BOS DESCKIPTIVE GEOLOGY. 



sandstone, witli alternate beds of reddish arenaceous material, not unlike 

 the beds of the Vermillion Creek series on the Aspen Plateau ; in all a 

 thickness of perhaps 500 feet. These same Tertiary beds form the crest 

 of the Wonsits Eidffe as far as Obelisk Plateau., Some distance down the 

 Green River could be distinguished red and chocolate-colored beds lying 

 nearly horizontal, while those of the White River Valley, from which Pro- 

 fessor Marsh's fossils were obtained, are represented as green and ash-colored 

 argillaceous beds, eroded into bad-land forms, which might seem to be an 

 unconformable and later series than the upturned conglomerates and sand- 

 stones ; this non-conformity is, however, merely conjectural, and not sup- 

 ported by any actual observations. 



At the Obelisk Plateau, as well as on the ridge east of Antero Canon, 

 the Tertiary beds are still capped by fragments of Wyoming Conglomerate, 

 but of the character of the underlying beds, owing to their friable natm^e 

 and consequent covering of loose material on the slopes, little could be seen 

 in these higher ridges. The low terrace-ridges, which separate the valleys 

 of the streams flowing- into the Uinta, seem largely composed, however, 

 of coarse sandstones and gravelly beds, of a general reddish color, having 

 few strata of a consistency to afford good outcrops. From the Ute Fork: 

 westward, the benches are covered near the hills by moraine ridges extend- 

 ing out into the valley from the canon-mouth of the principal streams, and 

 reaching a height, in some cases, of several hundred feet. Between the 

 Ute and Lake Forks were observed several exposures, showing from 200 

 to 500 feet of coarse red and yellowish sandstones, while the calculated 

 thickness of Tertiary ridges observed would give a development of 2,000 

 to 3,000 feet of Tertiary beds above the present 'average level of the 

 streams. The Tertiaries are, in general, much better exposed in the lower 

 portions of the valley toward the Uinta River, but time did not permit of 

 any extended examination in that direction. The most considerable body 

 of Tertiary beds on this map is that between the forks of the Duchesne, near 

 the western limits, where they form a flat-topped hill, capped by beds of the 

 Wyoming Conglomerate. The thickness here is, as already observed, be- 

 tween 2,000 and 3,000 feet, the beds lying practically horizontal. By refer- 

 ence to Map III, it will be seen that the Tertiaries extend westward nearly 



