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

Wet, Woody, Windy, and Woolly: The Mosaic Habitats of Central Beringia

Paper number: 97-4
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

Central Beringia (a.k.a. the Bering Land Bridge) is widely considered to have been an extension of the cold, dusty steppe that covered Eastern and Western Beringia during glacial stages. However, the lack of sedimentary records from sites below modern sea level has complicated efforts to reconstruct the climate and vegetation of this region. In 2023, we conducted a cruise with the goal of identifying and coring lakes that were present on the land bridge. We expected to find a few large lakes. Instead, Chirp images revealed networks of filled channels with small basins in between. Integration of sub-bottom profiles from prior expeditions confirms that swaths of Central Beringia were transected by anastomosing river floodplains dotted with freshwater ponds or bogs. These represent the former courses of the Yukon and Kuskokwim rivers on the low-gradient land bridge.

Cores collected from 30 sites in the Bering Sea at water depths less than ~100m all contain a basal freshwater sedimentary unit overlain by marine mud or sand. A freshwater origin for these basal deposits is confirmed by plant macrofossils, diatoms, and stable isotope analyses. Preliminary dates indicate that the ponds or bogs were present prior to ~25ka or after ~22ka but may have dried up during the last glacial maximum.

Pollen and sedaDNA analyses of freshwater sediment indicate the presence of woody plants, including birch, alder, poplar/aspen, and willow, in addition to abundant sedges. Contrary to expectations, woody plants and ferns appear to have been more common on the interior of Central Beringia than near the southern coast. This is supported by sedaDNA results that place wetland fauna, such as ducks and beavers, at inland locations. These spatial variations suggest that rivers flowing over permafrost were the main source of moisture, not coastal precipitation.

Preliminary sedaDNA results indicate that mammoth populations were present throughout the southern half of the land bridge, while horses and bison were less common. Perhaps higher, better-drained sites were covered by steppe vegetation, providing habitat for grazers, while low-elevation regions supported woody plants and wetland fauna on extensive floodplains. We conclude that Central Beringia was more mesic than Eastern or Western Beringia during the last glacial stage, but we emphasize that the climate, flora, and fauna were not uniform.

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

doi: 10.1130/abs/2025AM-413788

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