ENDLicH.j GREEN RIVER GROUP, 83 



I am opposed, however, for many reasons, to an explanation that would, 

 if correct, necessarily be corroborated by other facts, the existence of 

 Avhich we nowhere observe. I have not had an opportunity to study 

 the localities which Professor Powell has examined. It is therefore not 

 my place to enter into any discussion upon a question of which I am 

 personally acquainted with but one side. 



Proceeding^ westward from this area we reach the divide between Pte- 

 ce-ance and Douglas Creeks. Upon this a number of stations are located, 

 some of them being the most prominent within the district. On the 

 east side of this divide the narrow ridges, separated by steep caiions, 

 gently slope toward Pte-ce-ance. Within a horizontal distance of twenty 

 miles these ridges fall approximately 1,800 feet, retaining a very even 

 angle of slope, however. West of the divide the slope is decidedly pre- 

 cipitous, forming nearly vertical walls from 1,200 to 2,200 feet in height. 

 On the top of the divide we find that the elevation is quite uniform. 

 Station 11 is 9,035 feet above sea-level, while Station 18, seventeen miles 

 farther north, is 8,704 feet high. Continuing along this dividing ridge we 

 approach White River, and there find that it breaks up into a series of 

 radiating ridges which lead down to the stream. In the valley of Doug- 

 las Creek we tind Wasatch beds, but avscending to the divide west of it 

 are soon within the Green Eiver area again. From the crest of the Book 

 Cliffs northward we pass over the lower portion belonging to this group, 

 until, within about fifteen miles of White River, we meet with the up- 

 per sandstones. Here the general configuration of the country becomes 

 more varied. The ridges are no longer so regular both in shape and 

 distribution, and the canons do not show the same uniform features as 

 farther east. Erosion and atmospheric agents violently attack the 

 sandstone, and it soon yields to the combined influence, producing very 

 unique orographic details. Lithologically the sandstones can readily 

 be distinguished from the older shaly beds of the same group, but a 

 classiticatory separation of the two seems at present certainly ill ad- 

 vised. 



Stratigraphically the Green River Group in our district is remarka- 

 bly simple. Its strata partake to a slight extent of the flexures extend- 

 ing southward from the northern more disturbed district, but their 

 effect is soon lost, and the former resume their normal position. As 

 such, a slight dip, varying from 1° to 0° a little west of north may be 

 regarded. It is noticeable wherever the strata are exposed, and only 

 slight variations of the angle were observed. The most prominent of 

 these was found south of the Station-40 Group, where the di]) first dimin- 

 ished to zero, and as we neared White River became a southeasterly, 

 and farther west a southwesterly one. Both upper and lower groups 

 are perfectly conformable in this. 



Geognostically and lithologically speaking, we can distinguish the 

 two groups of Powell very readily. While the eastern two-thirds of 

 the Green River area are composed entirely of the shales, the western 

 third contains the younger sandstones. These shales generally show 

 very light shades of color upon exposure, which alternate with narrow, 

 dark bands, thus producing a laminated appearance of the steep bluffs 

 on the faces of which they are visible. Grey, yellowish, and white col- 

 ors predominate. Subordinate beds of sandstone occur, distributed 

 throughout the shales, but are then so highly argillaceous, that they 

 produce no difference in the general fades. Darker bands are usu- 

 ally composed of harder shales. All of them weather, eventually, 

 into thin, chip-like fragments, coated with a mealy clay, the result of de- 

 composition. When freshly broken, the lamination is noticed to be very 



