Late-Pleistocene fluctuations of sealevel and postglacial crustal rebound in coastal Maine

Abstract

Deglaciation and postglacial crustal rebound near Portland, Maine, took place during a time of generally rising sea level. The relative positions of land and sea level at several points in time are indicated in part by: 1) glacial-fluvial deposits buried by marine silty clay to depths of 70 ft below present sea level, 2) radiocarbon-dated shells from emerged marine beds 160-250 ft above present sea level, 3) pollen-stratigraphic profiles of coastal sites underlain by marine sediment, which lack the late-glacial and early postglacial portion of the record, and 4) submerged tree stumps dating back to 4200 yr B.P. The position of a reference point in Maine with respect to changing sea level is graphically shown, using several alternative interpretations of late-Pleistocene eustatic rise of sea level as base lines. Only one of the constructions can be reasonably interpreted in terms of postglacial crustal rebound, demonstrating that areas of known crustal deformation can be useful in interpreting eustatic sea-level fluctuations.