564 PRE-WISCONSIN GLACIAL DRIFT IN MONTANA 



interglacial beds, and this sub-Aftonian till was regarded as the oldest 

 known deposit of the Keewatin glacier. 



Believing that the drift of the Cordillera n glaciers, which he had cor- 

 related with the gravels underlying the lower boulder-clay of the conti- 

 nental glacier, was older than this early till of the Keewatin ice-sheet and 

 should have a distinct name, he proposed the name "Albertan" as fol- 

 lows : 23 



"Reverting now, on the basis of the above correlation, to the Saskatchewan 

 gravels and the 'western' boulder-clay, it will be apparent that these must 

 represent an antecedent and unnamed stage of glaciation in North America. 

 This, with scarcely any doubt, may, from the observations given in this paper, 

 be regarded as that of the maximum of the Cordilleran glacier, and to it I 

 would propose to apply the name of the Albertan stage or formation." 



Further study of the Pleistocene deposits in the Mississippi Valley by 

 the geologists of the Iowa Survey and by Mr. Frank Leverett led to the 

 conclusion that it was the drift overlying rather than underlying the 

 Aftonian interglacial beds which extended into northeastern Kansas and 

 to which the name. Kansan should be applied. After considering this 

 question and making two excursions to examine some of the deposits, 

 Professor Chamberlin discussed the matter of classification in an edi- 

 torial in the Journal of Geology, 24 in the course of which he made the 

 following statement : 



"During the past summer I have had the pleasure of making two excursions 

 with Mr. Bain of the Iowa Survey to localities where the above formations are 

 advantageously exhibited, and I have been impressed with the cogency of the 

 arguments of the Iowa geologists. While, therefore, the case can not be said to 

 be demonstrative, as yet, it seems best to accept the application of the nomen- 

 clature adopted by the Iowa Survey. This places the Aftonian beds below the 

 Kansan series instead of above them. It puts the sub-Aftonian sheet of till 

 in an earlier category, and, for the present, it may perhaps be regarded 

 tentatively as Albertan, although, of course, it can not now be demonstrated to 

 be equivalent to the Albertan beds of Canada." 



The name "Albertan" thus passed into use tentatively as correlated 

 with the sub-Aftonian of Chamberlin. 25 Such usage was continued until 

 Calhoun concluded as a result of his observations that the drift of the 

 mountain glaciers which is overlapped near the 49th parallel in the val- 

 leys of Saint Mary and Belly rivers by drift of the Keewatin Glacier was 



23 Bull. Geol. Soc. Am., vol. 7, pp. 65-66. 



24 T. C. Chamberlin : Editorial, Journal of Geology, vol. 4, 1896, pp. 872-876. 



25 Frank Leverett : The Illinois glacial lobe. Monograph U. S. Geological Survey, vol. 

 38, 1899, p. 40. 



Prank Leverett : Glacial formations and drainage features of the Erie and Ohio 

 basins. Monograph U. S. Geological Survey, vol. 41, 1902, p. 20. 



