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

Characterizing the Deglacial Environment of the Southern Beringian Coastline

Paper number: 97-9
Program: Technical Sessions
Time: 10:15 AM – 10:30 AM

Authors

Abstract

The Bering Sea “Green Belt” is the region along the Bering shelf edge with anomalously high biological productivity caused by deepwater upwelling from the Aleutian Basin. The primary productivity of algae, in particular diatoms, above the shelf edge supports the marine fauna of the surrounding regions. In the fall of 2023, on board the R/V Sikuliaq (SKQ202311S) the 12.2-meter-long piston core, 75JC, from the site “Finding Porpoise” (61.613 N, 177.122 W, 117 m water depth) and the 14.6-m-long piston core, 79JC, from the site “Rhubarbie’s World” (61.763 N, 176.429 W, 104 m water depth) were collected as part of a transect across the Bering shelf edge. Computed tomography (CT) scans, bulk sediment stable isotopes, radiocarbon dates, and diatom counts are used to quantify changes in the sedimentation regime since the late Pleistocene. Isotope values and core descriptions indicate that the two sites remained offshore throughout the sea level lowstand of the last glacial stage. Radiocarbon dates and CT scans indicate the presence of three sedimentary units between the two cores. These are interpreted as an offshore marine unit eroded by sea ice scour, overlain by a deltaic unit, with an open marine unit at the top. Radiocarbon dates indicate the basal unit of 75JC is of late Pleistocene age (42 Cal kyr BP) and contains low absolute diatom abundances. The second unit, in the middle of 75JC and the base of 79JC, dates to the deglaciation (15 Cal kyr BP). Terrestrial input decreases upcore, and neritic diatoms decrease at the top of the deltaic unit. The delta unit has lower percentages of high-productivity diatoms (Chaetoceros spp.) than the open marine units, particularly at the base. However, it contains percentages of sea ice-associated diatoms similar to those in the uppermost unit. The top unit of both core sites (collected in the adjoining trigger cores and multicores) preserves modern conditions with variable percentages of sea ice diatoms, reduced proportions of neritic diatoms, and a predominantly marine influx of carbon indicated by isotope values. This work provides insight into the Holocene history of the Bering Sea Green Belt, documents increasing productivity, and reconstructs similar to modern sea ice concentrations through diatom assemblages along the Beringian coastline during the last glacial period.

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

doi: 10.1130/abs/2025AM-413292

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.