Abstract

Strong katabatic winds are frequently generated in glaciated mountain valleys of the Alaska Range by downglacier gravitational flow of chilled air. Stronger katabatic winds probably occurred during late Quaternary time, when glaciers were more extensive, and such winds may have greatly influenced eolian sedimentation. In Nenana River valley and in most of adjacent Teklanika River valley, the entire 1- to 2-m-thick eolian cap is postglacial in age, and the beginning of loess deposition coincides almost exactly with rapid recession of late Wisconsin ice. Previously deposited loess and bluff-edge dunes were apparently deflated during the last glaciation between 25,000 and 12,000 yr B.P. Loess deposition in these mountain valleys thus is exclusively an interglacial phenomenon; glacial phases are characterized by deflation.

Meteorological modeling of katabatic winds generated during the last glaciation predicts that paleowind velocities greatly exceeded the entrainment thresholds required for eolian deflation. When both Nenana River and Teklanika River valleys are compared, theoretical differences in the potential for generating katabatic winds and differences in valley physiography explain why pre-Holocene loess is preserved in downstream reaches of Teklanika River valley and not Nenana River valley. The presence of strong katabatic winds in mountain valleys beyond former glacier limits has significant implications for late Pleistocene paleoecology and archeology.

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