SOUTHERN FLANKS OF THE UINTA RANGE. 301 



of the lower part of this spur, little is to be seen of the structure, owing to 

 the fact that it is covered with a dense forest, and the rocks are obscured 

 by vegetation and fallen timber; the upper and barer portion to the west 

 of the three lakes, at the head of Antero Creek, is formed of the striped 

 red quartzites, which belong apparently to the upper part of the Weber 

 Quartzite group, dipping 9° southward; within them were found, however, 

 some clay beds, about 100 feet in thickness, similar to those already observed 

 on Gilbert's Peak, though their geological horizon should be considerably 

 higher than the latter. 



Eastward from this point, the almost continuous ridge forming the 

 northern face of the higher portion of the range as far as Leidy's Peak, was 

 seen to be formed of similar beds of approximately the same horizon, dip- 

 ping from 5° to 7° to the southward, with a slowly-increasing angle toward 

 the southern flanks. The basin at the head of the western branch of Ute 

 Fork, to the west of this ridge, which is one of the largest of the character- 

 istic amphitheatre-shaped basins which are found all along the crest of the 

 range, has already been mentioned in the view from Gilbert's Peak ; it is 

 surrounded by the highest peaks of the range, Emmons' Peak on the west, 

 with a ridge of scarcely less elevation, connecting it with the east and west 

 crest of which Gilbert's and Burro Peaks are the prominent points. The 

 exit to the south down the canon of the west branch of Ute Fork was found 

 impracticable for animals on account of the peculiar canon^within-caiion 

 structure common to many of the valleys of the southern slope, but 

 remarkably well developed here. The peculiarity of this structure is that 

 while the main valley is a canon-like gorge, having the characteristic 

 U-shape of glacial valleys, the present stream has cut a still narrower 

 canon in its very bottom, scarcely wider than the stream itself, whose sides 

 are perpendicular, and frequently overhanging, while its depth is in places 

 50 to 100 feet below the general level of the main valley -bottom. The 

 cutting of such canons through rocks as hard as the Weber Quartzite, is an 

 additional proof of the great amount of post-Glacial erosion which has been 

 already supposed to be necessary for the removal of such immense quanti- 

 ties of softer material from the Tertiary plains since the deposition of the 

 Wyoming Conglomerate. 



