TITLES AND ABSTRACTS OF PAPERS 14P) 



GLAGJAL FORMATIONS IN THE WESTERN UNITED STATES 

 BY FRANK LEVERETT 



(Abstract) 



In the summer of 1916 the writer made the circuit of tlie chief areas of 

 glaciation in tlie western United States to compare the glacial formations 

 there with those of the eastern United States. 



The three drifts of the San Juan region in Colorado seem to correlate well 

 with the Wisconsin, Tllinoian, and the Kaiisnii. The middle or Durango drift 

 has moraines as well preserved as the lUinoian drift, and a weathering and 

 erosion more nearly in accord with the Illinoian than with the Kansan. The 

 oldest, or Cerro, drift is reduced to patches preserved in places where erosion 

 has been at a minimum. Its scanty preservation may seem to indicate that 

 it is older than the Kansan, but conditions for erosion are so favorable in the 

 Colorado field that it is to be expected that a deposit of Kansan age would be 

 largely removed. 



In the Yosemite region in California only the western slope of the Sierra 

 Nevada was examined. There are two sets of moraines widely different in 

 age, the younger of which seems to extend from the Wisconsin time into post- 

 Wisconsin. The older set seems to be no older than the Illinoian, for the 

 moraines have good preservation on slopes which are favorable for rapid ero- 

 sion. They could hardly be expected to be so well preserved if of Kansan age. 



In the Puget Sound region in Washington the Admiralty till appears to be 

 as old as Kansan drift, while the Vasliou till seems to be of Wisconsin age. 

 In the Mount Rainier region post- Wisconsin moraines are present, as well as 

 those of Wisconsin age. Those of Wisconsin age have a discoloration and 

 weathering to a depth of several feet, while the post- Wisconsin moraines are 

 nearly free from weather staining to within a few inches of the surface. The 

 reference of the Admiralty till to Kansan rather than to Illinoian age is based 

 on: (1) The condition of the till itself as to weathering and alteration. (2) 

 The amount of erosion it seems to have suffered prior to the last giaciation. 

 (3) The occurrence of partly lignitized, interglacial peat above it. 



In northeastern Washington the occurrence of a very old drift, probably 

 Kansan, was established by the discovery of till and striated stones on a liigli 

 divide southwest of Spokane in the vicinity of Cheney. Boulders had been 

 observed in this region and the possibility of giaciation had been suggested l)y 

 M. II. (3ampl)e]l in the Nortlie]-n Tacific Guide Book. 



The writer also visited the Yakima Valley, in southern Washington, where 

 erratic boulders occur whose distribution has been referred by earlier students 

 to floating ice. It seems an open question, however, whether this region, like 

 that near Spokane, may have been glaciated in early Pleistocene time. 



In central Oregon observations were made west of Sisters on moraines of 

 Wisconsin age which are found down to within five miles of that village. Out- 

 wash material around the village is probably of Wisconsin age, but faint 

 ridges two to three miles west may prove to be worn down moraines of pre- 

 Wisconsin age which are nearly buried under later deposits. Flows of basalt 

 have occurred in the district subsequent to the Wisconsin giaciation, the basalt 

 being over the Wisconsin drift deposits. 



