VALLEY OF BUENT FORK. 259 



bert's Peak, have a slight dip 3° to 5° northward, while at a point a little 

 below the upper timber-line the dip falls off steeply into that of the lime- 

 stone ridges to the north. 



Burro Peak is formed of almost horizontal beds of quartzite, with an 

 apparent dip of 1° to the north. The steep wall of quartzite, forming the 

 northern face of the higher portion of the range from Burro Peak eastward 

 to Leidy's Peak, marking approximately the line of the main geological 

 axis, is probably a line of faulting and displacement corresponding to that 

 at the head of Smith's Fork. The range was crossed at Burro Peak and 

 again on the Indian trail to the east of Leidy's Peak ; but between these 

 points, that is, from Island Pond to the head of Burnt Fork, there is a gap 

 in our observations on the northern slope. 



At the western base of Mount Corson lies the little valley of Burnt 

 Fork, one of the tributaries of 'Henry's Fork, which is characterized by 

 an unusually broad expanse of meadow-land, dotted by little clumps of 

 pine. Toward the head of this valley may be seen low ridges, com- 

 posed of strata of dark compact earthy limestone, having a strike of 

 east 15° south, and dipping 35° to 45° north. No fossil remains were 

 found in them; but, from their position, the limestones doubtless belong 

 to the same horizon as those, which are found to the east of Mount Cor- 

 son, near Sheep Creek, carrying well-recognized Jurassic fossils. About 

 200 yards north of these are similar low ridges, showing indistinct out- 

 crops of white sand-rock, having the same strike and dip, which probably 

 represent beds of the Dakota Cretaceous. In the wooded region, at the 

 head of this valley, and yet below the flanks of the Uinta Range proper, 

 are curious ridges of bare rock, standing prominently out among the green 

 valleys, formed of massive buff sandstone, in beds over 100 feet in thick- 

 ness, in which the prevailing yellow color sometimes passes into a pink. 

 These sandstones are formed of fine pure white quartz sand, owing their 

 color to minute specks of iron oxide plentifully disseminated through their 

 mass, and belong to the upper group of the Triassic sandstones, which, as 

 will be seen later, are so characteristically exposed on the Flaming Gorge 

 Ridge. The lower deep-red sandstones of this group were not distinctly 

 traced here, owing to the covering of forest and surface ddbris, but are well 



