GEOLOGY OF THE BEARTOOTH MOUNTAINS, MONTANA 457 



surfaces, countless perched bowlders, and extensive morainal 

 deposits. The area thus glaciated is about 350 square miles 

 between the base of the axial divide on the northeast and the front 

 of the Absaroka Range on the southwest. An extraordinary feature 

 of this glacier was the formation of several distinct valley lobes 

 which passed into valleys sharply trenched athwart the axial divide, 

 then descended these valleys to the plains beyond the eastern base 

 of the range, where conspicuous moraines were formed. 



Fig. 9. — The recent lateral moraine on the southeast side of East Rosebud Creek. 

 Its height is about 600 feet. 



STRUCTURE 



General form of the range. — The Beartooth Range is structurally 

 a broad asymmetric anticline that is in part strongly overturned 

 toward the Great Plains and broken along its northeast limb by a 

 huge fault (Fig. 10). The Paleozoic formations on the southwest 

 slope commonly have low southwesterly dips whereas along the 

 northeast flank they exhibit a variation from high easterly dips to 

 overturned beds that are more than 70° beyond the vertical. Num- 

 erous minor faults and folds exist along this side of the range and 

 in the adjacent plains. 



The Beartooth overthrust. — The plains-ward front of the range 

 is bounded throughout almost its entire length by the Beartooth 



