Jurassic Formations in 8. E. Idaho, etc. 59 



weathering dark brown, that form rngged topography 

 with characteristic dark brown slopes. 



It now appears that the Thaynes and Woodside of 

 southwestern Wyoming, like the formations of the same 

 names in the Park City district, should be considered 

 Triassic and that the stratigraphic limits of the Triassic 

 system in southwestern Wyoming are essentially the 

 same as in southeastern Idaho. 



Earlier ivork, southeastern Idaho. — The interpreta- 

 tions of Boutwell and Veatch were carried northward 

 into southeastern Idaho by Gale and Richards 11 and 

 later by Richards and Mansfield, 12 with such adaptations 

 as were required by the somewhat changed stratigraphic 

 conditions. The Woodside shale was found to be thicker, 

 more calcareous, locally meriting the designation lime- 

 stone, not red colored but olive drab or yellow and with 

 abundant fossils. The Thaynes formation also was 

 thicker, and sufficiently calcareous to be called a lime- 

 stone. In addition to the "Permo-Carboniferous" 

 faunas found in Wyoming and in the Park City district, 

 numerous ammonites were found and the Meekoceras 

 zone, or lowest ammonite horizon, was selected to mark 

 the base of the formation. The term Ankareh shale was 

 applied to a series of maroon, chocolate, and reddish 

 shales with some sandy and limy strata lying above the 

 massive limestones of the upper Thaynes and including 

 at its top another massive limestone. The Nugget sand- 

 stone was marked by the occurrence in some parts of the 

 area studied of beds of pure white and conglomeratic 

 sandstone near the base. The formation included beds 

 of red sandy shales and in some areas there was an 

 upper division of several hundred feet of white sand- 

 stone. The thickness assigned to the Ankareh was 670 

 feet and to the Nugget 1,900 feet. The effect of this 

 adaptation of Park City terms was the downward exten- 

 sion of Boutwell 's term Nugget and the restriction of his 

 term Ankareh. 



11 Gale, H. S. : Geology of the copper deposits near Montpelier, Bear, 

 Lake Co., Idaho, U. S. Geol. Survey, Bull. 430, pp. 112-121, 1910. 



Gale, H. S. and Kichards, E. W. : Preliminary report on the phosphate 

 deposits in southeastern Idaho and adjacent parts of Wyoming and Utah, 

 U. S. Geol. Survey, Bull. 430, pp. 457-535, 1910. 



12 Kichards, R. W. and Mansfield, G. E. : Preliminary report on a portion 

 of the Idaho phosphate reserve, U. S. Geol. Survey, Bull. 470, pp. 371-439, 

 1911; Geology of the phosphate deposits northeast of Georgetown, Idaho: 

 U. S. Geol. Survey, Bull. 577, 1914. 



