430 proceedings: geological society 



On the other hand the more or less classic section of southern and 

 central Wyoming, as established by King, Hayden, Darton, Stanton, 

 Knowlton, Veatch, and others, has been carried by detailed mapping 

 by Bowen, Barnett, Wegemann, Lupton, Hares, and others, northward 

 to the northern boundary of Wyoming and even beyond to the Yellow- 

 stone River. The area along the Montana-Wyoming State line may 

 be likened naturally to the closing point on an engineer's survey, and 

 it is found that the formations of the two classic sections join up for the 

 most part, as previous general correlations have been made, but vary 

 in certain details. 



The southern and central Wyoming section includes the following 

 formations in the Colorado and Montana group, from the bottom up, 

 the Thermopolis shale, Mowry shale, Frontier formation, Carlile shale, 

 Niobrara shale, Steele shale, Mesaverde formation, and Lewis shale. In 

 the detailed work it was found that the Thermopolis, Mowry, Frontier, 

 and Carlile are recognizable units as far north as the Yellowstone River 

 and possibly beyond, and that along the Montana-Wyoming State line 

 the Niobrara, as mapped in central Wyoming by Wegemann, Barnett, 

 Bowen, and Hares, falls about 1400 feet below the top of the Colorado 

 group and the base of the Eagle sandstone. The Steele shale along the 

 same line includes the upper part of the Colorado shale, the Eagle 

 sandstone, and the lower part of the Claggett formation. The Mesa- 

 verde corresponds to the upper part, or Parkman sandstone member, 

 of the Claggett and the Judith River. The Lewis shale has been rec- 

 ognized as far north as the Wind River basin and Salt Creek, Wyoming. 



It has been fairly definitely established that the type Eagle sandstone 

 includes in its lower part the massive cliff-forming sandstone at Park 

 City and Billings, but about 100 feet below the massive sandstone is a 

 thin sand, 10 to 40 feet thick, which contains an Eagle fauna. This 

 lower sand is rim-forming from Park City to Elk Basin and the Shoshone 

 River, but from there south it is represented, as is the remainder of the 

 Eagle formation, by thin-bedded sandstones and arenaceous shales. 

 This sand has been called the Elk Basin sandstone member of the Eagle. 

 Further, it seemingly corresponds to the Shannon sandstone as mapped 

 in the Casper-Salt Creek region, and it may be found still farther south. 

 The body of shale between this horizon and the Mesaverde as a rule is 

 light-colored and sandy, whereas the shale below the Elk Basin sand- 

 stone member of the Eagle and above the Carlile shale is darker colored, 

 contains thin limy layers, and concretions that weather reddish-brown. 

 The southern extension of the Eagle sandstone into Wyoming seems to 

 represent the thinning out to a feather-edge of a recessional sand that 

 is massive, thick, and resistant in central Montana. It has been found 

 that the upper part of the Claggett shale grows more and more sandy 

 as it is followed southward into Wyoming and includes about 540 feet 

 of massive sandstones and thin-bedded shales of which at least the lower 

 part is marine; and, further, that this ridge-forming sandstone — called 

 the Parkman sandstone member of the Claggett— corresponds to the 

 lower part of the Mesaverde, also called the Parkman sandstone mem- 



