Late Quaternary sea level change in Southern Beringia: postglacial emergence of the Western Alaska Peninsula

Abstract

Postglacial sea level trends have varied dramatically across the Bering Platform because of differences in coastal and shelf geologic settings. Emergent shorelines and basal peats along the western Alaska Peninsula indicate that relative sea level has fallen since regional deglaciation occurred ca. 13,000 cal. yr BP. Age/elevation determinations on four shorelines (25 m :>10 ka, 16 m : 9.6–6 ka, 6 m : 2.1 ka, and 2–3 m : 1.8–0.6 ka) in the vicinity of Cold and Morzhovoi bays provide an estimate of the pace and timing of of sea level change since the last glacial maximum (LGM, 22–17 ka). Isostatic recovery and shoreline regression following the disintegration of continental and alpine ice has been interrupted by transgressive conditions at least twice since deglaciation. Changes in the balance between eustatic sea level rise and isostatic uplift resulted in the reactivation of marine scarps during the early to middle Holocene, but terrace cutting and a gap in the archaeological record about 2.1 ka suggest that sudden tectonic displacements also influence the record. Reconstructions of coastal paleogeography constrain the timing and distribution of regional archaeological settlement. Periods of shoreline erosion during stillstands or transgressions, and the episodic reorganization of intertidal environments that accompanies tectonic displacements, have conditioned site preservation potential and long-term adaptive strategies.