Historical Ecology in Beringia: The South Land Bridge Coast at St. Paul Island

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Abstract
A 14-m core of lake sediments from St. Paul Island yields a long environmental history of the south coast of the Bering land bridge. Tritium assay demonstrates that sands in the bottom 8 m of deposit are injected with modern water, suggesting that a radiocarbon anomaly is the result of modern carbon introduced in groundwater. The remaining radiocarbon chronology, coupled with a time-stratigraphic pollen-zone boundary suggests that the record penetrates to the mid-Wisconsin interstadial. Pollen percentage data,Piceapollen influx, and pollen species lists allow reconstruction of the land bridge vegetation, which was tundra, without shrubs or trees, with bare ground, and comparable to Bering land bridge tundras found further north. There was no coastal mild or wet strip. Plant associations comparable to those of the modern Aleutians or Pribilofs probably did not exist along the land bridge coast and the region was probably not suitable for breeding by fur seals and other marine mammals. A cold, dry, continental air-mass system reached to the coast itself. The south land bridge coast did not offer an environment to aboriginal human populations that was significantly milder than that of the land bridge plains to the north. At about 11,000 yr B.P. the Wisconsin dry climate was replaced by a regimen comparable to that at the modern tree line of the interior, and this climate in turn was replaced with the modern system at about 9500 yr B.P. Climatic change was independent of fluctuating sea level.