POSTGLACIAL STRIGRAPHY AND EVOLUTION OF MAINE LAKES

Maine contains a wide variety of lakes created by glacial scour and deglacial damming. There are more than 6000 lakes and ponds in Maine ranging from high mountain tarns, to bedrock-controlled lakes and river drainage, to drift-dammed lakes. Our colleagues in the UMaine Climate Change Institute study paleoecological data in lakes, such as pollen and macrofossils of vegetation, which document wet and dry cycles, lake-level changes, and vegetation changes. Some coastal lowland lakes are isolation basins, recording a change from deglacial marine to isostatically rebounded freshwater settings. We have studied eight lakes in reconnaissance and detailed investigations using seismic profiling, sidescan sonar, and core sampling. Moosehead Lake, the largest in Maine, contains a submerged esker, glaciomarine, and postglacial lacustrine sediments. It is large enough that regional isostatic tilt is recognized in uplifted and submerged shorelines. Sebago Lake has a similar record but also extensive slumps and basinal slump run-out deposits, suggesting instability in early post-glacial times. We are studying Rangeley and Mooselookmegunticook Lakes in NW Maine to characterize their fishing habitats, stratigraphy, and potential isostatic tilt record. Lobster Lake in north-central Maine formed around a prominent kettle hole basin, and today receives input from springtime flow from the flooding West Branch Penobscot River, forming a reverse-flow delta at its outlet. Sebasticook Lake is notable for geoarchaeological studies of a mid-Holocene fishing weir site and low lake-level shorelines. Finally, Pemaquid Lake and Biscay Pond are coastal lakes with a record of glaciomarine sedimentation followed by emergence and isolation by uplift. They form analogues for the nearby Damariscotta River estuary, which saw a similar isolation, but then was subsequently resubmerged by the Holocene transgression. Many Maine lakes and ponds record an early Holocene low-lake level recorded in lowstand shorelines and wave-abrasion platforms (8-12 m in Moosehead, Sebago, Sebasticook, and other studies) that is an important link to paleoecological climate indicators, as well as a potential record of regional isostatic tilting, and evaluation of the passage of a glacial forebulge.