228 Cincinnati Society of Natural History. 



Theo. B. Corastock* found^the Jurassic limestones outcropping in 

 many places, in the Wind river country, particularly 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 coccinarum. 



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 Cliflf 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 they should be referred 

 to the Jurassic or the Triassic has not been determined. 



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

 times ai'gillaceous with much gypsum, 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 tj^pe locality. Commencing at the 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-land 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, Kauab, and Rio Virgen with their many 

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

 cut many canons and canon valleys through these escarpments plainly 

 revealing the structural geology and stratigraphy. 



The Vermilion Cliff Group consists of massive sandstones with fer- 

 ruginous layers, and often with thin, irregular beds of chertj' 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 Nortliwostern Wyoming, etc. 



t Proe. Acad. Nat. Sci. 



t Geo. of Uinta Mountains. 



