QUATERNARY MAPPING IN NEW ENGLAND AND GLACIAL SEDIMENTARY PROCESSES AT ACTIVE ICE MARGINS, NORTHEAST GULF OF ALASKA: A SYNERGY

Quaternary glacial mapping of Laurentide Ice Sheet deposits in New England has been greatly aided by an understanding of glacial and sedimentary processes occurring at and near the margins of large piedmont glaciers along the northeast Gulf of Alaska, most notably the Bering and the Malaspina. Likewise, a greater understanding of sedimentary processes at active ice margins of the Alaskan glaciers was gained by answering questions posed by mapping in New England. The modern connection between sedimentary processes in Alaska and glacial deposits in New England began with Hartshorn (1958), continued with the MA/SC/TX/RI group in the late 1960s and 1970s at the Malaspina Glacier, and is active today with the New York group at the Bering Glacier.

Some specific issues addressed in both Alaska and New England were and are: 1) the source of meltwater and sediment delivered to the proglacial alluvial fans and deltas and lacustrine fans, 2) sedimentary processes on slopes of lacustrine deltas, 3) nature of glacial lacustrine rhythmite sedimentation, 4) sedimentation of lacustrine fans, 5) complexity of esker sedimentation, 6) relation of clast size to alluvial fan gradient, 7) the processes of non-lodgment till sedimentation, 8) specifics of morphosequence development, 9) ice-margin fluctuations and surges.

For instance, ongoing Quaternary glacial mapping in Rhode Island in support of the StateMap program have made use of clast size/fan gradient relationships to map stratified deposits in heavily urbanized areas with few exposures. An understanding of lacustrine fan/esker sedimentation and subglacial sources of meltwater has led to a correct interpretation of borehole stratigraphy in support of the Providence River (RI) dredged-material placement in confined aquatic disposal cells.