AEOLIAN SAND DEPOSITION OVER THE LAST 20,000 YEARS IN THE MIDDLE TANANA VALLEY, INTERIOR ALASKA
Radiocarbon and luminescence ages provide initial age constraints on aeolian sand deposition in the region, indicating that the development of linear dunes and lowland and cliff-head sand sheets are associated with the end of the Last Glacial Maximum and the early Late Glacial period (20,000 to 14,000 years ago) during the waning of outwash deposition and immediately after the introduction of sand and silt sediment sources into the Tanana River basin. By 13,000 years ago, aeolian sand deposition generally transitioned to loess deposition in many areas in the valley and landforms became intermittently stable with soil development associated with the expansion of shrub tundra vegetation throughout the region. During the end of the Late Glacial and throughout the early Holocene (13,000 to 8,000 years ago), aeolian sand deposition was localized throughout the valley and likely occurred in response to different mechanisms including fire cycles, increased wind intensity, loss of vegetation, source exposure, and introduction of source sediment via flooding. At around 8,000 to 6,000 years ago, much of the aeolian sand deposition ceased and loess accumulation rates decreased in response to an increasingly stabilized landscape and the development of forest soils.