458 



ARTHUR BEVAN 



fault, which is an over thrust of considerable magnitude. West of 

 Red Lodge the overturned Madison limestone on the west has been 

 brought against the upper part of the Fort Union formation on the 

 east side of the fault trace. Farther northwest, in the vicinity of 

 West Rosebud Creek, the relations of the faulted formations are 

 obscured by the widespread mantle of terrace gravel and glacial 

 drift, but it appears that the pre- Cambrian crystallines abut 



L/i^/r7^sforj Peak 



5W. 

 /nc/ejt Peak 



nt Villa 

 C/ark rork <S/aciofed Plataau 

 ) 



tVe3f PosetudCr: mtreod SwpSumm'rt P/ateou tA.E-. 

 (Sreaf P'/ains 



£aoO Fi tef aAoi^e ScfjLaye/ 



Section e> 



fiunferPeak 



(S.000^'^^& if 



&eorfoofh 3ullo 



£>eatrtoofh P/ateau 



Pock Cre&k LJns C/TSek Rofeau 



i)E-CxiON C 



Fig. io. — Geologic cross-sections of the Beartooth Mountains. Section A is a 

 modification of section CDE of the Livingston folio. AR, Archean; -C, Cambrian and 

 Ordovician; P, Devonian; C, Carboniferous; /, Jurassic and Comanchean; Kc, 

 Colorado; Km, Montana; Kh, Livingston; T/, Fort Union; T, Tertiary volcanics 

 and intrusives. 



against, or overHe, the upper part of the Livingston formation or the 

 lower part of the Fort Union formation. 



Along the southeastern front of the range, between the state 

 line and Clark Fork Canyon, the Beartooth fault becomes a zone 

 of thrust faults that in places cause the pre- Cambrian granite to 

 rest upon the Chugwater "Red Beds" (Triassic).^ "At one point 

 the Chugwater is dipping west (overturned) at angles as low as 

 20°, and passes under the granite. At another point, the Dakota 

 (Cloverly) was also seen dipping west at a very flat angle, and 

 clearly upside down. The evidence of overturning rested not only 



' C. L. Dake, "The Heart Mountain Overthrust and Associated Structures in 

 Park County, Wyoming," Jour. Geol., XXVI (1918), 52-53. 



