292 DESCRIPTIVE GEOLOGY. 



side of the mouth of the canon are monoclinal depressions, forming low sad- 

 dles between the beds of the various creeks, and showing few rock-exposures, 

 the surface being covered by soil and ddbris. This gap of several hundred 

 feet is supposed to be occupied by the green and white clayey beds observed 

 at the base of the Triassic formation in Flaming Gorge and Vermillion Creek, 

 and which were assigned to the Permo-Carboniferous. 



In the first line of ridges parallel to the steep slopes of the BelleropJion 

 limestone, the escarpments of the northern face are formed of about 500 feet 

 of coarse, massively-bedded sandstones of a deep-red color, with numerous 

 intercalated clay seams, more or less impregnated with mineral salts, in which 

 chloride of sodium appears to predominate. In the lower portion are thinly- 

 bedded sandstones, which are remarkable for their well-defined ripple-marks. 

 At the base of these red sandstone cliffs, west of the mouth of Geode 

 Canon, on the divide between the tAvo forks of Ashley Creek, was found an 

 exposure of about 30 feet of solid white gypsum, overlaid by red and white 

 clays. This gypsum is remarkably pure, containing 79.014 per cent, of sul- 

 phate of lime and 20.93 per cent, of water. Its beds are very massive on 

 the exposed surfaces, and resemble a very fine-grained white marble, with 

 a cloudy veining running through the mass. Doubtless, if opened by 

 quarrying, these beds might furnish a very fair quality of alabaster. The 

 red sandstone cliffs are capped by beds of harder compact grayish sandstone, 

 above which a second line of cliffs is formed of 300 to 400 feet of lighter- 

 colored red or pinkish sandstones, with a gap of 100 feet or more between 

 this and the deep-red bed, representing probably some clayey or shaly 

 beds. These pink-red sandstones are capped by thin beds of flaggy sand- 

 stones, and a short line of cliffs is formed of 200 feet of yellowish sandstones, 

 above which are heavy, white, cross-bedded, massive sandstones from 500 to 

 600 feet in thickness. These correspond to the massive buff and white 

 sandstones already observed in former sections, and are noticeable for the 

 persistency of the cross-bedding, which sometimes forms an angle of 30° 

 with the true planes of stratification. We have thus a thickness of about 

 2,000 to 2,500 feet of Triassic sandstones, in which, however, the thin lime- 

 stone seam noticed in other sections was not observed. 



To the south of the white sandstone ridges is an interval of clayey val- 



