38 Smithsonian Exploration in Alaska in 1904 



localities along the coast of Bering Sea and in the banks of the 

 Yukon." 



The older elevated ice-beds of the Pleistocene lake basins appar- 

 ently have been covered and preserved in this way. As exposed 

 today by the lateral cutting of the streams draining their areas the 

 ice-beds have a covering of peat varying from two or three to 

 fifteen feet in thickness. In most cases this protective covering to 

 the ice is composed entirely of vegetable remains. It is only rarely 

 that recent alluvium or soil is incorporated with the peat or humus 

 covering. This is because of the relative positions of the ice-beds 

 with reference to drainage levels that have existed in these areas 

 from the time they formed to the present. This absence of allu- 

 vium above these elevated beds of old ice — when examined at the 

 places of their typical development, that is, out on the undulating 

 Pleistocene lake bottoms — distinguishes them from the newer, less 

 extensive occurrences of ice intermingled with the materials of the 

 present flood plains, that are subject to annual overflows and conse- 

 quent depositions of alluvium. 



Only where the ice masses formed near the shore lines of the 

 former lakes, and in places where the land rises more or less 

 abruptly, may we expect to find alluvium derived from the nearby 

 slopes on top of the ice or incorporated with its humus covering. 



The ice phenomenon at Eschscholtz Bay seems to be clearly an 

 example of former lake-shore conditions as is also the locality on 

 the Beresowka River in northeastern Siberia described by Tol- 

 matschow." 



3. coastal-plain ice-beds, not of snow origin 



The significance of coastal-plain ice-beds is not clear to the writer. 

 They are not elevated to such a height nor as uniformly or ex- 

 tensively as the beds in the elevated Pleistocene lake areas. They 

 are not of snow origin or we should expect to see the process of 

 their formation going on today. Some tentative suggestions are 

 offered. These deposits occur, as far as known, along the Arctic 

 coast and only in areas that have undergone comparatively recent 

 heavy sedimentation. It is reasonable to suppose that the shifting 

 of the mouths of the rivers and the consequent change of areas of 

 loading have caused a shifting of regions of depression and upheaval 

 during Quaternary times. Thus shallow lakes, bays, or sounds re- 

 sulted, according to the extent of the viplifting. Wave and floe-ice 



" Verhand. der Kaiser. Russ. Min. Gesell. Bd. XL, Lief. 2, 1903. 



