298 DESCRIPTIVE GEOLOGY. 



Quartzite series, and they have not, therefore, been indicated by a distinct- 

 ive color. 



In the synclinal south of Split Mountain, the red Triassic beds are seen 

 to extend hig-h up in the re-entering valley to the eastward, almost to the 

 summit of the Yampa Plateau, in a U-shaped line of bluffs, presenting always 

 steep escarpments toward the hills, while their surface slopes approximately 

 with the dip of the beds toward the valley. On the northern slope of Section 

 Ridge, these Triassic sandstones dip only 10° to the northwest. So contin- 

 uous a ridge do they form that it was found almost impossible to cross it with 

 mules in order to reach the curved interior valley, in which are White Sul- 

 phur Springs. These springs come from strata near the base of the Triassic 

 formation, and may probably get the sulphur, which deposits freely from 

 their waters, from the same stratum in the Upper Coal-Measure series from 

 .which proceed the pyrites, already mentioned as occurring on the summit 

 of Section Ridge. The width of the outcrops, indicated on the map, at 

 the southwestern point of Section Ridge, is probably narrower than it 

 should be, since the vertical distance of our grade-curves is so great that the 

 topography here has been too much generalized to give sufficient accuracy 

 in its delineation of the sandstone ridges. It is a matter of regret to the 

 observer in this district that only a few days could be allotted to the study 

 of this unique and interesting region, for the proper illustration of which a 

 careful plane-table survey and several months' geological field-work would 

 be necessary. 



Southern Flanks of the Uinta Range. — West and south of the 

 Wonsits Ridge, away from the immediate flanks of the mountains, the 

 country is covered by the Tertiary beds of the Uinta Valley, which form 

 gently-sloping terraces and plateau ridges between tlie valleys of the prin- 

 cipal streams. In the bottoms of these valleys are broad stretches of allu- 

 vial land along the borders of the streams, while, in the bench country, near 

 the canons, through which the larger streams emerge from the mountains, are 

 long ridges of moraine material overlying the Tertiaries. It is only along 

 the steeper slopes of the mountains, and that where the streams have deeply 

 eroded the Tertiary gravel beds, that the upturned older rocks can be 

 observed. 



