266 DESCRIPTIVE GEOLOGY. 



Tertiary benches. Here along the present bottom of the stream, sunk 

 some 40 or 50 feet below the older and wider stream-bottom, are outcrops 

 of white friable sandstones, with indications of coal seams, standing at an 

 angle of 70° north, and striking east and west, which must belong to the 

 Laramie group. 



On the surface of the triangular bench-country, included between the 

 course of Henry's Fork below the gap and Green River, are seen numerous 

 outcrops of sandstones of the Fox Hill group, running east and west, with 

 an average dip of 45° north, while, on the eastern bluff-faces of the bench- 

 country, where a point formed by these sandstones makes out, the under- 

 lying clays of the Colorado group can be distinguished, though, in general 

 throughout this basin, as elsewhere, the easily-disintegrating character of 

 their beds renders recognizable outcrops rare, and their presence is proved 

 rather by induction than by actual observation. 



The northern boundary of the valley, between these streams is formed, 

 as already mentioned, by striped pinkish gravel and sandstone beds of the 

 Vermillion Creek Eocene, dipping about 25° north, overtopped farther 

 back by the buff calcareous beds of the lower Green River group, which 

 are best exposed in the gap of Green River at its entrance into the valley. 



East of Green River, the prominent feature of the valley is formed by 

 a peculiar double-crested ridge, called Bighorn Ridge, from the animals of 

 this name, which frequent its precipitous sides, bare of vegetation with the 

 exception of a few hardy junipers and pines growing on the very faces of 

 the rock. It is formed of the coarse, gray sandstones of the Fox Hill Cre- 

 taceous, dipping 45° to the north, and rises some 500 or 600 feet above the 

 valley, extending with remarkable regularity from the Green River to the 

 hills which form the watershed of Red Creek, a distance of 15 miles, witli 

 only a single break in its crests made by the narrow gorge of a stream dry 

 in summer. 



North of the Bighorn Ridge, the red argillaceous sandstones and 

 gravel beds of the Vermillion Creek series are again recognized, dipping 25° 

 north, while the bluff line bounding the valley on the north is formed by 

 the buff calcareous sandstones of the Green River group, dipping only 5° to 

 10^ north, which would not necessarily prove an unconformity, as there is 



