62 GEOLOGICAL SURVEY OF THE TERRITORIES. 



viding line between the triassic and carboniferous "beds. It rises 'to the 

 height of one thousand three hundred feet above the bed of Green 

 Eiver, which runs along its western base. Below the sandstones, well 

 shown in the Green Eiver canon, is a considerable thickness of the 

 brick-red arenaceous clays which I have so often described in former 

 reports as characteristic of the triassic period in other portions of the 

 West. These red beds pass down into a series of rather variegated aren- 

 aceous clays, with thin beds of sandstone and one or two beds of bluish 

 siliceous limestone. The river sometimes flows for a short distance be- 

 tween the ridges, inclining in the same direction, or, as I have termed it, 

 a monoclinal rift ; then it cuts its way directly through a ridge, forming 

 a narrow channel, with high vertical walls on either side ; then making 

 a flexure and taking a monoclinal valley again. I do not see that the 

 waters made any difference in their course, whether they flow through a 

 valley originally prepared for them or cut their way through ridges at 

 right angles. The next ridge to the southwest of the triassic one is 

 composed of limestones and calcareous sandstones of carboniferous age. 

 These rocks in the aggregate really form but one of the ridges of up- 

 heaval, yet it is separated into numerous fragments, but without any dis- 

 tinct and continuous valley of separation, as between it and the triassic 

 ridges. Then comes a series of ridges, of purplish sandstone and quartz- 

 ites, reaching to the snow-covered axis of the range. The southwest ab- 

 rupt face of the triassic ridges, at the entrance of Green Eiver into the 

 canon, exhibits a remarkable example of the flexures of the layers, all 

 the triassic and Jurassic beds forming a bow or arch. Pictorial sections 

 were made of all the ridges, their surface, forms, inclination, and any 

 local peculiarities. These are intended to be engraved for the final 

 reports, and then my descriptions of this most interesting geological 

 region will become more clear. From the summit of the triassic ridge, 

 one thousand three hundred feet above the valley of Henry's Fork, we were 

 able to gather within the limits of our vision a most interesting group 

 of geological facts. This ridge is very tortuous in its outline, but its true 

 trend is about southwest and northeast, parallel with the axis of the Uinta 

 range. The angle or dip varies in different localities, but it is usually 20° 

 to 30°. Taken at different points the strike of this ridge varies from east 

 to west by way of north. At the junction of Henry's Fork with Green 

 Eiver the latter stream flows nearly east, yet it passes through this 

 nearly at right angles. From the summit one can pass the eye over the 

 upturned edges of an almost endless series of ridges across a rugged 

 and picturesque surface. Far to the south the main range of the Uin- 

 tas cuts off the view, while in the interval the ridges of sandstone and 

 quartzite, with the usual thick growth of pines, rise like steps to the 

 axis. Between the sandstones and the triassic ridge we look across 

 the steep, jagged ridges of carboniferous limestones, inclining at various 

 angles from 10° to 25°. 



Not unfrequently, along the sides of the river where the channel passes 

 through the ridges at right angles, the strata reveal very graceful curves 

 or arches, as they pass down beneath the more recent beds. Looking 

 west we can see how these ridges connect with the Uinta Mountains, 

 and that without doubt all the northern slope of the range from Bear 

 Eiver was once as rugged and bristled with as sharp ridges as this portion 

 on Green Eiver. 



We thus have some standard by which to estimate the extent of the 

 erosion that must have occurred. The eye can run along the sandstone 

 and quartzite ridges, and connect them without interruption far west 

 toward the Wasatch range. The ridge of carboniferous limestone which 



