KEGION EAST OF TDE UINTA EANGE. 279 



Yampa Peak is an isolated mountain-mass, which may be considered 

 to be, as it were, an eastern extension of the great terrestrial wave which 

 uplifted the Uinta Kange. It is composed, of the drab limestones of the 

 Upper Goal-Measures; its structure being that of a double anticlinal, or 

 quaquaversal, whose longer axis trends a little east of north. The Yampa 

 River has cut a canon, about half a mile in length, thi'ough the northern point 

 of this ridge, exposing a section of about 1,500 feet of strata, mostly of lime- 

 stone, with some sandstone. In the bluffs of the north side of this canon, 

 about the centre of the anticlinal, a slight north and south fault is observed, 

 in which the downthrow is on the west. Near the summit of the peak, 

 brownish-red quartzitic sandstones are found exposed in the deeper ravines, 

 and on the steeper slopes, though a drab limestone caps the very summit. 

 These were supposed to represent the Weber Quartzite group; but, as no 

 great thickness was observed, they may possibly represent a red sandstone, 

 which has been noticed in the Vermillion Creek section, included in the 

 limestone beds. The strata on the east and south, dip much more steeply 

 than on the west and north. No fossils were found on this peak, but 

 the lithological character of its beds leaved no doubt as to their age. The 

 white horizontal Tertiaries of Brown's Park cover the flanks of the peak on 

 every side, so that no younger upturned beds were observed, though 

 portions of the Permo-Carboniferous have been indicated on the map, to 

 better illustrate the structure. The peak is connected with the hills of the 

 White River divide by a Tertiary ridge, at the southern end of which were 

 found sandstones dipping 31° south, with an easterly strike, which, from 

 their position under the coal-rocks, were considered to represent the upper 

 portion of the Fox Hill group. 



Coal Mountaiuj on the White River divide, south of Yampa Peak, is 

 formed of soft, heavy-bedded sandstones of the Laramie group, which 

 abound in coal seams. Six of these were passed in the ascent of the peak, 

 and near the summit was found a 6-inch seam of iron-ore. The structure of 

 the ridge, as seen from this point, is to the eastward that of a gentle anti- 

 clinal, while on Coal Mountain itself the rocks dip 5° to the south, and to 

 the westward the axis of the anticlinal follows the higher part of the ridge, 

 dipping 10° southward on their southern slopes, while a synclinal fold is 



