Dune stabilization in central and southern Yukon in relation to early Holocene environmental change, northwestern North America

Eolian deposits of central and southern Yukon, northwestern Canada, consist of loess mantles, small areas of active dunes, and larger stabilized dune fields. Dune fields in valley settings within the region are situated both within and beyond the limit of the last glaciation. Infrared stimulation luminescence (IRSL) dating in central and southern Yukon reveals that these dune fields stabilized as late as 9–8.5 ka, well after the retreat of Cordilleran glaciers. These findings are comparable to other valley-setting dune fields and loess from central Alaska, which record activity during the period from the Lateglacial to the Holocene Thermal Maximum (HTM), and reduced or altered activity after 9–8 ka. Post-glacial dune activity was most likely related to warm, dry conditions during the HTM, under predominantly shrub-tundra vegetation. Early Holocene stabilization of these dunes probably occurred in response to cooler, moister conditions, and replacement of predominantly tundra by boreal forest cover, dominated by spruce. Stabilization of dune fields in southern Yukon and Alaska most likely represented an extension of the time-transgressive stabilization of dune fields that occurred across northwestern North America with the post-glacial expansion of the boreal forest.