Late-pleistocene eolian sand sheets in Alaska

Peter D. Lea, Bowdoin College
Christopher F. Waythomas, University of Colorado Boulder


Nonglaciated lowlands in central and southwestern Alaska contain extensive deposits of upper-Quaternary eolian sand, derived largely from major outwash rivers. Although surface dunes are common, deep exposures consistently reveal that subhorizontally stratified sand and silt deposits dominate over dune cross strata. We hypothesize that (1) many of the subhorizontally stratified deposits represent full-glacial eolian sand sheets, formed when sand supply was limited by seasonally variable combinations of ice cementation, snow cover, high groundwater tables, and vegetation, and (2) many surface dunes reflect late-glacial and postglacial reworking under conditions of increased short-term availability of loose sand. The morphology of some surface dunes may therefore reflect mainly the intensity of reworking since the last glacial maximum, rather than full-glacial paleowind vectors or the age of the bulk of the underlying deposits. © 1990.