Abstract

Ice-margin retreat, glacial processes, and associated marine environmental conditions were investigated along a tidewater margin of the Laurentide ice sheet in eastern coastal Maine. The ubiquitous presence of recessional moraines that typically show crosscutting relationships indicates that numerous stillstands and readvances interrupted net ice-margin retreat. Commonly, moraines exhibit changes in orientation associated with elevation changes, suggesting topographic control on retreat. Till, glaciofluvial facies, and glaciomarine sediment are the dominant components of the moraines. These sediments show that the ice terminated in the sea and that glacial meltwater played a key role in their deposition. The most continuous landforms in the study area are the Pond Ridge moraine and Pineo Ridge moraine system. Both landforms crosscut older moraines and contain ice-shove features, and crosscutting of moraines exists within the Pineo Ridge moraine system, indicating that the ice sheet readvanced during their formation. The Pond Ridge moraine and Pineo Ridge moraine system are straighter across elevation changes, compared to other moraines in the area, implying that during their formation, topography had less of a destabilizing influence on ice-margin dynamics. Foraminifera, Ostracoda, and mollusk species in ice-proximal and ice-distal glaciomarine sediments indicate that arctic to subarctic climatic conditions existed during deglaciation. Despite the persistence of a cold environment, 20 km of net ice-margin retreat occurred between ca. 14 000 and 13 000 14C yr B.P., mostly in contact with the sea.

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