c a t e d on the accompanying s e c t i o n s , F i g . 6. F i g . 6 ( a f t e r Stewart) (a) I n a n t i c l i n e , formed of B e l l y r i v e r formations on the • uplands and of Benton shales i n the v a l l e y s , p a r a l l e l s the trend f o r 12 mil e s i n the v i c i n i t y of Willow Greek The western limb of the arch i s ap p a r e n t l y broken by a f a u l t (b) A sharp a n t i c l i n a l f o l d o c c u r r i n g near Lundbreck on the Crowsnest l i n e of the C.P.R. has been traced f o r 9 m i l e s . To the south i t i s apparently cut by a f a u l t {G) A broader s y n c l i n a l f o l d i n the Benton shales occurs about 4 m i l e s to the west of the Lundbreck a n t i c l i n e * This s y n c l i n e p i t c h e s n o r t h . Less than a mile south of the r a i l w a y i t changes to a monocline of Blairmore sandstone, d i p p i n g to the west. (,d) Se v e r a l other f o l d s have t h e i r e a s t e r n limbs broken, cl o s e to the c r e s t , by f a u l t s . I n some cases the east e r n limb i s caused by the drag of the f a u l t . (5) Broad u n d u l a t i n g f o l d s . A s t r i p , 678 mil e s wide, o f v e r y gentle dips borders the Clarke range at the south. F a u l t s , i f they do occur, must be' of v e r y s m a l l displacement. This b e l t of gentle open f o l d s i s a con t r a s t to the c l o s e l y f o l d e d and f a u l t e d area to the ea s t . F a u l t s . The f a u l t s of the area f o l l o w c l o s e l y the s t r i k e of the r o c k s • Nowhere have f a u l t s , w i t h s t r i k e s c u t t i n g s t r a t a at angles of more than few degrees, been observed. These f a u l t s dip westward. In many cases the d i p has not been determined. Some of these f a u l t s have a displacement of thousands of f e e t . In every case o f much movement the west s i d e has "been u p l i f t e d w i t h regard to the east s i d e (see F i g * b ypage 71). Where there has "been much displacement the rock near the f a u l t - c o n t a c t has "been l i t t l e d i s t u r b e d . Gn the other hand the s m a l l e r breaks are o f t e n accompanied by inte n s e f o l d i n g . Evidences of f o l d i n g , i f i t did not go to depth, would be removed by e r o s i o n from the l a r g e r breaks. Thrust f a u l t s . , There are' three f a u l t s of l a r g e displacement which are o v e r t h r u s t s . They are: (1) The Pebisko f a u l t . This f a u l t extends to the western edge of the Disturbed B e l t i n the v i c i n i t y of Pebisko creek. I t s existence i s d i f f i c u l t to prove as much of the bedrock i s con-cealed; but i s i n f e r r e d as the Blairmore sandstones both under-l i e and o v e r l i e the Benton s h a l e s . The marked i r r e g u l a r i t y of the s t r i k e and dip a l s o i n d i c a t e s a f a u l t . (2) The Rowe f a u l t . The Rowe f a u l t occupies a s i m i l a r p o s i t i o n at the western edge of the Disturbed B e l t i n the v i c i n i t y of the Gldman r i v e r . Here the Kootenay and the base of the Blairmore have been ov e r t h r u s t on the B e l l y r i v e r formation. The r e l a -t i o n s i n d i c a t e a very f l a t d i p f o r the f a u l t - p l a n e . To the south the ov e r t h r u s t p a r t of the f a u l t ends a b r u p t l y against 1 h i l l s to the B e l l y r i v e r f o r m a t i o n . Stewart suggests that the ~ l ~ S t e l g a r t , J.S. G.S.cTlfe¥7Tl2T~P.50. ' " B e l l y r i v e r f ormation previous to the o v e r t h r u s t i n g was rough and that e i t h e r (a) the ol d e r rocks were o v e r t h r u s t and superimposed on -74- • the p r e - e x i s t i n g h i l l s and have s i n c e "been eroded away due to t h e i r g reater e l e v a t i o n ; or (b) the p o i n t s of highest r e l i e f on the o l d land s u r f a c e acted as a h a r r i e r to the o v e r t h r u s t . ^3) The l e w i s o v e r t h r u s t . This great f a u l t has been traced f o r 135 miles and has a probable c o n t i n u a t i o n of 50 m i l e s more. • 1 Rose and Mackenzie have shown i t to be an " i n t e g r a l p a r t of l~See M a c T i n i i e T T ^ . T.R.'S.C. Vol.XvT. T92"2. p.112. the s t r u c t u r e of the mountains themselves and i s not found only where the mountains j o i n the p l a i n s . " As such i t was discussed under a separate heading (see page 68). 2' Stewart o f f e r s the f o l l o w i n g i n t e r e s t i n g e x p l a n a t i o n 2 Stewart. J.S. G.S.C. Mem.112, p.51. ' ~ ~ ~ f o r the very gentle dips s t r e t c h i n g along the foo t of the Clarke range i n a b e l t 6 to 8 miles wide. These broad undu-l a t i o n s are i n marked contrast to the i n t e n s e l y f o l d e d and f a u l t e d s t r a t a to the east. He s t a t e s t h a t the o v e r t h r u s t rocks of the Lewis s e r i e s o r i g i n a l l y extended 6 to 8 m i l e s east of t h e i r present outcrops. I f the break along the Lewis f a u l t - p l a n e took place before there was much f o l d i n g i n the Cretaceous sediments, the superposing of the heavy load would make the Cretaceous s e d i -ments ,under the o r i g i n a l overthrust,competent to withstand the s t r e s s e s and r e s i s t a n t to f o l d i n g . The s t r e s s e s then would be transmitted to the uncovered Cretaceous s t r a t a f u r t h e r east, there causing intense f o l d i n g and f a u l t i n g . Subsequent e r o s i o n has removed the over t h r u s t Lewis s e r i e s and has now - 7 5 -uneovered the Cretaceous f o r a di s t a n c e 6 to 8 miles west of i t s outcrop at the clo s e of the Laramide R e v o l u t i o n . This g i v e s a sequence of events as f o l l o w s (a) Probable broad gentle f o l d i n g of the Cretaceous. (b) O v e r t h r u s t i n g of o l d e r rocks along the Lewis Thrust. (c) Intense f o l d i n g of the Cretaceous to the east of the o v e r t h r u s t . ^d) F a u l t i n g of the Cretaceous to the east of the over-t h r u s t . (e) Subsequent e r o s i o n of the o v e r t h r u s t and removal of a s t r i p of the o v e r t h r u s t block 8 m i l e s i n wi d t h . I t i s to be noted that t h i s e x p l a n a t i o n gives the Lewis Thrust an o l d e r age than the other t h r u s t f a u l t s of the Di s t u r b e d B e l t which are younger than the f o l d i n g . S t r u c t u r e i n the Crowsnest Coal Area, A l b e r t a . S t r u c t u r e s i n t h i s d i s t r i c t show remarkably w e l l the r e s u l t s of t h r u s t i n g from the west i n the B u i l d i n g of the 1 Rockies. Rose and Leach have made a g e o l o g i c a l map of the 1 Rose, B. G.S.C. Summ.Rept. 1912. area w i t h an accompanying b a t t e r y of s t r u c t u r e s e c t i o n s , Throughout the area t y p i c a l f o o t h i l l s s t r u c t u r e i s found. In the area two P a l a e o z o i c o u t l i e r s , the L i v i n g s t o n e range and T u r t l e mountain, b r i n g the Devono-Carboniferous limestones to the s u r f a c e . These more r e s i s t a n t rocks form the higher ranges; l e s s r e s i s t a n t r o c k s , l i k e the Crowsnest v o l c a n i c s and the Kootenay and Blairmore sandstones form lower r i d g e s while the s o f t e r shale formations outcrop i n the hollows between the P l a t e IX T h R ^ l a A r m o r e Map-area (Crowsnest_Pass).. ( a f t e r Leach & Rose.) r i d g e s . _The_ accompanying map, P l a t e IX,...shows t h a t the t r e n d of the formation outcrops i s i n a north-south d i r e c t i o n p a r a l -l e l to the s t r i k e of the mountains to the west. The s t r a t a , o r i g i n a l l y f l a t - l y i n g , have been f o l d e d and f a u l t e d by the t h r u s t from the west so that now the b e v e l l e d edges of the v a r i o u s s t r a t a are exposed on the limbs of the f o l d s or f a u l t -b l o e k s . R e p e t i t i o n of a formation i n an east-west d i r e c t i o n i n d i c a t e s a f o l d or f a u l t between the two outcrops. Where f a u l t i n g has occurred the beds i n each f a u l t block commonly d i p s t e e p l y t o the west • .: where f o l d i n g i s the rule' the rocks dip e i t h e r t o the west or to the east! according to t h e i r p o s i t i o n of the limbs of a n t i c l i n e s o.'r s y n c l i n e s . 1 Rose found t h a t the t h r u s t which upheaved the Rocky Rose, B. idem. " ~" mountains formed f o l d s at f i r s t , "When the f o l d i n g had reached the bending l i m i t of the more massive r o c k s , breaks occurred on the steep eastern limbs of a n t i c l i n e s and the rocks,at such places,were t h r u s t over those to the east by f a u l t i n g . I n places l i k e t h a t between Blairmore and Coleman, where there i s found only westward-dipping rocks repeated by f a u l t i n g , there were, at one t i m e , huge f o l d s , but e r o s i o n has removed vast q u a n t i t i e s of the deformed rocks and what i s exposed at the surface today i s only the westward-dipping 1imbs of f a u l t e d f o l d s . ' 1 Both the f a u l t s and f o l d s tend to play out along the - 7 7 -s t r i k e , w h i l e a f a u l t commonly ends i n a f o l d or v i c e v e r s a . The axes of f o l d s may j o i n . Sometimes, e s p e c i a l l y i n s h a l e s , a f a u l t ends without f o l d i n g , the movement being taken up i n the s o f t rock by s l i p p i n g i n s t e a d of f o l d i n g . Thus the exact l o c a t i o n or end of the f a u l t cannot be determined. •1 Rose emphasizes th a t i n a l l cases the breaks or 1 Rose . B. T.C.I.M.M". , part o f T o l . X X Y l T 7 " l 9 2 4 . " ~ deformations were caused by a t h r u s t from the west, so t h a t the rocks from the west have been pushed upwards and eastward w i t h respect to the rocks on the e a s t . The only case i n which t h i s does not h o l d i s on the west side of the H i l l c r e s t b a s i n . The f a u l t which passes west of H i l l c r e s t b a s i n and cuts o f f the Frank coal seams i s the o n l y f a u l t known i n the area where the rocks on the east s i d e have moved upwards w i t h respect to the rocks on the west s i d e . This Rose has e x p l a i n e d 2 Rose, B. idem. " • • i n the f o l l o w i n g paragraph as r e s u l t i n g from the same t h r u s t from the west. • • "At H i l l c r e s t the c o a l seams can be t r a c e d around the end of a spoon-shaped b a s i n where they come to the surface i n a south-plunging s y n c l i n e . To the east o f t h i s b a s i n there i s one of the o r d i n a r y t h r u s t - f a u l t s where the west s i d e has been pushed up and over the east and t h i s ' f a u l t when f o l l o w e d n o r t h -ward j o i n s the f a u l t from the west side of the b a s i n i n a jumbled area of much-broken rock towards Frank s l i d e . One mile f u r t h e r n o r t h , at Frank, along the t r e n d of the rocks there i s a l s o a s y n c l i n a l b a s i n but here i t i s not broken by f a u l t i n g . The e x p l a n a t i o n appears to be t h a t , at one stage i n the f o l d i n g of the rooks, the s y n c l i n e at Frank and that at H i l l c r e s t were continuous. With f u r t h e r t h r u s t the sh o r t e n i n g was taken up i n the v i c i n i t y of Frank by movement on the l a r g e f a u l t which passes east of B l u f f and T u r t l e mountains, but towards H i l l c r e s t h i s f a u l t p l a y s out, and here the movement i s taken up along the two f a u l t s , one on each s i d e of the H i l l c r e s t b a s i n . The s y n c l i n e here was f o r c e d b o d i l y upward as a bl o c k by great pressure at depth and broke away from i t s northward c o n t i n u a -t i o n along the two f a u l t s which end i n the area of jumbled rock towards Frank s l i d e . The movement here along the f a u l t on the west s i d e of t h i s forced-up block was that the east side moved upward w i t h respect to the west s i d e . Both f a u l t s p l a y out to the south, the one on the west side i n Fernie s h a l e s , and the one on the east s i d e i n an overturned a n t i c l i n e . " The above q u o t a t i o n i s of s p e c i a l i n t e r e s t i n t h a t i t shows how a normal f a u l t may r e s u l t from compression when adjacent f a u l t b l o c k s are t h r u s t from t h e i r o r i g i n a l po s i t i o n and the block on the foot w a l l of the f a u l t plane has undergone gr e a t e r movement. Another prominent f e a t u r e of the Blairmore area i s the T u r t l e mountain a n t i c l i n e . Sect ions of t h i s map i l l u s t r a t e another general f e a t u r e of the r e g i o n connected w i t h t h i s a n t i c l i n e (see F i g . 7)• This shows that the western limb of the a n t i c l i n e i s formed of s t e e p l y d i p p i n g f a u l t b locks of repeated s t r i p s of s t r a t a , whereas the eas t e r n limb i s more fo l d e d than f a u l t e d . The southern c o n t i n u a t i o n of t h i s - 7 9 -T u r t l e mountain F i g . ?a Cretaceous - green J u r a s s i c - y e l l o w Devono-Carboniferous - blue a n t i c l i n e e x h i b i t s a s i m i l a r though l e s s pronounced r e l a t i o n of 1 a steeper western and a f l a t t e r e a s t e r n l i m b . Mackenzie 1 Mackenzie, J.D. T.R.S.C., V o l . l b , 1922, p.110. b e l i e v e s t h i s e f f e c t would be caused, l e a v i n g the f a u l t i n g out of c o n s i d e r a t i o n , by the westward r o t a t i o n of a p r e v i o u s l y formed symmetrical a n t i c l i n e . The Bighorn and Mountain Park Coal B a s i n . The Bighorn coa l f i e l d i s bounded, on the west, by the F i r s t range of the Rockies and, on the ea s t , by the Bighorn range. The b a s i n s t r u c t u r e (see P l a t e X, page 8 0 ) continues from the North Saskatchewan r i v e r n o rth to beyond Mountain 2 Park. G.S. M a l l o c h has d e s c r i b e d that part of the b a s i n south 2 M a l l o c h , G.S. G.S.C. Mem.9E., p.39* of the Brazeau r i v e r . The Mesozoic s t r a t a of the b a s i n l i e i n a s y n c l i n e , the e a s t e r n limb of which forms the f a u l t block of the Bighorn range. Along the western margin of the b a s i n the s y n c l i n e i s , P l a t e X. (Joed /Ireas ' / Bighorn 2 Brazeau 3 Nikanassin 4 Muskikf Lake 3 Cadomin-Luscar Yairie Creek 7 Brule Mines 8 rocahontas-Moosehorn 9 Thare&u Creek 10 Wiidhay River 11 Smoky River 12 CosUspur District F o o t h i l l s S t r u c t u r e between the Saskatchewan and. Smoky R i v e r s . ( a f t e r KacKay.) - 8 0 -i n p l a c e s , c o n s i d e r a b l y overturned and i s overridden by the P a l a e o z o i c s t r a t a of the F i r s t or Front range of the Rocky mountains (see F i g . 7 , below.) F i g . 7b ( a f t e r Malloch.) Cretaceous - green T r i a s s i c - brown Devonian - blue J u r a s s i c - purple Permian - grey The Bighorn and F i r s t ranges of the Rocky mountains are huge f a u l t b l o c k s t i l t e d and t h r u s t to the northeast so that the Devonian limestones at t h e i r base have ove r r i d d e n ythe J u r a s s i c and Cretaceous rocks of the b a s i n . Along the south-western side of the b a s i n the d i f f e r e n t Mesozoic s t r a t a present i n the area come i n t o d i r e c t contact w i t h the limestone beds at the base of the F i r s t range. Along the eastern side of the Bighorn range, the throw of the o v e r t h r u s t f a u l t i s g r e a t e s t near the middle and decreases r a p i d l y towards the ends. At the southern e x t r e m i t y of the range the g r e a t l y decreased throw i s the probable cause of a change i n the d i p of the beds, f o r the southwest d i p , general throughout the range, changes to the south w i t h i n 5 miles of the end of the range. -81-The angle of dip i n the Bighorn range v a r i e s from ,.. o 0 60 t o 35 • The d i p s decrease g r a d u a l l y westward u n t i l the a x i s of the s y n c l i n e i s reached. To the west of the a x i s the change i s abrupt. The s t r a t a on the west side of the s y n c l i n e are n e a r l y v e r t i c a l or o v e r t u r n e d , i n some cases so much so as to give southwest d i p s of as low as 60 , making these beds • p a r a l l e l to those i n the Bighorn range. The sharpness of the f o l d has r e s u l t e d i n the t h i n n i n g out of the s o f t e r shale and crumpling of the harder beds. The main s y h o l i n e has been t r a c e d from the Saskatche-wan to the Brazeau. The s t r i k e of i t s a x i s v a r i e s from place to p l a c e ; thus the deepest part of the s y n c l i n e i s not always near the F i r s t range. I n the v i c i n i t y o f the Saskatchewan r i v e r the a x i s i s n e a r l y h o r i z o n t a l . From there to the B i g -horn r i v e r the s y n c l i n e p i t c h e s northwest, showing a gradual deepening of the b a s i n to the n o r t h . This i s f o l l o w e d by a f l a t s t r e t c h but at the Brazeau r i v e r the plunge i s again to the northwest. 1 M a l l o c h s t a t e s t h a t the Front range shows many 1 M a l l o c h , G.S* idem. crumbles. The s t r a t a of the Bighorn range are more r e g u l a r but overturned a n t i c l i n e s have been observed t h e r e . In the deep s y n c l i n e minor f l e x u r e s o f t e n cause a v a r i a t i o n of d i p . At one place i n the v a l l e y of the Bighorn the western limb of the s y n c l i n e f l a t t e n s out g i v i n g a much wider exposure of the Kootenay c o a l - b e a r i n g formation. A number of l i n e s o f sharp crumples w i t h some small f a u l t s have a f f e c t e d the s t r a t a i n - 8 2 -the s y n c l i n e . Mountain Parle. T h i s i s the n o r t h e r n c o n t i n u a t i o n of the same b a s i n . The lower Devonian beds of the Front range have been t h r u s t f o r s e v e r a l m i l e s over the Mesozoic sediments of the b a s i n which range p r o g r e s s i v e l y from T r i a s s i c beds at the western end of the b a s i n to Upper Cretaceous sediments at i t s c e n t r e . ^ T l f e c K a y , B.R. T.C.I.M.M. , Oct. 1930, P«4?2. ' ""*" Near the Brazeau r i v e r the v e r t i c a l displacement along t h i s f a u l t approximates 18,000 f e e t . The s y n c l i n a l a x i s o f the basin c o n t i n u i n g n o r t h from the Bighorn area disappears under the o v e r r i d i n g P a l a e o z o i c f a u l t - b l o c k at Mt. Mackenzie. Some distance to the no r t h i t reappears and i s t r a c e a b l e to beyond Whitehorse creek. At the n o r t h w e s t e r l y edge of the b a s i n the o beds are overturned, showing reverse dips up to 45 , f o r some distance to the east of the f a u l t plane. This suggests that at the northwestern edge of the b a s i n r e l i e f was by over-turning r a t h e r than by o v e r t h r u s t i n g . Near the centre o f the b a s i n the Upper Cretaceous beds d i p g e n t l y under the moderately d i p p i n g P a l a e o z o i c s of the Front range. From the above evidence i t seems c l e a r that the Cretaceous beds of the b a s i n had been f o l d e d i n t o a s y n c l i n e before the o v e r t h r u s t i n g of the P a l a e o z o i c limestone occurred. Also, i t appears ... ; that there has not been a great deal of e r o s i o n of the Cretaceous s t r a t a of the b a s i n since the o v e r t h r u s t i n g . - 8 3 » S t r u c t u r e i n the F o o t h i l l s Region to the East of the B i g -horn, N i k a n a s s i n and Brazeau Ranges. C h a r a c t e r i s t i c of the F o o t h i l l s B e l t the deformation i n t h i s r e g i o n i n c r e a s e s from east to west. R e l a t i v e l y open f o l d s of Cretaceous rocks are found i n the east; proceeding westward the f o l d s are c l o s e r , more numerous, and f a u l t i n g i s prevalent. In g e n e r a l , as one t r a v e l s westward, s u c c e s s i v e l y lower s t r a t a are brought to the s u r f a c e . The increased deform-a t i o n to the west has exposed the P a l a e o z o i c s t r a t a i n i s o l a t e d mountain o u t l i e r s along the western edge of the F o o t h i l l s b e l t . These ranges are due p a r t l y to s t r u c t u r e and p a r t l y to the erosion of the s o f t e r o v e r l y i n g Cretaceous beds. The area under c o n s i d e r a t i o n i s bounded on the west by three such out-l i e r s : the Bighorn, Nik-anas s i n , and Brazeau ranges (see P l a t e X, page 8 0 ) . The s t r u c t u r e i s d e s c r i b e d from east to west across the area. C h a r a c t e r i s t i c s t r u c t u r e s e c t i o n s are shown i n P l a t e X I , page 83* Throughout the eastern part of the area the beds d i p to the east away from the mountains and i n t o t h e • A l b e r t a geo-s y n c l i n e . But at a point of approximately 16 to 20 m i l e s to the east o f the P a l a e o z o i c o u t l i e r s , mentioned above, there i s a sudden change; from there westward the prevalent d i p is: t o -wards the mountains. This sudden r e v e r s a l of d i p i s c o i n c i d e n t throughout the area w i t h the L o v e t t F a u l t . (See P l a t e X,- p . 8 o ) . 1 A l b e r t a S c i e n t i f i c and I n d u s t r i a l Research C o u n c i l , Repts. b, L ; 9» 11* This f a u l t marks the major s t r u c t u r a l break t o the west. The Xovett f a u l t has been t r a c e d from the North -84-Saskatchewan to the Athabasca r i v e r . A l l beds n o r t h of t h i s f a u l t have a northeast d i p while those ot the south have, i n ge n e r a l , a southwest d i p . The movement has been g r e a t e s t along ends of the f a u l t , a:displacement of at l e a s t 3 0 0 0 feet being known at the Athabasca. Near the centre of i t s known l e n g t h , the t h r u s t i s f a r l e s s and along the Embarras r i v e r the f a u l t 1 goes i n t o a f o l d w i t h l i t t l e f a u l t i n g . 1 A l b e r t a Sci7& Ind.Res.Sounc., Rept.11. The Chungo f a u l t i s another w e l l d e f i n e d break. I t has been t r a c e d from the Saskatchewan to the Pembina r i v e r where i t forms the e a s t e r n border of a t h r u s t block o f Colorado sediments. To the n o r t h at the Pembina r i v e r i t f i r s t changes in t o an a n t i c l i n e , then m o d i f i e s i n t o a monocline and f i n a l l y dies out near Gregg r i v e r . To the west of t h i s f a u l t and i t s n o r t h e r n extension as an a n t i c l i n e l i e s an asymmetrical s y n c l i n e w i t h many minor f o l d s , e s p e c i a l l y along the western limb. In the south another f a u l t again b r i n g s the Colorado to the s u r f a c e . But to the north i t f i r s t passes i n t o a sharp a n t i c l i n e , then d i e s out f o r , i n the v i c i n i t y of the Athabasca the whole area to the east i s occupied by a s y n c l i n e . Between the Saunders formation to the east and F o l d -ing mountain to the west there l i e s a b e l t of s o f t Colorado shales. These s o f t rocks have y i e l d e d to f o l d i n g r a t h e r than to f a u l t i n g and the s t r u c t u r e s t h e r e i n have only a l o c a l s i g n i f i c a n c e . F o l d i n g mountain i s a n t i c l i n a l i n s t r u c t u r e and from the s e c t i o n along the Athabasca (see page 117) i t appears . - 8 5 - . .• • to be j o i n e d by a s y n c l i n e to the a n t i c l i n e at Roche a P e r d r i x . The Kootenay s t r a t a exposed on F o l d i n g mountain are c o n t o r t e d i n t o minor f o l d s . I t i s bordered on the east by a t h r u s t f a u l t of considerable displacement. The general s t r u c t u r e i s a n t i c l i n a l w i t h a plunge to the south. 1 R u t h e r f o r d found t h a t F o l d i n g mountain d i d not have I". R u t h e r f o r d , R . l . S.I.R.C.A. , Rept. No.11, p . 2 l . a c o u n t e r p a r t , i n s t r i k e alignment w i t h i t , on the northwest side of B r u l e l a k e , i . e . across the A t h a b a s c a . v a l l e y . The s t r u c t u r e s between F o l d i n g mountain and B r u l e l a k e are d i f f i -c u l t to i n t e r p o l a t e s i n c e recent d e p o s i t s cover p r a c t i c a l l y a l l the r o c k s . . 2 Dowling , i n d i s c u s s i n g the c o a l f i e l d s of Jasper Z Dowling,D.B. G.S.C. Summ.Rept. , 1910, p.150. "*" Park noted t h i s l a c k of alignment of s t r u c t u r e on the n o r t h and south side of B r u l e l a k e . To account f o r t h i s he put forward two suggestions: e i t h e r , that there was a r a p i d plunge of the a x i s of F o l d i n g mountain northward, o r , that there was a transverse break across the outer ranges i n the v a l l e y of the Athabasca. R u t h e r f o r d found, on t r a v e r s i n g the n o r t h and south ends of F o l d i n g mountain, that the a x i s d e f i n i t e l y dipped t o the southeast away from the Athabasca v a l l e y , and that the massive Saunders sandstone outcropping at l e a s t 5 miles to the northeast of F o l d i n g mountain had not been d i s p l a c e d by a transverse f a u l t , and a l s o that the s t r a t a at Entrance, 5 miles to the west of F o l d i n g mountain, were continuous across the Athabasca v a l l e y and on the h i l l s to both the north and south. -86-To account f o r t h i s l a c k of c o n t i n u i t y of s t r u c t u r e across the • 1 Athabasca v a l l e y at t h i s point Rutherford suggests: " I f a 1 R u t h e r f o r d , R . l . op. c i t . , p.22. t r a n s v e r s e f a u l t occurred at F o l d i n g mountain or at the s i t e of the present v a l l e y of the Athabasca through the f r o n t ranges, i t s i n f l u e n c e was d i s s i p a t e d i n the Colorado shales before reaching the Saunders beds to the east. Unless a t r a n s -verse f a u l t i s assumed the only a l t e r n a t i v e suggestion i s , t h a t the l a c k of c o n t i n u i t y of the F o l d i n g mountain s t r u c t u r e w i t h that to the northwest i s due to a s e r i e s of f o l d s and f a u l t s of short l a t e r a l extent which are not exposed. The steep n o r t h face of F o l d i n g mountain, w h i l e perhaps i n d i c a t i v e of a cross f a u l t i n g , appears to be more of an e r o s i o n a l f e a t u r e . " ••2 • C o l l e t c o n s i d e r s the l a c k of s t r u c t u r a l c o n t i n u i t y 2 C o l l e t , i.W. E x t r a i t du Compte Rendu de l a Societe de Physigue, e t c . , Vol.47 , No.2, 1930, p.80. across the v a l l e y of the Athabasca i s caused by a s y n c l i n a l i n f l e x i o n of the axes of f o l d i n g , i . e . by a transverse f o l d . S i m i l a r s t r u c t u r e s form some of the v a l l e y s i n the A l p s . He s t a t e s : " l a r i v i e r e Athabasca s o r t des montagnes Rocheuses par une v a l l e e qui s u i t une i n f l e x i o n s y n c l i n a l e de l'axe des p l i s . Nous retrouvons done l a un cas semblable a, ceux d e c r i t s par Maurice lugeon pour, c e r t a i n e s va11ees de s o r t i e des A l p e s . " I t i s a notable f e a t u r e that i n the Athabasca v a l l e y s t r u c t u r a l deformation has not brought the Colorado beds to the surface n e a r l y as f a r to the east as i n the f o o t h i l l s to the south. Although the v a l l e y of the Athabasca i s 1000 f e e t lower than the corresponding s t r i k e p o s i t i o n s on the Gregg or . . •• •• . - 8 7 -Mcleod r i v e r s . Here a long b e l t of Colorado sediments outcrops s e v e r a l m i l e s to the east of the s t r i k e c o n t i n u a t i o n of the most e a s t e r l y outcrop on the Athabasca. Rutherford suggests that there has been more o v e r t h r u s t i n g of the Pal a e o z o i c onto the Cretaceous i n the v i c i n i t y of B r u l e lake than to the south-west, where the E l k a n a s s i n range and F o l d i n g mountain l i f t e d the Cretaceous rooks to r e l a t i v e l y h i gher l e v e l s . Smoky R i v e r , The limestone f r o n t ranges of the Rockies continue .-• 1 north from the Athabasca across the Smoky and Hay r i v e r areas. "1 McVicar, J . G.S.C. Summ.Rept. 19-3» Pt.B, p .3Ju ~ In the Smoky r i v e r c o a l area the s t r u c t u r e i s an a n t i c l i n e w ith minor superimposed f o l d s . 2 MacKay s t a t e s that the asymmetrical a n t i c l i n e s of Z McKay, B.R. " 1T.C.1.M.M. , Oct. 1930, p . 3 0 b » the area have southern or i n n e r limbs s t e e p l y i n c l i n e d to overturned, w h i l e the. n o r t h e r n outer limbs are g e n t l y s l o p i n g . From t h i s evidence and from the f a c t that i n the Lovett f a u l t -to the south the upthrow i s , i n places.on the east s i d e , he concludes t h a t the t h r u s t s that developed these s t r u c t u r e s came from the p l a i n s and the A l b e r t a g e o s y n c l i n e . The same co n d i t i o n s might r e s u l t l o c a l l y from the r o t a t i o n ; of a symmetrical f o l d . They need not n e c e s s a r i l y be the r e s u l t of a t h r u s t from the east. - 8 8 -S p e c i a l cases of s t r u c t u r e i n the F o o t h i l l s B e l t encoun-t e r e d i r i the t r a c i n g •'•.aria mining of c o a l seams. ' • '.'1 "'• Rose has, from h i s work i n the Blairmore a r e a , made Rose, B. " S t r u c t u r e i n the "Crowsnest Coal Areas 1 6 •  T.'CVr.TOST V •:. . : ' -. .Vol. 27, 1924. a study of s p e c i a l s t r u c t u r e s a f f e c t i n g mining i n the f o o t h i l l s Because of t h e i r i n t e r e s t from an economic p o i n t of view these are o u t l i n e d "below. (1) S t e e p l y p i t c h i n g seams. The only s t r u c t u r a l d i f f i c u l t y met i n such seams i s i f the p i t c h i s too steep or too g e n t l e . In the former case the c o a l , descending "by g r a v i t y to the haulage l e v e l s , i s apt to "be "badly broken. In the l a t t e r , sheets of i r o n are o f t e n used, when p o s s i b l e , t o f a c i l i t a t e the running of the c o a l . (2) Small t h r u s t f a u l t s . (a) Those where a f a u l t cuts r a t h e r d i r e c t l y across a seam. I n places on the westward d i p p i n g coal-seams breaks of a few f e e t occur where the west s i d e has been moved upwards with respect to the east. I n many cases there i s l i t t l e i n d i -c a t i o n of a break at the surface as the movement has been taken up by s l i p i n shale beds. I f the displacement does not exceed 5 or 10 f e e t t r a c e s of c o a l are found along the s l i p and the c o n t i n u a t i o n of the seam to the eastward i s found by l e s s e n i n g the slope of the room. (b) Those where the f a u l t plane i s n e a r l y p a r a l l e l to the bedding f o r some d i s t a n c e . Where the c o a l has served as a s l i p plane f o r a f a u l t the coal may be completely dragged out so t h a t the foot and hanging w a l l of the seam are touching. - 8 9 -Commonly the f a u l t does not l i e i n the c o a l seam f o r any great distance so t h a t the c o n t i n u a t i o n of the coal seam i s found by •following up the f a u l t plane. Although the s l i p may be only a few f e e t the seam may be squeezed out f o r q u i t e a distance as i s the case w i t h No. 1 Seam, Be l l e v u e Mine, where along such a f a u l t the c o a l i s l a c k i n g f o r s e v e r a l hundred f e e t . ( 3 ) Large t h r u s t f a u l t s . I n t h i s case the seams are repeated at the surface and may outcrop at c o n s i d e r a b l e d i s t a n c e s a p a r t . Between Blairmore and Coleman the seams are repeated three times i n about 3 m i l e s . Here the seams of each f a u l t e d block are mined sep a r a t e l y and the problem i s to determine the depths to which the seams extend before running i n t o the next f a u l t plane• Where the f a u l t b l o c k s are l a r g e the c o a l may extend below mining depths but i n the s m a l l e r b l o c k s , where the f a u l t s out-crop only short d i s t a n c e s apart the tonnage i n any one f a u l t block w i l l be s m a l l . Sometimes a c o a l seam does not outcrop at the surface but i s cut o f f by a f a u l t at no great depth. A study of the s t r u c t u r e and the sediments may r e v e a l the b u r i e d seams. (4) Small f o l d s . F o l d s , even very small ones, d i f f e r from small f a u l t s i n that they can be detected at the s u r f a c e . As i t i s not p r a c t i c a l to c a r r y rooms across the tops of a n t i c l i n e s o r the bottoms of s y n c l i n e s rock t u n n e l l i n g must be done to reach the other limb of the f o l d . (5) (5) Large f o l d s . These are e a s i l y l o c a t e d at the surface and o f f e r no s p e c i a l d i f f i c u l t i e s i n mining. I n the case of a p i t c h i n g a n t i c l i n e or s y n c l i n e the l e v e l s curve around the plunging f o l d s . The d e t e r m i n a t i o n , from surface s t r u c t u r e , of the depth to the c o a l , b u r i e d i n a f o l d , i s not always a c c u r a t e , due to changes i n d i p at depth. However, i n the f o o t h i l l s r e g i o n , as there i s l i t t l e change i n d i p down to minable l e v e l s , the a c t u a l depths have been found to check very c l o s e l y w ith the c a l c u l a t e d depths determined from surface s t r u c t u r e . (6) D r a g - f o l d s . Drag f o l d s are found i n the f o o t h i l l s c l o s e t o the large f a u l t planes. Since the p r e v a i l i n g d i p of s t r a t a i n the f a u l t b l o c k s i s to the west and as the west side of the break was t h r u s t up and over the east s i d e , the movement has formed small drag a n t i c l i n e s on the western or hanging w a l l and s i m i l a r drag s y n c l i n e s along the eastern or f o o t w a l l . Thus when a f a u l t i s encountered the c o n t i n u a t i o n of the unbroken coal i s l i k e l y t o be found down the p i t c h i f on the west side of the f a u l t , and up the p i t c h i f on the east s i d e . (7) F a u l t s ending i n F o l d s . T y p i c a l of the f o o t h i l l s s t r u c t u r e , f a u l t s commonly occur where t h r u s t s have caused the rocks to break along the ste e p l y d i p p i n g east limbs of a n t i c l i n e s . Where the rocks are ste e p l y i n c l i n e d and not d i s p l a c e d , the s o f t rocks have been squeezed upwards or downwards towards the axes of the f o l d s . Coal being a s o f t rock i s l i k e l y to be squeezed out on the limbs and. thickened near the axes of the f o l d s . A l a r g e pocket of t h i s squeezed coa l may be found on the c r e s t s but r i s l i k e l y to be d i r t y as, i n the movement, shale may have mixed i n w i t h i t . As the f o l d i n g i s p r i o r to the f a u l t i n g the coal i s apt to be squeezed from the s t e e p l y d i p p i n g eastern l i m b s of a n t i c l i n e s whether f a u l t i n g has taken place or not. (8) F a u l t s ending i n s h a l e . Where a f a u l t cuts across the Kootenay formation i n the u n d e r l y i n g s h a l e , the exact l o c a t i o n and extent of the f a u l t cannot be determined as the movement i s taken up by s l i p p i n g i n the shale and the re i s no f o l d i n g to show the p l a y i n g out of the f a u l t . I I I . S t r u c t u r e along the Main Line of the C.P.R. and Adjacent Areas from the P l a i n s to the S e l k i r k Mountains. The work done i n t h i s b e l t y i e l d s the best cross s e c t i o n of s t r u c t u r e from the P l a i n s to the c r e s t o f the S e l k i r k s . F o o t h i l l s , Bow R i v e r S e c t i o n . The area along the Bow r i v e r extends across the foot h i l l s from east to west and consequently e x h i b i t s the s t r u c t u r e s c h a r a c t e r i s t i c of the f o o t h i l l s . The f o l d s and f a u l t s have the t y p i c a l northwest t r e n d p a r a l l e l to the Rocky mountains. There i s i n c r e a s e d deformation from east to west. In the e a s t e r n part the f o l d s are more open and there i s l e s s displacement along the f a u l t planes. ,In the western part of the area the p a r a l l e l s t r u c -ture i s c o n s i d e r a b l y m o d i f i e d by Moose Mountain, described on page 92* Around the c e n t r a l P a l a e o z o i c beds s u c c e s s i v e l y younger Mesozoic and Cretaceous beds outcrop i n roughly concen-t r i c arrangement. The e f f e c t of t h i s extends northwest across the Bow r i v e r . East of Cochrane on the C.P.R.,the s t r a t a are f l a t -l y i n g and undisturbed. To the west the s t r u c t u r e increases i n 1 complexity. R u t h e r f o r d has mapped twelve high angle t h r u s t 1 R u t h e r f o r d , R.K. S. & I.R.C. of A l b e r t a , Rept.No.17,"pp.10* • • • • : 19. f a u l t s i n a d i s t a n c e of 10 m i l e s west of Grand V a l l e y creek and s t a t e s t h a t the s t r u c t u r e i s f a r more complicated than i n d i c a t e d . I n the t h r u s t b l o c k s the s t r a t a dip to the west at 0 0 angles of 30 to 45 > This would seem to i n d i c a t e t i l t i n g of r e l a t i v e l y shallow b l o c k s . S i m i l a r o v e r t h r u s t s are described elsewhere i n the f o o t h i l l s . The accompanying s e c t i o n ( P l a t e X I I , page 92) from Turner V a l l e y to the south, g i v e s a good idea of the s t r u c t u r e of the r e g i o n . I t i s to be noted that the Bow R i v e r v a l l e y t r a v e r s e s the f o o t h i l l s where the u p l i f t has been r e l a t i v e l y l e s s . This i s a l s o c h a r a c t e r i s t i c of--. i • 2 . j . several of the l a r g e r streams. <i 2: Rutherford, R.K. As above, p.10. Moose Mountain Area. S t r u c t u r e s i n the Moose mountain area are t y p i c a l of MOOSE MOUNTAIN REGION LEGEND T e r t i a r y Cretaceous! Paskapoo Edmonton Bearpaw Benton, e t c . J u r a s s i c P a l e o z o i c Dakota Kootenay Fernie Ls. & q t z i t e F a u l t s ~93" the D i s t u r b e d B e l t to the east of the Rocky mountains. The area i s bordered on the west by the eas t e r n escarpment' of the Rocky mountains, where P a l a e o z o i c limestones and q u a r t z i t e s have been pushed over the Gretaceous rocks on a f a u l t plane dipping west, u s u a l l y at small angles. The o v e r t h r u s t i n g , as 1 s t a t e d by D.D. Cairnes , i s of the order of se v e r a l m i l e s . 1 C a i m e s , D.D. G.S.C. Mem.61. "Moose Mountain D i s t r i c t , Southern A l b e r t a " , p.33. The rocks of the r e g i o n are a l l more or l e s s f o l d e d , and overturned to the east. As i s c h a r a c t e r i s t i c of the Disturbed B e l t , o v e r t h r u s t f a u l t i n g to the east i s common. The movement took place along f a u l t planes having a no r t h w e s t e r l y s t r i k e and w e s t e r l y d i p - the l a t t e r o f t e n at low angles. The f a u l t s are more numerous and have g r e a t e r t h r u s t s c l o s e r to the Rocky mountain escarpment. The western l i m i t of the outcrop of the Edmonton formation f o l l o w s the eastern l i m i t of the Dis t u r b e d B e l t i n t h i s area. To the east the s t r a t a are quite even but the h i l l s are somewhat r o l l i n g f o r some d i s t a n c e . This i s probably the no r t h e r n c o n t i n u a t i o n of the Porcupine H i l l s . . The outstanding topographic and s t r u c t u r a l f e a t u r e s of the d i s t r i c t are the Moose mountain and Forgetmenot r i d g e s (see P l a t e X I I I , page 9 3 ) . They are immense f o l d s of Palaeo-z o i c limestone and q u a r t z i t e o v e r l a i n by Fernie shales and Kootenay rocks. The Moose mountain r i d g e i s an a n t i c l i n e w i t h a n o r t h e r l y plunge at the north end of the s t r u c t u r e and a south e r l y plunge .at the south end. This huge dome-like -9.4-s t r u o t u r e i s d e s c r i b e d as a quaquaversal by C a i r n e s " . The l' Cairnes , P.P. op. c i t . , p.33. s t r u c t u r e i s surrounded on a l l s i d e s by Cretaceous rocks. To the west and south of Moose mountain r i d g e l i e s the Forget-me-not r i d g e . This s t r u c t u r e i s separated from the Moose mountain s t r u c t u r e by a small s y n c l i n e of Mesozoic rocks and i s f a u l t e d along i t s e a s t e r n border, as shown i n P l a t e XIV, page 95• The f a u l t i n g appears to have taken place along the a x i s of an overturned a n t i c l i n e . To the south, on the n o r t h branch o f Sheep r i v e r , t h i s Forgetmenot t h r u s t f a u l t dies out i n t o an overturned a n t i c l i n e , A complete double f o l d has been formed and. then the top eroded o f f , as shown i n P l a t e XIV, S e c t i o n s 2 and J . This g i v e s a s e c t i o n of the Cretaceous formations i n reverse order. Whereas, to the n o r t h , the Cre-taceous rocks have had P a l a e o z o i c t h r u s t over them, to the south where f a u l t i n g has not occurred the rocks have been much fo l d e d and pushed hig h up i n t o the a i r . This great o v e r t u r n i n g has not o v e r f o l d e d the massive P a l a e o z o i c limestones and q u a r t z i t e s . In every case the o l d e s t formation i n v o l v e d i s the F e r n i e s h a l e s . These s o f t J u r a s s i c rocks acted as a " l u b r i c a t i o n " plane along which the s l i p p i n g took place (see P l a t e XIV, S e c t i o n 3 ) . As only the J u r a s s i c and Cretaceous s t r a t a are i n v o l v e d i n the o v e r f o l d i t f o l l o w s that the s t r u c t u r e s , as such, d i d not go to any great depth. The P a l a e o z o i c formations beneath were probably asymmetrically f o l d e d or s l i g h t l y overturned. What the adjustments were at depth, corresponding to the complete o v e r f o l d i n g at the s u r f a c e , 0^ * a CD « cn CQ CD Pi Pi •rH cd o R R Pi 0) O N P4 M M Pi -cj no - H r H PS "3 O - H +» H < H + ' t H H r-H O t»D 0) cd Pi <VH SS Pi O d CD d Ar> U U O <o <VH 03 CO 05 . Pi CO > CD •r< •¥> O cd <H R d o • o Pi O Pi •rH O +3 - H CQ CQ CD » H CD 03 o d cd co 03 4^ r H h O P i 01 O CD -H + » CO M Pi CO O Pi CD <VH O CD r H (H O 4=|i| ft CD Pi cd CD 03 r H EH O w co o o *=3 CO o M EH O CO e to CD CD CO d Pi CD HQ CD r H d i CO d o •rH + » O CD CO <M O a o •rH H-3 cd © o r H fH O fa \ \ d o • H H-3 O CD CO •) \\V MA d o •rH © CD CO :v..r^V - •.-95-;' ; i s d i f f i c u l t to e x p l a i n . Another feature o f i n t e r e s t i s the Cretaceous trough, known as P. Burns' c o a l f i e l d , l y i n g to the west of the E a s t e r n Escarpment and the F i r s t range of mountains. This b a s i n contains v a l u a b l e c o a l d e p o s i t s . As seen from P l a t e X I I I the re i s p r o b a b l y , i n the southern part of the b a s i n , a f a u l t along i t s western edge. To the n o r t h t h i s f a u l t i s r e p l a c e d by a f o l d where doubtless the P a l a e o z o i c s are t h r u s t over the Cretaceous thus l i m i t i n g the northern extent of the Cretaceous trough. I t i s noteworthy that t h i s r e l a t i o n of f a u l t i n g changing to f o l d i n g to the n o r t h i s the reverse of t h a t found i n the Forgetmenot r i d g e where the change i s to f o l d i n g i n the south. In c r o s s i n g the Cretaceous formations east of the Moose mountain r i d g e the f o l d i n g becomes l e s s overturned and more open as one t r a v e l s east. I n the Edmonton and Paskapoo formations the beds d i p evenly to the east i n t o the A l b e r t a g e o s y n c l i n e . Summary - Moose mountain area. (1) The s t r a t a were f i r s t c o n s i d e r a b l y f o l d e d e s p e c i a l l y i n the western part of the area. ( 2 ) P r o g r e s s i v e o v e r f o l d i n g to the east i n v o l v i n g the J u r a s s i c and Cretaceous rocks i n which the Fernie shales acted as a g l i d i n g plane. (3) Overthrust f a u l t i n g to the east along the axes of the i n c l i n e d f o l d s . The f a u l t planes dip about 45° S.W. (4) D e p o s i t i o n of the T e r t i a r y Paskapoo formation a f t e r © PM z o 51 o p < < z o h -o to o o o co > ca o5 < O ct si < < V, 0 &J LxJ ~ T ~ P a5 a *» to n o r-i • as 02 ca p, OJ • o CP o & 'A ¥ CO <M co c o o 33 -rH o © CO a +» o d ?H +» CO o a >> aJ OS © a5 el © © of U © (S3 5 co 05 © © o o © o 3 oo aJ CO © > •H CD O -H O •H £ •H 5>3 03 CO 03 CO © CO f-( as Pc< as Ph m -H CO in E-» CO S3 cJ o u © •H o as o as « O © Pi as •H U & H CO id as •H O •H > o o as "I as o as •H u a aj o © U completion of the mountain-building,, Sediments being, d e r i v e d from the e r o s i o n o f the newly formed Rockies. S t r u c t u r e S e c t i o n along Main l i n e o f C.P.R. - K i c k i n g Horse Pass and Bow R i v e r , The s e c t i o n along the C.P.R, has been d i v i d e d i n t o three b e l t s s i m i l a r to the d i v i s i o n made by Mackenzie f o r the southern Rockies, The outstanding d i f f e r e n c e i s that.whereas Daly has mapped the western b e l t along the 49th p a r a l l e l as normal f a u l t b locks w i t h p r o g r e s s i v e downthrow to?vfards the Trench, t h i s b e l t along the C.P.R. i s made up of c l o s e l y f o l d e d s t r a t a overturned and t h r u s t to the southwest. I f Daly's normal f a u l t s were high-angle t h r u s t s , as Shepard b e l i e v e s them to be, then the* s t r u c t u r e s i n the two areas are s i m i l ar i n o r i g i n , i . e . they are the r e s u l t of compressive s t r e s s e s a c t i n g from the centre of the Rockies. For a c r o s s s e c t i o n of Rocky Mountain s t r u c t u r e i n t h i s B e l t see P l a t e XV (page 9 6 ) and P l a t e XVI ( i n pocket). E a s t e r n B e l t of Thrust. As i s c h a r a c t e r i s t i c o f the Rockies the eastern part ; along the Bow r i v e r c o n s i s t s of a s e r i e s of narrow f a u l t b l o c k s , a l l c o n s i s t i n g of s t r a t a which d i p southwestward and a l l t h r u s t over one another to the no r t h e a s t . The g r a i n of the country o here s t r i k e s n o r t h 45 west. The d i p of the s t r a t a i n the 0 0 f a u l t b l o c k s i s i n many in s t a n c e s 30 - 50 to the southwest. The t h r u s t s u r f a c e s appear to be steep, s l o p i n g to the southwest at about the same angle as the d i p . The F r o n t a l Thrust. The t h r u s t i s w e l l exposed, at Kananaskis where the Bow r i v e r i s s u e s from the mountains. There the Middle Cam-b r i a n r e s t s on the Cretaceous g i v i n g a throw of approximately 10,000 f e e t , w i t h the plane of the th r u s t approximately h o r i -z o n t a l f o r over •§• m i l e . F i f t e e n m i l e s n o r t h of Kananaskis on the Ghost r i v e r the Lower Cambrian r e s t s upon approximately the same s t r a t a g i v i n g a throw of 11,500 f e e t . The o v e r r i d i n g here i s a t l e a s t 2 m i l e s . This f a u l t has been t r a c e d f o r at 1 Z • Z l e a s t 80 m i l e s . A l l a n , Raymond and W i l l a r d describe nine t h r u s t f a u l t s i n the eastern b e l t of Thrust b l o c k s . They are 1 A l l a n , J.A. G.S.C. Guide Book No.8, P t . I I , 1913. ~ 2 Raymond, P.E. & W i l l a r d , B. Jour, of Geol., V o l . 3 9 , 1931, _ pp.110-113. summarized i n the f o l l o w i n g t a b l e . I n a l l the t h r u s t planes there i s a steep d i p to the west (except i n the F r o n t a l t h r u s t ) and the s t r a t a i n the f a u l t b l o c k s dip to the south-west . Table 3« Thrust — Plane Displacement Formation u n d e r l y i n g f a u l t plane Formation o v e r l y i n g f a u l t plane F r o n t a l 10,000-12,000 Cretaceous Mid. Cambrian 1. Cambrian Minnewanka 45 2,500' Spray R i v e r T r i a s s i c Rundle l i m e -stone Inglesmaldie (Panther Or.) 6,ooo' 15,000' Spray R. Kootenay Minnewanka shale Minnewanka shale Standley 400 » ? Rundle Rundle Gasoade 17 ,ooo« Kootenay Cambrian Sulphur 10,000' T r i a s s i c Devonian E d i t h 6,ooo' Spray R, Minnewanka Sawback 1,000 ' Devonian Up. Gambrian Johnston 18,000* M i s s i s s -i p p i an -Pre-Cambrian The Johnston f a u l t marks the western boundary of the eastern p o r t i o n of the Rockies, the r e g i o n of t h r u s t s . Eleven more or l e s s notable breaks are encountered i n passing about 35 m i l e s across the s t r i k e • S i x of these have displacements of 6000 f e e t or over. They extend from 10 to 60 miles or over along the s t r i k e . Yet as t h r u s t s they are not r e a l l y impor-tant f o r there appears to be comparatively l i t t l e o v e r r i d i n g . •• - 9 : 9 - - -Eight of the t h r u s t s , i n c l u d i n g such important ones as the Cascade and Johnston, have been found to die out i n f o l d s at one or both ends. A l l except the F r o n t a l are so steep t h a t there i s l i t t l e suggestion that one block has rid d e n f a r over another, f o r i f they had done so, eastwardly bowed ares i n the t r a c e s of the f a u l t s would have been produced. These do not e x i s t . T h i s , t h e r e f o r e , not a r e a l "schuppen" s t r u c t u r e but s i m i l a r to one very commonly seen on a small scale i n s l a t e s , i n which breaks a few inches long are developed w i t h r e a l r e -verse f a u l t s which die out i n low f o l d s at e i t h e r end. Ray-1 mond s t a t e s t h a t these appear to be the r e s u l t of compression T~" op. c i t . , p.114. i n two d i r e c t i o n s . Gently Folded B e l t . West o f the Sawbacks, extending as f a r as the Van Horne range, a distance across the s t r i k e of about 25 m i l e s , i s a r e g i o n of a n t i c l i n e s and s y n c l i n e s w i t h low d i p s and occasion-a l normal f a u l t s . The f i r s t of these f o l d s i s the Cas t l e syn-c l i n e . To the; south of the Bow t h i s s y n c l i n e i s a v a l l e y but northwestward C a s t l e mountain i s i n i t s centre. Southwest of i t i s the Bow a n t i c l i n e which i s r e a l l y a great dome w i t h i t s highest p o i n t i n Mt. O l r i a n . So f a r as t h i s s e c t i o n i s con-cerned, t h i s i s the summit of the Rocky mountain g e a n t i c l i n e . • -• 2 Raymond s t a t e s : "The basa l Cambrian would, i f i t had not been 2 op. c i t . , p.ll5» . denuded from O l r i a n , have been there about 10,000 fe e t above s e a - l e v e l . This i n d i c a t e s a minimum of 30,000 f e e t as the - 1 0 0 -amount of u p l i f t i n t h i s dome sin c e the surface was p r a c t i -c a l l y at s e a - l e v e l i n l a t e Cretaceous times. 1 8 I n t e r e s t i n g s t r u c t u r e s occur i n the Pre-Cambrian Hector shale. Wherever the shale i s seen i n contact beneath the lower Gambrian q u a r t z i t e s i t i s evenly bedded and n e a r l y conformable, but, where i t outcrops on the surface i t i s very much d i s t u r b e d , showing many s h a r p l y f o l d e d a n t i c l i n e s , syn-c l i n e s and f a u l t s . I t has been suggested that t h i s may be due to the well-known creep which occurs when s o f t rocks are i n v o l v e d i n f o l d s between massive ones or due to the pressure of the superimposed massive beds surrounding the Pre-Cambrian area. , ••• Southwest of the Bow a n t i c l i n e i s the Bosworth s y n c l i n e along which occur such peaks as Mounts Whyte and V i c t o r i a . The Sherbrook f a u l t occurs along the a x i s of the s y n c l i n e . I t i s a small normal f a u l t with downthrow to the west. To the west i s the Yoho a n t i c l i n e broken by the Stephen Cathedral f a u l t of A l l a n . This f a u l t , described under the heading " F i e l d Map-Area", has a downthrow on the western side of over 3,000 f e e t . The break f o l l o w s the scenic Yoho v a l l e y and separates Cathedral crags from Mount Stephen. On the western side of t h i s peak the Stephen-Dennis f a u l t b r i n g s the s o f t shaly Upper Cambrian i n t o j u x t a p o s i t i o n w i t h the more massive Mid-Cambrian. I t i s supposed to be a g r a v i t y f a u l t but there i s some suggestion t h a t i t i s r e a l l y a t h r u s t towards the e a st. • ~ i o i - • ' • From here the wide O t t e r creek s y n c l i n e extends to the Van Horne range and i s f l o o r e d w i t h s o f t calcareous s h a l e s . They have s u f f e r e d severe compression and are p a r t i a l l y meta-morphosed. Western B e l t of Thrusts. In the Van Horne range the f i r s t of a s e r i e s of e a s t e r l y d i p p i n g o v e r t h r u s t s i s reached. Between the Van Horne range and the Dogtooth mountains west of the Trench, the re i s a b e l t of t e r r i t o r y 15 to 20 m i l e s wide i n which the dips are p r e v a i l i n g l y toward the e a s t , g e n e r a l l y very steep. The s t r a t a have been t i g h t l y f o l d e d and somewhat overturned towards the west. There are s e v e r a l t h r u s t s , the planes of 1 which d i p s t e e p l y eastward. Raymond i n c l u d e s i n t h i s b e l t , '1 ' op. c i t . , pp.I15"llb» """" ' — -the western part of the Van Horne range, the Beaverfoot and B r i s c o e ranges, the Rocky Mountain Trench and the eastern f l a n k s of the Dogtooth mountains. The g e o l o g i c a l s t r u c t u r e i s complicated. At l e a s t f o u r p r i n c i p a l t h r u s t s are shown but no one of them has a very great throw. A l l the rocks east o f the Trench.with the e x c e p t i o n of the Upper Or d o v i c i a n q u a r t z i t e and dolomite.are p r e v a i l i n g l y t h i n bedded, shaly and weak. This undoubtedly accounts f o r the complicated nature of the s t r u c t u r e . I t i s i n t e r e s t i n g to note that Rocky mountain s t r u c t u r e i s considered to extend across the Trench i n t o the Dogtooth mountains i n t h i s l a t i t u d e w h i l e f u r t h e r south i n the v i c i n i t y of S i n c l a i r , Shepard found P u r c e l l s t r u c t u r e to con-tinue east across the Trench i n t o the Rockies. '• . "102 - ' • ' • ' ' ' Summary. The s t r u c t u r e s e c t i o n i s divided, i n t o three b e l t s showing the f o l l o w i n g c h a r a c t e r i s t i c s : (1) E a s t e r n B e l t of Thrusts -F o l d i n g i n c l i n e d to the nort h e a s t . Narrow f a u l t b l o c k s t h r u s t i n g to the northeast d i p s o f f a u l t planes steep, exception F r o n t a l Thrust l a r g e displacements s t r a t a i n f a u l t b l o c k s d i p southwest. (2) Gently f o l d e d B e l t -25 m i l e s wide gentle a n t i c l i n e s - ;& s y n c l i n e s normal f a u l t s w i t h p r o g r e s s i v e downthrow towards centre of b e l t . (3) Western B e l t of Thrusts -15 to 20 m i l e s wide close f o l d i n g i n c l i n e d to southwest t h r u s t f a u l t i n g to the southwest small (known) displacements. S t r u c t u r e - F i e l d Map Area. Taken as a u n i t the s t r u c t u r e of the area i s mono-c l l n a l w i t h a general d i p towards the southwest 1, i . e . the 1 A l l a n , J.A. G.S.G. Mem.55: "Geology of the F i e l d Map-area." olde s t sedimentary rocks are exposed i n the northeast and the youngest i n the southwest i n the Beaverfoot range. P l a t e XVII. FULD MAP AREA. ( a f t e r A l l a n ) l e g e n d Quaternary S i l u r i a n O r d o v i c i a n G r a p t o l i t e shales Goodsir Upper Cambrian O t t e r t a i l C h a n c e l l o r " (shear zone) Sherhrookg^ c < Mid-Cambrian lower Cambrian Pre-Cambrian Igneous (Post Cre-taceous) F a u l t s o / e 3 -4 S 6 ©CXtfi ' - /"= •* M l . l i n e of s e c t i o n Fig, C.P.R. (main l i n e ) F a u l t s A - Stephen-Dennis B - Stephen-Cathedral C - Beaverfoot -103-As shown i n P l a t e X V I I , page 103, the ranges present i n the area are,from west to e a s t , the Beaverfoot, O t t e r t a i l and Bow ranges. The Van Home range n o r t h of the K i c k i n g Horse r i v e r i s the northern c o n t i n u a t i o n of the Beaverfoot and O t t e r t a i l ranges. Mt. Goodsir Stephen Cathedral F a u l t F i g . 8. Generalized s e c t i o n , F i e l d map area. F o l d i n g . (See F i g . 8 , above.) In the most w e s t e r l y or Beaverfoot range the s t r a t a are much f o l d e d and broken, sometimes g i v i n g the appearance of i s o c l i n a l f o l d i n g . As a r u l e the asymmetrical f o l d i n g i s overturned to the southwest. This intense f o l d i n g occurs only i n the area u n d e r l a i n by s o f t rock such as i n the O t t e r t a i l and Beaverfoot v a l l e y s and the Beaverfoot range. In the O t t e r -t a i l v a l l e y , near Mount Duchesnay, the f o l d i n g i s very c l o s e , showing, i n some cases, an i s o c l i n a l s t r u c t u r e w i t h f o l d s having a depth of over 2000 f e e t . The f o l d s g r a d u a l l y become g e n t l e r i n the v a l l e y and f l a t t e n out to a monoclinal s t r u c -ture i n the O t t e r t a i l range. In the Bow range, where i t i s not a f f e c t e d by f a u l t -i n g there i s a f a i r l y uniform d i p to the southwest, r e s u l t i n g i n the monoclinal s t r u c t u r e t y p i c a l of the area to the east. Not only do f o l d s w i t h the usual northwest t r e n d occur but there i s al s o s e v e r a l open a n t i c l i n e s w i t h a n o r t h -south a x i s . The f l a t a n t i c l i n e , i n the K i c k i n g Horse v a l l e y between Mt. Stephen and Mt.. F i e l d , i s of t h i s type. A l l a n 1 1 A l l a n , J.A. G.S.C. Mem.55, p.199. "" ~ suggests "that the p e r i o d of f o l d i n g i n the Rocky mountains was i n i t i a t e d by compressive s t r e s s e s which came from the east and west and t h a t l a t e r the major a x i s of compression became n o r t h -east and southwest, r e s u l t i n g i n mountain b u i l d i n g f o l d s of the f i r s t dimension." This would e x p l a i n the f l a t open north-south f o l d i n g i n the more massive rocks outcropping i n the eastern part of the map-area. These e f f e c t s would be masked by the intense northwest-southeast f o l d i n g i n the s o f t e r sediments to the west. The Ice R i v e r i n t r u s i o n has been di s c u s s e d i n d e t a i l : 2 by K i d d . The Ice R i v e r v a l l e y i s a n t i c l i n a l (see F i g . 8, page 2 K i d d , D.F. T h e s i s , u7BTc7T~l92b. ~ 102). The f o l d i n g was before the i n t r u s i o n but the i n t r u s i v e , l a c c o l i t h i c i n nature, f u r t h e r up-arched the s t r a t a . Cleavage. Shearing wlaich i s common i n the Chanc e l l o r formation i n O t t e r t a i l and Beaverfoot v a l l e y s i s l a t e r than the f o l d i n g . I t occurs i n the s o f t e r s t r a t a . I n the massive-bedded Cambrian q u a r t z i t e s to the East shearing i s found only i n the shaly - 1 0 5 -interbeds and does not extend i n t o the massive beds. There are s e v e r a l sets of cleavage planes, the p r i n -0 0 O n c i p a l ones having s t r i k e IT 65 - 75 W. and d i p 60 - 85 S.W. In the O t t e r t a i l v a l l e y these cleavage planes cut across the f o l d s showing,as s t a t e d above .that shearing i s l a t e r than the f o l d i n g and-also l a t e r than, or towards the close o f , the igneous i n t r u s i o n . J o i n t s . J o i n t i n g i s not common. The best examples are found i n the thick-bedded limestone where there are two planes of j o i n t i n g n e a r l y at r i g h t angles but not having any d e f i n i t e trend.: Faul t s. F a u l t s , normal i n c h a r a c t e r , are the most important s t r u c t u r a l f e a t u r e i n the F i e l d map-area. These normal f a u l t s are c h a r a c t e r i s t i c of the C e n t r a l B e l t o f the R©cky mountains and are i n contrast with the eastern p o r t i o n where o v e r t h r u s t -in g and reverse f a u l t s p r e v a i l • Two systems of f a u l t s are present: (1) northwest-southeast trends corresponding to the major a x i s of the mountain f o l d s . In t h i s type are i n c l u d e d most of the l a r g e r breaks, e.g. the Stephen-Dennis f a u l t . (2) f a u l t s having north-south t r e n d s , e.g. the Stephen-Cathedral f a u l t . These f a u l t s are younger than those w i t h a northwest s t r i k e because the Stephen-Cathedral f a u l t d i s p l a c e d the Stephen-Dennis f a u l t . The Stephen-Dennis f a u l t . (See P l a t e XVII and F i g . 8.) This f a u l t , named by A l l a n , i s the most important f a u l t i n the map-area having a northwest t r e n d . From the v a l l e y between Mt. Stephen and Mt. Dennis the f a u l t runs south-e a s t e r l y to • 0doray Pass and Park mountain. I t s course north of the K i c k i n g Horse r i v e r i s not known. The downthrow side i s to the west as shown i n F i g . 9» This f a u l t i s the eastern boundary of the zone of the sheared C h a n c e l l o r formation, u n d e r l y i n g O t t e r t a i l v a l l e y . On i t s n o r t h e a s t e r n or upthrow side are the massive Mid-Cambrian formations. A s i m i l a r normal f a u l t w i t h northwest s t r i k e and downthrow on the southwest side occurs on the west side of Mt. Hunter ( i n the Van Horne range east of L e a n c h o i l ) . The f a u l t plane i s n e a r l y v e r t i c a l . Another f a u l t w i t h northwest s t r i k e t r a v e r s e s the 1 northeast slope of the Beaverfoot range. A l l a n i n h i s 1 See Map 142A, S t r u c t u r e S e c t i o n C-D, accompanying G.sTcT " • Memoir 55 «> St r u c t u r e s e c t i o n shows t h i s as a reverse of t h r u s t f a u l t w i t h a northeast d i p . As he has s t a t e d that the f a u l t s of the region are normal i n c h a r a c t e r , (Memoir 55, page 201) i t i s probable t h a t , i f a f a u l t e x i s t s there i t s d i p i s to the south-west thus making i t normal i n c h a r a c t e r . However, presuming a southwest d i p f o r the contact i t i s p o s s i b l e that the G r a p t o l i t e beds o v e r l i e the Goodsir f o r m a t i o n without f a u l t i n g . On the other hand, the f a u l t , i f i t e x i s t s as drawn i n the above-mentioned s e c t i o n , i s a reverse f a u l t . ~ l o y - ' The Stephen-Cathedral f a u l t . This i s the l a r g e s t f a u l t w i t h a north-south trend* From Monarch i t has been t r a c e d to the south, between Mt. Stephen and Cathedral mountain, where i t d i s p l a c e s the Stephen-Dennis f a u l t at Odoray Pass; and to the north, across the east side of Mt. F i e l d . I t has a measured displacement of 3000 f e e t , downthrow to the west and a low d i p of 15 - 23 to the south-west. At Oddray pass t h i s f a u l t d i s p l a c e s the Stephen-Dennis f a u l t one-half m i l e . This l a r g e displacement i s due to the low d i p of the Stephen-Cathedral f a u l t . This shows that t h i s north-south f a u l t i n g i s younger than the northwest f a u l t -ing « : Whether the Stephen-Cathedral f a u l t continues south-ward of i t s i n t e r s e c t i o n w i t h the Stephen-Dennis f a u l t i s not known. I f there i s such a c o n t i n u a t i o n i t i s obscured i n the sheared C h a n c e l l o r f o r m a t i o n . Another f a u l t w i t h north-south trend crosses Lake McArthur and i n t e r s e c t s the Stephen-Dennis f a u l t . I t s c o n t i n u -a t i o n south cannot be t r a c e d i n t o the shear zone. As t h i s f a u l t has a n e a r l y v e r t i c a l d ip i t s displacement of the Stephen-Dennis f a u l t i s not apparent. To the n o r t h i t probably j o i n s w ith the Stephen-Cathedral f a u l t as A l l a n mentions i t c u t t i n g 1 A l l a n , J.A. G.S.C. Mem.53» p.20J. the north side of Mt. Odoray but has no t shown i t on h i s map. Age of f a u l t i n g . Some of the f a u l t i n g took place before the p e r i o d o f i n t r u s i o n , but the p r i n c i p a l f a u l t s were formed a f t e r the -108-shearing. As the f a u l t s are a l l normal they are s a i d to represent the r e c o i l a f t e r a p e r i o d of compression,, For reasons s t a t e d above the north-south f a u l t s are younger than the ones having northeast-southwest trends. F i s s u r e s . Important from an economic point of view, since they c o n t a i n pockets of l e a d , z i n c , copper and s i l v e r ores, the f i s s u r e s of the a r e a , although having no general t r e n d to them are probably formed by the same f o r c e s which produced f a u l t i n g Summary of c r u s t a l movements i n F i e l d Map Area. ( l ) North-south open f o l i : s formed by s l i g h t compression - the r e s u l t of i n i t i a l east-west s t r e s s e s . (_) Northwest-southeast mountain-building f o l d s - the r e s u l t of northeast southwest compress-ive s t r e s s e s . - i n C e n t r a l B e l t - open f o l d i n g - i n Western B e l t - close f o l d i n g and over-t u r n i n g to the southwest. (3) I n t r u s i o n of Ice R i v e r igneous complex - l a c c o l i t h i c - f u r t h e r up-arching of beds. (4) Shearing of the s o f t e r rocks notably the C h a n c e l l o r fo r m a t i o n - l a t e r than or towards close of i n t r u s i o n . (5) F a u l t i n g - maybe a r e c o i l a f t e r p e r i o d of compression, maybe formed by the compressive f o r c e s .. -109"" • • ' (a) northwest-southeast f a u l t s p a r a l l e l i n g major f o l d s and a x i s of the Rockies. (b) l a t e r north-south f a u l t s . (c) f i s s u r e s probably produced by same f o r c e s . S t r u c t u r e i n the B e a v e r f o o t - B r i s c o Ranges. The f o l d s i n t h i s area are dominantly, although not e n t i r e l y , i s o c l i n a l . Some idea of the s t r u c t u r e of these 1 mountains i s g i v e n i n Shepard's map and s e c t i o n s reproduced 1 Shepard, F.P.~ Jour, of Geol. , Vol.54, 192b, pp7b"23-64lT on P l a t e X V I I I , page 110, and F i g . 9* page 110. In many se c t i o n s exposed along the t r i b u t a r y v a l l e y s the d i p of the . formations v a r i e s but a few degrees from v e r t i c a l , except where cut by f a u l t s . S e c t i o n s show the r a p i d changes i n s t r u c t u r e along the s t r i k e . the deformation being g r e a t e s t i n the most n o r t h e r l y and s o u t h e r l y s e c t i o n s . There i s o f t e n a sharp l a t e r a l displacement of the axes of the f o l d s and a l -though the f o l d s on the east s i d e plunge p e r s i s t e n t l y n o r t h -ward there i s not the p r o g r e s s i v e change i n the age of the formation t h a t one would exnect. To account f o r these f a c t s 2 Shepard has mapped eight transverse f a u l t s i n a distance of 2 idem., p.b"JJ". " ' " ~~ 20 m i l e s . The abrupt n o r t h e r l y and s o u t h e r l y terminations of the i n t r a - v a l l e y r i d g e s such as Steamboat and J u b i l e e moun-t a i n s a l s o suggest transverse f a u l t i n g . Evidence of the Transverse F a u l t i n g . (a) Abrupt changes i n s e c t i o n . The accompanying map shows the r a p i d change i n the FIG. 3.—Geological map of the area Devonian )|j Silurian (Brisco) Ejft Ordovician, Richmond (Beaverfoot) • m ' Ordovician (Wonah quartzite and Glenogle shale) •** Lower Ordovician and uppermost Cambrian (Goodsir formation) W Upper Cambrian (Ottertail limestone) IWII Pre-Cambrian jitiating between the Richmond Beaverfoot and the Silurian seotions due to l a t e r a l displacement of the axes of f o l d i n g , (b) The i n t r a - v a l l e y r i d g e s . Shepard found a d i s t i n c t transverse f a u l t at the nor-thern end of Steamboat mountain. "Both tran s v e r s e and l o n g i -t u d i n a l f a u l t s bound other r i d g e s of the v a l l e y group" -suggesting that they are f a u l t block mountains. F i g . 9« ~ S e c t i o n s i n the B e a v e r f o o t - B r i s c o Range. ( a f t e r Shepard.) S i l u r i a n Richmond Wonah q u a r t z i t e Glenogle shale Goodsir (c) The n o r t h plunging f o l d s . A n o r t h e r l y p i t c h would be expected to cause the formations to i n c r e a s e i n age going south along these rangesj but no such change i s found. ?/hen Shepard t r a c e d the s t r i k e of the formations along the c r e s t of the B e a v e r f o o t - B r i s c o range he found a s e r i e s of f a u l t s c u t t i n g transverse to the a x i s o f the range. These cause the formations to be repeated and to p e r s i s t along the r i d g e i n s p i t e of the n o r t h e r l y p i t c h . The Redwall B r e c c i a . Extending along the B r i s c o and Stanford ranges f o r at l e a s t 15 m i l e s there i s a b r e c c i a t e d formation which i n places has a t h i c k n e s s of as great as 250 f e e t . I t c o n s i s t s of a mass • --111-. of limestone boulders ranging i n s i z e up to 7 f e e t i n diameter and of a wide v a r i e t y of co l o u r s - re d , brown, y e l l o w , grey, p u r p l e , b l u e . Almost every c o l o u r i s represented - sometimes seven or e i g h t c o l o u r s w i t h i n a few f e e t . These fragments have a calcareous cement w i t h the o c c a s i o n a l development of c a l c i t e c r y s t a l s . In some cases the formation c o n s i s t s mainly of v e i n m a t e r i a l . S t r a t i f i c a t i o n or banding i s rare and, i f present, i s g e n e r a l l y contorted and extends only f o r a few 1 f e e t , Walcott considers t h i s to be a f a u l t b r e c c i a . TUaTootlT S.M.cTTToTT75, Ko.TT~p.ll. ""  The most s t r i k i n g t h i n g about the b r e c c i a i s i t s 2 r e l a t i o n s h i p to the other beds. Shepard found that near 2 op. c i t . , p.637• ~~ ' ~ Radium Springs the b r e c c i a has " a l l the e x t e r n a l appearance of being a part of a continuous conformable s e r i e s of roc k s " l y i n g between the n e a r l y v e r t i c a l s t r a t a of the B r i s o o ( S i l u -r i a n ) formation on the east and the n e a r l y p a r a l l e l O t t e r t a i l (Upper Cambrian ) formation on the west. S i x thousand eight """Walcott, C P . ' o'p.cit., p*39» hundred f e e t of formations are miss i n g i n t h i s s e c t i o n and are very strong evidence f o r a f a u l t i n s p i t e of the p a r a l l e l arrangement of the d i p of the bordering s t r a t a and the w a l l s of the b r e c c i a . For 6 or 7 mil e s to the south the b r e c c i a continues w i t h the. same appearance of v e r t i c a l w a l l s and sep a r a t i n g formations of w i d e l y d i f f e r e n t age. In the Windermere map area there are se v e r a l zones o f the b r e c c i a ; i n some cases i t occurs between rocks of the same - I n -f o r m a t i o n , making the evidence of f a u l t i n g i n such places somewhat d o u b t f u l . In the S i n c l a i r s e c t i o n a second b r e c c i a occupies the same s t r a t i g r a p h i c p o s i t i o n as the f i r s t and probably r e -presents the outcrop of the o r i g i n a l b r e c c i a on the other limb of a s y n c l i n e . In the same s y n c l i n e eight miles north of S i n -c l a i r a huge mass of b r e c c i a t e d limestone 400 to 500 feet t h i c k l i e s conformably between the adjacent s t r a t a , but at the southernmost outcrop examined by Shepard the b r e c c i a cuts across the bedding planes f o r a short d i s t a n c e . P o s s i b l e o r i g i n of b r e c c i a F i g . 10. - The Redwall b r e c c i a . 1 Shepard forme r l y considered the Redwall formation to 1 Shepard, F.P. Jour, of Geol., V o l . 3 0 , 1 9 2 2 , p . 7 7 . be a S i l u r i a n t i l l i t e as he found a r e a l t i l l i t e i n d i r e c t l i n e of c o n t i n u a t i o n w i t h the b r e c c i a . Further i n v e s t i g a t i o n by him i n 192b showed that t h i s t i l l i t e o v e r l a y unconformably the rocks i n v o l v e d i n mountain b u i l a i n g and was e v i d e n t l y a t i l l i t e of q u i t e recent o r i g i n cemented by lime-bearing ground waters. The o r i g i n o f the b r e c c i a formation i s d i f f i c u l t to e x p l a i n . Where i t occurs along f a u l t s i t may be due to d i f f e r e n t i a l movements and the accompanying f r i c t i o n . However i t s t h i c k n e s s of hundreds of fee t i s incompatible w i t h t h i s i d e a . P o s s i b l y one, or s e v e r a l , of the S i l u r i a n formations are made up of b r i t t l e limestone of d i f f e r e n t c o l o u rs and that these rocks have been crushed to a b r e c c i a by the tremendous pressure a p p l i e d to the rocks between B r i s c o and Lake Winder-mere. Complete b r e c c i a t i o n on such a l a r g e s c a l e i s a very 1 rare occurrence. Quirke found a b r e c c i a s e v e r a l hundred feet 1 See STTepard, F.P". Jour, of G~o~l., V o l . j 4 , l ? - b . t h i c k i n the Pre-Cambrian of the western end of the Sudbury area that may have r e l a t i o n s s i m i l a r to that of the Redwall b r e c c i a . The w r i t e r wishes to b r i n g forward the suggestion t h a t the_ b r e c c i a i s caused by the drawing out and b r e c c i a t i o n of beds i n v o l v e d i n the i s o c l i n a l f o l d i n g (see F i g . 10). As no mention i s made of these b r i g h t l y coloured limestones e l s e -where i n the Rockies the blo c k s may have been coloured by ground waters subsequent to b r e c c i a t i o n . S t r u c t u r e of the S e l k i r k and P u r c e l l Mountains along the C. P. R. The broad open s t r u c t u r e s found to the south i n the Cranbrook and Windermere areas are a l s o c h a r a c t e r i s t i c of both 2 the S e l k i r k and P u r c e l l mountains i n the Railway B e l t . Daly 2 Daly, R.A. " G-.S.G. Mem.bcj, p .1127" has d e s c r i b e d the sediments i n t h i s area as a huge synclinoriurn 40 miles a c r o s s . Walker s t a t e s that the P u r c e l l range i s a -114-huge n o r t h - p i t c h i n g arch composed of numerous a n t i c l i n o r i a and s y n c l i n o r i a . T h i s l a s t g e n e r a l i z a t i o n agrees w i t h the e a r l i e r 1 Walker. J£F. G.S.C. 3umm.ReptT~l9'2bl, Pt.A. p.J25A. work by S c h o f i e l d i n the Cranbrook area. S e l k i r k s P u r c e l l s Rocky Mt, Trench F i g . 11 Upper P a l a e o z o i c O O r d o v i c i a n and Upper Gambrian ® Ross q u a r t z i t e Upper Cambrian ? O Cougar q u a r t z i t e lower Cambrian O The c r e s t s of the three ranges, the S e l k i r k s , Dog-toot h and P r a i r i e mountains, are formed from three s u b s i d i a r y s y n c l i n e s , w h i l e the Beaver and Quartz creek v a l l e y s occupy the corresponding a n t i c l i n e s . The f o l d s are open and the s t r u c -t u r e s r e g u l a r , and have the northwest-southeast C o r d i l l e r a n 2 t r e n d . 2 See above, Daly, p.112. F a u l t i n g i s not an important s t r u c t u r a l feature of these mountains. Minor s t r i k e f a u l t s o f small displacement occur. In the Beaver r i v e r a n t i c l i n e a normal s t r i k e - f a u l t w i t h a v e r t i c a l movement of perhaps 1000 f e e t d i s p l a c e s the Cougar q u a r t z i t e . Daly, i n h i s s e c t i o n reproduced i n F i g . 11, page 114, shows t h i s f a u l t d i p p i n g west at a high angle. At Laurie a c o n t o r t e d zone i n the l a u r i e m e t a r g i l l i t e formation i s the only other conspicuous break i n the mountains. ••• - 1 1 5 - ' Along the western boundary of the Rocky Mountain: Trench Daly placed a great normal s t r i k e f a u l t w i t h the down-throw on the northeast and having a v e r t i c a l displacement of 20,000 f e e t . Walcott has since placed the Cougar q u a r t z i t e i n the Cambrian so i t i s probable that the Upper Cambrian under-l y i n g the Trench f o l l o w the Cougar formation i n normal sedimen-t a r y sequence without f a u l t i n g of great displacement» Summary - S t r u c t u r e i n the C.P.R. S e c t i o n . The beds b o r d e r i n g the f o o t h i l l s d i p eastward to the A l b e r t a g e o s y n c l i n e . The deformation i n c r e a s e s i n i n t e n s i t y as one t r a v e l s across the Disturbed B e l t ot the F r o n t a l Escarpment. High-angled t h r u s t s d i v i d i n g f a u l t b l o c k s composed of w e s t e r l y d i p p i n g s t r a t a are c h a r a c t e r i s t i c of the F o o t h i l l s . The Rockies are d i v i d e d i n t o the eastern b e l t o f t h r u s t s , the c e n t r a l b e l t of open f o l d i n g and normal f a u l t i n g , and the western b e l t of clo s e f o l d i n g and t h r u s t s . The t h r u s t -i n g and f o l d i n g on both f l a n k s i n d i c a t e compressive s t r e s s e s a c t i n g from the a x i s of the range. There i s no evidence o f the t h r u s t s being cut by the normal f a u l t i n g , which has been supposed to be of l a t e r age; the s t r u c t u r e s , on the other hand, i n d i c a t e only one p e r i o d of f a u l t i n g . The S e l k i r k s and P u r c e l l s have a s i m i l a r open f o l d i n g i n the cent re of the ranges and a t h r u s t i n g to the east along the border of the Trench. The Rocky Mountain Trench i n t h i s area i s f l a n k e d on both sides by f o l d s overturned towards the Trench and i s under-l a i n by f o l d e d s t r a t a without any great f a u l t i n g . -116-IV. S t r u c t u r e along the main l i n e of the C.N.R. (Athabasca  r i v e r and Yellowhead P a s s ) . No complete s t r u c t u r e s e c t i o n has been made across • • • 1 • the Rockies i n t h i s l a t i t u d e . Dowling, McKay, Rutherford , ,-. 1 - 1 ' Warren and A l l a n have worked i n the f o o t h i l l s to the east. The l a s t three named have made an admirable s e c t i o n (see P l a t e XIX, page 117) from the eastern f r o n t at F o l d i n g mountain across the s t r i k e of the mountains to Pyramid mountain north 2 of Jasper. C o l l e t and P a r e j a s completed a s i m i l a r s e c t i o n along the n o r t h s i d e of the Athabasca v a l l e y . 1 A l l a n , Warren & Rutherford. T.R.S.C, 3rd s e r i e s , Vol.2b, Sect.IV, 1932, pp.225-248. 2 C o l l e t , l.W. et P a r e j a s , E. - E x t r a i t s du Compte Rendu des seances de l a Societe de Physique et d r H i s t o i r e n a t u r e l l e de Geneve, Vol.47, 1930, pp.80-82; Vol.49, 1952, pp.36-52, 60-67. These s e c t i o n s show o n l y the eastern b e l t of t h r u s t s , To the west, i n Mount Robson, the s t r a t a are g e n t l y f o l d e d suggesting the C e n t r a l B e l t of the C.P.R. and 49th p a r a l l e l s e c t i o n s . Bordering'the Trench on the west, the Bow r i v e r s e r i e s are c l o s e l y f o l d e d and s t r o n g l y sheared. This i s very 3 S c h o f i e l d , STJT T.R.S.C. , Sec.IV,"1.920 . p.bT suggestive of the Western B e l t of t h r u s t s found along the C.P.R. I f such a b e l t e x i s t s along the C.TT.R. then i t i s very much narrower than to the south. The E a s t e r n B e l t of Thrusts. The Front ranges comprise a s e r i e s of f a u l t b locks 4 made up of much the same s t r a t a of r o c k s . McKay has shown 4 McKay, R.B. ~"Y7cTlTMTM~."7 OctlfWTT^Z™Z~< -117-that deformation was most intense along the Athabasca r i v e r and becomes p r o g r e s s i v e l y l e s s to the southeast and northwest. This probably accounts f o r the numerous f a u l t s i n the accompany in g s e c t i o n s . ~ The b e l t has been subdivided on the b a s i s o f s t r u c -t u r e i n t o two d i s t i n c t areas: (1) an e a s t e r n area of f a u l t b l ocks made up of f o l d e d s t r a t a l y i n g to the east of Rocky r i v e r . (2) a western area of f a u l t b l o c k s showing but s l i g h t tend-ency to f o l d but g e n e r a l l y t i l t e d at high angles. These s t r u c t u r e s l i e to the west of Rocky r i v e r and probably extend to w i t h i n 5 m i l e s of Mount Robson. In the e a s t e r n area Roche a P e r d r i x , Roche M i e t t e and F o l d i n g mountain are examples of f o l d e d f a u l t blocks showing an a n t i -c l i n a l s t r u c t u r e . In the order named they are (a) a sharp a n t i c l i n e , (b) a f a u l t e d a n t i c l i n e of more complex s t r u c t u r e , / s 1 (3) a more ge n t l e f o l d . A l l a n s t a t e s that s t r u c t u r e s i n t h i s 1 op. c i t . , p.231» - '• '•• ' • area undergo r a p i d l a t e r a l changes. The s t r a t a i n the f a u l t blocks of the western area are t i l t e d to the west at high angles. The exception to t h i s i s the n e a r l y f l a t - l y i n g P a l i s a d e b l o c k , nearest to the g e n t l y f o l d e d s t r a t a of the C e n t r a l b e l t . S t r u c t u r e s appear to be continuous f o r Long ...distances along the s t r i k e . The_ second f a u l t b l ock or nappe, however, i s known to become an a n t i -c l i n a l f o l d i n the l e s s deformed country to the south, but on the whole, i n the western area, the type of f a u l t block shows -118-l i t t l e marked change i n s t r u c t u r e over long d i s t a n c e s , 1 C o l l e t and. P a r e j a s , i n t h e i r s e c t i o n to the north of 1 op. c i t . , Vol.49 t pp.44 -5a. Athabasca, found seven nappes or f a u l t b l ocks separated by seven clean cut t h r u s t s . These are summarized . i n the f o l l o w i n g t a b l e . F a u l t b l ock or nappe of t h r u s t s • over (1) Boule Roche and Roche a P e r d r i x Devonian Cretaceous U ) Roche Ronde Upper Cambrian lower Cretaceous (3) Greenock Devonian T r i a s s i c (4) Vine Creek Upper Devonian T r i a s s i c (5) Gargoyle lower Devonian J u r a s s i c (6) Chetamon ( P a l i s a d e ) Middle Cambrian Carboniferous Rocky Mountain Q u a r t z i t e s (7) Pyramid - Pre-Cambrian M i s s i s s i p p i a n A study of the s t r a t i g r a p h i c column w i l l show that i n every ease, competent s t r a t a have formed the o v e r l y i n g t h r u s t s u r f a c e , and a l s o , i n every case, except i n the Pyramid t h r u s t , the nappes have been t h r u s t over incompetent s t r a t a . This probably has l i t t l e s i g n i f i c a n c e as i n most cases the over-r i d i n g along the f a i r l y steep f a u l t planes has been s m a l l . -119-P a l a e o z o i c r o c k s , e s s e n t i a l l y l i mestones, are predominant throughout the area and form the back-bone of the p r i n c i p a l ranges. The more incompetent Mesozoic rocks u s u a l l y u n d e r l i e the v a l l e y f l o o r s . Pre-Cambrian beds are f a u l t e d against the P a l a e o z o i c s at the western end of the s e c t i o n and probably out-crop e x t e n s i v e l y to the west. Mesozoic rocks outcrop mostly i n the eastern part of the area, the o l d e r formations extending f u r t h e r west. The C e n t r a l B e l t of Gently Folded S t r a t a . Eo s t r u c t u r a l d e t a i l s are g i v e n f o r the ranges along the a x i s of the mountains w i t h the e x c e p t i o n of Mount Robson. The w r i t e r has placed i t under the heading " C e n t r a l B e l t " to emphasize i t s s i m i l a r i t y to the s t r u c t u r e found In a s i m i l a r p o s i t i o n i n the C.P.R. and 49th p a r a l l e l sections.' The accompanying s e c t i o n ( P l a t e XX, page 119)> a f t e r 1 ' 2 ' Walcott and modified by C o l l e t and Parejas , shows the g e n t l y T ~ W a l c o t t , C D . S.M.C. , Vol.75, ~o.£, 1928. 1 '. ~~~ ~ 2 C o l l e t & P a r e j a s , op, c i t . , V o l . 4 9 , Hote 5 , p.40,  f o l d e d s y n c l i n a l nature of the peak. The Western B e l t . l i t t l e i s known about t h i s r e g i o n except that the s t r a t a i n v o l v e d (Bow r i v e r s e r i e s ) are c l o s e l y f o l d e d and sheared. Summary. This s e c t i o n resembles that along the C.P.R. but judging from the wider b e l t of t h r u s t s to the east the com-pre s s i v e f o r c e s a c t i n g i n that d i r e c t i o n must have been -120- • g r e a t e r . I n t h i s b e l t the same type of h i g h angle t h r u s t s are c h a r a c t e r i s t i c and most of the nappes show great displacement without great o v e r r i d i n g . V. S t r u c t u r e i n the Peace R i v e r Area. The Peace R i v e r area c o n s i s t s of two land b l o c k s : the Peace R i v e r B l o c k , part of the l a n d grant to be given to the P a c i f i c Great Eastern Railway, when completed; and the Dominion Block f o r m e r l y under the Dominion Department o f l a n d s . The area i n c l u d e s the P a r s n i p r i v e r and the Peace r i v e r , from F i n d l a y Forks east to Pouce Coupe. The most recent and com-p l e t e work on the area has been done by M.Y. W i l l i a m s and 1 J..B. Bocock, f o r the P.G.3. Resources Survey. (See P l a t e XXI, 1 P.G.E. Railway lands Survey o f Resources Rept., P t . 2 , Vol.2. page 121.) The Dominion b l o c k , j u s t east of the f o o t h i l l s r e g i o n , o i s u n d e r l a i n by very g e n t l e f o l d s whose d i p s r a r e l y exceed 3 « The main s t r u c t u r e s l i e n e a r l y p a r a l l e l to the f r o n t ranges o f the Rocky mountains and decrease p r o g r e s s i v e l y i n height but increase i n amplitude w i t h d i s t a n c e from the mountains. The g e n t l e a n t i c l i n e s of the r e g i o n are favorable s t r u c t u r e s f o r o i l and more d e t a i l e d surveying may l o c a t e s u i t a b l e c l o s u r e s . Although only Cretaceous sandstones, conglomerates, shale and c o a l are the only rocks outcropping on the s u r f a c e , the area i s probably u n d e r l a i n by the p e t r o l i f e r o u s Devonian limestone. The main a n t i c l i n e s i n the r e g i o n are from west to e a s t , the Moberly lake , l y n x Greek-Table Mountain and the Hudson Hope P l a t e XXI PEACE RIVER AREA Compiled from P.G.E. Resources Survey maps. F a u l t s A n t i c l i n e s S y n c l i n e s Dunvegan Fort St.John Bul l h e a d Mt. J u r a s s i c Pine R i v e r T r i a s s i c Schooler Creek Devono-Carboniferous Cambrian? Mt.Selwyn Pre-Cambrian - M i s i n -chinka -121-a n t i c l i n e s . As mentioned above, these s t r u c t u r e s have v e r y o g e n t l e d i p s a v e r a g i n g about 3 • The F o o t h i l l s B e l t . (See F i g . 12, below.) (The most e a s t e r l y of the f o o t h i l l s s t r u c t u r e s , the Commotion Creek a n t i c l i n e . p a s s e s t h r o u g h the extreme s o u t h -west c o r n e r o f the Dominion B l o c k . ) g i g * 12. ( a f t e r P.G.E. Su r -veys.) S e c t i o n P i n e P a s s t o M o b e r l y Lake. F o r l e g e n d , see P l a t e X X I , p.121. The F o o t h i l l s i n the Peace r i v e r a r e a are much more rugged and o f h i g h e r e l e v a t i o n t h a n t h o s e to t h e s o u t h . The r e v e r s e i s t r u e i n the ease o f the main mountain r a n g e s , f o r the R o c k i e s to the s o u t h have g r e a t e r r e l i e f t h a n t h o s e i n t h i s a r e a . 1 Bocock has d i v i d e d the F o o t h i l l s i n t o t h r e e T~ op. c i t . , p.bb4. d i v i s i o n s , namely, the r o l l i n g , b r o k e n and p r e c i p i t o u s f o o t -h i l l s . I n the f i r s t two d i v i s i o n s o n l y wide and g e n t l e undu-l a t i o n s , w i t h o u t f a u l t i n g , o c c u r . The f r o n t ranges o f the f o o t h i l l s show en e c h e l o n s t r u c t u r e ( s e e P l a t e X X I ) . - 1 2 2 -The B u t l e r Ridge A n t i c l i n e . This s t r u c t u r e forms the f r o n t range of the f o o t h i l l s b e l t to the n o r t h of the Peace. The long a n t i c l i n a l r i d g e i s steep, i n comparison w i t h the g e n t l e s t r u c t u r e s to the ea s t , and, i n the Rocky mountain canyon, i s p o s s i b l y broken on i t s west s i d e . Here the c o a l measures outcrop on both sides of the a n t i c l i n e . Near the c r e s t , which i s crumpled and f a u l t e d , • •" . o maximum dips of 30 occur. Along the limbs the d i p decreases o o r a p i d l y to an average of 7 - 10 . To the southeast the B u t l e r r i d g e a n t i c l i n e g r a d u a l l y becomes f l a t t e n e d and passes i n t o a low g e n t l e f o l d at the west end of Moberly l a k e . The Commotion Creek A n t i c l i n e . The front- range of the f o o t h i l l s i n the l a t i t u d e o f Moberly lake i s formed by the Commotion Greek a n t i c l i n e ten mi l e s to the west of the l a k e . This s t r u c t u r e continues i n a southeast d i r e c t i o n , but i t a l s o subsides to a ge n t l e f o l d by the time i t crosses the Pine r i v e r at Gommotion creek. The Pine r i v e r a n t i c l i n e , 13 m i l e s west of Commotion creek, has thrown up F a l l s mountain which forms the Front range on the Pin e . The P r e c i p i t o u s F o o t h i l l s Area. The rocks of t h i s d i v i s i o n of the f o o t h i l l s along the Pine r i v e r are sharply f o l d e d and normally f a u l t e d , but there i s no o v e r t h r u s t i n g or block f a u l t i n g . Bocock s t a t e s that on the Peace heavy competent limestones c a r r y the s t r e s s e s over long d i s t a n c e s of f l a t or ge n t l e dips and l o c a l i z e d the deformation to s m a l l e r areas of steep f o l d i n g and f a u l t i n g . Steep dips and considerable throw, one of 1100 f e e t noted by Mclearn, are c h a r a c t e r i s t i c of the f a u l t s of the r e g i o n , The Rocky Mountains. In the mountains the s t r u c t u r e d i f f e r s from that of the Rockies f u r t h e r south i n that i t c o n s i s t s of a s e r i e s of sharp, broken, and i n some cases overturned f o l d s . ^ (See Fig.12) 1 idem, p.tf83. ~* -"In the centre of the range there i s considerable normal f a u l t i n g , but east of the summit the re i s l i t t l e evidence of the o v e r t h r u s t i n g and block f a u l t i n g so common i n the south. At the summit of Pine Pass a block c o n s i s t i n g of the Pine Pass formation capped w i t h Devonian limestones has been t h r u s t over the l e s s competent Mountain Greek formation which i n t u r n has been t h r u s t over the Carboniferous limestone. West of the summit the M i s i n c h i n k a s c h i s t s have been f a u l t e d and o v e r t h r u s t covering the Devonian limestones. Rocky Mountain Trench. -This great physiographic f e a t u r e here separates the Rockies from the I n t e r i o r P l a t e a u . As the rocks are so covered i n the Trench l i t t l e i dea of the u n d e r l y i n g s t r u c t u r e s can be a r r i v e d at u n t i l more d e t a i l e d work i s done. To the west of the Trench rocks of apparently the Cache Creek s e r i e s have been broken and metamorphosed by igneous i n t r u s i o n s . Here again the surface i s so h e a v i l y d r i f t covered that very l i t t l e about the s t r u c t u r e i s known. -124*-Summary. As i n the more so u t h e r l y s e c t i o n s , deformation i n the F o o t h i l l s i n c r e a s e s as the mountains are approached. The mountains however appear to have only the eas t e r n b e l t of t h r u s t s developed, i . e . they appear to be the r e s u l t of t h r u s t -in g from the: west. S e c t i o n ITT. THE NORTHERN MOUNTAINS. I n t r o d u c t i o n . 1 McConnell found t h a t the L i a r d r i v e r marked the 1 McConnell, E.G. G.S7cT~AnnTRept. Itititi-iiJ , P t . I V , p.4?d. northern l i m i t of the mighty Rocky mountains extending i n a b e l t over 50 m i l e s i n width and 1000 m i l e s i n l e n g t h from i n Montana to the Yukon. Only a s i n g l e range of the Rockies extends across the L i a r d r i v e r ; the mountain masses are o f f s e t 150 miles or more to the east and continue to the nor t h as the Mackenzie mountains and a s s o c i a t e d ranges. This dying out of the Rockies to the nor t h i s shown by the gradual decrease, towards the L i a r d , i n the e l e v a t i o n of the peaks and i n the w i d t h of the mountain b e l t . Obviously the deforming s t r e s s e s have not been so great i n the north as i n the southern Rockies. The great o v e r t h r u s t s o f the south are l a c k i n g . - 1 2 5 -1 Dowling s t a t e s that north of the 60th p a r a l l e l the T~DowIing, D.B. " T.R".~S7GT7~STcTT~r~l922, p . T T J . mountains do not l i e along the western limb of a great geosyn-c l i n e , as i n A l b e r t a , but, proceeding northward, cross i t d i a g o n a l l y from west to east and reach n e a r l y to the eastern edge, g i v i n g an en echelon arrangement to the ranges* The causes f o r t h i s sudden break i n alignment north . . 2 of the L i a r d r i v e r are given by W i l l i a m s as f o l l o w s : "The 2 WrlTI'ams,•:M..Y. BuTTTG-.S„A. , V o l . 3 5 , p*Tb3. cause of the echelon arrangement may be considered best i n the l i g h t of the r e l a t i o n s h i p s of the f r o n t s of the Rocky mountain ranges and the f l a n k i n g sediments to the ea s t . Prom L i a r d R i v e r south 2,000 f e e t or more of interbedded sandstones and shales of Mesozoic age occupy the f o o t h i l l s and a d j o i n i n g p l a i n s r e g i o n . These incompetent sediments have not t r a n s -m i t t e d mountain-building t h r u s t s to any great distance to the ea s t , but have absorbed the s t r a i n w i t h i n themselves by i n t r i c a t e f o l d i n g and f a u l t i n g i n the d i s t u r b e d b e l t , which i n c l u d e s the f o o t h i l l s . " "From L i a r d r i v e r n o r t h , the Mackenzie and F r a n k l i n mountains f r o n t f o r the most part on the same P a l e o z o i c formations that make up the mountains them-s e l v e s . " "At t h e i r n o r t h e r n end the Mackenzie mountains terminate at the p l a t e a u - l i k e area of Cretaceous sediments extending southward from the Mackenzie D e l t a . " The Mackenzie mountains are o f f s e t about 150 m i l e s to the east of the main trend of the Rocky mountains. They o ' o extend from the L i a r d r i v e r i n l a t i t u d e 60 to l a t i t u d e 66 and form the main no r t h e a s t e r n d i v i s i o n of the C o r d i l l e r a n system. The F r a n k l i n mountains l i e east of Mackenzie r i v e r and extend from 62° 45 f n o r t h , northward to an unknown distance beyond Great Bear r i v e r , probably to l a t i t u d e t>5° 30' n o r t h . Ranges East of the Mackenzie. The F r a n k l i n Mountains. The Mackenzie mountains form the main no r t h e a s t e r n d i v i s i o n of the Rocky mountains. The F r a n k l i n s , 20 to 50 m i l e s to the e a s t , form a s u b s i d i a r y and extreme n o r t h e a s t e r n con-t i n u a t i o n of the system. "The general f e a t u r e s suggest that the range i s i n the main a t i l t e d f a u l t b l ock w i t h a s e r i e s o f f a u l t scarps • • . 1 c o n t r o l l i n g i t s eastern f a c e . " 1 W i l l i a m s , MT~~ Bui 1. Ge olYSo c. Am. , Vol.3 5 , 1?24 >~P"*44"9 T4l)T7 Gap mountain i s a w e s t e r l y d i p p i n g f a u l t b l ock bounded on the east and northeast by a c u r v i n g f a u l t scarp. The beds on the western f l a n k dip g e n t l y towards the Mackenzie while the s t r u c t u r e s e c t i o n (see F i g . 15, page 127) shows those 2 to the east of the f a u l t d i p p i n g s t e e p l y to the east. I n 2 Map 2022, GTS.C. Summ.Rept. 1923, Pt.B, p.4(b")7"" ' general the s t r u c t u r e appears to be that of an asymmetrical a n t i c l i n e w i t h gentle western and steep e a s t e r n slopes, the r e s u l t of a t h r u s t from the west. This a n t i c l i n e has been normally f a u l t e d along i t s c r e s t w i t h the downthrow side to the e a s t . . . . . . - 1 2 7 -In Mount C l a r k the closed a n t i c l i n e which forms the n o r t h e r n peak changes to the southeast i n t o a reverse f a u l t w i t h an upthrow of 2000 f e e t from the east. W i l l i a m s 1 found 1 op» c i t . , p.453« "~~ " "* " p the f a u l t plane to s t r i k e 42 south of east and d i p northeast o at 30 . On the eastern s i d e of Mount Clark another f a u l t , p a r a l l e l i n g the c r e s t of the a n t i c l i n e , has a downthrow to the east of at l e a s t 1500 f e e t . The eastern face of Mount Charles a l s o suggests a f a u l t scarp. I t has a gentle dip t o the west and a p r e c i p i t o u s scarp to the east w i t h a probable downthrow to the east o f at l e a s t 1500 f e e t . F i g . 13 ( a f t e r W i l l i a m s . ) Devonian - blue S i l u r i a n - y e l l o w Cambrian & B e l t i a n - red From the above evidence W i l l i a m s has concluded that the F r a n k l i n range shows t y p i c a l Rocky mountain orogeny and that t h i s i s e x e m p l i f i e d by the b l o c k - f a u l t e d s t r u c t u r e . The Norman Mountains. "The mountains Of the Norman o i l area a r e , f o r the most p a r t , g i g a n t i c f o l d s some of which are very sharp but have - 1 2 8 - : very l i t t l e f a u l t i n g . " 1 East of the o i l w e l l s the range i s the T~Hume ," G. S. ""Summ.Rept. , 1922, Pt.B, p.59. ~~ west h a l f of a huge a n t i c l i n e , the eastern h a l f of which has been eroded away producing steep eastward-facing escarpments. No f a u l t i n g occurs near t h i s escarpment. The Wolverine a n t i c l i n e to the n o r t h has been des c r i b e d by K i n d l e and Bosworth. Devonian limestones outcrop 2 G.S."G7~~Summ.Rept. 1920 9 Pt.B, "p7Jl~ ~~~~ on the c r e s t of the a n t i c l i n e and are f l a n k e d by Cretaceous rocks. These Gretaceous rocks have been i n v o l v e d i n the mountain-building w h i l e the Eocene beds i n the v i c i n i t y of Fort Norman are comparatively undisturbed and f l a t - l y i n g and are c l e a r l y l a t e r than the mountain-building. This g i v e s to the Norman mountains a iaramide a g e , s i m i l a r to that of the southern Rookies, the L i a r d and Mackenzie mountains. Mountains West of the Mackenzie. L i a r d Mountains. These mountains occur en echelon along the L i a r d r i v e r as shown on McConnell 1s map. S t r a t a of Cretaceous age " " l i c C o l m e l l , R. G. G.STcTTnn.R^^ are i n v o l v e d i n the mountain-building, thus g i v i n g a Iaramide age to the mountains. At Fort L i a r d hard Devonian and Carbon-i f e r o u s limestones form a mountain range which continues w i t h only a few minor breaks to Lone mountain at North Nahanni j u n c t i o n . Mackenzie Mountains. 1 The Mackenzie mountains have been s t u d i e d by Keele 2 '. and Hume . The former descended the Gravel r i v e r , the l a t t e r 1 K e e l e , J . G.S.C. 1910. "A G e o l o g i c a l Reconnaissance ~ across the Mackenzie Mountains." 2 Hume, G.S. G.S.C Summ.Rept., 19 - 1 , Pt.B, pp.67-68.  ascended the North Nahanni and Root r i v e r s . I n the n o r t h e r n s e c t i o n along the Gravel r i v e r , Keele s t a t e s , "the s t r u c t u r e i s c h a r a c t e r i z e d by f o l d i n g , g e n e r a l l y on a broad s c a l e , which has thrown the s t r a t a i n t o a s e r i e s of a n t i c l i n e s and s y n c l i n e s ; but the f o l d i n g i s some-times c l o s e , and i n c e r t a i n eases the f o l d s appear to be overturned and o v e r t h r u s t . North to 65° N. these mountains s t r i k e s l i g h t l y west of n o r t h , but at that l a t i t u d e they swing i n a wide c i r c l e to the westward to cross the upper branches of the Peel r i v e r . " Keele s t a t e s that on the Wind r i v e r the mountain-building f o r c e s have been l e s s intense and that the s t r u c t u r e i s c h a r a c t e r i z e d by open f o l d s w i t h comparatively low dips to the beds,and that the ranges here s t r i k e east and west. Nahanni R i v e r s e c t i o n . Along the North Nahanni r i v e r the hard r e s i s t a n t middle Devonian rocks form the two easternmost ranges of the Mackenzie mountains, 3 and 15 m i l e s , r e s p e c t i v e -l y , west of the j u n c t i o n of the North Nahanni. These trend s l i g h t l y west of n o r t h . Both ranges are f l a n k e d by long gentle slopes and dips to the west and steep escarpments and dips to the e a s t , as shown i n F i g . 14, page 130. That i s , they are asymmetrical a n t i c l i n e s with the a x i a l plane dippi n g to - 1 3 0 -the west. The steep e a s t e r n f a c e s , towards the Mackenzie, are f a u l t l i n e scarps. The eroded f a u l t plane dips eastward p a r a l l e l i n g the steep d i p of the s t r a t a on the eastern limb, and b r i n g s the Middle Devonian limestone i n t o c o n t i g u i t y w i t h the Upper Devonian Simpson s h a l e s , r e s u l t i n g i n a downthrow to the east of approximately 3 0 0 0 f e e t . The limestone escarpments stand 2 0 0 0 - 3 0 0 0 f e e t above the Mackenzie, Between them i s a wide s y n c l i n e u n d e r l a i n by the l e s s r e s i s t a n t Upper Devonian s t r a t a , i n c l u d i n g the Simpson s h a l e s . F i g . 14. ( a f t e r Hume.) Upper Devonian limestone o Simpson shales O Mid - Devonian limestone O To the west of these ranges Hume found a broad pla t e a u of Upper Devonian rocks t e r m i n a t i n g against high c l i f f s 2 0 - 3 0 miles d i s t a n t . This t h i r d escarpment was not composed of Upper Devonian rocks. Root R i v e r s e c t i o n . The eastern range of the Mackenzie mountains i s , i n t h i s area, about 2 0 miles west of the Macken-z i e . The same eastward-facing f a u l t l i n e scarp w i t h s y n c l i n a l s t r u c t u r e to the west, shown i n F i g . 14, p e r s i s t s from the -131-North Nahanni to beyond Root r i v e r . The downthrow to the east of the escarpment i s of the order of 5000 or 6000 f e e t . The f l a t p l a i n between the Mackenzie r i v e r and the Camsell mountain range widens from l e s s than 2 miles i n the v i c i n i t y of Camsell mountain to over 20 miles along the Root r i v e r . As t h i s p l a i n i s covered by muskeg and l a k e s , l i t t l e i s seen of the u n d e r l y i n g rocks except along the r i v e r banks. These exposures are a l l of Upper Devonian s t r a t a . Along the Root r i v e r t h i s p l a i n i s u n d e r l a i n by a g e n t l e a n t i c l i n e , the western limb of which b u t t s against the eastern escarpment o f the Mount Camsell range. Dahadinni-Redstone area. The f r o n t range of the Mackenzie mountains, 25 m i l e s west of the Mackenzie r i v e r , i s again a sharp asymmetrical f o l d with the a x i a l plane- dipp i n g to the west. However no f a u l t i n g i s known along i t s eastern limb. The Mid-Devonian limestone,out cropping on the c r e s t of the a n t i c l i n e , i s o v e r l a i n by Upper Devonian and Cretaceous rocks. The s t r u c t u r e of the Cretaceous rocks u n d e r l y i n g the p l a i n , between the mountains and the Mackenzie, i s not known, but there i s undoubtedly minor undulations i n the s t r a t a . l i t t l e Bear R i v e r and Carcajou R i v e r areas. The Mackenzie p l a i n s t r e t c h e s to the high mountains 35 miles west of Norman and i s u n d e r l a i n by Cretaceous rocks . These mountains, through which the Carcajou r i v e r c u t s , are an a n t i c l i n e exposing S i l u r i a n and Devonian s t r a t a . Although the rocks on the east side of these mountains d i p s t e e p l y to the e a s t , no f a u l t i n g was seen. To the west the f o l d i n g i s more complicated and the topography more rugged. F i f t e e n miles southwest of Norman s i m i l a r s t r a t a are exposed i n a small a n t i c l i n e which d i e s out to the south of the L i t t l e Bear r i v e r . Richardson Mountains. This range which separates P e e l r i v e r from the Por-cupine has a north-south t r e n d . " I t has a general a n t i c l i n a l s t r u c t u r e , and i s broken by l o n g i t u d i n a l f a u l t s . On the ea s t -ern s ide the mountains present a steep f a u l t face to the d e l t a of the Mackenzie and the beds undulate g e n t l y . I n the middle o of the range the dips increase to 70 but maintain an e a s t e r l y d i r e c t i o n , but on the western side the beds g r a d u a l l y f l a t t e n and f i n a l l y d i p westward. As the range approaches the sea-1 coast the s t r i k e of the beds assumes a more w e s t e r l y t r e n d . a  T Camsell, 0. & Malcolm,""1//. G.S.C Mem. 10b , "p.87. "~ ' Summary - The Northern Mountains. The ranges trend p a r a l l e l to the a x i s of the Rocky mountains and the Continent, but d i f f e r from the Rockies i n that they l i e " e n echelon over a.wide shallow geosyncline — extending almost to i t s eastern edge. Almost without exception each range c o n s i s t s of an asymmetrical a n t i c l i n e w i t h gent lo-west ern and steep eastern s l o p e s . Normal f a u l t i n g may, or may not, have taken place along planes p a r a l l e l i n g the steep east-ern s l o p es. The f o l d i n g i s the r e s u l t of a t h r u s t from the west • I f the ranges be regarded as f a u l t blocks the long westward d i p i s s i m i l a r to the t i l t e d f a u l t blocks of the - 1 3 3 -F o o t h i l l s "but t h r u s t i n g appears to be e n t i r e l y absent. I t i s apparent that the s t r u c t u r e s are d i f f e r e n t to those i n the Rockies to the south though these mountains probably r e s u l t from the same, though l e s s i n t e n s e , orogenic movements a c t i n g on a shallower g e o s y n c l i n e . S e c t i o n V. THE ALBERTA SYNGLIITE. STRUCTURE. To the east of the d i s t u r b e d f o o t h i l l s b e l t l i e s the A l b e r t a g e o s y n c l i n e , the d i r e c t descendant of the great C o r d i l l e r a n geosyncline from which the Rocky mountains and the F o o t h i l l s arose. Although t h i s s t r u c t u r a l f e a t u r e i s to the east of the area considered i n t h i s t h e s i s , a short o u t l i n e of i t s s t r u c t u r e w i l l be g i v e n as i t i s the most recent evidence o f the eastward m i g r a t i o n of the C o r d i l l e r a n geosyncline d i s c u s s e d on page _9» E r o s i o n , contemporaneous w i t h , and subsequent to the b u i l d i n g of the Rocky Mountains and F o o t h i l l s has r e s u l t e d i n T e r t i a r y c o n t i n e n t a l sedimentation i n the shallow geosyncline to the east. F o l l o w i n g t h i s , the general u p l i f t of the l a n d , w i t h a d d i t i o n a l f o l d i n g and f a u l t i n g has r a i s e d p r a c t i c a l l y a l l the T e r t i a r y beds above the present s e a - l e v e l . Dowling 1 has o u t l i n e d the p o s i t i o n and area of t h i s T.Dowling, D.B. "G.S.C. Mem.lib. ' " P l a t e XXII. The A l b e r t a Geosyncline. s y n c l i n e , see P l a t e X X I I , page 134. The overthrust block under l y i n g Turner V a l l e y i s the most e a s t e r l y known deformation r e s u l t i n g from the Laramide R e v o l u t i o n and marks the western boundary of the s y n c l i n e . 1 From w e l l - d r i l l i n g s i n t h i s r e g i o n L i n k has shown 1 L i n k , T.A. A l b e r t a S y n c l i n e . Bull.Am.Assoc.PetiGeol., " V o l . 1 5 . May 1931, pp.491 -506. that the r e l a t i v e l y shallow A l b e r t a geosyncline i s , l i k e i t s predecessors, d e c i d e d l y asymmetrical. On the west,bordering Turner V a l l e y , a narrow zone o f . s t r a t a dips s t e e p l y to the deepest part of the s y n c l i n e . Sanderson, i n d e t a i l e d work i n the Porcupine H i l l s area, has shown that t h i s deepest part l i e s l e s s than 2-g- miles to the west of the outer overturned F o o t h i l l s f o l d . From there the s y n c l i n e shallows very gradu-a l l y , as shown on P l a t e I I I , page 30. The g e n t l e d e p o s i t i o n a l d i p of the sediments away from the o l d land mass i s g r e a t l y accentuated as the greatest downwarping due to l o a d i n g would occur d i r e c t l y beneath the locus of g r e a t e s t accumulation. The deepest part of the syn-c l i n e i s , then, close to the o l d land mass, that i s , close to the outer F o o t h i l l s f o l d . On the eastern limb the sediments die g e n t l y away towards the more d i s t a n t and l e s s e l e v a t e d e a s t e r n land mass, the Canadian S h i e l d . -136-Chapter IY. THEORIES OF ORIGIN AND DEVELOPMEUT OF FOLD MOUNTAINS SYSTEMS AND THEIR APPLICATION TO THE ROCKY MOUNTAINS Theories of Mountain-Building* The great mountain systems of the earth are composed of complexly f o l d e d and f a u l t e d sedimentary formations that have been i n t r u d e d by igneous rock. T h e i r complexity v a r i e s from the symmetrical f o l d s of the J u r a mountains to the 1 i n t r i c a t e l y c o n t o r t e d s t r a t a of the nieghbouring A l p s . Nevin 1 Nevin, CM. "The P r i n c i p l e s of S t r u c t u r a l Geology", 1931, pp.272-295* s t a t e s t h a t these mountain ranges a l l have a s i m i l a r h i s t o r y and the g e o l o g i c a l events occur i n the f o l l o w i n g order: (1) Accumulation of great t h i c k n e s s e s of sediments i n the geo s y n c l i n e . (2) Development of deformational s t r e s s e s w i t h r e l a t i v e suddenness. Smashing and squeezing of the sediments. Igneous m a t e r i a l i n t r u d e d along a x i s of the deformed zone. (3) P e r i o d of e r o s i o n during which the mountains, which had only a moderate e l e v a t i o n , were reduced to a peneplain. (4) S e r i e s of v e r t i c a l u p l i f t s and a s s o c i a t e d igneous e x t r u s i ons. (5) E r o s i o n i n time may reduce the mountains to quiescent stumps. The g e o l o g i c a l h i s t o r y of the P u r c e l l and S e l k i r k mountains f o l l o w s t h i s o u t l i n e very c l o s e l y . In the Rockies - 1 3 7 -v e r t i c a l u p l i f t appears to have f o l l o w e d c l o s e l y , or to have been synchronous w i t h the f o l d i n g and f a u l t i n g of the s e d i -ments. W i l l i s 1 b e l i e v e d the re was a p e r i o d of e r o s i o n and peneplanation coming between two periods of compression but Mackenzie found no evidence of t h i s peneplanation. 1 W i l l i s , B. Bull.Geol.Soc.Am., 13, 1902, p.339. ~" 2 Mackenzie, J.D. T.R.S.C., V o l . l 6 , 1922, pp .119-123.  Before attempting an e x p l a n a t i o n of the above pheno-mena , there f o l l o w s a short d i s c u s s i o n of the f a c t o r s i n v o l v e d ( l ) l a t e r a l compression; (2) V e r t i c a l s t r e s s e s ; (3) C o n d i t i o n of the sub-stratum. l a t e r a l compression. As has been po i n t e d out the s t r u c t u r e of the great mountain ranges of the world r e s u l t from deformation under t a n g e n t i a l s t r e s s . Compressive s t r e s s e s are c o n t i n u a l l y a c t i n g on the earth*s c r u s t and i t i s i n the mountain areas t h a t the c h a r a c t e r i s t i c phenomena r e s u l t i n g from l a t e r a l com-p r e s s i o n are best developed. Both h o r i z o n t a l and v e r t i c a l s t r e s s e s have acted on most mountain ranges. One i s not a component of the other as i t i s impossible to e x p l a i n a c r u s t a l shortening such as i s found i n the Himalayas, A l p s or Rockies as the h o r i z o n t a l component of a v e r t i c a l s t r e s s . In the Alps,Heim f i n d s that a 4:1 to 8:1 r a t i o i s necessary to e x p l a i n the shortening i n the A l p s . As t h e i r present breadth i s over 90 miles t h i s means that the s t r a t a i n v o l v e d were deposited over a zone of 300 to perhaps 700 m i l e s i n width. I t i s e q u a l l y impossible to • • • . -138-e x p l a i n the v e r t i c a l u p l i f t of mountain ranges and plateaus as a component of the t a n g e n t i a l s t r e s s e s . Theories of o r i g i n of L a t e r a l Compression. Modern t h e o r i e s of mountain-building d i f f e r i n t h e i r e x p l a n a t i o n of the o r i g i n of the t a n g e n t i a l s t r e s s e s . The f o l l o w i n g are the most important: (a) For lon g i t was b e l i e v e d that the earth was a c o o l i n g body and that mountain ranges were the r e s u l t of com-pr e s s i v e s t r e s s e s a r i s i n g when the outer crust sought to adjust i t s e l f to the s h r i n k i n g core. But the earth shows no s i g n of l o s s of heat and the mountain systems of recent g e o l o g i c a l time are as great as any of which we have knowledge. This shows that there has been no l e s s e n i n g of the f o r c e , such as would be expected i f the s t r e s s e s r e s u l t e d from the l o s s of the earth's heat. (b) J o l y 1 has brought forward the theory that there l:"_Joiy, J . "The S u r f a c e - H i s t o r y ~ o f the E a r t h " , "789-127* i s a p e r i o d i c i t y to mountain-building. He has shown that the heat gene r a t e d by radium emanations i n the e a r t h cannot escape because of the very low c o n d u c t i v i t y of the outer crust of the ea r t h but accumulates over a p e r i o d of the order of 100,000 ,000 years u n t i l i t has l i q u i f i e d the sub-stratum below a depth of 70 m i l e s . This heating causes t e n s i o n i n the outer c r u s t and escape of heat i n t o the oceans. F o l l o w i n g t h i s l o s s of heat the earth's crust i s too la r g e f o r the substratum. This r e s u l t s i n compressive s t r e s s e s wMich f o l d and f a u l t the crust along zones of weakness, i . e . i n the geos y n c l i n e s . These com-pr e s s i v e f o r c e s have f o r c e d the sediments of the geosyncline below t h e i r l e v e l of i s o s t a t i e e q u i l i b r i u m . When the com-pr e s s i v e f o r c e s are r e l i e v e d v e r t i c a l adjustments take p l a c e . (c) Lawson and others b e l i e v e that the compressive f o r c e s o r i g i n a t e i n the geosyncline due to expansion of the sediments as they are fo r c e d down to zones of higher tempera-t u r e . To the w r i t e r t h i s expansion seems inadequate. The deep part of the g e o s y n c l i n a l trough i s a r e l a t i v e l y narrow b e l t , and would have to undergo e x t r a o r d i n a r y expansion;-;:to cause c r u s t a l shortenings o f the magnitude of those found i n such ranges as the Alps and the Rockies. • • • 1 (d) Chamberlin b e l i e v e d that the e a r t h was conden-1 Chamberlin. R.T. Jour, of Geol.. vol.33, 1925, PP.755-792T" s i n g towards the centre but that there was greater r e l a t i v e condensation i n the oceanic than i n the c o n t i n e n t a l segments. Thi3 would produce compressive s t r e s s e s i n the c o n t i n e n t a l segment. These s t r e s s e s would be l o c a l i z e d along the borders of the co n t i n e n t s r e s u l t i n g i n the formation of mountain ranges. Chamberlin a p p l i ed the same p r i n c i p l e , on a sma l l e r s c a l e , to two-sided orogeny o f a s i n g l e system (see d i s c u s s i o n below) «•:•..:• So f a r no theory o f the o r i g i n of l a t e r a l com-p r e s s i o n i s accept a b l e . The r e s u l t s of the f o r c e s we can see, but of t h e i r o r i g i n we know l i t t l e . Manner of a c t i o n of L a t e r a l Compression. That compressive s t r e s s e s must have acted at a r i g h t angle to the trend of the geosyncline of d e p o s i t i o n i s a t t e s t e d by the a t t i t u d e of the deformed s t r a t a of a l l great mountain systems. This -140 T g e n e r a l i z a t i o n i s a c l e a r - o u t orogenic law. As has "been noted a geosyncline i s an unstable part of the c r u s t f i l l e d w i t h r e l a t i v e l y weak sediments. I f compressive s t r e s s e s were operative i n the r e g i o n occupied by a g e o s y n c l i n a l -g e a n t i c l i n a l couple the r e s u l t a n t deformation would n a t u r a l l y appear as a crumpling at r i g h t angles to the trend o f the trough, i . e . the s t r e s s e s would be res o l v e d i n t o components normal to the l i n e of weakness. Nevertheless the o r i g i n a l s t r e s s e s must be n e a r l y normal to the trough because, i f they were not, the component p a r a l l e l to the a x i s of the trough would develop l o n g i t u d i n a l t e a r f a u l t s w i t h l a t e r a l d i s p l a c e -ment, p a r a l l e l to the trend of the mountains. F o l d i n g and f a u l t i n g thus represent a simple squeezing of a weak trough between r e s i s t a n t areas. The d i r e c t i o n of the s t r e s s e s . G e o l o g i c a l o p i n i o n d i f f e r s i n whether the t a n g e n t a l t h r u s t s came from one or both s i d e s of the g e o s y n c l i n e . Those f a v o u r i n g a one-sided orogeny b e l i e v e that the sediments were crumpled and t h r u s t by a s t r e s s a c t i n g g e n e r a l l y from the d i r e c t i o n of the o l d land s u r f a c e ( g e a n t i -cline), and, that any f o l d i n g and f a u l t i n g i n the opposite d i r e c t i o n are assumed i n a l a t e stage of orogeny when the i n e r t i a of the over t h r u s t mass causes s l i g h t f o l d i n g and f a u l t i n g i n a d i r e c t i o n opposite to the movement. Others f i n d evidence i n most of the great mountain systems of a two-sided orogeny where the geosyncline area has been squeezed as a wedge between two r e s i s t a n t areas. The asymmetry o f the systems i s due to the d i f f e r e n c e s i n character P l a t e .XXIII. THE WEDGE THEORY OF 1)1 ASTKOl'II l.Sil 7<>7 T IG 7 - M a p of a portion of the Caledonian orogenic wedge. In Scandinavia, where the compressed belt bends forward to the east, the ovcrthrusling toward the east I the eastern flank has been particularly pronounced. In the BnUsh Isles, where the d d t e d belt makes a salient to the west, the ^ ^ ^ ^ M ^ strongly dominant. Some pivot action, with the neutral point under the North Sea between the Shetland Islands and Norway, is suggested. The amount of oyerthrust-ing is represented by the relative lengths of the arrows. The Caledonian Wedge. ( a f t e r Chamberlin.) . .--141- • • o f the bo r d e r i n g areas,not to a s t r e s s a c t i n g i n only one 1 • d i r e c t i o n . Chamberlin has found good evidence of two-sided I Chamberlin.R.T. JourT of Geol.. v o l . 5 3 , 1925, PP «755-795* orogeny In the f o l l o w i n g mountain systems: Appalachians Pyrenees Mountains Hocky Mountains Caucasus Mountains Caledonian Mountains Jurasside Mountains of the Cor-d i l l e r a Alps Mountains The accompanying P l a t e X X I I I , page 141, i l l u s t r a t e s the two-sided nature of the s t r u c t u r e i n the Caledonian wedge. F i g . 15* Diagrams i l l u s t r a t i n g two-sided. orogeny. Showing d i f f e r e n t types of f a i l u r e . ( a f t e r Chamberlin.) U n t i l more i s known about the a b i l i t y of rocks to transmit s t r e s s e s over great d i s t a n c e s , when f l a t - l y i n g and when f o l d e d , no d e f i n i t e d e c i s i o n can be made as to whether the s t r e s s e s acted i n a s i n g l e or i n opposing d i r e c t i o n s . The surface f e a t u r e s of many mountain ranges could have o r i g i n a t e d i n e i t h e r way. The w r i t e r has attempted to i l l u s t r a t e t h i s idea i n F i g . 15, ab'OT©. The d i f f e r e n c e i s that i n s i n g l e - s i d e d orogeny the side opposite to the t h r u s t i s considered as a b u t t r e s s ; i n two sided orogeny i t i s considered as a c t i n g as a s t r e s s . The r e s u l t a n t s t r u c t u r e s may "be n e a r l y i d e n t i c a l . V e r t i c a l s t r e s s e s . I s o s t a s y and i t s r e l a t i o n to mountain-building and geosyn-• dines. ' • The s t r e n g t h of the earth's c r u s t . G e o l o g i c a l evidence has shown that there i s a considerable amount of st r e n g t h i n the earth's crust and that the near-surface rocks have the a b i l i t y to m a i n t a i n some degree of e q u i l i b r i u m even i f subjected to long time s t r e s s e s . Geodysists, from t h e i r c a l c u l a t i o n s of g r a v i t y anomalies, c l a i m p e r f e c t compensation f o r areas 30 miles i n diameter and n e a r l y complete compensation f o r areas as low as 17 m i l e s i n diameter. G e o l o g i s t s on the other hand f i n d no evidence of compensation i n areas up to 50 miles and only 1 s l i g h t adjustment i n areas of as great as 200 miles a c r o s s . 1 Coleman, A.P. Geol.Soc.Am., Vol.31, pp.32b^2T7 T ? 2~0^  Swanson, CO. Jour.Geol.. V o l . 3 6 , pp.411-433, 1928. Peneplanation of mountain ranges. Assuming a 107. d i f f e r e n c e i n s p e c i f i c g r a v i t y between the sediments to be eroded from the mountain mass and the denser m a t e r i a l r e p l a c i n g i t at the depth of compensation (60 m i l e s ) , then by i s o s t a t i c adjustment every 1000 f e e t of eroded m a t e r i a l w i l l be balanced by 900 f e e t of the sub-crust which enters,and the surface w i l l be lowered 100 f e e t . In t h i s way an e l e v a t i o n of 3000 f e e t could be reduced to sea l e v e l only by the ero s i on and t r a n s p o r t a t i o n of some 30,000 f e e t of m a t e r i a l . I s o s t a s y and ge0synclines. The f r e s h l y deposited sediments -143- . must be considered as a load which upsets the i s o s t a t i c balance and d i s p l a c e s an equal mass of s u b - c r u s t a l m a t e r i a l * However t h i s s u b - c r u s t a l m a t e r i a l i s r e l a t i v e l y dense and t h e r e f o r e l e s s volume i s d i s p l a c e d than i s added by the s e d i -ments. Again, assuming a d i f f e r e n c e i n s p e c i f i c g r a v i t y of 10%, f o r every 1000 f e e t of sediments ( a f t e r compaction) deposited i n the geosyncline t h e r e . w i l l only be 900 f e e t r e -moved at the depth of compensation. This would cause a r a p i d f i l l i n g up of the g e o s y n c l i n a l trough.for, i f the geosyncline had an o r i g i n a l depth of as great as 600 f e e t i t would be f i l l e d up, a c c o r d i n g to i s o s t a s y , when 6000 f e e t of sediments had been dep o s i t e d . Yet the g e o l o g i c a l record shows that i n the Rocky mountains over 50,000 f e e t of shallow water sediments have been d e p o s i t e d , which proves that s i n k i n g went on f o r a l o n g period of time and that the bottom of the trough was adjusted about as f a s t as the sediments were added. Therefore, room f o r the l a r g e bulk of r e l a t i v e l y l i g h t sediments must be made by some cause e n t i r e l y removed from i s o s t a s y , or i s o s t a s y aided by some other f o r c e . The Substratum. To account f o r the workings of i s o s t a s y , the a c t i o n of s e i s m i c waves and other earth phenomena, g e o l o g i s t s and geo-d y s i s t s are i n agreement that the substratum of b a s a l t i s i n a l i q u i - v i t r e o u s s t a t e , i . e . i t has no r i g i d i t y . The change from the s o l i d rocks of the c r u s t to the n o n - r i g i d - substratum takes place along the isogeothermal l i n e of p o t e n t i a l f u s i o n . Mere, according to P r a t t ' s theory, the c r u s t a l segments f l o a t on the "basalt at a depth of 60 m i l e s . Other f i g u r e s given f o r t h i s depth of compensation vary from 25 to 100 m i l e s . Two f a c t o r s , heat and pressure, could cause the sur-face rocks to l o s e t h e i r r i g i d i t y at depth. The former might come from the o r i g i n a l i n t e r n a l heat of the earth or radium d i s i n t e g r a t i o n , the l a t t e r , from the weight of the o v e r l y i n g sediments or l a t e r a l compression, Willis"*" has shown that the pressure of the o v e r l y i n g 1 W i l l i s , B. & HT.""Geolo'gic Str¥clulre;s'Knr929."pp.442-44jT.~ r o c k s - w i l l p o t e n t i a l l y crush at a depth of 40 m i l e s . "Below t h i s depth rocks behave mechanically l i k e p l a s t i c substances but they are not e a s i l y molded i n the sense that our experience w i t h wax or p u t t y suggests." This p l a s t i c substratum has a great e f f e c t on moun-t a i n - b u i l d i n g . Much has been w r i t t e n about the c o n d i t i o n s i n the i n t e r i o r of the earth but i t i s s u f f i c i e n t ,for our purpose, to remember tha t at a depth of the order o f 60 m i l e s the rocks are i n a l i q u i - v i t r e o u s or p l a s t i c c o n d i t i o n . Geosynclines, t h e i r C h a r a c t e r i s t i c s , O r i g i n and Development. Before going on to a d i s c u s s i o n of the development of mountain systems, a short summary of the c h a r a c t e r i s t i c s of the geosynclines from which they are b u i l t i s here i n c l u d e d . I t i s the w r i t e r ' s o p i n i o n t h a t the t a n g e n t i a l or compressive f o r c e s which b u i l t the mountains a l s o aided i n the s i n k i n g of the g e o s y n c l i n e . (1) An abnormal t h i c k n e s s of sediments. Kevin gives the f o l l o w i n g f i g u r e s : 1 Kevin. " S t r u c t u r a l Geology", 1931. P . 2 7 3 . P r o t e r o z o i c (now eroded stumps; 18 ,000 ' 19,000' 50,000' Appalachians 30,000' Himalayas 20,000' Rockies 40,000' (2) N e a r l y a l l s t r a t a i n v olved are shallow water sediments. (a) Sea f l o o r must have been depressed as r a p i d l y as s e d i -ments were deposited. (b) To provide a source f o r the sediments a c o n t i n u a l l y e l e v a t e d land must have e x i s t e d near the slow l y s u b s i -ding b a s i n of d e p o s i t i o n f o r m i l l i o n s of years. \3) These sediments accumulated i n a geosyncline or lon g narrow trough. (a) Geosynclines represent l i n e s of s t r u c t u r a l weakness. |b) C o n t i n u a t i o n of geosynclines f o r m i l l i o n s of years i m p l i e s a c o n t i n u a t i o n of the oauses which make f o r weakness and i n s t a b i l i t y , (e) Cross s e c t i o n s of geosynclines ( i ) are asymmetrical w i t h the steep s i d e towards the d i r e c t i o n of the source of the sediments, ( i i ) the trough has an u n d u l a t i n g character and deep basins i n which the sediments accumulated to an e x c e p t i o n a l t h i c k n e s s . ( i l i j the a x i s of the geosyncline may s h i f t . In the Rockies i t shows a pro g r e s s i v e m i g r a t i o n eastward. •••••-14-6- ; ' ' • • Development of Geosyncline. (1) A depression formed by some cause not connected w i t h sedimentation. Obviously marine sediments cannot accumu-l a t e u n t i l a depression i s there. \2) A c o n t i n u a t i o n of the trough, as has been shown cannot represent a l o c a l downsinking of the c r u s t because of the i n c r e a s i n g load of sediments. Trough would f i l l up q u i c k l y due to i s o s t a t i c balance. (3) There i s some i n d i r e c t connection between the r a t e of d e p o s i t i o n and the r a t e of downsinking of the trough be-cause a c h a r a c t e r i s t i c depth of water i s maintained. O r i g i n of Geosynclines. Several suggestions, a l l i n v o l v i n g very s p e c i a l conditions,have been advanced to account f o r the s u b s i d i n g trough of d e p o s i t i o n . They are (1) For some unknown cause there was a l o s s of mass as m a t e r i a l flowed away to make room f o r the r e l a t i v e l y l a r g e r volume of sediments. This i m p l i e s that the seg-ment was d e f i c i e n t i n weight and f a r from i s o s t a t i c balance which i s d i r e c t l y opposed to the inference that a l a r g e u n i t i s i s o s t a t i c a l l y compensated and n e a r l y con-s t a n t i n mass. (2; U s i n g A i r y ' s ( F i g . 16, page 147.) theory of i s o s t a t i c ad-justment, room f o r the d e p o s i t i o n i n the geosyncline may be made by decreasing the t h i c k n e s s of the c o n t i n e n t a l rock. T h i s , i n the l a s t a n a l y s i s , means a l o c a l i z a t i o n of heat beneath the g e o s y n c l i n a l segment i n order that the rock be fused at a l e s s depth than that at which i s normal-l y would be compensated. F i g . 16. Blocks A i r y " s Hypothesis Thickness d i f f e r e n t d e n s i t y equal ocean f l o o r . l i q u i v i t r e o u s substratum F i g . I ? . P r a t t ' s Hypothesis equal d i f f e r e n t (3) I f P r a t t ' s conception ( F i g . 17, above) i s fo l l o w e d some change i n d e n s i t y should be i n v o l v e d . This might r e s u l t i n a s m a l l way by g r a v i t a t i o n a l compaction and a l s o by c h i l l i n g of the u n d e r l y i n g rock causing i t to c o n t r a c t . Probably t h i s c h i l l i n g i s caused by colder sediments moving downward i n t o the h o t t e r zones at depth. The w r i t e r sees no reason why the thermal c o n d u c t i v i t y of the rocks and the slow r a t e of s i n k i n g should cause compaction of the substratum by c o o l i n g . In f a c t , c o o l i n g of the substratum would b r i n g a corresponding h e a t i n g of the sediments, b a l a n c i n g the compaction of the former by an equal expansion of the l a t t e r . A l s o , f o r compaction to be e f f e c t i v e i n causing continued s i n k i n g of the geosyncline, i t would r e q u i r e the compaction of 10°/o (the d i f f e r e n c e i n S p e c i f i c G r a v i t y between sediments and substratum) of a volume of substratum equal i n volume to the sediments l a i d down. I t i s h a r d l y l i k e l y that such a volume of the substratum would be a f f e c t e d by cooling,so, to o b t a i n the desi r e d e f f e c t i t would r e q u i r e a s t i l l higher percentage of compaction over a reduced volume. Since i t i s h i g h l y improbable that compactions of 10% or over are p o s s i b l e i n the substratum, t h i s cannot be the .cause of continued s i n k i n g of the ge o s y n c l i n e . The w r i t e r wishes to b r i n g forward the ide a that the continued s i n k i n g i s caused by i s o s t a t i c adjustment plus com-pres s i v e f o r c e s a i d i n g the downfolding. As has been shown i n the d i s c u s s i o n of i s o s t a s y , i s o s t a s y can be r e s p o n s i b l e f o r on l y nine-tenths of the a c t u a l s i n k i n g . The w r i t e r b e l i e v e s that compressive f o r c e s account f o r the other t e n t h . T h i s , of course, throws the g e o s y n c l i n a l segment out of i s o s t a t i c ad-justment. I f 50,000 f e e t of sediments were l a i d down i n the Rocky Mountain Geosyncline the segment would then be below i t s p o i n t of adjustment by 5000 f e e t . Yet t h i s i s not ex c e s s i v e . That p o r t i o n s of the cr u s t have been i n s t i l l g reater malad-justment i s shown by the great v e r t i c a l displacements which have r e s t o r e d them to e q u i l i b r i u m . P l a t e a u areas and block f a u l t mountains have o f t e n undergone a v e r t i c a l movement of over 5000 f e e t . Reasons f o r assuming that compressive s t r e s s e s aided i n the s i n k i n g geosyncline are: (1) The s t r u c t u r e i n d i c a t e d that i t i s caused by downfolding r a t h e r than downdropping. (2) Minor f o l d s i n cross s e c t i o n of geosyncline. -149* .. (3) R e l a t i o n of geosyncline to a bordering g e a n t i c l i n e which r e s u l t e d from compressive s t r e s s e s , i . e . the g e a n t i c l i n e -g e o s y n c l i n a l couple. (4) Compressive s t r e s s e s f o r c i n g the segment f a r below the p o i n t of i s o s t a t i c balance give a source f o r the v e r t i c a l u p l i f t which takes place a f t e r the t a n g e n t i a l s t r e s s i s r e l i e v e d i n mountain-building I s o s t a t i c adjustment F i g . 18. I s o s t a t i c + compression adjustment Tensional f r a c t u r e s due to s i n k i n g I f the s i n k i n g were due simply to i s o s t a t i c a d j u s t -ment , i t would r e s u l t i n e i t h e r a downdropping of the segment or i n t e n s i o n along the limbs of the trough. The former would r e s u l t i n a l a r g e normal f a u l t or f a u l t s , e s p e c i a l l y along the border of the old land mass ( F i g . 18, above). The l a t t e r would produce t e n s i o n cracks or flowage along the steep limb i n both the sediments and substratum ( F i g . 19, above). But none of these s t r u c t u r e s are known to be present. I t might be argued that the movement i s w i t h i n the e l a s t i c l i m i t of the rocks, but the t e n s i l e s t r e n g t h o f rocks i s very s m a l l and the d i p from the land mass steep, so that some form o f f a u l t i n g or flowage would take place i f the geosyncline r e s u l t e d only from the l o a d i n g of the sediments. The o n l y p o s s i b l e way sediments can be folded i n t o s y n c l i n e s i s by compressive s t r e s s e s . The s t r u c t u r e of the geosyncline compares w i t h that of a s y n c l i n e which has under-gone s i m i l a r f o l d i n g . The s l i g h t f o l d i n g of the beds of a geosyncline s h o r t l y a f t e r d e p o s i t i o n resembles the s m a l l s t r u c -tures i n a s y n c l i n o r i u m , i n d i c a t i n g compressive s t r e s s e s were present. Only by the a i d of t a n g e n t i a l s t r e s s could the steep limb o f the geosyncline escape f a u l t i n g or flowage. At f i r s t i t seems improbable that compression could be r e l i e v e d by downward movement, however nine-tenths of the s i n k i n g can be accounted f o r by the l o a d i n g of the sediments. The i n i t i a l d i p of the geosyncline and the i n i t i a l movement are then downwards, r e n d e r i n g the downward component of the t a n g e n t i a l s t r e s s more e f f e c t i v e . Geosynclines u s u a l l y , i f not always, o r i g i n a t e from the remnant of former geosynclines which have been i n v o l v e d i n mountain-building, e.g. Rocky mountain geosyncline o r i g i n a t e d i n the remnant of the P u r c e l l g eosyncline. A l b e r t a geosyncline o r i g i n a t e d i n the remnant of the Rocky mountain geosyncline. Alps geosyncline o r i g i n a t e d i n the remnant of the Jura mountain geosyncline. These ranges or g e a n t i c l i n e s are the r e s u l t of compressive s t r e s s e s . The w r i t e r b e l i e v e s that the forces were not e n t i r e l y r e l i e v e d i n mountain-building but continued to act on the succeeding g e o s y n c l i n e s . Another p o i n t i n favour of having compressive s t r e s s e s f o r c e the geosyncline below i t s p o i n t of e q u i l i b r i u m i s that i t provides a source f o r the v e r t i c a l u p l i f t which f o l l o w s the r e l i e f of t a n g e n t i a l s t r e s s . I t would seem that when the f o l d i n g and f a u l t i n g have taken place the compressive s t r e s s e s no longer were s t r o n g enough to prevent i s o s t a t i c ad-justment and v e r t i c a l s t r e s s e s brought the g e o s y n c l i n a l prism, now mountain b u i l t , i n t o e q u i l i b r i u m . Thus l o a d i n g o f sediments plus compressive s t r e s s e s can be shown to account f o r the continued s i n k i n g of geosyn-c l i n a l prisms. F l u c t u a t i o n s between the two f o r c e s would cause the v a r i a t i o n s i n the depth of the geosyncline and r e s u l t i n the d i f f e r e n t types of sediments found t h e r e i n . The d i f f i -c u l t y i s to e x p l a i n why the t a n g e n t i a l f o r c e . p l u s l o a d i n g , caused s i n k i n g at n e a r l y the same r a t e as d e p o s i t i o n i n order that the n e a r l y continuous s e r i e s of shallow water sediments be l a i d down. There are two p o s s i b i l i t i e s : (1) That the t a n g e n t i a l s t r e s s was n e a r l y constant or s l o w l y i n c r e a s i n g . This would give a f i x e d r a t i o between the f o r c e s of l o a d i n g and compression which might give a gradual s i n k i n g . (2) I t i s p o s s i b l e that the depth of the waters d i d f l u c t u a t e considerably.. There were periods of u p l i f t and other times of deeper water between which there might have been a d i f f e r e n c e of e l e v a t i o n of the order of 3000 f e e t . The d i r e c t connection between the r a t e of d e p o s i t i o n and the r a t e of downsinking i s brought about by the j o i n t a c t i o n of i s o s t a t i c adjustment and compressive f o r c e s and i s a s s o c i a t e d w i t h the continued e l e v a t i o n of the land mass from which the sediments were d e r i v e d . Types o f Deformation found i n the Rockies. For a d i s c u s s i o n of the types of f a u l t i n g and f o l d -i n g found i n mountain systems the reader i s r e f e r r e d to any text-book on S t r u c t u r a l Geology. I t i s here s u f f i c i e n t to note that the Rockies show deformation of a type intermediate between the great recumbent f o l d s and nappes of the A l p s , on the one hand, and the i n c l i n e d f o l d i n g and high-angle f a u l t i n g of.the Appalachians • -on the other. However, the w r i t e r wishes to b r i n g forward an e x p l a n a t i o n of the normal f a u l t i n g found near the a x i s of such f o l d mountains as the Rockies,and to d i s c u s s high-angle f a u l t i n g . Normal F a u l t i n g near the axes of F o l d Mountain Systems. The t h r u s t s along the borders of such ranges as the Rockies, the Alps and the Himalayas are e a s i l y explained as being the r e s u l t of deformation under compressive f o r c e s . 1'he presence of normal f a u l t s showing an a p p a r e n t l y progressive downdropping towards the a x i s of the range i s more d i f f i c u l t to e x p l a i n . They are commonly supposed to be formed during a per i o d of tension which f o l l o w s the mountain-building. The w r i t e r b e l i e v e s that these normal f a u l t s are the r e s u l t of the same compressive s t r e s s e s which caused the other s t r u c -tures and that they do not r e s u l t from a l a t e r period of • •' -153- • t e n s i o n , although i s o s t a t i c adjustments may play some part i n t h e i r o r i g i n * The causes f o r t h i s supposed p e r i o d of t e n s i o n have always been hard to f i n d . The common ex p l a n a t i o n i s t h a t , i n mou n t a i n - b u i l d i n g , as the accumulated compressive s t r e s s e s were r e l i e v e d by deformation, the rocks i n v o l v e d passed through the c o n d i t i o n of no s t r e s s i n t o a stat e of t e n s i o n . This r e q u i r e s t h a t the mass moved by the compressive s t r e s s e s a c q u i r e d s u f f i c i e n t i n e r t i a or momentum to c a r r y i t beyond the point of e q u i l i b r i u m so th a t a s t a t e of t e n s i o n re s u i t e d . This t e n s i o n s t r e s s was r e l i e v e d by normal f a u l t i n g . But t h i s does not s a t i s f y the g e o l o g i c a l f a c t s or the mechanics of mountain-building. The Rockies, f o r i n s t a n c e , were b u i l t so s l o w l y that the r i v e r s were able to maintain t h e i r channels acr o s s the r i s i n g mountain systems and thus form the tr a n s v e r s e passes. Because of the great f r i c t i o n and the slow movement ,the mass i n v o l v e d would then gather i n s u f f i -c i e n t i n e r t i a or momentum to ca r r y i t beyond the point o f e q u i l i b r i u m i n t o a s t a t e of tension;but would stop before the compressive s t r e s s e s were e n t i r e l y r e l i e v e d . I s o s t a t i c adjustments, from a g e o l o g i c a l point o f view, have been shown to be e f f e c t i v e o n l y over l a r g e areas of approximately 2 0 0 m i l e s diameter and t h e r e f o r e could account f o r the c l o s e spacing of normal f a u l t s and the adjustments between the f a u l t b l o c k s . N e v e r t h e l e s s , great maladjustments of i s o s t a t i c e q u i l i b r i u m over small areas, - a c o n d i t i o n which might occur i n mountain systems - would l e a d to the eompensation of s m a l l e r areas and thus be a p o s s i b l e cause of the normal f a u l t i n g . As has been shown i n g e n e r a l i z e d s e c t i o n s across the Roc k i e s , the planes of both the t h r u s t and normal f a u l t i n g d i p towards the s t r u c t u r a l a x i s of the range i n a f a n - l i k e arrangement. T h i s , i n i t s e l f , suggests a common o r i g i n f o r the two types of f a u l t i n g , i . e . both t h r u s t and normal f a u l t s r e s u l t from the compressive s t r e s s e s . In the Rockies the c r u s t a l s h ortening has taken place i n the bor d e r i n g B e l t s of t h r u s t s and close f o l d i n g . There, along the low-angle f a u l t planes, the e a s i e s t r e l i e f was h o r i z o n t a l . As one approaches the a x i s o f the range a point i s reached where there i s a decrease i n the l a t e r a l move-ment along the high-angle f a u l t planes. For example, i n F i g . 20 (below), the b l o c k s A, B and C have moved s u c c e s s i v e l y F i g . 20. Diagram showing r e l a t i v e movement of f a u l t b l o c k s i n the Rockies. A l l blo c k s moved upwards, g r e a t e r l a t e r a l movement of bordering b l o c k s . f a r t h e r , producing t h r u s t f a u l t s , but block D has, because of the h i g h e r angle of the f a u l t plane, moved r e l a t i v e l y l e s s than b l o c k C and so produced a normal f a u l t . S i m i l a r l y a normal f a u l t e x i s t s between blocks D and E because of the l e s s e r movement of block E. So as one approaches the a x i s the decreased movement w i l l produce normal f a u l t s w i t h the upthrow away from the a x i s , 1 I t i s i n t e r e s t i n g to note that Chamberlin obtained the same 1 "Chamberlin, R.T. J o u K of QeoTTTTolTJT, IJd^rihTST* s t r u c t u r e s i n experimenting with h i s wedge theory but d i d not c o r r e l a t e the normal f a u l t s with those found along the c e n t r a l b e l t of the Rockies. Furthermore Rocky mountain s t r u c t u r e i n d i c a t e s i t was b u i l t as a u n i t . I f the compressive p e r i o d was f o l l o w e d by one of t e n s i o n there would be evidence of t e n s i o n a l normal f a u l t s c u t t i n g the close f o l d i n g and o v e r t h r u s t i n g caused by the e a r l i e r t a n g e n t i a l s t r e s s . That such s t r u c t u r e s are l a c k i n g i s good evidence t h a t these mountains were b u i l t as a u n i t and owe t h e i r present s t r u c t u r e s almost e n t i r e l y to compressive s t r e s s e s . The s l i g h t f o l d i n g which has a f f e c t e d the T e r t i a r y sediments of the F l a t h e a d v a l l e y and the P l a i n s i s f u r t h e r i n d i c a t i o n t h a t the compressive s t r e s s e s are never e n t i r e l y r e l i e v e d f o l l o w i n g the mountain-building. . Summary o f evidence i n d i c a t i n g that normal f a u l t i n g , when developed i n the c e n t r a l b e l t of such fold-mountain systems as the Rockies, i s the r e s u l t of compressive s t r e s s e s . (1) I n a b i l i t y f o r t e n s i o n a l s t r e s s e s to develop as the com-pr e s s i v e s t r e s s e s are never e n t i r e l y r e l i e v e d . (2) I s o s t a t i c adjustments are e f f e c t i v e only over f a i r l y l a r g e - 1 5 - ^ areas and so cannot be the cause of the r e l a t i v e l y close normal f a u l t s . (3) The dips of f a u l t planes on both s i d e s increase towards the centre of the range* (4) There i s no evidence of the normal f a u l t i n g c u t t i n g across the c l o s e f o l d i n g and o v e r t h r u s t i n g such as would be expee t e d i f the normal f a u l t s were the r e s u l t of a l a t e r p e r i o d of t e n s i o n . (5) The f o l d i n g of post orogenic sediments adjacent to the mountains i n d i c a t e s there was no complete r e l i e f of com-p r e s s i o n . High-angle t h r u s t - f a u l t s . Two types of high-angled t h r u s t s are found i n the Rockies. They are (1) The Rocky mountain type, having d i p s averaging 50 . (2) The F o o t h i l l s type, having steeper dips and w e s t e r l y d i p p i n g s t r a t a i n the f a u l t b l o c k s . In the Rockies shear planes seem to have f0rmed f i r s t at com-p a r a t i v e l y steep angles (see F i g . 21, page 157) » These f a u l t b l o c k s p i l e d up one above the other u n t i l e a s i e r r e l i e f was found along the low angle f a u l t planes such as the l e w i s thrus The whole mass then rode forward on these low-angle t h r u s t s . Such s t r u c t u r e s are c h a r a c t e r i s t i c of the S c o t t i s h highlands. In the F o o t h i l l s d r i l l i n g has shown that many of the t h r u s t s which have very high angles on the surface f l a t t e n out at depth. These f a u l t s are b e l i e v e d to j o i n a " s o l e " f a u l t at no -157-great depth. The c h a r a c t e r i s t i c westward dip of the s t r a t a i s e x p l a i n e d by the r o t a t i o n a l t h r u s t of the f a u l t b locks above t h i s low-angle f a u l t , as shown i n F i g . 2 2 , below. F i g . 21. High-angle t h r u s t s - Rockies type. F i g . 22. High-angle t h r u s t s - F o o t h i l l s type. => The Development of the Rooky Mountain Trench. 1 -Daly and S c h o f i e l d b e l i e v e d that the Trench i s a 1 Daly, R.A. G.S.C. Mem.3H, p.118. " — " ~ ~ ~ ~ ~ ~ 2 S c h o f i e l d , S.J. T.R.S.C., 1 9 2 0 , p . 7 6 .  u n i t i n i t s development and s t r u c t u r e . The former e v i d e n t l y considered i t a g r a b e n - l i k e s t r u c t u r e produced by normal f a u l t i n g ; the l a t t e r recognized i t s h i g h l y complex nature, that the Trench was bordered i n some places by t h r u s t s towards the Trench, i n others by normal f a u l t s and sometimes by f o l d i n g without apparent f a u l t i n g . Shepard l a t e r p o s t u l a t e d that the 3 ShepardT F.P. J o u r , of G~eoT. , Vol.XXX, 1 9 2 2 , pp. 1 3 0-140. -1J58-Trench, i n s t e a d of developing as a u n i t , was produced p a r t l y by normal e r o s i o n , p a r t l y by e r o s i o n along l i n e s of s t r u c t u r a l . weakness, and p a r t l y by the escarpment of a f a u l t . Between Canal F l a t s and B u l l r i v e r there i s found, i n the Rockies, formations of the P u r c e l l s e r i e s t h r u s t over the P a l a e o z o i c limestones by a t h r u s t from the west. This f a u l t i s undoubted-l y r e l a t e d to the b u i l d i n g of the P u r c e l l mountains. Shepard cons i d e r s t h i s as evidence that the Trench i s not g e n e t i c a l l y a s s o c i a t e d w i t h the b u i l d i n g of the Rockies. The w r i t e r sees no reason why the J u r a s s i d e mountains could not have extended acr o s s the present s i t e of the Trench,in t h i s area,and then have been i n v o l v e d i n the b u i l d i n g of the Trench and Rockies i n the laramide R e v o l u t i o n . The w r i t e r b e l i e v e s that the Trench i s due to the same compressive s t r e s s e s which b u i l t the Rockies r a t h e r than to t e n s i o n or r e l e a s e of the s t r e s s e s and i t does not seem p o s s i b l e f o r such a f e a t u r e to have been produced by e r o s i o n . Before the laramide r e v o l u t i o n the J u r a s s i d e mountains must have extended i n a f a i r l y s t r a i g h t l i n e along the border of the Rocky mountain g e o s y n c l i n e . I n very general terms, j u s t pre-v i o u s to the b u i l d i n g of the Rockies, the a n t i c l i n o r i a of the J u r a s s i d e , P u r c e l l , S e l k i r k and F i n d l a y mountains l a y along the western border of the geosyncline as a f o l d on a sheet of paper. When, i n the laramide r e v o l u t i o n , the Rockies were b u i l t w i t h t h e i r a x i s along the deepest part of the Rocky mountain g e o s y n c l i n e , they appear as a second f o l d on the paper, while the Rocky Mountain Trench l a y as the hollow between them. To account f o r the o r i g i n of the Trench one would f i r s t , then, have to be able to e x p l a i n the l o c a t i o n of the geosyncline and i t s remarkable s t r a i g h t n e s s . In attempting to e x p l a i n the o r i g i n of the Trench by compression we are concerned mostly w i t h the eastern side of the Trench bordering the Roeky mountains. The western border of the Trench antedates i t and was i n existence as the eastern f r o n t of the J u r a s s i d e mountains probably i n much the same p o s i t i o n as i t i s today. There, f o l d i n g i s common but i n at 1 east two places o v e r t h r u s t i n g f a u l t i n g from the west has taken place i n a manner s i m i l a r to the t h r u s t i n g along the eastern f r o n t of the Rockies. S t r u c t u r e s are oft e n continuous across the Trench to the Rocky mountains. In other places the eastern border i s marked by the overturned f o l d i n g and t h r u s t i n g towards the west along the f r o n t of the Rockies. These s t r u c t u r e s are c l e a r l y the r e s u l t of compressive s t r e s s e s . I t i s t h e r e f o r e c l e a r that a great part of the l e n g t h of the Trench has r e s u l t e d from compressive s t r e s s e s t h r u s t i n g to the west out of the Rocky mountains. The d i f f i c u l t y a r i s e s i n t r y i n g t o e x p l a i n f a u l t s 1 mapped as normal by Daly along the eastern boundary of the T~ See~structurT~s^ot i o n , "page Trench i n the v i c i n i t y of the 4?th p a r a l l e l . These are h i g h -angled f a u l t s , the planes of which have been mapped as dipping s l i g h t l y towards the Trench. Much of t h i s i s work Daly h i m s e l f considered h y p o t h e t i c a l . I f these f a u l t s planes dipped -lbp-s l i g h t l y away from the Trench they would become t h r u s t f a u l t s , t h e i r h i g h a n g l e due t o e a s i e s t r e l i e f b e i n g v e r t i c a l r a t h e r t h a n h o r i z o n t a l . The b u t t r e s s i n g e f f e c t o f the P u r c e l l s t o the west would produce such c o n d i t i o n s . 1 T h i s , Shepard c o n s i d e r s to be the cas e . He t r a c e d 1 ~opT"~c i^t". ~ ~ p . 1 3 b . ~ the f a u l t i n q u e s t i o n f o r s e v e r a l m i l e s and found the f a u l t p l a n e to cu r v e to the e a s t up a t r i b u t a r y v a l l e y . T h i s i s good e v i d e n c e , o f cour s e , o f an e a s t e r l y d i p p i n g f a u l t p l a n e . As the upthrow i s on the e a s t the r e l a t i o n i s t h a t o f a t h r u s t f a u l t r e s u i t i n g f r o m c o m p r e s s i o n from the c e n t r e o f the r a n g e s . Much more d e t a i l e d work w i l l have t o be done i n the T r e n c h and a l o n g i t s b o r d e r s , e s p e c i a l l y n o r t h o f G o l d e n , b e f o r e any v e r y d e f i n i t e i d e a can be had o f i t s s t r u c t u r e s and t h e i r o r i g i n . The Development o f F o l d M o u n t a i n Systems. 2 The f o l l o w i n g o u t l i n e , a f t e r Peacock and m o d i f i e d 2 Peacock~7""MT S t r u c T u r a T G e o l o g Y T ^ ^ ^ T ^ 3 0 - 3 1 . ZZZ by the w r i t e r , i s an a t t e m p t to show the development o f a f o l d m o u n t a i n system such as the A l p s o r R o c k i e s i n the l i g h t o f p r e s e n t day knowledge o f c r u s t a l d e f o r m a t i o n and the s u b s t r a t u m . legend f o r f i g u r e s 2 3 - 2 8 . sediments O granite ® basalt O fused •» O fused " © fused " O -161-F i g . 23. Showing sudden change f r o m g r a n i t e t o "basalt a t dep t h o f 40 m i l e s . I - I s o g e o t h e r m a l l i n e o f p o t e n t i a l f u s i o n ; a l l r o c k s "below t h i s l i n e are l i q u i - v i t r e o u s , i . e . thes e r o c k s are m e c h a n i c a l l y weak, n o n - c r y s t a l l i n e ( g l a s s y ) . F u s i o n w i l l t a k e p l a c e w i t h o u t the l a t e n t he at of f u s i o n . They have r i g i d i t y t o s u d d e n l y i m p l i e d i m p a c t , b u t are weak to l o n g a p p l i e d s m a l l s t r e s s e s . F i g . 24. Note gradual shortening of the s e c t i o n . Sediments from o l d l a n d mass d e p o s i t e d i n the slo w w a r p i n g due to c o n t r a c t i o n . S i n c e downward -262-moveraent i s s l o w the I s o g e o t h e r m a l s u r f a c e w i l l r e m a i n s t a t i o n a r y . The c o n t r a o t i o n more l i k e l y r e s u l t s from com-p r e s s i v e s t r e s s e s than from g r a v i t a t i o n a l f o r c e s o r i s o s t a t i c e q u i l i b r i u m . The t r o u g h becomes a geo-s y n c l i n e w i t h a l m o s t c o n t i n u o u s s e d i m e n t a t i o n . The t h i c k n e s s o f b a s a l t above t h e I s o g e o t h e r m a l l i n e i s l e s s e n e d under the g e o s y n c l i n e and p r o b a b l y i n c r e a s e d a l o n g the edges as t h e l i q u i - v i t r e o u s s u b s t r a t u m a d j u s t s i t s e l f t o the new c o n d i t i o n s . age 3. ( C r i t i c a l S t a g e ) C o n t i n u e d c o m p r e s s i o n and s e d i m e n t a t i o n i n the geo-s y n c l i n e . The s t r e n g t h o f t h e t r o u g h i s now g r e a t -l y weakened. That p a r t o f t h e g r a n i t e below the I s o g e o t h e r m a l l i n e i s now i n the f u s i o n o r e r u p t i c a l s t a t e . The s i n k i n g w i l l c o n t i n u e u n t i l the s t r e n g t h o f t h e g r a n i t e arid s e d i m e n t s has d e c r e a s e d u n t i l i t j u s t e q u a l s the c r u s h i n g or t a n g e n t i a l s t r e s s . -163-Stage 4. ( C o l l a p s e w i t h b a t h o l i t h i c i n t r u s i o n ) F i g . 26. When c o l l a p s e o c c u r s i t w i l l be r e l a t i v e l y sudden. The c r y s t a l l i n e g r a n i t e and perhaps some o f the f o l d e d s e d i m e n t s a r e downthrust o r downfolded i n t o t h e l i q u i - v i t r e o u s s u b s t r a t u m . I f there i s con-s i d e r a b l e s h o r t e n i n g s o l i d m a t e r i a l must be f o r c e d down i n t o the l i q u i - v i t r e o u s s u b s t r a t u m . T h i s r e -s u l t s i n l i g h t e r g r a n i t e " f l o a t i n g " on the b a s a l t i c s u b s t r a t u m so the f u s e d g r a n i t i c m a t e r i a l pushes i t s way up i n t o the s e d i m e n t a r y s e r i e s , t h a t i s , t h e r e i s g r e a t b a t h o l i t h i c i n t r u s i o n l e a d i n g t o t h e em-placement o f g r a n i t e o r g r a n o d i o r i t e r o c k s i n t o the c o r e s o f the f o l d e d s e d i m e n t s . N o t e . T h i s s-Sage i s g e n e r a l l y c o n s i d e r e d as p r o -d u c i n g o n l y the mount a i n s t r u c t u r e s w i t h o u t g r e a t e l e v a t i o n s . -164 Stage 5 . ( U p l i f t ) — v \ \*\ F i g , 27. T h i s i s t h e s t a g e of i s o s t a t i c r e c o v e r y . F o l l o w i n g the r e 1 i e f o f t a n g e n t i a l s t r e s s e s v e r t i c a l u p l i f t t a k e s p l a c e because the mountain mass i f below i t s p o i n t o r l e v e l o f e q u i l i b r i u m . The whole m o u n t a i n mass i s c o n s i d e r e d as r i s i n g as a u n i t because g e o l o g i c a l e v i d e n c e shows t h a t o n l y a r e a s 200 m i l e s o r more i n w i d t h are i s o s t a t i c a l l y compensated. The l i g h t m a t e r i a l o f f u s e d g r a n i t e beneath the g e o s y n c l i n e must f l o a t on the b a s a l t i c l i q u i -v i t r e o u s l a y e r . Thus the mountain ranges are e l e v a -t e d because o f the s p e c i f i c a l l y l i g h t e r g r a n i t i c m a t e r i a l b e n e a t h them. Stage 6. ( V u l c a n i s m ) F o l l o w i n g the c o l l a p s e and d u r i n g i s o s t a t i c a d j u s t -ment f i s s u r e e r u p t i o n s t a k e p l a c e . Most g e o l o g i s t s c o n s i d e r t h i s a p e r i o d o f t e n s i o n w i t h normal f a u l t i n g and r e a d j u s t m e n t o f the f a u l t b l o c k s . As d i s c u s s e d above the w r i t e r b e l i e v e s t h e normal f a u l t s a l o n g the a x i s of the Rockies to be produced by the same compressive s t r e s s e s as made the o v e r f o l d i n g and t h r u s t - f a u l t i n g , and that the compressive s t r e s s e s were not e n t i r e l y r e l i e v e d by mountain-building. Tension f a u l t s could be produced along the border of the mountain system due to the upwarping of the mass as a u n i t and account f o r the e x t r u s i o n s which f o l l o w v e r t i c a l up-l i f t . Stage 7• E r o s i o n w i t h probably repeated u p l i f t s or i s o s t a t i c adjustments. The Development of the Rooky Mountain S t r u c t u r e . Evidence i s strong t h a t the Rocky mountains f o l l o w e d the development of f o l d mountain systems o u t l i n e d i n the preceding pages (pp. 160-16.5) • I n i t i a l f o l d s i n the bottom of the geosyncline probably have c o n t r o l l e d the l a t e r mountain s t r u c t u r e s to some ex t e n t . The present s t r u c t u r e s (see F i g . IB, page 166) show-a l l the evidences of a two-sided orogeny. That the mountain-b u i l d i n g i s not symmetrical i s probably due to the e a s i e s t r e l i e f of the t a n g e n t i a l s t r e s s being towards the shallower part of the g e o s y n c l i n e , r a t h e r than to the west where the steep western limb of the geosyncline and the competent J u r a s s i d e mountains had a b u t t r e s s i n g e f f e c t and prevented great over--166-f o l d i n g and o v e r t h r u s t i n g along the western f l a n k o f the Rockies. Also r e l i e f under the compressive s t r e s s e s was much e a s i e r to the east because there the ov e r t h r u s t s could t r a v e l along the g e n t l e w e s t e r l y - d i p p i n g s t r a t a of the eastern limb f a r more r e a d i l y than they could along the steep s t r a t a of the western l i m b . A b a t h o i i t h has very probably been i n t r u d e d along the a x i s of the Rockies but has not yet been unroofed by e r o s i o n . F i g . -8. G e n e r a l i z e d c r o s s s e c t i o n . Rockies The s t r u c t u r e s i n d i c a t e a s i n g l e period of deforma-t i o n . E i t h e r the present e l e v a t i o n s of the Rockies are due to v e r t i c a l u p l i f t contemporaneous w i t h the development of moun-t a i n s t r u c t u r e or the whole area was u p l i f t e d as a u n i t . The remnants of the o l d peneplaned surface i n the S e l k i r k s and the gradual r i s e of the p r a i r i e l e v e l towards the mountains i n d i -c ates that the Rockies underwent no deformation as a r e s u l t of d i f f e r e n t i a l u p l i f t . -167~ The Development o f St rupture i n the Mackenzie mountains and  associated, rangeso The northern ranges have been said, to possess t y p i Rocky mountain s t r u c t u r e . They are made of asymmetrical a n t i c l i n e s w i t h g e n t l e western and steep eastern limbs i n d i c a t i n g t h a t they, l i k e the E a s t e r n B e l t of the Rockies, were b u i l t by a t h r u s t from the west a But they d i f f e r from them i n that the a n t i c l i n e s have normal f a u l t s w i t h eastward d i p p i n g planes along t h e i r axes, g i v i n g the appearance of hinge f a u l t i n g f o r e i g n to the Rockies. ABBREVIATIONS. B.G.S.A. - B u l l e t i n of the G e o l o g i c a l S o c i e t y of America. B.A.A.P.G. - B u l l e t i n of the American A s s o c i a t i o n of Petroleum G e o l o g i s t s . G.S.C., Summ.Rept. - G e o l o g i c a l Survey of Canada, Summary Report. G.S.C., Ann.Rept. - G e o l o g i c a l Survey of Canada, Annual Report. G.S.C. Mem. - G e o l o g i c a l Survey of Canada, Memoir. Jour, of Geol. - J o u r n a l of Geology. Rept. - Report. Sect. - S e c t i o n . S.I.R.C.A. - S c i e n t i f i c and I n d u s t r i a l Research C o u n c i l of A l b e r t a . T.C.I.M.M. - Transactions of the Canadian I n s t i t u t e of Mining and M e t a l l u r g y . T.R.S.C. - Transactions of the Royal S o c i e t y o f Canada. U.S.G.S. - United States G e o l o g i c a l Survey. i BIBLIOGRAPHY. A l l a n , J.A. "Rocky Mountain s e c t i o n between Banff, A l b e r t a and Golden, B.C., along the C.P.R." G.S.C., Summ.Rept., 1912. "Rocky Mountains, Bankhead to Golden." G.S.C. Guide Book Ho. 8, 1913* "Geology of the F i e l d Map-Area, B.C." G.S.C. Mem. 55, 1914. "The Geology of the Rocky Mountains." Canadian A l p i n e J o u r n a l , 1917. "A P r e l i m i n a r y study of the East e r n Ranges of the Rocky Mountains i n Jasper Park, A l b e r t a . " T.R.S.C,, Vol.XXVI, Sect.IV, 1932. "Saunders Creek and Nordegg Coal Basins, A l b e r t a , Canada." S.I.R.C.A. Rept. No. 6, I 9 2 3 . "Geology along the Blackstone, Brazeau and Pembina H i v e r s , i n the F o o t h i l l s B e l t , A l b e r t a . " S.I.R.C.A., Rept. No. 9, 1924. A l l a n , R u t h e r f o r d , and Warren. A l l a n , J.A. and R u t h e r f o r d , R.L. Bevan, A. Rocky Mountain Front i n Montana." B.G.S.A., V o l . 40, I 9 2 9 . Bocock, J.B. See under W i l l i a m s , M.Y. Burwash, E.M. "Geology of the Canadian Rocky Mountains." Can. A l p i n e J o u r n a l , V o l . 2, 1920. -BIBLIOGRAPHY (co n t i n u e d ) . Burwash, E.M. (continued) "Orogenic and Physiographic H i s t o r y of the Rocky Mountain Geosyncline." Can. A l p i n e J o u r n a l , V o l . 2, 1920. Campbell, M.R. U.3.G.S. B u l l . 600. Camsell, C. and Malcolm, W. "The Mackenzie R i v e r B a s i n . " G.S.C. Mem. 108, 1921. Gairnes, D.D. "Moose Mountain D i s t r i c t , Southern A l b e r t a . " G.S.C. Mem. 61, 1914. Chamberlin, R.T. "The Wedge Theory o f Diastrophism." Jour, of Geol., V o l . 32, No. 7, 1924. C o l l e t , L.W. "Le Canada et ses Montagnes Rocheuses." B x t r a i t de l a Revue du Club A l p i n Suisse "Les Alp e s " , No. 9 & 10, 1932. C o l l e t , L.W. et P a r e j a s , B. " R e s u l t a t s de l ' E x p e d i t i o n Geologique de l' H n i v e r s i t e de Harvard dans Les Montagnes Rocheuses du Canada.('Jasper N a t i o n a l Park, 1 9 2 9 ) . " E x t r a i t s du Compte Rendu des Seances de l a So c i e t e de Physiaue et d ' H i s t o i r e n a t u r e l l e d Geneve, V o l . 47 , 1930; V o l . 49, 1932. Cummings, J . "Pre-Laramide Formations of the Rocky Mountains." Th e s i s , U.B.C., I 9 3 3 . Daly, R.A. "Geology of the North American C o r d i l l e r a at the 4 9 t h P a r a l l e l . " G.S.C. Mem. 38, 1912. "A G e o l o g i c a l Reconnaissance between JLamloops and Golden, B.C., along the C.P.R." G.S.C. Mem. 68, 1915. BIBLIOGRAPHY ( o on t i nue a V. Dawson, G.M. " P r e l i m i n a r y Report on the P h y s i c a l and G e o l o g i c a l Features o f that p o r t i o n of the Rockies "between L a t i t u d e s - 4 9 ° and 51° 31'.» G.S.C. Ann.Rept., V o l . 1> I 8 8 5 . " G e o l o g i c a l Record of the Rocky Mountain Region i n Canada." B.G.S.A,, V o l . 12, 1901. DoImage, V. " F i n d l a y R i v e r D i s t r i c t , B.C." G.S.C. Summ.Rept., Pt.A, 1927. Dowling, D.B, "The E a s t e r n B e l t of the Canadian C o r d i l l e r a s . An Enqu i r y i n t o the age of deformation." T.R.S.C., Vol.XVI, 1922, F l i n t , "A B r i e f Review of Rocky Mountain S t r u c t u r e , " Jour, of Geol.- V o l . 32, 1929. Hume, G.S, J o l y , J, Keele, J , "North Nahanni and Root R i v e r areas, Mackenzie R i v e r D i s t r i c t . " G.S.C. SumnuRept., 1921, P t . B. "Geology of the Norman o i l f i e l d s and a Reconnais-sance o f a p a r t of L i a r d R i v e r . " G.S.C. Summ.Rept., 1922, P t . B. "Mackenzie R i v e r Area, N.W.T." G.S.C. Summ.Rept., 1923, P t . B. "The Surface H i s t o r y of the Ear t h " - 1925. "A Reconnaissance across the Mackenzie mountains on the P e l l y , Ross and Gravel r i v e r s , Yukon and N.W.T." G.S.C, 1910. BIBLIOGRAPHY (c o n t i n u e d ) . K i n d l e , E.M. "A Standard P a l a e o z o i c s e c t i o n of the Rocky Mountains near Banff, A l b e r t a . " Pan-American G e o l o g i s t , V o l . 42, 1924. Leach, W.W. "Geology o f the Blairmore Map Area, A l b e r t a . " G.S.C. Summ.Rept., 1911. ' L i n k , T.A. "The A l b e r t a geosyncline." B.A.A.P.G. McConnell, R.G. "Report on the G e o l o g i c a l Features of a P o r t i o n of the Rocky Mountains accompanied by a s e c t i o n measured near the 51st P a r a l l e l . " G.S.C. Ann.Re-ot., 1886, P t . D. Mc'Evoyi J,. "Summary of an E x p l o r a t i o n by the Yellowhead Pass from Edmonton, A l b e r t a , to Tete-Jaune Cache, B.C." G.S.C. Ann.Rept., I 8 9 8 , P t . A. MacKay 9 B.R. "Jasper Park C o a l f i e l d s . " T.C.I.M.M., Oct. 1930. M a l l o c h , G.S. "Bighorn Coal Bas i n . " G.S.C. Mem. 9 , 1911. Malcolm, W. See Camsell, C. M a r s h a l l , J.R. "Upper E l k R i v e r V a l l e y , B.C." G.S.C. Summ.Rept., 1920, P t . B. Nevin, CM. " S t r u c t u r a l Geology," 1931. BIBLIOGRAPHY ( c o n t i n u e d ) . P a r e j a s , B» See C o l l e t , L.W. et Pa r e j a s , E. Peacocks, M. S t r u c t u r a l Geology. U.B.C., 1931. P o l l o c k , J.R. "The Structure- of the Rocky Mountain Trench." T h e s i s , U.B.C., 1926. Ransoms, F.L. "The T e r t i a r y Orogeny of the North American C o r d i l -l e r a and i t s Problems." Problems of American Geology, 1915. Raymond, P.E. and W i l l a r d , B. "A S t r u c t u r e s e c t i o n across the Canadian Rockies." Jour, off Geol., V o l . XXXIX, No.2, 1931. Rose, B. "Blairmore Map-area, A l b e r t a . " G.S.C. Summ.Rept., 1915. "Highwood Coal Area, A l b e r t a . " G.3.C. Summ.Rept., 1919. " S t r u c t u r e i n the Crowsnest Coal Area, A l b e r t a . " T.C.I.M.M., V o l . XXVII, 1924. Ru t h e r f o r d , R.L. "Geology of the F o o t h i l l s - B e l t , between McLeod and Athabasca R i v e r s , A l b e r t a . " S.I.R.C.A., Rept. N o . l l , I 9 2 5 . "Geology along the Bow R i v e r between Cochrane and Kananaskis, A l b e r t a . " S.i.R.C.A., Rept. No.17, 1927. (See A l l a n , J.A. and Rutherford, R.L.) S c h o f i e l d , S.J. "The O r i g i n of the Rocky Mountains." Science Conspectus, V o l . 4, 1914. BIBLIOGRAPHY (c o n t i n u e d ) . S c h o f i e l d . S.J. (continued) "Geology of the Cranbrook Map-Area." G.S.C. Mem. 7&, 1915. "The O r i g i n o f the Rocky Mountain Trench." T.R.S.C, V o l . 14, Sect. IV, 1?20. "The G e o l o g i c a l Record of the C o r d i l l e r a i n Canada. T.R.S.C., V o l . 17, Sect. IV, I 9 2 3 . Shepard,•P.P. "Problems i n S t r a t i g r a p h y along the Rocky Mountain Trench." Jour, of Geol., Vol. 3 0 , No.3, 1922. ."Further I n v e s t i g a t i o n s i n the Rocky Mountain Trench." Jour, of Geol., V o l . 39, 1926. Stewart, J.S. "Geology of the Dis t u r b e d B e l t of Southwestern A l b e r t a . " G.S.C. Mem. 112, 1919. Thorne, H.L. "Turner V a l l e y . " T h e s i s , U.B.C., 1 9 3 3 . Walcott, C D . "Pre-Devonian P a l e o s o i c Formations of the Rockies." Smithsonian M i s c e l l a n e o u s C o l l e c t i o n , V o l . 7 3 , 1928. Walker, J.F. "Geology and M i n e r a l Deposits of the Windermere Map-area, B.C." G.S.C. Mem. 148, 1926. Warren, P.S. "A composite s e c t i o n near the $ l B t p a r a l l e l . " Can. F i e l d N a t u r a l i s t , V o l . 4 3 , 1929, pp.23-27. See A l l a n , Rutherford and Warren. "Banff Area, A l b e r t a . " G.S.C. Mem. 153, 1927. BIBLIOGRAPHY (c o n t i n u e d ) . Whittaker„ E.J. "Mackenzie R i v e r D i s t r i c t between Great Slave Lake and Simpson." G.S.C. Summ.Rept., 1921, P t . B. W i l l a r d , B. See Raymond and W i l l a r d . W i l l i a m s , M.Y. " E x p l o r a t i o n east of the Mackenzie R i v e r between Simpson and Wrigley." G.S.C. Summ.Rept. 1921, P t . B. "Reconnaissance across n o r t h e a s t e r n B r i t i s h Columbia and the Geology of the Northern E x t e n s i o n o f the F r a n k l i n Mountains, N.W.T." G.3*G. Summ.Rept., 1922, P t . B. " F r a n k l i n Mountains." B.G.S.A., V o l . 35, 1924. "Land Movements and Sedimentation." B.G.S.A., V o l . 4 3 , 1932. W i l l i a m s , M.Y. and Bocock, J.B. "The Peace R i v e r and Dominion Blocks - Geology." P.G.E. Lands Resources Survey. Report of Progress, V o l . 2, 1929. W i l l s , B. " S t r a t i g r a p h y and S t r u c t u r e , Lewis and L i v i n g s t o n e Ranges, Montana." B.G.S.A., V o l . 12, 1902. "Rocky Mountain S t r u c t u r e . " Jour, of Geol., V o l . 33 , No. 3 , 1925. "Geologic S t r u c t u r e s . " 1929. cibc <!iiincii' A T L A S 1 E I T I S E C O L U M B I A PLATE 89 ii 13+ IffllilllililUHiilf 1.4 1 1 E 1 1 4 r-^WU'iW,, Cm, A • ^ ^ T V J .... , . ,„:• "' feu-,,) ?•» / wL l4k £ '" AH \ \ ^ N ^ J J ' ^ _ _ _ > I x>, B) ""ft K • 5-j Pi '."•••""inX- Snt /VPS, Ji'iArThtltl ' - - • A N ' , ; ; -•-'tumtTMaxiafT ' ft'atiitrr)*' • • ••.J.f, m to 132 KXl'I.ANA'llON (IF o«()(;iiA.!'Hi(-,\i-i.:or,()i'i;iNi. MKTIIZS I T. FEET f ••• •••• I. I ' .iriri.q,/ (•'tux't-.V* •aw* I; JM*&w t t: x t./ip/fw-*"*" ^ &r>' .W'J|. *«' L„,nJP ,0 ntf\i<'f 7< X • .1: * TVs ^ q ^n--4 1, •.["rt"./n/'i-*'7' ' ( r: .ii.'r 2. / ^ ^ J T s d Irmri'\,t\\, ,/,• Moduli If" - „: • »^F" | v 'it.'; ,,J II.inII,.,- |»Vfy ••••'<(jr"'",il •i , •., i|- , N A N A I M C C • . ^ ^ > ' 1 J , | , . ^ M » V : ^ : - ' 4 / . . ^ ; ^ , ; Wl'nilii'ln" 3^ : -  K - t : : i !.:4r A , J - ^ r ^ O ^ V ^ * 1 * ii /..i/.iJ*. ,, • (?y,.,./#.iv/ - I / .' v.ii/ii«/fP i. I . , , iru„,.v ,,t *»ifc '#' ' i tefffif ll.uU.-^v, p^ _t |i»R*'*:i' ^ H^i^ZTiSrv^ii .X.i G 0 M, SraJc I : 2,500,000 English MilwH o it> so an *o K I ao T O so so KlJur.iom*n a m in B I I «i i.i in MM mi I I K I 1111 lju i:u> 1*1 I M I irv, Vvf,fi,vr/i..' .^ ^ |Q_H DMISH .,VI"*iV' • | " 1 11 1_ ; ,.»*u7l' • • i , ; r-w*?v^^ 123 lii A i M M l l ' ; : ! l i i M : i i ' i i i i i i i ^ THE to IN 8 U RGH CE0CPAPHICAL IN5TITUTE JOHN B4RTH010MIW « 50N. ITO BRITISH COLUMBIA The Shaded Area on Index Map shows the extent of this iPlate INDEX TO SECTION MAPS OF CANADA O N S C A L E O F t : 2 , 5 0 0 , 0 0 0 HON.SIR JAMES A LOUGHEED. MINISTER; CHARLES CAMSELL. DEPUTY MINISTER. GEOLOGICAL S U R V E Y W.H.COLLINS. DIRECTOR. Be I S H I U M I W i l l i l l d l l i l l O l l . S O l i d C I H ' l ••< I i ' J U M . l O L ' J LEGEND I. j V Paskapoo Tertiary I K8 E d m o n t o n and W a p i t i A t h a b a s c a R i v e r S e c t i o n River PeaceHiver K 7 . ,„ K6 Lower L a B I - h e P e l i c a n s a n d s t o n e K4 > Pelican M • K 3 <;,•„,„! R„| , ,ds K2 Clearwater I K l H e Smoky K i v e r Kd D u n v e ^ a n K c Fort S t J o h n Kb Peax-e R i v e r Ko Loon River 5 D2 J 'F.r.tl •—, M i d d l e Dev.. Devonian ^,«./ ,i„hdii-ul,<l) S i l u r i a n A3 Z < 00 r as Q. Late TYe C a m b r i a n A2 U m n i l c and Ciieiss A l Early P r e t.ajidn-ian (SchlWClf. sit)J**S, tunrstttrie's S y m b o l s Geological boundary t pcrs/fjtin • r. <fiittfa or exppr-oxunalrty lea.•<•••• I tfeolagiraj I x n i n d o r y C r e t a c e o u s I not subdivided.) Wo,oie C O Seneoal, Orography ami Chief Vrautikiamaj, JO.Fortin. Draught™,™ Publication No ISH.~. A ( . \ (.' K K I I'! I M V K K I - J A v i II NORT1 1 V VE STJEItN C A N A 1 ) A 11 'it} tit'ftyittfttlnv r/rw f t t i t i o r i at' Meirt'H'r ttv <:.i'tun.srll W.Matejibit. tll'JI. jr. .10 Stale, M i l e s J O O zoo a i m aoo 5 0 M I L E S T O I I N C H 1 ... 11.• r 1 

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