58 G. R. Mansfield — Trias sic and 



get, which he correlated with King's Triassic, doubtless 

 correspond in the main with Peale's "red beds," for in 

 the Park City district, as in the region of Peale's studies, 

 the red bed formations are overlain by strata contain- 

 ing marine Jurassic fossils. Thus the stratigraphic 

 limits of the Triassic system in the Park City district 

 and in southeastern Idaho appear to be essentially the 

 same. 



The Woodside in the Park City district is chiefly a 

 red shale without fossils, and about 1,180 feet thick. The 

 Meekoceras fauna does not appear to be present in the 

 Thaynes there, the boundary between the two forma- 

 tions being indicated by the change from the shaly, non- 

 fossiliferous beds below to the sandy, calcareous and 

 fossiliferous beds above. The Thaynes formation is 

 1,190 feet thick. The Ankareh is also distinguished from 

 the Thaynes on lithologic grounds by the change from 

 the calcareous beds below to the siliceous beds above. 

 The Ankareh is composed mainly of red shales that in 

 places are sandy through considerable thicknesses. It 

 includes a number of well-marked beds of coarse gray 

 sandstone 20-55 feet thick and at the base lies a coarse 

 massive sandstone that immediately overlies a thin lime- 

 stone. A few fossiliferous grayish-blue limestones are 

 intercalated in the formation, apparently 200 feet or 

 more above the base. The thickness of the formation is 

 1,150 feet and the top is defined by the massive white 

 sandstone of the overlying Nugget, which is 500 feet 

 thick and includes with the sandstones intercalated 

 reddish shales. 



Southwestern Wyoming. — In his report on southwest- 

 ern Wyoming, Yeatch distinguished the Woodside and 

 Thaynes formations and correlated them with the 

 "Permo-Carboniferous." The red beds above the 

 Thaynes were all grouped by him in a single formation, 

 the Nugget, which is overlain by the marine Jurassic 

 Twin Creek formation. 9 Veatch's Nugget consists of a 

 lower, brightly colored, red bed member, 600 feet thick, 

 correlated by Boutwell with his Ankareh 10 , and an upper 

 member, 1,300 feet thick, composed of thin-bedded, light 

 colored sandstones, light yellow on fresh fractures but 



9 Veatch, A. C. : Geography and geology of a portion of southwestern 

 Wyoming, U. S. Geol. Survey, Prof. Paper No. 56, pp. 50-56, 1907. 



10 Boutwell, op. cit. p. 59. 



