Tephrochronology and paleoclimatology of the Last Interglacial-Glacial cycle recorded in Alaskan loess deposits

Abstract

Abstract Alaskan loess deposits contain long paleoclimatic records analogous to those found in marine and lacustrine sediments and in ice sheets. The sedimentology and geophysical properties of Alaskan loess were influenced by climatically forced changes in wind intensity, storminess, temperature, and precipitation. Loess deposits also contain evidence of episodic permafrost and paleosol formation, explosive volcanic eruptions, paleoecologic changes in high latitude regions, Quaternary fossils, and early human sites and artifacts. The Old Crow tephra (ca. 140,000 ± 10,000 BP) dates the transition between full-glacial conditions and the last interglaciation in central Alaska. Climatic amelioration in Alaska apparently began prior to astronomically forced increases in insolation, a finding consistent with the well-dated Devil's Hole record. However, time-series analysis of loess proxy climate data also demonstrates the effects of orbital precession and obliquity on Alaskan climate change. Numerous short-term climate events are recorded in Alaskan loess deposits, including a climate reversal corresponding to the Younger Dryas.