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

​​Constraining changes in the sources of organic matter on the Bering Land Bridge during the Late Pleistocene: A stable isotopic approach

Paper number: 97-5
Program: Technical Sessions
Time: 9:10 AM – 9:25 AM

Authors

Abstract

The Bering Land Bridge (BLB) was subaerially exposed during glacial stages and served as a corridor for the exchange of flora, fauna, and early humans between eastern (present-day Alaska and Canada) and western (present-day Russia) Beringia. After the last glaciation the BLB was flooded (11.5-13.3 ka), separating eastern and western Beringia and removing access to study the paleoenvironmental conditions of the BLB. In 2023, 91 sediment cores from 36 sites across the Bering Sea continental shelf were recovered during a research cruise on the R/V Sikuliaq to better understand the paleoenvironmental conditions of the BLB. Part of this effort includes constraining changes in sources of organic matter to help reconstruct the nature of past ecosystems (e.g., freshwater aquatic vs. marine vs. terrestrial) at each of our study sites. Here, we present stable carbon and nitrogen isotope compositions (expressed as δ13C and δ15N values, respectively) and carbon/nitrogen ratios (C/N) of bulk sediments, and preliminary radiocarbon ages of 10 sediment cores located between 57°N to 64°N and 161°W to 177°W on the Bering shelf. We applied a Bayesian mixing model using the δ13C, δ15N, and C/N data to determine changes in the relative proportional contribution of different organic matter sources over time. Sediments from sites located close to the present-day coast (i.e., Norton Sound) and on the inner shelf were dominated by terrestrial organic matter (>80%) at the bottom or throughout (>90-95%) the core. Cores from the outer shelf show a dominance of marine organic matter throughout the core and/or fluctuation between dominance of terrestrial and marine organic matter at the base, followed by a transition to a fully marine source. Preliminary radiocarbon ages and changes in the proportional contribution of terrestrial vs. marine organic matter sources show that the southeastern, central, and northeastern (Norton Sound) BLB were flooded by ~19-30 ka, ~14-12 ka, and ~10-11 ka, respectively.

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

doi: 10.1130/abs/2025AM-413776

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