Subsurface stratigraphy of the Wasatch Formation of the Uinta Basin, Utah

The Wasatch formation of t h e Uinta Basin has g r a d a t i o n a l b o u n d a r i e s. The upper p o r t i o n of the formation, i s eq_ui.va.lent in time t o , - and i n t e r - f i n g e r s with, the black s h a l e f a d e s of t h e Green River format i o n . The lower p o r t i o n of the Wasatch i n t e r f i n g e r s with t h e North Horn and Tuscher f o r m a t i o n s . To the west in the Red Narrows - Thistle - S o l d i e r Summit a r e a the c o r r e l a t i o n of t h e Wasatch i s in doubt. Spieker (19^-6) has a s s i g n e d a Montanan age for the conglomerates exposed at Red Narrows- Recent work by Hintze (1962) and Boyd (1959) i n d i c a t e t h e y b e l i e v e t h e s e conglomerate t o be younger, p o s s i b l y North Horn in age. In t h e n o r t h e r n and e a s t e rn p o r t i o n s of the basin, t h e Wasatch i s l e s s than. 1000 f e e t t h i c k , and is unconformably o v e r l a i n by t h e Green River formation, and i s u n d e r l a in by the Mesaverde group of l a t e Cretaceous age. Southward t h e Wasatch formation t h i n s toward t h e Book. C l i f f s and c o n s i s t s of 75 f e e t of sandstones and s h a l e s o c c u r i n g between the Green River and Tuscher formations in t h e San Arroyo area. The author suggests t h a t the name Colton formation be reduced in r a n k t o the Colton tongue of the Wasatch formation, and t h a t the term Tuscher formation, be abandoned. In p l a c e of Tuscher formation i t is s u g g e s t e d t h a t i t be c a l l e d the b a s a l member of the Wasatch formation. I n t h e subsurface the Tuscher cannot be r e c o g n i z e d as a s e p e r a t e u n i t. The Wasatch formation is c o n s i d e r e d t o be an accumulation of cont i n e n t a l f l u v a t i l e sediments approaching feet in t h e c e n t r a l p o r t i on of the "basin.- All of t h e l a c u s i j e r i n e o s t r a c o d a l , . and o o l i t i c l i m e s t o n es near t h e t o p of f h e Wasatch f o r m a t i o n are excluded and p l a c e d i n t o t he "black s h a l e f a c i e s of t h e Green River f o r m a t i o n . The dominant l l t h o l o gy of t h e Wasatch i s red-brown s h a l e and f i n e - g r a i n e d subgraywacke sands t o n e . Great l a t e r a l v a r i a t i o n s in l l t h o l o g y cause d i f f i c u l t i e s in c o r r e l a t i o n between i n d i v i d u a l w e l l s .