EVIDENCE FOR LATE OIS3 ABRUPT CLIMATE CHANGE PRESERVED IN THE DELMARVA PENINSULA STRATIGRAPHIC RECORD

Several late Pleistocene stratigraphic units on the Delmarva Peninsula of the mid-Atlantic Coastal Plain provide evidence for abrupt climate and landscape change in the eastern United States. The upper 1.5 m of the emergent, estuarine Kent Island Formation and the marginal-marine, Sinepuxent Formation represent a period of relatively high sea level during OIS3. The younger and locally superjacent basal peats and eolian sand of the Parsonsburg Sand provide direct evidence of a colder and drier climatic interval during which wind was the dominant physical force of erosion and deposition. Radiocarbon and luminescence age data indicate depositional periods from ~35-30 ka for the uppermost Kent Island and Sinepuxent formations and from ~30-13 ka for the Parsonsburg Sand. Fossil pollen assemblages at the base of the Parsonsburg Sand indicate that a pine-birch vegetation locally intermixed with ponds and bogs was present at ~30 ka. Colder taiga or forest tundra assemblages developed in the Parsonsburg by ~26 ka based on a marked increase in spruce (>20% of pollen sum) and the co-occurrence of alder, Dryas, birch, grasses and sedge. Initiation of eolian activity on the Delmarva Peninsula, and in southern Maryland west of Chesapeake Bay at ~30 ka was approximately coincident with initiation of rapid incision of the region’s major rivers and with GS5 and Heinrich Event 3, an extremely cold period in the North Atlantic Ocean, and is within the period of rapid onset of Laurentide Ice Sheet expansion. The combined sedimentologic, stratigraphic, palynologic, and age data for these late Pleistocene units indicate abrupt changes in climate, sea-level, and landscape-affecting processes in late OIS3 in the mid-Atlantic region. We suggest that the uppermost Kent Island Formation, the Sinepuxent Formation, and the lowermost eolian sand and peat of the Parsonsburg Sand provide a mid-Atlantic continental-margin record that can be compared to the chronology of the Dansgaard-Oeschger and Heinrich events observed in the North Atlantic marine and ice-core records.