Jurassic Formations in 8. E. Idaho, etc. 55 



Stratigraphic correlation. — In figures 2 and 3 a tenta- 

 tive correlation is attempted of the stratigraphic units 

 employed by different authors in the discussion of Tri- 

 assic and Jurassic formations in northeastern Utah, 

 southeastern Idaho, and southwestern Wyoming^ 



Schultz, whose field work in western Wyoming was 

 completed before the classification here presented was 

 made, uses the name Ankareh in several publications 4 

 for strata corresponding with the Ankareh of Boutwell 

 (fig. 2) or with the red beds of Veatch's Nugget (fig. 3). 

 In the last two publications named he indicates an 

 unconformity at the base of the Ankareh. 



Review of Nomenclature. 



Hayden Surveys. — Although both Triassic and Juras- 

 sic rocks were recognized in southeastern Idaho by 

 the Hayden Survey parties, it was not then possible to 

 differentiate clearly the one group from the other, hence 

 both were included in the so-called " Jura-Trias. ' ' 

 Three subdivisions were recognized, namely, (1) a 

 lower series of arenaceous limestones characterized by 

 the occurrence of the fossil ammonite, Meekoceras, and 

 called the "Meekoceras beds"; (2) the red beds, a series 

 of red sandstones and shales classed with (1) as Triassic; 

 and (3) a series of limestones, shales, and sandstones 

 with Jurassic fossils. The last series was subdivided 

 into two formations. The doubt as to the nomenclature 

 was caused by the apparent intermingling of Triassic 

 and Jurassic faunas. 5 This broad grouping is still 

 applicable in a general way to the region. 



Park City district, Uutah. — In his original studies of 

 the Park City mining district Boutwell described the 

 Woodside shale and Thaynes formation. The faunal 

 content of the Thaynes was found to agree with that 

 of the "Permo-Carboniferous beds' ' of the Fortieth 

 Parallel Survey and the Woodside, almost nonfossilifer- 

 ous but lithologically related to the Thaynes, was grouped 

 with that formation rather than with the underlying Park 



4 Schultz, A. E. : Geology and geography of a portion of Lincoln County, 

 Wyoming: U. S. Geol. Survey, Bull. 543, p. 49, 1914. 



Idem: A geologic reconnaissance for phosphate and coal in southeastern 

 Idaho and western Wyoming, U. S. Geol. Survey Bull. 680, p. 25, 1918. 



Idem: Oil possibilities in and around Baxter Basin in the Rock Springs 

 uplift, Sweetwater County, Wyoming, U. S. Geol. Survey Bull. 702 (in press). 



5 Peale, A. C. : Report of the Green River Division, XL S. Geol. and Geogr. 

 Survey Terr, for 1877, pp. 621-629, 1879. 



