702 W. C. ALDEN PRE-WISCONSIN GLACIAL DRIFT IN MONTANA 



drift is to be correlated with the other deposits described as having been 

 laid down by ice during a pre-Wisconsin extension of the mountain 

 glaciers. 



Deposits on Kennedy Ridge 



North of North Fork of Kennedy Creek in the area east of Chief 

 Mountain is a hilly tract underlain by Cretaceous sandstones. A part 

 of this at least Avas covered by ice at the last stage of glaciation, but 

 little of it was examined during the past summer. Rising above the 

 general level of this tracts just north of Kennedy Creek, is a small, 

 abrupt, flat-topped mesa having an elevation 5,800 feet above tide and 

 900 feet above the stream on the south (figure 2, plate 40). This was 

 described by Mr. Willis in his paper on the Lewis and Livingston 

 Ranges® as "the typical occurrence of the Kennedy gravels." Tlie slopes 

 of this mesa are abrupt scarps due to landslides, and in places these 

 scarp faces are bare of vegetation and give good exposures of the com- 

 ponent material, 100 feet or more in height. This material is coarse 

 cobblestone gravel and small boulders. A large part of the stones are 

 subangular and facetted and some of it is well rounded. No evidence of 

 assortment or bedding was noted and, to the writer, the aspect was rather 

 that of gravelly glacial drift than of stream gravels. Moreover, careful 

 search yielded numerous pebbles carrying striations which, if not due to 

 glaciation, are certainly identical in character with such as were pro- 

 duced by glaciation. The stones, which are wholly pre-Cambrian rock 

 from the mountains, consist principally of buff limestone and quartzitic 

 material from the Altyn formation, and with this is a subordinate 

 amount of red and green argillite. Striations were found only on pieces 

 of the greenish dense quartzitic argillite. The surfaces of other pebbles 

 had been sufficiently etched and roughened by weathering to remove 

 striations if such were present. The ridge stands so high and is so 

 narrow and so exposed on all sides that conditions particularly favor the 

 surficial modifications of the material by the various agencies of weatli- 

 ering. 



Mr. Willis reports^° that Mr. George I. Finlay, who examined the 

 deposit, did not find striated pebbles. Concerning their interpretation, 

 he writes as follows: 



"The constituent materials, the forms of the honlders and pebbles, the 

 obscure stratification, the topotrraphic form, and the position of the mesa, all 

 characterize this occurrence as a remnant of an alluvial cone of Kennedy 



» Op. cit., pp. 328.330. 

 w Op. clt., pp. 328-330. 



