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
Sea-level driven isolation of glacial plant refugia revealed by submerged lake sediment from the Bering Land Bridge and St. Matthew Island, Alaska
Paper number: 97-1
Program: Technical Sessions
Time: 8:05 AM – 8:25 AM
Authors
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Lesleigh AndersonGeoscience and Environmental Change Science Center, Denver, CO
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Beth CaissieGeology, Minerals, Energy, and Geophysics Science Center, Moffett Field, CA
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David HarningCooperative Institute for Research in Environmental Sciences, Boulder, CO
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Thomas AgerGeoscience and Environmental Change Science Center, Denver, CO
Abstract
Central Beringian climate and vegetation during the Last Glacial Maximum (LGM) remains largely understudied, given challenges associated with collecting records from the submerged Bering Land Bridge. Previous records, confined mostly to the margins of the modern land area and adjacent shelf, reveal conflicting interpretations of the terrestrial Beringian environment during the LGM. Here, we reconstruct LGM vegetation, sedimentology, and stable isotopes from a central Bering Land Bridge paleo-lake (Lake Knebel; 61.2567˚ N, 172.568˚ W) and compare it with a Holocene peatland vegetation record from nearby St. Matthew Island (60.42 ˚N, 172.72˚W) to reconstruct central Beringian LGM vegetation and its implications for the timing of the deglacial sea level transgression. Results show strong similarities between LGM and late Holocene herb-sub-shrub tundra pollen assemblages, despite differences in relative taxonomic abundance, suggesting the preservation of LGM assemblages on St. Matthew Island that reflect the timing of its isolation from the Beringian land mass. We propose that a lack of Betula on St. Matthew Island during the Holocene is consistent with island isolation prior to ~15 ka, when Betula expanded rapidly at most present-day terrestrial sites during Bølling-Allerød warming. Meanwhile, Lake Knebel’s strongly bedded stratigraphy and sedimentology (grain size, composition, and organic carbon stable isotopes) reflects undisturbed, continuous deep-water sedimentation that transitions into undisturbed marine sediments during marine transgression by ~19 ka based on AMS radiocarbon dates on floating organic matter, providing a maximum limiting age of the transgression at Lake Knebel. The combined vegetation evidence indicates preservation of LGM tundra and steppe vegetation assemblages on St. Matthew Island and other Bering Sea islands today, and suggests that vegetation assemblages on other Bering Sea islands may similarly reflect the timing of the sea-level transgression, helping to further constrain Beringian sea level change.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-412976
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