538 



PRE-WISCONSIN GLACIAL DRIFT IN MONTANA 



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Heading at a point 1 mile northeast 

 of Davis Kanch and about 4 miles east of 

 the east end of Duck Lake (plate 13), 

 and extending thence northeastward a 

 distance of 8 miles, is another abrupt 

 ridge with remarkably smooth, flat top 

 (figure 4). This high-level plain has a 

 maximum width of about 1% miles and 

 is another remnant of the highest and 

 oldest plain. In the northeastern part 

 of township 36 north, range 11 west, the 

 ridge has been lowered by erosion, but 

 one going northeastward about 5 miles 

 across the gap reaches the head of an- 

 other like remnant of the highest plain, 

 in northwest 14. section 31, township 37 

 north, range 10 west, which extends 

 thence northeastward nearly to the Inter- 

 national Boundary. A small remnant of 

 the same plain persists as the top of the 

 ridge between the head of Kennedy Cou- 

 lee on the north and South Fork of Milk 

 Eiver on the south. 



These remnants of the highest plain 

 are underlain by a deposit of gravel, 

 mostly quartzite and red and green, si- 

 liceous argillite. with some diorites, all 

 from the mountains. The tops and slopes 

 of the ridges are grassed over, and it is 

 only at intervals around the margins of 

 the tops that as much as 1 to 3 feet of 

 the deposit, which is probably thin, is 

 exposed. 



Xo striated pebbles were noted east of 

 range 11 west, but in the western part 

 of this township and at a point nearly 

 north of Stones Ranch, township 36 

 north, range 12 west, section 23, careful 

 search revealed some pebbles of greenish 

 argillite with faint striations suggesting 

 glaciation, but not indisputable. The 



