Northeastern Section - 36th Annual Meeting (March 12-14, 2001)

For the last 14 thousand years, the "rock-bound" coast of Maine has been shaped by the interaction between glacial processes and fluctuating sea levels. Between 13.8 and 13.2 thousand years before present, the Laurentide Ice Sheet which had covered coastal Maine, retreated leaving the sea in its wake. The Maine coast had been isostatically depressed by the ice allowing for a rapid marine transgression. At its highest, sea level in mid-coast Maine rose to approximately 70 meters above the modern level. As the ice retreated and the water rose, the Presumpscot Formation, comprised of glacialmarine mud, was deposited as a drape over the bedrock previously sculpted by glacial activity. As sea level dropped to -60 meters in response to isostatic rebound, the surface of the Presumpscot was eroded. Evidence for sea level change is contained in the sedimentary record of Maine estuaries.

My work this summer focused on the New Meadows River, an elongate, rock-bound estuary in mid-coast Maine. The seismic and sedimentological characteristics of this river were investigated using high-resolution seismic profiles and coring. The purpose of this study was to determine what role sea level fluctuation played in shaping these characteristics. The seismic records from the New Meadows River taken in the summer of 1999 using Datasonics CHIRP sonar equipment shows an unconformity between the erosion surface of the glacialmarine mud of the Presumpscot Formation and a flat lying unit of Holocene mud. This unconformity is seen clearly in three cores taken from tidal flats on the river. Further work will be done to correlate the sedimentological units observed in the sediment cores to the seismic-stratigraphic units in the seismic records.