28 Cincinnati Society of Natural History. 



Theo. B. Comstock* found the Jurassic limestones outcropping in 

 many places, in the Wind river country, particularl}' in the neighbor- 

 hood of the mountains, upon both sides of the plateau, and having a 

 thickness of about 1,000 feet. 



And Prof. E. D. Copef described from the Trias of the Rocky Moun- 

 tains, in New Mexico, Typothorax coccinaruyn. 



In 1876, Prof. J. W. Powell J separated the Jurassic and Triassic 

 rocks of the Plateau Province of the west in descending order, as fol- 

 lows — 



1. Flaming Gorge Group, . . . . • 1200 feet. 



2. White Cliff Group, 1100 " 



3. Vermilion Cliff Group, .... 1100 " 



4. Shinarump Group, ...... 1800 " 



The Flaming Gorge Group is of Jurassic age, the other three are 

 situated above the carboniferous, but whether the}" should be referred 

 to the Jurassic or the Triassic has not' been determined. 



The Flaming Gorge Group consists of bad-land sandstones, some- 

 times argillaceous "^ith much g3q)sum, massive sandstones and lime- 

 stones. A bed of limestone at the base is from 10 to 200 feet in thick 

 ness. In Southern Utah it caps an extensive escarpment which is 

 called the white cliff limestone. It can be well studied at Flaming 

 > Gorge, the t3^pe locality. Commencing at tlie conglomerate of the 

 Henry's Fork Group, and going southward, you pass over the upturned 

 edges of the beds, crossing the bad-land sandstones, then the mid- 

 group limestones, and then the bad-land indurated sandstones until the 

 limestone is reached. The bad-laud sandstones both above and below 

 the mid group limestone are of fresh water origin. 



The White Cliff Group is a massive, obliquely laminated sandstone, 

 often a beautiful white or golden color, sometimes red. In a few 

 places there are heavily bedded sandstones. The typical locality is in 

 Southern Utah. The Paria, Kanab, and Rio Virgen with their many 

 tributaries that head in the Pink Cliffs above and to the north, have 

 cut many canons and canon valley's through these escarpments plainly 

 revealing the structural geology a,nd stratigraphy. 



The Vermilion Cliff Group consists of massive sandstones with fer- 

 ruginous layers, and often with thin, irregular beds of cherty lime- 

 stone ; the massive beds sometimes broken into thinner strata. It is 

 also well exposed in the Paria, Kanab, Rio Virgen and their tributa- 



* Jones' Report on Northwestern Wyoming, etc, 



t Proc. Acad. Nat. Sci. 



X Geo. of Uinta Mountains. 



