HENRY'S FORK BASIN. 261 



series. Some biiff and reddish sandstones carrying- fresh-water fossils, 

 which are exposed, dipping 25^ north, a few hundred yards north of Dead- 

 man's Spring in the Henry's Fork Basin, have also been referred to this 

 group. They are overlaid, a little to the north, by white calcareous beds 

 carrying numerous Melania, and again by a considerable thickness of shaly 

 beds with thin sandstones, which may represent the Green River series at 

 this point. 



Henry's Fork Basin. — While along the higher northern flanks of the 

 ran^e thus far described, the upturned beds of the conformable series above 

 the Carboniferous are still almost completely concealed by the overlying 

 Tertiaries, in the vicinity of Green Rivfer, the region bordering the range 

 on either side has been extensively denuded of its Tertiary covering, and 

 the upturned Mesozoic beds exposed, forming flanking monoclinal ridges, 

 parallel with the strike, and separated by valleys of erosion. ■ On the north 

 lies the longitudinal depression called Henry's Fork Basin, which forms a 

 long, narrow valley extending 15 miles in either direction, east and west, 

 from Green River, with a width of about 3 miles, and whose average level 

 is about 300 feet below the centre of the Bridger Basin proper. The still 

 more extensive region of denudation on the south, called the Ashley Creek 

 Basin, will be described later. 



In the western portion of this basin. Quaternary accumulations sepa- 

 rate the outcrops of the Cretaceous rocks, and obscure the outlines of the 

 overlying Tertiaries. Near Deadman's Spring were found low ridges show- 

 ing outcrops of a few hundred feet of loose yellow and white sandstone, in 

 which is a, bed of soft, yellow, fossiliferous limestone, striking east 20° 

 south, with a dip of 60° north, whose general character relates it to the 

 Colorado group of the Cretaceous, although the fossils obtained were too 

 imperfect for specific identification. 



South of this spring is a steep, narrow hill, or ridge, overlooking the 

 gorge -like valley of Sheep Creek, composed of highly- metamorphosed 

 sand-rocks, at times quite quartzitic, and standing at an angle of 50° 

 north, which have been considered to belong to the Dakota group, since, 

 apparently underlying them, at the eastern base of the ridge were found 

 outcrops of calcareous shales, highly fossiliferous, and carrying character- 



