19 Ice sheets, glaciers, and landscapes, oh my!

Glaciers and ice sheets shaped the landscape of the Northeast. Ice continues to shape the landscape of alpine and polar regions. We welcome submissions on glaciers &  ice sheets of any size, shape, age, and location.

Monday, 23 March 2026
8:00 AM - 12:00 PM
CCC, Room 26

New chronostratigraphy from glacial deposits in southern New England reveals major MIS5-4 Laurentide ice sheet advance

Paper number: 19-12
Program: Technical Sessions
Time: 11:40 AM – 12:00 PM

Authors

Abstract

Glaciotectonically deformed strata making up a belt of islands in southernmost New England contain a uniquely preserved archive of Pleistocene glacial history that records multiple ice sheet advance-retreat cycles. The deformed glacial deposits, or Lower Drift, comprise two distinct regional ice sheet advance-retreat cycles that are poorly constrained in age and sit stratigraphically below an upper undeformed ablation till, or Upper Drift, corresponding to a third ice sheet advance-retreat cycle. The Upper Drift was deposited during initial retreat of the Laurentide Ice Sheet at the Last Glacial Maximum (LGM) and has been assigned cosmogenic exposure dates of 27–22 ka. We implement Optically Stimulated Luminescence (OSL) dating from the Lower Drift to constrain the age of regional ice sheet advances prior to the LGM. Ten OSL samples yielding dates from quartz (7) and feldspar (3) aliquots from eastern Long Island (NY), Block Island (RI), Cuttyhunk Island (MA), and Martha’s Vineyard (MA) form age clusters above and below a regional erosional unconformity separating lithologically distinct pre-LGM glacial units. The basal glacial deposits of the Lower Drift (Jameco and Gardiner’s Clay formations) are dated at 80-60 ka and are overlain by glacial deposits (Jacob’s Sand, Montauk, and Hempstead formations) dated at 30-20 ka. The 80-60 ka deposits are associated with a nearly continuous sequence of ~1500 rhythmites from a pro-glacial lake that are interpreted to be annual varves. The chronostratigraphy suggests that the Laurentide ice sheet advanced to near its LGM extent at the MIS5a-MIS4 transition. The distinct ice advance-retreat cycle represented by the Montauk Formation and its bounding units at 30-20 ka is interpreted to immediately pre-date the overlying 27–21 ka ablation till of the Upper Drift. We integrate the newly identified regional record an MIS5a-4 ice sheet advance with geological evidence of broader continental Laurentide ice sheet advance at that time. Further linkages to cooling and sea ice expansion at the MIS5a-MIS4 boundary from North Atlantic deep-sea records indicate that regional ice-sheet expansion is associated with significant weakening of the AMOC comparable to the LGM and related to a global cooling event.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411496

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