JUNEAU ICEFIELD GLACIAL REGIME APPLIED TO LAURENTIDE RETREAT FROM CENTRAL NEW YORK STATE

Temperate valley glaciers, originating on the Juneau Icefield are known to deposit rock debris in a variety of diverse environments. Foreland tidal fans, outwash valley train, ice-contact lakes, and ice-cored, terminal remnants are all present. These environments and associated depositional conditions serve as current analogs for deposition during retreat of the Laurentide Ice Sheet from central New York State.

The Taku Glacier, with the largest and highest area of accumulation, represents an active ice regime that depicts conditions interpreted to have existing within Appalachian Plateau through valleys, circa 13,000 – 14,000 yrs BP. Moderately high continental relief strongly influenced the shape of the retreating temperate ice front, with salients ice tongues and recessional divides. Nourished by the ice sheet and its associated hydrologic system, 20 km-long ice tongues issued high-volume melt water forming well-sorted, gravel aquifers within widespread outwash. In contrast, non-through valleys starved of nourishment were sites of remnant and stagnant ice similar to detached ice blocks found in the proglacial environment of Herbert Glacier.

Water well logs from virtually all valleys indicate thick lacustrine sediments accumulated in ice-contact lakes that grew headward along the retreating termini of valley tongues, much like Mendenhall Glacier calving into Mendenhall Lake. Analog sediment sources and transport mechanisms common to the Juneau Icefield provide insight for the interpretation of ice marginal depositional conditions during Lauentide retreat.