294 DESCEIPTIVE GEOLOGY. 



On the southern face of this ridge, between beds of white and yellow 

 sandstones, was found a seam of coal about 10 feet in thickness. This coal 

 was apparently of remarkably good quality, having a brilliant lustre and 

 conchoidal fracture, and was, as well as could be seen, remarkably free from 

 clay seams. Unfortunately, the specimens obtained were lost in transitu, 

 and no analysis has been made of this coal. To the south of this ridge, 

 only a few hundred feet of sandstone ridges are exposed, which rapidly 

 disappear under the clayey wash of the open valley. The average ob- 

 served dip of the beds exposed in this section is about 20° south. In 

 general, it decreases in the higher beds and those at the greater distance 

 from the axis of upheaval. To the westward of the main branch of Ashley 

 Creek, the ridges bend off more to the northwest, closing up against the 

 foot-hills of the range, and steepening somewhat in dip. At Obelisk Pla- 

 teau, which forms the highest point of the Wonsits Ridge, the upper por- 

 tions of -these beds disappear under the Tertiaries, while the Triassic beds 

 are seen to form the western faces of the canon of the west branch of 

 Ashley Creek, which runs approximately in the strike. 



On the northern face of Obelisk Plateau, an abrupt escarpment, where 

 the massive sandstone has weathered into obelisk -like shafts, or pinnacles, 

 affords the following section. The summit is composed of conglomerate 

 ddbris, obscured by surface degradation, from 150 to 200 feet below the 

 highest point. In the next 250 feet were found some conglomerates and 

 clays, with sandy shales, having somewhat of an oolitic structure, and 

 carrying Jurassic fossils, among which were recognized Gryphcea calceola, 

 already observed on Ashley Creek. The next 200 feet were hidden by 

 d^biis ; in their base were found some green and white clays, and the 

 bottom of the cliff is formed of about 500 feet of the massive white cross- 

 bedded sandstone of the Upper Trias; dipping 29° to the southwest. The 

 strike of the sandstone is here about north 65° west. To the west of this 

 hill, the country is in general covered by benches of the Tertiaries of the 

 Uinta Basin. The crest of the Wonsits Eidge apparently gives the present 

 eastern limit of these Tertiaries, no remnants of them having been discov- 

 ered within the basin east of this line. The Wyoming Conglomerate found 

 on the Ti-ra-kav Plateau was apparently deposited upon the upturned 



