184 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



WAHSATCH GROUP. 



In the western part of Area B the Wahsatch group cannot be definitely 

 separated from the overlying Green Eiver nor from the underlying 

 Laramie. I therefore pass to the eastern portion of the district. 



A belt of Wahsatch beds extends from Grand Eiver up Roan Creek a 

 little above the bend, southeast of Station 27. The creek appears to 

 occupy the axis of an anticlinal fold in the variegated beds. The out- 

 crop becomes thicker as we descend until the entire thickness is exposed. 

 At the top are laminated sandstones and greenish shales. These may 

 be the lower portion of the Green River group. Below are the variegated 

 greenish, yellow, and red marls and shales, separated by bands of lami- 

 nated sandstone. The latter are not persistent, but often entirely fade 

 out. On Grand River I counted five separate bands, which varied in 

 thickness. At one place they were 50 to 75 feet thick, and a short dis- 

 tance beyond only 5 or 10 feet. Some of these sandstones are pink, 

 others yellow or greenish, in tint. In most places the variegated beds 

 weather into the columns, spires, and other forms so characteristic of 

 Bad Lands. These beds are the same that in 1874 were referred to the 

 Green River group, in which was included the Wahsatch group (Report 

 1874, p. 150). From the beds on Plateau Creek the following vertebrate 

 remains were obtained: CrocodUus, Eniys, Trionyx, Pappichthys. 



In the Cactus Valley, a low mesa extends southward from the Grand 

 Hogback Range east of Rifle Creek. In the bluff, ou the east side of 

 this mesa, the following fossil plants were found: Bhamnus, species new, 

 Aralia gracilis. Of these Professor Lesquereux says : " No. 5 (the num- 

 ber of the specimens) has two species only, a new species of Rhamnus 

 like R. Goldiamis, Lesqx. (Lower Lignite), but with a somewhat different 

 nervation, more like species of tlie Lower Miocene of Europe. Aralia 

 {Araliopsis) gracilis, Lesqx., is a very fine species, as yet represented by 

 one specimen only from Bridger Pass. Again he says: '' Specimens No. 

 5 are Upper Eocene f Similar beds, holding the same stratigraphical 

 relation to the Green River Group as these, outcrop in Dr. White's dis- 

 trict. He will discuss the question of their age more at length in con- 

 nection with the evidence furnished by paleontology. 



GREEN RIVER GROUP. 



The white shales mark the beds of the Green River group all along 

 the Book Cliffs. They consist of indurated, argillaceous, calcareous, 

 and arenaceous shales. When broken, they are generally dark-colored 

 inside. Toward the west there are layers of green and white fissile shales. 

 At Station 20 the summit of the cliffs is a yellow sandstone, and all 

 along the divide in this neighborhood there is an oolitic limestone that 

 comes in near the summit. 



At the Cliff Spring the shales contain fossils in at least two different 

 layers. 



The following is the general section : 

 Top. Feet. 



1. Sandstones, limestones, and shales • 40 



2. Argillaceous shales, dark colored, containing fossils No. 1-- ) 



3. Thin white shales, probably calcareous and argillaceous... > 133 



4. Dark argillaceous shales, containing fossils No. 2 3 



5. White arenaceous and argillaceous shales to base of cliff. 



The angle of dip is about 4°, and the inclination is a little east of 

 north. 



The fossils from layer 2 are— 

 Planer a Ungeri, Beer. 

 Planera long>foUa, Lesqx. 



