STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 101 



coal throughout is inferior and the seams, for the most part, are too 

 thin to be mined. 



Beyond Rawlins and still north from the Union Pacific Railroad, 

 Veatch'^ studied the coal field of east-central Carbon County, where 

 the Pierre consists of Lewis, Mesaverde and Lower Pierre, with a 

 total thickness of almost 8,000 feet, not far from that given by 

 Smith ; but in both districts the thickness decreases greatly toward 

 the north. According to Veatch, some important coal seams are 

 present in the lower part of the Lewis, evidently those belonging to 

 the highest zone of Smith. Seams in the middle zone of the Mesa- 

 verde occasionally become thick enough for mining, but they are 

 irregular and not persistent. The southern part of Carbon County, 

 where the subdivisions of the Pierre are as in the northern part of 

 the county, was studied by Ball and Stebinger."^ The thickness of 

 Lewis and JMesaverde decreases eastwardly, becoming 1,600 and 

 2,000 feet. The Lewis has no coal. The Mesaverde still has the 

 two limiting sandstones with the middle shale and sandstone mem- 

 ber. The basal sandstone is white gray and brown, cross-bedded 

 and, in the eastern part of the district, contains a limestone, 25 feet 

 thick. The top sandstone is less distinctly cross-bedded and the 

 layers are thinner. No workable coal seams were seen in the sand- 

 stone members, at the north, but the number and thickness of those 

 in the upper sandstone increase toward the south. Some important 

 seams are in the middle member near Rawlins, but they disappear 

 toward the northeast. The coal is hard and bituminous. The sand- 

 stones of this member are irregular and the coal seams appear to be 

 overlapping lenses. 



The Yampa coal field, in Routt County of Colorado, is the ex- 

 treme southeast part of the basin. One can recognize in the sec- 

 tion by Fennemann and Gale,-" Lewis, Mesaverde and the lower 

 shales, Mesaverde being ^Middle Pierre ; the relations are more 

 allied to those of the western than to those of the northern part of 

 the basin. There are three coal groups, which in some portions of 

 the field are in a vertical space of 2,000 feet, the lowest being about 



"- A. C. Veatch, Bull. 316, 1907, pp. 244-366. 



■9 M. W. Ball and E. Stebinger, Bull. 341, pp. 243-355; Bull. 381, pp. 

 186-213. 



s'J N. M. Fenneman and H. S. Gale, Bull. 285, 1906, pp. 226-239. 



PROC. AMER. PHIL. SOC, VOL. LVI, H, MAY 23, I917. 



