| OCR Text |
Show GEOLOGY O F T H E S H E E P R O C K MOUNTAINS, T O O E L E AND JUAB COUNTIES, UTAH b y R o b e r t E . Cohenour 3 8 7 9 9 1 T h i s T h e s i s f o r t h e P h . D. d e g r ee by R o b e r t E . C o h e n o ur h a s b e e n a p p r o v e d by ACKNOWLEDGEMENTS V a l u a b l e a s s i s t a n c e h a s b e e n r e c e i v e d f r o m m a n y p e o p l e d u r i ng t h i s s t u d y . I a m p a r t i c u l a r l y i n d e b t e d to D r . N o r m a n C. W i l l i a m s of t h e U n i v e r s i t y of U t a h f o r h i s i n t e r e s t and s u g g e s t i o n s ; to Dean A. J. E a r d i e y , P r o f e s s o r s W. L. S t o k e s , F . W. C h r i s t i a n s e n , B. S. S t r i n g h a m , and Max P . E r i c k s o n f o r s u g g e s t i o n s and c r i t i c a l r e a d i ng of t h e m a n u s c r i p t . The p r e p a r a t i o n of t h i s r e p o r t was i n f l u e n c e d by d i s c u s s i o n s with Max D. C r i t t e n d e n and H. T. M o r r i s of the U. S. G e o l o g i c a l S u r v e y , G r a n t S t e e l e and Dwight A r n o l d of t h e Gulf Oil C o r p o r a t i o n , R. H. O l s o n and R. C. B r i g h t , c o l l e a g u e s at the U n i v e r s i t y of U t a h , and B . J. S h a r p and A . E . G r a n g e r o f t h e U. S. A t o m i c E n e r g y C o m m i s s i o n. E s p e c i a l t h a n k s a r e due t h e l a t e M. A. S t a i n b r o o k , C h r i s t i na L o c h m a n B a l k , A. R. P a l m e r , W a l t e r S a d l i c k , C h e s t e r A r n o l d, a n d R. R. Brown f o r a i d in i d e n t i f y i n g f o s s i l s. M r . R. C. B r i g h t r e n d e r e d i n v a l u a b l e a s s i s t a n c e in i d e n t i f y i ng t h e C a m b r i a n and O r d o v i c i a n f a u n a s. T h e w r i t e r i s i n d e b t e d to W i l l i a m S a l i s b u r y f o r a s s i s t a n c e and s u g g e s t i o n s in t h e p r e p a r a t i o n of t h e i l l u s t r a t i o n s. E s p e c i a l t h a n k s a r e due m y wife, G e n e v r a , for h e r p a t i e n c e and u n d e r s t a n d i n g , and f o r t y p i n g at a l l s t a g e s of t h i s work. CONTENTS Pa^e ABSTRACT . , i INTRODUCTION . 1 P u r p o s e and s c o p e . . . . ... • • 1 L o c a t i o n a n d a c c e s s i b i l i t y • 1 G e o g r a p h y 2 T o p o g r a p h y and d r a i n a g e .. 2 C l i m a t e a n d . y e g e t a t i o n . . . . . . 4 P r e v i o u s g e o l o g i c i n v e s t i g a t i o n s 6 F i e l d w o r k • 7 ACKNOWLEDGEMENTS 9 STRATIGRAPHY . 10 G e n e r a l s t a t e m e n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 P R E C A M B R I A N ROCKS 11 G e n e r a l s t a t e m e n t 11 S h e e p r o c k s e r i e s (new n a m e ) \ . 11 G e n e r a l s t a t e m e n t • 11 D i s t r i b u t i o n and t h i c k n e s s 12 T o p o g r a p h i c e x p r e s s i o n 12 L i t h o i o g y • 13 F i e l d i d e n t i f i c a t i o n 15 D u t c h P e a k t i i l i t e (new n a m e ) . . . . . . . . . . . . . . . . . . . . . . . . . . 15 N e e d of n e w n a m e 15 D i s t r i b u t i o n and t h i c k n e s s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 T o p o g r a p h i c e x p r e s s i o n . # 17 L i t h o i o g y 17 F i e l d i d e n t i f i c a t i o n 19 C o r r e l a t i o n • • 19 M u t u a i ( ? ) f o r m a t i o n * • •• 21 G e n e r a l s t a t e m e n t • • • • • • • • • • • • • • • • 21 D i s t r i b u t i o n and t h i c k n e s s . . . . . . . . . . . . . . . . . . . . . . 21 T o p o g r a p h i c e x p r e s s i o n 22 L i t h o i o g y 22 F i e l d i d e n t i f i c a t i o n ....... 24 C o r r e l a t i o n • 24 P r e c a m b r i a n c o r r e l a t i o n 25 P r e c a m b r i a n - C a m b r i a n c o n t a c t 27 P a g e CAMBRIAN SYSTEM 29 G e n e r a l s t a t e m e n t 29 t T i n t i c q u a r t z i t e 29 G e n e r a l s t a t e m e n t 29 D i s t r i b u t i o n and t h i c k n e s s 29 T o p o g r a p h i c e x p r e s s i o n 31 L i t h o i o g y 31 F i e l d i d e n t i f i c a t i o n 32 C o r r e l a t i o n 33 ( Ophir g r o u p • 35 G e n e r a l s t a t e m e n t 35 L i m i t s . . . . . . . . . . 39 C o n c l u s i o n s . 40 , P i o c h e s h a l e . 40 D i s t r i b u t i o n a n d t h i c k n e s s 40 T o p o g r a p h i c e x p r e s s i o n 41 L i t h o i o g y 41 F i e l d i d e n t i f i c a t i o n . i.. 42 Age a n d c o r r e l a t i o n 43 , B u s b y q u a r t z i t e 44 D i s t r i b u t i o n and t h i c k n e s s 44 T o p o g r a p h i c e x p r e s s i o n • 44 L i t h o i o g y 44 F i e l d i d e n t i f i c a t i o n 45 Age and c o r r e l a t i o n 45 M i l l a r d f o r m a t i o n 48 G e n e r a l „ ; .... 48 D i s t r i b u t i o n , a n d t h i c k n e s s 48 T o p o g r a p h i c e x p r e s s i o n •.. 49 L i t h o i o g y -V* 49 F i e l d i d e n t i f i c a t i o n • 50 Age and c o r r e l a t i o n ... 50 B u r r o w s l i m e s t o n e 52 G e n e r a l • • • . . . • 52 B u r n t C a n y o n f o r m a t i o n 53 D i s t r i b u t i o n and t h i c k n e s s • 53 T o p o g r a p h i c e x p r e s s i o n 53 L i t h o i o g y 53 F i e l d i d e n t i f i c a t i o n 54 Age a n d c o r r e l a t i o n 54 P a g e Dome Limestone 55 D i s t r i b u t i o n a n d t h i c k n e s s 55 T o p o g r a p h i c e x p r e s s i o n 55 L i t h o i o g y 55 F i e l d i d e n t i f i c a t i o n 55 Age a n d c o r r e l a t i o n 56 C o n d o r f o r m a t i o n 56 G e n e r a l 56 D i s t r i b u t i o n and t h i c k n e s s ••••• 58 T o p o g r a p h i c e x p r e s s i o n • 58 F i e l d i d e n t i f i c a t i o n 59 Age a n d c o r r e l a t i o n 59 j S w a s e y l i m e s t o n e • 60 G e n e r a l 60 D i s t r i b u t i o n and t h i c k n e s s 60 T o p o g r a p h i c e x p r e s s i o n 60 L i t h o i o g y 60 F i e l d i d e n t i f i c a t i o n ; % . 60 Age and c o r r e l a t i o n . 61 W h e e l e r f o r m a t i o n ••••• 61 D i s t r i b u t i o n and t h i c k n e s s 61 T o p o g r a p h i c e x p r e s s i o n • 61 L i t h o i o g y • 62 F i e l d i d e n t i f i c a t i o n . 62 Age and c o r r e l a t i o n • 62 , M a r j u m f o r m a t i o n • 63 G e n e r a l 63 D i s t r i b u t i o n and t h i c k n e s s 63 T o p o g r a p h i c e x p r e s s i o n 64 L i t h o i o g y 64 F i e l d i d e n t i f i c a t i o n 65 Age and c o r r e l a t i o n • • 66 C o l e C a n y o n d o l o m i t e 67 D i s t r i b u t i o n and t h i c k n e s s 67 T o p o g r a p h i c e x p r e s s i o n 67 L i t h o i o g y 67 F i e l d i d e n t i f i c a t i o n 68 Age and c o r r e l a t i o n 69 Opex f o r m a t i o n ••••••••• 69 D i s t r i b u t i o n and t h i c k n e s s 69 T o p o g r a p h i c e x p r e s s i o n • 70 L i t h o i o g y • 70 F i e l d i d e n t i f i c a t i o n 71 Age a n d c o r r e l a t i o n 71 P a g e A j a x f o r m a t i o n .. 73 D i s t r i b u t i o n and t h i c k n e s s , 73 T o p o g r a p h i c e x p r e s s i o n 74 L i t h o i o g y 74 F i e l d i d e n t i f i c a t i o n 75 Age and c o r r e l a t i o n 75 C a m b r i a n c o r r e l a t i o n 76 C a m b r i a n - O r d o v i c i a n c o n t a c t 85 ORDOVICIAN SYSTEM 87 G e n e r a l s t a t e m e n t • •• 87 H o u s e and F i l l m o r e f o r m a t i o n s u n d i f f e r e n t i a t e d 89 D i s t r i b u t i o n a n d t h i c k n e s s 89 T o p o g r a p h i c e x p r e s s i o n 90 L i t h o i o g y 90 F i e l d i d e n t i f i c a t i o n 91 Age a n d c o r r e l a t i o n 91 Wah Wan f o r m a t i o n •••• '.. 92 D i s t r i b u t i o n and t h i c k n e s s •••• 92 T o p o g r a p h i c e x p r e s s i o n 93 L i t h o i o g y . . . 93 F i e l d i d e n t i f i c a t i o n 94 Age and c o r r e l a t i o n 94 J u a b f o r m a t i o n 95 D i s t r i b u t i o n and t h i c k n e s s 95 T o p o g r a p h i c e x p r e s s i o n 95 L i t h o i o g y 95 F i e l d i d e n t i f i c a t i o n 96 Age and c o r r e l a t i o n . 96 K a n o s h s h a l e 97 D i s t r i b u t i o n and t h i c k n e s s 97 T o p o g r a p h i c e x p r e s s i o n 98 L i t h o i o g y 98 F i e l d i d e n t i f i c a t i o n 99 Age a n d c o r r e l a t i o n 99 Swan P e a k q u a r t z i t e 100 D i s t r i b u t i o n and t h i c k n e s s 100 T o p o g r a p h i c e x p r e s s i o n 101 F i e l d i d e n t i f i c a t i o n 101 L i t h o i o g y .... 101 Age and c o r r e l a t i o n 103 P a g e F i s h H a v e n d o l o m i t e . . . . . . . . . . . . • • ••• . . . . . . 103 G e n e r a l ......... .. 103 D i s t r i b u t i o n and t h i c k n e s s •••• * !H T o p o g r a p h i c e x p r e s s i o n 105 L i t h o i o g y , .. .. 105 F i e l d i d e n t i f i c a t i o n 106 Age a n d c o r r e l a t i o n 107 O r d o v i c i a n - S i i u r i a n b o u n d a r y 108 SILURIAN SYSTEM .......... 112 G e n e r a l s t a t e m e n t ••••• ••••• 112 L a k e to wn d o l o m i t e 112 D i s t r i b u t i o n a n d t h i c k n e s s 112 T o p o g r a p h i c e x p r e s s i o n 113 L i t h o i o g y .. 113 F i e l d i d e n t i f i c a t i o n 114 Age a n d c o r r e l a t i o n . 114 S i l u r i a n - D e v o n i a n c o n t a c t 116 DEVONIAN SYSTEM 117 G e n e r a l s t a t e m e n t . . . . « . . . 117 Sevy d o l o m i t e 117 D i s t r i b u t i o n and t h i c k n e s s 117 T o p o g r a p h i c e x p r e s s i o n 118 L i t h o i o g y . . . . . . . . . . . • i.%9 F i e l d i d e n t i f i c a t i o n . . . . . . . . . 119 Age and c o r r e l a t i o n 119 S i m o n s o n d o l o m i t e 120 D i s t r i b u t i o n and t h i c k n e s s 120 T o p o g r a p h i c e x p r e s s i o n 120 L i t h o i o g y • • • I20 F i e l d i d e n t i f i c a t i o n 121 Age and c o r r e l a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . « 122 V i c t o r i a a n d P i n o n P e a k f o r m a t i o n s u n d i f f e r e n t i a t e d 124 D i s t r i b u t i o n and t h i c k n e s s 124 T o p o g r a p h i c e x p r e s s i o n 124 L i t h o i o g y .......... 124 F i e l d i d e n t i f i c a t i o n 125 Age a n d c o r r e l a t i o n 126 D e v o n i a n - M i s s i s s i p p i a n c o n t a c t 126 P a g e MISSISSIPPIAN SYSTEM 127 G e n e r a l s t a t e m e n t 127 M a d i s o n l i m e s t o n e 127 D i s t r i b u t i o n and t h i c k n e s s 127 T o p o g r a p h i c e x p r e s s i o n 128 L i t h o i o g y 128 F i e l d i d e n t i f i c a t i o n 129 Age and c o r r e l a t i o n 129 D e s e r e t - H u m b u g f o r m a t i o n 132 G e n e r a l 132 D i s t r i b u t i o n and t h i c k n e s s 132 T o p o g r a p h i c e x p r e s s i o n 133 L i t h o i o g y 133 F i e l d i d e n t i f i c a t i o n 134 Age and c o r r e l a t i o n 134 G r e a t B l u e f o r m a t i o n 135 D i s t r i b u t i o n and t h i c k n e s s 135 T o p o g r a p h i c e x p r e s s i o n 136 L i t h o i o g y 136 F i e l d i d e n t i f i c a t i o n 139 Age and c o r r e l a t i o n 140 PENNSYLVANIAN SYSTEM 142 O q u i r r h f o r m a t i o n •• 142 RESUM& OF P R E C A M B R I A N AND P A L E O Z O I C HISTORY 143 P r e c a m b r i a n . • 143 C a m b r i a n 145 O r d o v i c i a n 146 S i l u r i a n 146 D e v o n i a n • 147 M i s s i s s i p p i a n 148 P e n n s y i v a n i a n and l a t e r p e r i o d s . 149 C R E T A C E O U S ( ? ) - T E R T I A R Y ( ? ) ROCKS 150 G e n e r a l s t a t e m e n t 150 T E R T I A R Y ROCKS 151 G e n e r a l s t a t e m e n t 151 QUATERNARY 152 G e n e r a l s t a t e m e n t 152 P a g e IGNEOUS ROCKS . . . . . . . . 153 G e n e r a l d i s t r i b u t i o n , . . . 153 I n t r u s i v e r o c k s • . • • • 153 P r e c a m b r i a n ( ? ) s i l l 153 W e s t T i n t i c m o n z o n i t e s t o c k . . . . . . . . . . . . . . . . . . . . . . . 154 S h e e p r o c k g r a n i t e s t o c k • . • . . • • • • • • • • • • * • • • • • • . • . . . . . . . . 156 E x t r u s i v e r o c k s «„ 159 G e n e r a l s t a t e m e n t . . . . . . . . . . . . . . . . . . . . . 159 E x t r u s i v e s in t h e W e s t T i n t i c a r e a 160 E x t r u s i v e s f l a n k i n g the S h e e p r o c k s t o c k 160 E x t r u s i v e s f l a n k i n g t h e S i m p s o n M o u n t a i n s 160 V o l c a n i c s in A l l i s o n K n o l l s 161 S T R U C T U R E o » . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a . . . . . . . . . . . 162 M a j o r f e a t u r e s 162 F o l d s . 162 S h e e p r o c k m o n o c l i n e . 162 P o l e C a n y o n a n t i c l i n e 162 D e a t h C a n y o n a n t i c l i n e 163 F a u l t s . 164 S h e e p r o c k t h r u s t 164 O l d e r n o r m a l f a u l t s •• ... 166 P o l e C a n y o n t h r u s t 167 L i o n H i l l a n d r e l a t e d n o r t h f l a n k t h r u s t s 168 L o w - a n g l e , s t r i k e - s l i p f a u l t s 169 M i o c e n e n o r m a l f a u l t i n g 170 P l i o c e n e f a u l t m o v e m e n t s 171 P l e i s t o c e n e and R e c e n t f a u l t m o v e m e n t s 171 O r o g e n i c p h a s e s . . . 172 G e n e r a l s t a t e m e n t - 172 C e d a r H i l l s o r o g e n y ( ? ) - M i c i - C r e t a c e o u s p h a s e .. 172 E a r l y L a r a m i d e o r o g e n y - M o n t a n a p h a s e . . . . . . . . . . . . . . . . 172 M i d - L a r a m i d e o r o g e n y ( ? ) - P a i e o c e n e p h a s e . . . . . . . . . . . . . 174 L a t e L a r a m i d e o r o g e n y 175 B a s i n and R a n g e p h a s e . . . . . . « ; . . . . . . . . . . . . . 175 GEOM^ORPHOLOGY . . . . . . . . » . « . . « . . • • « • • » • « • » • » < » • • • . . . . o . . 177 G e n e r a l f e a t u r e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 F a u l t s c a r p s , „ „ 0 , 178 Gene r a l . o . . . . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • • . • • . • • » • • • 178 West F l a n k f a u l t , 178 S o u t h F l a n k f a u l t . . . 178 N o r t h and e a s t f l a n k i n g f a u l t s 179 P a g e P e d i m e n t s .... . . . . . . . . . . . . . . . . • 179 G e n e r a l .. . . . . . . . 179 H i g h - l e v e l p e d i m e n t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 L o w - l e v e l p e d i m e n t s • 180 A l l u v i a l f a n s .... . . . . . . . . . . . . . . . . • . 180 L a c u s t r i n e l a n d f o r m s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 G l a c i a l l a n d f o r m s . . . . . . . . . . . . . . . . . . . . 181 ECONOMIC G E O L O G Y . . . . 183 O r e d e p o s i t s • 183 H i s t o r y and p r o d u c t i o n 184 C o l u m b i a d i s t r i c t 185 L o c a t i o n 185 L e a d - z i n c v e i n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 B l u e B e l l d i s t r i c t .... 188 L o c a t i o n . . . . . . . . . . . . . . . . . . . v . . • • ••• • • • 188 L e a d - z i n c v e i n s •»........ . . . . . • . • . • • • 189 E r i c k s o n d i s t r i c t . ... . . . . . . . . . . . . . . . . . . . . . . 190 L o c a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • • 190 C o p p e r - f l u o r i t e v e i n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • 190 L e a d - z i n c v e i n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 M a n g a n e s e - f l u o r i t e - u r a n i u m v e i n s • • . . * . • • • • • • • • • • # « • • • * » 193 W o l f r a m i t e - q u a r t z v e i n s 194 P e g m a t i t e d e p o s i t s 195 W a t e r s u p p l y 198 G e n e r a l s t a t e m e n t 198 N o r t h s l o p e s p r i n g s 198 South s l o p e s p r i n g s 199 W e s t s l o p e s p r i n g s 200 L o o k o u t H i l l s a r e a • 200 E a s t s l o p e s p r i n g s 200 M e a d o w C r e e k s p r i n g 201 G o v e r n m e n t C r e e k a r e a 201 C o p p e r J a c k a r e a 201 R E F E R E N C E S C I T E D . 203 A P P E N D I X A Following p a g e 209 A P P E N D I X B F o l l o w i n g p a g e A75 ILLUSTRATIONS Following p a g e P l a t e I Geologic m a p of t h e S h e e p r o c k M o u n t a i n s a r e a . In p o c k et I I Geologic s e c t i o n of t h e S h e e p r o c k M o u n t a i ns a r e a . . . . . . . . . . . . . . . . . . . . . In p o c k et I I I Map of S h e e p r o c k M o u n t a i n s and v i c i n i t y, s h o w i n g m e a s u r e d s e c t i o n s and f o s s il l o c a t i o n s . . . In p o c k et I V Upper S h e e p r o c k s e r i e s and T a i a w ag q u a r t z i t e • 13 V Dutch P e a k t i l l i t e i n P o l e C a n y o n 17 VI Limestone c o b b l e s f r o m the D u t c h P e ak t i l l i t e 17 V I I Rounded c o b b l e s f r o m the D u t c h P e a k t i l l i t e . . . 17 V I I I Taiawag q u a r t z i t e m e m b e r of t h e M u t u a l ( ?) f o r m a t i o n • 21 I X Cambrian and O r d o v i c i a n f u c o i d s 42 X Correlation of C a m b r i a n S y s t e m in e a s t e rn N e v a d a and w e s t e r n U t a h 43 X I Correlation of C a m b r i a n S y s t e m in e a s t e rn N e v a d a , w e s t e r n U t a h , and s o u t h e a s t e rn I d a h o .'• 43 X I I Busby f o r m a t i o n 44 X I I I Specimens of p i s o l i t e s a n d p e b b l e b e d f r o m the M i l l a r d f o r m a t i o n 50 X I V Mar j u m f o r m a t i o n . 64 X V Specimens f r o m the C o l e C a n y o n and Opex f o r m a t i o n s 68 F o l l o w i ng p a g e P l a t e X V I Specimens f r o m t h e A j a x d o l o m i t e . 74 X V I I Composite d i a g r a m m a t i c c r o s s - s e c t i on of C a m b r i a n f o r m a t i o n 75 X V I I I House-Fillmore f o r m a t i o n s . . 90 X I X Swan P e a k q u a r t z i t e 103 X X Composite d i a g r a m m a t i c c r o s s - s e c t i o n of O r d o v i c i a n and S i l u r i a n f o r m a t i o n s 115 X X I Composite d i a g r a m m a t i c c r o s s - s e c t i o n of « . D e v o n i a n and M i s s i s s i p p i a n f o r m a t i o n s . . . . . . . . 141 X X I I Tertiary(?) c o n g l o m e r a t e 150 X X I I I 'White f a c i e s 1 of S h e e p r o c k g r a n i t e c o n t a i n i ng X X I V Views of L i o n H i l l a n d P o l e C a n y o n t h r u s t s - . ^ 167 X X V Pediment s u r f a c e s i n t h e v i c i n i t y of E r i c k s on P a s s . •<.....• 179 F i g u r e 1 Index m a p 1 2 Proposed s t r a t i g r a p h i c r e l a t i o n s h i p s of the P r e c a m b r i a n in w e s t - c e n t r a l Utah 20 3 Regional s t r a t i g r a p h i c r e l a t i o n s h i p s of b a s al C a m b r i a n c a r b o n a t e s 36 4 Isopach m a p of C a m b r i a n S y s t e m , e x c l u s i ve of b a s a l q u a r t z i t e s . . . . . . . . . . o . 78 F o l l o w i n g p a g e F i g u r e 5 6 T a b l e s 1 2 3 I s o p a c h m a p of M i d d l e O r d o v i c i an I n d e x m a p of m i n i n g d i s t r i c t s 183 S e d i m e n t a r y r o c k s of t h e S h e e p r o c k M o u n t a i ns S o u r c e s of i n f o r m a t i o n for C a m b r i a n S y s t em i s o p a c h m a p 78 S o u r c e s of i n f o r m a t i o n for M i d d l e O r d o v i c i an ABSTRACT T h e S h e e p r o c k R a n g e , T o o e l e and J u a b C o u n t i e s , Utah, i s c o m p o s ed chiefLy of c o n s o l i d a t e d s e d i m e n t a r y r o c k s of P r e c a m b r i a n and P a l e o z o ic a g e . S e v e r a l a r e a s of b o t h i n t r u s i v e and e x t r u s i v e r o c k s a r e p r e s e n t. U n c o n s o l i d a t e d s e d i m e n t s r e l a t e d to l a t e T e r t i a r y and Q u a t e r n a r y e p i s o d es c o v e r m u c h of t h e f l a n k s of t h e r a n g e a s p e d i m e n t g r a v e l s , lake d e p o s i t s, a n d a l l u v i u m. N e a r l y 1 1 , 0 0 0 f e e t of P r e c a m b r i a n m e t a s e d i m e n t s , l a r g e l y s l a t es a n d q u a r t z i t e s s i m i l a r to l a t e P r e c a m b r i a n f o r m a t i o n s in c e n t r a l and w e s t e r n Utah, c r o p out i n the c e n t r a l p a r t of t h e a r e a . T i l l i t e s s i m i l ar t o t h o s e found l o c a l l y in the W a s a t c h M o u n t a i n s a r e the t h i c k e s t and m o s t d i s t i n c t i v e of t h e P r e c a m b r i a n r o c k s . T w e n t y - s e v e n f o r m a t i o ns h a v i n g a c o m b i n e d t h i c k n e s s of a p p r o x i m a t e l y 2 0 , 0 0 0 f e e t r e p r e s e n t the P a l e o z o i c e r a and i n c l u d e r o c k s of a l l P a l e o z o i c p e r i o d s e x c e p t i n g ( ?) P e r m i a n . Over 80 p e r c e n t of t h e P a l e o z o i c r o c k s a r e of m a r i ne o r i g i n , the r e m a i n d e r a r e c o n t i n e n t a l - i n t e r i o r - s h e If a n d s h o r e l i ne d e p o s i t s . L i m e s t o n e , d o l o m i t e , q u a r t z i t e , and s h a l e t y p i c a l of m i o g e o s y n c l i n a i e n v i r o n m e n t c o n s t i t u t e t h e P a l e o z o i c r o c k t y p e s. E x c e p t i n g m i n o r h i a t u s e s , c o n t i n u o u s s e d i m e n t a t i o n p r e v a i l e d f r om P r e c a m b r i a n i n t o P e n n s y l v a n i a n. A l l f o r m a t i o n s w e r e s t r o n g l y f o l d e d and b r o k e n by t h r u s t f a u l ts d u r i n g the L a r a m i d e o r o g e n y . Rock u n i t s n e c e s s a r y for p r e c i se r e l a t i v e d a t i n g of L a r a m i d e and l a t e r o r o g e n i c e v e n t s a r e not p r e s e nt i i i i n the S h e e p r o c k R a n g e , but t h e r e l a t i o n s h i p s of p r e s e r v e d s t r u c t u r e s p e r m i t t h e e s t a b l i s h m e n t of a s e q u e n c e of d e f o r m a t i o n al p h a s e s a s f o l l o w s : (1) C e d a r H i l l s o r o g e n y ( ? ) - M i d - C r e t a c e o us p h a s e , (2) E a r l y L a r a m i d e o r o g e n y - M o n t a n a p h a s e , (3) M i d - L a r a m i de o r o g e n y ( ? ) - P a l e o c e n e p h a s e , (4) L a t e L a r a m i d e o r o g e n y , and (5) B a s i n and R a n g e p h a s e . S t r u c t u r e s f o r m e d d u r i n g t h e s e p h a s e s i n c l u de f o l d s , t h r u s t f a u l t s and i m b r i c a t i o n s , and n o r m a l f a u l t s , and t h e s t r u c t u r e s of e a c h s u c c e s s i v e p h a s e a r e s u p e r p o s e d upon t h o s e of e a r l i er p h a s e s . I g n e o u s a c t i v i t y which b e g a n in e a r l y T e r t i a r y and c o n t i n u e d i n t o' M i o c e n e f o r m e d g r a n i t i c and m o n z o n i t i c i n t r u s i o n s and e x t e n s i ve r h y o l i t i c and a n d e s i t i c f l o w s . A s i n g l e s m a l l a r e a of b a s a l t of u n d e t e r m i n e d a g e i s p r e s e n t. T h e r e s u l t i n g s t r u c t u r e of t h e S h e e p r o c k R a n g e i s e s s e n t i a l l y a n o r t h w a r d - d i p p i n g h o m o c l i n e m o d i f i e d by s e v e r a l f o l d s , m a j o r t h r u s t s, a n d i n t r u s i o n s. N o r m a l f a u l t i n g of t h e B a s i n and R a n g e o r o g e n i c p h a s e , c o n c o m i t a nt w i t h a n d f o l l o w i n g the i g n e o u s a c t i v i t y , a f f e c t e d b o t h T e r t i a r y and o l d er r o c k s and i s p r i m a r i l y r e s p o n s i b l e for the p r e s e n t t o p o g r a p h y and o u t l i n e of t h e S h e e p r o c k R a n g e. L a k e B o n n e v i l l e s h o r e l i n e f e a t u r e s a l o n g t h e w e s t e r n p a r t of the a r e a and a q u e s t i o n a b l e m o r a i n a l d e p o s i t at the m o u t h of N o r t h Oak B r u s h C a n y o n r e p r e s e n t P l e i s t o c e n e e v e n t s. I l l M i n e r a l d e p o s i t s f a l l i n t o two m a j o r g r o u p s : (1) d e p o s i ts a s s o c i a t e d with the West T i n t i c m o n z o n i t e c u t t i n g P r e c a m b r i a n and P a l e o z o i c r o c k s h a v e y i e l d e d m i n o r q u a n t i t i e s of c o m m e r c i a l o r es of l e a d , z i n c , s i l v e r , gold, and t u n g s t e n ; (2) d e p o s i t s a s s o c i a t ed with t h e S h e e p r o c k g r a n i t e h a v e y i e l d e d o r e s and p r o t o r e s of b e r y l l i u m , lead, s i l v e r , t u n g s t e n , t h o r i u m , and u r a n i u m , but none of t h e s e h a s a c h i e v e d c o m m e r c i a l s i g n i f i c a n c e. INTRODUCTION P u r p o s e and s c o pe T h i s i n v e s t i g a t i o n i s one of a s e r i e s of g e o l o g i c s t u d i e s in the S h e e p r o c k - W e s t T i n t i c M o u n t a i n s b e i n g c o n d u c t e d by g r a d u a t e s t u d e n ts of t h e D e p a r t m e n t of Geology of t h e U n i v e r s i t y of U t a h . The p u r p o se i s to d e c i p h e r the g e o l o g y of t h e a r e a . C o n s i d e r a b l e a t t e n t i o n h as b e e n p a i d the s t r a t i g r a p h y , i g n e o u s r o c k s , and s t r u c t u r e . Regional c o r r e l a t i o n s a r e p r o p o s e d , and t h e l o c a l s t r u c t u r e s a r e r e l a t e d to t he r e g i o n a l . A d e t a i l e d g e o l o g i c m a p i s p r e s e n t e d at t h e s c a l e of 1:31, 680 ( P l a t e I ). L o c a t i o n and a c c e s s i b i l i ty T h e r e g i o n of s t u d y i n c l u d e s t h e m a j o r p a r t of t h e S h e e p r o ck M o u n t a i n s , the A l l i s o n K n o l l s , the e a s t e r n p a r t of t h e S i m p s o n Mount a i n s , and t h e s o u t h end of t h e O n a q u i M o u n t a i n s ( F i g u r e 1 a n d P l a te I ) . T h r e e q u a r t e r s of t h e a r e a i s i n s o u t h e a s t e r n T o o e l e C o u n t y ; the r e m a i n d e r i s in n o r t h e a s t e r n J u a b C o u n t y . The a r e a c o m p r i s es a p p r o x i m a t e l y 300 s q u a r e m i l e s and i n c l u d e s a l l of T p s . 8, 9, 10, a n d U S . , R s . 6 a n d 7 W . , and t h e w e s t e r n half of R. 5 W . , Salt L a k e B a s e and M e r i d i a n. Many r o a d s , few of which a r e a l l - w e a t h e r r o a d s , s u r r o u n d the a r e a and c o n n e c t with b r a n c h wagon r o a d s which l e a d v a r i o u s d i s t a n c es up n e a r l y e v e r y m a j o r c a n y o n in t h e a r e a . Wood a n d s t o c k r o a d s link ( 1 ) I N D E X M A P S H O W I N G L O C A T I O N OF S H E E P R O C K M O U N T A I N S A R EA F I G U R E I 2 t h e m a i n a r t e r i e s and p r o v i d e r e a d y a c c e s s to m u c h of t h e i n t e r v e n i ng a r e a . The w e s t e r n p a r t of t h e a r e a i s r e a c h e d v i a c o u n t y r o a ds l e a d i n g w e s t f r o m S t a t e Highway 36 at V e r n o n and F a u s t . These c o n v e r g e to c r o s s Lookout P a s s which s e p a r a t e s t h e O n a q u i f r om t h e S h e e p r o c k M o u n t a i n s . This g r a v e l e d r o a d p r o c e e d s to S i m p s on S p r i n g s and p o i n t s w e s t , but a f ew m i l e s west of L o o k o u t P a s s a s e c o n d a r y c o u n t y r o a d l e a d s s o u t h a c r o s s the e a s t - w e s t d i v i d e known a s E r i c k s o n ' s P a s s , b e t w e e n the S h e e p r o c k and S i m p s o n M o u n t a i n si T h i s r o a d e v e n t u a l l y j o i n s a c o u n t y r o a d l e a d i n g f r o m the n o r t h w e st e d g e of t h e D e s e r t M o u n t a i n s to J e r i c h o . The s o u t h e r n p a r t of the S h e e p r o c k a r e a i s a c c e s s i b l e v i a e i t h e r the E r i c k s o n P a s s r o a d o r by a g r a v e l e d r o a d which l e a d s w e s t e r l y f r o m U. S. Highway 6 a t J e r i c ho a n d which e v e n t u a l l y j o i n s t h e E r i c k s o n P a s s r o a d b e f o r e c o n t i n u i ng w e s t w a r d to C a i l a o a n d the s t a t e l i n e . A r o a d f r o m S u g a r v i l l e , a s e t t l e m e n t a f ew m i l e s n o r t h of D e l t a , a l s o p r o v i d e s a c c e s s to the D e s e r t M o u n t a i n s and i n t e r s e c t s the J e r i c h o r o a d at i t s j u n c t i o n with t h e E r i c k s o n P a s s r o a d . The n o r t h e r n p a r t of t h e a r e a c a n be e n t e r e d by m e a n s of a s e r i e s of r o a d s f r o m V e r n o n and f r o m the F o r e s t S e r v i c e i n s t a l l a t i o n s at B e n m o r e . G e o g r a p h y T o p o g r a p h y and d r a i n a g e - The S h e e p r o c k M o u n t a i n s a r e an L - s h a p e d r a n g e and p r e s e n t a v e r y r u g g e d p r o f i l e . The b a s e of the L i s an e a s t - t o = w e s t e l e m e n t , and it i s out of h a r m o n y with the 3 g e n e r a l n o r t h - s o u t h t r e n d s which c h a r a c t e r i z e m o s t of t h e r a n g e s of t h e B a s i n and R a n g e p r o v i n c e . T h r e e of t h e h i g h e s t p e a k s in t he S h e e p r o c k R a n g e a r e in t h e C o a s t and G e o d e t i c T r i a n g u l a t i o n N e t w o r k, a n d S t a t i o n s a r e d e s i g n a t e d B e n n i o n , Dutch, and L o o k o u t P e a k s. B e n n i o n i s t h e h i g h e s t at 9, 273 f e e t above s e a l e v e l ; D u t c h a n d Lookout a r e a f ew h u n d r e d f e e t l o w e r at a b o u t 9, 000 f e e t e l e v a t i o n . Taiawag P e a k , about a q u a r t e r of a m i l e n o r t h w e s t of B e n n i o n , i s a p p r o x i m a t e ly 90 f e e t l o w e r t h a n B e n n i o n and, when v i e w e d f r o m the n o r t h , g i v e s the i m p r e s s i o n of b e i n g the h i g h e s t point in t h e r a n g e . Lookout P e a k is r e f e r r e d to a s R e d P i n e M o u n t a i n and B e n n i o n P e a k i s d e s i g n a t e d as B l a c k C r o o k P e a k by r e s i d e n t s on t h e s o u t h f l a n k of t h e R a n g e . The S h e e p r o c k d i v i d e s t a n d s b e t w e e n 2, 500 and 4, 000 f e e t a b o v e the s u r r o u n d i n g v a l l e y f l o o r , which in p l a c e s s l o p e s to t h e B o n n e v i l l e l e v e l at an e l e v a t i o n of a b o u t 5, 135 f e e t . The n o r t h and e a s t s i d e s of t h e r a n ge a r e dip s l o p e s and p r e s e n t the s t e e p e s t t o p o g r a p h y. S h a r p V - s h a p e d v a l l e y s m a r k the m a i n d r a i n a g e s in t h e m o u n t a i n s. All p e r e n n i a l s t r e a m s a r e n o u r i s h e d by s p r i n g s o r i g i n a t i n g at e l e v a t i o ns of 6 , 0 0 0 f e e t o r h i g h e r . Vernon and C h e r r y C r e e k s a r e the l a r g e st s t r e a m s and t h e i r c o u r s e s m a r k the g e o g r a p h i c b o u n d a r y b e t w e e n the s o u t h e r n p a r t of t h e S h e e p r o c k M o u n t a i n s and t h e m o r e s u b d u e d e a s t - l y i n g W e s t T i n t i c R a n g e . On the s o u t h s i d e of t h e S h e e p r o c k M o u n t a i ns Cow Hollow, P o l e , A u t s , J o e s , S h e e p r o c k , and H a r d - t o - B e a t C a n y o ns c o n t a i n s m a l l p e r e n n i a l s t r e a m s . A l b e r t E k k e r ' s ( f o r m e r l y C o t t o n w o o d ), 4 a n d South P i n e C a n y o n s a r e f a i r l y well w a t e r e d in s p r i n g and e a r ly s u m m e r , but t h e flow c e a s e s in l a t e s u m m e r . E l d e r b e r r y Canyon c o n t a i n s the m o s t p e r s i s t e n t w a t e r on t h e w e s t e r n f l a n k , w h e r e as N o r t h P i n e , N o r t h Oak B r u s h , H a r k e r s , and B e n n i o n C a n y o n s s u p p ly t h e n o r t h f l a n k with y e a r a r o u n d w a t e r . Except f o r C h e r r y and V e r n on C r e e k s , all s t r e a m s d i s a p p e a r i n t o t h e a l l u v i um and do not r e a c h the v a l l e y b o t t o m s. C l i m a t e and v e g e t a t i o n - W e a t h e r d a t a i s a v a i l a b l e f r o m two s t a t i o n s in t h e a r e a , one at B e n m o r e on t h e n o r t h f l a n k , the o t h e r at G o v e r n m e n t C r e e k ( J a m e s Ranch) on t h e west s i d e of t h e S h e e p r o ck R a n g e . A v e r a g e a n n u a l p r e c i p i t a t i o n i s a p p r o x i m a t e l y 1 3 . 5 0 i n c h es f o r t h e s e s t a t i o n s which a r e b e t w e e n 5, 250 a n d 5, 500 f e e t a b o v e s ea l e v e l . The w e t t e s t m o n t h s a r e f r o m S e p t e m b e r t h r o u g h A p r i l when p r e c i p i t a t i o n n o r m a l l y e x c e e d s one i n c h p e r m o n t h . The h i g h er p o r t i o n s r e c e i v e o v e r 30 i n c h e s ( e s t i m a t e d ) of p r e c i p i t a t i o n m a i n l y as s n ow which p e r s i s t s u n t i l l a t e May in p r o t e c t e d a r e a s on t h e n o r t h - f a c i n g s l o p e s . The s o u t h f l a n k of t h e r a n g e i s not well w a t e r e d and i t s c l i m a t e i s m i l d e r , b e i n g t e m p e r e d by f r e q u e n t s o u t h e r l y winds d u r i n g m o s t of t h e y e a r . T e m p e r a t u r e f a l l s to b e l ow z e r o o c c a s i o n a l ly d u r i n g D e c e m b e r and J a n u a r y . Hotest w e a t h e r c a n be e x p e c t e d in J u ly and A u g u s t when t e m p e r a t u r e s in e x c e s s of 100° F . h a v e b e e n r e c o r d e d. F r o s t - f r e e d a y s u s u a l l y e x t e n d f r o m May 1 t o O c t o b e r 30 in t h e v a l l ey a r e a s . 5 V e g e t a t i o n i s t h a t t y p i c a l of a m o d i f i e d d e s e r t e n v i r o n m e n t and c o n t a i n s c h a r a c t e r i s t i c s t r a t i f i c a t i o n of b o t a n i c a l a s s e m b l a g e s in z o n e s c o m m e n s u r a t e with a l t i t u d e a n d p r e c i p i t a t i o n . V a r i o u s s p e c i es of s a g e b r u s h , A r t e m i s i a , a r e the m o s t p r o m i n e n t p l a n t s of t h e v a l l ey f l o o r s and l o w e r s l o p e s . G r a s s e s and s m a l l s h r u b s a r e a b u n d a n t in t h e s a g e a r e a s , and s q u a t c a c t i b e c o m e m o r e a b u n d a n t on the l o w er s l o p e s . I n t e r g r o w i n g with s a g e on the h i g h e r s l o p e s a r e j u n i p e r s, l o c a l l y known a s c e d a r s , of s e v e r a l s p e c i e s a m o n g which J u n i p e r u s u t a h n e n s i s i s the m o s t c o m m o n . The j u n i p e r s p e r s i s t to c o n s i d e r a b le e l e v a t i o n s and d e s c e n d i n t o the v a l l e y f l o o r s a l o n g d r y w a s h e s and on p e d i m e n t s . At i n t e r m e d i a t e e l e v a t i o n s oak b r u s h r e p l a c e s the j u n i p e rs i n the m o r e p r o t e c t e d and b e t t e r w a t e r e d z o n e s . Mahogany, C e r c o c a r p u s l e d i f o l i u s , though r e l a t i v e l y s p a r s e t h i n s at h i g h e l e v a t i o n s p r i n c i p a l l y on s o u t h - f a c i n g s l o p e s w h e r e p r e c i p i t a t i o n i s low. P i n o n and y e l l o w p i n e s a r e p r e s e n t p r i n c i p a l l y on t h e n o r t h s l o p es of t h e h i g h e s t e l e v a t i o n s . Aspen, P o p u l u s t r e m u l o i d e s , and c h o k e - c h e r r y , P r u n u s v i r g i n i a n a , a r e p r e s e n t n e a r high a l t i t u d e s p r i n g s and a l o n g w a t e r c o u r s e s at i n t e r m e d i a t e e l e v a t i o n s . C o t t o n w o o d s and oak b r u s h a r e p r e s e n t in a f ew l o c a l i t i e s w h e r e an a b u n d a n c e of w a t e r p e r s i s t s and a r e u s u a l l y found n e a r the j u n c t i o n of m o u n t a in s l o p e s with the d e s e r t f l o o r. 6 P r e v i o u s g e o l o g i c i n v e s t i g a t i o n s - In 1 8 5 8 - 5 9 C a p t a i n J . H. S i m p s o n of t h e C o r p s of T o p o g r a p h i c a l E n g i n e e r s h e a d e d an e x p e d i t i o n c o m m i s s i o n e d to s u r v e y a wagon r o a d f r o m C a m p F l o yd i n R u s h V a l l e y n e a r the p r e s e n t town of S t o c k t o n , Utah, to C a l i f o r n i a . Henry E n g l e m a n n , e x p e d i t i o n g e o l o g i s t , e x c e p t f o r a b r i e f d e s c r i p t i o n of e x t r u s i v e r o c k s at S i m p s o n ' s S p r i n g s , c i t es n o t h i n g p e r t a i n i n g to t h e r o c k s of t h e S h e e p r o c k - O n a q u i a r e a . On S i m p s o n ' s m a p of Wagon R o u t e in U t a h T e r r i t o r y , the S t a n s b u r y, O n a q u i , and S h e e p r o c k R a n g e s w e r e not d i f f e r e n t i a t e d , and t h e t h r ee a r e c o l l e c t i v e , i n c l u d e d a s G u y o t ' s R a n g e. G i l b e r t (1890) in h i s s t u d y of t h e s h o r e l i n e f e a t u r e s of P l e i s t o c e n e, L a k e B o n n e v i l l e , d e s c r i b e s s h o r e l i n e s and a r i v e r c h a n n e l w e s t of the S i m p s o n M o u n t a i n s and a l o n g the D e s e r t M o u n t a i n s. L o u g h l i n (1920) in P r o f e s s i o n a l P a p e r 111, O r e D e p o s i t s of Utah, v e r y g e n e r a l l y d i s c u s s e s t h e g e o l o g y of t h e S h e e p r o c k M o u n t a i n s , and c o n t r i b u t i o n s by H e i k e s s p e c i f i c a l l y d e a l with t h e S h e e p r o c k , S i m p s o n, and D e s e r t M o u n t a i n s . Although the o r e d e p o s i t s a r e e m p h a s i z e d, s o m e g e n e r a l s t r a t i g r a p h i c and s t r u c t u r a l r e l a t i o n s in t h e r a n g es a r e i n c l u d e d. E a r d i e y and H a t c h (1940) i n t h e i r d i s c u s s i o n of t h e P r o t e r o z o ic r o c k s in Utah m e a s u r e d a s e c t i o n of P r e c a m b r i a n m e t a s e d i m e n t s in t h e S h e e p r o c k M o u n t a i n s a n d r e l a t e the s t r u c t u r a l f e a t u r e s of the r a n g e to t h e r e g i o n a l p a t t e r n. P a r t of t h e West T i e t i c m i n i n g d i s t r i c t was m a p p e d by S t r i n g h am (1940), who w a s c o n c e r n e d p r i m a r i l y with the m i n e r a l i z a t i o n in the v i c i n i t y of t h e Old S c o t i a m i n e . W e s t o n G a r d n e r (1954) r e m a p p e d t h e a r e a p r e v i o u s l y s t u d i e d by S t r i n g h a m and e x t e n d e d the m a p p i n g to i n c l u d e the S h e e p r o e k - W e st T i n t i c j u n c t i o n . G a r d n e r d e a l s with s t r u c t u r e and s t r a t i g r a p h y of a s m a l l a r e a e R o b e r t H i l l i e r (1956) r e p o r t e d on t h e u r a n i u m o c c u r r e n c e in the South Oak B r u s h a r e a on t h e s o u t h w e s t e r n flank of the S h e e p r o ck M o u n t a i n s . F i e l d work F i e l d w o r k upon which t h e p r e s e n t r e p o r t i s b a s e d was b e g u n in May 1953 while the w r i t e r was a s s i s t i n g i n a d i a m o n d d r i l l p r o g r am b e i n g c o n d u c t e d by t h e B r u s h B e r y l l i u m C o m p a n y . Work was c o n t i n u ed i n t e r m i t t e n t l y d u r i n g 1954, 1955, and 1956, and c o m p l e t e d , to the e x t e n t s e t f o r t h in t h i s r e p o r t , , in N o v e m b e r 1956. Mapping was done on U. S. F o r e s t S e r v i c e a e r i a l p h o t o g r a p h s at a s c a l e of 1:20, 000; a n d F a i r c h i i d a e r i a l p h o t o g r a p h s of a s c a l e of a p p r o x i m a t e l y 1:62, 500. E x c e p t f o r the e x t r e m e n o r t h e r n and s o u t h e r n p a r t s , the m a p was c o m p i l e d f r o m a F o r e s t S e r v i c e p l a n e m e t r i c b a s e and a e r i a l p h o t o g r a p h s . T h e g e o l o g i c m a p ( P l a t e I) i s at a s c a l e of 1:31, 680 h a v i n g b e en p l o t t e d on a n d r e d u c e d f r o m a b a s e m a p of a s c a l e of 1:21, 1 2 0 . The 8 m a p s h o w i n g p o s i t i o n s of s t r a t i g r a p h i c s e c t i o n s and f o s s i l l o c a l i t i es ( P l a t e III) i s at a s c a l e of 1:42, 240 h a v i n g b e e n r e d u c e d f r o m the 1:21, 120 b a s e m a p . On t h i s m a p the p o s i t i o n s of t h e s t r a t i g r a p h ic s e c t i o n s r e f e r r e d to i n t h e t e x t a r e p l o t t e d a n d a d d i t i o n a l s e c t i o ns a r e n o t e d . Ail m e a s u r e d s e c t i o n s , both t h o s e r e f e r r e d to i n the t e x t and the a d d i t i o n a l s e c t i o n s , a r e r e p o r t e d in A p p e n d i x A and shown on t h e m a p . F o s s i l l o c a l i t i e s of A p p e n d i x B s i m i l a r l y a re r e c o r d e d on the m a p . 9 ACKNOWLEDGEMENTS V a l u a b l e a s s i s t a n c e h a s b e e n r e c e i v e d f r o m m a n y p e o p l e d u r i ng t h i s s t u d y . I a m p a r t i c u l a r l y i n d e b t e d to D r . N o r m a n C. W i l l i a m s of t h e U n i v e r s i t y of U t a h f o r h i s i n t e r e s t and s u g g e s t i o n s ; to Dean A. J. E a r d l e y , P r o f e s s o r s W. L. S t o k e s , F . W. C h r i s t i a n s e n , B. S t r i n g h a m, a n d Max P . E r i c k s o n f o r s u g g e s t i o n s and c r i t i c a l r e a d i n g of the m a n u s c r i p t . The p r e p a r a t i o n of t h i s r e p o r t was i n f l u e n c e d by d i s c u s s i o n s with Max D. C r i t t e n d e n and H. T. M o r r i s of t h e U. S. G e o l o g i c a l S u r v e y , G r a n t S t e e l e and Dwight A r n o l d of the Gulf Oil C o r p o r a t i o n , R. H. O l s o n and R. C. B r i g h t , c o l l e a g u e s at the U n i v e r s i t y of U t a h , and B„ J . S h a r p and A. E. G r a n g e r of t h e U. S. A t o m i c E n e r g y C o m m i s s i o n. E s p e c i a l t h a n k s i s due to t h e l a t e M. A. S t a i n b r o o k , C h r i s t i na L o c h m a n B a l k , A. R. P a l m e r , W a l t e r S a d l i c k , C h e s t e r A r n o l d, and R. R, B r o w n f o r a i d in i d e n t i f y i n g f o s s i l s. M r . R. C. B r i g h t r e n d e r e d i n v a l u a b l e a s s i s t a n c e in i d e n t i f y i ng t h e C a m b r i a n and O r d o v i c i a n f a u n a s. T h e w r i t e r i s i n d e b t e d to W i l l i am S a l i s b u r y f o r a s s i s t a n c e and s u g g e s t i o n s in the p r e p a r a t i o n of t h e i l l u s t r a t i o n s. E s p e c i a l t h a n k s a r e due m y wife, G e n e v r a , for h e r p a t i e n c e and u n d e r s t a n d i n g , and f o r t y p i n g at a l l s t a g e s of t h i s w o r k. 10 STRATIGRAPHY G e n e r a l s t a t e m e nt S e d i m e n t a r y f o r m a t i o n s e x p o s e d in t h e S h e e p r o c k M o u n t a i n s h a ve a t o t a l t h i c k n e s s of a p p r o x i m a t e l y 3 1 , 0 0 0 f e e t . B e s i d e s P r e c a m b r i an r o c k s s t r a t a of t h e C a m b r i a n , O r d o v i c i a n , S i l u r i a n , D e v o n i a n , M i s s i s s i p - p l a n , P e n n s y i v a n i a n , C r e t a c e o u s ( ? ) , T e r t i a r y , and Q u a t e r n a r y p e r i o ds a r e p r e s e n t. T h e P r e c a m b r i a n s y s t e m i s r e p r e s e n t e d by a p p r o x i m a t e l y 1 1 , 0 00 f e e t of l o w - g r a d e m e t a m o r p h o s e d s e d i m e n t s p r i n c i p a l i t y of c o n t i n e n t al o r i g i n . O v e r 80 p e r c e n t of t h e P a l e o z o i c r o c k s a r e of m a r i n e o r i g in and t h e r e m a i n d e r a r e c o n t i n e n t a l , i n t e r i o r shelf, o r s h o r e l i ne d e p o s i t s . C o n t i n u o u s s e d i m e n t a t i o n s e e m s to h a v e p r e v a i l e d f r om P r e c a m b r i a n t h r o u g h n e a r l y t h e e n t i r e s e c t i o n of P a l e o z o i c r o c ks e x p o s e d within the a r e a. The s u c c e e d i n g d i s c u s s i o n and A p p e n d i x A p r e s e n t in d e t a i l the f o r m a t i o n s l i s t e d in T a b l e 1. P l a t e III s h o w s l o c a t i o n of s t r a t i g r a p h ic s e c t i o n s t o g e t h e r with l o c a l i t i e s w h e r e f o s s i l s w e r e c o l l e c t e d . In A p p e n d i x B t h e m a t e r i a l f r o m t h e s e f o s s i l l o c a l i t i e s i s c l a s s i f i e d. TABLE 1 - SEDIMENTARY ROCKS OF THE SHEEPROCK MOUNTAINS AREA System Series Formation Thfiecektn ess Quaternary and Tertiary. Tertiary(?) or Cretaceous(?) - Permian and Pennsylvania!!- Mississippian Devonian Silurian Ordovician Cambrian- Precambrian- Recent to Pliocene? Unconformity Pliocene? • Unconformity Unconformity Chester Meramec Osage-Kinderhook- Unconformity Upper Devonian Middle Devonian ? Unconformity Niagran Upper Middle Lower Upper Middle Lower ? Unconformity? Post Beltian Unconformity Post Beltian? - Gravel and clay Gravel and conglomerate Conglomerate and red beds Oquirrh formation Upper mbr. Great Blue fm. Chiulos mbr. - Lower mbr. Deseret-Humbug formations - Madison limestone Total, Mississippian Victoria-Pinon Peak fms.-"--- Sim on son dolomite i Sevy dolomite Total, Devonian Laketown dolomite Total, Silurian i Fish Haven dolomite Swan Peak qtzt. (restricted) Kanosh shale Pogonip Juab limestone Group Wah Wah Is. House-Fillmore Is - Total, Ordovician - Ajax dolomite Opex formation- Cole Canyon formation Marjum formation Wheeler formation Swasey limestone-' Condor fm. Dome limestone Ophii Burnt Canyon fm. - Group Millard formation - Busby formation Pioche shale Tintic quartzite Total, Cambrian - Total, Paleozoic Mutual(?) formation Sheeprock series Total, Precambrian +150 +200 Limited exposure (not measured) 1400 1818 911 1142 - 1165 399 5664+ 570+ - 775 450 - 563 356 -1044 1851 + 810 - 1001 905+ 701 • - 706 348 • - 465 206 • - 250 161 • - 204 456 • - 475 1088 - 1111 3086± 1016 938 899 1171 405 • - 430 131 • - 169 106 • - 135 37 - 81 178 • - 221 246 • - 355 65 • - 167 293 • - 342 2572 924 8269± 19775± 10000+ 10924+ PRECAMBRIAN ROCKS G e n e r a l s t a t e m e nt Rock s t r a t a a s s i g n e d to t h e P r e c a m b r i a n s y s t e m a g g r e g a te about 1 1 , 000 f e e t in t h i c k n e s s and a r e d i v i s i b l e i n t o two m a j or s e q u e n c e s . The u p p e r s e q u e n c e i s c o m p o s e d of a r g i l l i t e s , q u a r t z i t es and c o n g l o m e r a t e s and i s c o r r e l a t e d with t h e M u t u a l f o r m a t i o n . The l o w e r s e q u e n c e i s d i v i s i b l e i n t o t h r e e u n i t s b a s e d upon l i t h o l o g ic f e a t u r e s and s t r a t i g r a p h i c p o s i t i o n . The o l d e s t u n i t i s p r i n c i p a l ly b l a c k s l a t e a n d t a n q u a r t z i t e ; the m i d d l e unit i s a d i s t i n c t i v e t i l l i t e; and the u p p e r u n i t i s m a i n l y g r e e n and t a n s l a t e s with s u b o r d i n a te q u a r t z i t e s . P r e c a m b r i a n r o c k s , i n c l u d i n g the t i l l i t e , w e r e r e c o g n i z e d in t h e D e s e r t M o u n t a i n s and in t h e S i m p s o n M o u n t a i n s . The S i m p s on M o u n t a i n s e c t i o n i s one of t h e m o s t c o m p l e t e P r e c a m b r i a n s e c t i o ns of the r e g i o n . The P r e c a m b r i a n r o c k s of the S i m p s o n M o u n t a i n s, h o w e v e r , w e r e not t h o r o u g h l y i n v e s t i g a t e d and c a n only t e n t a t i v e ly be c o r r e l a t e d with t h o s e of t h e S h e e p r o c k R a n g e. S h e e p r o c k s e r i e s (new n a m e) G e n e r a l s t a t e m e n t - A 9, 000= to 10, 0 0 0 - f o o t s e q u e n c e of m e t a - s e d i m e n t s c o m p o s e d of s l a t e , t i l l i t e , p h y l l i t e , q u a r t z i t e , and c o n g l o m e r a t e c o n s t i t u t e s t h e o l d e s t r o c k s e x p o s e d in t h e S h e e p r o ck M o u n t a i n s . Owing to t h e d i f f i c u l t y and u n c e r t a i n t y of c o r r e l a t i ng t h i s s e q u e n c e with n a m e d f o r m a t i o n s in o t h e r a r e a s , the t e rm 12 " S h e e p r o c k s e r i e s " i s p r o p o s e d f o r i t . The S h e e p r o c k s e r i e s c a n , in s e v e r a l p l a c e s , be f u r t h e r s u b d i v i d e d i n t o t h r e e c o m p o n e n t u n i t s - - t h e l o w e r S h e e p r o c k s e r i e s , the D u t c h P e a k t i l l i t e , and t h e u p p er S h e e p r o c k s e r i e s. D i s t r i b u t i o n and t h i c k n e s s = The S h e e p r o c k s e r i e s c o m p r i s es a l l of t h e s t r a t a s o u t h of t h e c r e s t of the r a n g e f r o m the d i v i d e to the d e s e r t f l o o r . The only e x c e p t i o n s a r e the West T i n t i c and South Oak B r u s h a r e a s , at which l o c a l i t i e s P a l e o z o i c r o c k s c r o p o u t . The S i m p s o n M o u n t a i n s s o u t h of t h e v i c i n i t y of B l a c k ' s R a n c h a r e a l so c o m p o s e d l a r g e l y of t h e S h e e p r o c k s e r i e s . North of t h e S h e e p r o c k d i v i de f r om L i t t l e V a l l e y to t h e d e s e r t f l o o r n e a r t h e m o u t h of H a r k e r Canyon t h e s t r a t a a r e e n t i r e l y of t h e S h e e p r o c k s e r i e s . To t h e w e s t , the r o c k s of the S h e e p r o c k s e r i e s e x t e n d s o u t h of a l i n e f r o m the m o u th of H a r k e r C a n y o n to B e n n i o n P e a k . The i s o l a t e d k n o l l s p r o t r u d i ng t h r o u g h t h e d e s e r t f l o o r s o u t h of t h e S h e e p r o c k R a n g e a r e l i k e w i se s t r a t a of. t h e S h e e p r o c k s e r i e s. The S h e e p r o c k s e r i e s i s a p p r o x i m a t e l y 9, 800 f e e t t h i c k in the A u t s - P o l e ° C o w H o l l ow a r e a . At no p l a c e in the S h e e p r o c k a r e a is t h e b a s e of t h e s e r i e s e x p o s e d. T o p o g r a p h i c e x p r e s s i o n - The s e v e r a l l i t h o i o g i e s of t h e S h e e p r o ck s e r i e s g i v e it a v a r i e t y of t o p o g r a p h i c e x p r e s s i o n s o v e r i t s l a r g e a r ea of o u t c r o p . The m o r e m e t a m o r p h o s e d s l a t e s and a r g i i l i t e s c l o s e to 13 t h e i n t r u s i o n s w e a t h e r to f o r m s t e e p s l o p e s w h e r e a s in a r e a s of l e s s i n t e n s e m e t a m o r p h i s m the s a m e r o c k s f o r m g e n t l e s l o p e s. Q u a r t z i t e s f o r m c l i f f s and s t e e p s l o p e s a s do t h e c o n g l o m e r a t e s and m o r e s a n d y f a c i e s of t h e t i l l i t e ( P l a t e IV). L i t h o i o g y - The S h e e p r o c k s e r i e s i s c o m p o s e d of m a n y r o c k type a l l of which a r e v a r i e t i e s of m e t a s e d i m e n t s . Rocks c l o s e to the S h e e p r o c k g r a n i t e a r e t h e m o s t s e v e r e l y m e t a m o r p h o s e d. T h e o l d e s t e x p o s e d s t r a t a of t h e l o w e r s e r i e s a r e d e s i g n a t e d for m a p p i n g p u r p o s e s a s the ' b l a c k - b a n d e d p h y l l i t e 1 . Only one m e a s u r ed s e c t i o n ( A p p e n d i x A, S e c t i o n P C - 6 ) in the A u t s C a n y o n a r e a , i n c l u d es t h e p h y l l i t e . Units 24 t h r o u g h 30 r e p r e s e n t the p h y l l i t e u n i t and m e a s u r e 2 , 6 9 0 f e e t t h i c k . The b a s e of t h e p h y l l i t e i s c o v e r e d and b e l i e v e d to b e i n t r u d e d by t h e S h e e p r o c k g r a n i t e . Other e x p o s u r es of the p h y l l i t e a r e on t h e s o u t h f l a n k of Dutch P e a k and i n t h e h e a ds of J o e s a n d B e n n i o n C a n y o n s . The r o c k s a r e t h i n l y b a n d e d to v a r v e d, f i n e - g r a i n e d , b l a c k to s i l v e r - b l a c k , and i n m o s t l o c a l i t i e s h a v e b e en a l t e r e d b e c a u s e of t h e i r p r o x i m i t y to t h e S h e e p r o c k g r a n i t e. C o n f o r m a b l y o v e r l y i n g the ' b l a c k - b a n d e d p h y l l i t e ' i s a s e r i es of q u a r t z i t e s , c o n g l o m e r a t e s , and a f ew s l a t e s . This u n i t r a n g es b e t w e e n 1, 350 and 1, 470 f e e t in t h i c k n e s s . The q u a r t z i t e s a r e the d o m i n a n t r o c k type and a r e c h a r a c t e r i s t i c a l l y tan with a v e r y light g r e e n t i n t . Near the top of t h e s e q u e n c e i s a d a r k g r e e n d i a b a s ic Upper slates and quartzites of the Sheeprock series with overlying Taiawag quartzite member of the Mutual (?) formation showing repetition by faulting. 14 t e x t u r e d u n i t which r a n g e s f r o m 20 to 60 f e e t in t h i c k n e s s . It s e r v e s a s an e x c e l l e n t m a r k e r bed f o r d e t e r m i n i n g t h e p r o x i m i ty of the top of the u n i t . Above the d i a b a s i c t e x t u r e d r o c k i s a 4 0 - f o ot t h i c k u n i t of t h i n - b e d d e d , flaggy b l a c k q u a r t z i t e c o n t a i n i n g f ew s t r e a ks of d a r k g r e e n a r g i l l i t e . O v e r l y i n g the b l a c k q u a r t z i t e I s a 2 0 - to 4 0 - foot u n i t of g r a y - t a n to b l u e - g r a y t i n t e d q u a r t z i t e which c o n f o r m a b ly u n d e r l i e s the Dutch P e a k t i l l i t e . The g r a y q u a r t z i t e , b l a c k s l a ty q u a r t z i t e , and d i a b a s i c t e x t u r e d u n i t s c a n be t r a c e d t h r o u g h o u t the a r e a w h e r e the b a s e of t h e t i l l i t e i s e x p o s e d. The n e x t h i g h e r unit in the S h e e p r o c k s e r i e s i s a t i l l i t e m e m b er which r a n g e s f r o m a t h i n edge to o v e r 4 , 0 0 0 f e e t in t h i c k n e s s . This u n i t i s of s p e c i a l s i g n i f i c a n c e and a m o r e c o m p l e t e d i s c u s s i o n f o l l o ws u n d e r a s e p a r a t e h e a d i n g ; and t h e t e r m " D u t c h P e a k " t i l l i t e m e m b er i s p r o p o s e d. C o n f o r m a b l y o v e r l y i n g the t i l l i t e with g r a d a t i o n a l c o n t a c t i s the u p p e r S h e e p r o c k s e r i e s . The g r a d a t i o n a l and l e n s i n g c h a r a c t e r of t h e u p p e r s e r i e s and a t t e n d a n t l i t h o f a c i e s c h a n g e s m a k e the a c c u r a cy of m e a s u r e m e n t s of t h i s s e q u e n c e v e r y d o u b t f u l . Between 2, 000 and 3, 000 f e e t of s t r a t a w e r e m e a s u r e d or e s t i m a t e d to c o m p o s e t h e u n i t. The u p p e r S h e e p r o c k s e r i e s i s c o m p o s e d m a i n l y of t a n and light g r e e n s h a l e . In t h e e a s t e r n m o s t e x p o s u r e of the s t r a t a in Cow H o l l ow a l a r g e u n i t of white q u a r t z i t e l i e s at t h e top of the s e q u e n c e , but 15 t h i s i s the only l a r g e e x p o s u r e of q u a r t z i t e in t h i s s e r i e s . At T a i a w a g P e a k in t h e w e s t e r n p a r t of the r a n g e the S h e e p r o c k s e r i es c o m p r i s e s d r a b s h a l e and q u a r t z i t e in t h e u p p e r z o n e . T h e r e a re no t i i l i t e s on T a i a w a g P e a k ( A p p e n d i x A, S e c t i o n P C - 2 ). F i e l d i d e n t i f i c a t i o n - The S h e e p r o c k s e r i e s I n c l u d e s t h e m o st a l t e r e d and m e t a m o r p h o s e d s t r a t a In t h e S h e e p r o c k a r e a . Some f i s s i l e r o c k s In t h e u p p e r S h e e p r o c k s e r i e s a r e but s l i g h t l y m e t a m o r p h o s e d and m a y p a s s e a s i l y f o r u n c t i o u s ( g r e a s y ) , t h i n - b e d d ed s h a l e . The c l e a v a g e c u t s t h e b e d d i n g at a low a n g l e . Some of the q u a r t z i t e s a r e v e r y s i m i l a r to t h e T i n t i c q u a r t z i t e . Other t h a n q u a r t z i t es a l l o t h e r s e d i m e n t a r y r o c k s a r e e a s i l y r e c o g n i z e d f r o m y o u n g e r r o c ks b e c a u s e of t h e i r g r e a t e r I n d u r a t i o n . A f ew of t h e l o w e r m o s t c o n g l o m e r a t e s a r e c h a r a c t e r i z e d by s t r e t c h e d p e b b l e s. D u t c h P e a k t i l l i t e ( n ew n a m e) N e e d of n e w n a m e - The n a m e Dutch P e a k t i l l i t e m e m b e r i s p r o p o s e d f o r the t i l l i t e u n i t in t h e S h e e p r o c k s e r i e s . It i s p r o b a b l e that t h e D u t c h P e a k t i l l i t e i s in p a r t e q u i v a l e n t in a g e to t h e M i n e r a l F o rk t i l l i t e of t h e W a s a t c h M o u n t a i n s . The n a m e M i n e r a l F o r k t i l l i t e was not u s e d f o r d e s i g n a t i n g U t h o l o g i c a i l y s i m i l a r s t r a t a in t h e S h e e p r o c k M o u n t a i n s f o r the f o l l o w i n g r e a s o n s" 1. The M i n e r a l F o r k t i l l i t e l i e s u n c o n f o r m a b l y on r o c k s of t h e Big C o t t o n w o o d s e r i e s o r the o l d e r F a r m i n g t on 16 C o m p l e x . In t h e S h e e p r o c k M o u n t a i n s no b a s a l t i l l i te u n c o n f o r m i t y 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. 2 . The M i n e r a l F o r k t i l l i t e i s u n c o n f o r m a b l y o v e r l a i n by t h e M u t u a l f o r m a t i o n in t h e C o t t o n w o o d a r e a . In the S h e e p r o c k a r e a r o c k s a s s i g n e d to t h e M u t u a l ( ? ) f o r m a t i o n o v e r l i e with q u e s t i o n a b l e u n c o n f o r m i t y s h a l es a n d m e t a s e d i m e n t s of t h e u p p e r S h e e p r o c k s e r i e s . The c o n t a c t b e t w e e n t h e t i l l i t e and t h e c o n f o r m a b l y o v e r l y i ng S h e e p r o c k s e r i e s i s g r a d a t i o n a l. 3 . In one d i r e c t i o n the t i l l i t e of t h e S h e e p r o c k a r e a g r a d es l a t e r a l l y i n t o s h a l e s and q u a r t z i t e s of t h e S h e e p r o ck s e r i e s . 4 . S i m i l a r i t y b e t w e e n the M i n e r a l F o r k t i l l i t e and t h e t i l l i te of t h e S h e e p r o c k M o u n t a i n s and v i c i n i t y i s only l i t h o l o g ic w h e r e a s u p p e r and l o w e r c o n t a c t s of t h e two t i l l i t e s a re d i s t i n c t l y d i f f e r e n t. 5 . The t i l l i t e of the S h e e p r o c k a r e a p o s s i b l y i s m o r e r e p r e s e n t a t i v e of d e p o s i t i o n f a r t h e r f r o m g l a c i a l c e n t e r s w h e r e a s the W a s a t c h and A n t e l o p e I s l a n d d e p o s i t s m a y r e p r e s e n t a r e as of a c t i v e a b r a s i o n by a c o n t i n e n t a l i c e s h e e t. D i s t r i b u t i o n and t h i c k n e s s - The D u t c h P e a k t i l l i t e c r o p s out f r o m the h e a d of South Oak B r u s h Canyon a l o n g t h e c r e s t of t h e r a n ge 17 to Dutch P e a k w h e r e It l e a v e s t h e d i v i d e and f o r m s a dip s l o p e along t h e n o r t h - f a c i n g s l o p e s to L i t t l e V a l l e y C r e e k . The t i l l i t e i s a b s e nt in South Oak B r u s h Canyon but a t t a i n s a t h i c k n e s s of 4, 044 f e e t on the n o r t h s l o p e of D u t c h P e a k . In P o l e C a n y o n t h e o v e r t u r n e d t i l l i te o c c u p i e s b o t h s i d e s of t h e c a n y o n , e x t e n d i n g f r o m a r e v e r s e fault n e a r the c r e s t of t h e r a n g e , to t h e f o o t h i l l s on t h e s o u t h . T i l l i t e is p r e s e n t n o r t h of t h e p r i n c i p a l m i n i n g a r e a in the W e s t T i n t i c m i n i ng d i s t r i c t . S m a l l e r e x p o s u r e s of t i l l i t e s a r e in the D e s e r t M o u n t a i ns and in the A l l i s o n ' s K n o l l s . An i s o l a t e d e x p o s u r e i s at C o y o t e S p r i n gs on the s o u t h s l o p e s of t h e S i m p s o n M o u n t a i n s. T h e t i l l i t e t h i c k e n s e a s t w a r d f r o m B e n n i o n P e a k . The s e c t i on m e a s u r e d on t h e n o r t h s l o p e of D u t c h P e a k a g g r e g a t e s a t o t a l of 4, 044 f e e t of s t r a t a . In P o l e C a n y o n , 2, 555 f e e t of t i l l i t e was m e a s u r e d in t h e o v e r t u r n e d P r e c a m b r i a n s e c t i o n. T o p o g r a p h i c e x p r e s s i o n - The Dutch P e a k t i l l i t e w e a t h e r s to f o r m s l o p e s . Gently d i p p i n g s t r a t a a r e l o c a l l y s t r e w n with t h e r e s i s t a nt b o u l d e r s c o m m o n in t h e t i l l i t e. L i t h o i o g y = The t i l l i t e i s a d a r k g r e e n c o n g l o m e r a t i c r o c k h a v i ng a s l a t e o r q u a r t z i t e m a t r i x . Unlike a c o n g l o m e r a t e , the b o u l d e r s, c o b b l e s , and p e b b l e s a r e widely d i s p e r s e d in a s l a t y m a t r i x ( P l a t e V). The l a r g e r f r a g m e n t s of t h e t i l l i t e a r e s u b a n g u l a r and s u b r o u n d ed with c o b b l e and p e b b l e s i z e s p r e d o m i n a t i n g ( P l a t e s VI a n d V I I ). Q u a r t z i t e f r a g m e n t s p r e d o m i n a t e but s c h i s t , s l a t e , l i m e s t o n e, Figure 2 Cobble of limestone from the Dutch Peak tillite, from the west side of Pole Canyon showing fractures filled with a chloritic matrix. Cobbles from the Dutch Peak tillite, composed of igneous rock, quartzite and schist. Rounding indicates fluvial or partially fluvial origin. Matrix material at lower right. 18 p e g m a t i t i c q u a r t z , and I g n e o u s p a r t i c l e s a r e a l s o r e p r e s e n t e d in the c o a r s e r m a t e r i a l . The l a r g e r b o u l d e r s a r e g e n e r a l l y m o r e a n g u l ar t h a n t h e c o b b l e s . Included in t h e t i l l i t e a r e a f ew l e n s e s of well r o u n d e d c o b b l e s and in p l a c e s s o m e r e l a t i v e l y p u r e l e n s e s of q u a r t z i t e . The q u a r t z i t e s a r e light g r a y to i v o r y c o l o r e d but s o me h a v e a p u r p l e c a s t . Bedding within t h e t i l l i t e I s v e r y p o o r l y shown, a l t h o u g h in s e v e r a l p l a c e s c r o s s ° b e d d i n g I s p r e s e n t. T h e t y p i c a l t i l l i t e p o s s e s s e s a c l e a v a g e which c a u s e s t h e r o c k to w e a t h e r a s i r r e g u l a r s l a b s . This f r a c t u r e i s well m a r k e d a n d in p l a c es m a y be m i s t a k e n f o r b e d d i n g . The t i l l i t e w e a t h e r s greenish«=brown t o b r o w n . C a r b o n a t e e l a s t i c s u s u a l l y w e a t h e r out l e a v i n g h o l e s which m a y be c o a t e d with an u n i d e n t i f i e d r a d i a t i n g , f i b r o u s m i n e r a l, e s p e c i a l l y n e a r the i n t r u s i o n. T h e l a r g e s t b o u l d e r o b s e r v e d in t h e t i l l i t e m e a s u r e d G^b^xAK I t w a s t e n t a t i v e l y i d e n t i f i e d a s a q u a r t z m o n z o n i t e . A p r o s p e c t o r in t h e West T i n t i c a r e a m i n e d s u c h a b o u l d e r t h i n k i n g it was an i n t r u s i o n. L a r g e b l o c k s of l i m e s t o n e a r e a l s o p r e s e n t in t h e t i l l i t e , and, the l a r g e s t n o t e d was l e s s t h a n t h r e e f e e t a c r o s s . Q u a r t z i t e b o u l d e rs s e l d o m e x c e e d two f e e t in d i a m e t e r . Typical in t h e m o r e b o u i d e ry f a c i e s a r e b o u l d e r s of b r i g h t g r e e n q u a r t z i t e . The c o l o r a t i o n of the q u a r t z i t e s i s p r o b a b l y c a u s e d by m i n u t e g r a n u l e s of c h r o m e m i ca ( f u c h i t e ) d i s p e r s e d In t h e i n t e r s t i c e s. 19 N e a r the t o p of t h e t i l l i t e the m a t r i x b e c o m e s m o r e s a n d y and q u a r t z i t i c and c o n t a i n s a f ew s h a l e and s a n d y l e n s e s . West of t he D u t c h P e a k s e c t i o n t h e t i l l i t e i s m o r e s a n d y and c o n g l o m e r a t i c. It i n t e r t o n g u e s with d a r k s l a t e s and q u a r t z i t e s of t h e S h e e p r o ck s e r i e s . As the u n i t p i n c h e s o u t f i t b e c o m e s m o r e q u a r t z i t i c and g r a d u a l l y c h a n g e s to a b r o w n i s h - p u r p l e c o n g l o m e r a t i c q u a r t z i t e. The u p p e r and l o w e r c o n t a c t s of t h e t i l l i t e a r e c o n f o r m a b l e with a d j a c e n t r o c k s. F i e l d i d e n t i f i c a t i o n - The t i l l i t e i s t h e m o s t d i s t i n c t i v e of a l l t h e P r e c a m b r i a n r o c k s in t h e S h e e p r o c k a r e a . The d a r k b r o w n i s h - g r e e n c o l o r i s p a r t i c u l a r l y d i s t i n c t i v e . The s p o t t e d g r a v e l l y a n d c o b b ly b e d s e x h i b i t i n g p r o m i n e n t c l e a v a g e and f l a g g y w e a t h e r i n g c h a r a c t e r i s t i c s a r e a l s o a i d s in r e c o g n i t i o n . L i m e s t o n e s and b r i g h t g r e en ! q u a r t z i t e c o b b l e s and b o u l d e r s of P r e c a m b r i a n age a r e found only in t h e t i l l i t e. C o r r e l a t i o n - The m o s t o b v i o u s c o r r e l a t i o n of P r e c a m b r i an u n i t s i s t h a t of t h e D u t c h P e a k t i l l i t e of t h e S h e e p r o c k R a n g e and the M i n e r a l F o r k t i l l i t e of t h e W a s a t c h R a n g e ( E a r d l e y and H a t c h , 1940, p.827). The u n u s u a l l i t h o i o g y i s not l i k e l y to b e r e p e a t e d a n d a m i n o r u n u s u a l c h a r a c t e r s u c h a s the c o n c e n t r i c l a m i n a e in the l i m e s t o n e b o u l d e r s o c c u r s in t h e t i l l i t e of b o t h l o c a l i t i e s. As to t h e l o w e r and u p p e r S h e e p r o c k s e r i e s , the f o l l o w i n g r e l a t i o ns s e e m s i g n i f i c a n t . In the S h e e p r o c k R a n g e the t i l l i t e r e s t s on t h e l o w er 20 S h e e p r o c k s e r i e s a p p a r e n t l y c o n f o r m a b l y . On A n t e l o p e I s l a n d the t i l l i t e o c c u p i e s d e p r e s s i o n s i n t h e F a r m i n g t o n C a n y o n c o m p l ex ( W i l l a r d L a r s o n , p e r s o n a l c o m m u n i c a t i o n ) . It a l s o r e s t s on t h e old c o m p l e x in the C i t y C r e e k - B o u n t i f u l s e c t o r of t h e W a s a t c h Range ( B y r o n S h a r p , p e r s o n a l c o m m u n i c a t i o n ) . In t h e C o t t o n w o o d dome of the W a s a t c h R a n g e it r e s t s on t h e e r o d e d Big C o t t o n w o o d s e r i es ( G r a n g e r , 1943, p . 2, and C r i t t e n d e n , 1952, p . 5). Since t h e p h y l l i te a r e in p l a c e s v a r v e d and g e n e r a l l y a s s o c i a t e d with t h e t i l l i t e s , it i s a s s u m e d t h a t t h e y a r e t i e d to t h e t i l l i t e s e q u e n c e and a r e not p a rt of the Big C o t t o n w o o d s e r i e s . Hence, it i s t e n t a t i v e l y c o n c l u d ed t h a t b o t h the l o w e r S h e e p r o c k s e r i e s and the t i l l i t e p r o g r e s s i v e ly o v e r l a p a t e r r a n e of o l d e r r o c k s , s u c h a s i n d i c a t e d in F i g u r e 2. The u p p e r S h e e p r o c k s e r i e s i s c o n f o r m a b l e with t h e u n d e r l y i ng t i l l i t e . In b e i n g c o m p o s e d c h i e f l y of t a n and l i g h t g r e e n s h a l e it i s u n l i k e the M u t u a l f o r m a t i o n of t h e W a s a t c h R a n g e w h i c h i s m a de up of a r g i i i i t e and q u a r t z i t e ( C r i t t e n d e n , 1952, p . 6 ) . The Mutual a l s o r e s t s with p r o n o u n c e d a n g u l a r u n c o n f o r m i t y on t h e M i n e r a l F o rk t i l l i t e , c u t t i n g it out e n t i r e l y and r e s t i n g in p l a c e s on t h e Big C o t t o n wood s e r i e s . It i s t h e r e f o r e a s s u m e d t h a t t h e u p p e r S h e e p r o c k s e r i es i s o l d e r t h a n t h e M u t u a l . The p o s t u l a t e d r e l a t i o n s a r e shown in F i g u r e 2 . The b e s t e v i d e n c e of t h e u n i t y of t h e u p p e r S h e e p r o c k s e r i e s, the Dutch P e a k t i l l i t e , and t h e l o w e r S h e e p r o c k s e r i e s , i s t h e f a c i es GOLD HILL (NOLAN ) SHEEPROCK (THIS P A P E R ) % TINTIC (MORRIS) DRY CAN I ~ L.RIDGE % (EARDLEY ' (MUSSIG T I N T I C QUARTZITE S H E E P R O C K S E R I ES BIG C O T T O N W O O D S E R I ES ( B E L T I A N ) ? / P R O P O S E D S T R A T I G R A P H I C R E L A T I O N ^ I P S ^ " O F T H E P R E C A M B R I AN IN W E S T C E N T R A L U T AH FIGURF 9 21 r e l a t i o n s h i p ; the t i l l i t e f i n g e r s and g r a d e s Into t h e S h e e p r o ck p h y i l i t e s a n d q u a r t z i t e s. *MutuaL(?) f o r m a t i on G e n e r a l s t a t e m e n t - The y o u n g e r s e q u e n c e of P r e c a m b r i an r o c k s c o n s i s t s of two d i s t i n c t i v e l i t h o i o g i c m e m b e r s , h e r e c o r r e l a t ed with t h e M u t u a l f o r m a t i o n of t h e W a s a t c h M o u n t a i n s . The M u t u a i ( ?) f o r m a t i o n r e s t s with q u e s t i o n a b l e u n c o n f o r m i t y upon b e d s of t he S h e e p r o c k s e r i e s . The e v i d e n c e a v a i l a b l e s u g g e s t s an u n c o n f o r m i t y, but l i m i t e d e x p o s u r e s of t h e c o n t a c t l e a v e s m u c h u n c e r t a i n t y about t h e r e l a t i o n s h i p s . However, the M u t u a i f ? ) f o r m a t i o n r e s t s upon v a r i o u s r o c k t y p e s of the u p p e r S h e e p r o c k s e r i e s . F o r e x a m p l e , in t h e T a i a w a g a r e a the M u t u a l f ? ) f o r m a t i o n a p p e a r s to r e s t upon the t r u n c a t e d e d g e s of the t a n q u a r t z i t e m e m b e r of t h e u p p e r S h e e p r o ck s e r i e s ; at V e r n o n C r e e k , in t h e c e n t r a l p a r t of t h e West T i n t i c Moun= t a i n s , the M u t u a l ( ? ) f o r m a t i o n r e s t s upon a t a n and d r a b s h a le s e q u e n c e ; in t h e Cow H o l l ow a r e a , the M u t u a l ( ? ) f o r m a t i o n r e s ts upon a t h i c k , white q u a r t z i t e . T h e s e r e l a t i o n s h i p s s t r o n g l y s u g g e st a n u n c o n f o r m i t y , although the v a r i o u s r o c k t y p e s upon which the M u t u a i ( ? ) f o r m a t i o n r e s t s m a y be f a d e s of a s i n g l e s e d i m e n t a r y unit, and not a c o m p o s i t e s u r f a c e. D i s t r i b u t i o n and t h i c k n e s s <= T h e M u t u a l ( ? ) f o r m a t i o n c r o p s out in t h r e e s m a l l a r e a s . The l a r g e s t o u t c r o p I s on t h e n o r t h dip s l o p e of T a i a w a g P e a k ( P l a t e VIII). v r Figure I I X b t d l t I a X 9 ^ ' l ^ ^ ' o f T a l a w a 9 «*- 22 i At t h e h e a d of Cow H o l l ow n e a r the s o u t h e a s t e r n edge of the m a p p e d a r e a an o v e r t u r n e d m e m b e r of t h e M u t u a l ( ? ) f o r m a t i on c o v e r s an a r e a of a p p r o x i m a t e l y two t h i r d s of a s q u a r e m i l e . South of B l a c k ' s R a n c h in t h e e a s t e r n p a r t of t h e S i m p s o n M o u n t a i n s i s a s m a l l e x p o s u r e of t h e M u t u a l ( ? ) f o r m a t i o n , and o t h e r s m a l l e x p o s u r es a r e on V e r n o n C r e e k. T h e t h i c k n e s s of t h e M u t u a l ( ? ) f o r m a t i o n i s 924 f e e t on T a i a w ag P e a k w h e r e b o t h the top and the b o t t om of t h e f o r m a t i o n c o u l d be f a i r ly a c c u r a t e l y l o c a t e d . The Cow H o l l ow s e c t i o n ( o v e r t u r n e d ) i s i n v o l v ed in t h r u s t f a u l t i n g and c a n not be r e l i a b l y m e a s u r e d. T o p o g r a p h i c e x p r e s s i o n - The M u t u a l ( ? ) f o r m a t i o n w e a t h e r s to f o r m c l i f f s and dip s l o p e s u n d e r c o n d i t i o n s p r e v a i l i n g in t h e S h e e p r o ck a r e a . The b a s a l s h a l e u n i t , t o g e t h e r with the s h a l e s of the u p p er S h e e p r o c k s e r i e s , w e a t h e r s to f o r m s a d d i e s. L i t h o i o g y - The Mutuai( ? ) f o r m a t i o n i s d i v i d e d i n t o two u n i t s: a b a s a l s l a t e o r a r g i l l i t e and an u p p e r c o n g l o m e r a t i c q u a r t z i t e . The u p p er u n i t i s r e f e r r e d to h e r e i n a s the T a i a w a g m e m b e r (new n a m e ) . T h e b a s a l u n i t c a n b e s t be d e s c r i b e d a s an a r g i l l i t e o r t h i n - b e d d ed a r g i l l a c e o u s q u a r t z i t e . The u n i t i s b e t w e e n 150 and 217 f e e t thick* T h e g e n e r a l c o l o r of the o u t c r o p i s d a r k purpLe a l t h o u g h a f ew thin b e d s a r e t a n . M u s c o v i t e m i c a i s p r o m i n e n t on t h e b e d d i n g p l a n e s. Much of t h e m a t e r i a l c o n t a i n s f i n e s a n d . The t h i n , flaggy b e ds t o g e t h e r with t h e c o l o r m a k e it d i s t i n g u i s h a b l e f r o m the o v e r l y i ng 23 c o n g l o m e r a t i c q u a r t z i t e . On T a i a w a g P e a k , r i p p l e m a r k s w e re o b s e r v e d ; s t r a t a r e s t o r e d to a h o r i z o n t a l p o s i t i o n i n d i c a t e t h a t the a q u e o u s c u r r e n t s flowed f r o m s o u t h w e s t to n o r t h e a s t . This c u r r e nt d i r e c t i o n is shown by r i p p l e m a r k s s e e n in t h e T a i a w a g a r e a . The b a s e of t h e s h a l e c o n t a c t s r o c k of v a r i e d l i t h o i o g y and c o l o r in d i f f e r e n t a r e a s , but at any s i n g l e l o c a l i t y the c o n t a c t a p p e a r s c o n f o r m a b l e . The a r g i l l i t e ( s h a l e ) g r a d e s i n t o t h e o v e r l y i n g c o n g l o m e r a t i c q u a r t z i t e . A f ew i n t e r c a l a t e d g r a y q u a r t z i t e s o c c u r in t h i s z o n e. T h e top of t h e u n i t i s t a k e n a s the h i g h e s t p u r p l e a r g i l l a c e o u s bed. T h e T a i a w a g q u a r t z i t e m e m b e r on t h e n o r t h s l o p e of T a i a w ag P e a k i s 706 f e e t t h i c k . It i s c o m p o s e d of q u a r t z i t e , c o n g l o m e r a t ic q u a r t z i t e , and c o n g l o m e r a t e . The q u a r t z i t e i s p r i n c i p a l l y c o a r s e g r a i n e d , and c r o s s - b e d d i n g i s p r e s e n t , but not p r o m i n e n t in t h e l o w er 500 f e e t . The T a i a w a g m e m b e r c o n t a i n s c o n g l o m e r a t e l e n s e s c o m p o s e d of white and p u r p l e q u a r t z i t e c o b b l e s and p e b b l e s . Q u a r t z and j a s p e r p e b b l e s w e r e n o t e d about 300 f e e t above the b a s e . The w e a t h e r e d r o c k i s only s l i g h t l y d a r k e r in h u e than the f r e s h r o c k. P u r p l e c o l o r a t i o n , except f o r the c o n s t i t u e n t a r e n a c e o u s m a t e r i a l, i s s e c o n d a r y . Near s o m e f a u l t s the r o c k i s m o r e pink o r r e d d i s h. T h e c o l o r of the unit i s i m p a r t e d by p u r p l e and r e d , i n t e r g r a n u l ar m i n e r a l s . In m a n y l o c a l i t i e s the s o a k i n g e f f e c t of s o l u t i o n s h a s l o c a l ly p r o d u c e d a f a l s e c r o s s - b e d d i n g. 24 F i e l d i d e n t i f i c a t i o n - The c o a r s e n e s s of the c o n s t i t u e n t g r a i ns of the T a i a w a g q u a r t z i t e t o g e t h e r with a f ew j a s p e r p e b b l e s and g e n e r a l l y a d e e p p u r p l e t i n t s e r v e to d i s t i n g u i s h it f r o m the o v e r l y i n g T i n t i c q u a r t z i t e . Except f o r s e v e r a l t h i n p u r p l e u n i t s within t h e T i n t i c q u a r t z i t e , t h e r e a r e no o t h e r q u a r t z i t e s t h a t c a n be m i s t a k e n f o r T a i a w a g in the a r e a. C o r r e l a t i o n - At the t y p e s e c t i o n , the M u t u a l q u a r t z i t e u n c o n - f o r m a b l y o v e r l i e s the B i g C o t t o n w o o d s e r i e s and t h e M i n e r a l F o rk t i l l i t e a n d i s in t u r n u n c o n f o r m a b i y o v e r l a i n by t h e T i n t i c q u a r t z i t e. No s t r a t a a s old a s t h e B i g C o t t o n w o o d s e r i e s c a n p o s i t i v e l y be i d e n t i f i e d in t h e S h e e p r o c k R a n g e . Q u e s t i o n a b l e u n c o n f o r m i t i e s o c c ur a b o v e and b e l o w the M u t u a l ( ? ) f a c i e s in t h e S h e e p r o c k a r e a . The s t r a ta u n d e r l y i n g t h e M u t u a i ( ? ) f o r m a t i o n c o n f o r m a b l y o v e r l i e and a re g r a d a t i o n a L with t h e Dutch P e a k t i l l i t e. S i m i l a r s t r a t i g r a p h i c p o s i t i o n and l i t h o l o g i e s , s u c h a s the p u r p le c o l o r a t i o n , g r a i n s i z e , and the p r e s e n c e of p u r p l e a r g i l l i t e s , s u g g e st t h a t t h e M u t u a i ( ? ) s t r a t a of the S h e e p r o c k R a n g e c o r r e l a t e with the t y p e M u t u a l . In t h e S h e e p r o c k R a n g e , h o w e v e r , the s t r a t a both a b o v e and b e l o w a r e p r o b a b l y c o n f o r m a b l e w h e r e a s at t h e type s e c t i o n an u n c o n f o r m i t y e x i s t s at the b a s e of the M u t u a l and, being t h e y o u n g e s t of the p r e s e r v e d P r e c a m b r i a n s t r a t a , it i s u n c o n f o r m a b i y o v e r l a i n by t h e b a s a l C a m b r i a n q u a r t z i t e ( T i n t i c ) . N. C. W i l l i a m s ( 1 9 5 3 , p. 2783), h o w e v e r , h a s c o r r e l a t e d the t y p e Mutual with s i m i l a r s t r a t a in t h e U i n t a M o u n t a i n s and h a s n o t e d that t h e R e d P i n e s h a l e , y o u n g e s t P r e c a m b r i a n unit p r e s e r v e d in the w e s t e r n U i n t a M o u n t a i n s , c o n f o r m a b l y o v e r l i e s the Mutual q u a r t z i t e . The T i n t i c q u a r t z i t e , in t u r n , t r u n c a t e s both the M u t u a l f o r m a t i o n and the Red P i n e s h a l e . No s h a l e o v e r l i es t h e M u t u a i ( ? ) s t r a t a In the S h e e p r o c k a r e a and the t y p e a r e a of t h e M u t u a l ; h o w e v e r , such a s h a l e m a y h a v e b e e n p r e s e n t but e r o d e d p r i o r to C a m b r i a n d e p o s i t i o n . The M u t u a l f o r m a t i o n at I t s t y p e l o c a l i t y i s 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 but b e c a u s e It is b o u n d e d by u n c o n f o r m i t i e s i t s o r i g i n a l t h i c k n e s s c a n n o t be m e a s u r ed P r e c a m b r i a n c o r r e l a t i on Many p r o b l e m s e x i s t in t h e c o r r e l a t i o n of P r e c a m b r i a n r o c k s. H i n d s (1935=36) r e v i e w s the P r e c a m b r i a n g e o l o g y of w e s t e rn N o r t h A m e r i c a and in s u m m a r y d i v i d e s the P r e c a m b r i a n i n t o (1) A r c h e a n , (2) U n c o m p a h g r a n , and (3) A l g o n k i a n ( B e l t i a n ) s y s t e m s. A r c h e a n r o c k s ( H i n d s , 1936, p . 12) of t h e Big and L i t t le C o t t o n w o o d Canyon a r e a s of t h e W a s a t c h M o u n t a i n s h a v e b e e n d e s i g n a t e d by C r i t t e n d e n , S h a r p , and C a l k i n s (1952, p. 3) a s the L i t t le W i l l ow s e r i e s and c o r r e l a t i o n with the F a r m i n g t o n Canyon c o m p l ex ( E a r d l e y and H a t c h , 1940, p. 61) i s s t r o n g l y s u g g e s t e d. T i l l i t e and v a r v e d s l a t e u n i t s f o r m e r l y w e r e i n c l u d e d in the C o t t o n w o o d s e r i e s and d e s i g n a t e d by H i n d s (1936, p . 134) as U n c o m p a h g r a n . C r i t t e n d e n et a l . (1952, p. 3-5) d e m o n s t r a t e d that 26 t h e t i l l i t e u n c o n f o r m a b l y o v e r l i e s the C o t t o n w o o d s e r i e s and h a ve d e s i g n a t e d t h e l o w e r b e d s a s the Big C o t t o n w o o d s e r i e s and the u p p e r a s the M i n e r a l F o r k t i l l i t e. H i n d s (1936, p . 135) i n d i s c u s s i n g B e l t i a n r o c k s s t a t e s , " S o - c a l l e d a l g a l s t r u c t u r e s a r e c o m m o n in the l i m e s t o n e s " . C r i t t e n d en ( p e r s o n a l c o m m u n i c a t i o n , 1955) found l a r g e c i r c u l a r and o v a l - s h a p e d markings in the l i m e s t o n e b o u l d e r s in t h e M i n e r a l F o r k t i l l i t e. P o r t i o n s of s i m i l a r m a r k i n g s w e r e o b s e r v e d in l i m e s t o n e b o u l d e rs i n t h e Dutch P e a k t i l l i t e of the S h e e p r o c k a r e a . Both o c c u r r e n c es s u g g e s t o r g a n i c o r i g i n - - p o s s i b l y a l g a i ° - a n d the m a r k i n g s found in t h e l i m e s t o n e b o u l d e r s s t r o n g l y s u g g e s t a B e l t i a n age f o r the l i m e s t o n e s . If t h e l i m e s t o n e s a r e B e l t i a n , the t l i l i t e s a r e l a t e r B e l t i a n. U n c o n f o r m a b l y o v e r l y i n g the M i n e r a l F o r k t i l l i t e ( C r i t t e n d en e t a i . , 1952, p . 6) i s the M u t u a l f o r m a t i o n . S i m i l a r l y , in the S h e e p r o c k M o u n t a i n s , the f o r m a t i o n t e n t a t i v e l y c o r r e l a t e d with the M u t u a l , u n c o n f o r m a b l y o v e r l i e s t h e u p p e r S h e e p r o c k s e r i e s. A s s u m i n g the l i m e s t o n e b o u l d e r s a r e B e l t i a n t h e n at l e a s t two l a t e - B e l t i a n , P r e c a m b r i a n s e r i e s m a y be p r e s e n t : (1) The s t r a ta r e p r e s e n t e d by t h e e n t i r e S h e e p r o c k s e r i e s and the M i n e r a l F o rk t i l l i t e ; and (2) The s t r a t a r e p r e s e n t e d by the M u t u a l f o r m a t i o n . The u p l i f t c a u s i n g t h e u n c o n f o r m i t y b e t w e e n t h e M u t u a l f o r m a t i o n and t h e o v e r l y i n g T i n t i c ( C a m b r i a n ) q u a r t z i t e a f f o r d e d an e n v i r o n m e nt which p r o v i d e d the a d v a n c i n g C a m b r i a n s e a with m a t e r i a l f o r the 27 basaL C a m b r i a n q u a r t z i t e s. P r e c a m b r i a n - C a m b r i a n c o n t a ct In the w e s t e r n U n i t e d S t a t e s the b a s e of t h e C a m b r i a n s y s t e m is LocaLIy i n d e f i n i t e , e s p e c i a l l y s i n c e the b a s a l C a m b r i a n r o c k s a re n O n f o s s i l i f e r o u s q u a r t z i t e s . G e n e r a l l y , the b a s e of t h e C a m b r i a n is t a k e n at the f i r s t u n c o n f o r m i t y b e l ow the b a s a l q u a r t z i t e c o n f o r m a b ly u n d e r l y i n g f o s s i l i f e r o u s C a m b r i a n s t r a t a . However, in p a r t s of s o u t h w e s t e r n N e v a d a g r e a t t h i c k n e s s e s of s t r a t a a r e a s s i g n e d to the C a m b r i a n s y s t e m ( H a z z a r d , 1937). The c o n f o r m a b i i i t y of t h e s t r a ta t o g e t h e r with t h e i r g r e a t t h i c k n e s s s u g g e s t t h e p o s s i b i l i t y t h a t the P r e c a m b r i a n - C a m b r i a n b o u n d a r y m a y o c c u r within a c o n f o r m a b le s e q u e n c e in p l a c e s . Nolan (1935, p . 6) i n d i s c u s s i n g the b a s al C a m b r i a n q u a r t z i t e s in the Deep C r e e k M o u n t a i n s of w e s t e r n Utah, a s s i g n s a t h i c k b a s a l s e q u e n c e of q u a r t z i t e s and s h a l e s to the P r o s p e c t M o u n t a i n q u a r t z i t e . The P r o s p e c t M o u n t a i n q u a r t z i t e was f i r s t d e s c r i b e d by Hague ( 1 8 8 3 , pp. 253, 254) in the E u r e k a d i s t r i ct ( N e v a d a ) . As the b a s e of the P r o s p e c t M o u n t a i n i s not e x p o s e d at E u r e k a , N e v a d a , Nolan (1935, p . 4-6) at Gold H i l l e x t e n d e d the f o r m a t i o n to i n c l u d e the e n t i r e c o n f o r m a b l e s e q u e n c e - - 2 , 750+ f e et of s h a l e s and q u a r t z i t e s c o n f o r m a b l y u n d e r l y i n g the u p p e r m o s t 2, 500 f e e t of q u a r t z i t e. T h e w r i t e r s u g g e s t s t h a t the u p p e r m o s t 2, 500 f e e t of l i g h t c o l o r ed q u a r t z i t e m a y be T i n t i c and t h e s h a l e and q u a r t z i t e s t r a t a b e l o w M u t u a l. 28 The f o l l o w i n g o b s e r v a t i o n s s u p p o r t the p r o p o s a l . F o s s i l s c o l l e c t ed f r o m the o v e r l y i n g C a b i n s h a l e w e r e i d e n t i f i e d a s L o w e r C a m b r i an t y p e s . Other c o l l e c t i o n s f r o m the B u s b y f o r m a t i o n in the S h e e p r o ck M o u n t a i n s i n d i c a t e an a g e n e a r t h e M i d d l e - L o w e r C a m b r i a n b o u n d a r y. C o n f o r m a b l y u n d e r l y i n g a p p r o x i m a t e l y 300 f e e t of P i o c h e s h a l e in t h e S h e e p r o c k M o u n t a i n s i s 2, 572 f e e t of s t r a t a a s s i g n e d to the T i n t i c q u a r t z i t e . A s s u m i n g the P i o c h e f a c i e s of t h e S h e e p r o c k a r ea i s l o w e r C a m b r i a n a s i s the C a b i n f a c i e s at Gold H i l l , one m a y then a s s u m e t h a t t h e u p p e r q u a r t z i t e u n i t of t h e P r o s p e c t M o u n t a i n q u a r t z i te a t Gold H i l l a n d t h e T i n t i c q u a r t z i t e in t h e S h e e p r o c k M o u n t a i n s a re t h e s a m e , and t h a t the l o w e r s h a l e and q u a r t z i t e u n i t s at Gold H i ll a r e M u t u a l ( ? ) f a c i e s of P r e c a m b r i a n a g e. T h e b a s a l C a m b r i a n s t r a t a a p p a r e n t l y o v e r l a p p r o g r e s s i v e l y f r om w e s t to e a s t o l d e r P r e c a m b r i a n r o c k s , and i t t h e r e f o r e s e e m s p o s s i b le o r e v e n p r o b a b l e t h a t in the c e n t r a l and w e s t e r n p a r t of t h e G r e at B a s i n g r a d a t i o n a l c o n t a c t s e x i s t . Without m e a n i n g f u l i i t h o i o g ic b r e a k s , the c o n t a c t will be d i f f i c u l t to r e c o g n i z e , h o w e v e r. CAMBRIAN SYSTEM G e n e r a l s t a t e m e nt T h e C a m b r i a n s y s t e m of t h e S h e e p r o c k M o u n t a i n s i s r e p r e s e n t ed by 13 f o r m a t i o n s a g g r e g a t i n g b e t w e e n 8, 000 and 8, 500 f e e t of s t r a t a. F o r m a t i o n a i t e r m i n o l o g y i s t a k e n f r o m s e c t i o n s in t h e H o u s e R a n ge a n d t h e E a s t T i n t i c M o u n t a i n s . The b a s i s f o r the t e r m i n o l o g y and c o r r e l a t i o n s i s d i s c u s s e d in d e t a i l in l a t e r p a r a g r a p h s. T h e P r e c a m b r i a n - C a m b r i a n b o u n d a r y i s v a g u e and q u e s t i o n a b le i n t h e S h e e p r o c k s a s in m a n y o t h e r G r e a t B a s i n s e c t i o n s . The T i n t ic i s n o n f o s s i i i f e r o u s and i t s b a s e m a y be well within t h e P r e c a m b r i a n. T i n t i c q u a r t z i te G e n e r a l s t a t e m e n t - The T i n t i c q u a r t z i t e i s s e p a r a t e d f r o m the u n d e r l y i n g M u t u a l ( ? ) f o r m a t i o n by a q u e s t i o n a b l e u n c o n f o r m i t y . The t o p of t h e T a i a w a g q u a r t z i t e m e m b e r of t h e M u t u a l ( ? ) f o r m a t i o n is t r a n s i t i o n a l with the o v e r l y i n g T i n t i c q u a r t z i t e . The b a s a l u n i ts of t h e T i n t i c q u a r t z i t e a r e white and i v o r y with a s l i g h t but n o t i c e a b l e a m o u n t of g r e e n c o l o r due to a m i c a c e o u s , i n t e r s t i t u a l m i n e r al b e l i e v e d to b e g l a u c o n i t e . The c o l o r c h a n g e f r o m p u r p l e h u e s to white a n d the p r e s e n c e of g l a u c o n i t e w e r e t a k e n a s t h e c o n t a c t b e t w e e n the M u t u a i ( ? ) f o r m a t i o n and t h e T i n t i c q u a r t z i t e. D i s t r i b u t i o n and t h i c k n e s s - The T i n t i c q u a r t z i t e c r o p s out in a b a n d o v e r a m i l e in width on t h e l o w e r s p u r s a l o n g t h e n o r t h f r o nt of t h e S h e e p r o c k M o u n t a i n s . The f o r m a t i o n t r e n d s n o r t h w e s t e r ly 30 f r o m i t s t h i n e a s t e r n o u t c r o p above a t h r u s t f a u l t in t h e m o u t h of H a r k e r C a n y o n , and g r a d u a l l y w i d e n s w e s t e r l y and c r o s s e s the m a i n , n o r t h - s o u t h d i v i d e a s a dip s l o p e u n i t n o r t h of T a i a w a g P e a k. The T i n t i c q u a r t z i t e i s r e p e a t e d n o r t h of an e a s t - w e s t r e v e r s e fault b e t w e e n T a i a w a g and Lookout P e a k s and h e r e m a i n t a i n s a n e a r ly e a s t - w e s t s t r i k e and a 4 5 - d e g r e e n o r t h e r l y d i p . A s i z a b l e s e g m e nt of T i n t i c q u a r t z i t e s t r i k e s w e s t e r l y in a 3, 0 0 0 - f o o t b a n d a c r o ss t h e d i v i d e b e t w e e n M e a d o w and J u d d C r e e k s s o u t h w e s t of B l a c k 's R a n c h in the e a s t e r n S i m p s o n M o u n t a i n s . S e v e r a l o u t c r o p s of q u a r t z i t e which l i e a b o v e and in f a u l t c o n t a c t with t h e S h e e p r o ck s e r i e s in t h e e a s t e r n p a r t of t h e a r e a h a v e t e n t a t i v e l y b e e n i d e n t i f i ed a s t h e T i n t i c q u a r t z i t e. As n o p r o n o u n c e d b a s a l u n i t w a s o b s e r v e d in t h e T i n t i c q u a r t z i te and b e c a u s e p a i e o n t o l o g i c a l e v i d e n c e i s l a c k i n g , the b a s e of t he T i n t i c q u a r t z i t e m a y be a r b i t r a r i l y p l a c e d at a p o i n t w h e r e c o n g l o m e r a te l e n s e s , c o n t a i n i n g b r i g h t r e d j a s p e r p e b b l e s , b e c o m e s i g n i f i c a n t , the j a s p e r s b e i n g a r b i t r a r i l y c o n s i d e r e d a s b a s a l C a m b r i a n . C o n g l o m e r a te l e n s e s a r e m o r e p r o n o u n c e d in t h e c o n f o r m a b l y u n d e r l y i n g T a i a w ag q u a r t z i t e , but s i n c e t h i s u n i t a v e r a g e s about 850 f e e t in t h i c k n e s s and i s u s u a l l y p u r p l e , it would p r o b a b l y be b e s t to c o n s i d e r t h i s a s e p a r a te u n i t r a t h e r t h a n b a s a l T i n t i c . On t h e b a s i s of t h i s r e a s o n i n g the u p p e r l i g h t e r q u a r t z i t e f a c i e s h a v e b e e n a s s i g n e d to t h e T i n t i c to g i ve a t o t a l of 2, 572 f e e t of s t r a t a. 31 T o p o g r a p h i c e x p r e s s i o n - The T i n t i c q u a r t z i t e w e a t h e r s to f o r m w e l l - e x p o s e d l e d g e s but at c o n s i d e r a b l y l o w e r e l e v a t i o n s t h an e i t h e r the u n d e r l y i n g T a i a w a g q u a r t z i t e o r t h e o v e r l y i n g m i d d le C a m b r i a n l i m e s t o n e s . The r i d g e s and s a d d l e s f o r m e d by t h e T i n t ic a r e due t o f r a c t u r i n g and m e c h a n i c a l e r o s i o n . The i n a b i l i t y of the T i n t i c to p r o v i d e a s u i t a b l e p a r e n t m a t e r i a l f o r s o i l f o r m a t i o n is m o r e than any o t h e r f a c t o r r e s p o n s i b l e f o r the e x c e l l e n t e x p o s u r e s. L i t h o i o g y - The T i n t i c q u a r t z i t e i s a t y p i c a l m e d i u m - g r a i n ed q u a r t z i t e which i s u s u a l l y h i g h l y j o i n t e d a n d f r a c t u r e d . Its c o l o r, which h a s g e n e r a l l y b e e n r e f e r r e d to a s buff, i s v a r i e d , r a n g i ng f r o m white t h r o u g h p u r p l e s with p i n k a n d g r e e n t i n t s not u n c o m m o n. Y e l l o w s a n d b r o w n s a r e t y p i c a l of t h e c o l o r a t i o n f o r 80 t o 90 p e r c e nt of t h e s t r a t a in t h e T i n t i c q u a r t z i t e in t h e S h e e p r o c k M o u n t a i n s. S t r a t a in o r n e a r f a u l t z o n e s c o n t a i n a b u n d a n t l i m o n i t e a s s t a i ns and f r a c t u r e f i l l i n g. B e d d i n g i s not e v e r y w h e r e d i s t i n c t but i n p l a c e s e i t h e r m i c a c e o us p a r t i n g s o r c r o s s - b e d d i n g i s p r e s e n t and a f f o r d s o p p o r t u n i t y for m e a s u r e m e n t . Small o u t c r o p s of t h e T i n t i c a r e u s u a l l y d e v o i d of b e d d i n g . C o n g l o m e r a t e l e n s e s a r e p r e s e n t in t h e l o w e r 400 f e e t of t he T i n t i c q u a r t z i t e . The h i g h e s t p u r p l e b e d s a r e about 700 f e e t above t h e b a s e . The p u r p l i s h s t r a t a a r e g e n e r a l l y c o a r s e - g r a i n e d and l o w e r p o r t i o n s c o n t a i n p e b b l e s of p e g m a t i t i c q u a r t z and g r a y and 32 p u r p l e q u a r t z i t e . J a s p e r o i d p e b b l e s a r e p r e s e n t u p to 200 f e e t above t h e b a s e . W e l l - r o u n d e d p e b b l e s up to \ \ i n c h e s a r e p r e s e n t in t he c o n g l o m e r a t e f r a c t i o n s. G r e e n m i c a c e o u s s h a l e p a r t i n g s up to one i n c h in t h i c k n e s s o c c ur i n t h e u p p e r 450 f e e t of t h e T i n t i c . These p a r t i n g s i n d i c a t e p r o x i m i ty t o t h e o v e r l y i n g P i o c h e s h a l e. D a r k p u r p l e a r g i l l i t e s , h a v i n g a m i c a c e o u s s h e e n , w e r e found n e a r t h e c e n t e r of t h e T i n t i c but p r o v e d to be of l o c a l e x t e n t o n l y. B a s a l T i n t i c s t r a t a i n c l u d e a g r e e n i s h t i n t e d q u a r t z i t e with v e r y t h i n m i c a c e o u s p a r t i n g s . The c o l o r a t i o n of t h e q u a r t z i t e is due to t h e d i s p e r s a l of a g r e e n m i c a c e o u s m i n e r a l in t h e i n t e r s t i t u ai c e m e n t . This unit i s 75 f e e t t h i c k. T h e top of t h e T i n t i c i s v e r y d i s t i n c t and i s t a k e n at t h e b a s e of t h e t a n a n d o l i v e w e a t h e r i n g q u a r t z i t e s and s h a l e s of t h e o v e r l y i ng P i o c h e s h a l e. F i e l d i d e n t i f i c a t i o n - The T i n t i c q u a r t z i t e i s at p l a c e s difficult to d i s t i n g u i s h f r o m the v a r i o u s P r e c a m b r i a n q u a r t z i t e s . The p r e s e n ce of t h e f u c o i d a l s e c t i o n of t h e O p h i r f o r m a t i o n at t h e top of t h e T i n t ic q u a r t z i t e i s the b e s t c r i t e r i a f o r i d e n t i f i c a t i o n . The b a s e of t he T i n t i c q u a r t z i t e i s of v e r y i n c o n s t a n t and e r r a t i c l i t h o i o g y . Dark r ed j a s p e r o i d p e b b l e s in c o n g l o m e r a t i c z o n e s w e r e u s e d a s a m e a n s f or d e t e r m i n i n g the b a s e . These p e b b l e s w e r e found to e x t e n d f o r a 33 c o n s i d e r a b l e i n t e r v a l i n t o t h e u n d e r l y i n g p u r p l e q u a r t z i t e s of t h e w T a i a w a g a s well a s i n t o the g r e e n i s h t i n t e d white to t a n q u a r t z i t es a s s i g n e d to t h e T i n t i c . The c o l o r c h a n g e f r o m p u r p l e to t a n was f o u n d to be v e r y e r r a t i c even in s h o r t d i s t a n c e s and p u r p l e b e d s w e re found a f ew h u n d r e d f e e t a b o v e t h e r e d p e b b l e s a s w e r e o c c a s i o n a l s i x - i n c h b e d s of m i c a c e o u s p u r p l e s l a t e s of t h e t y p e c o m m o n to t h e b a s al T a i a w a g . C r o s s - b e d d i n g i s c o m m o n in b o t h t h e T a i a w a g m e m b e r of the M u t u a l ( ? ) f o r m a t i o n and the T i n t i c q u a r t z i t e and c a n n o t s e r v e as d i f f e r e n t i a t i n g c r i t e r i a . Near t h e t o p of t h e T i n t i c q u a r t z i t e , thin b e ds of l i g h t g r e e n , v e r y m i c a c e o u s s h a l e s s e r v e a s a g u i d e to t h e p r o x i m i ty of t h e O p h i r s h a l e. C o r r e l a t i o n - The T i n t i c q u a r t z i t e of t h e S h e e p r o c k M o u n t a i n s is c o r r e l a t e d with s u r r o u n d i n g s e c t i o n s on t h e b a s i s of l i t h o i o g y and s t r a t i g r a p h i c p o s i t i o n . In the E a s t T i n t i c R a n g e t h e t y p e T i n t i c h as b e e n r e d e f i n e d by M o r r i s ( p e r s o n a l c o m m u n i c a t i o n ) and r e s t r i c t ed t o t h o s e q u a r t z i t e s above t h e j a s p e r o i d c o n g l o m e r a t e s and b e l o w the O p h i r s h a l e . The T i n t i c ( r e d e f i n e d ) a g g r e g a t e s a p p r o x i m a t e l y 3, 000 f e e t of s t r a t a. T h e P r o s p e c t M o u n t a i n q u a r t z i t e of Gold H i l l i s i n p a r t the l i t h o l o g i c e q u i v a l e n t of t h e T i n t i c q u a r t z i t e in the S h e e p r o c k M o u n t a i n s. T h e u p p e r m o s t unit of t h e P r o s p e c t M o u n t a i n d e f i n e d by N o l a n ( 1 9 3 5, p . 6) i s a " m a s s i v e , d o m i n a n t l y l i g h t c o l o r e d q u a r t z i t e " and i s 2 , 5 00 f e e t t h i c k . The w r i t e r b e l i e v e s t h a t t h i s u n i t i s r e p r e s e n t a t i v e of 34 t h e T i n t i c q u a r t z i t e of t h e S h e e p r o c k M o u n t a i n s . The s l a t e s o r s h a le m e m b e r s a s d e s c r i b e d by N o l a n m a y b e p r e s e n t in t h e S h e e p r o ck s e q u e n c e but t h e i r i n c l u s i o n in t h e T i n t i c q u a r t z i t e would i n c r e a se i t s t h i c k n e s s of 2, 572 f e e t by 3, 500 to 4, 300 f e e t g i v i n g an a g g r e g a te t o t a l of a p p r o x i m a t e l y 6, 900 f e e t f o r the P r o s p e c t M o u n t a i n or T i n t i c q u a r t z i t e. A l t h o u g h t h e T i n t i c - P r e c a m b r i a n c o n t a c t was e s t a b l i s h e d on the b a s i s of j a s p e r o i d p e b b l e s , it m a y be well to i n c l u d e the 800 f e e t of p u r p l e t i n t e d c o n g l o m e r a t i c q u a r t z i t e which l i e s b e t w e e n the j a s p er p e b b l e zone and t h e u n d e r l y i n g p u r p l e a r g i l l i t e in t h e T i n t i c q u a r t z i t e. T h i s z o n e of q u a r t z i t e c o n t a i n s m a n y l e n s e s of c o n g l o m e r a t e and r e s ts with a p p a r e n t c o n f o r m i t y on t h e a r g i l l i t e . The p u r p l e a r g i l l i te t h i n s and t h i c k e n s and i n p l a c e s i s a b s e n t . Other q u a r t z i t e s l e ns with t h e a r g i l l i t e and m a y r e p r e s e n t an u n c o n f o r m i t y . If t h i s is a v a l i d u n c o n f o r m i t y , it i s so s l i g h t a s to be m i s t a k e n f o r c o n t i n u o us s e d i m e n t a t i o n . However, t h e r e a r e no q u a r t z i t e s o r q u a r t z i t ic c o n g l o m e r a t e s b e l o w the a r g i l l i t e s t h a t a r e t y p i c a l of e i t h e r the p u r p l e o r b r o w n v a r i e t i e s of t h e o v e r l y i n g s t r a t a . The a r g i l l i t es m a y be r e p r e s e n t a t i v e of t h e top of t h e M u t u a l f o r m a t i o n ; if s o, d r a s t i c f a c i e s c h a n g e s h a v e o c c u r r e d in t h e M u t u a l f o r m a t i o n b e t w e en t h e t y p e l o c a l in t h e W a s a t c h M o u n t a i n s and t h e S h e e p r o c k a r e a. 35 O p h i r g r o up G e n e r a l s t a t e m e n t - C o r r e l a t i o n of t h e O p h i r f o r m a t i o n of the S h e e p r o c k M o u n t a i n s with p r e v i o u s l y d e s c r i b e d s e c t i o n s n e a r by p o s e s c e r t a i n p r o b l e m s of l i t h o l o g i c and f a u n a l e q u i v a l e n c y and c o n t a c t p o s i t i o n s which m u s t be r e c o n c i l e d. L o u g h i i n ( 1 9 1 9 , p . 23) in d i s c u s s i n g the top of t h e Tin t i c q u a r t z i te of t h e E a s t T i n t i c M o u n t a i n s s t a t e s: " i n t h e e a s t e r n m o s t r a i l r o a d cut i n the l o w er p a r t of E u r e k a Gulch t h e r e a r e a f ew i n s i g n i f i - c a n t s l a t e b a n d s f r o m two i n c h e s to one foot t h i c k . . . . t h e r o c k a s a whole g r a d u a l l y b e c o m es s l i g h t l y a r g i l l a c e o u s and t h i n - b e d d e d with f i n e ly m i c a c e o u s p a r t i n g s , o n e - f o u r t h of an i n c h a p a r t. . . . T h i s v a r i e t y p a s s e s c o n f o r m a b l y but a b r u p t l y i n t o t h e b r o w n - w e a t h e r i n g , highly m i c a c e o u s and c a l c a r e o u s s a n d s t o n e and s h a le at the b a s e of the O p h i r ." The O p h i r s h a l e was m e a s u r e d " f r o m the t o p of t h e T i n t i c q u a r t z i te to the top of t h e u p p e r m o s t s l a t e b e d " (1919, p. 23) and f o r s i x l o c a l i t i es in the d i s t r i c t the O p h i r s h a l e a v e r a g e d 400 f e e t in t h i c k n e s s . T h e r e a re two c h o i c e s in t h e S h e e p r o c k s e q u e n c e f o r the t o p of t h e O p h i r s h a le if the f o r e g o i n g , t o g e t h e r with F i g u r e 4 of L o u g h i i n ' s w o r k ( 1 9 1 9 , p . 25) a r e c o n s i d e r e d : (1) The s t r a t a lying b e t w e e n the t o p of t h e T i n t ic q u a r t z i t e and t h e b a s e of the u p p e r l i m e s t o n e m e m b e r of t h e M i l l a rd f o r m a t i o n would a g g r e g a t e a t o t a l of a p p r o x i m a t e l y 613 f e e t of r o ck a s s i g n a b l e to t h e O p h i r f o r m a t i o n , or (2) B e t w e e n t h e t o p of the T i n t i c q u a r t z i t e and the b a s e of t h e l i m e s t o n e m e m b e r of t h e S w a s ey |
