STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 103 



*' Pierre-Fox Hills " to designate the whole mass. Just above the 

 one persistent sandstone, Pine Ridge of Siebenthal, is a coal bed and 

 others, unimportant, are in the succeeding 560 feet of black shale; 

 but in the overlying beds no coal was found. It may be that the 

 upper part of the section, including the Pine Ridge sandstone, is 

 equivalent to Mesaverde, Lewis and Fox Hills, the coal being in the 

 Mesaverde. 



Farther west in Fremont County, north from Sweetwater, the 

 lower shales are 2,250 to 3,000 feet, increasing eastwardly, while 

 the upper division, of which erosion has spared 550 feet, has at base 

 a sandstone, 200 to 250 feet thick. Overlying this is a bed of car- 

 bonaceous shale, which occasionally contains a seam of coal. Here 

 the Mesaverde conditions are distinct for the overlying mass con- 

 sists of " sandstones, with intercalated gray shales, sandy shales and 

 coal beds." The lowest coal is 8 feet thick at 10 miles east from 

 Lander. 



The Pierre is without coal*^ in the Black Hills and is wholly 

 shale. The Sussex field at 100 miles southwest from the Black 

 Hills has, according to Wegemann, 4,650 feet of Montana rocks, of 

 which he refers the upper 700 feet to the Fox Hills. The Pierre 

 has a sandstone, 175 feet thick, at about 1,000 feet from the base 

 and, at 2,300 feet, another sandstone, the Parkman of Barton's Big- 

 horn section, 350 feet. This sandstone contains masses of petri- 

 fied wood with shells of turtles and bones of TracJiodon. Li the 

 shaly portions near the base, it has thin seams of low-grade bitumi- 

 nous coal, high in ash. Thin seams are associated in the southern 

 part of the field with another sandstone, about 300 feet above the 

 Parkman. The Pierre rocks are predominatingly shale. The fauna 

 of the Parkman sandstone, according to T. W. Stanton, is similar to 

 that of the Mesaverde in Colorado and of the Claggett in Alontana. 



The Bighorn Basin of north central Wyoming lies west from 

 the Bighorn Mountains, occupying parts of several counties and ex- 

 tending into Montana. It was examined by Washburne and Wood- 

 ruff and in part by Barton.-^ The indefinite relations of the upper 



^3 N. H. Darton, Folios 127, 12S, 1905. 



84 N. H. Darton, Prof. Paper 51, 1906, pp. 13, 58, 59; E. G. Woodruff, 

 Bull. 341, pp. 204, 208-210, 215; Bull. 381, pp. 173-175, 178; C. W. Washhurne, 

 Bull. 341, pp. 168, 172-179, 187, 195. 



