| Summary: | Pleistocene periglacial eolian sediments are widespread in the Nushagak, Holitna, and Upper Kuskokwim lowlands of southwestern Alaska. These sediments comprise mainly sand-sheet deposits and sand-loess intergrades, with subordinate sand-dune deposits and loess. Sand-sheet deposits range from 1) sharply defined, parallel, low-angle laminae by migrating wind ripples to 2) irregular subhorizontal strata which reflect migration of poorly segregated wind ripples, accumulation on a sparsely vegetated surface, adhesion on a quasi-planar bed, and/or niveo-eolian deposition. Sand-loess intergrades represent alternating bed-load and suspension deposition related mainly to the stochastic and seasonal variability of former wind systems. The dominance of sand-sheet deposits over deposits of well-formed dunes in the Pleistocene eolian record of southwestern Alaska reflects the limited availability of loose, dry sand in this former periglacial environment. Immobilization of sand after deposition as low-relief sheets resulted from a seasonally variable combination of ice cementation, sparse vegetation, high water tables, and snow cover. -Author
|
|---|