EAST FOEK OF DUCHESNE. 303 



ley above was not explored; but from Point Carbon, the culminating point 

 of its western ridge, it was possible to distinguish the Upper Coal-Measure 

 limestones forming the hills on its eastern border, with dips varying from 

 27°, near the lower end of the spur, to 14° near its head. East of this gate- 

 way, remnants of Tertiary beds, dipping only 2° south, are seen high up on 

 the spurs, about 2,000 feet above the bed of the stream. 



The valley of the next stream to the west, the east branch of the 

 Duchesne Fork, presents the best and most continuous section of any of 

 those west of the Ashley. Like Antero Canon, its upper course runs par- 

 tially with the strike of the beds, but below the bend, at Beaver Lake, it . 

 crosses them almost at right angles. Below its deeper portion, a moraine 

 ridge covers the Tertiary beds of the eastern bank, as was seen to be the 

 case at the eastern branch, of Lake Fork, and the general shape of the 

 canon is glacial, though the height of these moraine ridges above its pres- 

 ent bottom shows, in the absence of canon- within-canon structure, the work 

 done by post-Glacial erosion. 



On the western wall of the canon are the best exposures found, the 

 eastern slopes being broken and covered by ddbris below the bend. The 

 beds here dip 25° to 30° south, and strike a little north of west. Those 

 recognized going up the canon were, first, in the saddle above the flat- 

 topped Tertiary hill at the lower end of this western ridge, a few outcrops 

 of gray sandstones, which were referred to the Dakota Cretaceous ; next, 

 in a short side-ravine, evidently washed out of clayey beds, irregular out- 

 crops of light-colored limestones and whitish calcareous shales, in which 

 were found a few remains of Pentacrinus asteriscus, sufiicient to designate 

 their horizon as Jurassic. A short distance beyond these is the prominent 

 cross-bedded white massive sandstone of the Triassic formation, 600 to 800 

 feet in thickness, underlaid by a yellowish sandstone 200 to 300 feet thick ; 

 next, 500 feet of pinkish-red sandstone, having at its base a thin bed, less 

 than a foot thick, of greenish-white limestone, included in shaly beds, with 

 500 feet of deep-red sandstone beds forming the base of the series. Analy- 

 ses were made of characteristic specimens from these beds by Mr. B. E. 

 Brewster, with the following result. From the greenish-white limestone, a 



