386 



Medicine Bow 



Range 



F 



7,500 



5,000 



2,500- 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



Sheep Mtn. 



7,500' 



5,000 



2,500' 



Green Ridge 



2,500 



Fig. 24.19. Cross sections along the east front of the Medicine Bow Range and the west side 

 of the Laramie basin, after Beckwith, 1938 and 1942. Cfn, Fountain fm., Cc, Casper fm.; Cs, 

 Satanka sh.; Cf, Forelle Is.; He, Chugwater fm.; T\, Jelm fm.; Js, Sundance fm.; Jm, Morrison 



Medicine Bow 

 Range 



A pt 



7,500' 



5,000- ~\yt 



7,500' 



IV ■ 5,000' 



fm.; Kd, Dakota group; Kb, Bsnton group; 

 Kl, Lewis sh.; Twr, White River group. 



■ 2,500' 



Kn, Miobara fm.; Ks, Steel sh.; Km, Mesaverde fm.; 



marine Lewis shale and several thousand feet of grits, standstones, carbonaceous 

 shales, and coals constituting the Medicine Bow formation. The Medicine Bow 

 is overlain unconformably by the Hanna formation. At the Citizen's Coal Mine, 

 5 miles north of Sheep Mountain, the lower beds of the Medicine Bow contain 

 conglomerates with pebbles of Dakota sandstone and Mowry shale several 

 inches across. Thousands of feet of marine beds must therefore have been 

 stripped from the adjacent rising arch by early Medicine Bow time. A similar 

 conclusion is reached for the region to the south. 



Lovering (1935) states: 



Before the end of Pierre time, the central part of the Front Range highland 

 was pushed above the level of the sea, and recently deposited shales were ex- 

 posed to erosion. They were reworked into the upper part of the marine Creta- 

 ceous, and the Dakota sandstone was also exposed and reworked in many 

 places and was probably the source of much of the sandy material found in the 

 Fox Hills sandstone. 



