532 PRE-WISCONSIN GLACIAL DRIFT IN MONTANA 



with similar topographic relations, so that it is evident that there is here 

 another remnant of the pre-Wisconsin glacial drift. 



Ridge East of Waterton Lakes 



Looking west from the top of Belly River Eidge, there is a fine view 

 of the north end of the Lewis Range, a few miles north of the Interna- 

 tional Boundary. From the horizon of the Lewis overthrust, at the base 

 of the bold cliffs of pre-Cambrian limestone, a long low slope, developed 

 on the soft Cretaceous and Tertiary rocks, extends several miles north- 

 ward. Rising above this slope is a narrow wooded ridge, the straight 

 though notched top of which is a remnant of the higher level on which 

 the observer stands. West of this are Waterton lakes. This ridge was 

 not examined, but it is thought probable that this also is capped with the 

 pre-Wisconsin glacial drift. 



Absence of Peneplain Remnants in southern Alberta 



As far as we traversed the plains of southern Alberta to the northwest 

 and north, no other remnants of the high-level plains were seen. Even 

 the Porcupine Hills, so far as seen, show nothing of such a high-plain 

 surface. It is possible that some slight remnants .of the peneplain persist 

 close to the mountain front at places which we did not examine, but it 

 is evident that Willis's Blackfoot peneplain surface has been almost en- 

 tirely cut away from southern Alberta, unless it be represented by the 

 top of Milk River Ridge, which, in the part north of the boundary, is 

 farther east than the line of our traverse. 



Remnants of Peneplains in Browning and Blackfoot 

 Quadrangles, Montana 



South of the 49th parallel, in the Browning quadrangle, the geology 

 of which, especially, is being studied by Mr. Stebinger, and in the north- 

 western part of the Blackfoot quadrangle, there is the best preservation 

 of remnants of the high-level plains found anywhere in the region. Over 

 a triangular area having an extent of about 30 miles from north to south 

 and about the same from east to west there are 15 or 20 more or less 

 distinct remnants of the ancient plain surfaces having a total extent of 

 100 square miles. The nearly flat, plain surfaces of the bedrock under- 

 neath the surficial deposits on these elevated plateaus are planes of erosion 

 developed indiscriminately over the flat-lying Cretaceous and Tertiary 

 beds and over the upturned edges of the strata in the zone of folding 



