STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 119 



present in the southern part of the field, but is 5 feet 8 inches at 

 Kemmerer, where it yields a coking coal. The Carter bed is 1,300 

 feet below the Kemmerer and the Spring Valley, 1,475. The last, 

 5 to 6 feet thick, is apt to be dirty. 



The Bear River coals are occasionally thick, as much as 6 feet, 

 but the coal is so dirty as to be worthless. This formation, 2,400 

 feet on the western side of the county, is only 100 feet at the east 

 side. The Frontier coals are bituminous, of high grade, with low 

 ash and water content; the Coalville coal is subbituminous. 



The Frontier sandstone does not outcrop in the Rock Springs 

 field ; in northern Carbon County Smith saw it with all the litho- 

 logical features observed in Uinta County, but without coal. It is 

 900 feet thick in the southern part but only 500 in the northern part 

 of his district ; showing a great decrease toward the east. The Bear 

 River is only 30 feet thick, but this has some thin and worthless 

 streaks of coal. Veatch^^*' in the eastern part of the same county 

 found 400 to 800 feet of Frontier, but no coal, while the coaly 

 streaks in shales overlying the Dakota are thin and worthless. 

 Woodruff saw thin streaks of coal, 6 to 8 inches, below the middle 

 of the Colorado, in Park County of Wyoming, almost due north 

 from the Rock Springs coal field. No observer has reported the 

 occurrence of coal at the Frontier horizons at any locality in ]\Ion- 

 tana or in Alberta or anywhere east from the 109th meridian in 

 Wyoming or the io8th in Colorado, but the lowest coal horizon, that 

 resting on the Dakota, reaches to the 105th in Carbon County of 

 Wyoming and, in northern New Mexico, along the southern bor- 

 der, it is present occasionally to near the same meridian. In New 

 Mexico it extends northwardly for only a short distance. 



The Dakota. 



The Dakota or basal member of the Upper Cretaceous is a sand- 

 stone, more or less massive and locally conglomerate in the eastern 

 or Rocky Mountain region. It is often cross-bedded and some- 

 times ripple-marked. At some localities farther west it contains 

 much conglomerate. The thickness rarely exceeds 200 feet. Land 



116 E. E. Smith, Bull. 341, p. 226; A. C. Veatch, Bull. 316. p. 247; E. G. 

 Woodruff, Bull. 341, p. 203. 



