96 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



formations. If the deposits under consideration underlie the Lewis, 

 they belong to the Pierre. 



The undifferentiated Mesaverde on the western border of Lee's 

 area consists chiefly of massive cliff-making sandstones, about 1,500 

 feet thick, containing deciduous and conifer leaves as well as 

 Sphccrinni, Physa and Goniobasis. Within 22 miles eastward, of 

 about 1,000 feet exposed, 700 feet are shales; it may be described 

 as shale with thick partings of sandstone, while near Bowie in the 

 Somerset district the shale feature becomes much more marked ; 

 but in Crested Butte district, the southeastern part of the basin, it 

 consists of sandstones separated by layers of shale. The coal seams 

 throughout are thin. 



The Paonia shales, at several horizons, are rich in fossil leaves 

 and fresh-water mollusks. The lowest coal seam, Cameo of 

 Richardson, is at 4 to 10 feet above the great sandstone at top of 

 the Bowie ; in the western part of the area studied by Lee, this coal 

 horizon seems to persist throughout the whole region. This coal is 

 double at Rollins, 3 and 11 feet with parting of 2 feet. Thin seams 

 are at 80,123 and 219 feet higher at Cameo on Grand River; but in 

 the Rollins district 3 workable seams were seen in 108 feet above 

 the base. Similar irregularity was observed in the easterly districts, 

 so that one must look upon the coal seams as lenses. The quality is 

 as variable as the quantity of coal. In one mine on the lowest seam, 

 irregular masses of white sandstone descend from the roof and 

 occasionally extend across the bed. Cross-bedded sandstone was 

 seen midway in the section at several localities. 



The Bowie shale, 420 feet thick on Grand River, has a sandstone, 

 100 feet, on top, cross-bedded, with worm tube^ and Halymenites. 

 Only one coal seam is there, about 430 feet below the Cameo bed ; 

 this is unimportant and thins away toward the south. There is no 

 Bowie in the Rollins district, but it reappears farther east in the 

 Somerset district, where, near Bowie, it is 405 feet and has the 

 great top sandstone. The coal seams are numerous and at least 7 of 

 them are " relatively thick," aggregating 38 to 43 feet in this district. 

 The thickness of other seams has not been determined. The coals 

 are exceedingly variable and they may be only extensive lenses ; 

 but some of them attain notable thickness. The Juanita bed is 12 



