Integrated high-precision analyses of Holocene relative sea-level changes: Lessons from the coast of Maine

Abstract

A suite of salt-marsh peat samples from four sites along the coast of Maine (Wells, Phippsburg, Gouldsboro, and Machiasport) has been analyzed using high-precision techniques to determine local relative sea-level trends and to evaluate proposed along-coast warping. A spatially variable set of relative sea-level records in Maine would have important implications for geophysical models that predict the response of the lithosphere during deglaciation and postglacial isostatic relaxation. The amplification of M{sub 2} tidal range in the Gulf of Maine and the Bay of Fundy during the Holocene is modeled and applied to the mean high water data yielding best-estimate envelopes of mean tide level change for each location. Average long-term (thousands of years) mean tide level rise did not exceed {approx}2 mm/yr at any time during the late Holocene at Wells, Phippsburg, and Machiasport. Between 4.5 and 3 ka (calibrated [cal]), the apparent rate of rise at Gouldsboro was higher than at any other site studied. This along-coast variation in the rate of mean tide level rise may reflect time of deglaciation, neotectonics, or differential isostatic adjustments. A slight acceleration of mean tide level rise has occurred during the past millennium in Gouldsboro and Machiasport. If 12 m downwarping inmore » easternmost Maine occurred, as suggested in other publications, it must have happened prior to 5.7 ka(cal). 84 refs., 13 figs., 8 tabs.« less