LOGAN: FREEZE-OUT HILLS OF WYOMING. Ill 



hard and soft layers has produced a number of terrace-like ledges 

 which rise one above the other between the lowermost Red Beds and 

 the Dakota at the summit. 



In many places the topograpliy approaches the Bad Lands type. 

 The characteristic absence of vegetation of the Bad Lands is saved 

 here to a limited extent by the presence, on the lower levels, of 

 springs of water which irrigate the creek valleys. On the slopes, 

 however, very little vegetation grows, but the dip of the strata com- 

 bined with the thickness of the hard layers serves to produce the 

 shelving rather than the sharjj-crested form of topography which is so 

 common in the Bad Lands. 



Streams which have worked against the face of the monocline 

 from the west have carved out broad, amphitheater-like basins. Those 

 streams which flow toward the east have cut down through the hard 

 strata of the Dakota and carved out similar basins in the softer strata 

 of the underlying beds. The courses of these streams are marked 

 through the Dakota by narrow, tortuous defiles or canons. 



The basal portion of the hills is formed by the Red Beds, while the 

 main body of the hills is formed by the Jurassic and Atlantasaurus 

 Beds. The hills are capped, usually, with a hard stratum of Dakota 

 sandstone. This sandstone, broken into huge blocks by the sapping 

 action of erosion, lies scattered upon the slopes. The soft clays under- 

 lying are first cut away by the action of the falling water, and the 

 sandstones, being undermined, are broken ofp by their own weight and 

 roll down the slopes of the hills. In some places the Jura is, by this 

 means, concealed, although on the whole the exposures are very per- 

 fect. 



STRATIGRAPHY. 



The Red Beds. The oldest rocks recognized in the Freeze-out Hills 

 are the Carboniferous. They occupy the center of the anticline and are 

 Dverlain by the Red Beds, which are composed of sandstones and red- 

 jiish arenaceous clays, enclosing here and there lenticular masses of 

 gypsum or gypsiferous clays. These beds are seemingly devoid of 

 fossils, and are apparently conformable with the overlying Jurassic 

 beds, of unquestionable marine deposition. The brilliant colors of 

 uhe Red Beds, blended in places with the green of the vegetation and 

 aluish clay of the Jura, produce in the hills a series of views remark- 

 iible alike for their beauty and brilliancy. At a point on the Dyer 

 'anch the following stratigraphical conditions of the contact between 

 :he Red Beds and the Jura were noticed : 



1. Base, near top of Red Beds, reddish clay 2 ft.+ 



2. White, indurated sandstone 4 in. 



3. Clay, light red. . . 5 " 



•> 4. White sandstone with reddish tinge . . 1 " 



