390 DESCRIPTIVE GEOLOGY. 



Tliey are directly overlaid by the red Triassic sandstones, estimated 

 here to be from 800 to 1,000 feet in thickness. The same general distinction 

 in color can be noted, as elsewhere, dividing them into a darker red series 

 below, and a lighter above, though not as distinctly as in the Uinta, where 

 the sandstones are much more loosely compacted and impure. A specimen 

 of this rock gave 94 per cent, of silica, alumina being the principal impurity, 

 and scarcely a trace of lime, while the specimen which was analyzed from 

 the Uinta Eange contained, as has been seen, 27 per cent, of carbonate of 

 lime. The bedding of these sandstones is often extremely fine, especially 

 in that portion which is quarried ; some of the heavy beds are made of a 

 finely-striped sandstone of brick-red and venetian-red color, banded with 

 pale cream-color and white stripes. Much of the whole Triassic series 

 shows remarkable cross-stratification, developing in section the arrowhead- 

 figure and' the flow-and-plunge structure. The average dip of these beds is 

 from 70° to 75° eastward. Directly over the Triassic occur lime-beds, in 

 which are found the following Jurassic fossils: 



Myoplioria lineata. 



Pinna Kingii. 



CucuUcBa Haguei. 



Myacites (Pleuromya) inconspicuus. 



Myacites (Pleuromya) suhcompressus. 



Volsella scalprum var. isonema. 



Of these, the Myoplioria lineata^ which is found in Europe in the Saint 

 Cassian beds, was obtained from the limestone directly above the red sand- 

 stones of the Triassic; the others at different horizons in the calcareous 

 shales.^ 



The lowest of these beds are quite thick, heavily bedded, and have an 

 exceedingly fine texture, not unlike the true lithographic limestone. Over 

 these, calcareous and argillaceous shales occur for a thickness of perhaps 80 

 feet, and, passing upward, are interstratified with lime-beds for some 600 feet. 

 It is impossible to estimate definitely this thickness, as the hill-spurs upon 



^ Owing to a misuuderstanding of the labels of fossils found in this caiion and in 

 that of the Upper Weber Eiver, Professor Meek, in Plate XII of his Eeport (Vol. IV), 

 has associated Carboniferous with Jurassic species. 



