104 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



part of the column near Bighorn Mountains are shown by the fact 

 that Darton embraces the whole above his Parkman sandstone in a 

 single formation, the Piney. Woodruff in the southeastern part 

 of the basin found indefiniteness throughout, but the succession is 

 suggestive of the section as recognized in Montana and northward, 

 there being at base shales with Pierre fossils succeeded by two sand- 

 stone and shale members which he referred provisionally to the 

 Eagle sandstone and Claggett shale of Montana, while he terms the 

 higher beds merely Undifferentiated Montana. All become more 

 shaly toward the east. Coal seams were seen in the upper division, 

 but they are lenticular and unimportant : the quantity decreases to- 

 ward the north. In the western portion, Woodruff recognized the 

 Eagle sandstone of the Montana section, but none of the higher 

 divisions could be identified. Coal seams in the Eagle are lenticular, 

 but occasionally they are important. One near Gebo is ii feet 

 thick ; in Grass Valley, a seam, 7 to 8 feet, is mined, but within a 

 fourth of a mile toward the west it is too thin to be worked, while, 

 at an equal distance toward the south, it becomes much thinner and 

 so broken by partings as to be worthless. Similar variations in the 

 Eagle coals were observed elsewhere within this portion of the field. 

 Farther south in the Buffalo Basin no coal has been found in the 

 Eagle. The Undifferentiated Montana has some coal seams but 

 they are wholly unimportant. 



In the northeastern part of the basin, extending into Montana, 

 Washburne was able to recognize all members of the Pierre as they 

 had been determined in Montana — Bearpaw shale, Judith River For- 

 mation, Claggett shale. Eagle River sandstone, the last resting -on 

 Colorado shale. The Bearpaw, evidently the Lewis of localities 

 farther south, is marine, 150 feet thick and without coal; the Judith 

 River variegated clays and sandstone, 300 to 400 feet, has abundance 

 of leaves and bones but seems to be without coal ; the Claggett, 400 

 to 500 feet, consists of massive gray to yellow sandstone with inter- 

 bedded shales and has marine fossils in many portions ; the Eagle, 

 150 to 225 feet, has two or three massive sandstones. The upper 

 part of the Colorado shale, for 1,000 feet, is without fossils, but it 

 differs lithologically from the shales below and it may be taken as, 

 at least in part, representing the lower shales of the Pierre as in the 



