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UBC Theses and Dissertations

Geology of Yukon Territory with special reference to Alaska Johnston, J.R. 1934

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GEOLOGY OF YUKON TERRITORY, with special reference to Alaska.  by J.R. JOHNSTON  A T h e s i s submitted, f o r t h e Degree o f PIASTER OF APPLIED  SCIENCE  i n t h e Departmentof GEOLOGY  The U n i T e r s i t w - o f B r i t i s h C o l u m b i a April.  .  CONTENTS. Page  CHAPTER I ,  PHYSICAL GEOGRAPHY. P o s i t i o n and a r e a .............»..»«.. General r e l i e f features ». D r a i n a g e ......••.•«....•...«•••»•••»• F e a t u r e s due t o g l a c i a t i o n .«  1 1 12 16  GEOLOGY. CHAPTER I I , t h e PREG AMBRIAN. Yukon g r o u p Age o f t h e Yukon g r o u p .. . T i n d i r group Age o f t h e T i n d i r g r o u p  18 29 44 48  CHAPTER I I I , t h e PALEOZOIC. Cambrian s y s t e m O r d o v i c i a n system S i l u r i a n system D e v o n i a n s y s t e m ....»......«..»• Lower P a l e o z o i c i g n e o u s r o c k s ........ Carboniferous system  57 61 bo 75 83 86  CHAPTER I V , t h e MESOZOIC. T r i a s s i c system « J u r a s s i c system O l d e r v o l c a n i c s ...................... Granitic intrusives • Cretaceous system *•  104 108 115 117 119  CHAPTER V, t h e CENOZOIC. Tertiary  sediments  Quaternary system  125 133  CONTENTS ( c o n t i n u e d ) . Page CHAPTER V I , t h e CHRONOLOGICAL RECORD. Precambrian record Paleozoic record Mesozoic r e c o r d Tertiary record Q u a t e r n a r y r e c o r d .. .  *  137 140 * 147 133 1J?4  APPENDIX. BIBLIOGRAPHY  i  IITR03UCTIOH. The p u r p o s e o f t h i s p a p e r i s a summary o f the known geology,  o r more e x a c t l y , t h e s t r a t i g r a p h y o f Yukon T e r r i t o r y .  I n view o f the f a c t s t h a t t h e g e o l o g y  of the p o l i t i c a l  p r o v i n c e s o f Yukon and A l a s k a p r e s e n t s many p o i n t s i n common, t h a t many o f the p r o b l e m s o f t h e two p r o v i n c e s a r e i n t e r r e l a t e d , and t h a t c o n s i d e r a b l e work h a s b e e n done a l o n g t h e Y u k o n - A l a s k a b o u n d a r y , the w r i t e r f e e l s t h a t a g e n e r a l e o r r e l a t i o n o f A l a s k a n g e o l o g y w i t h t h a t o f Yukon i s j u s t i f i e d a n d , i n t h i s case, l e a d s to a b e t t e r understanding province.  o f t h e Yukon  He h a s , t h e r e f o r e , r e f e r r e d e x t e n s i v e l y t o t h e  l i t e r a t u r e on A l a s k a . The r o c k s o f Yukon T e r r i t o r y range i n age f r o m P r e cambrian t o R e c e n t .  P a r t o f the P r e c a m b r i a n  p e r i o d o f the P a l e o z o i c and M e s o z o i c ,  e r a , and e v e r y  and p a r t o f t h e Genozoic  i n t h e g e o l o g i c a l t i m e - s c a l e a r e r e p r e s e n t e d by rocks.  The P r e c a m b r i a n  sedimentary  rocks are d i s c u s s e d here i n c o n s i d e r -  a b l e d e t a i l j the r e a s o n f o r t h i s b e i n g t h a t most o f Yukon g e o l o g i c a l i n v e s t i g a t i o n t o date has c e n t e r e d on a r e a s u n d e r l a i n by t h e s e r o c k s .  The v a l u e o f c o r r e l a t i o n between A l a s k a  and Yukon i s soon a p p a r e n t the P r e c a m b r i a n  t o anyone s t u d y i n g t h e problems o f  r o c k s i n e i t h e r r e g i o n , f o r o u r knowledge o f  t h e i r sequence a n d t h e i r age s t a t u s depends on work done i n both r e g i o n s .  The Y u k o n - A l a s k a b o u n d a r y , t h r o u g h  the g r e a t e r  part of i t s l e n g t h , i s against the s t r i k e o f the rocks i n both Yukon and. A l a s k a .  The s e c t i o n a l o n g t h i s l i n e h a s been  examined by A l a s k a n a n d Yukon g e o l o g i s t s , and i t s p o s i t i o n and  -IId i r e c t i o n a r e such t h a t i t s e r v e s as a k e y to the g e o l o g y o f "both T e r r i t o r i e s .  Wherever p o s s i b l e the w r i t e r has r e f e r r e d t o  the known p a r t s o f t h i s s e c t i o n .  Sources o f i n f o r m a t i o n and acknowledgrnents. During  the l a s t t h r e e summers t h e w r i t e r has been  a c t i v e l y i n t e r e s t e d i n the problems o f Yukon g e o l o g y w h i l e s e r v i n g as an a s s i s t a n t on the G e o l o g i c a l S u r v e y .  He t h e r e -  f o r e has some f i r s t - h a n d i n f o r m a t i o n o f t h e f i e l d ,  particular-  l y of the i n t e r i o r r e g i o n , over a c o n s i d e r a b l e part o f which he has been.  I n t h i s connection, the w r i t e r wishes to  .acknowledge v a r i o u s c o m m u n i c a t i o n s and d i s c u s s i o n s w i t h Dr. H.S. Bos took o f t h e S u r v e y , w i t h whom he worked i n t h e f i e l d . . The  g r e a t e r part o f the i n f o r m a t i o n I n t h i s paper i s  from r e p o r t s by the Canada and U n i t e d S t a t e s G e o l o g i c a l S u r v e y s , o r f r o m p a p e r s by the members o f t h e s e journals of various s c i e n t i f i c s o c i e t i e s . Yukon f i e l d were G.M.  surveys  i n the  The p i o n e e r s i n t h e  Dawson and R.G. M c C o n n e l l , who c o n d u c t e d  l e n g t h y e x p l o r a t i o n s i n the r e g i o n i n 1887 and 1888. f o l l o w i n g y e a r s a number o f l e n g t h y and d i f f i c u l t  In  route  s u r v e y s were c o n d u c t e d by b o t h C a n a d i a n and A m e r i c a n g e o g r a p h e r s and g e o l o g i s t s , and o u r p r e s e n t  knowledge o f e x t e n s i v e  t r a c t s o f Yukon depends l a r g e l y on t h i s e a r l y work.  With the  d i s c o v e r y o f g o l d i n the K l o n d i k e i n 18?6, t h e n e c e s s i t y f o r geological information pertaining to t h i s region resulted i n o r g a n i z e d mapping w h i c h has been c a r r i e d on i n A l a s k a and Yukon s i n c e t h a t t i m e .  A t the p r e s e n t , about one q u a r t e r o f  -IllYukon T e r r i t o r y and one h a l f o f A l a s k a has been examined i n reconnaissance  surveys.  F i n a l l y t h e w r i t e r w i s h e s to acknowledge the a s s i s t a n c e and g u i d a n c e o f Dr. S . J . S c h o f i e l d , u n d e r whose d i r e c t i o n t h i s p a p e r was  written.  CHAPTER I . PHYSICAL GEOGRAPHY  6  -1GE1ERA1 PHYSICAL GEOGRAPHY OP YUKON WITH REFERENCE TO ALASKA P o s i t i o n and A r e a . 1 Yukon. T e r r i t o r y and A l a s k a  occupy t h e n o r t h w e s t e r n  p a r t o f the N o r t h A m e r i c a n c o n t i n e n t , t h a t p a r t e x t e n d i n g t o ward t h e c o n t i n e n t o f A s i a .  This general r e g i o n ( i n c l u d i n g the  A l e u t i a n I s l a n d s ) l i e s "between l a t i t u d e s -51° n o r t h and 7 2 ° o o n o r t h , and b e t w e e n l o n g i t u d e s 173 e a s t and 12j> w e s t . The r e g i o n i s bounded on t h e n o r t h by A r c t i c Ocean; on t h e west by A r c t i c Ocean, B e r i n g S t r a i t , and B e r i n g Sea;  on t h e s o u t h by  P a c i f i c O.cean, s o u t h e a s t e r n A l a s k a , and B r i t i s h C o l u m b i a ; and on the east by the N o r t h w e s t T e r r i t o r i e s . separated meridian.  Yukon T e r r i t o r y i s  f r o m t h e main p a r t o f A l a s k a by t h e 1 4 1 s t . The main mass o f A l a s k a o c c u p i e s  western  an a r e a o f about  500,000  square m i l e s , and Yule on o f o v e r 1 0 0 , 0 0 0 square m i l e s .  General  Relief The  Features. main t o p o g r a p h i c  s i m i l a r to those  f e a t u r e s o f A l a s k a and Yukon a r e  o f w e s t e r n Canada and U n i t e d S t a t e s .  No  p h y s i c a l boundary w h i c h c a n be d e f i n e d i n g e n e r a l terms between t h e two r e g i o n s ; t h e t h r e e major t o p o g r a p h i c  exists  divisions  c h a r a c t e r i s t i c o f t h e w e s t e r n C o r d i l l e r a o f Canada and U n i t e d S t a t e s a r e p e r s i s t e n t t o t h e n o r t h w e s t i n Yukon and A l a s k a . These t o p o g r a p h i c  d i v i s i o n s trend p a r a l l e l t o the P a c i f i c  l i n e , and c o n s i s t o f an i n t e r i o r r e g i o n o f moderate  coast  relief  'bounded on t h e south and w e s t , and on t h e n o r t h a n d e a s t , by I. The main o r p e n i n s u l a r p a r t o f A l a s k a , e x c l u s i v e o f t h e s o u t h e a s t e r n 'Panhandle', i s r e f e r r e d t o i n t h i s d i s c u s s i o n .  regions of high r e l i e f .  The o u t e r or n o r t h e a s t e r n  periphery  o f the Y u k o n - A l a s k a C o r d i l l e r a i s bounded on t h e n o r t h e a s t by a r e g i o n o f moderate to low r e l i e f .  The g e n e r a l r e l i e f o f Yukon  and A l a s k a i s shown i n F i g u r e s 1 and 2 .  F i g . 1.  B e l i e f features of Alaska (after  F i g . 2.  R e l i e f f e a t u r e s o f Yukon ( a f t e r K e e l e J .  The n o m e n c l a t u r e o f t h e n o r t h w e s t e r n p r o v i n c e s v a r i e s w i t h t h e usage o f d i f f e r e n t  Brooks).  Cordilleran  authorities,  -3d e p e n d i n g on the scope o f t h e i r d e s c r i p t i o n s ,  or the b a s i s o f  c l a s s i f i c a t i o n (topographic, s t r u c t u r a l , chronological,  etc.;.  As t h i s d i s c u s s i o n r e f e r s  writer  m a i n l y t o Yukon T e r r i t o r y  the  has adopted the n o m e n c l a t u r e o f t h e p h y s i o g r a p h i c p r o v i n c e s o f Yukon*, d e s c r i b e d and f i g u r e d  i n numerous p a p e r s by C D .  Cair-  nes ( F i g . 3 . ) .  F i g . 3»  P h y s i o g r a p h i c p r o v i n c e s o f Yukon.  The major d i v i s i o n s  of r e l i e f  include:  1 . A r c t i c S l o p e , M a c k e n z i e l o w l a n d s , and G r e a t 2. E o c k y M o u n t a i n 3.  Interior  4. C o a s t a l 1.  Plains.  System.  System. System.  A r c t i c S l o p e , M a c k e n z i e l o w l a n d s , and Great The d i v i s i o n s  Plains.  named i n t h i s h e a d i n g c o l l e c t i v e l y f o r m  $ The d i s t r i b u t i o n o f the t o p o g r a p h i c p r o v i n c e s o f Yukon and A l a s k a i s shown i n F i g . 4 ( i n p o c k e t ) .  a r e g i o n o f low and moderate r e l i e f w h i c h bounds the n o r t h w e s t e r n C o r d i l l e r a on t h e e a s t and n o r t h . e s s e n t i a l l y one o f p l a t e a u s and p l a i n s ,  This region i s Yukon T e r r i t o r y i n -  cludes o n l y a s m a l l part o f t h i s p r o v i n c e ; v a l l e y o f P e e l r i v e r and a l o n g t h e A r c t i c The sell,  1  i t a p p e a r s i n the coast.  "basin o f P e e l r i v e r has been d e s c r i b e d  b y Cam-  The upper p a r t i s a p l a t e a u , the P e e l p l a t e a u , w h i c h  occupies  a g r e a t bay i n t h e e a s t e r n mountains o f t h e C o r d i l l e r a o 2 a t l a t i t u d e 66 n o r t h . A c c o r d i n g t o C a m s e l l : "On t h e n o r t h s i d e t h e P e e l p l a t e a u forms an a b r u p t escarpment o v e r l o o k i n g the l o w l a n d ( M a c k e n z i e Lowland) and r i s e s g r a d u a l l y southward u n t i l i t s t a n d s about 1,500 f e e t above the s e a . I t s surface i s a p p a r e n t l y f l a t but i s i n r e a l i t y made up o f s e v e r a l l o n g u n d u l a t i o n s h a v i n g a n o r t h and a s o u t h t r e n d . P e e l r i v e r c u t s a v a l l e y i n t h e p l a t e a u , r a n g i n g f r o m 700 t o 1000 f e e t deep.... The e a s t e r n l i m i t o f t h e b r o k e n h i l l y c o u n t r y o f t h e p l a t e a u l i e s a t Snake r i v e r , beyond w h i c h the p l a t e a u s t r e t c h e s e a s t ward w i t h an u n b r o k e n s k y - l i n e f o r an unknown d i s t a n c e The p l a t e a u g r a d u a l l y n a r r o w s i n w i d t h n o r t h w a r d as t h e M a c k e n z i e a p p r o a c h e s the m o u n t a i n s u n t i l i t e v e n t u a l l y merges i n t o the m o u n t a i n s and d i s a p p e a r s near R a t r i v e r a t the head of the (Mackenzie) d e l t a , " 5  The  A r c t i c S l o p e r e g i o n o f Yukon i s d e s c r i b e d b y  3  O'Neill  as a p l a t e a u about 13 m i l e s w i d e w h i c h e x t e n d s f r o m  the A r c t i c Ocean s o u t h  to t h e A r c t i c m o u n t a i n s .  p l a i n r a r e l y more t h a n h a l f a m i l e wide o c c u r s the c o a s t .  A coastal i n places  along  The p l a t e a u , where n o t b o r d e r e d b y a c o a s t a l p l a i n ,  r i s e s from the beach i n c l i f f s  seldom l o w e r t h a n 20 t o 30 f e e t  h i g h and e x t e n d s s o u t h w i t h a g r a d u a l upward s l o p e  t o an e l e -  v a t i o n o f 400 f e e t a t t h e n o r t h f r o n t o f t h e m o u n t a i n s .  This  plateau i s e v i d e n t l y q u i t e s i m i l a r to the Peel plateau; i t 1. C a m s e l l , C - C.G.3., " P e e l R i v e r and T r i b u t a r i e s ' " , E p t . l 9 0 6 . 2. " -C.G.S., Mem. 108, p.19. 3. O ' N e i l l , J . J . - R p t . o f 1913-18, C a n . A r c t i c Exped., Y o l . X I , p.10a, 19 24.  -3-  e x t e n d s e a s t t o t h e M a c k e n z i e r i v e r and d r o p s to the low l e v e l o f the d e l t a . West o f t h e A l a s k a - Y u k o n "boundary the A r c t i c  Slope  r e g i o n w i d e n s t o a n immense.tundra r e g i o n a l o n g t h e n o r t h e r n part of Alaska.  The two d i v i s i o n s , p l a t e a u and c o a s t a l p l a i n ,  o From the 15 m i l e b e l t n e a r l o n g i t u d e 141 W. o the p l a t e a u w i d e n s to n e a r l y 100 m i l e s a t l o n g i t u d e 1.50 W. and m a i n t a i n s a w i d t h o f t h i s o r d e r t o t h e A r c t i c o c e a n on t h e w e s t . are m a i n t a i n e d .  o The  c o a s t a l p l a i n r e m a i n s narrow west t o l o n g i t u d e 1.50 , but  widens t o n e a r l y 80 m i l e s i n t h e r e g i o n o f P o i n t Barrow ( 1 5 6 ° W.), and g r a d u a l l y n a r r o w s a g a i n  to l o n g i t u d e 162  W.  The 1  ' A r c t i c P l a t e a u s ' r e g i o n i s d e s c r i b e d by S m i t h and M e r t i e  as  c o n s i s t i n g dominantly of Mesozoic rocks o f r e l a t i v e l y low resistance to erosion.  These u p l a n d s s l o p e f r o m a n e l e v a t i o n to 400 t o 600 f e e t on t h e  o f 3,000 t o 3,500 f e e t on t h e south north.  D i f f e r e n t p a r t s o f t h i s s u r f a c e were formed a t  d i f f e r e n t times  by d i f f e r e n t p r o c e s s e s ,  so t h a t t h e ' p l a t e a u '  i s r e a l l y a group o f p l a t e a u s and u p l a n d  surfaces.  C o a s t a l ' p l a i n , d e s c r i b e d by the same a u t h o r s ,  The ' A r c t i c  i s a featureless  s u r f a c e w i t h a v e r y g e n t l e s l o p e to t i d e a t the n o r t h . everywhere c o v e r e d organized  drainage,  by u n c o n s o l i d a t e d and r e p r e s e n t s  m a r i n e d e p o s i t s , has d i s -  an u p l i f t e d p a r t o f t h e s e a  f l o o r which i s only p a r t i a l l y modified 2, R o c k y M o u n t a i n System. The  It i s  by e r o s i o n .  c o n t i n u i t y o f the R o c k y M o u n t a i n s o f B r i t i s h  C o l u m b i a and ' A l b e r t a i s i n t e r r u p t e d t o the n o r t h w e s t n e a r L i a r d 1. Smith,P.S. & M e r t i e , J.B., , j r . - U . S . G . S . B u l l . 8 1 5 , pp.41-51, 1930.  ~6-  r i v e r , where the m o u n t a i n s appear to d i e away; the  eastern  f o o t h i l l s however c o n t i n u e a c r o s s the L i a r d and merge w i t h s o u t h e r n s p u r s o f the M a c k e n z i e m o u n t a i n s .  The  nature of t h i s  t'break' i s not known. The M a c k e n z i e m o u n t a i n s r i s e n o r t h o f L i a r d  river.  At i t s s o u t h e r n e x t r e m i t y the e a s t e r n f r o n t o f t h e range i s stepped  f a r t o the e a s t o f the e a s t e r n "border o f the R o c k y  mountains.  The  e a s t e r n f r o n t o f the M a c k e n z i e m o u n t a i n s t r e n d s  i n a g r e a t a r c f r o m L i a r d r i v e r , n o r t h and n o r t h w e s t  along  the  course o f M a c k e n z i e r i v e r and west a c r o s s the h e a d w a t e r s o f Peel r i v e r .  The w e s t e r n  border trends northwest  heads o f F r a n c e s , P e l l y , and  Stewart  across  the  r i v e r s , and west a c r o s s  the heads o f B e a v e r , McQuesten, and K l o n d i k e r i v e r s t o the Y u k o n - A l a s k a boundary.  The M a c k e n z i e m o u n t a i n s , t h e r e f o r e ,  f o r m a g r e a t h i g h l a n d r i s i n g near l a t i t u d e 60° IT., l o n g i t u d e y 0  0  124  W.  and  extending northwest  t o l a t i t u d e bj?  on the A l a s k a  s i d e o f the 1 4 l s t . m e r i d i a n , where the mountains appear to merge w i t h the i n t e r i o r p l a t e a u c o u n t r y to the w e s t .  Little  i s known o f t h i s m o u n t a i n t r a c t , a p a r t o f w h i c h l i e s i n Yukon Territory. miles.  The h i g h l a n d v a r i e s i n w i d t h t o a maximum o f  200  On the s o u t h t h e m o u n t a i n s r i s e r a p i d l y to 6000 f e e t ,  r e a c h e l e v a t i o n s o f 8000 f e e t above the s e a near G r a v e l r i v e r , but g r a d u a l l y drop to j>000 f e e t and sion into Alaska.  l e s s i n the w e s t e r n  exten-  The w e s t e r n e x t e n s i o n a c r o s s Yukon and  A l a s k a i s known as the O g i l v i e m o u n t a i n s .  A c c o r d i n g to K e e l e  the M a c k e n z i e m o u n t a i n s "appear to c o n s i s t o f two r a n g e s , older western  into 1  r a n g e , a g a i n s t the e a s t e r n edges o f w h i c h a  an  -7 newer range has "been p i l e d * " N o r t h o f the M a c k e n z i e mountains and a c r o s s t h e P e e l p l a t e a u the e a s t e r n h i g h l a n d o f the C o r d i l l e r a  i s represented  bv the R i c h a r d s o n m o u n t a i n s w h i c h t r e n d n o r t h a l o n g t h e west s i d e o f P e e l r i v e r t o n e a r the M a c k e n z i e d e l t a where t h e y s w i n g a b r u p t l y w e s t , c r o s s Yukon, and e n t e r A l a s k a as -part o f the g r e a t e r group o f A r c t i c mountains range  (now known as t h e B r o o k s  ;. The B r o o k s r a n g e , under the o l d e r name ' A r c t i c Moun2  t a i n s y s t e m ' , i s d e s c r i b e d by B r o o k s  as  follows:  , "A new name, A r c t i c M o u n t a i n s y s t e m , i s p r o p o s e d f o r t h e east and west t r e n d i n g m o u n t a i n s y s t e m o f n o r t h e r n A l a s k a f o r m e r l y r e g a r d e d as p a r t o f t h e R o c k y M o u n t a i n s y s t e m . Recent i n v e s t i g a t i o n s by C a n a d i a n and A m e r i c a n g e o l o g i s t s have shown that t h i s i s a d i s t i n c t system from the Rocky Mountains, a l t h o u g h t h e y are c o n n e c t e d by the f l a t - t o p p e d R i c h a r d s o n Mountains, forming the Mackenzie-Porcupine d i v i d e . The A r c t i c M o u n t a i n s y s t e m s t r e t c h e s westward f r o m t h e i n t e r n a t i o n a l boundary t o t h e A r c t i c Ocean n o r t h o f K o t z e b u e Sound. I t i s not everywhere s h a r p l y d i f f e r e n t i a t e d f r o m t h e p l a t e a u r e g i o n to the s o u t h , f o r i n many p l a c e s the d i s s e c t e d p l a t e a u remnants merge w i t h the f o o t h i l l s o f the r a n g e s . . . . On the n o r t h the m o u n t a i n s , so f a r as known, everywhere f a l l o f f a b r u p t l y t o the A r c t i c s l o p e . T h i s s c a r p a f f o r d s a d e f i n i t e boundary l i n e between the two p r o v i n c e s . The s y s t e m i s made up t h r o u g h o u t i t s e x t e n t o f two o r more p a r a l l e l r a n g e s and i n c l u d e s some broad l o w l a n d s . . . . The A r c t i c M o u n t a i n s y s t e m i s c o n t i n u e d e a s t o f the boundary by some m o u n t a i n s o f l e s s e r latitude. These end i n a s c a r p a t the M a c k e n z i e d e l t a , e a s t o f w h i c h t h e y have not b e e n r e c o g n i z e d . " Whether o r n o t t h e B r o o k s Range c a n be c o r r e l a t e d w i t h the R o c k y mountains  is still  open t o q u e s t i o n .  According  3  to M e r t i e :  "the B r o o k s Range...may r e p r e s e n t e i t h e r  the Rocky-  M o u n t a i n Range o f t h e C o r d i l l e r a , b e n d i n g n o r t h w e s t w a r d i n t o TV Smith,P.S. & M e r t i e , J.B., j r . - U.sTG.S. B u l l . 8 1 5 , p.29, 1950. 2. Brooks,A.H.- Wash.Acad.Sci., J o u r . , V o l . 6 , pp. 252-253. 3 . M e r t i e , J . B . , j r •- U.3.G.S. B u l l . 8 l 6 ,  p.6,  1930.  1916.  _8~ A l a s k a , or a s e p a r a t e m o u n t a i n range o f A r c t i c  r a t h e r than  of  Pacific affinity." 3.  Interior  System.  The  i n t e r i o r r e g i o n o f the n o r t h w e s t i s a  p r o v i n c e o f p l a t e a u s and mountains.  l o w l a n d s w i t h o c c a s i o n a l g r o u p s of  In general t h i s province  c o r r e s p o n d s to and  e x t e n s i v e w i t h the i n t e r i o r r e g i o n o f the C o r d i l l e r a B r i t i s h Columbia.  topographic  i s co-  of  I n Yukon t h e most p r o m i n e n t f e a t u r e i s a n  e x t e n s i v e r o l l i n g u p l a n d w h i c h i s d e e p l y d i s s e c t e d by s t r e a m valleys.  'The  upland  i s known as the Yukon p l a t e a u .  The  Yukon  1  p l a t e a u has been d e s c r i b e d by C a i r n e s  as h a v i n g  "the  contour  o f a huge f l a r i n g t r o u g h whose median l i n e i s i n a g e n e r a l marked by the course Northern  of Yukon r i v e r f r o m i t s h e a d w a t e r s i n  B r i t i s h C o l u m b i a to B e r i n g Sea."  The p l a t e a u  s l o p e s , t h e r e f o r e , b o t h from the b o r d e r i n g h i g h l a n d s the Yukon r i v e r , and lower b a s i n .  way,  f r o m the s o u r c e s  surface  towards  of the Yukon towards i t s  Near the B r i t i s h Columbia - Yukon boundary the  p l a t e a u has an e l e v a t i o n o f 6000 f e e t above the s e a .  To  the  n o r t h w e s t the e l e v a t i o n o f the p l a t e a u s u r f a c e d e c r e a s e s t o 4000 or 4500 f e e t at the Y u k o n - A l a s k a boundary, and, a c c o r d i n g 2  to Brooks , i t s t a n d s a t an e l e v a t i o n of l e s s t h a n 2000 f e e t 0 o near the lower r a m p a r t s o f the Yukon (150 W., 66 N.). I n the i n t e r i o r r e g i o n o f Yukon the p r o p o r t i o n o f lowland floors  to upland of wide and  ( p l a t e a u ) i s low; deep v a l l e y s ,  the l o w l a n d s  comprising  the  the e l e v a t i o n s o f w h i c h v a r y  I T C a i r n e s , D . D . - C.G.S. Guide Book 10, 2. Brooks,A.H.- U.S.G.S. P r o f . P a p . 45,  p.54. p.57,  1906.  -9-  but decrease  i n the d i r e c t i o n o f d r a i n a g e .  A c r o s s the  Alaska  boundary the p r o p o r t i o n o f l o w l a n d to u p l a n d becomes p r o g r e s s 1  i v e l y g r e a t e r to the west and s o u t h w e s t .  Quoting  Brooks:  "As the Yukon P l a t e a u approaches B e r i n g Sea i t gradua l l y l o s e s i t s d i s t i n c t i v e f e a t u r e s ; the v a l l e y s b r o a d e n , t h e i n t e r s t r e a m a r e a s grow s m a l l e r and l o w e r , and, f i n a l l y , 100 m i l e s o r more from t i d e w a t e r , the u p l a n d s end and the v a l l e y f l o o r s merge w i t h the c o a s t a l p l a i n w h i c h s k i r t s the e a s t e r n shore o f B e r i n g Sea. T h i s c o a s t a l p l a i n , w h i c h i s by f a r the l a r g e s t o f t h i s r e g i o n , i s o f low r e l i e f and about 25,000 square m i l e s i n e x t e n t . I t embraces the l o w e r Kuskokwim and Yukon v a l l e y s as f a r n o r t h as N o r t o n Sound, and f o r the most p a r t i s i n the d e l t a s o f t h e s e two g r e a t r i v e r s . . . . . . t h e r e a r e a l s o l a r g e l o w l a n d t r a c t s i n the i n l a n d p a r t s o f the p r o v i n c e , . .,, The l a r g e s t o f t h e s e i s the s o - c a l l e d Yukon P l a t s , a d e p r e s s e d a r e a a t t h e g r e a t bend o f the m i d d l e Yukon , A n o t h e r d e p r e s s e d . a r e a , s i m i l a r to the Yukon F l a t s , l i e s between l a . t i t u d e 63° and 64° i n the Kuskokwim d r a i n a g e b a s i n . " The  Yukon p l a t e a u i s a g e n e r a l p h y s i o g r a p h i c f e a t u r e ,  b e l i e v e d by many i n v e s t i g a t o r s to r e p r e s e n t an u p l i f t e d penep l a i n ; o t h e r s contend  t h a t a mature but not o l d t o p o g r a p h y had  been carved i n the r e g i o n o f the p l a t e a u p r i o r to p o s t - P l e i s t o cene u p l i f t .  Many of the p l a t e a u f e a t u r e s are a t t r i b u t e d  p r o c e s s e s p e c u l i a r t o s u b - A r c t i c c l i m a t e , such as n i d a t i o n , and  solifluxion,  altiplanation.  B e s i d e s the p l a t e a u and p r o v i n c e comprises  l o w l a n d f e a t u r e the  interior  a number o f h i g h e r t r a c t s , some o f w h i c h  c o u l d a l m o s t be c l a s s e d as m o u n t a i n r a n g e s . i n o r d e r f r o m t h o s e i n the s o u t h e a s t (1)  to  These a r e  to those i n the  listed  northwest.  Northwest e x t e n s i o n o f C a s s i a r m o u n t a i n s o f B r i t i s h Columbia,  (2)  P e l l y mountains, south of P e l l y  (3)  H i g h group west o f Q u i e t l a k e .  river.  ( 4 ) Glenl;/on m o u n t a i n s , s o u t h o f P e l l y and e a s t o f l e w e s r i v e r .  -10(5)  Dawson r a n g e , west o f Lewes and s o u t h o f Yukon r i v e r .  (6)  H i g h group between A i s h i h i k l a k e and M l s l i n g  (7)  M a c m i l l a n , M c A r t h u r , and K a l z a s m o u n t a i n s , n o r t h o f P e l l y  river.  and s o u t h o f S t e w a r t r i v e r . ( 8 ) K e e l e m o u n t a i n s , i n t e r n a t i o n a l boundary s o u t h o f P o r c u p i n e river. W i t h t h e e x c e p t i o n o f t h e K e e l e mountains t h e s e g r o u p s r e a c h an average maximum e l e v a t i o n o f 6000 t o 7000 f e e t . Whether a l l ,  or some o f t h e i n t e r i o r m o u n t a i n groups b e l o n g t o  t h e Rocky M o u n t a i n o r C o a s t a l p h y s i o g r a p h i c p r o v i n c e s i s a t present.hypothetical. all  The C a s s i a r , P e l l y , and G l e n l y o n g r o u p s ,  embody c o n s i d e r a b l e a r e a s o f g r a n i t i c r o c k s and i n t h i s  r e s p e c t r e s e m b l e t h e C o a s t range o f B r i t i s h C o l u m b i a .  Collec-  t i v e l y , t h e y f o r m a m o u n t a i n t r a c t w h i c h l i e s i n 'en e c h e l o n ' arrangement w i t h the Coast r a n g e .  These m o u n t a i n s , i n Yukon,  appear t o be s e p a r a t e d f r o m t h e Rocky m o u n t a i n s by a b e l t o f p l a t e a u c o u n t r y w h i c h i s d r a i n e d b y F r a n c e s and L i a r d Little  rivers.  i s known o f M a c m i l l a n , K a l z a s , and M c A r t h u r g r o u p s .  T o g e t h e r , t h e y f o r m a mountainous t r a c t between S t e w a r t and M a c m i l l a n r i v e r s and a r e n o t s h a r p l y d i f f e r e n t i a t e d from the M a c k e n z i e mountains t o t h e e a s t .  The h i g h e r p o i n t s o f the  Dawson range c o n s i s t o f r o o f pendants o f v o l c a n i c r o c k ded by a mass o f g r a n i t i c r o c k , s u g g e s t i n g t h a t t h e i r e l e v a t i o n i s due p a r t l y t o d i f f e r e n t i a l e r o s i o n .  intrusuperior  The K e e l e  mountains l i e s o u t h o f P o r c u p i n e r i v e r and n o r t h o f t h e O g i l v i e mountains.  They a r e b e l i e v e d t o have the same p h y s i o -  g r a p h i c h i s t o r y as t h e Yukon p l a t e a u , but s t a n d h i g h e r because of t h e i r g r e a t e r r e s i s t a n c e to e r o s i o n .  -11Sirailar mountain groups occur i n the i n t e r i o r plateau province of Alaska.  These are generally lower than those of  Yukon T e r r i t o r y , except along borders of the c e n t r a l region where they occur as f o o t h i l l s to the Brooks and Alaska 4.  ranges.  Coastal System. The Coastal system i s represented i n Yukon by a  northwestern extension of the Coast range of B r i t i s h Columbia, part of the St. E l i a s range, and the southeastern end of the Hutzotin mountains of Alaska.  This provinoe i s known i n  B r i t i s h Columbia as the 'Eastern Belt *, and i n Alaska as the ' P a c i f i c Mountain System'. The Coast range i n Yukon consists of a complex of peaks, l a r g e l y of g r a n i t i c rook, which reach an e l e v a t i o n of about 7000 feet at the B r i t i s h Columbia - Yukon boundary, but gradually drop o f f to the northwest.  Hear Kluane lake the  summits merge with the upland surface of the Yukon plateau. The St. E l i a s range l i e s to the west of the Coast range, being separated from the l a t t e r by a depressed  area  which probably belongs l a r g e l y to the Yukon plateau province. The range r i s e s abruptly from the plateau i n a steep escarpment to high snow f i e l d s .  Peaks i n the centre of the range r i s e  above the snow and i c e and reach elevations of 1J?»000 feet or more above the sea. The Nutzotin mountains constitute the  innermost  member of the Coastal system i n the v i c i n i t y of the 141st. meridian.  They l i e north of the S t  %  E l i a s range, and r i s i n g i n  Yukon T e r r i t o r y trend northwest into Alaska.  The higher  summits r i s e to elevations of 6 , 5 0 0 and. 7,200 feet above the sea. Both the St. E l i a s and Nutzotin mountains are. "bordered on the northeast by extensive lowland as well as upland (plateau) areas.  As the structure along the contact has not  been worked out, the r e l a t i o n of the mountains to the i n t e r i o r features i s not known.  Cairnes  considered that the Nutzotin  mountains merged with the Yukon plateau at the beginning of the present topographic c y c l e , and that the apparent  abrupt con-  tact i s due to stream and i c e erosion. The St. E l i a s and Nutzotin mountains belong to the group o f high ranges which trends i n a great are from the i n t e r n a t i o n a l boundary across southern Alaska to Cook I n l e t , where a break occurs; the imaginary c e n t r a l axis appearing again i n the A l e u t i a n Islands.  A number of w e l l defined  ranges appear i n t h i s group, i n c l u d i n g the Chugach, Wrangell, Kenai, Talkeetna, St. E l i a s , A l e u t i a n and Alaska ranges. these the Alaska range i s the greatest.  Of  I t includes the  Hutzotin mountains and extends i n an unbroken chain from the i n t e r n a t i o n a l boundary 6.50 miles to near lower Cook i n l e t (see F i g . 4.)•  The Alaska range reaches a maximum e l e v a t i o n o f  20,300 feet at Mount McKinley near the centre o f the arc.  Drainage. The drainage o f Yukon T e r r i t o r y can be divided into three main parts: 1. Cairnes,D.C.-  C.CJ.S. Mem.50, p.43. 1915*  "  ~*  ( 1 ) Drainage (2)  to P a c i f i c Ocean.  Drainage to A r c t i c Ocean.  (3) Drainage to Bering Sea. ( 1 ) Drainage  to P a c i f i c Ocean.  A small part of Yukon T e r r i t o r y , the extreme south* west, i s drained by Alsek r i v e r , the t r i b u t a r i e s of which r i s e i n the Yukon Plateau region and j o i n to flow through the St. E l i a s mountains.  low d i v i d e s e x i s t between the Alsek and Yukon  drainages; i n some cases these are through v a l l e y s suggesting that the Alsek once extended to much more distant sources.  The  fact that i t has maintained i t s course across the St. E l i a s mountains shows that the Alsek i s an antecedent the P a c i f i c drainage of Yukon i s by way Two Ocean.  important  stream. A l l  of t h i s r i v e r .  streams drain from Alaska to P a c i f i c  These are the Susitna and Copper r i v e r s which have  t h e i r catchment basins e n t i r e l y w i t h i n the coastal zone of mountains.  The Copper r i v e r drains the Copper River plateau, a  depressed area l y i n g between the Alaska range and the Talkeet° na, Wrangell, and Chugach mountains. stands at  2000  to  J000  This b a s i n - l i k e feature  feet above the sea.  At i t s lower end  the Copper r i v e r follows a rather c o n s t r i c t e d course the Chugach mountains.  through  The Susitna drains part of the south  slope of the Alaska range and part of the Copper River plateau. It empties into Cook I n l e t . (2)  Bra&n&ge to A r c t i c Ocean. With the exception of the small A r c t i c Slope region,  the drainage of Yukon to the A r c t i c i s by way  of Mackenzie  -14river.  The main s t r e a m of the A r c t i c  slope i s F i r t h  river,  w h i c h r i s e s w e l l w i t h i n the R i c h a r d s o n mountains n e a r the 1 4 1 s t . m e r i d i a n and r u n s n o r t h t o the A r c t i c . tributaries, mountains delta.  t a k e s t h e r u n - o f f from the n o r t h f a c e o f O g i l v i e  and d r a i n s t h r o u g h P e e l p l a t e a u t o t h e M a c k e n z i e  A c o n s i d e r a b l e p o r t i o n o f s o u t h e r n Yukon i s d r a i n e d by-  tributaries  of Liard  Rocky mountains drainage  Peel r i v e r , with i t s  r i v e r w h i c h j o i n t o f l o w e a s t t h r o u g h the  to Mackenzie r i v e r .  The g r e a t e r p a r t o f t h i s  i n Yukon i s t h a t o f F r a n c e s and upper L i a r d  rivers,  w h i c h t o g e t h e r occupy a h i g h p l a t e a u r e g i o n on the west s i d e o f the M a c k e n z i e  mountains.  I n A l a s k a the e a s t h a l f o f the n o r t h s l o p e o f B r o o k s range i s d r a i n e d by n o r t h w a r d f l o w i n g s t r e a m s s u c h a s Canning and S a d l e r o c h i t r i v e r s .  The w e s t e r n p a r t o f t h e A r c t i c  drain-  age o f t h e range i s dominated by C o l v i l l e r i v e r , w h i c h f l o w s e a s t a l o n g t h e n o r t h f r o n t o f the range f o r about s i x d e g r e e s o f l o n g i t u d e and t h e n t u r n s n o r t h a c r o s s t h e p l a t e a u and coastal plain  t o the A r c t i c .  range i s d r a i n e d by Hoatak  Much o f the w e s t e r n end o f B r o o k s  r i v e r , w h i c h r u n s west t h r o u g h t h e  c e n t r e o f t h e range and e m p t i e s i n t o (3) Drainage to Bering  K o t z e b u e Sound.  Sea.  W i t h t h e e x c e p t i o n o f the b a s i n o f Kuskokwim r i v e r , Seward P e n i n s u l a , and the upper b a s i n s o f L i a r d  and A l s e k  r i v e r s , a l l o f the i n t e r i o r r e g i o n o f Yukon and A l a s k a i s d r a i n e d by Yukon r i v e r and i t s t r i b u t a r i e s .  The main stream  t r e n d s n o r t h w e s t t h r o u g h the p l a t e a u p r o v i n c e o f Yukon T e r r i t o r y , and a f t e r  c r o s s i n g the i n t e r n a t i o n a l boundary  joins  the  -15-  Porcupine  r i v e r at the A r c t i c  f o l l o w s the southwest course and  The Yukon r i v e r  Upper Yukon v a l l e y ;  valley  then  o f t h e l a t t e r f o r about 300  a f t e r s e v e r a l g r e a t bends r e a c h e s B e r i n g Sea.  recognised four subprovinces 1.  Circle.  i n t h e Yukon  miles  Brooks"*  -  has  valley;  1 to 3 miles wide, with w a l l s  r i s i n g t o the s u r f a c e o f t h e Yukon p l a t e a u .  This part o f the  Yukon e x t e n d s from t h e mouth o f P e l l y r i v e r to t h e P o r c u p i n e . 2 . Yukon F l a t s ; f l o w s through  f o r 200 m i l e s below P o r c u p i n e  r i v e r t h e Yukon  a g r e a t l o w l a n d v a r y i n g f r o m 40 t o 100 m i l e s i n  width. 3 . Rampart r e g i o n ; a l o n g t h e r i v e r t h e f l a t s end a b r u p t l y a t a s c a r p w h i c h forms p a r t o f t h e p l a t e a u . about 2000 f e e t above the s e a .  This upland stands at  F o r o v e r 100 m i l e s t h e Yukon  f l o w s s o u t h w e s t i n a v a l l e y -§- t o 3 m i l e s w i d e , t h e w a l l s o f w h i c h r i s e r a m p a r t - l i k e f r o m the w a t e r o r from a narrow terrace.  Brooks c o n s i d e r e d t h a t t h e windings  suggest i n c i s e d  o f the stream  meanders.  4. Lower Yukon; a t t h e mouth o f Tanana r i v e r the Yukon a g a i n e n t e r s a l o w l a n d , w h i c h a l o n g the main s t r e a m i s 15 t o 20 m i l e s w i d e , b u t e x t e n d s up t h e Tanana 200 m i l e s w i t h a w i d t h o f 20 t o 100 m i l e s . valley  From t h e Tanana t o the d e l t a t h e w i d t h o f Yukon  i s never l e s s  than 2 o r 3 m i l e s .  In Yukon T e r r i t o r y  the t r i b u t a r i e s  o f t h e Yukon r i s e  i n t h e h i g h l a n d s b o r d e r i n g the p l a t e a u r e g i o n and t o g e t h e r form a r a t h e r w e l l - d e f i n e d upper b a s i n .  The T e s l i n  and Lewes  r i v e r s r i s e i n t h e s o u t h e r n i n t e r i o r and Coast r a n g e ;  their  h e a d w a t e r s f o r m the most remote s o u r c e s o f t h e Yukon.  The  1. Brooks,A.H.- O p . c i t . , p p . 5 4 - 9 2 .  "  ~~  P e l l y and Stewart r i v e r s r i s e i n the Mackenzie mountains, the White r i v e r ' i n the. g l a c i e r s of the St . E l l a s mountains.  A  number of wide and deep v a l l e y s connect these streams i n the plateau region, and i t i s quite evident that there have "been extensive drainage changes i n T e r t i a r y and Quaternary time. The Porcupine r i v e r r i s e s on the northern slope of the O g i l v i e mountains near the source of Peel r i v e r .  It then  flows northeast, and near the Richardson mountains, where i t i s joined by B e l l r i v e r , i t swings to the west and southwest. Above the Yukon-Alaska boundary the Porcupine v a l l e y i s wide and cut to a depth of 1000 feet or more i n the plateau.  Near  the boundary the v a l l e y i s c o n s t r i c t e d and canyon-like f o r 50 miles to the Yukon F l a t s . The l a r g e r streams o f the Yukon are navigable through a greater part of t h e i r length, a feature which has allowed t r a v e l i n an otherwise p r a c t i o a l l y i n a c c e s s i b l e country.  R e l i e f features due t o g l a o i a t i o n . Two types of topography have developed i n Yukon and Alaska as the r e s u l t of g l a o i a t i o n .  One of these i s the topo-  graphy l e f t by the advance and retreat of the Pleistocene i c e sheets.  The well known features t y p i c a l of a g l a c i a t e d region  are c h a r a c t e r i s t i c of about two-thirds of Yukon T e r r i t o r y . The northwestern part of Yukon and much of the i n t e r i o r and northern part of Alaska escaped g l a o i a t i o n and have a topography developed from atmospheric and stream erosion; a topography equally unique as, but widely d i f f e r e n t from, that of the g l a c i a t e d region.  -17The cene  limits  o f t h e maximum i c e a d v a n c e  a r e shown i n F i g u r e  glaciers  4.  At  the present  i n Yukon l i e i n the S t . E l i a s T h e r e a r e many m i n o r  o f the  t i m e t h e only-  mountains.  f e a t u r e s o f topography, which,  although probably resulting  f r o m c o n d i t i o n s which were  spread  c a n n o t be  in their  treatment not  influences,  such as t h i s .  discussed  Such a r e r i v e r  be u n d e r s t o o d p r o p e r l y u n t i l  t o p o g r a p h i c mapping  has been  Pleisto-  general  t e r r a c e s , which  much more a n d  done.  in a  wide-  detailed  will  CHAPTER I I .  THE PRECAHBRIAN•  -18PRECAMBRIAN  The P r e c a r a h r i a n r o c k s o f Yukon and A l a s k a a r e d i v i s i b l e i n t o two c l a s s e s : (1)  S c h i s t o s e - Yukon Group.  (2) N o n - s c h i s t o s e  - T i n d i r Group.  Of t h e s e the Yukon group a p p e a r s t o be the o l d e r and w i l l be d i s c u s s e d f i r s t .  Yukon Group. The Yukon g r o u p , w h i c h o c c u p i e s a l a r g e p a r t o f the i n t e r i o r r e g i o n o f Yukon and A l a s k a , c o n s i s t s o f a v a r i e t y o f s c h i s t o s e and g n e i s s i c . r o c k s the l e a d i n g t y p e s o f w h i c h a r e q u a r t z i t e s , quartzose mica s c h i s t s , c r y s t a l l i n e hornblende  limestones,  s c h i s t s , c h l o r i t e and s e r i c i t e s c h i s t s , and  granitic gneisses.  I n g e n e r a l t h e s e r o c k s a r e h i g h l y meta-  morphosed, e x h i b i t c o n t o r t i o n a l f o l d i n g , and show w e l l developed  cleavages.  I n p l a c e s t h e r e i s complete  l i z a t i o n ; i n o t h e r s a l t e r a t i o n has not c o m p l e t e l y the o r i g i n a l f a b r i c and s e d i m e n t a r y , t y p e s can be r e c o g n i z e d .  recrystaldestroyed  e x t r u s i v e , and i n t r u s i v e  The g e n e r a l c h a r a c t e r o f t h e s e  rocks  i s u n i f o r m o v e r g r e a t d i s t a n c e s , e s p e c i a l l y a l o n g the s t r i k e w h i c h i s r o u g h l y p a r a l l e l t o t h e a r c u a t e t r e n d o f the C o r d i l l e r a i n Yukon-Alaska.  No f o s s i l s have been found i n t h e  r o c k s o f the Yukon g r o u p . The g e n e r a l d i s t r i b u t i o n o f the Yukon group i n Yukon and A l a s k a i s shown i n the maps w h i c h i l l u s t r a t e t h e l o c a l i t i e s m e n t i o n e d i n the d i s c u s s i o n o f the c o r r e l a t i o n o f t h e s e  -19roclcs.  The group i s f a i r l y w e l l c o n f i n e d t o the i n t e r i o r  r e g i o n o f the C o r d i l l e r a and e s p e c i a l l y t o t h e and s o u t h e r n p a r t o f the i n t e r i o r .  southwestern  I n Yukon the group a p p e a r s  on "both f l a n k s o f t h e C o a s t Range; i n A l a s k a i t i s w e l l developed  on the n o r t h e r n f r o n t o f the A l a s k a range, hut south  o f t h e range a r e a s o f s i m i l a r r o c k s a r e d o u b t f u l l y  correlative  w i t h the main development i n t h e i n t e r i o r . I n the f o l l o w i n g  discussion  o f the general character  o f the members o f the Yukon g r o u p t h r e e g e n e t i c t y p e s a r e recognized: (a) S e d i m e n t a r y s c h i s t s and g n e i s s e s . (b) Igneous s c h i s t s o f s u r f i c i a l o r i g i n . (c) G r a n i t i c a  ( )  gneisses.  S e d i m e n t a r y s c h i s t s and g n e i s s e s . Among t h e v a r i o u s t y p e s o f s c h i s t s and g n e i s s e s  w i t h i n t h e Yukon g r o u p t h o s e o f s e d i m e n t a r y widespread.  o r i g i n a r e most  I n Yukon t h e s e r o c k s a r e known as t h e "Hasina  s e r i e s " , i n A l a s k a they have t h e name " B i r c h Greek s c h i s t " . Where t h e Yukon g r o u p has been s t u d i e d i n any d e t a i l t h e s e d i mentary members have been found t o occupy a b a s a l p o s i t i o n i n the sequence.  The H a s i n a  s e r i e s and t h e B i r c h Greek  schist  a r e t h e r e f o r e c o n s i d e r e d t o be t h e o l d e s t r o c k s known i n Yukon or Alaska. The v a r i o u s l i t h o l o g i c t y p e s i n c l u d e : q u a r t z - m i c a , m i c a , and c a l c a r e o u s q u a r t z i t e gneissio  schists, with  phases; c r y s t a l l i n e l i m e s t o n e s , sheared  and carbonaceous o r g r a p h i t i c s c h i s t s .  quartzites,  conglomerates,  Garnet and e p i d o t e  '-20- •  ' -  v a r i e t i e s a r e g e n e r a l l y confined, to zones o f c o n t a c t me tamo r phism. The  q u a r t z i t e s and micaceous s c h i s t s a r e by f a r t h e  most abundant.  These r o c k s a r e composed o f q u a r t z and m i c a s ,  t h e d i f f e r e n t t y p e s b e i n g due to d i f f e r e n t p r o p o r t i o n s o f t h e minerals.  Q u a r t z i s most abundant, but g i v e s way t o s e r i c i t e ,  muscovite,  and b i o t i t e i n the m i c a s c h i s t s .  Occasionally bio-  t i t e i s p l e n t i f u l enough t o c l a s s t h e r o c k a s a b i o t i t e  schist.  C h l o r i t e , c a l c i t e , k a o l i n , and m a g n e t i t e a r e p r e s e n t a s a r u l e , but i n c o n t a c t zones t h e m i n e r a l o g y  i s o f t e n much more complex  w i t h t h e development o f m i n e r a l s such as e p i d o t e , z o i s i t e , g a r n e t , s t a u r o l i t e , z i r c o n , r u t i l e , t i t a n i t e , amphibole, t o u r m a l i n e , l i m o n i t e , and g l a u e o p h a n e .  There i s u s u a l l y a l i t t l e  f e l d s p a r a s s o c i a t e d w i t h t h e q u a r t z o f t h e s e s c h i s t s , and i n some l o c a l i t i e s t h e f e l d s p a r c o n t e n t  i s h i g h enough t o c l a s s  the r o c k a s a g n e i s s i c phase o r g n e i s s . S h e a r e d c o n g l o m e r a t e s f o u n d i n the S i x t y m i l e d i s t r i c t are b e l i e v e d to represent l o c a l l y coarser f a c i e s o f the quartzites.  The w r i t e r h a s s e e n q u a r t z - p e b b l e  conglomerates,  a m i c a c e o u s m a t r i x , i n t h e s c h i s t group o f l o w e r P e l l y  with  river.  A s h o r t d i s t a n c e f r o m t h e s e , and a p p a r e n t l y a c r o s s a f a u l t , were c o a r s e r c o n g l o m e r a t e s made up o f b o u l d e r s o f b a s i c f l o w r o c k , much s h e a r e d  and g r a d i n g i n t o f i n e g r a i n e d , dark g r e e n  schist. The crystalline.  l i m e s t o n e s a r e u s u a l l y s i l i c e o u s and h i g h l y Secondary m i n e r a l s d e v e l o p e d  tremolite. 1. C o c k f i e l d , W.E.-  G.G-.S. Mem. 123, p. 1$-.  a r e s e r i c i t e and  The  presence of g r a p h i t e  quartzites.  o f t e n causes b a n d i n g o f  G r a d a t i o n s o c c u r to t y p e s w h i c h may  the  be c l a s s e d  as  graphite s c h i s t s . The  development o f the v a r i o u s s c h i s t t y p e s i s  b e l i e v e d to be due tion. has  l a r g e l y to o r i g i n a l d i f f e r e n c e s i n composi-  I t seems p r o b a b l e , however, t h a t r e g i o n a l metamorphism  to some e x t e n t  a c c e n t u a t e d o r i g i n a l d i f f e r e n c e s ; the  less  competent beds o f the  sedimentary s e r i e s probably s u f f e r e d  greatest a l t e r a t i o n .  I n the l e a s t a l t e r e d p o r t i o n s o f t h e s e  r o c k s a p a r a l l e l arrangement o f the and  the  constituents i s exhibited  d e t r i t a l f a b r i c i s recognizable.  p o r t i o n s are c o m p l e t e l y  The  most a l t e r e d  r e c r y s t a l l i z e d to s c h i s t s and  i n w h i c h no v e s t i g e o f o r i g i n a l t e x t u r e little  i s known o f the  i n the  sedimentary assemblage.  types,  such as the  gneisses  remains.  sequence o f the v a r i o u s In Alaska  q u a r t z i t e s and  the  the  types  the more massive  q u a r t z - m i c a s c h i s t s , are  b e l i e v e d to c h a r a c t e r i z e the l o w e r p a r t of the B i r c h Greek schist,  limestone  o c c u r s a t v a r i o u s p o r t i o n s o f the  but l i k e the g r a p h i t i c s c h i s t s , a p p e a r s t o be most i s t i c o f the u p p e r p a r t . p e r s i s t e n t but Klondike  The  limestone  section, character-  developments are  a r e more o r l e s s l e n t i c u l a r i n form.  I n the  region McConnell^ notes that " c l a s t i c gneisses  some o f the s c h i s t s " and  not  in  s e c t i o n s u n d e r l i e the l e s s a l t e r e d q u a r t z - m i c a p o s t u l a t e s t h a t the f o r m e r may  r o c k s t h a n the q u a r t z - m i c a s c h i s t s .  be much o l d e r  A somewhat s i m i l a r c o n -  d i t i o n p r e v a i l s i n the B i r c h Greek s c h i s t o f the 1. M c C o n n e l l , R.G.-  Circle  K l o n d i k e G o l d . F i e l d s , C.G.S. An.Rpt. v o l . x i v , p . l j b , 1?05»  ™  ttE  *"* 2 2 * quadrangle,Alaska, apparently  o f which P r i n d l e  1  s t a t e s : "The f o r m a t i o n  becomes i n c r e a s i n g l y g n e i s s o i d w i t h d e p t h , a n d the  o b s e r v e d f a c t s i n d i c a t e t h a t a t t h e base i t i s c l o s e l y w e l d e d t o a n c i e n t g r a n i t i c i n t r u s i v e s t h a t have been metamorphosed t o gneisses and  by t h e same p r o c e s s t h a t metamorphosed the q u a r t z i t e s  interbedded  slates to s c h i s t s . "  (b) I g n e o u s S c h i s t s o f S u r f i o i a l , O r i g i n . The r o c k s d e s c r i b e d u n d e r t h i s h e a d i n g v a r y w i d e l y i n age a n d o r i g i n , t h e i n t e r p r e t a t i o n o f t h e i r r e l a t i o n s h i p s b e i n g one o f t h e most d i f f i c u l t p r o b l e m s i n the s t u d y o f the Yukon group.  A l t h o u g h g e n e r a l l y b e l i e v e d t o be d e r i v e d f r o m v o l c a n i c  rocks and near-surface  i n t r u s i o n s , t h e y show marked a f f i n i t i e s  w i t h both t h e s e d i m e n t a r y ( H a s i n a ) s e r i e s and t h e g r a n i t e gneisses.  I t i s probably  due t o the p r e s e n c e o f t h e s e s c h i s t s  o f d o u b t f u l c h a r a c t e r t h a t t h e combined members o f t h e Yukon g r o u p have been mapped a s a complex i n many p a r t s o f Yukon and Alaska.  The i g n e o u s s c h i s t s , a l t h o u g h  found throughout t h e  d i s t r i b u t i o n o f t h e Yukon g r o u p , have n o t t h e e x t e n s i v e opment o f t h e s e d i m e n t a r y members.  devel-  They a r e w e l l known i n t h e 2  Klondike  r e g i o n , and i n t h e S i x t y m i l e r e g i o n where C o c k f i e l d  s u b d i v i d e d them i n t o two g r o u p s : ( l ) S e r i c i t e and c h l o r i t e (2.) A m p h i b o l i t e s  schists.  o r hornblende  schists.  The d e s c r i p t i o n s g i v e n here a r e t a k e n f r o m t h e 3 4 reports on Klondike and S i x t y m i l e regions. 1. P r i n d l e , I.M.- C i r c l e Quad., U.S.G.S. B u l l . 5 3 8 , p.24, 1913. 2. C o c k f i e l d , W.E.- C.G.S. Mem.123, pp.10-21, 1921. 3. M c C o n n e l l , R.G.- C.G.S.An.Rpt. , V o l . x i v , p a r t B,pp.1.5-23,1905. 4. C o c k f i e l d , W.E.- R p t . c i t e d T pp.10-21.  S e r i c i t e and, c h l o r i t e  schists.  These s c h i s t s resemble i n appearance t h e most comp l e t e l y r e c r y s t a l l i z e d , r o c k s o f the H a s i n a on t h e one hand and t h e most s h e a r e d o f t h e g r a n i t e g n e i s s e s on t h e o t h e r . The  s e r i c i t e s c h i s t s a r e most abundant.  They a r e  composed o f q u a r t z , f e l d s p a r , s e r i c i t e , and c h l o r i t e , w i t h minor p r o p o r t i o n s o f magnetite,  p y r i t e , hematite,  e p i d o t e , z i r c o n , k a o l i n and c a l c i t e .  zoisite,  The f e l d s p a r s a r e o r t h o -  c l a s e and p l a g i o c l a s e ( u s u a l l y a l b i t e o r o l i g o c l a s e ) . With an i n c r e a s e i n t h e amount o f c h l o r i t e  transi-  t i o n s o c c u r from t h e s e r i c i t e s t o c h l o r i t e s c h i s t s . s c h i s t s a l s o occur interbanded with the s e r i c i t e s .  Chlorite The  development o f t h e c h l o r i t e s i s s u b o r d i n a t e t o t h a t o f t h e s e r i c i t e s , and the a l t e r n a t i n g bands a r e b e l i e v e d t o be due t o dykes and s i l l s o f t h e c h l o r i t e s c u t t i n g t h e s e r i c i t e  schists.  Rounded b l e b s o f q u a r t z and f e l d s p a r found i n l e s s a l t e r e d p h a s e s o f t h e s e r o c k s a r e thought  to represent  original  porphyrinic, texture.  B u t g r a n u l a t i o n and complete r e c r y s t a l -  l i z a t i o n a r e common.  Some o f t h e r e c r y s t a l l i z e d v a r i e t i e s  appear t o be i d e n t i c a l w i t h r e c r y s t a l l i z e d p o r t i o n s o f t h e elastic schists.  P r o g r e s s i v e f a i l u r e o f the q u a r t z  phenocrysts  and i n c r e a s e o f the development o f those o f f e l s p a t h i c compos i t i o n shows t r a n s i t i o n i n t o g r a n i t i c g n e i s s e s . The  s e r i c i t e and c h l o r i t e s c h i s t s a r e d i s t i n c t l y i n -  t r u s i v e i n t o t h e N a s i n a s e r i e s i n the S i x t y m i l e r e g i o n and t h e Klondike.  I n the K l o n d i k e area McConnell  grouped t h e s e r i c i t e s  and c h l o r i t e s w i t h t h e g r a n i t e g n e i s s e s under t h e name K l o n d i k e s e r i e s b e l i e v i n g t h a t t h e g r a n i t e s r e p r e s e n t e d deeper phases  -24-'' but a l l t y p e s were contemporaneous i n o r i g i n and age. S i x t y m i l e a r e a C o c k f i e l d a r g u e s t h a t the s c h i s t s are by the g r a n i t e g n e i s s and are t h e r e f o r e o l d e r .  A  I n the intruded  similar  r e l a t i o n s h i p i s g i v e n by C a i r n e s f o r the r o c k s of the K l o t a s s i r area"*" where the g n e i s s e s a r e shown as y o u n g e r t h a n the  igneous  schists. Amphibolites. The subordinate  amphibolites  o r h o r n b l e n d e s c h i s t s form a n o t h e r  p a r t o f the Yukon g r o u p .  They i n c l u d e s e d i m e n t a r y  and  i g n e o u s t y p e s w h i c h are i n d i s t i n g u i s h a b l e i n the f i e l d  may  be s e p a r a t e d u n d e r the m i c r o s c o p e .  The  but  f i r s t t y p e i s com-  posed o f q u a r t z , i n an i r r e g u l a r m o s a i c , w i t h bands o f h o r n blende,  z o i s i t e , e p i d o t e , and g a r n e t .  The  presence o f  sericite  sometimes forms v a r i e t i e s w h i c h cannot be d i s t i n g u i s h e d f r o m quartz-mica  s c h i s t s o f the H a s i n a s e r i e s .  are most common and range f r o m t h o s e composition  The  types  equivalent to d i o r i t e s i n  to phases as b a s i c as p y r o x e n i t e .  h o r n b l e n d e and  igneous  They c o n s i s t o f  p l a g i o c l a s e ( l a b r a d o r i t e ) with subordinate,  v a r y i n g p r o p o r t i o n s o f b i o t i t e and pyroxene ( d i o p s i d e  but  and  augite) • These r o c k s , a l t h o u g h  i n j e c t e d by  s t r i n g e r s of  g r a n i t e g n e i s s , a r e c l o s e l y a s s o c i a t e d w i t h the g n e i s s , as a r u l e , and a r e b e l i e v e d to be, i n p a r t a t l e a s t , b a s i c d i f f e r e n t i a t e s o f the g n e i s s magma.  Some show remnants o f p o r p h y r i t i c  t e x t u r e and may  have been f l o w r o c k s , o t h e r s were d o u b t l e s s l y  deeper s e a t e d .  T h e i r r e l a t i o n t o t h e s e r i c i t e and  1. C a i r n e s , D.D.-  C.G.S. Sum.Rpt., 1916,  pp.27-28.  chlorite  -25s c h i s t s i s unknown, "but most o f them appear to be younger t h a n the Hasina  series. The  blende  d e s c r i p t i o n of the s e r i c i t e , c h l o r i t e , and  s c h i s t s a p p l i e s i n a g e n e r a l way  rocks throughout  of  similar  t h e range o f the B i r c h Greek S c h i s t group and  the Yukon g r o u p .  I n the m a j o r i t y o f cases t h e s e r o c k s a r e  b e l i e v e d t o be o f i g n e o u s (c) G r a n i t i c  to exposures  horn-  origin.  Gneisses.  The g r a n i t i c g n e i s s e s , most r e c e n t r o c k s o f t h e Yukon g r o u p , a r e known i n Yukon and t o some e x t e n t i n A l a s k a as t h e P e l l y g n e i s s .  They a r e b e s t d e v e l o p e d  i n the  central  zone o f the a r e a u n d e r l a i n by the r o c k s o f the Yukon group. G r a n i t e s a r e the most common type but v a r i a t i o n s i n composit i o n o c c u r t o r o c k s as b a s i c as gabbro.  T e x t u r a l l y there i s  g r a d a t i o n from massive g n e i s s i c v a r i e t i e s i n t o quartz-mica s c h i s t s .  feldspathic  The more t y p i c a l g n e i s s o i d t y p e i s  c h a r a c t e r i z e d by many augen, sometimes o f q u a r t z , but more often of f e l s p a r . I t i s i m p o s s i b l e to g i v e any q u a n t i t a t i v e o f the c o m p o s i t i o n o f t h e s e r o c k s .  The  d e s c r i p t i o n s i n the  l i t e r a t u r e a r e q u a l i t a t i v e and a r e g i v e n i n g e n e r a l The  terms.  f o l l o w i n g b r i e f e x t r a c t s a r e t a k e n from r e p o r t s o f w i d e l y  separated 1.  description  localities.  A t l i n d i s t r i c t , B r i t i s h Columbia ( l a t . 59°30' H. , l o n g . 134°30» "The  W.)  1  g n e i s s e s are g r e y i s h t o dark g r e e n i s h , medium  1 . C a i r n e s , D . D . - A t l i n D i s t r i c t , B . C . , G.G.S.Mem.37,pp.49-50,1913.  -26t o c o a r s e l y t e x t u r e d r o c k s which have a d e c i d e d l y g n e i s s o i d h a b i t , and i n w h i c h o r t h o c l a s e , p l a g i o c l a s e , and e i t h e r " b i o t i t e or hornblende  o r b o t h , can be r e a d i l y d e t e c t e d by the  unaided  .eye. Under the m i c r o s c o p e  t h e s e r o c k s a r e seen t o  consist  l a r g e l y of o r t h o c l a s e , m i c r o c l i n e , p l a g i o c l a s e , b i o t i t e , b l e n d e ^ e p i d o t e , c h l o r i t e , and a c c e s s o r y i r o n - o r e .  The  hornfeld-  s p a r s v a r y c o n s i d e r a b l y i n r e l a t i v e amounts; i n some specimens the a l k a l i f e l d s p a r s p r e d o m i n a t e ,  but i n o t h e r s the  lime-alkali  f e l d s p a r s c o n s t i t u t e the g r e a t e r p o r t i o n o f the r o c k mass. C h l o r i t e and e p i d o t e as w e l l as z o i s i t e a r e g e n e r a l l y promine n t , and i n some s e c t i o n s the o r i g i n a l f e r r o - m a g n e s i a n  minerals  have been e n t i r e l y r e p l a c e d ; g e n e r a l l y , however, v a r y i n g amounts o f b i o t i t e and hornblende  still  remain."  These r o c k s a r e d e s c r i b e d under the name  1  'Gneisses ,  but a r e c o r r e l a t e d w i t h the P e l l y g n e i s s e s o f Yukon v a l l e y . 2.  G e n e r a l r e g i o n o f Yukon r i v e r , below P e l l y r i v e r and t o the Alaska-Yukon R.G.  t a i n i n g t o the  boundary.  McConnell  has g e n e r a l i z e d the i n f o r m a t i o n p e r -  ' G r a n i t e G n e i s s e s ' f o u n d a l o n g the Upper Yukon  valley."*The g n e i s s o c c u r s i n a b e l t e x t e n d i n g from Nordenskio3i.d r i v e r n o r t h w e s t  f o r J80 m i l e s t o Tanana r i v e r n e a r t h e  mouth o f D e l t a r i v e r .  On White and S t e w a r t r i v e r s the a r e a i s  known to be 110  m i l e s wide.  The p r i n c i p a l c o n s t i t u e n t s o f the g n e i s s e s a r e q u a r t z , 1.  M c C o n n e l l , R.G.-'The S o - e a l l e d B a s a l G r a n i t e o f Yukon V a l l e y * , Araer.Geol. V o l . x x x , pp.55-62.  o r t h o c l a s e , o l i g o c l a s e and a l b i t e i n v a r y i n g p r o p o r t i o n s . B i o t i t e i s common, and h o r n b l e n d e  i s often present.  i s a l m o s t u n i v e r s a l l y p r e s e n t a s a secondary  m i n e r a l ; garnet  i s o f l o c a l o c c u r r e n c e ; and c h l o r i t e , m u s e o v i t e , are  Epidote  and s e r i c i t e  common. The  s c h i s t o s i t y o f t h e g n e i s s e s i s f a r from  uniform,  the same a r e a o f t e n i n c l u d i n g f i n e g r a i n e d w e l l f o l i a t e d m i c a s c h i s t s , o r d i n a r y g n e i s s e s , and c o a r s e g n e i s s o i d g r a n i t e s showing l i t t l e  deformation.  The d i p s o f t h e f o l i a t i o n a r e l o w  as a r u l e , a v e r a g i n g l e s s t h a n 3 0 ° ; h i g h d i p s a r e l o c a l . Concerning  the s t r u c t u r e McConnell  s t a t e s t h a t the  g n e i s s e s i n some a r e a s have been t h r o w n i n t o wide r e g u l a r f o l d s , i n o t h e r s t h e d i p i s c o n s t a n t i n t h e same d i r e c t i o n and the g n e i s s e s a r e o v e r l a i n and u n d e r l a i n by c l a s t i c The  schists.  s t r i k e o f t h e g n e i s s e s i n Yukon v a l l e y i s g e n e r a l l y n o r t h -  w e s t , b u t n o r t h e a s t s t r i k e s have a l s o been o b s e r v e d . a l l y the planes o f s c h i s t o s i t y f o l l o w curved courses. s t r i k e o f t h e g n e i s s e s i s o f t e n conformable c l a s t i c s c h i s t s but i s n o t always  so.  OccasionThe  to that o f the  The s t r i k e s a r e  g e n e r a l l y n o r t h w e s t e r l y , b u t n o r t h e a s t e r l y s t r i k e s have been observed  i n a few p l a c e s . The  r e s t of McConnell's  paper i s d e v o t e d t o a demons  s t r a t i o n o f the f a c t t h a t t h e g r a n i t i c g n e i s s e s a r e i n t r u s i v e i n t o t h e c l a s t i c metamorphics.  T h i s r e l a t i o n s h i p has been  c o n f i r m e d by more r e c e n t i n v e s t i g a t i o n s . 3.  Dennison Pork d i s t r i c t , A l a s k a ( l a t . 6 3 ° 4 0 V N . , l o n g . 142°  W.)  1  • -28- •' J.B. M e r t i e g r o u p s t h e i n t r u s i v e g n e i s s e s o f t h i s d i s t r i c t under t h e name ' P e l l y G n e i s s ' and r e c o g n i z e s  types  t h a t appear t o he c l a s s i f i a b l e a s o r i g i n a l l y g r a n i t e , , q u a r t z m o n z o n i t e , g r a n o d i o r i t e , q u a r t z d i o r i t e , and q u a r t z g a b b r o . " I n the g r a n i t i c t y p e s q u a r t z , o r t h o c l a s e o r m i c r o c l i n e , a l b i t e , and m i c a seem t o c o n s t i t u t e t h e e s s e n t i a l m i n e r a l components; t h e a c c e s s o r y m i n e r a l s a r e a p a t i t e , g a r n e t , and m a g n e t i t e ,  and the secondary  zircon,  minerals quartz, s e r i -  c i t e , s e v e r a l v a r i e t i e s o f c h l o r i t e , e p i d o t e , c a l c i t e , and i r o n hydroxides.  Of the m i c a s , b i o t i t e i s much more common t h a n  m u s c o v i t e , but a s t h e s e r o c k s v e e r t o w a r d muscovite  feldspathic  becomes more common than b i o t i t e .  schist  The m o n z o n i t i c and  d i o r i t i c t y p e s c o n t a i n u s u a l l y b o t h o r t h o c l a s e and s o d a - l i m e p l a g i o c l a s e i n v a r y i n g amounts, though i n a few such o r t h o c l a s e i s e n t i r e l y absent.  Green h o r n b l e n d e  rocks  becomes t h e  p r o m i n e n t m a f i c m i n e r a l i n p l a c e o f m i c a , and t i t a n i t e and magnetite The  become more prominent among t h e a c c e s s o r y m i n e r a l s .  quartz gabbroic types are c l o s e l y r e l a t e d to t h e quartz  d i o r i t e s , i n that hornblende,  and n o t p y r o x e n e , s t i l l  consti-  t u t e s t h e main dark m i n e r a l , a l t h o u g h t h e p l a g i o c l a s e i s s u f f i c i e n t l y b a s i c t o r e n d e r t h e d e s i g n a t i o n q u a r t z gabbro applicable.  1 1  M e r t i e n o t e s t h a t the most i n t e r e s t i n g p e t r o g r a p h i c f e a t u r e i s t h e c o n s t a n t and l o c a l l y h i g h p e r c e n t a g e among the a l k a l i f e l d s p a r s o f the g r a n i t i c g n e i s s e s .  of albite He con-  s i d e r s t h e a l b i t e t o be o f t h r e e t y p e s : (1) A l b i t e t h a t r e p l a c e s o r t h o c l a s e o r p l a g i o c l a s e by the p r o c e s s o f a l b i t i z a t i o n .  F i g . 5<  L o c a l i t i e s a t which rocks c o r r e l a t e d w i t h t h e Yukon and T i n d i r g r o u p s o c c u r i n Yukon T e r r i tory.  The numbers r e f e r t o numbers i n t h e  m a r g i n o f the t e x t . Yukon group i n r e d . T i n d i r group i n b l u e .  F i g . 6.  L o c a l i t i e s a t which rocks c o r r e l a t e d w i t h the Yukon and T i n d i r groups o c c u r i n A l a s k a . Yukon group i n r e d . ' T i n d i r group i n b l u e .  :  ( 2 ) O r i g i n a l magmatic m a t e r i a l ; a l b i t e  intergrown  with, q u a r t z and o r t h o c l a s e i n a f a b r i c t h a t seems o r i g i n a l . (3) lite  C r y s t a l l o b l a s t i c a l b i t e t h a t grows l i k e  i n t h e metamorphic r o c k s , w i t h many i n c l u s i o n s o f o t h e r  rock forming m i n e r a l s . pa t h i c 4.  ottre-  This i s c h a r a c t e r i s t i c of the f e l d s -  schists.  F a i r b a n k s d i s t r i c t , A l a s k a ( l a t . 65  N., l o n g . 148° W.)  The g r a n i t e g n e i s s o f t h i s d i s t r i c t o c c u r s i n bands, up t o s e v e r a l hundred f e e t w i d e , p a r a l l e l t o t h e s c h i s t s i n which i t o c c u r s .  I n one case i t forms a d y k e , a few hundred  f e e t t h i c k , c u t t i n g the s c h i s t s . Of t h e p e t r o g r a p h y  o f t h e g n e i s s e s P r i n d l e and K a t z  state: / "The u s u a l t y p e c o n t a i n s augen o f m i c r o c l i n e i n a granular massof quartz, feldspar, s e r i c i t e , b i o t i t e , t i t a n i t e , and o r t h i t e .  The f e l d s p a r o f t h e groundmass i n -  c l u d e s a l k a l i f e l d s p a r and s o d a - l i m e most common v a r i e t y .  epidote,  f e l d s p a r ; a l b i t e i s the  The m i n e r a l s o f w h i c h t h e s e r o c k s a r e  composed have been s h a t t e r e d and r e c r y s t a l l i z a t i o n h a s t a k e n place. Age and C o r r e l a t i o n . The f i r s t r e f e r e n c e t o r o c k s w h i c h may be c l a s s e d w i t h t h e Yukon g r o u p o c c u r s i n t h e w r i t i n g s o f C M . Dawson and R.G-. M c C o n n e l l  who conducted  the o r i g i n a l g e o l o g i c a l e x p l o r a -  t i o n s i n Yukon and i n t e r i o r A l a s k a .  Dawson, i n a r e p o r t o f a  1. P r i n d l e , I . M . and K a t z . F . J . - F a i r b a n k s D i s t r i c t , U.S.G.S. B u l l . 5 2 5 , pp.65-66, I913.  route  s u r v e y o f Dease, F r a n c e s , and P e l l y r i v e r s , d i v i d e d  ancient  r o c k s i n t o f o u r s u b - d i v i s i o n s , the l o w e r two  the  of which  were u n f o s s i l i f e r o u s : (1) An upper s e r i e s o f "grey and b l a c k i s h , o f t e n l u s t r o u s and sometimes more o r l e s s micaceous c a l c - s c h i s t s and q u a r t z i t e s , i n c l u d i n g b e d s o f l i m e s t o n e o f moderate t h i c k n e s s , w h i c h are o f t e n more or l e s s d o l o m i t i c . " (2) A l o w e r s e r i e s o f " g r e e n i s h and g r e y s c h i s t s , g e n e r a l l y f e l s p a t h i c o r h o r n b l e n d i c , but o f t e n q u a r t z o s e and i n c l u d i n g d i s t i n c t l y micaceous and t a l e o s e s c h i s t s , w i t h some bands o f l i m e s t o n e ; the l i t h o l o g i c a l c h a r a c t e r o f t h i s s u b - d i v i s i o n being exceedingly v a r i e d . " ^ f Dawson, G.M.-  He two  Can. G. and N a t . H i s t . S u r v . , Y o l . I I I , p.32B, 1889.  considered  t h e s e two  An.Rpt. I«b7-b«,  s u b - d i v i s i o n s as w e l l as  o v e r l y i n g f o s s i l i f e r o u s ones to be P a l e o z o i c and  the  "probably  r e f e r a b l e to s e v e r a l o f the main s u b - d i v i s i o n s o f the  geologi-  cal scale." Dawson f u r t h e r s t a t e s , i n d i s c u s s i n g the g r a n i t e s Upper P e l l y and  Dease r i v e r s r e g i o n :  of  "In close a s s o c i a t i o n with  t h e s e g r a n i t e s a r e some g n e i s s i c r o c k s and h o l o c r y s t a l l i n e m i c a - and h o r n b l e n d e - s c h i s t s . . . . . . . . r e g a r d e d t h a n as r e p r e s e n t i n g  as A r c h e a n , r a t h e r  highly altered Paleozoic  rocks."#  ' ? ^ I b i d . - p.34B. I n ,the same y e a r (188?) as Dawson's s u r v e y M c C o n n e l l t r a v e r s e d from the M a c k e n z i e r i v e r , by way  of Porcupine  river,  t o the Yukon w h i c h he f o l l o w e d upstream t o l a k e l i n d e m a n i n the Coast r a n g e .  H i s c l a s s i f i c a t i o n o f the c r y s t a l l i n e r o c k s  found a l o n g the v a l l e y o f the Upper Yukon was  g i v e n as f o l l o w s :  (1) An u p p e r s e r i e s o f " s h e a r e d and a l t e r e d g r e e n i s h quartzose s c h i s t . With t h i s are a s s o c i a t e d g r e e n i s h c h l o r i t e b e a r i n g s c h i s t , l u s t r o u s mica s c h i s t s , d i a b a s e s , and s e r p e n t i n e s . The s c h i s t s a r e i n t e r b e d d e d w i t h o c c a s i o n a l bands o f  • • -3i~  ;  s l a t e s and. c r y s t a l l i n e l i m e s t o n e s , and a r e b r o k e n t h r o u g h many p l a c e s by i g n e o u s i n t r u s i o n s . "  in  ( 2 ) A l o w e r s e r i e s c o n s i s t i n g of "a g r e a t t h i c k n e s s o f w e l l f o l i a t e d m i c a g n e i s s e s , a l t e r n a t i n g w i t h mica and h o r n b l e n d e s c h i s t s , w h i c h a r e d i s t i n c t l y A r c h e a n i n appearance and l i t h o l o g i c a l characters."$ ^McConnell,  R.G.-  Can.G. and N a t . H i s t . S u r v . An.Rpt. V o l . I V , pp. 13D-14D, 1891.  a p a p e r p u b l i s h e d i n 1901,  In  Dawson d e s c r i b e d a  s e r i e s o f h i g h l y metamorphosed s e d i m e n t s and  contemporaneous  bedded v o l c a n i c m a t e r i a l s , w i t h a s s o c i a t e d g n e i s s e s , under the name Shuswap s e r i e s . but he  These r o c k s o c c u r r e d i n B r i t i s h Columbia  c o r r e l a t e d w i t h them s i m i l a r s c h i s t s and g n e i s s e s  Yukon d i s t r i c t , and  c o n s i d e r e d the whole t o be  of  correlative  w i t h the G r e n v i l l e s e r i e s o f e a s t e r n Canada.$ # Dawson, G.M.-  G.S.A. V o l . 1 2 , p p . 6 3 - 6 4 ,  1901*  D u r i n g the y e a r I896 S p u r r t r a v e r s e d the  entire  l e n g t h o f the Y u k o n , e x a m i n i n g i n p a r t i c u l a r the r o c k s Fortymile d i s t r i c t .  His report records the f i r s t g e o l o g i c a l  s e c t i o n a p p l i c a b l e p a r t i c u l a r l y t o A l a s k a and at  of  the f i r s t  attempt  s u b - d i v i s i o n o f the o l d e r s c h i s t o s e r o c k s i n w h i c h forma-  t i o n a l names were u s e d ; Upper s e r i e s - F o r t y m i l e  series.  I n t e r c a l a t e d marble and q u a r t z i t e , w i t h m i c a c e o u s , g a r h e t i f e r o u s , and g r a p h i t i c s c h i s t s . l o w e r s e r i e s - B i r c h Creek  hornblendic  series.  Q u a r t z i t e , q u a r t z i t e s c h i s t , quartz-mica minor p r o p o r t i o n o f s c h i s t o f i g n e o u s o r i g i n .  schist, with  B a s a l g r a n i t e o r g r a n i t e gneiss.?/ f S p u r r , J.E.- U.STG.S. l b t h An.Rpt". , p t . 3 , The  s e p a r a t i o n o f the  pp.134-155, 1898.  " F o r t y m i l e " as a s e r i e s was  (3  "based on the predominance o f l i m e s t o n e i n t h e u p p e r p a r t o f t h e s u c c e s s i o n , a d i s t i n c t i o n which was  found t o be so vague i n  o t h e r d i s t r i c t s t h a t the name was n e v e r u s e d by o t h e r g e o l o gists.  S p u r r d i d not v e n t u r e an age assignment  f o r these rocks  o t h e r t h a n a b r i e f n o t e t h a t the b a s a l g r a n i t e was p r o b a b l y the e q u i v a l e n t o f t h a t d e s c r i b e d by Dawson and t h e r e f o r e o f A r c h e a n age. In.1898 B r o o k s t r a v e r s e d from Skagway t o Tanana by way  o f White P a s s , Yukon r i v e r , and t h e White and Tanana  rivers. (1)  He  d i v i d e d the a n c i e n t s c h i s t s i n t o two  parts:  Hasina s e r i e s - v a r i o u s s c h i s t s , mainly of sedimentary origin. Tanana s c h i s t s - g n e i s s o i d and s c h i s t o s e r o c k s , d o m i n a n t l y m i c a c e o u s , c a l c a r e o u s , and g r a p h i t i c .  (2)  Gneissic s e r i e s - mainly of g r a n i t i c  t B r o o k s , A.H.-  origin.#  TT.S.G.S. 20th An.Rpt., pt . 7 , pp.46.0-469,  S e p a r a t e names were g i v e n f o r the two groups p a r t ( 1 ) because  1900.  of  the Tanana s c h i s t s , f o u n d a l o n g t h e Tanana  r i v e r , were too f a r away f r o m the H a s i n a s e r i e s o f l o w e r White r i v e r t o be c o r r e l a t e d w i t h t h e l a t t e r .  However, Brooks  e v i d e n t l y c o n s i d e r e d them e q u i v a l e n t , f o r he s t a t e s : " I t h i n k q u i t e l i k e l y t h a t when the r e g i o n has been s t u d i e d i n more d e t a i l the H a s i n a s e r i e s w i l l be found t o i n c l u d e the Tanana schists.'•#<••. f- B r o o k s , A.H.-  r e p o r t c i t e d , p.4?9.  D u r i n g the n e x t summer B r o o k s t r a v e r s e d a g a i n from Lynn C a n a l , f o l l o w i n g K l e h i n i r i v e r , Kluane l a k e , White F o r t y m i l e r i v e r s , to E a g l e on the Yukon.  and  He combined the  (4)  •• - 3 3 H a s i n a s e r i e s and t h e Tanana s c h i s t s under t h e name K o t l o s e r i e s , a t e r m d e f i n e d t o i n c l u d e a l l t h e metamorphic r o c k s o f dominantly  sedimentary o r i g i n .  The s e r i e s was c o r r e l a t e d w i t h  the combined F o r t y m i l e and B i r c h Greek s e r i e s o f S p u r r and considered  t o he o f l o w e r P a l e o z o i c and p r e - C a m b r i a n age.  The  name G n e i s s i c s e r i e s was r e t a i n e d as b e f o r e f o r t h e presumably basal  granites.#  t B r o o k s , A.H.- U.S.G.S. 2 1 s t An.Rpt., p t . 2 , p p . 3 5 b " 3 5 b , IgfioT" Returning 1898  t o the work o f Canadian g e o l o g i s t s ; i n  M c C o n n e l l t r a v e r s e d B i g Salmon, T e s l i n , and H i s u t l i n  rivers.  A s e r i e s o f q u a r t z i t i c and micaceous s c h i s t s and c r y s -  t a l l i n e limestones  on the B i g Salmon r i v e r he c o r r e l a t e d w i t h  the Shuswap s e r i e s o f t h e S e l k i r k Range o f B r i t i s h  Columbia.$  # M c C o n n e l l , R^G.-C.G.S. An.Rpt. V o l . x i , pp.4»a-49a7"T8"98. A s e m i - d e t a i l e d examination  o f t h e r o c k s o f the K l o n -  d i k e d i s t r i c t was c o m p l e t e d by M c C o n n e l l i n 1 9 0 3 . to e f f e c t a g e n e t i c  He was a b l e  c l a s s i f i c a t i o n w h i c h s t i l l forms t h e b a s i s  f o r n o m e n c l a t u r e and s u b - d i v i s i o n o f t h e P r e c a m b r i a n i n Yukon. The  classification:  (1)  Moosehide g r o u p : A l t e r e d d i a b a s e  (2)  Klondike  and s e r p e n t i n e .  series:  (a) S e r i c i t e and c h l o r i t e s c h i s t , d e r i v e d from a c i d and basic porphyries. (b) P e l l y g n e i s s , d e r i v e d f r o m g r a n i t e and q u a r t z porphyries. (3)  (5)  Hasina s e r i e s : q u a r t z i t e , q u a r t z i t e s c h i s t , quartz-mica s c h i s t , w i t h some' c r y s t a l l i n e l i m e s t o n e and c h l o r i t e and a c t i n o l i t e schist.§  (6)  '"-34-.. '  I t i s n o t e d t h a t t h e name ' H a s i n a the  sedimentary s e r i e s .  1  was adopted f o r  M c C o n n e l l c o n s i d e r e d t h e two sub-  d i v i s i o n s o f the Klondike series  to be contemporaneous i n age  and o r i g i n , t h e s e r i c i t e and c h l o r i t e s c h i s t s  representing  s u r f i c i a l phases o f magma w h i c h gave r i s e t o t h e g r a n i t e gneisses.  He s t a t e s t h a t t h e t e r m ' P e l l y g n e i s s ' was proposed r e l a t i o n o f t h e Moosehide group t o the K l o n -  by B r o o k s . T h e  d i k e s e r i e s was n o t f o u n d . McConnell,R.G.- R p t . c i t e d , p.13b. I t i s i n t e r e s t i n g t o n o t e however t h a t Brooks a t t r i b u t e s t h e name t o M c C o n n e l l (Pre-Camb.Geol. o f H.Amer. , U.S.C-.S. Bull.360 , p.883, 1909.) Considerable i n f o r m a t i o n r e g a r d i n g the d i s t r i b u t i o n o f t h e s e r o c k s was o b t a i n e d a b o u t t h e time o f t h e K l o n d i k e s u r v e y i n e x p l o r a t i o n s i n e a s t e r n Yukon. clastic  McConnell found  s c h i s t s , a l o n g the P e l l y below M a c m i l l a n r i v e r , w h i c h  he c o n s i d e r e d t o b e l o n g t o t h e H a s i n a s e r i e s , and i n t h e same l o c a l i t y he d e s c r i b e d c e r t a i n c h l o r i t e and s e r i c i t e s c h i s t s and augen g n e i s s e s a s r e s e m b l i n g t h e K l o n d i k e s c h i s t s . f f f- M c C o n n e l l ,R.G.- C.G.S. Sum.Rpt. 1902, pp.25-29, 1903.  (8)  A g a i n t h e s c h i s t s a l o n g the South F o r k o f B i g Salmon r i v e r were d e s c r i b e d by M c C o n n e l l a s c o n s i s t i n g  of rocks partly  i g n e o u s and p a r t l y s e d i m e n t a r y i n o r i g i n and r e s e m b l i n g t h e gold-bearing schists of Klondike district.7^ =  !  # McConn?ITjRTGT "C.G .S. A r u R p t . , VoT.XIV, P t . A , p." K e e l e , i n an e x p l o r a t i o n o f t h e S t e w a r t r i v e r made i n 1904, mentioned  t h a t the metamorphic r o c k s o f t h i s r e g i o n ,  p a r t i c u l a r l y around Duncan c r e e k and the l o w e r p a r t o f t h e S t e w a r t , p o s s e s s e d t h e c h a r a c t e r i s t i c s o f the H a s i n a s e r i e s . #  (9)  The  e a s t e r n m a r g i n o f the s c h i s t o s e s e r i e s was found  on P e l l y r i v e r b y K e e l e i n 1907.  He f o u n d c r y s t a l l i n e  schists  a l l t h e way up the P e l l y t o K e t z a r i v e r a n d a s most o f t h e r o c k s were c l a s t i c t y p e s h e c o n s i d e r e d them t o r e p r e s e n t t h e Hasina s e r i e s .  O r d o v i c i a n f o s s i l s were found i n a d j o i n i n g  s e d i m e n t s t o t h e n o r t h e a s t , b u t t h e c o n t a c t was n o t observed.# f K e e l e , J . - P e l l y , R o s s , and G r a v e l R i v e r s , G.G.S. Rpt.1097 , PP. 3 2 - 3 3 ,  1910.  •;  I n t h e c o u r s e o f a s u r v e y o f K l u a n e Lake made d u r i n g 1904, quartz-mica  McConnell  observed  district,  a series of well  foliated  s c h i s t s t o w h i c h he gave t h e name 'Kluane  Of t h e s e he s t a t e s : "They d i f f e r from t h e H a s i n a  schists'.  s e r i e s i n the  absence o f . q u a r t z i t e and l i m e s t o n e bands." $ f M c C o n n e l l ,R.G.- G.G.S. Sum.Rp"t. 1904, p.5a, 1905.  "  D.D. C a i r n e s , i n 1905, d e s c r i b e d v a r i o u s s c h i s t s and g n e i s s e s i n Windy Arm d i s t r i c t o f Southern Yukon.  He con-  s i d e r e d t y p e s o f a l l t h e s u b - d i v i s i o n s o f the K l o n d i k e sequence to be p r e s e n t a n d r e f e r r e d them a l l t o t h e p r e - O r d o v i c i a n . ^ f- C a i r n e s , D . D . - G.G.S. Rpt. on Conrad and W h i t e h o r s e d i s t r i c t s , p.24, 1 9 0 8 . D u r i n g 1907 and 1908 C a i r n e s found mica g n e i s s and schistose amphibolite along Hordenskiold r i v e r .  To t h e s e he  gave t h e name 'Razor M o u n t a i n g r o u p " , s t a t i n g however t h a t they resembled  s c h i s t s and g n e i s s e s o f t h e K l o n d i k e  and were p r o b a b l y  district  pre-Ordovician.#  f C a r i n e s , D . D . - G.G.S. Mem.5, p.27, 1910. I n 1912 and 1913 C a i r n e s gave t h e name 'Mt. Stevens g r o u p ' t o t h e combined s e d i m e n t a r y ,  v o l c a n i c , and i n t r u s i v e ,  s c h i s t s a n d g n e i s s e s o f Wheaton and A t l i n d i s t r i c t s . sidered report  the  g e n e r a l age t o he l o w e r P a l e o z o i c .  He con-  I n the A t l i n  t h e g r a n i t e g n e i s s e s were c o r r e l a t e d w i t h  the P e l l y  gneisses.# f  C a i r n e s , D . D * - C.G.S. Mem.31, p p . 4 5 - 4 b , 1912. C.G.S. Mem.37 • p p . 4 8 - 6 1 , 1913. From 1903  t o 1 9 1 1 l.M.  Prindle  of Alaska.  His publications  Yukon-Tanana  of t h i s i n v e s t i g a t i o n are  numerous; t h e ones c i t e d h e r e may be t a k e n as In h i s report l y i g n o r e d the the  on Fortymile  representative.  quadrangle P r i n d l e  entire-  a l r e a d y w e l l - d e v e l o p e d n o m e n c l a t u r e and grouped  following lithologic  cian rocks':  :  c a r r i e d on an e x t e n -  s i v e s t u d y o f the a n c i e n t metamorphics o f the region  "~  t y p e s under the h e a d i n g  quartzite, quartzite  *pre-0rdovi-  s c h i s t , calcareous  schist, quartz-biotite s c h i s t , garnetiferous  quartzite  mica s c h i s t , horn-  b l e n d e s c h i s t , carbonaceous s c h i s t , c r y s t a l l i n e l i m e s t o n e , b i o t i t e gneiss,  hornblende-piagioclase gneiss,  and b i o t i t e  augen g n e i s s . # ^ " P r i n d T e T l T l . - FortymTIe~^uadTT^«S«G.S. 5 0 1 X 7 3 7 5 7 ^ 9 0 9 . Prindle rocks..  d i d not  accomplish a c l a s s i f i c a t i o n o f these  ;In h i s l a t e s t r e p o r t s  regardless  o f c h a r a c t e r o r o r i g i n , under the  s c h i s t ' ( a name d e r i v e d series') •  he grouped t h e whole assemblage, term ' B i r c h Creek  by B r o o k s from S p u r r ' s ' B i r c h Creek  P r i n d l e a s s i g n e d the  B i r c h Creek, s c h i s t t o t h e P r e -  O r d o v i c i a n ( ? ) because he found them t o be o v e r l a i n unconforma b l y by t h e T a t a l i n a g r o u p o f f e l d s p a t h i c stones , c h e r t s ,  fragmentals,  lime-  l a v a s , t u f f s , and b r e c c i a s , w h i c h were i n t u r n  o v e r l a i n by l i m e s t o n e s c o n t a i n i n g  Ordovician f o s s i l s  ~3?ft P r i n d l e , I . M . - F a i r b a n k s ^uad., U.S.G-.S. B u l l . 5 2 5 , (16)  The  same usage ( B i r c h Greek s c h i s t ) was adopted by  Capps f o r the metamorphics o f t h e B o n n i f i e l d r e g i o n on t n o r t h f r o n t o f t h e A l a s k a Range.#  Capps n o t e d t h a t b o t h  ft Capps,S.R.- B o n n i f i e l d r e g i o n , U.S.G.S. B u l l . 5 0 l , pp.20-22, 1912. i g n e o u s and s e d i m e n t a r y t y p e s o c c u r r e d i n the B i r c h schist.  Creek  Re d e s i g n a t e d t h e s e r i e s as p r e - O r d o v i c i a n . B r o o k s and P r i n d l e h a d , i n t h e c o u r s e o f t h e i r  s t u d i e s , d e s c r i b e d a g r o u p o f augen g n e i s s e s and igneous schists.  Capps r e c o g n i z e d and s e p a r a t e d t h e s e under t h e name  ' T o t a t l a n i k a s c h i s t ' , n o t i n g a l s o that the s e r i e s contained much m a t e r i a l o f s e d i m e n t a r y o r i g i n i n i t s l o w e r p a r t . age was n o t d e t e r m i n e d beyond t h e f a c t t h a t i t was i f e r o u s and younger than t h e B i r c h Greek f  Capps ,S.R.- R p t . c i t e d , pp.22-2b. Regarding  O r d o v i c i a n ' , mention  The  pre-Carbon-  schist. ~~  ~"~  ~  "  the use b e f o r e 1 9 1 3 o f t h e term ' p r e s h o u l d be made t h a t i t d e v e l o p e d  from  c o r r e l a t i o n o f t h e o l d e r metamorphic r o c k s o f A l a s k a and Yukon w i t h a s e r i e s o f black, s l a t e s and q u a r t z i t e s w h i c h K i n d l e f o und t o u n d e r l i e O r d o v i c i a n beds a l o n g P o r c u p i n e r i v e r . # K i n d l e ,E.M.- P o r c u p i n e V a l l e y , Bull.G-.S.A. , V o l .19, pp. 320D u r i n g 1911 and 1912 C a i r n e s examined t h e g e o l o g i c a l s e c t i o n a l o n g t h e 1 4 1 s t . m e r i d i a n between Yukon and P o r c u p i n e rivers.  Only a s m a l l a r e a o f s c h i s t o s e r o c k s o c c u r s w i t h i n  the s t r i p o f c o u n t r y w h i c h C a i r n e s mapped, but t h i s a r e a i s  (17)  -38  p a r t o f t h e n o r t h e r n p e r i p h e r y o f the g r e a t development o f these r o c k s s o u t h o f the Yukon r i v e r .  O v e r l y i n g the s c h i s t s i n  apparent u n c o n f o r m i t y he f o u n d but s i i g h t l y metamorphosed l i m e s t o n e beds c o n t a i n i n g Upper and p r o b a b l y M i d d l e Cambrian fossils.  Cairnes concluded, t h e r e f o r e , t h a t the schistose  r o c k s were p r o b a b l y P r e c a m b r i a n  i n age. As he was unable t o  make any s u b - d i v i s i o n s , he proposed "to  t h e new name, Yukon group  i n c l u d e a l l t h e s e o l d e r metamorphosed, s c h i s t o s e and  g n e i s s o i d r o c k s o f b o t h s e d i m e n t a r y and i g n e o u s o r i g i n . " n o t e d t h a t t h i s d e f i n i t i o n makes the Yukon g r o u p  s  It i s  as a name,  the e x a c t e q u i v a l e n t o f the t e r m B i r c h Greek s c h i s t .  Be-  l i e v i n g t h a t i t v/ould prove a u s e f u l f i e l d name, C a i r n e s i n c l u d e d w i t h t h e Yukon group t h e f o l l o w i n g s u b - d i v i s i o n s and g r o u p s , w h i c h have a l r e a d y been d i s c u s s e d : H a s i n a K l o n d i k e s e r i e s , P e l l y g n e i s s e s , Moosehide d i a b a s e  series, (possibly),  B i r c h Greek s e r i e s and F o r t y m i l e s e r i e s , Tanana s c h i s t s . K o t l o s e r i e s , and Mt. Stevens g r o u p ( p o s s i b l y ) .jf F*Gairne"s,I).I).- G.O.S. Mem.b?, pp.40-44T"l914.  ~~  D u r i n g 1913 C a i r n e s a g a i n a p p l i e d t h e name Yukon g r o u p t o t h e s c h i s t s o f Upper White r i v e r . # f- Cairnes,D.D.-""~C.G.S. Mem. 50T*PP~« 68-71, 1915»  ~  Two y e a r s l a t e r , i n K l o t a s s i n a r e a , he s u b d i v i d e d the Yukon group as f o l l o w s : Yukon Group ( P r e - C a m b r i a n ?) 1. P e l l y g n e i s s e s , g r a n i t e g n e i s s . 2. D o m i n a n t l y h o r n b l e n d e s c h i s t and g n e i s s , i n c l u d e a l s o some s e r i c i t i c g n e i s s and schist. Igneous o r i g i n . 3. Appears t o c o r r e s p o n d t o H a s i n a s e r i e s ; mica s c h i s t , mica g n e i s s , q u a r t z - m i c a  -39s c h i s t , quartz-mica g n e i s s , s c h i s t o s e and g n e i s s o i d q u a r t s i t e sheared c o n g l o m e r a t e , p h y l l i t e , and l i m e s t o n e . Sedimentary origin. # C a i r n e s ,D.D.~ K l o t a s s i n a r e a , G.G.S. Sum.Rpt. 191b,p.27 ,19177~ I n 1917 C o c k f i e l d examined the S i x t y m i l e r e g i o n t o t h e west o f the K l o n d i k e ,  H i s c l a s s i f i c a t i o n o f t h e members o f  the Yukon group i s e s s e n t i a l l y a rearrangement o f t h a t o f M c C o n n e l l f o r t h e K l o n d i k e , and r e p r e s e n t s t h e l a t e s t at s u b - d i v i s i o n o f these r o c k s .  attempt  The c l a s s i f i c a t i o n :  1. P e l l y g n e i s s ( ? ) , g r a n i t e g n e i s s . 2. A m p h i b o l i t e s , h o r n b l e n d e o r a m p h i b o l i t e s c h i s t s . 3. K l o n d i k e s e r i e s ( ? ) , s e r i c i t e a n d c h l o r i t e s c h i s t s mainly o f igneous o r i g i n . 4. H a s i n a s e r i e s , q u a r t z i t e , q u a r t z - m i c a s c h i s t s , mica s c h i s t s , sheared c o n g l o m e r a t e , g r a p h i t e s c h i s t s , and c r y s t a l l i n e limestone mainly o f s e d i . mentary o r i g i n . The g r a n i t e g n e i s s , a l t h o u g h  c o r r e l a t e d w i t h the P e l l y g n e i s s ,  i s s e p a r a t e d f r o m the K l o n d i k e s e r i e s ( a s M c C o n n e l l had i t ) because i t a p p e a r s t o be i n t r u s i v e i n t o t h e s e r i c i t e and c h l o r i t e s c h i s t s w h i c h make up the b u l k o f t h e K l o n d i k e The  series.  r e l a t i o n of the amphibolites t o the s e r i c i t e s i s undeter-  mined a n d t o t h e P e l l y g n e i s s and H a s i n a s e r i e s i s p r o b l e m a t i c . The  a m p h i b o l i t e s c o n s i s t o f b o t h sedimentary  w h i c h cannot be s e p a r a t e d i n the f i e l d ; w i t h the Hasina  and igneous  they show a f f i n i t i e s  s e r i e s and, i n p a r t , appear t o be d i f f e r e n t i a -  t e s o f t h e g r a n i t e g n e i s s magma.  They a r e p r o b a b l y f o r t h e  most p a r t younger t h a n t h e r o c k s o f the H a s i n a Hasina  s e r i e s comprises  sedimentary  types  group.  series.  The  t h e o l d e s t r o c k s o f the r e g i o n and i s a  C o c k f i e l d c o n s i d e r e d t h e whole sequence t o  be  Precambrian.^  # Cockfield,W.E.^  G.G.S. Mem.123, p p . l 2 ~ 2 b ,  I921V  ~~  I n r e c e n t y e a r s t h e name Yukon group has g e n e r a l l y been a p p l i e d to v a r i o u s e x p o s u r e s o f t h e o l d e r s c h i s t o s e r o c k s as t h e mapping p r o g r e s s e d .  I n W h i t e h o r s e d i s t r i c t , however,  C o c k f i e l d and B e l l r e t a i n e d t h e t e r m Mt. S t e v e n s group a s i t was  o r i g i n a l l y a p p l i e d w i t h i n t h i s a r e a ; t h e age b e i n g g i v e n as  probably Precambrian.# # C o c k f i e l d ,W.E. & B e I l A . H . 9  C.G.S. Mem.ljO, pp.U-IQ., 1926.  I n t h e d i s t r i c t s o f Dezadeash and A i s h i h i k l a k e s , a d j o i n i n g W h i t e h o r s e a r e a on t h e west and n o r t h w e s t , C o c k f i e l d has  c l a s s e d the s c h i s t o s e r o c k s under t h e name Yukon group on  the b a s i s o f t h e i r l i t h o l o g y and a p p a r e n t b a s a l p o s i t i o n . b o t h c a s e s t h e age i s g i v e n a s p r o b a b l y P r e c a m b r i a n  In  i n keeping  w i t h the g e n e r a l c o n c e p t i o n o f t h e s t a t u s o f t h e Yukon group.# '§ Cockfield",W.E.-  Dezadeash D i s t r i c t , G.G.S. Sum.Rpt. 1^27 p t . A , p.4, 1928. - A i s h i h i k D i s t r i c t , C.G.S. Sum.Rpt. I926, . , p t . A , p.4, 1927.  I t s h o u l d be mentioned t h a t i n t h e Dezadeash d i s t r i c t the Yukon s c h i s t s a r e a p p a r e n t l y o v e r l a i n by a s e r i e s o f a r g i l l i t e s o f w h i c h t h e r e i s some e v i d e n c e % C o c k f i e l d ,W.E.- R p t . c i t e d , p.T*  o f O r d o v i c i a n age.# "  "~"  I n 1928 C o c k f i e l d d e s c r i b e d t h e ' S c h i s t Complex' o f L i t t l e Salmon a r e a a s c o n s i s t i n g o f q u a r t z i t e , mica s c h i s t , c h l o r i t e s c h i s t , and an abundant development o f l i m e s t o n e . predominance o f l i m e s t o n e n o t i c e d elsewhere  The  i s a f e a t u r e w h i c h h a s n o t been  i n Yukon, b u t , a s p r e v i o u s l y mentioned, seems  t o be c h a r a c t e r i s t i c o f t h e E o r t y m i l e r e g i o n o f A l a s k a .  -41Although, t h e o l d e s t i d e n t i f i e d , h o r i z o n o v e r l y i n g t h e was  found i n t h i s d i s t r i c t to "be C a r b o n i f e r o u s  o f the age  (?)  schists  limestone,  of the metamorphic complex C o c k f i e l d s t a t e s :  d e f i n i t e evidence  o f t h e age  o f t h e s e r o c k s was  "No  obtained....  t h e y have u n d o u b t e d l y been s u b j e c t e d t o f o l d i n g and metamorp h i s m t h a t the o l d e r s e d i m e n t a r y  r o c k s have escaped... and  as  i n v e s t i g a t i o n s i n o t h e r p a r t s o f Yukon have shown t h e s c h i s t o s e r o c k s t h e r e to be P r e c a m b r i a n , the s c h i s t group o f Salmon a r e a has  little  a l s o b e e n c l a s s e d i n t h a t era."#  "§ C o c k f i e l d , W . E . ., ...  L i t t l e Salmon A r e a , C7&.S. Sum.Rpt. 192b, ..... , - .... p t . A , pp.4-5, 1929.  Of the s c h i s t s o f Mayo d i s t r i c t C o c k f i e l d s t a t e s : "The  q u a r t z i t e , quartz-mica  s c h i s t , and g r a p h i t e s c h i s t  b e l i e v e d t o b e l o n g t o the N a s i n a i n h i s r e p o r t on K l o n d i k e  s e r i e s , d e s c r i b e d by M c C o n n e l l  d i s t r i c t . . . . . . The  c h l o r i t e s c h i s t s . . . are b e l i e v e d t o b e l o n g Klondike  • ,  sericite  and r  to M c C o n n e l l s  series."$  ft C o c k f i e l d , W . E . .,.  are  •;, ,:•  The  Mayo D i s t r i c t , •, .. • : • •;.  .  • :.  C.G.S. Sum.Rpt. 1923, -.  ,  .  . , .. . p . 3 ,  Pt.A. ,  1924....  ......  f o l l o w i n g i s a b r i e f summary o f the work i n  A l a s k a d u r i n g the l a s t two I n 1915 .  Creek d i s t r i c t  ( i )  decades.  Capps c o r r e l a t e d t h e m i c a s c h i s t o f '  Willow  .  , s o u t h o f the A l a s k a range and the  Talkeetna  mountains, w i t h s i m i l a r s c h i s t s i n s o u t h - c e n t r a l Alaska; near Lake K l u t i n a ^ " ' ; on Dadina r i v e r n e a r Mount Drum^^ ; i n the (4) (5) Gulkana d i s t r i c t ; and i n the I l i a m n a r e g i o n . # 2  U;  Capps,S.R.- W i l l o w Creek D i s t r i c t , U . S . G . S . B u l l . b O ' / ,  p.29,  (2) (3;  S c h r a d e r , P . C - U.S.G.S. 2 0 t h An.Rpt. , p t . 7 ,p.410 , I898. M e n d e n h a l l ,W.CCopper R i v e r r e g i o n , U.S. G.S. P r o f .Pap. 41, pp.27-30, 1903.  ' . ' '-42- • (4) M o f f i t , F . H . - U.S.G.S.Bull.498, pp.26-27, 1912.  (28  (5) M a r t i n . G . C . & K a t z , F . J . - U.S.G.S.Bull.485,pp.30-32, 1912.  (29  Capps, i n t h e r e p o r t c i t e d , a l s o t e n t a t i v e l y c o r r e l a t e d t h e s c h i s t o f W i l l o w c r e e k w i t h t h e B i r c h Greek s c h i s t o f YukonTana na r e g i o n , n o t i n g t h e p r o b a b l e  pre-Middle  Cambrian age o f  the l a t t e r a s d e t e r m i n e d by C a i r n e s on t h e Y u k o n - A l a s k a boundary. D u r i n g t h e same y e a r M a r t i n n o t e d t h e s t r o n g resemb l a n c e o f t h e s c h i s t s and c r y s t a l l i n e l i m e s t o n e s o f t h e s o u t h w e s t e r n p a r t o f K e n a i p e n i n s u l a t o those  of the Iliamna r e g i o n  m e n t i o n e d above.$ M a r t i n , G . C . - K e n a i PenlnsuTTaT^»S.G.S.BuI1.5^7 , p.44, 1915. A g a i n , i n 1915s  (30)  E a k i n d i s c o v e r e d s c h i s t s and q u a r t -  z i t e s unconformably u n d e r l y i n g O r d o v i c i a n limestones i n the f  Cosna-Nowitna r e g i o n , A l a s k a . r e p o r t A.H. Brooks e x p r e s s e s  I n the preface to E a k i n s t h e o p i n i o n t h a t "the c o r r e l a t i o n  o f the p r e - O r d o v i c i a n metamorphic s e d i m e n t s o f t h e CosnaH o w i t n a r e g i o n w i t h t h e B i r c h creek s c h i s t s o f Yukon-Tanana r e g i o n . . . . . seems j u s t i f i e d .  ft Eakin,H.M.- Cosna-Kowitna R e g i o n , U.S.G.S.Bull.667 » p.22 and (31) • . .• . .• ' •• . • •• ' • -.. •• • • •• '. ••'., ' •• • : • .: p.5, 19 Capps, i n 1919, Kantishna  c o r r e l a t e d t h e B i r c h Creek s c h i s t o f  r e g i o n w i t h t h e B i r c h Creek s c h i s t o f Yukon-Tanana  r e g i o n and t e n t a t i v e l y w i t h the p r e - O r d o v i c i a n r o c k s o f CosnaNowitna  r  e  g  i  o  n  .  ft CappiTS.R.- K a n t i s h n a Region", U.S."£.S.Bull.68*7 ,PP*28-29 ,1919* The  \ (32) |  p o s s i b i l i t y t h a t c e r t a i n metamorphic r o c k s o f  Ruby-Kuskokwim r e g i o n might be comparable i n age t o t h e B i r c h  j  Creek s c h i s t o f Yukon-Tanana r e g i o n i s mentioned by M e r t i e and  j  H a r r i n g t o n i n a r e p o r t on t h e f o r m e r r e g i o n . ^ f Mertie,J*P«>jrT7~& H a r r i n g t o n , G . L . - U . S . G . S ^ B l i l l . 7 5 4 , 1924. On l i t h o l o g i e g r o u n d s , M e r t i e i n 1925, c o r r e l a t e d c e r t a i n p r e - S i l u r i a n q u a r t z i t e s and q u a r t z i t e s c h i s t s o f t h e C h a n d a l a r d i s t r i c t w i t h t h e B i r c h Creek s c h i s t o f Yukon-Tanana region.^ f M e r t i e , J . B . , j r . - Chandalar D i s t r i c t , U.S.G.S.Bull777T pp.224-225,'1925. I n 1930, a f t e r e x a m i n i n g the E a g l e - C i r c l e  district  ( l y i n g "between t h e Yukon-Tanana r e g i o n and t h e Yukon-Alaska b o u n d a r y ) , M e r t i e r e d e f i n e d t h e t e r m " B i r c h Creek s c h i s t " a s i n c l u d i n g " a l l t h e d e f i n i t e l y pre-Cambrian rocks o f t h i s region."# M e r t i e , J . 3 . , j r . - E a g l e - C i r c l e D i s t r i c t , "U.S.GVSVBuTl.bTF^ ;. ; ,; • . :  ••.  ; :;• • • •;-,: ; . . . • •„, ,. " •„  •  , p.14,,/1930. -  The new d e f i n i t i o n was g i v e n a more u s a b l e w o r d i n g i n a r e c e n t r e p o r t on D e n n i s o n F o r k d i s t r i c t , where t h e B i r c h Greek s c h i s t s a r e w e l l d e v e l o p e d .  M e r t i e s t a t e s : "the name  B i r c h Creek s c h i s t i s t o be r e s t r i c t e d t o t h e p r e - C a m b r i a n met amorphic r o c k s o f s e d i m e n t a r y o r i g i n . "^"^  He n o t e s t h a t  t h i s d e f i n i t i o n makes t h e t e r m B i r c h Creek s c h i s t t h e s t r i c t a n a l o g o f the term H a s i n a s e r i e s a s u s e d i n Yukon T e r r i t o r y . F o l l o w i n g t h e C a n a d i a n usage M e r t i e d e s c r i b e d t h e g r a n i t i c (£) g n e i s s e s o f t h i s r e g i o n under the name P e l l y  gneiss.  TO M e r t i e , J . B T T J r T ^ . b . G . S . B u l l 7 o 2 7 T " p ' . 1 3 (.2; Idem.- p. 14.  1931.  r  9  A f u r t h e r d i s c u s s i o n o f the c h r o n o l o g i c a l status of the Yukon group i s g i v e n i n the d i s c u s s i o n o f the age o f the T i n d i r group.  -44T i n d i r Group The  r o c k s o f the T i n d i r g r o u p a r e  typically-  developed  a l o n g the 1 4 1 s t . m e r i d i a n , n o r t h o f the Yukon r i v e r . 1 . . On h i s map o f the Y u k o n - A l a s k a "boundary, w h i c h shows a s t r i p o f c o u n t r y f i v e m i l e s w i d e e x t e n d i n g f r o m Yukon r i v e r n o r t h t o the P o r c u p i n e , D.D.  C a i r n e s shows f o u r b e l t s o f r o c k s c o l o u r e d  as the T i n d i r g r o u p ,  The  geographic  l o c a t i o n s are g i v e n as  follows: ( 1 ) L a t i t u d e 6?° 25» 20'.  1ST. ( P o r c u p i n e r i v e r ) to l a t i t u d e  67°  T h i s a r e a i s known to e x t e n d up b o t h s i d e s o f the  Porcu-  p i n e f o r s e v e r a l m i l e s and down the r i v e r f o r about 10 m i l e s . (2) L a t i t u d e 66° 45' W. (Orange c r e e k ) .  The  ( F o r t c r e e k ) t o l a t i t u d e 66°  eastward  05'  and w e s t w a r d e x t e n s i o n s o f t h i s  a r e a a r e not known. (3)  L a t i t u d e 65° 20' F. ( T i n d i r c r e e k ) t o l a t i t u d e 65°  (Harrington creek). n o t known.  The  eastward  07'  e x t e n s i o n of t h i s area i s  Westward i t e x t e n d s a e r o s s H a r d Luck c r e e k to  l o n g i t u d e 141°  JO' W.,  occupying  an a r e a o f about 200  square  miles i n Alaska. ( 4 ) A narrow b e l t E".  c r o s s e s the boundary a t l a t i t u d e 64°  45'  On the A l a s k a s i d e t h e s e r o c k s e x t e n d 3 m i l e s t o Yukon  r i v e r , where t h e y d i s a p p e a r under Quaternary T h e i r e x t e n s i o n to the s o u t h e a s t The  valley deposits.  i s unknown.  f o l l o w i n g d e s c r i p t i o n o f the two most n o r t h e r n  1. C a i r n e s , D . C . - Map  w i t h C.G.S. Mem.67.  -45-  areas (1.  and 2 . above) i s t a k e n f r o m C a i r n e s ' memoir.^  ( l ) A n a p p r o x i m a t e s e c t i o n o f the T i n d i r r o c k s as exposed on P o r c u p i n e r i v e r i s g i v e n as f o l l o w s : "Shales,  d o m i n a n t l y dark g r e y to b l a c k i n c o l o u r , c a l c a r e o u s i n p l a c e s , and p r e v a i l i n g l y s o f t , t h i n l y bedded, and f r i a b l e , w e a t h e r i n g r e a d i l y t o b l a c k mud. 1000+ f t . Q j u a r t z i t e s , "white t o g r e y i s h i n c o l o u r , t h i n l y bedded and w e a t h e r i n g r e a d i l y t o form a f i n e y e l l o w i s h sand. 1200+ f t . 1J?Q f t . B l a c k and g r e y i s h s h a l e s . . . . . . . . . . .  I n t e r c a l a t e d s o f t , g r e y i s h , t h i n l y bedded and black, f i s s i l e shales............... lj?0 f t . B r i c k - r e d c l a y s and s h a l e s 75 f t . D o l o m i t e s - s o f t , l i g h t g r e y , t h i n l y bedded, and c o n t a i n i n g t h i n i n t e r c a l a t e d c h e r t ••Lectin X 33. c l @ « o e e « e # # o » e * 6 s a « « # a a « # » e « e e * e 1^5 0 0  J_* U •  " T h i s e n t i r e g r o u p o f r o c k s has been c o n s i d e r a b l y f o l d e d , f a u l t e d , and d i s t o r t e d , so t h a t i t i s d i f f i c u l t t o estimate  the a g g r e g a t e t h i c k n e s s o f t h e beds i n s i g h t , and t h e  bottom o f t h e group was not o b s e r v e d .  I t would a p p e a r , t h e r e -  f o r e , t h a t t h i s g r o u p o f r o c k s on t h e P o r c u p i n e h a s a t h i c k n e s s o f a t l e a s t 5»000 f e e t , and may be s e v e r a l t i m e s t h i s t h i c k ness, i n places." (2)  Between F o r t and Orange c r e e k s  the r o c k s  o f the Tindir  group i n c l u d e m a i n l y s l a t e s , p h y l l i t e s , q u a r t z i t e s , s a n d s t o n e s , shales, dolomites,  and o c c a s i o n a l beds o f m a g n e s i t e .  C o n c e r n i n g t h e s t r u c t u r e and t h i c k n e s s  Cairnes  states: "Ho a c c u r a t e  estimate  c o u l d be formed as t o t h e  a g g r e g a t e t h i c k n e s s o f t h e T i n d i r beds between Orange and F o r t 1. C a i r n e s , D . D . - C.G.S. Mem.67, p p . 4 5 - 5 4 , 1914.  ^  -46-  c r e e k s , a s -these r o c k s a r e t h e r e so deformed, metamorphosed, and i n d u r a t e d , t h a t i t was d i f f i c u l t  i n most p l a c e s t o d e t e r -  mine t h e i r d i p s o r s t r i k e s o r even t h e i r r e l a t i v e s t r a t i g r a p h i e positions. at  T h i s g r o u p i s i n t h a t p o r t i o n o f t h e "belt, however,  l e a s t 6000 f e e t i n t h i c k n e s s and may be c o n s i d e r a b l y more." In  h i s d e s c r i p t i o n o f the r o c k s o f the T i n d i r group  C a i r n e s s t r e s s e s t h e pronounced c o l o u r v a r i a t i o n s w h i c h rocks d i s p l a y .  these  Bright colour contrast i s a c h a r a c t e r i s t i c  f e a t u r e o f t h e g r o u p , t h e e f f e c t b e i n g due p r o b a b l y t o t h e i r h i g h i r o n content tion.  and t o s p e c i a l c o n d i t i o n s d u r i n g t h e i r forma-  The f a c t s n o t e d ,  c o u p l e d w i t h t h e presence o f w e l l -  p r e s e r v e d r i p p l e marks i n some o f t h e q u a r t z i t e s , a r e suggestive  of continental deposition. ( 3 ) The f o l l o w i n g d e s c r i p t i o n o f t h e t h i r d a r e a a l o n g t h e  i n t e r n a t i o n a l boundary, t h a t l y i n g between T i n d i r and H a r r i n g t o n c r e e k s , i s t a k e n f r o m a r e p o r t by J.B. Mertie"*", who has r e c e n t l y s t u d i e d t h e r o c k s f r o m t h e boundary t o t h e i r w e s t e r n limit  i nAlaska.  M e r t i e ' s complete, s t r a t i g r a p h i e s e c t i o n i s  t o o d e t a i l e d t o g i v e h e r e ; t h e sequence o f t h e v a r i o u s u n i t s i s g i v e n as f o l l o w s : A. P r i n c i p a l l y t h i n - b e d d e d  limestones.  Top o f sequence.  1,700 f t . B. P r i n c i p a l l y s i l i c e o u s d o l o m i t e and s h a l e , w i t h beds o f d o l o m i t i c c o n g l o m e r a t e n e a r t h e base. 2,500 f t . C. Upper r e d b e d s , c o n s i s t i n g o f h e m a t i t i c d o l o m i t e , s h a l e , f l i n t , t u f f , and l a v a , w i t h a r e d b a s a l conglomerate. ' 2,200 t o 2,600 f t . D. A m y g d a l o i d a l and e l l i p s o i d a l l a v a s o f g r e e n s t o n e habit. 1,000+ f t . E. Thin-bedded d o l o m i t e , s h a l e , a r g i l l i t e , and q u a r t z i t e , w i t h l o c a l beds o f more massive d o l o m i t e  1. M e r t i e .J.B. , j r . - T a t o n d u k - l l a t i o n D i s t r i c t , U.S.G.S.Bull.83b, pp.369-390, 1933«  and q u a r t z i t e .  A l s o b a s i c d i k e s and s i l l s . 10,000 t o l b ,800 f t ,  P. M a s s i v e magnesian l i m e s t o n e and d o l o m i t e . .Lowest h o r i z o n thus f a r r e c o g n i z e d i n T i n d i r group. 1,000 t o G. T h i n - b e d d e d d o l o m i t e s and a r g i l l a c e o u s r o c k s not u n l i k e those o f u n i t E. A l s o c o n t a i n s a prominent h o r i z o n o f l a v a f l o w s and an equallyprominent h o r i z o n o f r e d beds. The  1,370 f t ,  r o c k s o f u n i t G appear i n p a r t t o be l i t h o l o g i -  e a l l y e q u i v a l e n t to p a r t o f u n i t E, b u t the p o s i t i o n o f t h e u n i t a s a w h o l e , i n the s t r a t i g r a p h i c sequence above, i s n o t known. The  s t r u c t u r e o f t h e s e r o c k s i s c o m p l i c a t e d by con-  s i d e r a b l e f a u l t i n g , some o f w h i c h h a s been observed and some inferred.  U n i t s A, B, a n d C, as w e l l a s t h e o v e r l y i n g M i d d l e  Cambrian, l i e i n a p l u n g i n g a n t i c l i n e , t h e a x i s o f w h i c h s t r i k e s i n a g e n e r a l s o u t h w e s t e r l y d i r e c t i o n toward t h e Yukon river.  The n o r t h e a s t e r n end o f t h i s a n t i c l i n e  i s interrupted  by a f a u l t , the g e n e r a l s t r i k e o f w h i c h appears t o be n o r t h west.  To t h e e a s t o f t h i s f a u l t S i l u r i a n l i m e s t o n e a p p e a r s t o  d i p under the a n t i c l i n e fault i sa thrust.  o f old.er r o c k s , s u g g e s t i n g t h a t t h e  U n i t s D and E, l y i n g t o the n o r t h , o c c u r  i n a m o n o c l i n a l s t r u c t u r e w i t h n o r t h e a s t e r l y and e a s t e r l y s t r i k e s and s o u t h e r l y d i p s . posure by a s t r i k e f a u l t .  These have been brought up to ex-  The r o c k s o f u n i t W s t r i k e p a r a l l e l  to u n i t s D and E b u t d i p t o t h e n o r t h ; t h e i r p o s i t i o n i s b e l i e v e d t o be due t o f a u l t i n g .  The i m p o r t a n t f e a t u r e t o note  i s , i n the w r i t e r ' s o p i n i o n , • t h a t t h e T i n d i r r o c k s have a n o r t h e a s t t o east s t r i k e which i s n o t i n keeping w i t h the g e n e r a l northwest ian.  t r e n d o f the C o r d i l l e r a a t the 141st.  merid-  -48I t s h o u l d be n o t e d here t h a t M e r t i e has i n c l u d e d w i t h u n i t G a"basal conglomerate o f angular t o subangular dolomite, greenstone,  pebbles of  and c h e r t , i n a h e m a t i t i c m a t r i x .  c o n g l o m e r a t e was mapped by Cairnes"*" as  This  "Permo-Carboniferous"  i n age because he b e l i e v e d i t t o o v e r l i e h i s Devonian-Cambrian l i m e s t o n e s , but M e r t i e has found t h i s to be a f a u l t c o n t a c t and the conglomerate i s s u c c e s s i v e l y o v e r l a i n by u n i t s C, B, and A, as w e l l as M i d d l e Cambrian b e d s , o u t s i d e t h e a r e a w h i c h C a i r n e s examined. ( 4 ) The members o f t h e f o u r t h g r o u p o f T i n d i r r o c k s , ment i o n e d a t the b e g i n n i n g o f t h i s d i s c u s s i o n , a r e d e s c r i b e d by 2  Cairnes  a s c o n s i s t i n g o f p h y l l i t e s , s l a t e s , q u a r t z i t e s , and  conglomerates.  The most prominent o f t h e s e a r e t h e p h y l l i t e s  (micaceous s l a t e s ) , but r e d and g r e e n s l a t e s , s i m i l a r t o those found between Orange and F o r t c r e e k s ( a r e a 2) a l s o o c c u r .  This  group o f r o c k s i s so much i n d u r a t e d , c o n t o r t e d , f o l d e d , and metamorphosed, t h a t C a i r n e s was n o t a b l e , i n the time a b l e , to e s t i m a t e the t h i c k n e s s o r determine  avail-  the r e l a t i v e  s t r a t i g r a p h i e p o s i t i o n o f t h e members. Age  and C o r r e l a t i o n . The  R.G. M c C o n n e l l river.  r o c k s o f the T i n d i r group were f i r s t o b s e r v e d by i n 1888 a l o n g t h e upper r a m p a r t s o f P o r c u p i n e  He t r a c e d the s e r i e s a l o n g t h e r i v e r , from about 20  m i l e s e a s t o f t h e Y u k o n - A l a s k a boundary to about 10 m i l e s west. McConnell  d e s c r i b e d these rocks as c o n s i s t i n g o f h i g h l y  -49c o l o u r e d d o l o m i t e s and s h a l e s , bedded t r a p s , o c c a s i o n a l l i g h t c o l o u r e d . s c h i s t s ,• and' q u a r t z i t e s .  He n o t e d t h a t , a t the head  o f t h e r a m p a r t s , t h e r o c k s s t r i k e n o r t h and south and d i p west. No e v i d e n c e o f t h e age was f o u n d , but M c C o n n e l l c o n s i d e r e d t h a t i t was p r o b a b l y P a l e o z o i c i F T f c G o n n e l l ,R.G.- Can.GeoTT and Nat . H i s t . S u r v . A n . R p t . ,l«bb-b9 , V 0 l . 4 , p t . J y PP.128-132, 1891. I n 1907 K i n d l e examined t h e s e c t i o n below t h e YukonA l a s k a boundary on P o r c u p i n e  river.  Ordovician f o s s i l s i n limestone  He d i s c o v e r e d M i d d l e  a l o n g t h i s p a r t o f the r i v e r  and, because n o t h i n g e q u i v a l e n t t o t h e r o c k s now known as t h e T i n d i r group o c c u r r e d i n t h e w e l l d e v e l o p e d  P a l e o z o i c sequence  above t h e O r d o v i c i a n h o r i z o n , he c o n s i d e r e d t h a t t h e T i n d i r r o c k s were p r e - O r d o v i c i a n i n age. K i n d l e e s t i m a t e d t h e t h i c k n e s s t o be 5*000 f e e t o r more.  He n o t e d t h a t t h e d i p s were  p r e v a i l i n g l y t o t h e west./..f K i n d l e ,E.M. - B u l l TGeoTTS^.Am.TVoTriQ , ppTJl5~3lirr~lTo5~. I n 1911 Maddren examined the s e c t i o n o f t h e s e n o r t h o f Porcupine  r i v e r and a l o n g - t h e . 1 4 1 s t .  rocks  meridian.  He  found the s e r i e s t o e x t e n d 6 m i l e s n o r t h o f the P o r c u p i n e where t h e y were i n t e r r u p t e d by 23 m i l e s o f g r a n i t e . N o r t h o f the g r a n i t e t h e presumably p r e - O r d o v i c i a n r o c k s o c c u r r e d i n a b e l t 8 m i l e s wide. north, o f the P o r c u p i n e  again  A g a i n , a t Ammerman mountain 67 m i l e s r i v e r , Maddren found  quartzites,  p h y l l i t e s , s l a t e s , and c r y s t a l l i n e l i m e s t o n e s , t h e whole i n t r u ded by g r a n i t e .  He c o n s i d e r e d t h e sediments to belong  pre-Ordovician series.  to the  N o r t h o f Ammerman mountain the s e r i e s  a p p e a r e d t o d i s a p p e a r u n d e r C a r b o n i f e r o u s l i m e s t o n e s , b u t 40  -50m i l e s north, q u a r t z i t e s , p h y l l i t e s , and s l a t e s a g a i n were No new e v i d e n c e obtained.#  found.  o f t h e t h i c k n e s s o r age of these r o c k s was  D u r i n g 1911 and 1912 C a i r n e s was a b l e t o  frTifeaaren Av(^  1912.  t  demonstrate t h e p r e - M i d d l e  Cambrian age of these  sediments  s o u t h o f the P o r c u p i n e t o w h i c h he gave t h e name T i n d i r group. The b e s t e v i d e n c e was o b t a i n e d a t J o n e s r i d g e , j u s t n o r t h o f H a r r i n g t o n c r e e k and w i t h i n t h e t h i r d a r e a mentioned a t t h e b e g i n n i n g o f the d e s c r i p t i o n o f t h e T i n d i r group. r i d g e C a i r n e s found t h e f o l l o w i n g c o n t a c t  A t Jones  sequencer;  limestone-dolomite h o r i z o n c o n t a i n i n g f o s s i l s o f probable M i d d l e Cambrian age. S e v e r a l hundred f e e t o f u n f o s s i l i f e r o u s l i m e s t o n e - d o l o m i t e . Unconformity. T i n d i r group. Because o f t h e marked change i n l i t h o l o g y between t h e T i n d i r and Cambrian s e d i m e n t s ,  t h e absence o f f o s s i l s i n t h e  T i n d i r g r o u p , and t h e p o s s i b i l i t y t h a t t h e i n t e r m e d i a t e l i m e s t o n e - d o l o m i t e s might be l o w e r Cambrian, C a i r n e s c o n s i d e r e d the T i n d i r group t o be p r o b a b l y ff C a i r n e s , P . P . -  Precambrian.^  C.G.S. M e t t i ib 7 V ' " p^ 7 ^ J 5 T ^ 3 T 4 .  ~  I n a r e c e n t r e p o r t M e r t i e , who has re-examined'the J o n e s r i d g e s e c t i o n , d i s p u t e s the presence  o f M i d d l e Cambrian  f o s s i l s o n t h i s r i d g e and c o n t e n d s t h a t the l i m e s t o n e s t h e r e are Upper Cambrian and O r d o v i c i a n i n age.  On t h e Tatonduk  r i v e r a few m i l e s t o t h e s o u t h , however, he f o u n d  Middle  Cambrian r o c k s w h i c h he b e l i e v e s u n d e r l i e t h e Jones r i d g e l i m e s t o n e . . U n d e r l y i n g t h e M i d d l e Cambrian r o c k s o n Tatonduk r i v e r M e r t i e found t h e upper u n i t ( u n i t A) o f h i s T i n d i r group sequence.  The c o n t a c t here a p p e a r s t o be a conformable one,  but because o f the q u i e k change  i n l i t h o l o g y and t h e absence o f  f o s s i l s i n t h e T i n d i r g r o u p , M e r t i e c o n s i d e r s t h a t a marked s t r a t i g r a p h i e h i a t u s e x i s t s and t h a t t h e T i n d i r r o c k s a r e p r o b a b l y o f A l g o n k i a n age.$ ft M e r t i e ,J.B. , j r . - U.S.G.S." BullTbTST p p . 3 9 l ° 3 9 2 , 1933. As t h e P r e c a m b r i a n s t a t u s o f t h e B i r c h Greek  '"'  "  schist  and o f t h e Yukon g r o u p depends l a r g e l y on C a i r n e s ' work on t h e boundary, i t seems opportune t o d i s c u s s t h a t p r o b l e m h e r e . Regarding the problem Cairnes s t a t e s :  ".....the w r i t e r d i d not  o b s e r v e t h e members o f t h e Yukon g r o u p i n d i r e c t c o n t a c t w i t h r o c k s t h a t c o u l d be p o s i t i v e l y i d e n t i f i e d as b e l o n g i n g t o t h e T i n d i r group.  I f t h e p h y l l i t e s , s l a t e s , and r e l a t e d r o c k s  along. Yukon r i v e r ( t h e s e b e l o n g t o l o c a l i t y 4 m e n t i o n e d a t t h e b e g i n n i n g o f t h e d e s c r i p t i o n o f the T i n d i r g r o u p , J.R.J.) prove t o b e l o n g t o t h e T i n d i r g r o u p , as t h e w r i t e r i s f a i r l y  certain  t h e y do, t h e supposed u n c o n f o r m i t y , i s e s t a b l i s h e d , as t h e s e p h y l l i t e s and a s s o c i a t e d r o c k s r e s t u n c o n f o r m a b l y on members o f the Yukon g r o u p . ft C a i r n e s , D . I ) . - C.G.S, Mem.fo?, p.57, 1914.  ~"  ~  M e r t i e , a f t e r a l o n g d i s c u s s i o n o f the s t r u c t u r e o f t h e r o c k s i n t h e l o c a l i t y o f the. " p h y l l i t e s , s l a t e s , and r e l a t e d r o c k s " m e n t i o n e d above, has come t o t h e c o n c l u s i o n t h a t b o t h t h i s g r o u p and t h e 'Yukon g r o u p ' , a s d e s c r i b e d i n t h i s v i c i n i t y , a r e P a l e o z o i c i n age, and has mapped b o t h g r o u p s here as " U n d i f f e r e n t i a t e d P a l e o z o i c " . f t f ~ l e r t i e ,J.B. , j r . - U.S.Gl^T^guTITFIb, p p . ^ 1 and 3T7~If30. The e v i d e n c e a l o n g t h e Y u k o n - A l a s k a boundary i s t h e r e f o r e open t o c o n t r o v e r s y .  ~  -52-  1 C a i r n e s , however, c o r r e l a t e d , the T i n d i r group w i t h the T a t a l i n a  group o f F a i r b a n k s q u a d r a n g l e , A l a s k a , as 2' • •  c r i b e d by P r i n d l e feldspathic  .  The T a t a l i n a  des-  group c o n s i s t s o f a s e r i e s  fragmental rocks, i n c l u d i n g  conglomerates,  of  sand-  s t o n e s , and graywaekes, i n t e r b e d d e d w i t h a r g i l l i t e s - t h a t are i n p l a c e s a l t e r e d to p h y l l i t e s .  I t a l s o c o n t a i n s some r e d s l a t e s  w h i c h a r e somewhat s i m i l a r to some o f the r e d beds o f the T i n d i r group.  Prindle  f o u n d the T a t a l i n a  group t o o v e r l i e  uneonformably the B i r c h Greek s c h i s t and to be o v e r l a i n  by  Ordovician limestones.  Regarding  Cairnes, Mertie states:  " . . . . t h i s c o r r e l a t i o n , i f made w i t h the  l o w e r p a r t o f the T a t a l i n a l o g i c a l one,  the c o r r e l a t i o n suggested  by  g r o u p , seems i n d e e d to be a v e r y  f o r the T a t a l i i a a i n c l u d e s r o c k s o f l o w e r  c i a n and p r o b a b l y o f Cambrian and pre-Oambrian  Ordovi-  age."  T. 2. PC ra i nr dn le es ,,D.D.X . M . - FC.*G.S. a i r b a n kMem«b7 s q u a d»r aP»n g5t>, e l , 1914 A l a s k a , U.S.G.S. B u l l . 525, pp«37"°39 19"i2. 3. M e r t i e , J.B. . . j r . - U.S.G.S. B u l l . 8 l 6 , pp.23-24. 1950." The P r e c a m b r i a n  age o f the T i n d i r group and a t l e a s t  p a r t o f the Yukon g r o u p ( e s p e c i a l l y the H a s i n a  s e r i e s o r the  B i r c h Creek s c h i s t ) seems t o be a f a i r l y r e a s o n a b l e i t y , i f not a c e r t a i n t y .  The  probabil-  r e l a t i o n s h i p o f the T i n d i r group  to the Yukon g r o u p , however, i s b a s e d on a r a t h e r meagre assemblage o f f a c t s . l i t e r a t u r e , admits A. The  F i e l d e v i d e n c e , as p r e s e n t e d i n the  of three  possibilities:  two g r o u p s ( a s known) may  r e p r e s e n t a more o r l e s s  con-  t i n u o u s s e r i e s , w i t h no major u n c o n f o r m i t i e s , the l o w e r p a r t of. w h i c h has s i n c e been metamorphosed and i s now B i r c h Creek s c h i s t .  T h i s does not seem v e r y  r e c o g n i z e d as the probable.  -53-  B. The two groups may r e p r e s e n t a c o n t i n u o u s  s e r i e s , w i t h no  major u n c o n f o r m i t i e s , p a r t s o f w h i c h have "been metamorphosed a l o n g zones o f a n c i e n t m o u n t a i n " b u i l d i n g . G. The two groups may be s e p a r a t e d by a major  unconformity.  T h i s would be known t o be t h e case i f t h e c o r r e l a t i o n o f t h e T i n d i r w i t h the T a t a l i n a g r o u p c o u l d be p r o v e d to be Very l i t t l e  correct.  i s known o f t h e e x t e n s i o n o f t h e T i n d i r  group f r o m the 1 4 1 s t . m e r i d i a n i n t o Yukon T e r r i t o r y .  Cock-  f i e l d , however, has d e s c r i b e d two w i d e l y s e p a r a t e d a r e a s o f r o c k s w h i c h appear t o be s i m i l a r t o t h e T i n d i r r o c k s w i t h w h i c h he has t e n t a t i v e l y c o r r e l a t e d m i l e and Upper B e a v e r R i v e r  them.  These o c c u r i n t h e Twelve-  areas.  I n the T w e l v e m i l e a r e a t h e sediments examined appeared to be d i v i s i b l e i n t o two u n i t s : Upper - E x c e e d i n g l y  t h i c k s e r i e s o f g r a y i s h q u a r t z i t e s and  black slates with i n t e r c a l a t e d Apparent  impure sandy l i m e s t o n e .  conformity,  Lower - Red and g r e e n s l a t e s , p h y l l i t e s , banded c h e r t s and quartzites,  and some 1 i m e s t o n e .  The l i t h o l o g y o f t h e l o w e r u n i t  i shighly character-  i s t i c o f the T i n d i r r o c k s , but o f t h e u p p e r u n i t  i s doubtfully  so.jf # Cockfield,W.E..  1  T w e l v e m i l e A r e a , C.G.S. Sum.Rpt. 191b , P t . B , p.-16, 1919.  I n Upper B e a v e r R i v e r d i s t r i c t two u n i t s o f sediments are d e s c r i b e d by C o c k f i e l d the T i n d i r group. A. C a l c a r e o u s  as p r o b a b l y  equivalent to parts of  These a r e :  s a n d s t o n e , s l a t e , a r g i l l i t e , and l i m e s t o n e .  -54-  B. Q u a r t z i t e , s l a t e , l i m e s t o n e , and .The  r e l a t i o n o f A t o B was  conglomerate. not found hut u n i t A  was  seen to u n c o n f o r m a b l e u n d e r l i e l i m e s t o n e s c o n t a i n i n g O r d o v i c i a n f o s s i l s . ff  C o c k f i e l d , W . E . - Upper B e a v e r R i v e r A r e a ,  1924,  C.G.S. Sum.Rpt. P t . A , pp.4-5, 1925.  The r e g i o n to the s o u t h e a s t o f Beaver r i v e r i s known o n l y f r o m a few r a p i d r o u t e - s u r v e y s .  K e e l e , i n h i s r e p o r t on  the M a c k e n z i e mountains m e n t i o n s a s e c t i o n on Ross r i v e r , below l e w e s l a k e , w h i c h shows "a r e m a r k a b l y  complex s e r i e s o f  c l o s e l y f o l d e d r o c k s , w i t h r a p i d a l t e r n a t i o n i n bedding composition.  These c o n s i s t o f r e d , g r e e n and g r e y s l a t e s , o r  a r g i l l i t e s , c h e r t , q u a r t z i t e , l i m e s t o n e , sandstone, volcanic  and  grits,  and  tuffs." S i m i l a r r o c k s were found on o t h e r r i v e r s i n e a r l i e r  surveys.  Regarding "The  these l o c a l i t i e s Keele  states:  s t r o n g r e d c o l o u r o f some o f the s l a t e s , and  r a t h e r remarkable  q u a r t z g r i t s , have s e r v e d to i d e n t i f y  group of r o c k s a t the f o l l o w i n g w i d e l y s e p a r a t e d  this  localities:  the P e l l y r i v e r , i n the v i c i n i t y o f Wolf canon; the r i v e r , n e a r R u s s e l l c r e e k ; and the S t e w a r t  the  Macmillan  r i v e r at Tasin  mountains."/ f Keele.Joseph  - Mackenzie Mountains,  Although Keele  C.G.S. R p t . N o . 1 0 9 7 , p.34, 1910.  c o n s i d e r e d the r e d s l a t e group o f  Ross r i v e r to be S i l u r i a n i n age because i t a p p a r e n t l y o v e r l a y a g r e y a r g i l l i t e group c o n t a i n i n g O r d o v i c i a n f o s s i l s , p r o b a b i l i t y e x i s t s t h a t t h i s s u c c e s s i o n may the r o c k s o f the s l a t e g r o u p may  the  be r e v e r s e d  be c o r r e l a t i v e w i t h the  and  T i n d i r group.  Gn the M a c s i l l l a n r i v e r t h e r e d s l a t e group  a p p a r e n t l y l i e s beneath r o c k s c o r r e s p o n d i n g argillites.  to the O r d o v i c i a n  As t h e p o s s i b i l i t y e x i s t s , however, t h a t the r e d  s l a t e s and a s s o c i a t e d r o c k s may  be P a l e o z o i c , o r even  Mesozoic,  t h e i r c o r r e l a t i o n w i t h the T i n d i r r o c k s o f the Yukon-Alaska boundary i s o f f e r e d m e r e l y as a s u g g e s t i o n based e n t i r e l y  on  lithological similarity. On the G r a v e l r i v e r , j u s t below the mouth o f H a t l a r i v e r , K e e l e has r e p o r t e d the f o l l o w i n g descending  section, given i n  order: 1,100  Brown micaceous sandy s l a t e s Coarsely laminated hematite Dolomite  and s i l i c e o u s slate..........  and a r g i l l i t e  feet. . " "  100 1,000  These r o c k s d i p southwest and appear t o p a s s under a group comp o s e d o f p u r p l e and g r e e n i s h a r g i l l i t e Upper Cambrian l i m e s t o n e .  The  o v e r l a i n by M i d d l e  l a t t e r group d i p s  A l t h o u g h K e e l e does hot m e n t i o n an u n c o n f o r m i t y , d i p s suggest  one.  Regardless  southeast. the  of t h i s p o s s i b i l i t y the  group i s , from the d e s c r i p t i o n ,  or  recorded lower  l i t h o l o g i c a l l y and s t r a t i g r a -  p h i c a l l y s i m i l a r t o t h e T i n d i r group o f the Y u k o n - A l a s k a boundary,# it K e e l e , J o s e p h - R p t .  In Hdrthwestern sedimentary Range and correlated  A l a s k a ^ p a r t s of a great s e r i e s  of  r o c k s , l y i n g a l o n g the s o u t h s i d e of the Brooks  c o n s i d e r e d to be p r e - S i l u r i a n i n age, have been w i t h the Home g r o u p  2  1. Smith,P.S. & M e r t i e , J . B . , j r * 2.  (1°)  c i t e d , pp»36~37»  o f Seward P e n i n s u l a ; w i t h t h e U.SvG.S.Bull.813 pp.l23~124,  M o f f i t , F . H . - U.S.G.S.Bull.533, p . 2 6 ,  s  1915-  1930.  C ) 11  (12)  »5bpre-Ordovician quartzites,  s h a l e s , and l i m e s t o n e s o f P o r c u p i n e  r i v e r ; and t h e T a t a l i n a g r o u p o f t h e Yukon-Tanana 2-  region,  Cairnes* , i n h i s c o r r e l a t i o n o f t h e T i n d i r  rocks,  mentioned t h e i r resemblance t o the 'Belt Terrane' o f B r i t i s h 2  Columbia  and t h e w e s t e r n U n i t e d S t a t e s .  Made i n g e n e r a l 3  t e r m s , t h i s c o r r e l a t i o n seems e x p e d i e n t a s more r e c e n t work has  shown t h a t  there i s s t r a t i g r a p h i c as w e l l as l i t h o l o g i e  s i m i l a r i t y between t h e B e l t i a n  s e r i e s and T i n d i r group.  The  g r e a t d i s t a n c e s e p a r a t i n g t h e two l o c a l i t i e s , however, p e r m i t s of 1. 2. 3.  n o t h i n g more t h a n a v e r y g e n e r a l c o r r e l a t i o n . C a i r n e s , D . D . - C.G.S. Mem.b7, up.56-57, 1914, Daly,R.A.- C.G.S. Mem.38, pp.179-191, 1912. S c h o f i e l d , S . J . - C.G.S. Mem.76, pp.22-52. 1915. - C.G.S. B u l l . 3 5 . 1922.  ~  "  CHAPTER I I I . THE PALEOZOIC  -57PALEOZOIC CAMBRIAN SYSTEM. Lower Cambrian. The Lower Cambrian has not been i d e n t i f i e d by fossils  i n Yukon o r A l a s k a .  M i d d l e and Upper Cambrian. Rocks d e f i n i t e l y o f M i d d l e and Upper Cambrian age a r e known i n Yukon and A l a s k a o n l y i n t h e O g i l v i e mountains a t the vicinity  o f the 1 4 1 s t .  meridian.  The most d e t a i l e d i n f o r m a t i o n o f t h e s e r o c k s i s T  1  g i v e n i n J.B. M e r t i e s r e p o r t on the Tatonduk-Nat i o n d i s t r i c t . " " M e r t i e has d i v i d e d the Cambrian o f t h i s d i s t r i c t following  i n t o the  sequence:  "1. Upper Cambrian l i m e s t o n e , w h i c h g r a d e s upward w i t h o u t any n o t i c e a b l e s t r a t i g r a p h i c o r l i t h o l o g i e break i n t o O r d o v i c i a n limestone."  2000 f e e t e s t i m a t e d .  " 2 . Upper p l a t e o f M i d d l e Cambrian l i m e s t o n e . "  300 f e e t .  ,'-"3» A t h i n f o r m a t i o n o f s l a t e and q u a r t z It e', a l s o o f M i d d l e Cambrian age."  3°0 f e e t .  "4. Lower p l a t e o f M i d d l e Cambrian l i m e s t o n e . "  B e l i e v e d to be  600 t o 800 f e e t t h i c k . The Cambrian r o c k s l i e i n s y n c l i n a l and a n t i c l i n a l s t r u c t u r e s w h i c h a r e c o m p l i c a t e d by f a u l t i n g .  The M i d d l e Cam-  b r i a n beds conform t o t h e upper p a r t o f t h e T i n d i r group and lie  i n an a n t i c l i n e w h i c h p l u n g e s southwestward from the  •:~58- .  .  Tatonduk r i v e r , n e a r the Y u k o n - A l a s k a boundary, t o the Yukon river. and  T h i s a n t i c l i n e i s t e r m i n a t e d on the e a s t ,  southwest,  by f a u l t s .  northwest,  A. few m i l e s to the s o u t h e a s t o f the  a n t i c l i n e Upper Cambrian l i m e s t o n e o u t c r o p s i n a s t r u c t u r e around the head of Shade c r e e k .  complicated  N o r t h o f the  anti-  c l i n e , a t J o n e s r i d g e on the i n t e r n a t i o n a l boundary, the Upper Cambrian and O r d o v i c i a n l i m e s t o n e s o c c u r i n an ing  eastward-plung-  s y n c l i n e f r o m w h i c h the Lower Cambrian members have been  removed i n a g r e a t f a u l t d i s p l a c e m e n t .  Mertie believes that  the Cambrian s e c t i o n n e a r the 1 4 1 s t . m e r i d i a n r e p r e s e n t s the w e s t e r n end  o f a g r e a t s t r u c t u r e o f a n t i c l i n e s and s y n c l i n e s  w h i c h s t r i k e N. Age  and  80° E. i n t o Yukon T e r r i t o r y .  Correlation. On h i s map  and P o r c u p i n e  o f the Y u k o n - A l a s k a boundary between Yukon  r i v e r s C a i r n e s ^ d i d n o t d i f f e r e n t i a t e the Cam-  :  b r i a n as a c a r t o g r a p h i c u n i t , but grouped i t w i t h O r d o v i c i a n , S i l u r i a n , and  Devonian r o c k s shown as e x t e n d i n g  intermittently  f r o m n e a r Yukon r i v e r to j u s t n o r t h o f Tatonduk r i v e r .  Another  mapping u n i t shows D e v o n i a n , S i l u r i a n , O r d o v i c i a n , and p o s s i b l y Cambrian r o c k s , w h i c h o c c u r a t i n t e r v a l s as f a r n o r t h as P o r c u pine r i v e r .  The  p o s s i b i l i t y e x i s t s t h a t Cambrian exposures  o c c u r a c o n s i d e r a b l e d i s t a n c e n o r t h o f Tatonduk r i v e r , C a i r n e s ' f o s s i l l o c a l i t i e s a l l l i e i n the c e n t r a l and p a r t o f the O g i l v i e The  may  but southern  range.  following l i s t i n g  o f t h r e e Upper Cambrian  c o l l e c t i o n s , t a k e n by C a i r n e s and determined  by L.D.  -  Burling,  i s b e l i e v e d t o be r e p r e s e n t a t i v e o f t h e f a u n a ,  1  The l o c a l i t i e s  •?  are p u b l i s h e d i n M e r t i e ' s r e p o r t . " 140° 5 8 » W. , 6 4 ° 5 6 ' IT. N o r t h o f Shade c r e e k and s o u t h o f Tatonduk  B.  river. Obolus s p .  P t y c h o p a r i a sp.  A c r o t r e t a sp.  Anomoeare s p .  Agraulus sp.  S o l e n o p l e u r a sp,  141° 00' W.,  65° 04' 1.  South o f H a r d l u c k c r e e k .  Obolus ( W e s t o n i a ) c f . stoneanus (Whitfield.) . lingulella  Sehizambon c f , t y p i c a l i s W a l c o t t . Undetermined t r i lobite.  sp.  Aero t h e l e c f . o o r iaeea linnarsson. C.  141° 0 0 ' W,,  65° 0 6 ' N.  Jones Ridge.  F o r a m i n i f e r a ? undetermined.  A c r o t r e t a sp.  Obolus 2 sp.  Orthoid.  Obolus ( W e s t o n i a ) c f , stoneanus (Whitfield).  Coral ?  lingulella  Ostracod.  2 sp.  D i c e l l o m u s ? sp.  Agnostus s p .  C u r t i c i a ? sp.  D u r y c a r e ? sp.  A c r o t h e l e c f . coriacea linnarsson.  3 unidentified  trilobites.  1. C a i r n e s , ! ) . ! . - C.G.S. Mem.67, p p . 6 3 - 6 4 , 1914. 2. M e r t i e , J . B . , j r . - O p . c i t . , p . 3 9 9 . " l e t t e r s p l a c e d a t the f r o n t o f each l o c a l i t y a r e p l o t t e d on t h e a t t a c h e d diagrams o f A l a s k a and Yukon t o show the geographic p o s i t i o n s .  -60-  The  f o l l o w i n g a r e two M i d d l e Cambrian c o l l e c t i o n s by  J.B. M e r t i e . ^  D.  141° 10' W.,  64° 5 8  above E a g l e .  f  N.  Northeast  s i d e o f Yukon r i v e r  D e t e r m i n e d by C.E. R e s s e r .  This i s the  o l d e s t Cambrian h o r i z o n r e c o g n i z e d . l i s u s i a o r Jamesella sp. Dorypyge 2 s p . Albertella E.  141° 0 5 ' W.,  rugosa.  "Ptychoparia" 2 sp.  mertieii(MSS.)  64° 58' N.  Stenotheca  Ogygopsis s p .  About 5 m i l e s east o f D.  D e t e r m i n e d by E. K i r k . Archaeocyathus sp.  Ethmophyllum sp,  "Cocinoptycha" sp.  F o s s i l s f r o m Seward P e n i n s u l a , w h i c h were once a s s i g n e d t o t h e Upper C a m b r i a n , a r e now r e g a r d e d by K i r k t o be 2 lower O r d o v i c i a n . The  n e a r e s t Cambrian l o c a l i t y t o t h e Yukon-Tatonduk  a r e a i s a t t h e j u n c t i o n o f the K a t l a w i t h t h e G r a v e l  river.  5  The  s e c t i o n as g i v e n by K e e l e  i s about 4,000 f e e t t h i c k :  limestone c o n t a i n i n g brachiopods. Calcareous  sandstone.  Dolomites. P u r p l e and g r e e n i s h  argillites.  1. M e r t i e , J . B . , j r . - U.S.G.S.Bull.836, p . 5 ? 8 , 1933. 2. K i r k , Edwin- U.S.G.S.Bull.733, p.24, 1922. • 3. K e e l e , J o s e p h - P e l l y , R o s s , and G r a v e l R i v e r s , C.G.S. R p t . 1097, p.36, 1910.  Fig.  7.  Cambrian  (brown), Ordovician  f o s s i l l o c a l i t i e s o f Yukon.  (red),  and S i l u r i a n  The l e t t e r s a r e t h e  same a s t h o s e g i v e n a t the. head o f t h e g e o g r a p h i c l o c a t i o n s i n the t e x t .  . 8.  O r d o v i c i a n ( r e d ) and S i l u r i a n ( b l u e )  Fig localities  of Alaska.  fossil  (blue)  -61-  .  127° 57' W.,  63° 3 6 ' F.  The b r a c h i o p o d s  taken from the  l i m e s t o n e a t the t o p o f the s e c t i o n were considered, by Schu.chert  t o be the s p e c i e s ' B i l l i n g s e l l a  Goloradoensis  Shumard'; t h e f o r m ' E o - o r t h i s d e s m o p l e u r a , Meek, sp.* w also  identified.  Schuchert  T h i s fauna was c o n s i d e r e d by Ami and  to be M i d d l e  o r Upper Cambrian.  ORDOVICIAN SYSTEM. U n l i k e t h e Cambrian, the O r d o v i c i a n r o c k s a r e w i d e s p r e a d i n i n t e r i o r A l a s k a and the e a s t e r n p a r t o f Yukon T e r r i tory.  I n Yukon the O r d o v i c i a n has been f o u n d , i n the O g i l v i e  mountains a t the i n t e r n a t i o n a l boundary, on Upper B e a v e r r i v e r , and on Ross r i v e r . A. O g i l v i e mountains a t the i n t e r n a t i o n a l boundary. As a l r e a d y n o t e d C a i r n e s mapped t h e 'Cambrian t o Devonian' r o c k s o f t h e boundary a s two u n d i f f e r e n t i a t e d one  groups,  o f w h i c h e x t e n d s f r o m n e a r Yukon r i v e r t o j u s t n o r t h o f t h e  Tatonduk, t h e o t h e r f r o m C a t h e d r a l ereek n o r t h t o t h e P o r c u p i n e river.  C a i r n e s ' O r d o v i c i a n f o s s i l s were f o u n d i n t h e s o u t h e r n  s e c t i o n and w i t h i n the O g i l v i e m o u n t a i n s . Two l i t h o l o g i c t y p e s have been r e c o g n i z e d section.  i n this  A t J o n e s r i d g e , the O r d o v i c i a n h o r i z o n i s , l i k e t h e  Upper Cambrian l i m e s t o n e s i l i c e o u s limestone.  i n t o which i t g r a d e s , a massive  At t h e head o f Shade c r e e k the O r d o v i c i a n  -62h o r i z o n c o n s i s t s of dark-grey s l a t e s and  cherts.  Although  to b l a c k , thin-bedded,  siliceous  the l i t h o l o g y o f the Shade c r e e k  r o c k s i s m a r k e d l y d i f f e r e n t to t h a t o f Jones r i d g e , t h e  fossil  e v i d e n c e i n d i c a t e s t h a t the O r d o v i c i a n h o r i z o n i s about c o n temporaneous a t b o t h l o c a l i t i e s , so t h a t c o n d i t i o n s o f sedimentation  were c o n s i d e r a b l y d i f f e r e n t a c r o s s a d i s t a n c e of  about 10 m i l e s . a t each  The  f o l l o w i n g i s a l i s t i n g of f o s s i l s  found  locality.  A - l . 141°  011  65° 06'  W„,  T h i s c o l l e c t i o n was  „.  South s i d e o f J o n e s Ridge,  made by  J.B.'  M e r t i e and d e t e r m i n e d by  Edwin K i r k . Middle Streptelasma Halysites  sp.  sp.  Zygospira  sp.  Syntrophia  sp.  The M i d d l e  sp.  E o h a r p e s sp. lower  sp•  Illaenus  sp.  Bumastus sp.  sp.  Dalmanella  sp.  Sowerbyella  sp.  Christiania  sp<  Rhynchotrema sp.  sp.  leptelloides  C a t a z y g a sp.  lingula  sp.  Dalmanella  |  Platystrophia  Strophomena s p . Dinorthis  Ordovician.  Ordovician.  O r d o v i c i a n f a u n a abov e i s c o n s i d e r e d by K i r k to be a p p r o x i m a t e l y Trent on o r u p p e r Mohawkian, but he  -63-  does n o t c o n s i d e r i t e q u i v a l e n t t o any o t h e r O r d o v i c i a n known i n A l a s k a o r n o r t h e r n N o r t h A-2.  ?  141° 0 0 ' W., 64° 5 5 N.  fauna  America.  Head o f Shade  creek.  T h i s c o l l e c t i o n was made by D.D. C a i r n e s ; t h e g r a p t o l i t e s were examined by R. Ruedemann, t h e o t h e r i n v e r t e b r a t e s by l.D. B u r l i n g . Dicranograptus ramosus H a l l .  c f . D.  Ostracode.  j  P t y c h o p a r i a sp.  Retiograptus geinitzianus \ Hall •  I s o t e l u s ? sp.  Diplograptus foliaceus incisus lapworth.  Harpes ? s p .  Obolus sp,  The  g r a p t o l i t e s h e r e were r e f e r r e d t o t h e Normanski11  o r l o w e r O r d o v i c i a n , the u p p e r p a r t o f w h i c h Ruedemann c o n s i d e r s t o be o f e a r l y B l a c k R i v e r , w h i c h i s commonly 2 • c l a s s e d as M i d d l e O r d o v i c i a n .  The o t h e r i n v e r t e b r a t e s  were d e t e r m i n e d t o be O r d o v i c i a n . B. O g i l v i e mountains a t Upper Beaver r i v e r . The  O r d o v i c i a n was i d e n t i f i e d i n t h i s d i s t r i c t by  f o s s i l s t a k e n from a n u n d i f f e r e n t i a t e d group o f massive-bedded, i n part shaly limestones. r i a n and Devonian f o s s i l s .  These l i m e s t o n e s a l s o c o n t a i n  Silu-  The group l i e s i n an a n t i c l i n e ,  s t r i k i n g a l i t t l e n o r t h o f west and u n c o n f o r m a b l y o v e r l y i n g p a r t o f t h e beds o f the T i n d i r ( ? ) group.  No d e f i n i t e b r e a k was  r e c o g n i z e d between t h e O r d o v i c i a n o r S i l u r i a n . 1. Cairnes,D.D.- C.G.S. Mem.6?, p.66. 2. M e r t i e , J . B . , . j r . - O p . c i t . , p.48.  ~  The Devonian  -64a p p e a r e d t o be r e s t r i c t e d t o one s m a l l l o c a l i t y , The l i s t e d here.  1  f o s s i l s assigned, d e f i n i t e l y t o t h e O r d o v i c i a n a r Several l o t s are considered ' S i l u r i a n or Ordovi-  c i a n ' or ' S i l u r i a n and O r d o v i c i a n ' .  The g e n e r a l l o c a l i t y i s o:  the n o r t h e r n l i m b o f the a n t i c l i n e m e n t i o n e d above, and i s given only B.  approximately.  135° 3 0  1  W.,  64° 30* N.  North of Carpenter  T h i s c o l l e c t i o n was made by W.E.  creek.  C o c k f i e l d and  determined  by E.M. K i n d l e . ~ Ordovician, Columnaria  alveolata.  Zaphrentis ? sp.  E r i d o p h y l l u m c f . rugosum. H a l y s i t e s n. s p .  The H a l y s i t e s above i s c o n s i d e r e d t o be i d e n t i c a l w i t h a new Richmond s p e c i e s o r v a r i e t y i n t h e Lake Windermere district of British The  Columbia.  f o l l o w i n g g r a p t o l i t e s o f the same c o l l e c t i o n a r e con-  s i d e r e d by Ruedemann t o be l a t e N o r m a n s k i l l i n age and s u g g e s t i v e o f t h e f a u n a d e s c r i b e d by L a p w o r t h f r o m Dease 3  river. Didymograptus s p . two f o r m s , Dicranograptus  fragments.  s p . n o v . c f . ramosus H a l l .  C l i r a a c o g r a p t u s c f . a n t i q u u s group. Glyptograptus  1. C o c k f i e l d . W . E . -  c f . t e r e t i u s e u l u s euglyphus(lapworth) .  Upper B e a v e r R i v e r , C.G.S. Sum.Rpt.1924,  2. C o c k f i e l d , W . E . - O p . c i t . , p p . 6 - 7 , ' " ' 3. Dawson,G.M.- G e o l . and N a t . H i s t . S u r v . o f Canada, 1887-88 P  Vol.Ill,  t  ,  A  >  p t . B , p.94, I889.  P P  6  7  -65-  C. Ross r i v e r i n the S e l w y n m o u n t a i n s . A s m a l l c o l l e c t i o n o f g r a p t o l i t e s was  obtained  Keele from black i n d u r a t e d shale interbedded with a r g i l l i t e s and 150°  50  r  by  cherty  c h e r t s i n the S e l w y n m o u n t a i n s o f Ross r i v e r . W. , 62° 4 ? '  IT.  On Ross r i v e r , 7 m i l e s below  • '  John l a k e .  R e f e r r e d by Ami  Orthograptus  to the  Ordovician.  1  quadrimucronatus, H a l l .  leptograptus flaccidus, H a l l . Orthograptus  or Glossograptus,  sp.  Correlations. The  f o l l o w i n g d e a l s m a i n l y w i t h the O r d o v i c i a n i n  A l a s k a , but m e n t i o n s h o u l d be made here of an O r d o v i c i a n h o r i zon f o u n d by K e e l e  i n the MacKensie mountains j u s t e a s t  of  2  Yukon T e r r i t o r y .  The  s e c t i o n , c o n s i d e r e d by K e e l e t o  be  O r d o v i c i a n , l i e s a l o n g the n o r t h s i d e o f G r a v e l r i v e r below the mouth o f T w i t y a r i v e r and  i s composed o f 4000 f e e t  a l t e r n a t i n g beds of a r g i l l i t e , d o l o m i t e , and o f d i a b a s e 100  f e e t t h i c k , and an upper 1,500  of  limestone, a  sill  f e e t o f sand-  stone « D.  127°  56'  W.,  64° 18' N.  m i l e s n o r t h of Eidhe The  East  side of Gravel r i v e r a  creek.  cephalopod found here,  S t o k e s ' , was  few  c o n s i d e r e d by Ami  'Actinoceras B i g s b y i , t o be c h a r a c t e r i s t i c  the B l a c k R i v e r ( H i g h l o w e r O r d o v i c i a n )  of  of e a s t e r n  Canada. 1. K e e l e . J . - P e l l y , R o s s , and 4. Idem.- pp.37-38.  G r a v e l r i v e r s , C.G.S.Rpt.1097 p  ^ ' 8  -66-  I n f o r m a t i o n r e g a r d i n g the O r d o v i c i a n o f A l a s k a i s t o o e x t e n s i v e t o he g i v e n h e r e i n d e t a i l , h u t most o f the l o c a l i t i e s are l i s t e d and t h e main f e a t u r e s d e s c r i b e d .  Lower O r d o v i c i a n . E.  Lower O r d o v i c i a n f o s s i l s have been found  i n Alaska  n e a r the Y u k o n - A l a s k a boundary ( a l r e a d y d i s c u s s e d ) and i n 3  Seward Peninsula." "  The f o s s i l s o f Seward P e n i n s u l a o c c u r i n  the P o r t C l a r e n c e l i m e s t o n e ( O r d o v i c i a n and S i l u r i a n ) w h i c h has been mapped w i t h some M i s s i s s i p p i a n l i m e s t o n e as an u n d i f f e r e n t i a t e d group.  The l i m e s t o n e o v e r l i e s  s l a t e i n apparent t r a n s i t i o n a l to  pre-Ordovician  conformity which i s d i f f i c u . l t  e x p l a i n because the s l a t e i s i n t r u d e d by b a s a l t and gabbro  to w i t h i n a few f e e t o f t h e l i m e s t o n e beds s u g g e s t i n g unconformity.  an  The f o s s i l s f r o m t h e f o l l o w i n g l o c a l i t i e s were  c l a s s e d by K i r k as Lower O r d o v i c i a n (Beekmantown). E - l . 167° 0 5' W.,  65° 23' N.  Vicinity  65° 27' K.  E a s t bank o f C a l i f o r n i a  o f t h e mouth o f L o s t  river. E-2.  166° 33  T  W.,  Middle P. P o r c u p i n e  river.  river.  Ordovician.  Two l o c a l i t i e s of O r d o v i c i a n f o s s i l s were  found by E.M. K i n d l e ^ a l o n g t h e l o w e r r a m p a r t s o f P o r c u p i n e river.  These o c c u r i n h a r d b l u i s h g r e y l i m e s t o n e w i t h  s i o n a l o o l i t i c bands.  occa-  The s t r a t i g r a p h i e r e l a t i o n s w i t h the  u n d e r l y i n g r o c k s and the o v e r l y i n g S i l u r i a n were n o t  determined.  1. S t e i d t m a n n , E . & C a t h c a r t , S . H . - U.S.G.S.Bull.733, p.24, 1922. d. K i n d l e , E . M . - B u l l . G e o l . S o c . A m e r . , V o l . 1 ? , pp.322-324, 1908.  -67F - l . 143° 10' ¥. , 67° 00' IT. above an i n d i a n v i l l a g e  North side Porcupine, i n the lower ramparts.  miles The  f o s s i l s h e r e were p l a c e d b y U l r i c h i n t h e M i d d l e Ordovician F-2.  (Mohawkian).  142° 59» W. , 67° 00» 1\.  South s i d e o f P o r c u p i n e , about 6  T  m i l e s above t h e i n d i a n v i l l a g e .  The f a u n a here was conr  s i d e r e d t o be O r d o v i c i a n .  The p r e s e n c e o f M a c l u r i n a  manitobensis Whiteaves' suggests c o r r e l a t i o n w i t h l i m e s t o n e i n Seward P e n i n s u l a c o n t a i n i n g t h e same s p e c i e s . The l a t t e r i s c o n s i d e r e d t o be Upper O r d o v i c i a n i n Seward Peninsula.  Upper O r d o v i c i a n . 1 G.  Upper O r d o v i c i a n f o s s i l s we re f o u n d by E ale i n  i n the  v a l l e y o f Sulukna r i v e r ,  some 50 m i l e s west o f l a k e Mulehumina.  The a p p r o x i m a t e l o e a l i t y  i s 154° W. , 64° N.  Columnaria a l n e o l a t a  J  Halysites gracilis  Hall.  Goldfuss var. C r i n o i d columnals. These f o s s i l s were t a k e n from l i m e s t o n e s . H.  F o s s i l s c l a s s i f i e d a s Richmond i n age were f o u n d by  J.S. Brown i n t h e N i x o n F o r k c o u n t r y n e a r t h e head o f t h e 2  N o r t h F o r k o f Kuskokwim 154° 1 5  f  W.,  river.  63° 2 8 ' N.  utary of Nixon Fork).  P  Head o f W h i r l w i n d c r e e k ( a t r i b The f o l l o w i n g f a u n a i s O r d o v i c i a n .  " B a k i n ^ S . - U.S.G.S. B u l i . b b ' / , p.25, IjmT 2. Brown,J.S.- U.S.G.S. B u l l . 7 8 3 , p.104, 1?26.  •68-  (Richmond) a c c o r d i n g t o K i r k . Paleophyllum sp.  P a l e o f a v o s i t e s sp.  H a l y s i t e s sp.  Galapoecia canadensis B i l l i n g s .  l i o s p i r a sp,  Columnaria sp.  Hormotoma s p .  I l l a e n u s sp. Stromatopora sp.  The above f a u n a was t a k e n f r o m h e a v i l y bedded b l u e - g r e y limestone.  I.  I n t h e A l a s k a Range, n e a r t h e s o u r c e o f Kuskokwim 1  r i v e r , Brooks and P r i n d l e  f o u n d f o s s i l s b e l i e v e d to have come  f r o m a h o r i z o n o f b l u e l i m e s t o n e and carbonaceous 153° 3 0 ' W. , 62° 30* IT. ( a p p r o x . ) .  slate.  T h i s f a u n a was con-  s i d e r e d by S c h u c h e r t t o be Upper O r d o v i c i a n ( U t i c a ) . Glimacograptus b i c o r n i s  (Hall).  C l i m a c o g r a p t u s s p . undet. D i c r a n o g r a p t u s c f . ramosus ( H a l l ) . A few f r a g m e n t a r y r e m a i n s found 20 m i l e s t o the s o u t h were s u g g e s t i v e o f a M i d d l e O r d o v i c i a n h o r i z o n .  SILURIAN SYSTEM. The S i l u r i a n i s n o t w e l l known i n Yukon, so t h e d i s c u s s i o n o f t h i s p e r i o d w i l l be b r i e f .  Two l o c a l i t i e s a r e  known i n the O g i l v i e m o u n t a i n s , one a t t h e i n t e r n a t i o n a l 1. Brooks,A.H.  & P r i n d l e , L . M . - uTs.G.S.Prof.Pap.70, p.72,  1?11.  -69-  boundary and one a l o n g Upper B e a v e r r i v e r .  Silurian  fossils  have a l s o been found i n the' K e e l e mountains a l o n g t h e i n t e r n a t i o n a l boundary. I n t e r n a t i o n a l boundary s e c t i o n . The  C a m b r i a n - S i l u r i a n sequence a l o n g t h e 1 4 1 s t .  meri-  d i a n a p p e a r s , f r o m t h e p u b l i s h e d d e s c r i p t i o n s , t o be conforma b l e t h r o u g h o u t and made up l a r g e l y o f somewhat d o l o m i t i c l i m e s t o n e w i t h o c c a s i o n a l s h a l y beds. D.D. C a i r n e s c o l l e c t e d S i l u r i a n f o s s i l s from numerous l o c a l i t i e s a l o n g t h e boundary both i n t h e K e e l e and the O g i l v i e mountains.  The f o l l o w i n g l i s t  i s b e l i e v e d t o be r e p r e s e n t a t i v e  o f t h e d i s t r i b u t i o n and f a u n a • ^ A.  140° 56* W.,  67° 14* H.  T h i s fauna  i s c o n s i d e r e d by K i n d l e  t o be e a r l y S i l u r i a n . Streptelasma sp.  Halysites catenulatus Linn.  Cladopora sp.  Trematospira  c f . camura H a l l ,  Bronteus sp. B.  141  0 0 ' W.,  Silurian.  67° 2 0 ' H.  R e f e r r e d by K i n d l e t o the middle  F i v e m i l e s south o f Porcupine  river.  Favosites cf. n i a garensis H a l l .  Camarotoechia c f . n e g l e c t a Hall,  Conchidium s p . undet.  Conchidium c f . g r e e n e i H a l l and C l a r k e .  1. C a i r n e s , C . G . S . M e m . V / , pp.66-67. The l o c a l i t i e s were f o u n d f r o m a k e y g i v e n i n U.S.G.S. B u l l . 8 l 6 , p.47.  -70-  140° 59' W.,  65° 06'  K.  Near H a r r i n g t o n c r e e k .  Middl«  Silurian. Stropheodonta sp.  Dalmanella c f . elegantula (Dalman) .  Orthis f l a b e l l i t e s Foerste.  S p i r i f e r r a d i a t u s Sowerby.  M e r i s t i n a sp.  Sphaerexochus r o m i n g e r i H a l l ,  S p i r i f e r sp.  I l l a e n u s c f . imperator H a l l .  B r o n t i o p s i s sp. D.  141° 00' W.,  67° 0 1 ' N.  Hear Salmon T r o u t  river.  late  Silurian.  E,  Meristella  s p . undet.  leperditia  s p . undet.  141° 0 0 ' W.,  66° 1 7 ' H. ( a p p r o x . ) .  Provisionally  referred  to t h e l a t e S i l u r i a n by K i n d l e . Stropheodonta, Meristella  s m a l l sp.  M a r t i n i a sp.  sp.  l e p e r d i t i a sp.  R e t z i a ? sp. 0  F.  141  I s o c h i l i n a sp.  0  0J5 W. , 6.5 06' H, f  H a r r i n g t o n creek.  Probably  late  Silurian. Whitfieldella  sp.  Atrypa r e t i c u l a r i s Upper B e a v e r  linn.  river.  The S i l u r i a n  f o s s i l s c o l l e c t e d by W.E.  from t h e O g i l v i e mountains a l o n g Beaver by E.M. K i n d l e and a r e l i s t e d below. 1.  Cockfield"  r i v e r we r e  determined  These f o s s i l s came from  0 o c k f i e l d . W . E . - C.U.S.Sum.Rpt. 1924, P t . A , p . b , 1925.'  =71of 0 r do v i e i an - S i 1 u r i an l i m e s t o n e mentioned under  the a n t i c l i n e  " O r d o v i c i a n System". 0.  135°  30  I . , 64° 30'  ?  N.  of Carpenter creek. Bryozoa  Northern limb of a n t i c l i n e , north  Silurian.  (undet.).  Cladopora  Megalomus c f . c a n a d e n s i s .  cf. cervicornis.  Orthis f l a b e l l i t e s . Whitfieldella  H.  135°  20'  25  W. , 64°  creek.  f  N.  nitida.  Betwe en B e a v e r r i v e r and  Carpenter  Silurian. Favosites c f . favosus. Stromatopora  c f . antiquua.  Correlations. -Along G r a v e l r i v e r , e a s t o f Mt. Sekwi and west o f N a t l a r i v e r , Keele found S i l u r i a n  fossils.  These were d e t e r -  mined by lambe, P a r k s , and S c h u c h e r t , and the h o r i z o n i s  1 i n d i c a t e d on the map T X .  128°  15'  river.  as Upper  W. , 63° 3 5 The  r  Silurian  N.  Silurian.  M a c k e n z i e mountains west o f N a t l a  s e c t i o n i s d e s c r i b e d as composed o f  2,000 f e e t o f r a t h e r pure l i m e s t o n e a t the t o p o f w h i c h t h e f o s s i l s were  found.  F a v o s i t e s sp. Streptelasma  Stromatoperoids: sp.  Acervularia g r a c i l i s , Billings.  (1) A c t i n o d i c t y o n K e e l e i new sp. (2)  Undetermined sp.  1. K e e l e , J . - Mackenzie* m o u n t a i n s , C.G.S.Rpt.1097, pp.38-39.  -72P o s s i b l y the g r e a t e r p a r t o f the u n d e r l y i n g i s e q u i v a l e n t to the M i d d l e n a t i o n a l "boundary, and forms one  S i l u r i a n limestone  to t h e M i d d l e  o f the most c h a r a c t e r i s t i c  limestone  a t the  inter-  S i l u r i a n limestone  which  Paleozoic horizons i n  Alaska* S i l u r i a n f o s s i l s have been f o u n d a t the  following  local i t i e s i n Alaska. J.  Northwestern Alaska. The  S i l u r i a n limestone j  known as the S k a g i t f o r m a t i o n . f o r 600  m i l e s from P o r c u p i n e  of northwestern  Alaska i s  T h i s h o r i z o n has been t r a c e d  r i v e r to the I g i e b u k H i l l s , n e a r  K o t z e b u e Sound o f the A r c t i c ocean.  I t i s d o u b t l e s s the same  h o r i z o n as found i n Yukon a l o n g the i n t e r n a t i o n a l The  t r e n d through northwestern  to l a t i t u d e  68,  The  Skagjit  boundary.  A l a s k a i s more o r l e s s  limestone  i s b e l i e v e d to be 1  middle or e a r l y are g i v e n J-l.  152°  parallel  u p p e r S i l u r i a n i n age.  late  -  The  fossil  localities  here. 30*  A single  W. , 67° 30* fossil  by S c h u c h e r t  T  I\ . ( a p p r o x . ) .  collected  by F.O.  as "a b r a c h i o p o d  valley  of John r i v e r .  S c h r a d e r was  identified  o f the o r d e r o f M e r i s t i n a  and M e r i s t e l l a , and a l s o r e s e m b l i n g a t r a n s v e r s e Seminula." The age was c o n s i d e r e d as u p p e r S i l u r i a n o r l o w e r 2  Carboniferous. J-2.  148°  56'  ¥.,  67° 52*  N.  North  f o r k of Chandalar r i v e r .  A c o l l e c t i o n o f s h e l l s made by M e r t i e were i d e n t i f i e d 1. 0  SmithTPTs. & M e r t i e J7B. }  0  , j r . - UVs.G.S. B u l l . 8 l 5 ,  pp.124-— 1  ,  2. S c n r a d e r , F . C - U.S.G.S. P r o f . P a p . 2 0 , p.57,  1°04.  by  32,  1930.  -73-  Edwin K i r k as 'Conchidium  ? sp.  f  and c o n s i d e r e d t o be  p r o b a b l y the same genus as found i n t h e l a t e m i d d l e  Silu-  r i a n o f the White mountains o f Yukon-Tanana r e g i o n and i n the upper S i l u r i a n of Southeastern A l a s k a .  1  O v e r l y i n g t h e S k a j i t l i m e s t o n e and below the Devonian sequence i s a g r o u p o f n o n - c a l c a r e o u s beds c o n t a i n i n g , however, one  o r more prominent  beds o f l i m e s t o n e .  This i s b e l i e v e d to  be upper S i l u r i a n . K.  Porcupine  valley.  A l t h o u g h b e l i e v e d to be more o r l e s s c o r r e l a t i v e the S k a j i t  f o r m a t i o n , the f o s s i l s o f t h e S i l u r i a n d o l o m i t e o f  Porcupine v a l l e y i n d i c a t e dle  with  collected  a somewhat l o w e r h o r i z o n .  E.M.  Kin-  f o s s i l s f r o m two l o c a l i t i e s which are g i v e n  here. K - l . 142°  f  4.5  river.  W. , 6 6 ° 59  f  N.  Lower r a m p a r t s o f P o r c u p i n e  31 genera were c o l l e c t e d  These g i v e a fauna e s s e n t i a l l y t e d by l o c a l i t y C above.  K-2.  from d o l o m i t i c l i m e s t o n e .  s i m i l a r to that represen-  T h i s c o l l e c t i o n was  referred  K i n d l e to the m i d d l e S i l u r i a n .  He n o t e s the s i m i l a r i t y  t o the N i a g a r a of e a s t e r n N o r t h  America.  143°  08' W.,  river.  6 6 ° 39  r  N.  Lower r a m p a r t s  of Porcupine  A group o f p o o r l y p r e s e r v e d g r a p t o l i t e s  l o c a l i t y were r e f e r r e d or Cayugan. d o l o m i t e one.  from  this  by U l r i c h t o the l a t e N i a g a r a n o r  T h i s fauna i s somewhat l a t e r t h a n the The  by  f o s s i l s were f o u n d i n s h a l e s  1. Merti©,J.B.,jr.- U.S.G.S. B u l l 7 7 3 , u . 2 3 2 , 1925. 2. K i n d l e , E . H . - B u l l . G e o l . S o c . A m . , V o l . 1 9 , pp.324-327,  1908.  -74i n t e r b e d d e d w i t h l i m e s t o n e a t the t o p o f the  Silurian  sequence. K i n d l e e s t i m a t e d the S i l u r i a n o f P o r c u p i n e  r i v e r t o be about  2500 f e e t t h i c k . 1.  Yukon-Tanana r e g i o n - White M o u n t a i n s . The  S i l u r i a n l i m e s t o n e h o r i z o n o f the White M o u n t a i n s  i s d e s c r i b e d by P r i n d l e as a h e a v i l y bedded magnesian about 100  limestone  f e e t t h i c k which conformably o v e r l i e s O r d o v i c i a n lime-  stone. 20' W. , 65  147°  30'  0  IT.  Brachiopod  g u l c h , 53 m i l e s  F.  0  9-f- E. o f F a i r b a n k s , A l a s k a . Pentamerus sp. According approximately  M.  F i a g a r a n age."*"  . Most o f the  i s now  t o K i r k t h i s Pentamerus i n d i c a t e s an •  ' S i l u r i a n ' f a u n a o f w e s t e r n Seward P e n i n s u l a  r e f e r r e d by K i r k to the O r d o v i c i a n .  the P o r t C l a r e n c e 166°  50 * W.,  o f Don  limestone 65°  25'  F.  But  i s r e f e r r e d t o the  one  l o t from  Silurian:  2  2 m i l e s southwest o f the f o r k s  river. F a v o s i t e s sp. Pentameroid  brachiopod.  T h i s f a u n a i s c o n s i d e r e d to be m i d d l e to upper S i l u r i a n . I n a d d i t i o n t o the d e f i n i t e h o r i z o n s , a c o n s i d e r a b l e p a r t o f r o c k s mapped as  'undifferentiated Paleozoic' i n inter-  i o r and n o r t h e r n A l a s k a are thought to be S i l u r i a n  and  1. P r i n d l e , L . M . - U.S.G.S. B u l l . 5 2 3 , p p . 4 2 - 4 3 , 1913. 2. Steidtmann,E.& Cathcart,S.H.-U.S.G.S.Bull.733,p.28,  ~ 1922.  i  p a r t i c u l a r l y upper S i l u r i a n  j  limestones  and  siliceous  i n age.  These rocks  s h a l e s and  eonsist of  slates.  DEY0NIA1T SYSTEM.  A g e n e r a l i z e d Devonian published found  that  and  to  by J.B.  d i s c u s s the  g r e a t a t a s k f o r the the  citing  aim  r  Mertie s  and  1  data  from  individual  purpose of t h i s  be  other invertebrates.  Islands, i n southeastern High  s l a t y beds i n the b o u n d a r y ) and  by  It is  achieved  U p p e r D e v o n i a n , c h a r a c t e r i z e d by  2.  geolo-  localities  paper.  bee  is  felt by  s e c t i o n , g i v e n as f o l l o w s :  These r o c k s  B r o o k s Range, o f n o r t h e r n A l a s k a , a n d Chlchagof  been  D e v o n i a n f o s s i l s have  of a g e n e r a l c o r r e l a t i o n w i l l  "1» junotus  Mertie.  i n n e a r l y e v e r y l a r g e a r e a examined by  i n Alaska  gists, too  recently  s e c t i o n f o r A l a s k a has  Middle  the  are  found  i n the  on P r i n c e o f W a l e s  and  Alaska.  Devonian, t y p i f i e d  Tatonduk-Hation  Spirifer dis-  district  by  siliceous  (near  and  Yukon-Alaska  W o o d c h o p p e r v o l c a n i c s f a r t h e r down t h e  Yukon. 3.  Middle  bedded limestone including  age, 1.  and  Devonian proper, s h a l e , found  the  Tatonduk-Hation  4.  Salmontrout  typically  on  the  e x e m p l i f i e d by  i n many p a r t s o f  Alaska,  district.  l i m e s t o n e , o f lowest  Porcupine  thin-  R i v e r , and  also  Middle  Devonian  i n the  M e r t i e , J . B . , j r . - U . S . U . S . B u l l . « 3 b , pp.34? & 414,  19&.  '  ~  • Tatonduk-Nation  district,"  -76-  1  In Yukon T e r r i t o r y Devonian f o s s i l s have "been found: on the i n t e r n a t i o n a l "boundary, north of Yukon r i v e r ; at the source of Beaver r i v e r ; and on Braine creek, at the StewartPeel r i v e r s  f  divide.  I t i s also l i k e l y that some of the basic  igneous rocks i n the rather complicated volcanic s e r i e s of the Yukon may  be Devonian.  International boundary section. Limestone. The Devonian limestones of the 141st. meridian, 1  2  north of Yukon r i v e r , as described by Mertie , and Cairnes , are l i t h o l o g i c a l l y very s i m i l a r to the Silurian-Cambrian limestones.  They are, however, somewhat more homogeneous and  darker i n appearance, and are i n most places c h a r a c t e r i s t i c a l l y coarsely c r y s t a l l i n e .  The l a s t feature i s believed to be  due to some inherent character of the rock rather than to excessive metamorphism, for t h i s limestone i s bordered above and below by n o n c r y s t a l l i n e limestone.  The most s i g n i f i c a n t  difference between the Devonian and older Paleozoic limestones i s the l e s s abundant secondary s i l i c a i n the higher horizon. The close s i m i l a r i t y between the Devonian and e a r l i e r Paleozoic limestones has disguised the r e l a t i o n s h i p between the two groups of rocks.  But the apparent absence of Lower  Devonian f o s s i l s here, as elsewhere  i n Alaska and Yukon, and  the f a c t that small bodies of basic igneous rocks cut the older Paleozoic sediments and appear to be Devonian i n age, 1. Idem.- pp.407-40b". " '• ° " ""* 2. Cairnes,D.D.- C.G.S. Mem.67, pp.75-76, 1914.  suggests  2MTOsJ,aii f O B sIX loo a l l tie© Yukon Territory.  -77a Silurian-Devonian unconformity.  A.  Salmontrout  Devonian  limestone ( p a r t i c u l a r l y  Boundary s e c t i o n , Salmontrout Kindle*). a list  A-l.  The  1 4 1 ° W.  on the b a s i s o f f o s s i l river  f o l l o w i n g approximate  evidence, with (as described  localities  the by  are g i v e n w i t h  fauna:  b e t w e e n 66°  20»  and  66°  30*  N.  H e a r Raquet  and  Creeks. L i n g u l a sp. Camarotoechia  A-2.  o f the  i n Keele mountains) o f the  limestone of Porcupine  o f the  Bern  Cairnes correlated part  limestone.  1 4 1 ° W.  sp.  b e t w e e n 6.5° 2 0 '  I Stropheodonta G y p i d u l a sp.  and 65°  30«  N.  sp.  South  of  Ettrain  Creek.  Favosites sp. Camarotoechia sp. Pugnax o f . pugnus (Martin)• P l a t y e e r a s sp. C y t h e r e l l a sp. Cyphaspis c f . b e l l u l a . Z a p h r e n t i s sp. Stropheodonta sp. Gypidula sp. P r o d u o t e l l a sp. Reticularia cf.laevis (Hall). H u c l e o s p i r a sp. P r o e t u s sp* M a r t i n i a c f . maia (Billings).  Atrypa r e t i c u l a r i s l i n n . var. leptaena rhomboidalis (Wilck). Schizophoria s t r i a t u l a (Schlot). Anoplotheca c f . a c u t i p l i c a t a (Gon.). Atrypa spinosa H a l l . Reticularia? of. subundifera (M.and W.). Cyathophyllum sp. Camarotoechia c o n t r a c t a H a l l ? Stropheodonta arcuata H a l l . Favosites of. basaltica Goldf. Favosites c f . canadensis (Billings). A l v e o l i t e s sp. Chonetes sp.  1. K i n d l e ,E.M. - B u l l . G e o i . S o o . A m . , V o l . X I X , 2. C a i r n e s , D . D . - O p . c i t . , p p . 7 8 - 8 0 .  . " l W  pp.327-329 '  7  -78141° W. between 6\5° 00* and 65° 10' Iff.  A->.  duk  river.  F o r t h o f Taton-  The f a u n a h e r e i s much t h e same a s t h a t o f  A-2 w i t h t h e f o l l o w i n g a d d i t i o n s ; Meristella cf. laevis (Vanux.). Productella cf. spinulicosta Hall. Fenestella sp. Atrypa c f . f l a b e l l a t a Goldf. Conocardium c f . cuneus Conrad.  Leptaena  rhomboidalis (Wilok.). Cryphaeus? s p . Platychisma? sp. Cyathophyllum c f . _uadrigeminum G o l d f .  As a l r e a d y n o t e d t h e f a u n a l i s t e d above was cons i d e r e d c o r r e l a t i v e w i t h the Salmontrout h o r i z o n o f Porcupine river.  The c o r r e l a t i o n o f A - J w i t h t h e S a l m o n t r o u t i s f u r t h e r  strengthened  by a d d i t i o n a l m a t e r i a l c o l l e c t e d i n t h e d i s t r i c t  a d j o i n i n g t h i s l o c a l i t y on the w e s t .  1  S e v e r a l l o t s o f f o s s i l s c o l l e c t e d by C a i r n e s  could  not be p l a c e d i n a d e f i n i t e h o r i z o n and were r e f e r r e d p r o v i s i o n a l l y to t h e D e v o n i a n .  As K i n d l e (who examined t h e  f o s s i l s ) n o t e s , i t i s s i g n i f i c a n t t h a t none o f t h e l o t s i n c l u d e any c h a r a c t e r i s t i c U p p e r o r Lower D e v o n i a n f o r m s . i n g were c o n s i d e r e d  t o be M i d d l e  The f o l l o w -  Devonian, but p o s s i b l y  r e p r e s e n t i n g a f o r m a t i o n d i s t i n c t from t h e S a l m o n t r o u t l i m e stone:^ B-l.  140° 59» W.,  65° 46» H.?  Head o f a south b r a n c h o f  Kandik r i v e r ? G l a d o p o r a c f . dichotoma H a l l . P h i l l i p s a s t r a e a v e r n e u i l l i M Edwards. P r o e t u s c f . macrocephalus H a l l . 1. M e r t i e ,J.B. J r . - O p . c i t . , p.412. 2. Cairnes,D.D.- O p . c i t . , p . 8 l .  ~~  ~~~~  "  -79B-2.  140°  00' W.,  65° 23' F.  P r o d u c t e l l a ? sp. A t r y p a sp. nov.? M a r t i n i a c f . Maia Bill.  South of E t t r a i n  creek.  S t r o p h e o d o n t a sp. P r o e t u s c f . macrocephalus H a l l .  Limestone and s h a l e . T h i s f o r m a t i o n i s known d e f i n i t e l y a t o n l y l o c a l i t y a l o n g the A l a s k a - Y u k o n boundary.  The  one  r o c k s here were  mapped by C a i r n e s a s p a r t o f h i s ' C a r b o n i f e r o u s to Devonian s h a l e - c h e r t g r o u p * , but f o s s i l s c o l l e c t e d by H a r r i n g t o n and Mertie  i n d i c a t e t h a t the h o r i z o n i s i n t e r m e d i a t e between the  Salmontrout  l i m e s t o n e and t h e h i g h e r s h a l e - c h e r t group.  known l o c a l i t y i s j u s t n o r t h o f Tatonduk r i v e r ( 6 5 ° the 1 4 1 s t .  The  00' K.)  at  meridian.  S h a l e and c h e r t b e d s . These beds are d e s c r i b e d by C a i r n e s as o c c u r r i n g a l o n g the 1 4 1 s t . m e r i d i a n from j u s t n o r t h o f H a r r i n g t o n (63°  05  r  IT.) s o u t h t o n e a r Yukon r i v e r .  r e p r e s e n t e d at Shade and E a g l e c r e e k s . essentially  The  creek  s e r i e s i s best  The r o c k s c o n s i s t  o f a r g i l l i t e , s l a t e , c h e r t , and c h e r t y g r i t .  The  l o w e r p a r t o f the sequence i s composed o f v a r i o u s s h a l e s , argillaceous limestone, a r g i l l i t e , siliceous chert.  s l a t e , and some  These r o c k s a r e a l l s i l i c e o u s , but c h e r t i s most  characteristic  o f the upper members.  At Shade creek  these  r o c k s r e s t on l i t h o l o g i c a l l y s i m i l a r O r d o v i c i a n beds, but exact c o n t a c t has not been d e t e r m i n e d .  The  average s t r i k e i s  n o r t h w e s t , but d i p s v a r y due t o i n t r i c a t e f o l d i n g . i . M e r t i e , J . B . , j r . - O p . c i t . , pp.412-413.  the  The  -80foilowing  f a u n a was  as h i g h M i d d l e  C-l.  Devonians  00'  141°  determined  W.,  by K i r k a s m a r k i n g  the h o r i z o n  1  6 4 ° 55>  N.  North  F a v o s i t e s sp. A c e r v u l a r i a sp. Zaphrentis sp. J j e i o r h y n c h u s sp, Pteropod (?)  f o r k o f Shade  creek.  S p i r i f e r sp. Stropheodonta sp. B a o t r i t e s ? sp. Orthoceras sp.  2 Plant .0-2.  remains. 141° One  00/f.W., 6 5 ° 01» fragment  to  J u s t n o r t h o f Tatonduk  of a c o l l e c t i o n of plant  C a i r n e s , was portion of  B".  determined  by  made b y  D. W h i t e a s p r o b a b l y b e i n g  'Archaeosigillaria*  possibly  remains,  river.  and  b a s a l M i s s i s s i p p i a n but  a  r e f e r r e d the h o r i z o n more p r o b a b l y U p p e r  Devonian.  Upper Beaver  D.  135° to  River  25«  Section. 6 4 ° 32*  W.,  U.  Head o f Carpenter creek,  the h e i g h t o f l a n d .  The  following  fossils  were  , c o l l e c t e d by  Cockfield  and  determined  by  near  3 Kindle:  Favosites c f . digitatus. Favosites cf. radiatus. C y r t i n a c f . umbonata. T h i s f a u n a was  referred  stone h o r i z o n from which states:  to t h e these  " I t seems p r o b a b l e t h a t  the Devonian  Devonian.  Of t h e l i m e -  f o r m s were t a k e n  w i t h i n t h e a r e a mapped  i s r e p r e s e n t e d o n l y to a s l i g h t  ~  Cockfield  1.  Idem., p . 4 1 3 .  —~"—~~  2. 3.  Cairnes,D.D.- O p . c i t . , pp.83-84. C o c k f i e l d , W . E . - C.G.S.Sum.Rpt. 1 9 2 4 ,  "—' Pt.A,  extent  '  po.6-7,  and  ~" 1925.  -81-; that  practically  a l l the limestone  Ordovician or Silurian. between t h e s e  Braine  Ho  mapped b e l o n g s  d e f i n i t e b r e a k was  t o the  recognized  two s y s t e m s . "  Creek S e c t i o n . The  sediments o f the O g i l v i e  creek a r e d e s c r i b e d by C a m s e l l  1  mountains along  as l y i n g  Braine  i n the f o l l o w i n g  succession: Massive d o v e - c o l o u r e d limestone becoming s h a l y a t base. Beds o f b l a c k s l a t e . Massive g r a n u l a r limestone c o n t a i n i n g f o s s i l s . Ferruginous s l a t e s weathering r e d . Black weathering conglomerate ( b a s e ) . These b e d s l i e i n a n t i c l i n e s west. creek  and s y n c l i n e s which s t r i k e  The t h i c k n e s s o f t h e s e d i m e n t s i s n o t g i v e n . i s b e l i e v e d to l i e a l o n g a t h r u s t  fault  north-  Braine  which has exposed  2 the  lower  beds o f the s e c t i o n .  creek at s e v e r a l l o c a l i t i e s ; follows: E. 135° W.  between 64° 20'  Fossils  the general l o c a l i t y  and 64° 30'  Favosites. Productella. Atrypa r e t i c u l a r i s This  f a u n a was r e f e r r e d  were f o u n d  H.  along the  i s given as  Braine  creek.  ?  provisionally  t o t h e D e v o n i a n by  Whiteaves. The  s e c t i o n given suggests  may be c o r r e l a t i v e w i t h  that the f o s s i l i f e r o u s  the Salmontrout  limestone  limestone and t h a t the  b l a c k s l a t e s may c o r r e s p o n d t o h o r i z o n 3 o f t h e g e n e r a l i z e d Alaska  section.  i . C a m s e l l , c . - C.U.S. Sum.Rpt. 1 9 0 6 , P t . C C , p . l b . 2* Idem.- p . 4 8 .  • -82-* Mackenzie mountains These hut  and Mackenzie  River  d i s t r i c t s l i e to t h e east  a r e m e n t i o n e d h e r e b y way o f  •• '  '••  F.  "••  "• 1  the e a s t e r n f o o t h i l l s o f the  along the course o f Gravel  posed o f massive l i m e s t o n e , l y i n g o f M i d d l e Devonian age.  lands.  separating  These 125°  45'  Fossils  i n fault  river,  b l o c k s and p r o b a b l y  were f o u n d a b o u t a t t h e  the f o o t h i l l s from the Mackenzie  64°  W.,  15» IU  river.  Gravel  low-  Hederella  35  miles  Streptelasma rectum ( H a l l ) . Phillipsastraea vemeuili (Milne-Edwards & Haime).  canadensis (Nicholson)..  Both o f the brachiopods i n t h i s Salmontrout  r i v e r , about  Two l o c a l i t i e s .  Atrypa r e t i c u l a r i s (1.). Atrypa spinosa ( H a l l ) .  collection  occur i n the  l i m e s t o n e o f Yukon and A l a s k a .  The D e v o n i a n o f G r e a t S l a v e l a k e , l o w e r P e a c e  rivers,  a s com-  are given as follows:  from Mackenzie  G.  Territory,  correlation.  has d e s c r i b e d  mountains,  escarpment  o f Yukon  "•  Joseph Keele  Mackenzie  valley.  and l o w e r Mackenzie  river,  and  Liard  h a s b e e n d e s c r i b e d by  2 Kindle.  [I]  Two m a j o r  divisions  are recognized:  U p p e r D e v o n i a n - p r e d o m i n a t i n g s h a l e s w i t h some l i m e s t o n e s . Lower D e v o n i a n - p r e d o m i n a t i n g l i m e s t o n e w i t h some s h a l e . Brooks and K i n d l e  correlations  , after  discussing  possible  o f t h e D e v o n i a n o f t h e Upper Yukon w i t h  Devonian  horizons elsewhere i n North America, note t h e d i f f i c u l t y o f c o m p a r i s o n due t o t h e d i v e r s i t y  o f f a u n a s and t e n d e n c y o f  1. Keele,J.-_c.G.S. R p t . 1 0 9 7 , p.39~  \* K i n d l e , E . M . - i n C.G.S. M e m . l o 8 , p p . 6 2 - 6 6 , 1 9 2 1 . 3. B r o o k s . A . H . & K i n d l e ,E.M.- B u l l . G e o l . S o c . A m . , V o l . X I X , p . 2 9 1 ,  •L ^0 o «  Devonian faunas to develop p r o v i n c i a l appears p r o b a b l e . . . .  that  types,  but s t a t e :  the D e v o n i a n f a u n a o f Yukon  bears a c l o s e r r e l a t i o n s h i p t o the Mackenzie R i v e r to  any o f t h e o t h e r w e s t e r n f a u n a s o u t s i d e T h e r e i s some e v i d e n c e  that  part  t i a t e d * , *Braeburn», o r * C a r b o n i f e r o u s Lewes R i v e r b a s i n o f s o u t h e r n age.  may a l s o ous  be D e v o n i a n .  The e v i d e n c e  fauna  than  of the *Undifferen-  (?)« l i m e s t o n e s  o f the  o f Devonian  q u a r t z i t e s and s l a t e s  i s given under  "Carbonifer-  System".  Lower P a l e o z o i c It rocks  Igneous  Rooks.  i s pertinent  o f Y u k o n and A l a s k a  Devonian a g e . stone  habit*  larly  along  V o l c a n i c and i n t r u s i v e  o f Yukon r i v e r .  still  and along  *green-  particu-  the Yukon-Alaska vary  from a n d e s i t i c  They are diverse  i n age.  the Precambrian  which  sediments,  r e m a i n members, p a r t i c u l a r l y u l t r a - b a s i c , w h i c h  a p p e a r t o be l a r g e l y writer  of general  a r e u n d o u b t e d l y Me so z o i c a n d t h o s e  a p p e a r t o be a s s o c i a t e d o n l y w i t h there  rocks  These rocks  to u l t r a - b a s i c types.  groups which  igneous  which are b e l i e v e d t o be, i n p a r t , o f  the u p p e r Yukon r i v e r ,  diabasic  Excluding  to discuss; c e r t a i n b a s i c  have b e e n n o t e d a t numerous l o c a l i t i e s ,  boundary south and  cherty  district  of Alaska*"  Y u k o n may be i n p a r t  The p r e s u m a b l y u n d e r l y i n g  "It  lists  the se i g n e o u s  D e v o n i a n o r Lower P a l e o z o i c  the following rocks  information  i n age.  i n an attempt  The  to place  as c l o s e l y as p o s s i b l e i n the g e o l o g i c a l  sequence.  Woodchopper v o l c a n i c s . These rocks  have b e e n d e s c r i b e d  by Brooks and K i n d l e ,  -84Mertie, and other g e o l o g i s t s . west of meridian 143° W. stones with interbedded  1  They l i e along Yukon r i v e r  The s e r i e s consists o f "bedded greenlimestone, shale, s l a t e , and chert.  The structure i s highly complicated.  F o s s i l s i n the sediments  indicate that the s e r i e s i s high Middle Devonian i n age. Brooks and Kindle, i n the report c i t e d , mentioned the s i m i l a r i t y of the greenstones t o McConnell*s »Moosehide group*  which  i s here included with the Yukon group. 2.  The general run o f greenstones (not intimately associated  with sediments) of the upper Yukon region of Alaska i s 3  described by Mertie  as follows:  "Greenstones are known at many horizons i n the Paleozoic and pre-Paleozoic seajienoes o f Alaska, and most o f these rocks resemble one another g r e a t l y . . . . the present grouping includes a l l the Paleozoic basio and u l t r a b a s i c rooks of greenstone h a b i t . The serpentine, however, which forms a large part o f these rocks, i s known to intrude the S i l u r i a n and Middle Devonian rocks of t h i s region but has not been seen anywhere i n rocks o f l a t e r age. This does not d e f i n i t e l y e s t a b l i s h i t s age, f o r i t may have been intruded at depths below the surface too great to reach the l a t e r Paleozoic rocks. But a s t r a t i g r a p h i e d i s c o n t i n u i t y and perhaps angular unconformity of considerable magnitude i s believed to separate the Middle Devonian rocks o f t h i s area from the overlying Carboniferous sequence, and with the idea i n mind that such rock deformation i s u s u a l l y accompanied by volcanism, i t seems possible that these u l t r a b a s i c rocks are Upper Devonian. '* 3»  The basic i n t r u s i v e s ( l a r g e l y dykes and s i l l s of diabase)  of the Yukon-Alaska boundary between Yukon and Porcupine r i v e r s are described by C a i r n e s  4  as extensively developed i n  association with members of the T i n d i r and Yukon groups. Some, 1. Brooks.A.H. <fe Kindle , E . ^ . - B u l l . f i e o l . S o o . A m . , V o l . x j l ^ p j . g ^ * 2. 3. 4.  Mertie ,J.B. J r . - U.S.G.S.Bull.8l6, pp.75-80, 1930. McConnell,R.G.- C.G.S. Rpt.884, pp.22B-23B, 1904. Mertie,J.B.,jr.- Op.cit., pp.149-150. Cairnes,D.D.- C.G.S. Mem.67, p.110, 1914.  -85however, a r e thought found  t o he D e v o n i a n i n age b e c a u s e t h e y  were  to c u t the Lower P a l e o z o i c beds* o  4.  Hear l a t i t u d e  greenstones  62  40* o n t h e 1 4 1 s t .  consisting  m e r i d i a n a group o f  o f gabbro , d i a b a s e , b a s a l t , and u l t r a 1  b a s i c m a t e r i a l has been d e s c r i b e d by B r o o k s . l a i n unconformably  by conglomerate  formation, which from  fossils  These a r e o v e r -  and s l a t e o f the W e l l e s l e y  c o l l e c t e d by Brooks,  i s now c o n 2  s i d e r e d t o be C a r b o n i f e r o u s a n d p r o b a b l y M i s s i s s i p p i a n The  b a s a l p a r t o f the W e l l e s l e y i s mostly  pebbles and,  and c o b b l e s i d e n t i c a l  a s the greenstone  beds w h i c h a r e m o s t l y  i n age •  a conglomerate  to the greenstone  of  i n composition,  intrudes undifferentiated Paleozoic Silurian  i n a g e , i t i s b e l i e v e d t o be  Devonian. 5*  Basic igneous  peridotite, they  r o c k s , composed l a r g e l y o f p y r o x e n i t e and  are widely d i s t r i b u t e d  are not developed  i n Southern  i n abundance.  Yukon  although  T h e y were d e s c r i b e d i n  3 Atlin  district  under  t h e name  'Gold S e r i e s ' by G w i l l i m .  Sim-  4  i l a r r o c k s have s i n c e been found  i n Whitehorse  district  , and  .5' in Little similar  Salmon a r e a  .  The w r i t e r h a s s e e n  lithologically  r o c k s a t the h e a d o f t h e s o u t h f o r k o f B i g Salmon  r i v e r , a n d o n Lewes r i v e r n e a r  t h e mouth o f t h e P e l l y .  The a g e  is uncertain.  The ' g r o u p ' , i f i t may be c o n s i d e r e d a s a u n i t ,  has been f o u n d  t o c u t members o f t h e Y u k o n a n d Mount  groups.  I n the southern  d i s t r i c t s these  Stevens  r o c k s have been  found  T n r o o k s , A . H Y - U.S.G.S. 2 o f h A n . R p t . , p i . 7 , ~~ 2. M e r t i e , J . B . , j r . - U.S.G.S. B u l l . 8 2 7 , p . 2 6 , 1 9 3 1 . 3. G w i l l i m , J . C . - C.G.S. R p t . 7 4 3 , p p . l 8 B - 1 9 B , 1 9 0 1 . 4 . C o c k f i e l d , W . E . & B e l l , A . H . - C . G . S . M e m . l 5 0 , p p . 1 0 - 1 1 , 1926. 5 . C o c k f i e l d , W . E . - C.G.S. Sum.Rpt. 1928, p t . A , p . 5 , 1929.  -86associated with he  sediments of  Carboniferous)  intrude the then,  but  there  the  Taku group  (here  i s no  recorded  evidence  Taku sediments.  i s that these  The  most a c c u r a t e  b a s i c igneous  rocks are  age  considered that  to  they  assignment  probably  lower  Paleozoic.  CARBONIFEROUS SYSTEM.  Carboniferous Yukon and  Alaska.  division  of the  plished, horizons ilarly along  in  both  I n most d i s t r i c t s o f Yukon T e r r i t o r y  sub-  Carboniferous  b e e n accom-  but  M i s s i s s i p p i a n , Pennsylvanian,  and  Permian  are  recognized the  along  upper part of the  The ' '' Carboniferous  the  Yukon-Alaska boundary.  Carboniferous  stratigraphy i s best  Yukon r i v e r .  primarily  Upper Y u k o n R i v e r r e g i o n o f  t o the  Reference  to  Simknown  Alaska,  upper Yukon s e c t i o n .  Alaska.  following general was  g i v e n by  s t r a t i g r a p h i e sequence o f the • I • B r o o k s and K i n d l e i n 1908 f o r the  r e g i o n embracing u p p e r White  river,  i n t e r v e n i n g p a r t o f Yukon  Upper  distributed  not  t h e r e f o r e , w i l l be  the  are w i d e l y  sequence has  i n Alaska the  rocks  lower  Porcupine  river,  and  river:  Carboniferous. Heavy l i m e s t o n e ( i n v e r t e b r a t e f o s s i l s ) ; Yukon r i v e r n e a r mouth o f N a t i o n r i v e r , u p p e r W h i t e River valley. Unconformity  ?  1. B r o o k s , A . H . & K i n d l e , E . M . - B u l l . G e o l . S o c . A m . , V o l . 1 9 ,  pp.262,291-304,  "  1908.  C a r b o n i f e r o u s l o c a l i t i e s of A l a s k a - a n d Yukon. The l e t t e r s are the same as t h o s e used under ' C a r b o n i f e r o u s System' i n the t e x t .  -87lower  Carboniferous N a t i o n R i v e r f o r m a t i o n , conglomerates, sandstones, and s h a l e s ( p l a n t f r a g m e n t s ) ; Yukon r i v e r a t mouth of Nation r i v e r . Unconformity. Calico B l u f f formation; s l a t e s and s h a l e s , some brate f o s s i l s ) . Calico upper Yukon r i v e r , a l s o  thin-bedded limestone, igneous rocks ( i n v e r t e B l u f f and o t h e r p o i n t s on on P o r c u p i n e r i v e r .  Conformity. Upper D e v o n i a n B l a c k and grey s h a l e s and s l a t e s . (A few i n v e r t e b r a t e f o s s i l s ) ; C a l i c o B l u f f , on Yukon and on Porcupine r i v e r * F o s s i l s from the 'Upper C a r b o n i f e r o u s * l i m e s t o n e i n the t a b l e above were l a t e r d e t e r m i n e d t o be P e r m i a n i n a g e *  1  A.  A more d e t a i l e d s e c t i o n f o r t h e A l a s k a p o r t i o n o f t h e 2 r e g i o n d e s c r i b e d by B r o o k s and K i n d l e i s g i v e n by M e r t i e a s fOllOWSS  Tahkandit  limestone.  M o s t l y l i m e s t o n e , but g r a d e s i n t o i n t e i n f o r m a t i o n a l cong l o m e r a t e s ( c h e r t p e b b l e s ) . 527 f e e t . H i g h l y f o s s i l i f e r o u s . Low Permian h o r i z o n . Nation River formation. S h a l e , s a n d s t o n e , and conglomerate ( c h e r t p e b b l e s i n sandy m a t r i x ) . C o n t i n e n t a l o r i g i n . C o n t a i n s some c o a l beds, and many f r a g m e n t a r y p l a n t r e m a i n s . 5000 t o 6000 feet t h i c k . Pennsylvanian ? T r a n s i t i o n a l formation. Sandy s h a l e , a r g i l l i t e , s l a t e , and some c h e r t . B e l i e v e d to o v e r l i e C a l i c o B l u f f f o r m a t i o n and u n d e r l i e N a t i o n R i v e r f o r m a t i o n . 1000 t o 2000 f e e t e s t i m a t e d . No diagnostic f o s s i l s . 1.  Smith,P.S. & M e r t i e , J . B . , j r . - U.S.G.S. B u l l . 8 1 5 , table,.1930..  correlation  2 . M e r t i e , J . B . , j r . - U.S.G.S.Bull.816,pp.84,85-130 , 1930.  -88Calico  Bluff  formation.  A l t e r n a t i n g b e d s o f l i m e s t o n e a n d s h a l e w i t h some s l a t e . Marine o r i g i n . 968 f e e t . Highly fossil iferous. Upper Mississippian. Chert  formation. The l i t h o l o g y i s v a r i e d and a p p a r e n t l y d i f f e r s i n d i f f e r ent l o c a l i t i e s . l a r g e l y c h e r t s w i t h s h a l e s , s l a t e s , and c h e r t b r e c c i a s . G e n e s i s unknown. - P r o b a b l y s e v e r a l F o s s i l s nondiagnostic, lower thousand f e e t t h i c k . Mississippian ?  Circle voloanics. B a s a l t i c lavas of greenstone h a b i t , with chert a r g i l l i t e , and t u f f s . Considered Mississippian. t  :  •.;vy;:.'if-hi^  ;s.equenee i s - b e l i e v e d to. be s e p a -  ;  r a t e d from  the Devonian by a d e p o s i t i o n a l  s e n t e d by the apparent ior  Alaska.  discontinuity  repre-  absence o f the Upper Devonian i n i n t e r -  No m a j o r u n c o n f o r m i t y  Carboniferous  some i n t e r b e d d e d t o be l o w e r .  sedimentation  i s recorded i nthe  although  shown b y t h e t r a n s i t i o n f r o m  changes i n c o n d i t i o n s a r e  marine t o f l u v i a t i l e  back t o  ;  marine d e p o s i t s . The extensive  w r i t e r cannot  fossil  undertake  remains taken  upper Yukon r i v e r  of Alaska.  from  Tahkandit  forms a r e s a i d The horizons  limestone.  b e s t known o c c u r r e n c e s  B.  York  i n their  following i s a brief with  district  Bluff  genera  and Permian  affinities.  summary o f t h e o c c u r r e n c e o f  the upper Yukon s e c t i o n .  are given.  o f Seward P e n i n s u l a •  Upper M i s s i s s i p p i a n  of the  f o r m a t i o n a n d 61 i n  Both the M i s s i s s i p p i a n  t o be A s i a t i c  correlative  the Carboniferous  One h u n d r e d a n d s e v e n t e e n  have b e e n r e c o g n i z e d i n t h e C a l i c o the  a tabulation o f the  fossils  were  found i n  Only the  -89undifferentiated Silurian  fossils.  the Idsburne  C.  limestone  The C a r b o n i f e r o u s  limestone  Northern The  containing also  of northern  O r d o v i c i a n and  horizon i s correlated  with  Alaska.*  Alaska. following Carboniferous  section i s given for  2 northern Alaska  (west  o f Chandalar  river):  .Upper M i s s i s s i p p i a n . Lisburne chert.  l i m e s t o n e , o f marine o r i g i n ,  lower M i s s i s s i p p i a n  ( i n part upper  limestone and  Mississippian).  Noatak f o r m a t i o n . Sandstone and shale p r i n c i p a l l y o f marine o r i g i n but c o n t a i n s s m a l l c o a l beds. Includes chert conglomerate formerly c a l l e d Stuver s e r i e s . The originally  lower  called  p a r t o f the l o a t a k f o r m a t i o n ,  the Stuver  rocks and i s a p p r o x i m a t e l y (lower M i s s i s s i p p i a n The lisburne boundary. Bluff  •. .  s e r i e s , o v e r l i e s upper  correlative with  Devonian  the chert  3  formation  ?) o f the u p p e r Yukon.  lisburne limestone  on the A r c t i c Although  •  i . e . the part  extends  eastward  o c e a n f o r 600 m i l e s t o t h e  lithologically  different  formation, p a l e o n t o l o g i c a l l y  i t i svery  from  from  Cape  Yukon-Alaska the  Calico  closely  4 • . correlative. G-l.  The S a d i e r o c h i t s a n d s t o n e  o f n o r t h e r n A l a s k a was o r i g i n a l l y Pennsylvanian,  o f the Canning R i v e r r e g i o n  p l a c e d by l e f f i n g w e l l  b u t i s now c o n s i d e r e d t o be l o w e r  i n the  Permian and  1. Steidtmann,E.<fe flatheart ,S.K*.- UVS.G.S.3ull.723,PP«27-^,19-2. 2 . S m i t h , P . S . & M e r t i e ,J.B. , j r . - U . S . G . S . B u l l . 8 1 5 , p p . 151-18.5, 3 . Idem., p p . 1 5 5 - 1 5 7 . (1930. 4. Idem., p . l 8 4 . 5 . l e f f i n g w e l l , E . d e K.- U . S . G . S . P r o f . P a p . 1 0 9 , p p . 1 1 3 - 1 1 3 , 1 9 1 9 .  and  t h e same h o r i z o n a s t h e T a h k a n d i t • • - 1" Yukon r i v e r .  D.  Copper R i v e r r e g i o n , southern The  as  limestone ••  o f the upper  Alaska*  Strelna formation of Ghitina r i v e r  i s described  composed o f t u f f b e d s , b a s a l t , a r g i l l a c e o u s a n d s a n d y s h a l e ,  c h e r t , and t h i n  limestones.  65OO f e e t o r g r e a t e r . with  The t h i c k n e s s i s c o n s i d e r e d t o be  The S t r e l n a f o r m a t i o n  i scorrelated  t h e C a l i c o B l u f f f o r m a t i o n o f u p p e r Yukon r i v e r a n d the  lisbume  limestone  D-l.  of northern  Alaska.  I n the headwater r e g i o n o f C h i s t o c h i n a r i v e r  o f the  C o p p e r R i v e r b a s i n t h e name Mankomen f o r m a t i o n was g i v e n b y  3 t o bOOO o r 7000  Mendenhall shale• fossil stone  feet  o f limestone,  sandstone,  and  The P e r m i a n a g e o f t h i s h o r i z o n was e s t a b l i s h e d b y collections  and t h e f o r m a t i o n  o n Yukon r i v e r  at the type  was c o r r e l a t e d w i t h  locality  lime-  o f the Tahkandit  limestone. I.  Headwaters The  o f White  river,  southern  following Carboniferous  Alaska.  s e c t i o n i s g i v e n by  A  Capps  for this  In descending  districts  order,  ( 1 ) l a v a s a n d p y r o c l a s t i c b e d s , w i t h some s h a l e s , (2) Massive l i m e s t o n e , a s s o c i a t e d with s h a l e s ; thin-bedded l i m e s t o n e s ; and a l i t t l e sandstone and c o n g l o m e r a t e . ( 3 ) l a v a s a n d p y r o c l a s t i c r o c k s , w i t h a s m a l l amount o f sediments. (4) M a s s i v e l i m e s t o n e beds o f S k o l a i Creek, w i t h i n t e r b e d d e d l a v a s and m i n o r amounts o f s h a l e a n d  1. M e r t i e , J . B . , j r . - U.S.U.S.Bull.81b, p.12?, 1930.—~ 2. M o f f i t , F . H . & M e r t i e , J . B . ,jr.-U.S.G.S.Bull.745,PP»21-28,1923. 3 . M e n d e » h a l l , W . C . - U . S . G . S . P r o f . P a p . 4 1 , pp.40-49, 1 9 0 5 . 4 . Capps,S.R.- U . S . G . S . B u l l . 6 3 0 , p p . 3 3 - 4 7 .  conglomerate. (5) This The  B a s i c bedded, l a v a s , with, l i t t l e  structure of the  Calico  c o n f o r m t o t h e u n d e r l y i n g D e v o n i a n r o c k s and o f the  o v e r l y i n g Mesozoic  Carboniferous  horizons;  fossil  one  correlative and  lower  sediments  collections indicate  the  the  conforms to t h a t  section.  The  Bluff  w i t h the  material.  1 0 , 0 0 0 f e e t o r more i n t h i c k n e s s  s e c t i o n i s b e l i e v e d t o be strata  sedimentary  w i t h the- t y p i c a l  lisburne  two  Mississippian  l i m e s t o n e , the  Permian Tahkandit  limestone  paleontological  other  and  the  of  correlative Mankomen  formation.  F.  A  l i m e s t o n e h o r i z o n i n the  southwestern  Alaska  Permian f o s s i l s  and  u p p e r Kuskokwim v a l l e y  i s d e s c r i b e d by i s the  Brown^" a s  same h o r i z o n a s  the  of  containing  lower  Tahkandit  lime=  stone. I n Yukon T e r r i t o r y widely d i s t r i b u t e d as characteristic e v e r , has boundary.  C a r b o n i f e r o u s a p p e a r s t o be  i t i s i n Alaska.  of the M i s s i s s i p p i a n  been found The  the  only i n areas  Carboniferous  here  by  G.  I n t e r n a t i o n a l boundary  and near  The  abundant  as  fauna  P e r m i a n o f A l a s k a , howto the  Alaska-Yukon  o f Yukon, t h e r e f o r e * i s d i s c u s s e d  localities.  Along  this  b e t w e e n Y u k o n and  s e c t i o n D.D.  Porcupine  Cairnes recognized  rivers.  four  2 g r o u p s o f r o c k s w h i c h he are g i v e n i n d e s c e n d i n g 1. 2.  assigned  to t h e  stratigraphie  Carboniferous.  o r d e r as f o l l o w s :  B r o w n , J . S . - IT.S.G.S. B u l l . 7 8 3 , p p . 1 0 5 - 1 0 6 , 1926. C a i r n e s D . D . - C.G.S. Mem.6?» p p . 8 4 - 1 0 3 , 1914. 9  These  1,  C o n g l o m e r a t e h o r i z o n o c c u r r i n g a t one l o c a l i t y  of Tatonduk r i v e r boulders feet  clay.  because  i t appeared to o v e r l i e  beds which  Referred  tentatively  this  ate upon the C a r b o n i f e r o u s and 2. is  Carboniferous  shales.  i s the r e s u l t  Cambrian  of faulting  group.  and s u p e r j a c e n t  beds.  d e s c r i b e d b y C a r i n e s a s c o n s i s t i n g o f two m a j o r  This  interbedded  cherty  that  i t was f o u n d  r e m a i n s , was c o r r e l a t e d w i t h  type l o c a l i t y  on Y u k o n  sand-  c o n g l o m e r a t e s and s h a l e s .  T h i s h o r i z o n , on t h e b a s i s o f i t s l i t h o l o g y , p o s i t i o n , a n d t h e fact  group  horizons:  (a) lower h o r i z o n c o n s i s t i n g o f brownish to black stones , with  1  s u p e r p o s i t i o n o f the conglomer-  shales  River formation  Mertie,  examined by C a i r n e s .  has i n c l u d e d the h o r i z o n i n the T i n d i r Nation  resembling  to the Permo-Carboniferous  o f the area  that the apparent  and  up t o 3 o r 4  h o r i z o n t o dip u n d e r M i d d l e  l i e t o the west  He c o n s i d e r s  i n size  i n a reddish-coloured matrix  boulder  however, h a s found  north  and d e s c r i b e d a s c o n s i s t i n g o f p e b b l e s  ( l a r g e l y of limestone), ranging  i n diameter,  just  the Nation  stratigraphic  t o c o n t a i n a few p l a n t River formation  at i t s  river.  (b) Beds s u p e r j a c e n t  to the Nation  River  formation.  T h e s e u p p e r members a r e d e s c r i b e d a s c o n s i s t i n g o f a r e n a c e o u s  and a r g i l l a c e o u s .sediments s i m i l a r t o t h e l o w e r b e d s , b u t c o n - ' taining  o c c a s i o n a l l a y e r s o f thin-bedded  tebrate f o s s i l s . Pennsylvanian,  The f o s s i l s  limestone  with  were c l a s s e d a s P e r m i a n o r  and the s u p e r j a c e n t  b e d s were c o r r e l a t e d  1. M e r t i e J . B . , j r . - U.S.G.S. B u l l . b l 6 , p p . 2 5 - 2 8 , 1 9 * 0 . - a n d U.S.G.S. B u l l . 8 3 6 , p . 3 7 9 , 1935* f  2. B r o o k s , A . H . & K i n d l e ,E.M.- O p . c i t . , p . 2 6 2 .  inver-  primarily with a limestone Nation River formation horizon 3. nes  h o r i z o n b e l i e v e d to d v e r l i e the  at i t s type  i s now known a s t h e T a h k a n d i t  limestone-chert  group.  as i n c l u d i n g limestone  dark s h a l e , c a l c a r e o u s  age, C a i r n e s  group o v e r l i e River  i s d e s c r i b e d by C a i r -  and c h e r t s w i t h  o c c a s i o n a l beds o f  and c h e r t y c o n g l o m e r a t e .  g r o u p was c o n s i d e r e d t o be a t l e a s t the  1500  feet  s t a t e s : "The members o f t h i s  thick.  Pennsylvanian  The  Regarding  limestone-chert  the Devonian l i m e s t o n e s , under1ie  beds, and c o n t a i n both  limestone  limestone.  T h i s group  sandstone»  This  locality.  the Nation  and M i s s i s s i p p i a n  f o s s i l s . '*  4.  Shale  largely  group.  i s d e s c r i b e d a s composed  t h e g r o u p was e s t i m a t e d here  Bluff  o f the b o u n d a r y •  s e c t i o n were c o n s i d e r e d  Fossils  800 f e e t  thick.  i n lithology  o f the  t o be P e n n s y l v a n i a n  the  Bluff. 1  of Harrington  a few  from the Harrington  the shale group represented  Cairnes  calcareous  b e d s o n Yukon r i v e r  fore , that Calico  North  t o be a t l e a s t  the c l o s e resemblance  group t o the C a l i c o  m i l e s west  cherts,  and t h i n l y bedded l i m e s t o n e s .  Cairnes noted shale  group*  o f s h a l e s , but i n c l u d i n g c l a y s ,  sandstones, creek  The'shale  suggesting,  a higher horizon  Creek therethan  summarized t h e p a l e o n t o l o g i c a l e v i d e n c e  o b t a i n e d as f o l l o w s * "Thus a l o n g Carboniferous represented  t h e Boundary l i n e  three  h o r i z o n s have been i d e n t i f i e d .  by the M i s s i s s i p p i a n f o s s i l s  I . G a i r n e s , D . D . - O p . c i t . , pp. 10a-10.>.  fairly  definite  The l o w e s t i s  obtained  --------  from the  -94lower p o r t i o n of recent  the  limestone-chert  h o r i z o n i s r e p r e s e n t e d by  t a i n e d from the  s h a l e g r o u p and  limestone-chert group.  The  group*  the  the upper p o r t i o n o f  most r e c e n t  fossils  obtained from the  is  o f A r t i n s k i a n o r U p p e r G s c h e l i a n age  Recently, nes*  fossils,  found  south  the  G i r t y , who  re-allocated 66°  of l a t i t u d e  assigned to Of  has  the  N.  more  horizon i s  and  represented which  thus belongs  to  originally  o f 18  Out  examined  Cairthose  c o l l e c t i o n s , 15  3 t o the  u p p e r M i s s i s s i p p i n a and  problem o f assignment G i r t y  the  Permian."  t o more d e f i n i t e h o r i z o n s 1  ob-  the  Nation River formation  o r , p o s s i b l y the G.H.  next  Gschelian f o s s i l s . . . .  by  upper Pennsylvanian  The  are  lower Permian.  states i n part:  "At p r e s e n t  t h e o n l y g r o u n d t h a t i s e v e n a p p r o x i m a t e l y s a f e i s t h a t we a p p a r e n t l y h a v e two d i s t i n c t f a u n a s b e l o n g i n g i n two d i s t i n c t horizons. One h o r i z o n i s the A l a s k a P e r m i a n ; the o t h e r i s older. U n f o r t u n a t e l y we know l i t t l e o r n o t h i n g a b o u t t h e s t r a t i g r a p h i c r e l a t i o n s of the C a i r n e s c o l l e c t i o n s . . . . . The t r u e p o s i t i o n s o f t h i s f a u n a i n t h e t i m e s c a l e . . must be l e f t t o f u t u r e i n v e s t i g a t i o n s . •... '»*•.••  H.  Upper White R i v e r The  district.  Carboniferous  s e c t i o n o f Upper White r i v e r  as  3 i s e v i d e n t l y q u i t e s i m i l a•r t o t h a t o f t h e examined by C a i r n e s Yukon-Alaska boundary n o r t h Carboniferous s e r i e s ' , and (a)  The  of limestone stones  I. 2. 3.  are  strata (b)  are  o f Yukon r i v e r .  described here:  'shale-limestone  limestone-chert with  500  feet  groups  of  (a)'limestone-chert  series'•  series  i s d e s c r i b e d as  some a s s o c i a t e d c h e r t s and  at l e a s t  Two  t h i c k and  shales.  dominantly The  100  a r e u n d e r l a i n by  G i r t y , G . H . - i n U.S.G.S. B u l l . 8 l b , pp.50-$S7~WW* Idem., p.53* C a i r n e s , D . D . - C.G.S. Mem.50, p p . 7 1 - 8 3 , 1915•  lime-  '  -95feet  of i r r e g u l a r (b)  The  and  distorted  shale-limestone  d a r k c h e r t s and  shales.  s e r i e s c o n s i s t s of s h a l e s , w i t h  some i n t e r b e d d e d l i m e s t o n e s , and m i n o r beds o f s a n d s t o n e and The r e l a t i v e p o s i t i o n o f beds i s n o t g i v e n .  conglomerate. series  h a s an e s t i m a t e d t h i c k n e s s o f a t l e a s t 1500 f e e t and  probably  3000 f e e t .  nearly The  s t r a t i g r a p h i e evidence be  slightly  Girty  into  obtained  o f the  stratigraphie  limestone-chert  does n o t  divisions  in  a g e n e r a l way,  to  the  lower  the  u n c e r t a i n and  as  considered  series.  but  considered to  Cairnes  entirely  states:  correspond  to  c h a r a c t e r of the  be  "The  the  r e p o r t , but  discrepancies being  indefinite  available  b e d s were d i v i d e d by  indicated i n this  apparent  the  series i s  group, both  or Pennsylvanian;  fossils  On  shale-limestone  from these  an u p p e r and  Upper Carboniferous grouping  the  o l d e r than the  Fossils G.H»  o f t h e s e r o c k s i s c h a r a c t e r i z e d by  structure  w i t h a general northwest s t r i k e .  close f o l d s  to  The  agrees  probably  due  invertebrate  remains." Certain r e d by  Girty  stone)  a t the  o f the  to the  fossils  limestone  mouth o f H a t i o n  ( t h e u p p e r g r o u p ) were  (now  known a s T a h k o n d i t  river.  River  formation  tentatively  of Yukon  In spite  of the  Boundary s e c t i o n n o r t h River d i s t r i c t ,  by  lime-  Also, certain plant  remains , c o l l e c t e d from s a n d s t o n e s i n the s e r i e s were r e f e r r e d  refer-  E.M.  shale-limestone Kindle  to  the  Hation  river. fact  t h a t , both  o f Yukon r i v e r  Carboniferous  and  formations  ciently well defined stratigraphioally  i n the  Alaska-Yukon  i n the Upper White are  not y e t  suffi-  or paleontologically  to  -96-  establish  definite  section of Alaska; ferring that exists  9  one c a n n o t  in all  three  study the l i t e r a t u r e  Kluane lake  sequence Pennsyl-  lower Permian.  and headwaters o f White  This region,  lying  river.  t o t h e s o u t h o f Upper White  h a s b e e n d e s c r i b e d by R.G. M o G o n n e l l . ^ great  terrestrial  Yukon  without i n -  r e g i o n s a somewhat s i m i l a r  embracing marine M i s s i s s i p p i a n ,  v a n i a n , and marine  I.  c o r r e l a t i o n s w i t h the Upper  direct  t r e n c h o c c u p i e d by K l u a n e l a k e  The m a i n f e a t u r e  and r i v e r .  The r o c k s o f t h i s  escarpment  escarpment a r e  c o n s i d e r e d b y M c C o n n e l l t o be l a r g e l y U p p e r P a l e o z o i c . iferous  f o s s i l s were f o u n d a t two p o i n t s ,  i s the  This i s  f l a n k e d on the southwest b y t h e s t e e p n o r t h e a s t e r n of the S t . E l i a s mountains.  river,  Carbon-  discussed as  follows: , 1-1.  Bullion The  green schists bands  creek.  Hear  general  139° W.,  section  of fragmental  described here c o n s i s t s o f  origin overlain  o f limestone , dark s l a t y  fossils  61° F*  by a l t e r n a t i n g  r o c k , and eherty  a r e mentioned as being  slate.  The  corals, but the horizon  from  w h i c h t h e y were t a k e n i s n o t g i v e n . 1-2.  Donjek r i v e r ,  Range.  Hear The  139°  between 45* W.,  section,  s o u r c e a n d emergence 61°  30* H.  o n a s c e n d i n g Donjek  by M c C o n n e l l a s c o n s i s t i n g  from S t . E l i a s  of:  river,  i s described  crushed r e d weathering lime-  1. M c C o n n e l l , R . G . - C.G.S. Sum.Rpt. 1904, p p . I - l b , 1905. - C.G.S. Sum.Rpt. 1 9 0 5 , p p . 1 9 - 2 6 , 1 9 0 6 . 2. M c C o n n e l l , R . G . - 1st R p t . c i t e d , p . 6 .  *  -97s t o n e , o v e r l y i n g g r a y i s h m a s s i v e l i m e s t o n e and s h a l e ; o v e r l a i n by f e l d s p a t h i c , t u f f a c e o u s , s a n d s t o n e a n d l i m e s t o n e c o n t a i n i n g C a r b o n i f e r o u s f o s s i l s , and i n t r u d e d b y d i o r i t e ; o v e r l a i n by m a s s i v e , g r e y l i m e s t o n e w i t h s l a t e s on t o p . 1  J.  Dezadeash l a k e  137°  d i s t r i c t , near  Dezadeash l a k e  l i e s i n the  v a l l e y ) as Kluane l a k e .  V/.  60°  t  30*  E".  same g r e a t v a l l e y  A g r o u p o f a r g i l l i t e s on  (Shawak  t h e west  side  2 of  the v a l l e y  ably  has  b e e n mapped by W.E.  a r g i l l i t e s are  places passing into glomerate  occur.  of  sediments,  to  occur  Alaska  but  to the  question-  c o a r s e l y bedded, i n  M i n o r bands o f q u a r t z i t e  thickness i s very great•  A  similar  c o n t a i n i n g metamorphosed l i m e s t o n e ,  southeast  i n Rainy Hollow  and  congroup  i s stated  d i s t r i c t near  the  boundary.  flicting,  lower  uncertain this  as t o  the  vicinity  evidence  the Porcupine  by  rocks i s r a t h e r  be  similar  but  were  south  containing  o f Dezadeash l a k e and  Canada-Alaska boundary. are  Fossils  s t a t e d by E a k i n  the R u s s i a n A r t i n s k i a n  found  t a k e n as d i a g n o s t i c . rocks  4  found  t o be  con-  as t h e l o c a l i t y  i n t e r v e n i n g Rainy Hollow d i s t r i c t )  district  r o c k s by W r i g h t ^  o f these  Tyrrell,  cannot  o t h e r hand, l i t h o l o g i c a l l y beds ( a s i n the  age  Paleozoic (Ordovician?) f o s s i l s  somewhere i n t h i s  1. 2. 3. 4.  d e s c r i b e d as  schists.  The  Evidence  the  as  Carboniferous. The  of  Cockfield  On  is the  limestone  a r e known i n just  i n the  south  latter  correlative  with  (lower Permian of A l a s k a ) .  M e C o n n e i l , R . G . - 2nd R p t . c i t e d , p . 2 2 . C o c k f i e l d . W . E . - C.G.S.Sum.Rpt.1927, P t . A , p . 5 , W r i g h t ,C.W.-. U.S.G.S. B u l l . 2 3 6 , p . l b , 1904. E a k i n , H.M.U.S.G.S. B u l l . 6 9 9 , p . H , 1?19.  and  map,  ~ 1928.  -98K.  Interior Two  localities ior  convenience  Lewes r i v e r  southern  of these  are  of  Yukon.  and  r o c k s a r e known a t many  i t s tributaries  i n the  For v a r i o u s reasons  i n c l u d e d here  d e s c r i p t i o n the  (a) Non-calcareous (b)  Yukon*  groups of sedimentary  along  part of  part  of Southern  with the  inter-  t o be  given,  Carboniferous.  For  groups are c l a s s e d ;  group.  Limestone.  (a) N o n - c a l c a r e o u s  group.  1 K-l.  T h i s g r o u p , a s mapped by  shown a s o c c u p y i n g and  Teslin  the g r e a t e r p a r t  lake s at the  consisting of cherty  British  i n 1899-1900, i s  Gwillem of the  r e g i o n between  C o l u m b i a - Y u k o n b o u n d a r y , and  quartzite, black slate,  limestone•  Some o f t h e  in origin.  Gwillim noted  gether with  the  c h e r t s was  limestones  Atlin  biotite  c o n s i d e r e d t o be  the resemblance o f these o f the  r e g i o n , to the  slate,  as and  pyroclastic rocks, to-  Cache  Creek  2 group of B r i t i s h K-2.  Columbia  limestones  igneous  The  i n part  Carboniferous  age  sediments (together with  rocks) with  Columbia. and  Cairnes considered these  of probable  non-calcareous  1. 2. 3.  Dawson.  S i m i l a r r o c k s were mapped a l o n g T a g i s h l a k e  C a i r n e s - ^ i n 1908.  ous  a s d e f i n e d by  the  and  rocks  to u n d e r l i e  correlated  the  associated basic  L o w e r Cache C r e e k g r o u p o f  L o w e r Cache C r e e k was  by  thought  t o be  British Carbonifer-  Devonian.  Gwillem,J.O.- C.G.S.An.Rpt.1899,Vol.XII,Pt.B,pp.l6-l8,1901. Dawson.G.M.- C . G . S . A n . R p t . 1 8 9 4 , V o l . ¥ I I , P t . B , p p . 3 7 " 4 9 • C a i r n e s , D . D . - C.G.S. R p t . 9 8 2 , p p . 2 6 - 2 0 , 1908.  Subsequently the n o n - c a l c a r e o u s lake) d i s t r i c t . consisting and  1  g a v e t h e name  'Taku g r o u p  The T a k u g r o u p i s d e f i n e d i n t h i s  mainly  o f c h e r t s and s l a t e s o f sedimentary (?) Braeburn  Cairnes  , b u t was c o r r e l a t e d  It  limestones.  the se n o n - c a l c a r e o u s  that l i t t l e  s c h i s t s and g n e i s s e s . to the lower  by  Cache  Yukon.  They a r e  thought  i n part o f Carboniferous age.  unconformably the Precambrian ( ? ) The l i t h o l o g y  o f t h egroup i s  (?) M i s s i s s i p p i a n  on the Yukon r i v e r  and the f a c t  I n view o f t h i s  have been c o r r e l a t e d w i t h t h e  Columbia  Carboniferous  strikingly  cherty sediments o f  o f Alaska.  t h a t they  p a r t o f the B r i t i s h  p l a c e d i n the  'lower  1  i s known o f t h e age o f  beds o f S o u t h e r n  They p r e s u m a b l y o v e r l i e  lower  08* W. , 6 l ° 48» ET.)  tentatively with  u n d e r l i e limestones, which are  similarity  s l a t e s , and  lake,  i s evident  Calico Bluff,  0  origin,  r i v e r was g i v e n t h e name 'Montague g r o u p  Creek' o f T a g i s h  similar  (I36  occurring at a locality  on N o r d e n s k i o l d  to  report as  A s m a l l arm o f c h e r t s , c h e r t y q u a r t z i t e s ,  argillites,  1  s e d i m e n t s i n t h e n e a r b y T a k u Arm ( o f T a g i s h  as underlying the Carboniferous  K~3.  to  Cairnes  Cache G r e e k g r o u p , now  a n d P e r m i a n , i t seems b e s t t o c o n -  s i d e r t h e group a s C a r b o n i f e r o u s .  (b)  limestone. To t h e t r a v e l l e r  and b l u f f s  on both  s i d e s o f the  feature o f the scenery.  1. 2.  on lewes r i v e r  Massive  route form  the limestone a  hills  conspicuous  developments o f limestone  C a i r n e s , D . I . - C.G.S. Mem.37, p p . £ 2 - 5 3 , 1912.' C a i r n e s C . G . S . Mem.3, p p . 2 7 - 2 8 , 1 9 1 0 .  -100ocour at  i n t e r v a l s from A t l i n  macks a t t h e are  drained  b e d s and  Teslin river,  "by the  e r o s i o n a l t r u n c a t i o n and some e v i d e n c e f o r m a b l e to critical  to  the  the  northwest  faulting  of  limestones,  however, has  i n part  to  the  this  i n part  The  dis-  limestone  l i e i n more  along  courses  the  revealed  There i s  at l e a s t , are 1  uncon-  Structure  o f the  of  by  structure.  sediments,  character  Gar-  limestones  outlying  been found d i f f i c u l t  massive  to  volcanics  l o w e r beds are  overlying Mesozoic  points,  p r e t , due part  that  Similar  i n various  s e d i m e n t s and  The  nearly  i t s tributaries.  or l e s s open f o l d s which s t r i k e Teslin rivers.  lakes  river.  and  Lewes and  o v e r l y i n g Mesozoic  Lewes and  Tagish  mouth o f N o r d e n s k i o l d  exposed a l o n g  tricts  and  to  at  inter-  beds and  in  these rocks  is  metamorphism. The  essentially  d e s c r i p t i o n s of the  the  same i n v a r i o u s  l i t h o l o g y of  widely  separated  districts,  2 Cairnes  describes  the  limestone  of A t l i n  district  in  the  following  words: " T h e s e l i m e s t o n e s a r e g e n e r a l l y f i n e l y t e x t u r e d and range i n c o l o u r from g r e y s i h b l u e to almost w h i t e . They a l s o v a r y f r o m sub c r y s t a l l i n e to c r y s t a l l i n e i n s t r u c t u r e , but a r e p r e v a i l i n g l y i n the s t a t e o f m a r b l e , and many s p e c i m e n s a r e h a n d s o m e l y a n d c u r i o u s l y m a r k e d w i t h g r e y and b l a c k l i n e s a n d spots. Some b e d s c o n t a i n c o n s i d e r a b l e s i l i c a and w e a t h e r r o u g h , and o c c a s i o n a l l a y e r s , p a r t i c u l a r l y n e a r t h e b o t t o m o f t h e s e r i e s , a r e composed l a r g e l y o f c h e r t y m a t e r i a l . These l i m e s t o n e s a r e o v e r 3»000 f e e t i n t h i c k n e s s , and a r e g e n e r a l l y h e a v i l y b e d d e d , and c o n s i d e r a b l y m e t a m o r p h o s e d , so t h a t i n o n l y rare cases are d e f i n i t e bedding-planes d i s t i n g u i s h a b l e . " I n the tion the  of the  drainage  o f Lewes r i v e r , w i t h t h e  beds a s s o c i a t e d w i t h  limestones  are  T. C o c k f i e l d , t f . E . & 2.  area  the  Precambrian (?)  mapped as u n d i f f e r e n t i a t e d .  fcell.A.H.-  C a i r n e s , D . J D . - C.G.S. Mem.37 ,  C.U.S. Mem.l^O, 1913.  The  p.12.  excep-  sediments, age  of  part  -101of  t i l l s g r o u p i s c o n s i d e r e d t o be C a r b o n i f e r o u s i n a l l p r o b a -  bility.  Fossil  evidence  b o n i f e r o u s , and p o s s i b l y evidence K-4.  i s listed 15'  134°  shows t h e p r e s e n c e  of Triassic,  Devonian h o r i z o n s .  Car-  The P a l e o z o i c  here: 60°  W.,  07* IT.  T a g i s h l a k e b e t w e e n Windy a n d  Taku Arms. In crinoidal  the limestone  remains  of this  ogy  The f o s s i l  The l i m e s t o n e was evidence,  c h e r t y q u a r t z i t e s and a r g i l l i t e s  134° 07*  60°  W.,  south of Michie A  135°  H.  c o n s i d e r e d t o be  w i t h h i s Cache British  Columbia.  o f Marsh l a k e and 5 m i l e s  East  mountain.  E.M. K i n d l e a s h a v i n g  K-6.  25*  species o f brachiopod  Probably belongs  found  the l i m e s t o n e and  C r e e k s e r i e s o f Thompson a n d F r a s e r r i v e r s , K-5.  Dawson  c o u p l e d w i t h the l i t h o l -  o f t h e r o c k s , l e d Dawson t o c o r r e l a t e  underlying  CM.  and a s p e c i e s o f F u s u l i n a ( r e f e r r e d t o  ' F u s u l i n a r o b u s t a , Meek*). Carboniferous.  vicinity  some  resemblance  to a Devonian  30* W. , 62°  found here  i s d e s c r i b e d by  t o 'Newberryia  laevis*.  fauna•  07* K.  lower  canyon o f l i t t l e  Salmon  river. One o f two f o s s i l s this  vicinity  i s referred  found  i n a band o f l i m e s t o n e i n  provisionally  to the Carboniferous. 3  The  genus i s t h o u g h t The  following  t o be  *Eapsiphyllum*.  l i m e s t o n e g r o u p has been d e s c r i b e d i n the  papers,  i n addition  to the ones a l r e a d y  1. Dawson,CM,- 0 . C S • R p t . 6 2 9 , 2. 3.  pp.1'69-170,  cited:  l B ? 8 , ( a n a map;.  C o c k f i e l d , W . E . & B e l l . A . H . - C.G.S. Mem.150, p . 1 3 , 1926. C o c k f i e l d , W . E . - C.G.S. Sum.Rpt. 1928, P t . A , p . 6 , 1929.  -102Gwillim, J.C. - " A t l i n  district",  C.G.S. A n . R p t . , V o l . X I I ,  Pt.B, pp. 16-18, 1901. Cairnes,  D.D*  - Conrad d i s t r i c t ,  C.G.S. R p t . 9 8 2 ,  pp.25-26,  1908. - lewes and N o r d e n s k i o l d R i v e r s d i s t r i c t ,  C.G.S.  5 , p p . 2 8 - 2 9 , 1910 ( u n d e r B r a e b u m l i m e ?  Mem.  stones/).  In a d d i t i o n probable ing  1*  to the areas  Carboniferous  d i s c u s s e d above, rooks o f  age h a v e b e e n d e s c r i b e d a t t h e f o l l o w -  localities:  129°  60°  W.,  3 0 ' H. ( a p p r o x . ) .  Frances  river.  S p e c i m e n s o f ' F u s u l i n a * w i t h p o l y z o a were f o u n d by 1  D a w s o n , who  considered that the limestones  together with canic  Finlayson  135°  M.  a s s o c i a t e d s h a l e s , c h e r t y q u a r t z i t e s , and v o l -  agglomerates,  description  c o n t a i n i n g them,  these  were o f G a r b o n i f e r o u s  rocks  appear to continue  age.  From Dawson's  northwest  to  lake.  30" W.,  Maomillan  62°  5 0 ' H. ( a p p r o x . ) .  South s i d e of lower  river.  Crinoid  stems were  found  b y R.G. M c C o n n e l l  i n lime-  2 stone  bluffs  sidered from  along  this  the limestone  the l i m e s t o n e s ,  part  o f the river*  t o be p r o b a b l y  Carboniferous.  1.  conApart  the c h e r t s , c h e r t b r e c c i a s , s l a t e s , and  q u a r t z i t e s which are e x t e n s i v e l y developed Maomillan  McConnell  appear to resemble  along  the Carboniferous  Dawson,G.M.- O p . c i t . , p p . 1 0 1 - 1 0 2 .  the l o w e r  rocks  *~  2. M c C o n n e l l , R . G . - C.G.S. Sum.Rpt. 1 9 0 2 , p . 2 9 , 1903*  o f the  -103Y u k o n - A l a s k a boundary. Cairnes.  N.  T h i s f e a t u r e h a s been n o t e d by D.D,  1  132° W., 61° 3 0  f  H. ( a p p r o x . ) .  P e l l y Mountains. •  The r o o k s o f t h e p a r t o f P e l l y M o u n t a i n s d r a i n e d by M s u t l i n r i v e r a r e d e s c r i b e d by McConnell  as c o n s i s t i n g o f  dark s l a t e s , g r e e n s c h i s t s , and l i m e s t o n e s .  C o r a l s and f r a g -  ments o f o t h e r f o s s i l s w h i c h a r e p r o b a b l y o f C a r b o n i f e r o u s age were found i n a l i m e s t o n e band n e a r t h e summit o f t h e r a n g e .  1. C a i r n e s , D . D . - C.&.S. Mem.67, p.103, 1914. 2. McConnell,R.G.- G.G.S.An.Rpt.1898,Vol.XI,Pt.A,pp.52-53,1901.  CHAPTER IV* THE MESOZOIC.  -104-  MES0Z0IC The known f a c t s g a t h e r e d up t o t h e y e a r 1926 r e g a r d ing  t h e M e s o z o i c s t r a t i g r a p h y o f A l a s k a have been summarized  and c o r r e l a t e d "by G.C. M a r t i n .  1  Reference to A l a s k a i n the  f o l l o w i n g d i s c u s s i o n o f t h e M e s o z o i c o f Yukon w i l l be p r i m a r i l ; through t h i s  authority.  TRIASSIC SYSTEM.  Fig.  11.  1. M a r t i n , G . C -  T r i a s s i c l o c a l i t i e s o f Yukon T e r r i t o r y . "The M e s o z o i c S t r a t i g r a p h y B u l l . 776, 1926.  o f Alaska," TT.S.G.S.  f o s s i l s h a v e "been f o u n d  Triassic i n Yukon T e r r i t o r y : and  L a b e r g e Lake  Upper Stewart A.  00»  1J4°  upper Stewart  river, Little  Tentatively  basis of  64°  16»  N.  Forks  o f Rackla  p l a c e d as T r i a s s i c  this  "Since then  area there  S t e w a r t , and  has  enfolded with  sandstones,  quartzites.  mountains, O g i l v i e  T  1  as  of  On  the  area  Triassic.  r e p o r t he  Men-  stated:  these  rocks  remnant o f T r i a s s i c  Paleozoic  t o M a r t i n (p.128)  *Pseudomonotis  i n a bed  to b e l i e v e that  limestones,  •Pseudomonotis s u b c i r c u l a r i s *  Pacific  and  a small  The  grits, slates,  The  by K e e l e  mapped a c o n s i d e r a b l e  been r e a s o n  them."  According  Alaska.  Whiteaves.  Beaver r i v e r s  that only  river.  'Arpadites.•  of sediments i n a l a t e r  a r e P a l a e o z o i c , and was  argillites  information Keele  between L a n s i n g , tioning  by  f o s s i l s a b o v e were f o u n d  associated with this  river,  river.  •Monotis subcircularis.* 'Halobia Xommelli.* •Ammitoid s h e l l s i m i l a r t o  limestone  Salmon  area*  W.,  The  at three l o c a l i t i e s  rocks mentioned  and this  some fauna  rocks are  volcanics. belongs to  zone or h i g h e s t Upper T r i a s s i c h o r i z o n i s w e l l known i n  range  the of  the  ( R o c k y m o u n t a i n s ) , and  Brooks  range o f A l a s k a .  Little B.  Salmon  1J5°  30*  river. W.,  M c L e a r n t o be  62°  Ob  1  N.  S p e c i m e n s d e t e r m i n e d by  'Pseudomonotis s u b c i r c u l a r i s  1. K e e l e . J . - G.G.S. A n . R p t . V o l . X v I , 2. K e e l e J . - C.G.S. R p t . 1 0 9 7 , p.39, 9  pt.C, 1910.  F.H.  ?' were f o u n d  p . l b , 190 6.  by  -10fe~ W.E,  Cockfield  i n an o u t c r o p  canyon o f l i t t l e was  also  river  found  from  the  argillite  a Mesozoic  (Triassic  seems p r o b a b l e  Salmon r i v e r  lower h o r i z o n than relation be  o f the  Laberge Lake The  the  coral  This  t h a t p a r t o f the but  undifferentiated limestones  Lewes R i v e r r e g i o n . n o r t h o f the  was  argillite.  lake  limestone  Carboniferous  some e v i d e n c e  the b e l i e f  limestone  i n the  that of  they the  i s Triassic  Laberge area  lacking  series  lake  t h a t p a r t , i f not in  clastic  age.  i s d e s c r i b e d as  bedded p l a n e s ,  d e s c r i b e d as a r g i l l i t e s  t h i c k n e s s o f the  System."  i n the o l d e r surveys  o f l i m e s t o n e , s e p a r a t e d by  members a r e  total  thought  i n v e s t i g a t i o n s around Laberge  confirms  l a r g e l y m e t a m o r p h o s e d and  The  The  o f Lewes R i v e r b a s i n  "Carboniferous  although  found  Recent  the g r e a t e r p a r t , o f t h i s  clastic  of  area.  were i n p a r t T r i a s s i c  divisions  is  found.  a number o f p u b l i c a t i o n s ,  The  coral  r e p r e s e n t s a somewhat  These l i m e s t o n e s have been c l a s s e d as p r o b a b l y  and  was  limestone  beds to nearby conglomerate,  have been d e s c r i b e d , i n p a r t , under  in  the  the  1  Pseudomonotis-bearing  not  lower  'Isastrea?"  limestone  ? i n p a r t , hut  i s Upper T r i a s s i c  Triassic  J u r a s s i c , was  exposure.  form.  i n the  h a n d a s h o r t d i s t a n c e up  Carboniferous ?)  argillite  A single  i n a limestone  t o he  Little  to  Salmon r i v e r ,  determined  It  o f dark  Two  o r more  beds, occur. and  i s estimated  The  greywackes. t o be  in  excess  1. C o c k f i e l d . W . K . - C.G.S.Sum.Rpt. 1928 , P t . A , p . b , I ? 2 9 . ' 2. C o c k f i e l d , W . E . & l e e s , E . J . - T r a n s . R o y . S o c . C a n . , S e c t . I V , 3 r d s e r . , V o l . X X V , pp.101-104, 1931*  -io?o f 4000 f e e t , a n d The  f o l l o w i n g Upper T r i a s s i c  fossils  found  graphic  location  G.  2000 t o 3000 f e e t i s  of t h i s ,  135°  i n both  61°  W.,  the  stages  are  d e f i n e d from  limestone  and  elastics  r e f e r s to the  30*  N.  limestone.  centre  East, north,  o f the  (the  area  geo-  described).  northwest  and  the  of  laberge  Lake. "Koric..•  Pseudomonotis zone.... Pseudomonotis s u b c i r o u l a r i s Gabb. C o r a l zone I s a s t r e a c f . vancouverens i s C l a p p and Shimer and other fragmentary c o r a l s . New s p e c i e s o f V a r i a m u s i u m and a sponge c f . S t e i n m a n i a u t r i c u i u s Regny. K a r n i c . . . J u v a v i t e s zone Juvavites subinterruptus Mo j s . Halobia omatissima S m i t h . "1 The  observed. Laberge  bottom o f these  General  relations  end  and  the  Middle  Upper T r i a s s i c  rocks  parts of Alaska  eroded surface  are w i d e l y  occupied  Mountain systems.  by  of  the  at the  distributed  Plateau  region.  & Lees.E.J.-  western  throughout  0 are  Op.cit.,  i n the  p.103.  p.12?)  those  Rocky ( O g i l v i e ) ,  I n Yukon, l o c a l i t y A l i e s B and  and  t o M a r t i n (p.119 and  the P a c i f i c ,  mountains, l o c a l i t i e s  Cockfield,W.E.  i s known o n l y  According  Ogilvie  1.  an  overlying  s e d i m e n t s a r e unknown i n Y u k o n  Triassic  o f Seward P e n i n s u l a .  Arctic  on  not  sediments.  Lower T r i a s s i c Alaska,  b e d s was  i n d i c a t e t h a t the  ( J u r a s s i c ) beds r e s t  Triassic  Upper T r i a s s i c  near  Interior  and the  -108-  F i g . 12.  T r i a s s i c l o c a l i t i e s o f Alaska ( a f t e r Martin). The Yukon l o c a l i t i e s a r e a l s o shown. The dotted l i n e i n d i c a t e s the northern l i m i t of T r i a s s i c ( o r Permian) v o l c a n i c s .  -109I n Yukon J u r a s s i c near the A r c t i c  Ocean*  r o c k s a r e known o n F i r t h  Jurassic  sediments, with  members, a r e a l s o w i d e l y d i s t r i b u t e d s o u t h e r n Yukon, east  Firth  volcanic  i n the i n t e r i o r  o f the C o a s t Range  river,  region of  mountains.  river. I n 1914  d i s t a n c e o f 50 reports"*  -  J . J . O'Neill  explored F i r t h  river  m i l e s f r o m i t s mouth on t h e A r c t i c  the f o l l o w i n g  for a  coast.  s e c t i o n (abbreviated here) :  In descending  order.  Grey s h a l e s , t h i n beds o f s a n d s t o n e , c h e r t l e n s e s . In places schistose. Middle J u r a s s i c f o s s i l s 100 Massive , r u s t y conglomerate 20 Chert i n massive beds • •. 50 Green s c h i s t , g r e y s l a t e s , r e d and brown s h a l e s 300 Grey s h a l e s , sandstone » conglomerate .100 T h i n - b e d d e d l i m e s t o n e , c h e r t s , and some s a n d s t o n e . . • 40 • 20 Sandstone , w i t h c h e r t pebble conglomerate Thin-bedded shale and q u a r t z i t e 20 B l a c k s h a l e , c h e r t , and r e d c o n g l o m e r a t e 20 Cherts 75 Massive quartzite 200 C o a r s e s a n d s t o n e and s a n d y s h a l e 75 t o 150 S a n d s t o n e and s h a l e 100 B l a c k , massive l i m e s t o n e ; base not o b s e r v e d . No the  u n c o n f o r m i t i e s were o b s e r v e d i n t h i s  c o n t a c t s below  member were n o t  the h i g h e s t  seen.  The  member a n d  extend a l o n g the e n t i r e A r c t i c  A.  i n age  1 4 0 ° W., The  from Devonian to 69°  fossils  N.  feet. 11  " " 18  ,(  " '.! " '! !! !•  s e c t i o n but  lithologically  i t i s probable that  f a c e o f the Brooks  range  they and  Jurassic.  river,  exact l o c a l i t y not  c o l l e c t e d b e l o n g to t h e genus  most s a t i s f a c t o r y i.  Firth  and  + + + + + + +  above t h e l o w e s t  s t r a t a , however, are  s i m i l a r t o measures f a r t h e r west  range  He  identification  being  O'Neill,«J • J . - R p t . C a n . A r c t i c E x p e d .  given.  "Cadoceras", the  "Cadoceras  sublaere*  1913-18, V o l . X I , p t . A , p p . 1 2 - 1 5 , 1924.  -110-  The f a u n a i s n o t c o r r e l a t i v e w i t h A l a s k a n h o r i z o n s h u t i s c o n s i d e r e d b y Buckman t o be about e q u i v a l e n t t o t h e M i d d l e 1  o f North America*  Jurassic  S o u t h e r n Yukon, Laberge  and T a n t a l u s  series  conglomerate*  As known a t p r e s e n t t h e J u r a s s i c l a b e r g e s e r i e s i s c o n f i n e d t o t h e a r e a d r a i n e d by l e w e s r i v e r and i t s t r i b u t a r ies*  These s t r a t a a r e r e s t r i c t e d t o t h e e a s t s i d e o f t h e Coast  r a n g e , a r e known as f a r e a s t a s T e s l i n r i v e r , and may e x t e n d a considerable  distance  farther  to the e a s t .  l e s s open f o l d s t r e n d i n g n o r t h w e s t . series about  extends from A t l i n lake 180  They  l i e i n more o r  A l o n g the s t r i k e  the  to Tatchun r i v e r , a distance  of  m i l e 8 i n Yukon. The  laberge series  has been  d e s c r i b e d i n some d e t a i l  2 by C o c k f i e l d  and B e l l .  l i t h o l o g i c a l l y the beds  are  o f a r g i l l i t e , shale , sandstone, a r k o s e , greywacke, conglomerate• The  shale  stone .  The  series also  The  series.  becoming  some t h i n  tuff, coal  t u f f s are both massive  They  and b e d d e d ,  Conglomerates  a r e most abundant  progressively  less  form a c o n s p i c u o u s p a r t near to the Coast  so f a r t h e r  i n a conformable s e r i e s .  ed c o n s i s t to  east.  The  t h e C o a s t Range g r a n o d i o r i t e ) , 1  conglomerate  Cockfield,W.E. & Bell,A.H.=  definite report-  ( i d e n t i c a l i n composition  tuffs, quartzite,  Rpt. c i t e d , p . I J T "  of  range,  p e b b l e s and b o u l d e r s  of andesite , granodiorite  1. O ' N e i l l , J . J . 2.  The  sand-  and g r a d e i n  appears to occur i n i r r e g u l a r l e n s e s r a t h e r than as beds  and  seams.  i s t h i n - b e d d e d and a s s o c i a t e d w i t h a r k o s e and  p l a c e s to greywackes. the  contains  composed  ~  —  ~  and  ~~  C.G.S.Mem.150, p p . 1 4 - 2 3 ,  ~" 1926.  -Illlimestone. The t h i c k n e s s o f t h e Laberge s e r i e s i s n o t known. The g r e a t e r p a r t o f the s e r i e s i s composed o f t u f f s ; much o f the sandstone i s t u f f a c e o u s .  The Laberge s e r i e s i s , t h e r e f o r e ,  e s s e n t i a l l y o f v o l c a n i c o r i g i n , and i t w o u l d be e x p e c t e d the s t r a t a t h i c k e n and t h i n somewhat r a p i d l y . district  that  I n Wheaton  the t h i c k n e s s was e s t i m a t e d t o be 5000 t o 6000 f e e t .  The f o l l o w i n g s e c t i o n i s known i n Wheaton d i s t r i c t .  1  Tantalus  conglomerate: conglomerate, s h a l e , sandstone, and c o a l . . ,. 1800 f e e t . Laberge s e r i e s : Upper beds: c h i e f l y s a n d s t o n e , . . , , 1500 " M i d d l e beds: s h a l e s j s a n d s t o n e , arkose 1700 Lower beds: a r k o s e and t u f f s w i t h ,• s h a l e s and conglome r a t e s . . . . . . . . . . . . . . . . 1800 " ,s  Bast  o f Lewes r i v e r t h e Laberge s e r i e s a p p e a r s t o be somewhat  thicker. The T a n t a l u s  c o n g l o m e r a t e i s a s w i d e l y d i s t r i b u t e d as  the Laberge b e d s , but h a s s u f f e r e d g r e a t l y from e r o s i o n ,  The  exposures are few, r e l a t i v e l y s m a l l , but w i d e l y separated. type a r e a i s a t the mouth o f B b r d e n s k i o l d r i v e r .  The  At t h i s 2  l o c a l i t y t h e conglomerate was d e s c r i b e d by C a i r n e s  as c o n s i s t -  i n g o f pebble8 and b o u l d e r s , r a r e l y more than 3 o r 4 i n c h e s i n diameter,  composed o f q u a r t z i t i c , c h e r t y , and s l a t y r o o k .  The  m a t r i x n e a r the t o p o f t h e f o r m a t i o n i s s i l i c e o u s , and n e a r the bottom a r g i l l a c e o u s . The f o r m a t i o n a l s o c o n t a i n s minor sandstone beds and c o a l seams.  A t the type l o c a l i t y  Cairnes  e s t i m a t e d t h e t h i c k n e s s t o be a t l e a s t 1000 f e e t . A s i m i l a r c o a l - b e a r i n g format i o n was d e s c r i b e d by 1. C o c k f i e l d , W . E . & BeTl,A.H.- O p . c i t . , p . l 5 . 1926T"" 2. C a i r n e s , D . D . - C.G.S. Mem.5, p p . 3 5 - 3 8 , 1910.  -112Cairnes and  i n Windy Arm  again  o f the The  f r o m the ranging  1  (as part of h i s Tutshi s e r i e s )  i n Wheaton R i v e r d i s t r i c t  t h e name T a n t a l u s  Age  district  best  s e r i e s and  evidence  o f the  at  two  nearby  m o u n t a i n and  these  at. Mr.  fossils  Pacific  ammonoids l i s t e d  argue 1.  2. 3. 4. 5.  by  the  that t h i s  parts of  occur  fossil  southern  C a i r n e s , D . D . - G.S.C. R p t .  Middle  localmay  Alaskan  Jurassic strata i n the  peninsula. f r o m the  laberge  Y u k o n , C o c k f i e l d and supports  pp.31-36,  190b.  - G.S.C. Mem.31, i>p.57-39,  1912. 1913* p.21.  "  in  as e x i s t i n g  evidence  evidence 982,  not  - G.S.C. Mem.37 , p p . 6 3 - 6 4 , C o c k f i e l d , W . E . & B e l l , A . H . - Op. c i t . , Idem., p p . 2 1 - 2 2 .  "  strata  above do  i n Alaska  less definite  laberge  above.  e q u i v a l e n t l o w e r and  M o u n t a i n r e g i o n and  f r o m o n l y two  limits given  by M a r t i n ( o p p o s i t e p.270)  i n other  following  4 Buckman:  were c o l l e c t e d  In a d i s c u s s i o n of series  The  Haugia ? Harpoceras. Elegantuliaras. Amaltheus s e q u e n z i c e r a s . Prodactyliooeras.  c o n s i d e r a b l y b e y o n d the  c o l l e c t i o n s , but  S.S.  22* I .  60°  lansdowne.  by  time range r e p r e s e n t e d  recorded  localities:  60° 26* N. a n d 1 3 4 ° 32* W.,  Pleydellia. Dumortieria. Phlyseogrammoceras. Pseudogrammoceras. Grammoceras.  are  series i s  Middle  W.,  The  of the l a b e r g e  lower  g e n e r a have been i d e n t i f i e d  extend  age  conglomerate.  from middle lower J u r a s s i c to  40*  the  under  fossils  B.  ities  3  where  have been found  As  district  district  Jurassic  Hear Lome  Atlin  Tantalus  e a s t e r n part of Whitehorse  134°  and  conglomerate.  laberge  i n age  2  Bell  the view t h a t '  ~"  ~113°  t h e s e s t r a t a are l o w e r and M i d d l e  Jurassic.  In the K o r d e n s k i o l d R i v e r area the f o s s i l s  were  r e g a r d e d by W h i t e a v e s as J u r a s s i c o r C r e t a c e o u s : G.  136  W,,  61  25* N.  H e a r Vowel m o u n t a i n and a t o t h e r  localities* T r i g o n i a dawsoni. N e r i n o e a maudensis. Rhynchonella orthidoides. A c c o r d i n g to C o c k f i e l d and B e l l ,  "two  i f not a l l 1  t h r e e o f t h e s e s p e c i e s are now ' R h y n c h o n e l l a * and J u r a s s i c 'Tuxedni  r e g a r d e d as J u r a s s i c  ' T r i g o n i a dawsoni' sandstone'  forms."  a r e found i n the M i d d l e  o f Cook I n l e t , A l a s k a ( M a r t i n ,  pp.150-151). From the d e s c r i p t i o n s the T a n t a l u s appears  conglomerate  to o v e r l i e the l a b e r g e s e r i e s c o n f o r m a b l y .  The  fossil  e v i d e n c e r e g a r d i n g the age o f the f o r m a t i o n has come from districts: D. 135° 10'  W.,  60° 15'  H.  two  Wheaton R i v e r d i s t r i c t . 2  F o s s i l p l a n t s c o l l e c t e d by C a i r n e s  i n this district  the T a n t a l u s beds were r e f e r r e d by F.H. Jurassic. E.  136° 16'  The W.,  names or l o c a l i t i e s  62° 06'  of H o r d e n s k i o l d  H.  Knowlton  from  to the  o f these are not g i v e n .  T a n t a l u s Goal mine, near the mouth  river. 3  F o s s i l p l a n t s c o l l e c t e d here were r e f e r r e d by P e n h a l l o w ' T h y r s o p t e r e s e l l i p t i c a , F o n t a i n e ' as f i g u r e d by Ward. 1. 2. 3'  i s n o t e d , however, t h a t some doubt e x i s t s as to the C o c k f i e l d , W . 3 . cc B e l l , A . H . - Op. c i t . , p. 21. Cairnes,D.D.- C.G.S. Sum.Rpt. 1913, p.41, ]916 " " - C.G.S. Mem.5, p.38, 1910.  to It  -114c o r r e c t n e s s o f Ward's o r i g i n a l r e f e r e n c e . M  further: A  somewhat r e l a t e d f l o r a was  Penhallow  notes  d e s c r i b e d by me  in  I898 as o b t a i n e d by Mr. J.B. T y r r e l l from N o r d e n s k i o l d river.  A l l the specimens shown, however, were specimens o f  C l a d o p h e b i s , and t h e y i n d i c a t e d C r e t a c e o u s The  evidence  age."  c i t e d above i s somewhat c o n f l i c t i n g .  The more r e c e n t d e t e r m i n a t i o n i s f a v o r e d by C o c k f i e l d and who  Bell  state: "The  p l a n t evidence  ...... seems to c o r r o b o r a t e the  a n i m a l e v i d e n c e o b t a i n e d from the l a b e r g e beds, end t h e r e be l i t t l e  doubt t h a t the l a b e r g e beds and T a n t a l u s  are b o t h o f J u r a s s i c age,  conglomerate  and i t would appear t h a t the  d e t e r m i n a t i o n s o f f o s s i l s are to be r e g a r d e d  as  earlier  extremely  d o u b t f u l i n the l i g h t o f the more e x a c t e v i d e n c e now  presented."  F i g . 14. J u r a s s i c l o c a l i t i e s o f A l a s k a ( a f t e r M a r t i n ) The Yukon l o c a l i t i e s are a l s o shown.  TTTockfiTld.W.S.  & Bell,XH7~"0p.cit.,  p.23.'  can  -115-  Older V o l p a n i c s . I n s o u t h e r n and w e s t e r n Yukon t h e r e are e x t e n s i v e areas o f v o l c a n i c r o c k b e l i e v e d to "be l a r g e l y o f M e s o z o i c These r o c k s i n t r u d e the P r e c a m b r i a n  ( ? ) metamorphics, a r e i n  p a r t i n t i m a t e l y a s s o c i a t e d w i t h the l a b e r g e s e r i e s , and as i n c l u s i o n s i n the M e s o z o i c  g r a n i t i c rocks.  map  occur  They show the  n o r t h w e s t e r n t r e n d w h i c h i s so c h a r a c t e r i s t i c o f the sediments.  age.  The known d i s t r i b u t i o n i s shown on the  Mesozoic  geological  ( i n pocket). l i t h o l o g i c a l l y these Older v o l c a n i c s v a r y c o n s i d e r -  ably.  They i n c l u d e a n d e s i t e s , d i o r i t e s , d i a b a s e s , and  w i t h a s s o c i a t e d , more deep-seated c a s e s , w e l l advanced.  rock.  basalts,  A l t e r a t i o n i s , i n many  Much o f the v o l c a n i c group shows a t e n -  dency towards greenstone  habit.  Where i n t r u d e d by  r o c k the v o l c a n i c s o f t e n show a w e l l - d e v e l o p e d  granitic  c l e a v a g e and  are  o f t e n q u i t e s c h i s t o s e . A l o n g the l o w e r p a r t o f l e w e s r i v e r  the  v o l c a n i c s d i p i n t o the i n t r u s i v e s , the r e s u l t , p r o b a b l y ,  of  w r a p p i n g around the b a t h o l i t h i c c u p o l a s d u r i n g i n t r u s i o n . V a r i o u s names have been a p p l i e d t o t h i s group o f rocks.  In Hordenskiold d i s t r i c t Cairnes divided corresponding  v o l c a n i c s i n t o two  groups;  the ' H u t s h i g r o u p ' and  'Schwatka  1  andesites'.  He found  t h a t b o t h i n t r u d e d the Laberge s e r i e s  and T a n t a l u s c o n g l o m e r a t e , one p e r i o d of v u l c a n i s m . c l u d e d the two  and  considered that they represented  l a t e r , i n Wheaton R i v e r a r e a , he i n -  groups under the name ' C h i e f t a i n H i l l  volcanics  and c o n s i d e r e d t h e i r f o r m a t i o n to be i n p a r t contemporaneous 1.  Cairnes,D.I).- C.G.S. Mem.5, pp.38-43,  1910.  T  -11bw i t h the d e p o s i t i o n o f the Xiaberge and T a n t a l u s beds.  Final-  l y , C a i r n e s grouped t h e s e v o l c a n i o s w i t h h i s ' O l d e r v o l c a n i c s * 2  o f upper White R i v e r  district.  I n upper White R i v e r d i s t r i c t C a i r n e s p o s t u l a t e s t h a t t h e O l d e r v o l c a n i c s i n c l u d e members r a n g i n g i n age from Pennsylvanian to Cretaceous,  I n A l a s k a v o l c a n i c rocks which  mark the P e n n s y l v a n i a n ( o r e a r l y Permian) - Upper T r i a s s i c i n t e r v a l are w e l l d e v e l o p e d  south o f the A l a s k a range h u t are  not known n o r t h o f the range ( M a r t i n , p.476).  I t therefore  seems p r o b a b l e t h a t p a r t o f the O l d e r v o l c a n i c s o f the N u t 2 0 t i n mountains i s P e r m i a n o r T r i a s s i c . i n t r u d e Cretaceous part Cretaceous,  These r o c k s a l s o  sediments, so they probably are a l s o i n No v o l c a n i c s w h i c h are d e f i n i t e l y  are known i n A l a s k a ( M a r t i n , p.477)•  Cretaceous  A l t h o u g h some o f t h e  O l d e r v o l c a n i c s o f White r i v e r may be C r e t a c e o u s , as C a i r n e s p o i n t s o u t , i t seems p r o b a b l e t h a t t h e y a r e f o r the most p a r t Jurassic. I n Yftiitehorse d i s t r i c t , w h i c h , i n v i e w o f C a i r n e s " c o r r e l a t i o n s , may be t a k e n t o be r e p r e s e n t a t i v e 0 f the g e n e r a l r u n o f t h e s e v o l c a n i c s i n the s o u t h e r n i n t e r i o r o f Yukon, the problem  i s summarized b y C o c k f i e l d and B e l l as f o l l o w s :  "The O l d e r V o l c a n i c s a r e , p r o b a b l y , a l l o l d e r t h a n t h e g r a n i t i c i n t r u s i v e s . A l t h o u g h some o f t h e f l o w s are more r e c e n t t h a n the beds o f the l a b e r g e s e r i e s w i t h w h i c h t h e y come i n c o n t a c t , the w r i t e r i s o f the o p i n i o n t h a t t h e y are t o a l a r g e e x t e n t contemporaneous w i t h the l a b e r g e beds, and a r e p r o b a b l y o f l o w e r and M i d d l e J u r a s s i c age; and t h a t t h e t u f f s , w h i c h are so p l e n t i f u l i n the Laberge s e r i e s , a r e t o be a t t r i buted t o t h e same p e r i o d o f v u l c a n i s m . " * 1. Cairnes,D.D".- C.G.S. Mem.31, p.64, 1912. ~ 2. " " - C.G.S. Sum.RIDt. 1913, pp.41-42, I916. 3. " " - C.G.S. Mem.50, p.93, 1915. 4. C o c k f i e l d , W . S . & B e l l , A . H . - O p . c i t . , p.29.  "  '  A s i m i l a r v i e w was h e l d b y G w i l l i m rocks i n A t l i n Granitic  1  f o r corresponding  district.  Intrusives, The r o c k s o f p l u t o n i c o r i g i n d i s c u s s e d h e r e a r e those  w h i c h a r e thought t o be J u r a s s i d e •  They i n c l u d e t h e Coast  Range i n t r u s i v e s as w e l l as g r a n i t i c r o c k s i n o t h e r p a r t s o f Yukon.  The l a t t e r , f o r t h e most p a r t , have g e n e r a l l y been con-  s i d e r e d t o be c o r r e l a t i v e w i t h t h o s e o f t h e Coast r a n g e , s u c h c o r r e l a t i o n b e i n g based on l i t h o l o g i c a l s i m i l a r i t y and l a c k o f c o n f l i c t ing evidence• That p a r t o f the Coast Range composite  batholith 2  which e x t e n d s i n t o Yukon has been d e s c r i b e d by W.E.  Cockfield.  The main mass o f t h e b a t h o l i t h c o i n c i d e s f a i r l y c l o s e l y w i t h the Coast Range m o u n t a i n s , w h i c h merge w i t h the Yukon p l a t e a u near K l u a n e  lake.  The t y p i c a l r o c k i s medium t o c o a r s e g r a i n e d , com posed u s u a l l y o f l e s s t h a n 20% q u a r t z , a l k a l i and s o d a - l i m e f e l d s p a r s i n about e q u a l amounts, and b i o t i t e or h o r n b l e n d e or both.  The average r o c k , t h e r e f o r e , can be c l a s s e d a s monzonite  or g r a n o d i o r i t e . a r e a l importance.  True g r a n i t e s a l s o o c c u r , but a r e o f minor Rocks more b a s i c t h a n q u a r t z - d i o r i t e  appear  to be o f v e r y l i m i t e d o c c u r r e n c e ; t h e y a r e n o t mentioned i n most d e s c r i p t i o n s o f the Coast Range i n t r u s i v e s o f Yukon.  Nor  does t h e r e appear t o be any phase w h i c h c a n be c l a s s e d as c h a r a c t e r i s t i c a l l y marginal. The w e s t e r n c o n t a c t has n o t been c l o s e l y s t u d i e d but 1. G w i l l i m , J.C.- C.G.S. An.Rpt., v o l . X I I , P t . B , p.28". 2. C o c k f i e l d , W . E . - C.G.S. Sum.Rpt.19 26, p t . A , pp.6-10, 1927.  -118i s thought t o he g e n t l y s l o p i n g .  The e a s t e r n c o n t a c t i s  f a i r l y w e l l known, hut c o n s t i t u t e s a d i f f i c u l t problem.  The  known f a c t s s u g g e s t t h a t i n Yukon "the e a s t e r n m a r g i n o f the b a t h o l i t h s l o p e s g e n t l y e a s t w a r d w i t h r e c u r r e n t upward p r o j e c 2  tions..."  G r e a t b o d i e s o f g r a n i t i c r o c k o c c u r between P e l l y ,  N i s i i n g , and White r i v e r s ( s e e g e o l o g i c a l map i n p o c k e t ) , and the p r e s e n c e o f t h e s e s u g g e s t s t h a t the g r e a t e r p a r t of s o u t h w e s t e r n Yukon i s u n d e r l a i n by a g r e a t i n t r u s i v e o f a character.  composite  Stocks of g r a n i t i c rock also occur a t v a r i o u s  l o c a l i t i e s throughout  the i n t e r i o r r e g i o n s o u t h o f O g i l v i e  mountains. I t i s q u i t e e v i d e n t t h a t the g r a n i t i c i n t r u s i v e s o f Yukon embody a number o f d i f f e r e n t phases w h i c h p r o b a b l y r e p r e s e n t a c o n s i d e r a b l e range i n age.  Boulders o f g r a n o d i o r i t e  o c c u r i n t h e l o w e r and M i d d l e J u r a s s i c l a b e r g e s e r i e s ,  indica-  t i n g t h a t p r e - J u r a s s i c i n t r u 3 i v e s e x i s t i n the Yukon r e g i o n . The Coast Range i n t r u s i v e s c u t the Laberge  s e r i e s and O l d e r  v o l c a n i c s : C a i r n e s was o f the o p i n i o n t h a t the i n t r u s i v e s were 3 younger t h a n the T a n t a l u s conglomerate  , but as the age o f the  l a t t e r i s u n c e r t a i n t h e age o f the i n t r u s i v e s cannot definitely fixed.  be  The known f a c t s i n d i c a t e t h a t the main mass  of t h e Coast Range b a t h o l i t h i n Yukon r e p r e s e n t s m o u n t a i n b u i l d i n g w h i c h p r o b a b l y l a s t e d d u r i n g Upper J u r a s s i c and a cons i d e r a b l e p a r t of Cretaceous time. S i m i l a r age r e l a t i o n s h i p s a r e shown by the g r a n i t i c 1. C o c k f i e l d , W . E . - C.tf.S. Sum.Rpt.1927, p t . A , p.6, 1928. 2. C o c k f i e l d , W . E . - C.G.S. Sum.Rpt.1926, p t . A , p.10. 3. C o c k f i e l d , W . E . & B e l l , A . H . - O p . c i t . , p.32.  -119i n t r u s i v e s o f upper White r i v e r .  Here, c o n g l o m e r a t e s o f the  Mesozoic sediments c o n t a i n g r a n i t i c pebbles; which a r e p a r t l y Lower C r e t a c e o u s , rock.  and the s e d i m e n t s ,  are i n t r u d e d by g r a n i t i c  The i n t r u s i v e s i n t h i s r e g i o n a r e more p r e v a i l i n g  dior-  i t i c t h a n those o f the Coast Range p r o v i n c e o f Yukon, where i n t e r m e d i a t e and g r a n i t i c t y p e s p r e v a i l .  They t h e r e f o r e may  r e p r e s e n t a l o c a l p h a s e , p o s s i b l y o f Laramide a f f i n i t y .  The  g e n e r a l absence o f known C r e t a c e o u s d e p o s i t s i n the i n t e r i o r Yukon s u g g e s t s  t h a t the g r a n i t i c b o d i e s i n t h i s r e g i o n may be  C r e t a c e o u s o r L a r a m i d e i n age. I n the A l a s k a range t h e g r a n i t i c r o c k s have g e n e r a l l y been r e g a r d e d  as J u r a s s i c or C r e t a c e o u s ,  although  i n recent  y e a r s many o f the a r e a s f o r m e r l y c o n s i d e r e d t o be J u r a s s i c have been p l a c e d i n t h e T e r t i a r y .  J u r a s s i c sediments have not been  found i n i n t e r i o r A l a s k a , a f a c t w h i c h s u g g e s t s the b o d i e s  t h a t many o f  o f i n t r u s i v e r o c k i n t h i s r e g i o n may be J u r a s s i c ,  J.B. M e r t i e has demonstrated t h e p r e s e n c e o f a l o w e r  Devonian  g r a n i t e ( i n p e r t g n e i s s i c ) i n the C h a n d a l a r d i s t r i c t , n o r t h o f 2  Yukon r i v e r . The g r a n i t i c g n e i s s e s a s s o c i a t e d w i t h the P r e c a m b r i a n r o c k s o f Yukon and A l a s k a have a l r e a d y been d i s c u s s e d .  CRETACEOUS SYSTEM. C r e t a c e o u s r o c k s a r e known i n Yukon T e r r i t o r y ; of O g i l v i e m o u n t a i n s , on P e e l and P o r c u p i n e  north  r i v e r s ; and a l o n g  1. Cairnes,D.D.- C.^.^. Mem.50, p.95, I 9 I 5 . 2. M e r t i e , J . B . J r . - U.S.G.S. B u l l . 7 7 3 , pp.243-244, I925.  -120-  the Y u k o n - A l a s k a boundary, n o r t h o f Yukon r i v e r , upper White  river.  F i g . 15. Yukon-Alaska A.  141° W.,  and  C r e t a c e o u s l o c a l i t i e s o f Yukon.  boundary. between 65° 40* and 66° 00* N.  International  boundary n o r t h o f Sitdown c r e e k . Specimens  o f A u c e l l a were c o l l e c t e d by D.D.  i n t h i s v i c i n i t y and r e f e r r e d by S t a n t o n to ' A u c e l l a 1  Cairnes Crassi-  collis Keyserling.' T h i s form i s c h a r a c t e r i s t i c o f the l o w e r 1. C a i r n e s , D . U . - C.^.o. Mem.67, p.106, 1914.  -121-  C r e t a c e o u s and has "been found i n many l o c a l i t i e s i n Alaska« The M e s o z o i c  beds o f the Y u k o n - A l a s k a  boundary a r e  1  d e s c r i b e d by C a i r n e s  as c o m p r i s i n g most o f the r o c k  f o r 55 m i l e s s o u t h o f Orange c r e e k . s h a l e s , sandstone,  and  a t l e a s t 4000 f e e t i n t h i c k n e s s .  The  component p e b b l e s i n some beds c o n s i s t  of chert, i n others of s l a t e , quartz i t e , or a n d e s i t i c igneous r o c k s . sed .  slates,  The  v a r y i n t e x t u r e up t o b o u l d e r s , 6 t o 10 i n c h e s i n  conglomerates diameter.  The beds c o n s i s t m a i n l y of  greywaekes, c o n g l o m e r a t e s ,  q u a r t z i t e s and a g g r e g a t e  exposure  c h e r t , and  entirely  granitic  l o c a l l y the r o c k s are metamorpho-  A l t h o u g h the A u c e l l a i n d i c a t e s t h a t p a r t o f the s e r i e s i s  l o w e r C r e t a c e o u s , C a i r n e s s t a t e s : " s i n c e these r o c k s r e s t  on  Upper C a r b o n i f e r o u s o r p o s s i b l y P e r m i a n s e d i m e n t s , and s i n c e f o s s i l s were found  at r e l a t i x ^ e l y few p o i n t s i t seems q u i t e  p o s s i b l e t h a t J u r a s s i c o r even T r i a s s i c - members may  also  be  included." Upper White B.  140°  river.  45' W.,  62° N.  Upper White B i v e r d i s t r i c t .  F o s s i l s c o l l e c t e d from a number o f p o i n t s i n the d i s t r i c t by D.D.  C a i r n e s were r e f e r r e d by T.W.  Stanton to  ' A u c e l l a c r a s s i c o l l i s ' i n d i c a t i n g the l o w e r C r e t a c e o u s age  of  2  the beds from w h i c h t h e y were o b t a i n e d . The  sediments  from w h i c h t h e s e f o s s i l s were o b t a i n e d  are e v i d e n t l y q u i t e s i m i l a r t o the C r e t a c e o u s beds on the 5 boundary n o r t h o f Yukon r i v e r . D.D. C a i r n e s d e s c r i b e s the 1. Idem., pp.105-105." C.G.S. liem.50. p.86, 2. C a irnes,D.D.rn 3. " - Op.cit., pp.83-87.' u  1915.  -122sediments as c o n s i s t i n g o f s h a l e s , a r g i l l i t e s ,  greywackes,  s a n d s t o n e s , and c o n g l o m e r a t e s , h a v i n g an a g g r e g a t e t h i c k n e s s o f 1000  feet.  A l o n g t h e main H u t z o t i n range the conglomerates a r e  c h a r a c t e r i z e d by a r g i l l i t e and c h e r t p e b b l e s .  Along Boulder  creek ( s o u t h e r n p a r t o f the d i s t r i c t ) the conglomerate  contains  l a r g e w e l l - r o u n d e d b o u l d e r s o f g r a n i t i c r o c k s and v a r i o u s canics.  vol-  These M e s o z o i c s e d i m e n t s a r e mapped w i t h some Carbon-  i f e r o u s s e d i m e n t s , and as t h e y appear to conform to t h e l a t t e r , and because s i m i l a r sediments a few m i l e s west i n A l a s k a c o n t a i n b o t h J u r a s s i c and C r e t a c e o u s f o s s i l s , C a i r n e s c o n s i d e r s t h a t the J u r a s s i c and p o s s i b l y the T r i a s s i c i s r e p r e s e n t e d i n the g r o u p . Wind and P e e l  rivers.  The n o r t h w a r d - f l o w i n g Wind r i v e r i s d e s c r i b e d  by  1  C. C a m s e l l  as r u n n i n g from the O g i l v i e range a c r o s s the broad  Peel plateau.  On i t s way a c r o s s the p l a t e a u Wind r i v e r runs  through p a r t o f a low a n t i c l i n a l range c a l l e d the I l l t y d  range  e  The l a t t e r i s composed o f l i m e s t o n e s w h i c h a r e b l o c k - f a u l t e d and domed t h r o u g h C r e t a c e o u s ? sandstone and f i n e  conglomerate  W h i c h o c c u r a l o n g Wind r i v e r above and below the r a n g e .  The  l i m e s t o n e s a r e c o n s i d e r e d by C a m s e l l t o be Devonian; the o v e r l y i n g sandstone appears to be c o n f o r m a b l e ( o r n e a r l y so) t o the l i m e s t o n e s , but i s c l a s s e d as C r e t a c e o u s because o f s i m i l a r i t y to C r e t a c e o u s r o c k s i n o t h e r p a r t s o f the n o r t h w e s t . p a r t o f Wind r i v e r c u t s t h r o u g h T e r t i a r y beds w h i c h  The lower unconform-  a b l y o v e r l i e b l a c k s l a t e s a s s i g n e d to the D e v o n i a n . A l o n g P e e l 1. C a m s e l l , C - " P e e l R i v e r and T r i b u t a r i e s " , C,G.S.An.Rpt.1904, V o l . X V I , Pt.CC, 19 06.  -123r i v e r , below t h e mouth o f Wind r i v e r , T e r t i a r y beds a r e exposed f o r 13 m i l e s and a r e f o l l o w e d by 2 o r 3 m i l e s o f b l a c k s l a t e s and c r y s t a l l i n e l i m e s t o n e s * F o r t McPherson,  A l o n g the r e s t o f P e e l r i v e r t o  C r e t a c e o u s s a n d s t o n e s , c l a y s , s h a l e s and con-  glomerate are exposed.  On the whole the C r e t a c e o u s beds appear  to be p r o g r e s s i v e l y l e s s f o l d e d away f r o m the O g i l v i e r a n g e . F o s s i l s were f o u n d a t two l o c a l i t i e s and d e t e r m i n e d 1 as C r e t a c e o u s by W h i t e a v e s : 133°  C.  40* W.,  65°  55"  N.  N o r t h s i d e o f Snake r i v e r .  Inoceramus sp. Desmoceras c f . D. l i a r d e n s e D.  ;  134°  50* ¥ . , 66°  50*  W.  N.  Undetermined Thracia ? Tellina ?  ammonites.  These g e n e r a o c c u r i n the Upper C r e t a c e o u s C h i g n i k format i o n o f A l a s k a P e n i n s u l a ( M a r t i n , pp.302-303)• Porcupine r i v e r . 2 R.C.  McConnell  on h i s t r a v e r s e from the  Mackenzie  to Yukon r i v e r found c o n s i d e r a b l e e v i d e n c e showing t h a t ceous r o c k s a r e w e l l - d e v e l o p e d a l o n g P o r c u p i n e r i v e r . B e l l and D r i f t w o o d r i v e r he g i v e s the f o l l o w i n g  CretaBetween  section:  In descending o r d e r , 3000 t o 4000 f e e t Q u a r t z i t e s and s a n d s t o n e s . Band of d a r k s h a l e s , p r o b a b l y o f B e n t o n age. Great s e r i e s o f sandstone s h a l e s and c o n g l o m e r a t e s w i t h f o s s i l s . Base not d e t e r m i n e d . Paleozoic limestone• 1. C a m s e l l , C - O p , c i t . , p.487 °~ 2. McConnell,R.G.- C.G.S. No.62?, pp.20?-224, l 8 ? 8 .  -124-  B.  137° 35* W.  f  67° 30' B.  below B e l l r i v e r .  On P o r c u p i n e  river  a few m i l e s  A t t h i s l o c a l i t y M c C o n n e l l found s p e c i -  mens o f ' A u c e l l a mosquensis'. P.  138° 30' W.,  67  0  40» U.  On P o r c u p i n e  r i v e r a few m i l e s  below D r i f t w o o d r i v e r , M c C o n n e l l found specimens o f ' I n o ceramus' i n s h a l e beds w h i c h o v e r l i e and a r e somewhat cordant G.  dis-  to Paleozoic limestones.  135° 25» W.  t  67° 22' IT. P e e l - P o r c u p i n e  portage.  Two l o c a l -  ities. Discina pileolus,  Whiteaves (•?)  I t t h e r e f o r e seems p r o b a b l e  t h a t much o f the p l a t e a u  r e g i o n n o r t h o f the O g i l v i e mountains i s covered  by r o c k s o f  Cretaceous age.  Fig.  16 .  Cretaceous  l o c a l i t i e s of Alaska  CHAPTER V. THE CENOZOIC.  -125GMOZOIC  TERTIARY SYSTEM. The  T e r t i a r y rocks  were l a i d  down i n i s o l a t e d  and  composition.  acid  Tertiary  o f Yukon i n c l u d e  basins,  rocks  localities  1.  Prances r i v e r  W.,  2.  Porcupine  3. K l o n d i k e  (12?°  W. , 6?°  region  (139°  W.,  r e g i o n (140°  5.  K l u a n e Lake  b.  Junction  7.  Upper White R i v e r  district  o f Peel  i n Yukon T e r r i t o r y :  IT.).  (139°  Sixtymile  Prances  60°  river  4.  64°  40' N . ) . 15*  IT.).  25* W. , 63° 40*  (139°  W. , 6 1 °  district  IT.).  (135°  and Wind r i v e r s (140°  IT.).  W. , 65° 4 5 '  55* W. , 6 1 °  50'  IT.).  IT.).  river.  A basin  describes  o f basic  t h o u g h t t o be o f T e r t i a r y age a r e  known a t t h e f o l l o w i n g  junction  and igneous r o c k s  sediments. Sedimentary  1.  sediments which  o f T e r t i a r y s e d i m e n t s was d i s c o v e r e d  o f L i a r d and F r a n c e s r i v e r s the rocks  i n the f o l l o w i n g  by G.M.  Dawson  1  near the  who  words:  " The r o c k s a r e s o f t s h a l e s , s a n d s t o n e s and c l a y s , g e n e r a l l y o f p a l e c o l o r , and h o l d i n g b e d s o f l i g n i t e i n some places. F l o w s o f b a s a l t e i t h e r cap t h e s e r o c k s o r a r e i n c l u d e d i n t h e i r upper p o r t i o n , and from t h e c o n s i d e r a b l e angles of d i p o b s e r v e d , t h e f o r m a t i o n w o u l d a p p e a r t o h a v e s u f f e r e d some f l e x u r e subsequent to i t s d e p o s i t i o n . 1 1  On page 99 o f h i s r e p o r t lignite,  c l a y s , and s h a l e s resemble  Dawson s t a t e s t h a t t h e the Miocene  T. Dawson,G.M.- C.G.S. R p t . b 2 9 , P - 3 4 , 1 « 9 « .  deposits of  "~  '  ~~  "  -12b-  British  Columbia  F i g . 17.  2.  P o s i t i o n s o f T e r t i a r y b a s i n s i n Yukon.  Porcupine r i v e r . S e d i m e n t a r y r o c k s a s s i g n e d t o t h e T e r t i a r y were  found by R.G. McConnell'*' a l o n g P o r c u p i n e r i v e r between D r i f t wood r i v e r and t h e P o r c u p i n e r a m p a r t s . these  From t h e d e s c r i p t i o n s  c o n s i s t o f s o f t , s c a r c e l y s t r a t i f i e d , w h i t i s h and y e l l o w  i s h c l a y s and s a n d s , which unconformably o v e r l i e C r e t a c e o u s shales.  I n t e r b e d d e d p e b b l e conglomerate was a l s o f o u n d i n t h e  1. McConnell,R.G.- C.G.S.Rpt.b2? , pp.220-224 and p.240, lb"9«.  -127-  f o r m a t i o n , and a t one  s e c t i o n a s m a l l l i g n i t e seam was  noted.  These beds a r e h o r i z o n t a l , o r n e a r l y s o , and have a minimum t h i c k n e s s o f 300  feet,  McConnell  c o n s i d e r e d them c o r r e l a t i v e  w i t h t h e I a r a m i d e beds o f t h e M a c k e n z i e , f o s s i l s i n the 3.  a l t h o u g h he found  no  strata.  Klondike region. The  T e r t i a r y sediments  o f K l o n d i k e r e g i o n have been 1  d e s c r i b e d by R.G. The  McConnell  under the name "Kenai s e r i e s  l a r g e s t a r e a o f t h e s e r o c k s extends  west f o r 70 m i l e s from K l o n d i k e r i v e r .  ?*.  west-north-  I t l i e s a l o n g the base  of the O g i l v i e range and has a p r o b a b l e w i d t h o f 10 m i l e s . O t h e r s m a l l e r b a s i n s o c c u r on the out s k i r t s o f the K l o n d i k e district. These r o c k s c o n s i s t of s l i g h t l y coherent w i t h conglomerates  sandstones  a l t e r n a t i n g w i t h c l a y s and s h a l e s and,  sionally , lignites.  The  sandstones  are o f t e n a r k o s i c .  occa-  The  beds u s u a l l y show moderate d i p s , but f a u l t s and h i g h d i p s occur.  The  t h i c k n e s s i s unknown.  The  age  of the l i g n i t e - b e a r i n g beds o f t h e main a r e a 2  The was d e t e r m i n e d from f o s s i l l e a v e s t o be Upper Eocene. s e d i m e n t s , the r e f o r e , a r e a p p r o x i m a t e l y c o r r e l a t i v e w i t h the 3  Kenai s e r i e s of Kenai P e n i n s u l a . A n o t h e r a r e a of T e r t i a r y r o c k s o c c u r s i n t h e v a l l e y o f l a s t Chance c r e e k .  As w e l l as the sediments  mentioned above,  t h i s g r o u p c o n t a i n s beds o f decomposed a n d e s i t i c t u f f . 1. M c C o n n e l l , E . G . - C.G.S.Rpt.8«4 , pp,23-24, i ? u > . " 2. C o l l i e r , A . J . - U.S.G.S.Bull.218, p.25, 1903. 3. M a r t i n , G . C . - U.S.G.S.Bull.587 . p. 8.8, 1915.  "~~  -128Another Creek  beds'  extend ly  group  of Tertiary  by M c C o n n e l l ,  from  a point  occur  n o r t h of Twelvemile  and  are h o r i z o n t a l  silt. late  be  They r e s t  Tertiary,  river  to Stewart  on the K e n i a may  the  series  sand,  ( ? ) and  represent g l a c i a l  'Flat These  i n a southeaster-  river.  beds o f l o o s e g r a v e l ,  but  called  i n the K l o n d i k e r e g i o n *  d i r e c t i o n a c r o s s the K l o n d i k e  strata  sediments,  These sandy  clay,  are thought  outwash from  to  the  1 Ogilvie  4.  range.  Sixtymile  region.  Sediments p r o v i s i o n a l l y occur  on Mat s o n  a s s i g n e d to the K e n a i  creek, a tributary  of Sixtymile  river;  series a  few 2  small  areas also The  s t o n e , and the  occur along ladue  occurrence  conglomeratej  1 i g n i t e was  not  creek bed.  The  o v e r l a i n by  friable  or  on M a t s o n c r e e k and  found  lower part  glomerate , which  river  possibly  i n the  same r e g i o n .  shows s h a l e ,  some l i g n i t e ,  i n p l a c e , but  sand-  although  i n pebbles i n the  o f t h e f o r m a t i o n i s compact s h a l e ,  a r k o s i o sandstone  w h i c h g r a d e s up  i s composed o f p e b b l e s o f q u a r t z ,  to  con-  quartzite,  schist. These  b a s a l t s , and  allied  The show low  rocks are invaded  dips,  r o c k s of the  Tertiary but  sediments  o r o v e r l a i n by the a n d e s i t e s , 'Hewer v o l c a n i c s ' . of Sixtymile  i n some c a s e s a r e  region usually  considerably disturbed  and  faulted. These beds are p r o b a b l y e q u i v a l e n t to s i m i l a r ments i n t h e n e i g h b o r i n g F o r t y m i l e d i s t r i c t 1. 2.  McConnell,R.G-.- R p t . c i t e d , p.25* C o c k f i e l d , W , E . - C.G.S. Mem.123, p p . 2 9 - 3 1 .  sedi-  o f A l a s k a where ~~~  -129fossils  5.  show the age  Kluane lake  t o he  ahout  Kenai.  1  district.  Two  small basins  of T e r t i a r y  eastern front  of St. E l i a s  range near Kluane  o n Sheep  sediments occur i n the lake.  and K i m b e r l e y c r e e k s , a n d h a v e b e e n  These  occur  d e s c r i b e d by  R.G.  2 McConnell. grits,  The  s e d i m e n t s a r e composed o f t u f f s ,  c o n g l o m e r a t e s , and  seams.  The  sediments strongly  beds  are s a i d  Junction of Peel A  and  basin  beds  of  are exposed  d e s c r i b e d as  McConnell  range.  and W i n d  of T e r t i a r y  the l o w e r p a r t  These  to be v e r y s i m i l a r t o t h e  and h a v e p a r t i c i p a t e d  making movements o f t h e 6.  shales containing occasional  o f the K l o n d i k e . folded  sandstones,  Eooene "They  i n the p r i n c i p a l  are  mountain-  1 1  rivers. sediments exposed  Wind r i v e r f o r 13  states also:  lignite  on P e e l  i s d e s c r i b e d by  m i l e s on P e e l  river  river  G. C a m s e l l . ^ and  are  follows:  11  «. The r o c k s o f t h i s b a s i n c o n s i s t o f t h i c k b e d s o f s o f t s a n d s t o n e , w i t h some t h i n seams o f l i g n i t e , o v e r l a i d b y more s a n d s t o n e c o n t a i n i n g p e b b l e s , w i t h c l a y a n d some v e r y t h i c k beds o f l i g n i t e . The whole s e r i e s h a s b e e n g e n t l y f o l d e d i n t o a number o f a n t i c l i n e s a n d s y n c l i n e s . "  7.  U p p e r White The  three beds  small  River  Tertiary  district. sediments of t h i s  a r e a s n e a r to t h e A l a s k a - Y u k o n  comprise mainly l o o s e l y  s h a l e s , and  district  clays.  Some t h i n  a b l e amount o f f o s s i l  or partly  occur i n  boundary.  consolidated  seams o f l i g n i t e  wood o c c u r i n t h e b e d s .  These sandstones,  and a  consider-  These  strata  1. P r i n d l e . L . M . - U . S . S . B u l l . 3 ? 5 , pp.2>-2b, I 9 0 7 . 2. M c C o n n e l l , R . G . - C.G.S .Sum.Rpt .1904 , p.7 , 190.5. 3. C a m s e l l , C - G.G.S.An.Rpt.1904, V o l . X V I , p t . C C , p . 4 1 ,  are  ~ 1906.  -130gene r a l l y and is  flat-lying  o v e r l a i n by b o t h considered  Tertiary  b a s i c and a c i d  t o be K e n a i  and Quaternary Tertiary  intrusive and  and u n d i s t u r b e d ,  bodies  throughout  lavas with  o f t h e same p r o v i n c e s  rocks  of this  type  range and A r c t i c  provinces  These l a v a f l o w s b a s i c and a c i d  types.  g e n e r a l l y been c a l l e d  r e g i o n o f Yukon charac-  Prom what l i t t l e i s  mountains,  are o f very  the Rocky M o u n t a i n p r o v i n c e .  a s s o c i a t e d minor  They a r e e q u a l l y  i n Alaska.  known o f t h e M a c k e n z i e a n d O g i l v i e that  1  the i n t e r i o r  i n the C o a s t a l System mountains.  teristic  both  i n age.  The f o r m a t i o n  Rooks.  and Q u a t e r n a r y  occur  volcanics.  o r Eocene  Igneous  b u t have b e e n i n t r u d e d  restricted  i ti s probable occurrence i n  The same i s t r u e o f t h e B r o o k s  o f Alaska. and a s s o c i a t e d i n t r u s i v e s  embody  I n Y u k o n t h e more b a s i c t y p e s  have  t h e 'Newer v o l c a n i c s " .  Newer v o l c a n i c s . T h i s name was a p p l i e d b y C a i r n e s sites,  d i a b a s e s , b a s a l t s , and a l l i e d  rocks  to a group o f andeo f T e r t i a r y age,  2 . which occur  i n Upper White R i v e r d i s t r i c t .  included with Nordenskiold  a n d Wheaton r i v e r s , a n d o t h e r p o r t i o n s o f Yukon.  name h a s b e e n u s e d  can  be r e g a r d e d  1. 2. 3.  he  t h e Newer v o l c a n i c s t h e 'Carmack b a s a l t s ' o f  The  andesitic  Subsequently  i n other  r e p o r t s on i n t e r i o r  Yukon, and  a s a g e n e r a l term t o i n c l u d e b a s a l t i c and  l a v a s o f Cretaoeous  to Recent age.  C a i r n e s , D . D . - C.G.S. Mem.50, p p . 9 5 " 9 7 , 1 9 1 5 . C a i r n e s , D . D . - C.G.S. Mem.50, p p . 9 7 - 1 0 1 , 1 9 1 5 . " " - C.G.S. Sum.Rpt.1915, p . 4 2 , 191b.  -131Rocks o f t h i s  type  Y u k o n P l a t e a u r e g i o n and distribution, probably  the  occur  i n the  i n every  Coast  range.  lavas l i e i n separated  approximate with  the  large area of Although  'basins  1  map  o f wide  which  centres of o r i g i n .  b u t i o n i s shown o n t h e g e o l o g i c a l  the  The  distri-  ( i n pocket).  These l a v a s are undoubtedly  of s e v e r a l ages.  In  1 Sixtymile  district  t r u n c a t e d by  .they  cut the  the u p l a n d  activity,  occur  i n the  Yukon p l a t e a u i s thought end  o f Miocene time,  early  in  the  age,  vening and  rivers,  field  mouth o f N o r d e n s k i o l d lava  as  f l o w s from  they  original  probably  have not  upper  The  lava  somewhat  of lewes r i v e r ,  and  river.  a v o l c a n i c cone been weathered  surface details  at  older.  inter-  In the  the  the  between N o r d e n s k i o l d  show t h a t i n t e r m e d i a t e s t a g e s  C a r m a c k s b a s a l t s and  formed  flows a c t u a l l y  Recent  from exist  e f f u s i o n s near  river. A t M i l e s canyon on lewes r i v e r , Hoole  r i v e r , and 1.  district  v a r i o u s groups of flows occur, which  relationships  between the Pelly  are  c o u n t r y west  Pelly  their  show t h e  Pelly  the  t o t h e Y u k o n p l a t e a u i s shown  of s o l i d i f i c a t i o n .  mouth o f t h e  As  age.  are  time  o f the Fewer v o l c a n -  to r e p r e s e n t a p e n e p l a i n formed by  river  at the  and  the  N e a r t h e mouth o f P e l l y o b v i o u s l y of Recent  are  surface of  Carmacks b a s a l t s at the  but  stages  Eooene b e d s .  Similar relationship  appreciably,  but  t h e Newer v o l c a n i c s o f S i x t y m i l e  are Eocene t o Miocene  by t h e  sediments,  s u r f a c e o f the Yukon p l a t e a u ;  t u f f s , b e l i e v e d to r e p r e s e n t ics'  Eocene  the  ramparts  Cockfield,W.E.-  of Porcupine  river,  O.G'.S. Mem.123, p.32,  c a n y o n on  basaltic  1?21.  Pelly  flows —  —  occur  i n v a l l e y s w h i c h had.been-out i n t o  plateau. depth  The p r e s e n t  r i v e r s have i n c i s e d t h e s e  o f t h e o r d e r o f 100  as o f l a t e  Tertiary  the u p l i f t e d  feet*  These f l o w s  or Quaternary  In the Wrangell  Yukon  flows to a  c a n be  regarded  age.  mountains o f the P a c i f i c  system  of  • 1 Alaska, Mendenhall activity ranging  has d e s c r i b e d l a v a s which represent  from Eocene t o Recent from  early  Tertiary  time.  igneous  B a s a l t s and r h y o l i t e s  to Recent  time  are recognized  near  2 the head o f Tanana r i v e r i n the i n t e r i o r Upper C r e t a c e o u s  t o Recent  Koyukuk b a s i n , s o u t h elsewhere Acid  l a v a s and p y r o e l a s t i c s o c c u r i n the  of Brooks  range•^  S i m i l a r r o c k s a r e known  i n Alaska. types. These r o c k s  consist  o f r h y o l i t e s and a s s o c i a t e d  t u f f s and b r e c c i a s , w i t h g r a n i t i c as h y p a b y s s a l flows occur probably  region of Alaska.  phases,  like  porphyry  and q u a r t z porphyry ,  t h e Newer v o l c a h i c s , t h e r h y o l i t e  a t a number o f w i d e l y s e p a r a t e d l o c a l i t i e s .  represent  common a r e r h y o l i t e  t h e same i n t e r m i t t e n t dykes,  and r h y o l i t e  vuloanicity.  They More  and g r a n i t e porphyry-  stocks. The  most a b u n d a n t  quartz porphyries.  r o c k s o f the a c i d type  are the  These r o c k s a r e mentioned i n n e a r l y every  area  examined i n t h a t p a r t o f Yukon s o u t h o f t h e O g i l v i e  west  o f the M a c k e n z i e m o u n t a i n s .  readily  distinguished  and  The q u a r t z p o r p h y r i e s a r e  i n the f i e l d .  They have a y e l l o w ,  1. M e n d e n h a l l , W . C . - U . S . G . S . P r o f . P a p . 4 1 ,  p p . 5 4 - 6 2 , 1905*  2. M e r t i e , J . B . , j r . - U . S . G . S . B u l l . 8 2 7 , PP*39"40, 1931* 3. Smith,P.S. & M e r t i e , J . B . J r . - U . S . G . S . B u l l . 8 1 5 , p . 2 6 5 ,  1930.  - I n compact, a p h a n i t i c groundmass, w h i c h pegmatitie.  The p h e n o e r y s t s  i s m i c r o g r a n i t i c or micro-  are quartz, feldspar,  These r o c k s o c c u r  a s d y k e s w h i c h have been f o u n d  c o n s o l i d a t e d rock  formations with  most r e c e n t they  basaltic  are covered  sidered  Gairnes  spring  Tertiary  seems p r o b a b l e ,  . '1'  by  by g l a c i a l  t o be l a t e It  lavas.  or b i o t i t e .  t o cut a l l the  t h e e x c e p t i o n o f some o f t h e  I n t h e g l a c i a t e d r e g i o n , however, d e p o s i t s , so t h a t t h e i r  age i s c o n -  o r early Pleistocene. from  t h e r e l a t i o n s h i p s w o r k e d out  '  i n Wheaton d i s t r i c t ,  a c t i o n i n connection with  and from  evidence  of hot-  the quartz porphyries o f  2 Sixtymile ciates Newer  district  , t h a t the a c i d v o l c a n i c s and t h e i r  asso-  a r e o n t h e whole , y o u n g e r t h a n t h e m a j o r i t y o f the volcanics.  QUATERNARY SYSTEM. The  P l e i s t o c e n e and Recent  Yukon and A l a s k a volcanic  pocket)•  of unconsolidated  sediments,  a s h , b u r i e d and s u r f a c e i c e , and v o l c a n i c f l o w The  glacial  by a wide range  epochs are r e p r e s e n t e d i n  drift,  distribution of glacial till,  Pleistocene  i c e sheets.  to indicate  B u t much o f t h i s  r e d e p o s i t e d both  during  the area covered  4( i n by the  Among t h e u n c o n s o 1 i d a t e d d e p o s i t s i n  the g l a c i a t e d r e g i o n s , p r o d u c t s predominate.  deposits, including  and m o r a i n e s , i s shown i n f i g u r e  These a r e taken  rocks.  of g l a c i a l  erosion  probably  m a t e r i a l has been reworked and  the i c e r e t r e a t  and i n Recent  1.  C a i r n e s , D . D . - C.G.S. Mem.31, pp.68-72,  1912.  2.  Cockfield,W.E.-  1921.  G.G.S. Mem.123, p.34,  time,  and  probably  includes pre-Pleistocene  In the  unglaciated region  ments i n c l u d e p r o d u c t s gravity and  and  Recent  deposits and  running times,  water  unconsolidated  sedi-  late  Tertiary, Pleistocene,  extraglacial  streams f r o m the  by  or g l a c i a l  outwash  g l a c i a t e d regions  during  ice retreat. The  oldest  gravels  g l a c i a t e d r e g i o n , are  the  of the Klondike  white  1  McConnell" * t o d a t e back t o t h e and  the  well.  decomposition coneentrated  during  as w e l l as  c a r r i e d by  after  of r o c k  g r a v e l s as  boulders  i n this  deposit  channel g r a v e l s McConnell  district,  channel g r a v e l s Pliocene  are  largely  said  at l e a s t . quartz.  in  by  The Of  the  pebbles  the  white  states:  " T h e y w e r e a l m o s t c e r t a i n l y d e p o s i t e d when m i l d e r c l i m a t i c c o n d i t i o n s p r e v a i l e d , a s t h e l e a c h i n g o u t o f the g r e a t e r p a r t o f t h e i r o n , and t h e d e c a y e d c o n d i t i o n o f t h e s c h i s t p e b b l e s must be a t t r i b u t e d t o s u r f a c e w a t e r s , and no c i r c u l a t i o n o f t h e s e was p o s s i b l e i f t h e g r a v e l s , l i k e t h o s e o f the p r e s e n t s t r e a m s , h a d b e e n f r o z e n t o g e t h e r a s s o o n a s deposited." Somewhat along  the  north  f r o n t of the  much o x i d i z e d a n d age. like  s i m i l a r are  were  Alaska  deeply  the  range.  They are  r a n g e , and  synonymously w i t h  are  the  streams before  progressively less  o f the  are  the  ice-  and  post-Eocene u p l i f t  b e l i e v e d i n part to  uplift  These g r a v e l s  Eocene c o a l measures  l a t t e r have p a r t i c i p a t e d i n the  the A l a s k a from the  range.  e r o d e d by  They c o n f o r m a b l y o v e r l i e the  the Henana g r a v e l s , which l i e  d e f o r m e d away  have b e e n  range, or  of  deposited  directly  after  a the  coal-bearing It  beds.  i s therefore  probable  t h a t the  unconsolidated,  1. M c C o n n e l l , R . G . - C.G.S. R p t . 8 8 4 , p p . 3 1 - 3 3 , 1905. 2. C a p p s . S . R . - U.S.G.S. B u l l . 8 3 6 , pp.279-284, 1933.  "  or  •.-135partially  c o n s o l i d a t e d sediments o f the  Y u k o n and  Alaska,  although  the  Pleistocene  great and  The in  range  majority  soil,  a  such  the  result  o f the  time,  conceded to  he  the  of the  thrive.  i s forming  The  muck  tundra  the  run-off  accumulate.  t e m p e r a t u r e was  plants  Such m a t e r i a l  muck.  s o i l - e r o s i o n by to  high  embody d e p o s i t s  i n the unglaciated region  than i t i s a t present,  These during  probably  lower  t y p e were a b l e  at present,  the  especially  to  on  slopes.  Surface  ice i n Alaska  confined  small g l a c i e r s  They  to  the  are  are  the  and  Coastal  a r e known i n the  glaciers  sheets.  of  frozen condition of  prevented  P l e i s t o c e n e , when, a l t h o u g h  present  also  decayed v e g e t a t i o n  d e p o s i t s were a c c u m u l a t i n g  exclusively  are  m a t e r i a l , l o c a l l y known a s  direct  allowed  north-faoing  deposits  deposits  c o n d i t i o n which has  w a t e r and  from Eocene to Recent  of  unconsolidated  are  regions  Recent.  decayed organic  deposits  i n age  interior  present  System mountains.  almost A  B r o o k s Range p r o v i n c e .  vestiges  confined  Yukon i s at  of the  to r e g i o n s  former great  of high  relief  few The  ice and  heavy  precipitation. A widely i n the south  upper basins of  latitude  deposits to  Capps  valley  1.  d i s t r i b u t e d deposit  and 1  o f Yukon and  63.  This  this  material  of White r i v e r  Tanana r i v e r s ,  overlies  i s g e n e r a l l y two  of v o l c a n i c ash  the  or three  inches  o r i g i n a t e d i n an  some 1400  years  other  i n general unconsolidated  thick.  eruption  According  i n the  ago.  Gapps.S.R.- TT.S.G.S. P r o f . P a p . 9 5 , '-pp.59-64,  occurs  1915.  upper  -136-  As a l r e a d y m e n t i o n e d , some v o l c a n i c f l o w s a r e known i n Y u k o n and A l a s k a w h i c h a r e b e l i e v e d t o be of P l e i s t o c e n e ai Recent age.  V o l c a n i c a c t i v i t y i s s t i l l p r e v a l e n t i n the  A l e u t i a n chain of Alaska*  CHAPTER V I .  T H E  C H R O N O L O G I C A L  R E C O R D .  -137-  CHRONOLOGIC  This  chapter  gical history  embodies a b r i e f  summary o f t h e g e o l o -  o f Yukon w i t h r e f e r e n c e t o A l a s k a ,  c o r r e l a t i o n o f the horizons  Eedueed  and a g e n e r a l  i n t h e two r e g i o n s .  PRSCAMBRIAN  RECORD.  t o i t s s i m p l e s t form, a g e n e r a l  of the Precambrian next  RECORD.  rooks  correlation  o f Y u k o n and A l a s k a i s shown o n t h e  page. The  sediments  oldest  o f the Hasina  the P r e c a m b r i a n character traces that  r o c k s known i n Y u k o n a r e t h e metamorphosed  Birch  s e r i e s , which  Creek s c h i s t  i s correlated  of Alaska.  o f t h e b a s a l members o f t h e s e  of original  texture which they  they are deposits o f the l i t t o r a l  have b e e n f o u n d  i n the Hasina  series,  here  The a r e n a c e o u s  sediments,  and t h e  show i n p l a c e s , type•  A s no  i t cannot  r e p r e s e n t s marine  with  indicate  fossils  d e f i n i t e l y be  stated  that the s e r i e s  larity  o f l i t h o l o g y o v e r w i d e a r e a s , h o w e v e r , and t h e d e v e l o p -  ment o f a r g i l l a c e o u s  b e d s and l i m e s t o n e s  the  uniform  sequence  suggest  great area which fore,  that  these  the Hasina  sedimentation.  i n the upper p a r t o f  c o n d i t i o n s o f d e p o s i t i o n over the  rocks occupy. and B i r c h  I t i s conceivable,  Creek s t r a t a  represent  t i o n i n a s e a w h i c h o c c u p i e d what i s now t h e i n t e r i o r r e g i o n o f Y u k o n and A l a s k a , extent, p o s s i b l y  completely,  and w h i c h o v e r l a p p e d  the b e l i e f  there-  deposiplateau  t o some  t h e C o a s t a l System mountains.  Reasons have been advanced support  Simi-  i n f o r e g o i n g pages t o  t h a t t h e T a t a l i n a g r o u p and e q u i v a l e n t  -138-  1  OH ©  © as rt  ©O 05 0}  rO  rt ri © .©  bo 8 © •rtr  a  o  a  •i' «  o5 ts  n  A  o  i>:  ri 05  rH  O © ,£3 +> 03 Gj , Q H O  o  U  A  rt  >0  54  <a  Art  •H © O A{H •rt A M O T3 O ,4 +5 O rt *H  «o  ©  65  o  o  05  g  M  © 03 4 3 13  o  O 8 ^  M  ©  •H  g ©  rt  +3  o  o  a 43 rt o  •rt 50 ©  as  I  +3 •rt  g ©  O O  bQ <D j* rt N +3  O  o  • 43  ©  rtxj  43  43  o  03 03 rH 03 03 © © •rt +3 05 43 rt © -rt O rt H © O feO © ^ ri fe-H rO ©  Hi! rt ©  rH  02 © •rt © 03  §  ©  •rt  bt  &  03  09  rt+a rt  o as o  03 ©  o  0 S rQ •rt «rt rO rt  ©  43  o3 *—> © © © 03  +5H-P  ta  03 © •rt  ©  05 ©  rt  ©  >»> u ta H © O «5  ftgrl  I  rttn  rt  © 43 r© rt o H  ta  i rt Q  O  ©  rt  O © 03  43 43  r-i  43  O «H  +3  rt  05. ©  r© 43 *rt O rt © Cfl K5 u ©  .rt-H43  rt Oa  43 •rt  A H  o  rt 43 u c3O rt  m  ri  ri -rt om  01  03 •H Og  rgS o  0  rO 43  A  S3 »©  {=•»  ©  43  ©  ©  rt  E«0  O  o  o ©  CO  © 03  ©  a © +3 •rt  M  ©  03 43  § ©  a © 43 •rt  43  O Pi  43  cd  >5> 43  43 43  rQ © • 43 4»  © O  rt  © iH  O O rt S3  •rt  03  05  43  rt  03  05  03 M  X!  03 03 03  03 ©  . ro •rt  o5  o ^  MU  03 03  o  05 M- r H  03 U ri «rt  © pq © rt ©  H 43  •a  05  rM  03 •0©43 r5t « rt O O  o ©  o ro *4 o  rt © o ra ri o ©  ©  «q  m  M ©  O  © bO  si u § o ©u U  43  •n rt  PQ M  © ©  A A  ©  rO •rt  Eg O rt  o  ©  -139-  sediments  i n n o r t h e r n A l a s k a are c o r r e l a t i v e w i t h the  g r o u p and e q u i v a l e n t sediments mountains.  These sediments  Tindir  o f t h e O g i l v i e and M a c k e n z i e  are r e s t r i c t e d t o t h e n o r t h e r n and  n o r t h e a s t e r n b o r d e r s o f the a r e a o c c u p i e d by the B i r c h Creek s c h i s t and H a s i n a s e r i e s .  They a l s o e x h i b i t the  following  features: (1)  T e x t u r e and c o m p o s i t i o n which  indicate, i n part, deposition  close to source. (2) R a p i d changes i n l i t h o l o g y and i n t e r b e d d e d v o l c a n i c members , i n d i e a t i n g d e p o s i t i o n during a p e r i o d of (3)  instability*  F e l d s p a t h i c members i n d i c a t i n g d e r i v a t i o n , i n p a r t , from  igneous r o c k s . These c o n s i d e r a t i o n s s u p p o r t the t h e o r y t h a t t h e T i n d i r and T a t a l i n a groups were depo s i t e d i n a g e o s y n c l i n a l a r e a which o c c u p i e d what i s now  the n o r t h e r n p a r t o f i n t e r i o r  A l a s k a , the O g i l v i e mountains , and the M a c k e n z i e m o u n t a i n s . They f u r t h e r suggest t h a t t h i s s e d i m e n t a t i o n was  accompanied  by, o r f o l l o w e d , u p l i f t o f the g e n e r a l r e g i o n o c c u p i e d by the B i r c h Creek and H a s i n a s t r a t a .  I t seems l o g i c a l t o assume  t h a t the g r a n i t e g n e i s s and igneous s c h i s t a s s o c i a t e d w i t h the metamorphosed P r e c a m b r i a n interval  9  sediments were i n t r u d e d d u r i n g t h i s  which p r o b a b l y r e p r e s e n t e d t h e c l o s e o f  Precambrian  time* The u p l i f t w h i c h r e s u l t e d i n t h e e l e v a t i o n o f the B i r c h C r e e k and H a s i n a sediments  and, r e s t r i c t i o n o f the T a t a - .  l i n a and T i n d i r d e p o s i t i o n to the n o r t h e r n and e a s t e r n a r e a s appears t o have been of a r e g i o n a l c h a r a c t e r , and p r o b a b l y i n c l u d e d A l a s k a s o u t h o f the Yukon r i v e r and Yukon west o f t h e  •140*  Mackenzie  mountains.  T h i s landmass was p r o b a b l y c o n t i n u o u s t o  the s o u t h w i t h the a n c i e n t l a n d o f C a s c a d i a .  PALEOZOIC RECORD, The known Cambrian o f A l a s k a - Y u k o n  c o n s i s t s o f Upper  and M i d d l e Cambrian l i m e s t o n e a t t h e 1 4 1 s t . m e r i d i a n , n o r t h o f Yukon r i v e r , and Upper o r M i d d l e Cambrian l i m e s t o n e i n t h e Mackenzie  mountains, a t Gravel r i v e r .  that very l i t t l e  I n view o f t h e f a c t s  i s known o f the i n t e r v e n i n g c o u n t r y , and t h a t  t h e Cambrian f a u n a s o f t h e N o r t h American  C o r d i l l e r a are large-  1  l y of A r c t i c o r i g i n ,  i t i s p r o b a b l e t h a t a Cambrian seaway  e x t e n d e d f r o m t h e A r c t i c ocean r e g i o n s o u t h t o t h e O g i l v i e and M a c k e n z i e mountains and t h r o u g h t h e Rocky Mountain B r i t i s h Columbia.  system  into  The Cambrian s e a s , t h e r e f o r e , f o l l o w e d t h e  g e o s y n c l i n e i n i t i a t e d d u r i n g t h e T i n d i r epoch.  There  appears  t o be no marked u n c o n f o r m i t y between t h e Cambrian and T i n d i r beds, but a marked change i n s e d i m e n t a t i o n , p r o b a b l y from a s h o r e - l i n e t o a t y p i c a l l y marine  t y p e , i s r e c o r d e d i n the  l i t h o l o g y o f t h e T i n d i r and Cambrian beds. D u r i n g t h e O r d o v i c i a n t h e seas were more t r a n s g r e s s i v e and appear t o have i n v a d e d p a r t o f t h e C a s c a d i a n l a n d mass and c o v e r e d a l l o f A l a s k a and Yukon.  Ordovician limestones are  known i n e v e r y l a r g e a r e a o f A l a s k a , and a l t h o u g h t h e y a r e n o t known i n s o u t h e r n Yukon ( e x c e p t from f o s s i l s o f an unknown h o r i z o n i n t h e c o u n t r y west o f t h e Coast r a n g e , see p. 9 7 ) . O r d o v i c i a n r o c k s have been found i n s o u t h e a s t e r n A l a s k a and on 1. Resser,C.E.-  Bull.Geol.Soc.Am.,  V o l . 4 4 , p»74H, 1933"  -141-  o  CO 4 3 13 ! 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S i m i l a r c o n d i t i o n s p r e v a i l e d d u r i n g the S i l u r i a n , f o r limestone  of t h i s age  l y a l l the O r d o v i c i a n  i s known i n the g e n e r a l v i c i n i t y o f n e a r localities.  I t i s probable  t h a t the O r d o v i c i a n , S i l u r i a n ,  and  D e v o n i a n s e d i m e n t s were d e r i v e d from the C a s c a d i a n landmass, which occupied area.  The  a p o s i t i o n somewhere i n the N o r t h P a c i f i c Ocean  combined t h i c k n e s s o f t h e s e s e d i m e n t s i s p r o g r e s s -  i v e l y g r e a t e r f r o m Seward p e n i n s u l a t h r o u g h the upper Yukon r e g i o n to s o u t h e a s t e r n A l a s k a .  Of the o r i g i n o f the  Ordovician 1 . to D e v o n i a n s e d i m e n t s i n s o u t h e a s t e r n A l a s k a , R e s s e r states: " I t i s e v i d e n t t h a t the v a s t q u a n t i t y o f e l a s t i c s and v o l c a n i c m a t e r i a l c o u l d not have come from the e a s t w a r d , mhere no s i g n s o f such m a t e r i a l s are f o u n d i n sediments o f a p p r o x i m a t e l y e q u i v a l e n t age. One i n e v i t a b l y i s f o r c e d to the c o n c l u s i o n t h a t d u r i n g the g r e a t e r p a r t o f the P a l e o z o i c t h e r e e x i s t e d a c o n s i d e r a b l e landmass o f h i g h r e l i e f and o r o g e n i c a c t i v i t y t o the westward i n what i s now the n o r t h e r n P a c i f i c Ocean. 11  l o w e r Devonian r o c k s have n o t been recognized, i n Yukon o r A l a s k a , and a g r e a t s t r u c t u r a l u n c o n f o r m i t y  is  b e l i e v e d to e x i s t between the S i l u r i a n and Devonian r o c k s n o r t h e r n and  i n t e r i o r Alaska.  the l o w e r Devonian was Alaska.  I t i s t h e r e f o r e probable  of  that  a p e r i o d o f emergence i n Yukon and  T h i s u p l i f t was  probably  accompanied by some mountain  b u i l d i n g , p a r t i c u l a r l y i n n o r t h e r n A l a s k a , where a g r a n i t e g n e i s s o f l a t e S i l u r i a n o r e a r l y Devonian age has been f o u n d . Also i t i s probable  t h a t p y r o x e n i t e and p e r i d o t i t e o f  southern  Yukon, b a s i c dykes and s i l l s o f the A l a s k a - Y u k o n boundary, and the r h y o l i t e s o f the T o t a t l a n i k a s c h i s t o f the A l a s k a range 1. Resser,O.E.- B u l l . G e o l . S o c . A m . , V o l . 4 0 , p . 2 2 9 ,  1929.  -146-  were e r u p t e d d u r i n g t h i s  emergence.  C e r t a i n o f the s t r u c t u r e s , p a r t i c u l a r l y the w e l l d e v e l o p e d c l e a v a g e , o f the B i r c h Greek s c h i s t and Yukon group may date t o the S i l u r i a n - D e v o n i a n i n t e r v a l , f o r a s i m i l a r c l e a v a g e o c c u r s i n t h e Lower P a l e o z o i c r o c k s , hut i s n o t c h a r a c t e r i s t i c o f t h e Upper P a l e o z o i c s e d i m e n t s .  Cleavage and  f o l d s i n the Lower P a l e o z o i c and P r e c a m b r i a n r o c k s o c c u r i n two d i r e c t i o n s , one p a r a l l e l t o t h e t r e n d o f t h e n o r t h w e s t e r n d i l l e r a , the o t h e r more o r l e s s a t r i g h t a n g l e s .  Cor-  The l a t t e r  s t r u c t u r e s a r e t h e more obscure and a r e b e l i e v e d t o be t h e o l d e r , but t h e s t r u c t u r e s p a r a l l e l t o t h e C o r d i l l e r a may be i n p a r t P a l e o z o i c , f o r t h e y a r e e q u a l l y w e l l - d e v e l o p e d away from the M e s o z o i c i n t r u s i v e s as they a r e a t t h e i n t r u s i v e c o n t a c t s . The M i d d l e Devonian was a t i m e o f s u b s i d e n c e w i t h d e p o s i t i o n o f l i m e s t o n e a l l o v e r A l a s k a and i n t h e O g i l v i e and Mackenzie  mountains o f Yukon.  I t i s probable t o o , that  i n t e r i o r and w e s t e r n Yukon was i n v a d e d by the s e a , f o r f o s s i l s o f p r o b a b l e Devonian age have been found i n southern. Yukon. Upper Devonian d e r s o f the A l a s k a - Y u k o n  sediments a r e r e s t r i c t e d t o t h e b o r region.  They o c c u r i n n o r t h e r n  A l a s k a , s o u t h e a s t e r n A l a s k a , p r o b a b l y i n the Mackenzie t a i n s , and i n t h e Mackenzie  r i v e r region.  moun-  I t i s probable,  t h e r e f o r e , t h a t a g e n e r a l s h o a l i n g o f t h e sea o c c u r r e d i n l a t e Devonian  t i m e , and t h i s was accompanied i n i n t e r i o r Yukon and  A l a s k a by v o l c a n i c a c t i v i t y w h i c h c o n t i n u e d i n t o t h e e a r l y Carboniferous•  TSo major u n c o n f o r m i t y i s i n d i c a t e d , but t h e r e  was a break i n s e d i m e n t a t i o n d u r i n g t h e i n t e r v a l between t h e Devonian and C a r b o n i f e r o u s •  -147The Alaska.  Garboniferous  Marine  covered, a l l o f Y u k o n a n d  sedimentation reached  an a n d P e r m i a n t i m e , Pennsylvanian  seas  a maximum  hut s h o a l i n g appears  t i m e when t r a n s i t i o n  Following Carboniferous  the widespread  and Lower and M i d d l e  e r o s i o n ensued u n t i l  crest ains  f l o w s were e x t r u d e d  o f Yukon.  invade  indicates  that  that  occupied  The a b s e n c e o f known sediments  late  indicates  During  this  i n the r e g i o n south  that  interval  o f the  and p r o b a b l y i n t h e N u t z o t i n mountc h a r a c t e r o f the T r i a s s i c  the Upper T r i a s s i c  a r e g i o n o f mountain ranges,  Permian or l a t e  the whole a r e a  Triassic  The f i n e - g r a i n e d  dence o f s t r u c t u r a l  fore,  river  marine s e d i m e n t a t i o n o f  the Upper T r i a s s i c .  o f the A l a s k a range  sediments  White  RECORD.  and e a r l y P e r m i a n t i m e ,  b y Y u k o n and A l a s k a was u p l i f t e d .  basi c lava  r e g i o n , near  river.  MESOZOIC  Permian,  t o have o c c u r r e d i n  t o a non-marine type o f  s e d i m e n t a t i o n o c c u r r e d i n the i n t e r i o r and N a t i o n  i n Mississippi-  unconformity  seas  d i d not  and t h e r e i s l i t t l e  evi-  b e t w e e n t h e T r i a s s i c and  Carboniferous strata.  I t i s concluded,  the P a l e o z o i c - M e s o z o i c u p l i f t  there-  was o f a r e g i o n a l  character. The synclines of  Upper T r i a s s i c  which  high r e l i e f ;  d e p o s i t s were l a i d  coincided approximately the Brooks,  down i n g e o -  with the present  areas  R o o k y M o u n t a i n , A l a s k a , and C o a s t  ranges. 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The absence o f  limestone  known h i g h e s t Upper T r i a s s i c s e d i m e n t s i n a l l o f A l a s k a and Yukon i n d i c a t e s u p l i f t , b e l i e v e d to be o f a r e g i o n a l c h a r a c t e r , and e r o s i o n a t the c l o s e o f T r i a s s i c time*. The their  coarse  d i s t r i b u t i o n shows  c l i n e s between  t h e J u r a s s i c sediments and  character of  t h a t t h e y were d e p o s i t e d i n g e o s y n -  l a n d masses.  D u r i n g the J u r a s s i c , the A l a s k a  and Brooks r a n g e s and c e n t r a l A l a s k a formed a p o s i t i v e  element.  The w e s t e r n end o f the O g i l v i e range and p o s s i b l y the whole range was above the s e a . A s y n c l i n a l b a s i n o c c u p i e d Yukon, i t s c e n t r a l a x i s b e i n g somewhere  interior  east o f the present  Coast range.  The w r i t e r b e l i e v e s t h a t t h i s n e g a t i v e element  was  from the J u r a s s i c geosyncline o f the P a c i f i c  separated  board the  a p o s i t i v e a r e a , w h i c h i s now  o f A l a s k a by  country  between the  The Y u k o n and volcanic  Middle  and  rocks.  of g r a n i t i c  folding  and  are  St. E l i a s  t u f f a c e o u s and  M i d d l e and  of d i f f e r e n t i a l  intrusion  southern Alaska.  o f the  Various  mountains.  probably and  U p p e r J u r a s s i c was  the  :  early  intrusion essen-  upwarp w h i c h r e s u l t e d  Coast  by  associated with  J u r a s s i c mountain b u i l d i n g  The  occupied  sediments of western  T h i s v o l c a n i c a c t i v i t y was  rock.  a period  r a n g e and  Lower J u r a s s i c  southern Alaska  manifestation of late  tially  Coast  sea-  i n the  r a n g e s o f w e s t e r n Yukon  and  r e g i o n a l adjustments e v i d e n t l y took  p l a c e i n t h e r e g i o n s t© the n o r t h and e a s t , but a c t u a l mountain b u i l d i n g have c e n t e r e d parallel  during  along  granitic  the  the  J u r a s s i d e r e v o l u t i o n appears  Pacific  intrusions  to  c o a s t a l r e g i o n , w i t h minor  i n the  interior  region.  Rapid  and  • ,  1  •  e r o s i o n accompanied at  least,  2  •:  r^" the u p l i f t s  was r e d u c e d  and t h e g r e a t e r p a r t  t o low r e l i e f  a t the close  of Alaska,  o f the J u r a s -  sic. During most of  t h e Lower C r e t a c e o u s ,  seas p r o b a b l y  o f A l a s k a w i t h t h e e x c e p t i o n o f the A l a s k a range  the Brooks  range,  a r e a s w h i c h were u n d e r g o i n g  justment.  The same was t r u e o f t h e C o a s t  was e i t h e r  still  as a h i g h t r a c t c o v e r e d what Mackenzie  under p o s i t i v e under e r o s i o n .  i s now t h e O g i l v i e  and p a r t s  s t r u c t u r a l ado f Yukon which  influence  or r e s t i n g  The L o w e r C r e t a c e o u s s e a range,  and p r o b a b l y a l s o t h e  mountains. activity prevailed  Orogenic ceous  tectonic  range  covered  d u r i n g the Middle  Creta-  when t h e f o l l o w i n g a r e a s were e l e v a t e d t o m o u n t a i n  ranges:  -  1 . The s i t e  o f the p r e s e n t Brooks  2. The a r e a s o u t h o f A l a s k a 3 . The w e s t e r n p a r t  range.  range.  o f the Mackenzie  m o u n t a i n s and t h e O g i l v i e  range. 4. The C o a s t  range  o f southwestern  This mountain b u i l d i n g Lower C r e t a c e o u s  was a c c o m p a n i e d  sediments  axes o f t h e r a n g e s )  range  the m a j o r  and d e p o s i t i o n o f U p p e r C r e t a c e o u s . s e d i -  well ceous  and the e a s t e r n s i d e  tectonic  With  existing  the exception o f the  o f the Mackenzie  time.  t h e r e f o r e , have a d e f i n i t e  geographic  mountains,  f e a t u r e s o f the northwestern C o r d i l l e r a  d e f i n e d e a r l y i n Upper C r e t a c e o u s sediments,  by deformation o f the  ( p r o g r e s s i v e l y g r e a t e r towards the  ments i n t h e i n t e r m o u n t a i n t r a c t s . Alaska  Yukon ( r e j u v e n a t e d ) •  features i n their  were  The U p p e r C r e t a r e l a t i o n s h i p to  distribution.  They  occur  -153i n Yukon n o r t h o f the central  and  b y way  Yukon t o near  The  sea  and  the  i n the  was  River region with  o f the M a c k e n z i e  of  Cretaceous  T h i s sea extended  b o u n d a r y , and  Porcupine  lowlands  main marine Upper  o f Yukon v a l l e y .  the Alaska-Yukon  through  Cretaceous  range,  northern Alaska.  i n v a s i o n was  tinuous  Ogilvie  up  the  probably the  con-  Upper  region.  TERTIARY RECORD.  The ing  Tertiary  r e c o r d i n Y u k o n i s one  o n a l a n d m a s s w h i c h was  o s c i l l a t o r y and, At  i n part,  the  close  s u b j e c t e d to u p l i f t  differential  o f the Mesozoic  l y w i t h d r a w n f r o m a l l o f what i s now late  Cretaceous  uplift and  Eocene time  v i g o r o u s mountain b u i l d i n g  range  e x i s t i n g ranges.  i s believed  e a s t e r n ranges late  Cretaceous  tended  through  where l a t e certain Coast  range  tion,  but  the  s e a s were  Y u k o n and  complete-  Alaska.  In  Cretaceous  sediments  i n r e g i o n s a d j a c e n t to  the  m a j o r d e f o r m a t i o n o f the A l a s k a  to have o c c u r r e d i n e a r l y E o c e n e t i m e .  o f the Mackenzie o r E o c e n e and  m o u n t a i n s were b u i l t  this  d e f o r m a t i o n may  the R i c h a r d s o n mountains  the r a n g e s  uplift  occurred.  may  have  The  i n the  have  to the Brooks  ex-  range,  I t seems  s o u t h o f the A l a s k a range  i n Y u k o n were u p l i f t e d  this  an  the whole r e g i o n underwent  Eocene m o u n t a i n b u i l d i n g  that  character.  The  of  character.  w i t h a g e n e r a l d e f o r m a t i o n o f the  already  was  and  of erosion act-  and  the  d u r i n g the Iaramide  revolu-  b e e n o f an e p e i r o g e n i c  Contemporaneous w i t h the M e s o z o i o - T e r t i a r y u p l i f t  the d e p o s i t i o n o f c o a l or l i g n i t e - b e a r i n g sediments  in  -  -154-  l o e a l b a s i n s between t h e m o u n t a i n r a n g e s .  Volcanic  activity  i n t h e l o w l a n d r e g i o n s o f t h i s age, p r e c e d e d , f o l l o w e d , o r was contemporaneous w i t h t h e Eocene d e p o s i t i o n * The post-Eocene r e c o r d o f Yukon i s l a r g e l y a p h y s i o g r a p h i c p r o b l e m w h i c h c e n t r e s around t h e i n t e r p r e t a t i o n o f e l e v a t i o n s and d e p r e s s i o n s o f t h e b a s e - l e v e l o f e r o s i o n .  It i s  g e n e r a l l y conceded t h a t i n t e r i o r Yukon was reduced to a penep l a i n sometime i n T e r t i a r y t i m e , and t h i s was accompanied by a g e n e r a l r e d u c t i o n o f t h e m o u n t a i n ranges,  p a r t i c u l a r l y the  Coast range and U u t z o t i n mountains i n Yukon.  But b e f o r e  ero-  s i o n had advanced t o t h i s l a t e s t a g e , t h e r e was a n u p l i f t w h i c h r e s u l t e d i n f o l d i n g and f a u l t i n g o f the Eocene s e d i m e n t s , and the s t r u c t u r e s developed  were t r u n c a t e d by t h e p e n e p l a i n o r  mature e r o s i o n s u r f a c e r e f e r r e d t o above• o c c u r r e d i n l a t e Eocene, O l i g o c e n e ,  The u p l i f t may have  o r Miocene time and was  contemporaneous w i t h t h e d e p o s i t i o n o f the Kenana g r a v e l o n t h e n o r t h f a c e o f the A l a s k a r a n g e , Miocene s t r a t a i n t h e v a l l e y o f the l o w e r Yukon r i v e r , and p o s s i b l y t h e w h i t e o f the K l o n d i k e .  channel  gravels  P l a n a t i o n o f the Yukon P l a t e a u r e g i o n and  r e d u c t i o n o f the b o r d e r i n g ranges t o mature r e l i e f f o l l o w e d t h e uplift.  QUATERNARY RECORD. I n P l i o c e n e o r P l e i s t o c e n e time  the n o r t h w e s t e r n  C o r d i l l e r a n r e g i o n was a g a i n u p l i f t e d ; the u p l i f t  apparently  "being g r e a t e s t i n t h e ranges b o r d e r i n g the Yukon p l a t e a u producing the great t r o u g h - l i k e form o f the present p l a t e a u .  -155T h i s u p l i f t , c o u p l e d w i t h a p r o b a b l e change i n c l i m a t e , resulted i n glaoiation.  Evidence  o f s e v e r a l i c e advances p r e -  v i o u s t o t h e l a s t g r e a t advance has been f o u n d n e a r the margins o f the g l a c i a t e d a r e a i n A l a s k a .  I t i s safe to say, t h e r e f o r e ,  t h a t the g l a c i a t e d r e g i o n s o f Yukon and A l a s k a were c o v e r e d  by  s u c c e s s i v e i c e s h e e t s , but t h a t the l a s t and p r o b a b l y g r e a t e s t advance s e r v e d t o d e s t r o y o r mask t h e e f f e c t s o f p r e v i o u s gressions.  The  pro-  age o f t h e l a s t g r e a t e x t e n s i o n has been  e s t i m a t e d i n the v a l l e y o f White r i v e r t o have been about c o n temporaneous w i t h the W i s c o n s i n p e r i o d o f e a s t e r n •• ' 1 • America* The  d i s t r i b u t i o n o f the Alaska-Yukon g l a c i a l  b e l i e v e d to represent  the a r e a s covered  s o u t h e r n Yukon was  The  i c e sheet  E a s t e r n Yukon was  w h i c h c o l l e c t e d on t h e w e s t e r n  g l a c i a t e d by i c e  s l o p e s o f t h e M a c k e n z i e mount-  I c e f r o m t h e O g i l v i e m o u n t a i n s , and p o s s i b l y f r o m the  K e e w a t i n i c e she e t , c o v e r e d p a r t s o f no r t h e a s t e r n Yukon. western  of  probably continuous w i t h the C o r d i l l e r a n i c e  of B r i t i s h Columbia.  ains*  deposits  by t h e maximum i c e  a d v a n c e , a r e shown i n F i g u r e 4 ( i n p o c k e t ) *  sheet  North  l i m i t o f t h e K e e w a t i n sheet  The  i n n o r t h e r n Yukon i s not  known; f a r t h e r s o u t h i t p e n e t r a t e d w e l l i n t o the M a c k e n z i e m o u n t a i n s , but a p p a r e n t l y d i d not  c r o s s the range.  P l e i s t o c e n e the n a r r o w A r c t i c s l o p e r e g i o n was n e a t h the sea t o a depth o f 500  During  the  submerged be-  f e e t , a f a c t e s t a b l i s h e d by 2  P l e i s t o c e n e f o s s i l s found a t v a r i o u s p o i n t s i n t h i s r e g i o n . The main v a l l e y s o f A l a s k a and Yukon p r o b a b l y date  to  1. Capps,S.R.- U.S.G.S.Prof.Pap. 170-A, pp.4-fa, 1931. 2. O ' N e i l l ,'J".»T.- 1913-18 C a n . A r c t i c Exp. , V o l . X I , p t . A , pp.1018, 1924.  -156-  the P l i o c e n e o r e a r l y P l e i s t o c e n e u p l i f t , when the l o w e r i n g  of  the g e n e r a l " b a s e - l e v e l r e s u l t e d i n v i g o r o u s e r o s i o n , w e l l o r g a n i s e d d r a i n a g e , and surface.  a deep entrenchment o f the o l d l a n d  I n many c a s e s the newer d r a i n a g e  channels  probably  f o l l o w e d c o u r s e s more o r l e s s c o i n c i d e n t w i t h the  ancient  drainage  case the  p a t t e r n o f the o l d land s u r f a c e .  I n any  p r e s e n t v a l l e y system i s , i n g e n e r a l , a p h y s i o g r a p h i c w h i c h was  feature  w e l l developed before the l a s t great g l a c i a t i o n .  t h e g l a c i a t e d r e g i o n t h e s e v a l l e y s have been p a r t i a l l y by g l a c i a l  d e p o s i t s and m o r a i n e s , t h e i r i n t e r l o c k i n g  In  filled  spurs  t r u n c a t e d , and p o s s i b l y they have been overdeepened i n p l a c e s . That many changes i n d r a i n a g e have t a k e n p l a c e s i n c e the main v a l l e y s were formed, p a r t i c u l a r l y i n t h e Yukon P l a t e a u p r o v i n c e , seems t o be a c e r t a i n t y .  Some o f the g r e a t v a l l e y s  a r e o c c u p i e d a t d i f f e r e n t p a r t s of t h e i r l e n g t h by p a r t s of different R.G.  streams.  M c C o n n e l l , who  A p a r t i c u l a r case i s a v a l l e y d e s c r i b e d states;  "This v a l l e y i s occupied  by  in  d i f f e r e n t po r t i o n s o f i t s course by the P e l l y , a b r a n c h o f K a l z a s r i v e r , Crooked creek, a p o r t i o n of Stewart r i v e r ,  Clear  c r e e k , F l a t c r e e k , and the l o w e r p o r t i o n o f the N o r t h F o r k o f 1  Klondike  river."  As t h i s p a p e r i s n o t i n t e n d e d t o be  an  a n a l y s i s o f the p h y s i o g r a p h y o f Yukon o r A l a s k a , the w r i t e r w i l l not p r e s e n t  a d i s c u s s i o n o f the v a r i o u s f a c t o r s on w h i c h  extensive drainage  r e v e r s a l s and changes have been p o s t u l a t e d  by d i f f e r e n t i n v e s t i g a t o r s i n t h i s r e g i o n .  He h a s , however,  embodied a number o f these h y p o t h e t i c a l o l d e r s t r e a m c o u r s e s a map  ( F i g u r e 4, i n p o c k e t ) .  I t may  be s a i d t h a t a t the  on  present  t i m e , a l l the t h e o r i e s o f o r i g i n a l d r a i n a g e c o u r s e s  must he r e g a r d e d as w o r k i n g h y p o t h e s e s r a t h e r t h a n as e s t a b l i s h e d f a c t s , a s few o f the supposed o r i g i n a l c o u r s e s have been examined t h r o u g h o u t t h e i r  length.  There a r e many minor t o p o g r a p h i c  f e a t u r e s w h i c h have  undoubtedly developed during Quaternary time.  Such a r e t e r -  races , of which there are three types: ( l ) rock~cut r i v e r r a c e s , (2)  h i g h - l e v e l t e r r a c e s not n e c e s s a r i l y connected w i t h  v a l l e y s , (3) The lift  ter-  g r a v e l , d r i f t , s a n d , and s i l t t e r r a c e s i n v a l l e y s .  f i r s t t y p e i n Yukon may be e x p l a i n e d e i t h e r b y r e c e n t upo r by stream d i v e r s i o n .  I n view o f t h e f a c t t h a t i t seems  c e r t a i n t h a t m a j o r s t r e a m d i v e r s i o n s have t a k e n p l a c e , and t h a t t h e s e t e r r a c e s o c c u r a l o n g p o r t i o n s o f streams b e l i e v e d t o be o c c u p y i n g v a l l e y s d i f f e r e n t t o t h o s e which they f o r m e r l y p i e d , i t i s best to favour the l a t t e r hypothesis.  occu-  The o r i g i n  o f such t e r r a c e s , which a r e common a l o n g Yukon r i v e r below t h e P e l l y r i v e r , w i l l n o t be e s t a b l i s h e d u n t i l more d e t a i l e d mapping has  been done and e l e v a t i o n s a r e c o o r d i n a t e d .  High-level  ter-  r a c e s w h i c h o c c u r on h i l l s i d e s and even on r i d g e t o p s a r e common f e a t u r e s p a r t i c u l a r l y i n the u n g l a c i a t e d r e g i o n .  These  are c a l l e d a l t i p l a n a t i o n t e r r a c e s by E a k i n , who p o s t u l a t e s  ••  that  -1 1  t h e y a r e due t o s o l i f l u c t i o n e f f e c t s . ~  That such t e r r a c e s  appear t o be r e s t r i c t e d t o l i t h o l o g i c a l l y d i s t i n c t i v e  rocks  such as h i g h l y i n d u r a t e d s e d i m e n t s o r h a r d , massive g r e e n s t o n e s i s i n support of Eakin's theory.  The t e r r a c e s o f u n c o n s o l i d a -  t e d m a t e r i a l w h i c h l i e a l o n g many o f t h e v a l l e y s o f Yukon, b o t h i n the g l a c i a t e d and u n g l a c i a t e d r e g i o n s , may be due t o  -1^8the  following  causes:  (1) Entrenchment by  present streams i n t o g l a c i a l  (2) Entrenchment by  p r e s e n t streams i n t o e x t r a - g l a c i a l d e p o s i t s  l e f t by (5)  o v e r b u r d e n e d streams d u r i n g the  deposits.  ice retreat.  Entrenchment by p r e s e n t t r i b u t a r y streams o f d e p o s i t s i n  t r i b u t a r y v a l l e y s , the  major v a l l e y s o f w h i c h have been  deepened by r i v e r d i v e r s i o n . ( 4 ) E n t r e n c h m e n t by  p r e s e n t streams i n d e p o s i t s of a r e a s ponded  d u r i n g g l a c i a t i o n by i c e damming. A s y m m e t r i c a l v a l l e y s are common f e a t u r e s these may  glaciated region;  o f the v a l l e y streams t o one influence  be due  i n the t i n -  i n some eases to  confinement  s i d e o f the v a l l e y due  of t r i b u t a r y s t r e a m s .  I n the m a j o r i t y  to  the  of cases  8  how-  e v e r , such v a l l e y s a p p e a r to have r e s u l t e d from d i f f e r e n t i a l i n s o l a t i o n a c t i n g on the  f r o z e n d e b r i s o f the v a l l e y  V a l l e y s l o p e s exposed to the t h a w i n g , and a r e  sun erode q u i c k l y due  s t e e p ; t h o s e away f r o m the  f r o z e n d e b r i s , are h e a v i l y t i m b e r e d , and creep r a t h e r t h a n by region  quick run-off.  to q u i c k  sun h o l d  their  e r o d e d by  Even i n the  ground-  glaciated  d i f f e r e n t i a l i n s o l a t i o n e f f e c t s are o c c a s i o n a l l y  p a r t i c u l a r l y above t i m b e r - l i n e is  are  sides.  seen,  where e r o s i o n by f r o s t a c t i o n  rapid. Volcanic  Quaternary. canic  The  a c t i v i t y also took place during  the  w r i t e r b e l i e v e s t h a t t h e main s t a g e s o f v o l -  a c t i v i t y followed  s h o r t l y a f t e r the main u p l i f t s  as  follows: (1) V o l c a n i c exemplified  a c t i v i t y a f t e r the  Oretaceous-Eocene  by t u f f s i n the Eocene s e d i m e n t s .  uplift,  -159-  (2) V o l o a i i i c a c t i v i t y a f t e r the l a t e Eocene o r Miocene  uplift,  e x e m p l i f i e d by l a v a s w h i c h a r e t r u n c a t e d by the Yukon p l a t e a u . (3) V o l c a n i c a c t i v i t y a f t e r the P l i o c e n e o r e a r l y P l e i s t o c e n e u p l i f t , e x e m p l i f i e d by l a v a s i n the v a l l e y b o t t o m s , r e c e n t f l o w s and c i n d e r - c o n e s , and the p r e s e n t  the ash d e p o s i t  eruptions  south o f l a t i t u d e  i n the A l e u t i a n I s l a n d s .  lava 63,  F i g u r e 17. E f f e c t s of d i f f e r e n t i a l i n s o l a t i o n on the mountains between T e s l i n r i v e r and Q u i e t l a k e . Southwest-facing slopes.  Northeast-facing  F i g u r e 18. Recent l a v a f l o w a t the mouth o f Pelly river.  slopes.  APPENDIX. BIBLIOGRAPHY. ( O n l y the main p u b l i c a t i o n s r e f e r r e d t o are  listed.)  General. B r o o k s , A.H.-  "The g e o l o g y and geography o f A l a s k a , " G e o l . Surv. P r o f . Pap, 4 5 , 1906,  B r o o k s , A.H.  and K i n d l e , E.M." P a l e o z o i c and a s s o c i a t e d r o c k s o f the Upper.Yukon", G e o l , Soc. Amer., V o l . XIX, 1908.  C a i r n e s , D.D.-  " D i f f e r e n t i a l e r o s i o n and e q u i p l a n a t i o n i n p o r t i o n s o f Yukon and A l a s k a . " G e o l , Soc. Am., V o l . 2 3 , pp. 333-348, 1912. •; - Can. 1913.  Capps, S.R. Dawson, G.M.  G e o l . S u r v . Guide Book 10,  - " G l a o i a t i o n i n A l a s k a , " U.S. Pap. 170. 1932,  pp,  U.S.  51-104,  Geol. Surv. P r o f .  and M c C o n n e l l , R.G. - "Report o f an e x p l o r a t i o n i n Yukon d i s t r i o t N.W.T.," Can, G e o l . Surv. no. 629, 1898. e  Hayes, C.W.  - "An e x p e d i t i o n t h r o u g h the Yukon d i s t r i c t , " • Nat.•Geog. Mag. , V o l . I V , . l 8 9 2 .  K i r k , E d w i n - " O r d o v i c i a n , S i l u r i a n , and D e v o n i a n o f A l a s k a " , B u l l . G e o l . Soc. Amer. ( a b s t r a c t ) , V o l . 40, p. 227, 1929. Mart i n , G.C.  - "The Mesozoic s t r a t i g r a p h y o f A l a s k a , " G e o l . S u r v . B u l l . 776, 1926.  U.S.  M c C o n n e l l , R.G. - "Note on the s o - c a l l e d b a s a l g r a n i t e o f t h e Yukon V a l l e y , " Amer. G e o l . , V o l . XXX, 1902. M e r t i e , J.B.  j r . - "Mountain b u i l d i n g i n A l a s k a , " S c i . , 5 t h s e r . , v o l , XX,.pp.101-124.  Am.  Jour.  H o r d e n s k i o l d , 0 . - " S u r f a c e geology o f the Yukon T e r r i t o r y , " Amer. G e o l . , v o l . X X I I I , I 8 9 9 . O ' H e i l l , J . J . - "The geology o f the A r c t i c c o a s t o f Canada, west o f Kent P e n i n s u l a , " 1913-18 Can. A r c t i c Exped., Rpt. V o l . X I , p t . A, 1924.  Ransome, F . l . - "Problems o f N o r t h A m e r i c a n G e o l o g y , " Y a l e P r e s s , 1913. . R u s s e l l , I.C. - "Notes on t h e s u r f a c e g e o l o g y o f A l a s k a , " G e o l . S o c . Am., V o l . 1, pp. 7 2 - 1 5 5 , I89O. , S p e n c e r , A.C. - " P a c i f i c mountain system i n B r i t i s h Columbi and A l a s k a , " G e o l . S o c . Am., V o l . X I V , 1 ? 0 5 . S p u r r , J . E . - "Geology o f t h e Yukon G o l d d i s t r i c t , " U.S. G e o l . S u r v . 18th An. R p t . , p t . 5, I898.  Yukon.  R e p o r t s a n d Memoirs o f t h e G e o l o g i c a l Survey C a i r n e s , D.D.-  o f Canada.  "Conrad and. V/hitehorse m i n i n g R p t . 1908.  districts"  - "Lewes and N o r d e n s k i o l d R i v e r s c o a l Mem. 5» 1910.  district  - " I h e a t o n d i s t r i c t , " Mem. 3 1 , 1912, - "Portions of A t l i n / 1913. '  d i s t r i c t , B.C. ," Mem, 57, ' ' ,.'  - "The Yukon-Ala ska i n t e r n a t i o n a l boundary between Yukon and P o r c u p i n e r i v e r s , " Mem. 67, 1914. ' • - "Upper White R i v e r d i s t r i c t , " Mem. 50, 1915. - "Wheaton d i s t r i c t , " Sum. R p t . 1915* 1916. - " I Q o t a s s i n a r e a " Sum. Rpt. I916, 1917. 5  - " S c r o g g i e , B a r k e r , T h i s t l e , and K i r k m a n c r e e k s , " Mem. 97, 1917. C a m s e l l , C.  - " P e e l r i v e r and t r i b u t a r i e s , " An. R p t . , V o l . X V I , p t . CG, 1906.  C o c k f i e l d , W.E. - " S i x t y m i l e and l a d u e R i v e r s a r e a , " Mem. 123, 1921. - "Geology and o r e d e p o s i t s o f Keno H i l l , Mayo d i s t r i c t , " Sum. R p t . 1923, p t . A, 1924. - "Upper Beaver R i v e r a r e a , " Sum. Rpt. 1924, p t . A, 1925* - " E x p l o r a t i o n s between A t l i n and T e l e g r a p h c r e e k s , B.C. ," Sum. R p t . 1925, p t . A, 1926. - " A i s h i h i k l a k e d i s t r i c t , " Sum. R p t . 1926, p t •• ..;.• •.• A.,  1  9  2  7  .  V  '  -iii- "Lezadeash Lake a r e a , " Sum. Rpt. 1 9 2 ? , p t . .A, 1 9 2 8 . - " L i t t l e Salmon A r e a , " Sum, Rpt. 1 9 2 8 , p t . A ,  G o c k f i e l d , W.E.  .1929.  C o c k f i e l d , W.E.  and B e l l , A.H. - "Whitehorse d i s t r i c t , " Mem. 1 5 0 , 1926.  G w i l l i m , J.G, - " A t l i n M i n i n g d i s t r i c t , B.C.," An. Vol.'  Keele, J .  XII,  pt,  B,  Rpt.,  19.01.  - "Upper S t e w a r t R i v e r r e g i o n , " An. R p t . , V o l . X V I , pt.. G, 1 9 0 6. ' - "A r e c o n n a i s s a n c e a c r o s s t h e M a c k e n z i e Mount a i n s , on the P e l l y , R o s s , and G r a v e l r i v e r s , " Rpt.  M c C o n n e l l , R.G.  I9IO,  - " S t e w a r t r i v e r , " An, R p t . , V o l . X I I I , p t . A, 1 9 0 0 .  - " M a o m i l l a n r i v e r , " Sum,  Rpt. 1 9 0 2 , pt.A,  1903»  - " K l o n d i k e g o l d f i e l d s , " An. R p t . , V o l * p t . B , 1905. - "Kluane M i n i n g d i s t r i c t , " Sum. .pt. A, 1905.  XIV,  R p t . 1904 ,  - "Headwaters of White r i v e r , " Sum. p t . 'A, 1 9 0 6 .  Rpt. 1 9 0 3 ,  Alaska. B u l l e t i n s and P r o f e s s i o n a l papers o f the U n i t e d S t a t e s G e o l o g i c a l Survey. Atwood, W.W.  - "Geology and m i n e r a l r e s o u r c e s o f p a r t s o f Alaska Peninsula," B u l l . 4 6 7 , 1 9 1 1 .  B r o o k s , A.H.  - "A R e c o n n a i s s a n c e i n t h e Tanana and White R i v e r b a s i n s , " 2 0 t h An. R p t . , p t . V I I , 1 9 0 0 * - "A R e c o n n a i s s a n c e f r o m P y r a m i d Harbour to E a g l e C i t y , " 2 1 s t An, R p t . , p t . I I , 1 9 0 0 . - "Mount M c K i n l e y r e g i o n , " P r o f . pap. 7 0 ,  1911.  Brown, J . S .  - "Hixon P o r k c o u n t r y , " B u l l . 7 8 3 , 1 9 2 6 .  Capps, S.R.  - "Bonnifield region," B u l l . 5 0 1 , 1 9 1 2 . - "Kantishna d i s t r i c t , " B u l l . • 6 8 7 , 1 9 1 9 * - " W i l l o w Creek d i s t r i c t , " B u l l . 6 0 7 , 1 9 1 5 .  "17"  Gapps, S.R.  - " E a s t e r n p o r t i o n o f Mount M c K i n l e y N a t i o n a l p a r k , " i n B u l l . 8 3 6 , 1933. - " l a k e C l a r k - M u l c h a t n a r e g i o n , " B u l l . 824, 1931. - "Mount S p u r r r e g i o n , " B u l l . 8 1 0 , 1930. - "Chisina-Y/hite R i v e r d i s t r i c t , " B u l l . 630, 1916.  Capps, S.R. and J o h n s o n , B . I . - " E l l a r n a r d i s t r i c t , " B u l l . 342, 1913. C h a p i n , T. - " N e l c h i n a - S u s i t n a  region," B u l l .  668, 1918.  E a k i n , H.M. - "Yukon-Koyukuk r e g i o n , " B u l l . 6 3 1 , 1916. - "Cosna-Nowitna r e g i o n , " B u l l . 6 6 7 , 1918. H a r r i n g t o n , G.I. - " A n v i k - A n d r e a f s k i 1918.  r e g i o n , " B u l l . 683.  l e f f i n g w e l l , E. de K. - "Canning R i v e r r e g i o n , " P r o f . pap. 109 * 1919Maddren, A.G. - " G e o l o g i c a l i n v e s t i g a t i o n s a l o n g t h e Canada** A l a s k a boundary," B u l l . 5 2 0 , 1912. Mart i n , G.C., J o h n s o n , B.L., and G r a n t , U.S. - "Kenai s u l a , " B u l l . 5 8 7 , 1915.  Penin-  M a r t i n , G.C. and K a t z , E . J . - " I l l i a m n a r e g i o n , " B u l l . 4 8 5 , 1912. . :  M e n d e n h a l l , W.C. - "Geology o f t h e c e n t r a l Copper R i v e r r e g i o n , " P r o f , pap. 4 1 , 1 9 0 5 . M e r t i e , J.B.  j r . - "The g o l d p l a c e r s o f t h e Tolovana t r i c t ," B u l l . 6 6 2 , 1918.  dis-  - "Chandalar d i s t r i c t , " i n B u l l . 7 7 3 , 1 9 2 5 . - "Chandalar-Sheenjek d i s t r i c t , " i n B u l l . 810, ' ' • 1930. • • • • - " E a g l e - C i r c l e d i s t r i c t , " B u l l . 8 l 6 , 1930. - "Dennison Fork d i s t r i c t , " B u l l . 8 2 7 , 1932. - " T a t o n d u k - N a t i o n d i s t r i c t , " B u l l . 8 3 6 , 1933. M e r t i e , J . B . j r . a n d H a r r i n g t o n , G.L. - "Ruby-Kuskokwim r e g i o n , " B u l l . 754, 1924. M o f f i t , F.H. - "Nome and Grand C e n t r a l q u a d r a n g l e s , " B u l l . 533, 1913. - "Headwater r e g i o n s o f Gulkana a n d S u s t i n a r i v e r s . " B u l l . 4 9 8 , 1912.  M o f f i t , F.H. - "Broad P a s s r e g i o n , " B u l l .  608 ,  - "Upper C h i t i n a v a l l e y , " B u l l .  1915.  675,  1918.  - " S l a n a d i s t r i c t , Upper Copper R i v e r r e g i o n , " B u l l . 824-B, 1931. M o f f i t , F.H. and Capps, S.R. - "Geology and m i n e r a l r e s o u r ces o f H i z i n a d i s t r i c t , " B u l l . 4 4 8 , 1911. M o f f i t , F.H. and K n o p f , A. - "Habesna-White R i v e r d i s t r i c t , " B u l l . 417, 1910. P r i n d l e , L.M. - " F o r t y m i l e q u a d r a n g l e , " B u l l . 3 7 5 , 1909* - " C i r c l e q u a d r a n g l e , " B u l l . 5 3 8 , 1913* - "Fairbanks  quadrangle -" B u l l . 5 2 5 ,  1913*  S m i t h , P.S. and M e r t i e , J . B . j r . - "Geography and g e o l o g y o f northwestern A l a s k a , " B u l l . 815, 1930. S t e i d t m a n n , E. and C a t h c a r t , S.H. - "Geology o f t h e Y o r k t i n d e p o s i t s , " B u l l . 7 3 3 , 1922.  Figure 4 i n pocket (1)  illustrates:  The main t o p o g r a p h i c d i v i s i o n s o f Yukon and A l a s k a (brown dashed l i n e s ) . The brown l i n e s show t h e a p p r o x i m a t e t r e n d s o f t h e mountain r a n g e s .  (2) The l i m i t s o f W i s c o n s i n g l a c i a t i o n ( a f t e r Capps i n U.S.G.S. P r o f . pap. 170-A, w i t h some m o d i f i c a t i o n s ) . (3) H y p o t h e t i c a l major r i v e r s b e f o r e g l a c i a t i o n , after: 1. R.G. M c C o n n e l l , C.G.S. An. R p t . v o l . . X V , p. 24A. 2. H.M. E a k i n , U.S.G.S. B u l l . 631, pp. 6 9 - 7 2 . 3 . J.B. M e r t i e , j r . and G . l . H a r r i n g t o n , U.S.G.S. B u l l . 745» PP« 7 and 8 . 4. C a i r n e s , D.D., C.G.S. Mem. 50, pp. 6 0 - 6 2 . 5 . B r o o k s , A.H., U.S.G.S. 2 1 s t An. R p t . , p t . I I , pp. 3 5 4 - 3 5 5 , 1 9 0 0 .  M A P OF  A L A S K A 80m.* 1 in. (Appro*.)  L E G END.  Superficial  deposits  in valleys.  P l e i s t o c e n e 3iid Recervt.  Eocene t'J .sediments. Tertiary  •  Generally non- calcareous Sediments Mesozoic.  Limestone - Triassic and Carboniferous .  Chertu Upper-  sediments Paleozoic.  Limestone, shale, slate, quart3itc , chertLon/er Paleozroi'c.  Tindir >^rovp~  Precambrian (?).  Yukon group Precambrisn.  Acid and basic v o l c a n i c s T e r t i a r y and Recent . -  Granitic intrusi'/es. Upper J u r a s s i c and Cretaceous.  Older voicani'cs-. Carboniferous to J u r a s s i c -  YUKON TERRITORY Scale  16 M i l e s t o 1 I n c h  

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