268 G. R. MAXSFIELD STRUCTURE OF ROCKY MOUNTAINS 



Mountains, has a length of about 35 miles as mapped by Calvert.^ It 

 was not at first considered as an overthrust, but its relationship to zones 

 of overthrusting farther southeast makes this interpretation highly 

 probable. 



The Heart Mountain overthrust, first described by Dake^ and later by 

 Hewett, has a minimum horizontal displacement of 28 miles and should 

 be traceable over the entire eastern edge of the Absaroka Range perhaps 

 for 125 or 150 miles. 



The Darhy fault, as mapped by Schultz,^^ has a length of about 125 

 miles and a horizontal displacement perhaps greater than 15 miles. 



The AhsaroJca fault, as mapped by Veatch^^ and Schultz,^^ has a known 

 length of approximately 200 miles. Its zone of displacement may exceed 

 25 miles in breadth and its throw.(stratigraphic?), like that of the Darby 

 fault, is said to exceed 20,000 feet. 



The Medicine Butte and Crawford faults, as mapped respectively by 

 Veatch^^ and by Gale and Richards/* in southwestern Wyoming and in 

 northeastern Utah, are overthrusts on a smaller scale than most of the 

 preceding. 



A thrust-fault some 30 miles in length has been recognized by Schultz 

 and Richards^^ along Snake River, but little is known of its displacement. 



The Bannock overtlirust, as mapped, is about 270 miles long and has 

 a maximum displacement perhaps greater than 35 miles. It seems pos- 

 sible that the Bannock over thrust and the Putnam over thrust, to which 

 reference has already been made, may prove to be connected. 



The Willard overtlirust, as described by Blackwelder,^^ is about 22 

 miles long and has a maximum displacement of at least 4 miles. It is 

 exceptional for the Rocky Mountain region, in that the inclination of its 

 plane is apparently eastward instead of westward. 



8 W. R. Calvert : Geology of the upper Stillwater basin, Stillwater and Carbon coun- 

 ties, Montana. U. S. Geol. Survey Bull. 641, 1917, pp. 109-214. 



s C. L. Dake : The Hart Mountain overthrust and associated structures in Park County,. 

 Wyoming. Jour. Geol., vol. 26, 1918, pp. 52-58. 



D. F. Hewett : The Heai-t Mountain overthrust, Wyoming. Jour. Geol., vol. 28, 1920, 

 pp. 536-556. 



" A. R. Schultz : Geology and geography of a portion of Lincoln County, Wyoming. 

 U. S. Geol. Survey Bull. 543, 1914, pp. 84-85, map. 



" A. C. Veatch : Geography and geology of a portion of southwestern Wyoming. U. S. 

 Geol. Survey Prof. Paper 56. 1907, pp. 109-110. ■ 



^ Idem., p. 87, and U. S. Geol. Survey BuU. 680, 1918. 



"Idem., pp. 111-113. 



" Op. cit., p. 515. 



^^ A. R, Schultz and R. W. Richards : A geologic reconnaissance in southeastern Idaho. 

 U. S. Geol. Survey BuU. 530, 1913, p. 277 and pi. vi. 



1^ Eliot Blackwelder : New light on the geology of the Wasatch Mountains, Utah. 

 Bull. Geol. Soc. America, vol. 21, 1910, pp. 517-542. . 



