76 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



separation can be made. The coal deposits of this region were re- 

 ferred to the Laramie by the earlier observers ; the later observers 

 have proved that they in the Pierre. 



Laramie coals are important in the Green River Basin of south- 

 western Wyoming. The Cretaceous section in the outlying coal field 

 of Coalville in northeastern Utah has on top 2,500 feet of mostly 

 sandy beds, with leaves and fresh-water shells, but no coal. This 

 rests on 1,650 feet of sandy beds with marine fossils.^^ At about 

 30 miles northeast, one reaches the Laramie area of Uinta County, 

 Wyoming, where the Laramie, according to Knight and Veatch,^* is 

 more than 5,000 feet thick in the southern part of the county. 

 There, as in the Coalville field, one is near the western border of 

 deposition and the formations are thick. Schultz found only 2,800 

 feet remaining in the northern part of the county. The lower por- 

 tion of the column for several hundred feet contains marine fossils 

 and it must be referred to the Fox Hills ; but Laramie leaves are 

 ■ abundant in the higher deposits. The Tertiary coals of Evanston 

 overlie the Laramie uncomformably. Coal seams are numerous in 

 the Laramie and at times they are workable, but the thicker seams 

 of the Tertiary render them unimportant. 



The Rock Springs coal field in Sweetwater County is about 50 

 miles farther east, only Tertiary deposits being at the surface in 

 the intervening space. Schultz"'^ gives the thickness of Laramie as 

 3,900 to 1,500 feet, the variation being due to extent of erosion. 

 The lower part of the section is clearly Fox Hills ; the Laramie beds 

 are sands and clays with little coal. The marine sandy beds persist 

 eastwardly and the Laramie rocks retain their features, finer in 

 grain, more argillaceous and without important coal beds. In 

 southern Carbon County, Ball and Stebinger^*' find an extreme thick- 

 ness of 4,000 feet, but the formation thins away southward. The 

 lower part of the column for about 400 feet must be assigned to the 



23 C. H. Wegemann, Bull. 58i-£, 1915, p. 161. 



2* W. C. Knight, " Southern Uinta County, Wyoming," Bull. Gcol. Soc. 

 Amer., Vol. 13, 1902, pp. 542-544; A. C. Veatch, Bull. 285, 1906, p. 2i2>2>', A. R. 

 Schultz, Bull. 316, 1907, p. 217. 



35 A. R. Schultz, Bull. 341, 1909, p. 259; Bull. 381, 1910, pp. 223, 227. 



36 M. W. Ball and E. Stebinger, Bull. 341, 246, 253 ; Bull. 381, pp. 190, 

 193, 204. 



