296 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



River, I observed a layer of an impure limestone, with imperfect indications of fossils, 

 but I did not succeed in finding a single specimen from which to identify the forma- 

 tion. Else, the character of the strata is unchanged. 



In the northeast corner of Kamas Prairie, at the mouth of the canon of the East 

 Fork of Weber River, I noticed a gray, very compact, calcareous rock, and up that 

 stream more light-red and gray compact siliceous sandstones, some what altered by 

 metamorphic action, and sonic shaly strata. The canon follows for a long distance, 

 although not throughout, the trend of the strata, the dip of which varies between north 

 and west-northwest, and is partly very strong, 60° and 70°. Some miles up that 

 stream I found pieces of a gray altered limestone, evidently from an outcrop close by, 

 with numerous traces of organic remains. Although I could only obtain some imper- 

 fect IWtm, Ostrca, and Pentacrinus, these, taken together with all the other circum- 

 stances, leave scarcely room to doubt the Jurassic age of the formation. (See Mr. 

 Meek's report.) 



The high mountains between this point and the head of White Clay Creek, which 

 I crossed with ( Japtain Simpson and a small reconnoitering party, are covered all over 

 with soil, timber, and undergrowth, and therefore afford few data to the geologist. A 

 few red escarpments were observed at a distance near the summits of the Uintah Mount- 

 ains, of which more will be said below. On the summit of the trail, between Porter's 

 Fork and the East Fork of Weber River, T observed some large masses of white 

 granite, apparently not far out of place. 



On another reconnaissance with Captain Simpson, in the summer of 1859, from 

 Round Prairie, on the Timpanogos, to the Uintah River, I obtained a view of the con- 

 tinuation of the Weber River formations south of the Uintah Mountains, where they 

 appear to be a little differently developed, with less conglomeratic portions, although 

 the close connection between the two is evident at the first glance. The axis of the 

 Uintah Mountains bears from east to west at a right angle to the Wahsatch Mountains, 

 and although they may have a center of igneous rocks, and owe their origin to their 

 eruption, these do not appear prominently in the general outlines of the chain, and 

 besides the few blocks of granite mentioned above, I have only noticed near our trail, 

 at their junction with the Wahsatch Mountains, some of the same dioritic porphyries 

 which form the ridge west of Weber River. From north and south stratified rocks 

 cover their slopes, and rise toward the summits, where they form a crest remarkable 

 lor its horizontal outlines, with deep intervening chasms and apparently high vertical 

 walls of mostly reddish color. 



Near the pass from the heads of Coal Creek, a tributary of Timpanogos River to 

 Potts' Creek, an affluent of Duchesne Fork of the Uintah River, the ridges are' all 

 strewn with pieces of white, highly altered, compact sand-rock, but the first stratum 

 in place, just beyond the summit, is a siliceous conglomerate, followed by red sand- 

 stones and conglomerates, and red arenaceous and argillaceous shales, several hundred 

 feet thick, but not well exposed. Near the summit I also obtained some imperfect 

 Wis in a gray limestone, apparently in stiu, which, however, could not be identified 

 These red strata are apparently the same which cap the Uintah Mountains farther 

 east, and I have been doubtful whether they occupy a high or low position in the 



