Figure 4. Location of end moraines (black polygons) and submarine ridges (dashed lines) in southern New York and New England (modified from Gustavson and Boothroyd, 1987) and location of study area (gray polygon). The Ronkonkoma-Nantucket end moraine represents the maximum advance of the Laurentide Ice Sheet about 20,000 years ago and the Harbor Hill-Roanoke Point-Charlestown-Buzzards Bay end moraine represents a retreated ice-sheet position from about 18,000 years ago (Uchupi and others, 1996).