97 New Perspectives on Beringian Paleoecology, Paleoclimate, and Paleoceanography

This session will showcase the use of new sedimentary records and analytical techniques to augment reconstructions of Beringian and North Pacific Gateway paleoclimate and paleoecology and elucidate the role of terrestrial and marine linkages.

Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 303C

Late Pleistocene paleoclimate preserved in MIS-3 and MIS-4 loess along the eastern Bering Sea coast, Alaska

Paper number: 97-2
Program: Technical Sessions
Time: 8:25 AM – 8:40 AM

Authors

Abstract

The Yukon-Kuskokwim Delta (YK Delta) in southwestern Alaska is a critically understudied region for Arctic paleoclimate especially how climate history and geomorphic landscape evolution impacted the permafrost content and the current vulnerability of the landscape to thawing and rising sea levels. Aeolian sediment deposition (especially loess) and delta progradation and or transgression have played a significant role in developing the region's late Quaternary surficial geology. We have identified and mapped upland features, 10 – 20 m above sea level (asl), distributed across the modern delta that broadly match loess deposition maps of Alaska first introduced by Muhs et al. (2003). We have explored two new exposures located on the coastal portion of Nunivak Island and on the YK Delta west of the Kuskokwim River outlet.  The low carbon content (~4% loss on ignition) and the dominant clayey silt texture (~25 µm) of the exposures match characteristics of previously described loess deposits found higher in the watershed and in other parts of the world. Radiocarbon (14C) and infrared stimulated luminescence (IRSL) are in good agreement at our site near the Kuskokwim River, suggesting continuous loess deposition between ~49,000 – ~24,000 years before present (49 – 24 ka). Around the same time, loess sourced from NW Alaska was being deposited at Zagoskin Lake to the north. (Muhs and Pigati, in press).  Our exposure on Nunivak Island has more limited age control with 4 14C ages approaching 50ka and two IRSL ages from the topmost unit constraining loess deposition between ~72 and ~60.1 ka. One IRSL age from the base of the exposure yielded an age of 150ka. More IRSL ages are forthcoming. Preliminary branched glycerol dialkyl glycerol tetraethers (brGDGTs) indicate warmer and cooler temperatures than present-day at both sites. Further work including XRF scanning on two continuous sediment cores taken through the exposures allows us to produce a continuous downcore record of regional paleoclimate and transitions in the deposited loess’ biophysical properties. These data build on previous but limited work on the landscape history and evolution. 

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414341

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