Figure 2. Map of end moraines (black polygons) and submerged ridges (dashed lines) in southern New York and New England (modified from Gustavson and Boothroyd, 1987) with study-area location (red polygon). The Ronkonkoma-Block Island-Nantucket end moraine represents the maximum advance of the Laurentide Ice Sheet about 20,000 to 24,000 years ago, while the Harbor Hill-Roanoke Point-Charlestown-Buzzards Bay end moraine, of which a submerged segment crosses through the study area, represents a retreated ice-sheet position from about 18,000 years ago (Uchupi and others, 2001).