LATE PLEISTOCENE SEQUENCES ON THE NEW JERSEY CONTINENTAL SHELF INDICATE SIGNIFICANT STAGE 3 ICE SHEET DYNAMICS

Two sea-level highstands (3a and 3c) at ~-30m at ~35ka, and ~-20m at ~55ka, and a lowstand (3b) at ~-60m at ~45ka, have been identified from correlated seismic sequences on the New Jersey continental shelf. Correlations were based on ties to nannofossil stratigraphy on the continental slope, pollen indices, foraminifera, amino acid racemization, radio carbon dating, and the age peaks in a temperature-adjusted delta 18 oxygen isotope curve and the Antarctic ice-core methane curves. These oscillations in stage 3 sea levels of 30 to 40m indicate stadial and interstadial events in the last glagial interval (stages 2,3, and 4). Even with these large sea-level changes in stage 3, the pollen indices indicate a cool conifer environment for New Jersey in all three stage 3 intervals, and G. pachyderma foraminifera and Astarte pelecypods indicate cool boreal marine environments throughout stage 3. One explanation for these observations is that the stage 3 northern hemisphere ice sheet dynamics were similar to those changes between ~9ka and ~12ka. According to COHMAP(1988), at 12ka, when sea level was ~-60m similar to stage 3b, the Cordilleran, Laurentide, Greenland, and Fennoscandian ice sheets covered about 21 million square kilometers. Conifer forests and boreal G. pachyderma foraminifera occurred in the New Jersey area. At 9ka, when sea level was at ~-20m to -30m similar to stages 3c and 3b, the Cordilleran ice sheet had lost ~75% of its area, the Fennoscandian lost ~88% area, while the Laurentide only lost ~44% area, and Greenland nil. Because of the lesser northern retreat of the laurentide ice sheet, about 700 linear kilometers, conifer forests still existed near New Jersey at 9ka, and the Greenland influence with the Labrador Current maintained cool boreal marine faunas southward to New Jersey. The extensive losses of the Cordilleran and Fennoscandian ice sheets, assuming thicknesses of 1.0 to 1.5km, contributed significantly to the 30 to 40m sea-level rise between 12ka and 9ka, more than the Laurentide ice sheet contribution. Similar ice sheet dynamics must have occurred during the stage 3 stadials and interstadials.