Abstract

Within a 50-km segment of the coast of Connecticut, the discovery of two discontinuous late Wisconsin end moraines — the Old Saybrook moraine and the Madison moraine — extends existing knowledge of end moraines that occur to the east. The moraines trend N75°E, which is oblique to the coast; the Old Saybrook moraine intersects the coast farther east than the Madison moraine.

Offshore, within an area of about 235 km2, a study of the bottom and subbottom by acoustic-reflection profiling has revealed a probable westward continuation of the Old Saybrook moraine. The 18-km-long continuation was recognized by its form and by concentrations of large boulders. Bedrock shoals were differentiated from shoals believed to be end moraine according to (1) absence of surface boulders and (2) greater relief than that which would be expected on drift reworked by surf and currents during postglacial submergence.

Increased width of the Old Saybrook moraine at the mouth of the Connecticut River may indicate an ice stream within the former ice sheet. The newly identified moraines fit reasonably into the general framework of similar features between New Jersey and Cape Cod. North of the moraines and parallel with them, is a belt within which ice-contact stratified drift merges into outwash. This belt is believed to approximate a glacier terminus of later date, when the glacial regimen was less active. Search of the Connecticut region north of this line has not thus far yielded evidence of later positions of a discrete margin of the former ice sheet.

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