278 DESCRIPTIVE GEOLOGY. 



axis, whose beds, at the same time, rise toward the south to a region beyond 

 the hmits of the map, which may represent the geological continuation to the 

 eastward of the Uinta plications. With the exception of a few specimens of 

 Ostrea, no fossils were found here. The beds have been separated, therefore, 

 in a general way, into a lower group of white, rather more heavily-bedded 

 sandstones, and an upper series of red and pinkish sandstones. No oppor- 

 tunity offered for obtaining a continuous section of these beds, but their 

 structure was easily traced by the difference of coloring of the two series. 

 The lower beds, as exposed in the deeper cuts of Williams Fork and Mill 

 Creek, the next tributary of the Yampa River to the west, have, mainly on 

 structural grounds, been included in the Fox Hill group. In the narrow 

 ridge just east of Canon Park, the rather steeply-dipping massive white 

 sandstones represent the eastern side of the Williams Fork fold. The beds 

 descend in Caiion Park, and are capped by the reddish strata of the Laramie 

 group, which rise again to the Avest of Canon Park in a gentle anticlinal, 

 descending again to the westward beyond the mouth of Mill Creek ; and 

 near the point where the river emerges- from the caiion into the alluvial 

 valley east of Yampa Peak, an upper series of beds is found containing 

 coal and scattered deposits of iron-ore, with some shale beds, which 

 resemble in lithological character those observed on the Upper Little 

 Snake River. At the mouth of the canon, the strata rise again slightly, with 

 a gentle dip to the eastward, forming a bluff face to the valle y, against 

 which its white Tertiary beds are deposited horizontally. 



To the north, these upper beds slope off gently, and disappear under the 

 rolling hills of the Vermillion Creek group between the Yampa and Little 

 Snake Rivers. To the south of the Yampa River, the strata rise again, and 

 are cut off abruptly in an east and west line of bluffs, which border the anti- 

 clinal valley of the upper part of Wilhams Fork and Mill Creek. Beyond this 

 valley, on the foot-hills of the White River divide, the other member of the 

 anticlinal is seen, the strata dipping southward into the hills. This seems to 

 be the general structure of that portion of the White River divide included 

 on the map, namely, that of the southern portion of a gentle anticlinal fold, 

 from which the northern member has been cut off by erosion, and possibly 

 also by some faulting, though no evidences of this were observed. 



