A CONTINUOUS RECORD OF LATE QUATERNARY CLIMATE AND ENVIRONMENTAL CHANGES FROM THE DELAWARE COASTAL PLAIN

The mid-Atlantic region experienced dramatic environmental changes during the late Quaternary because of its position immediately south of the Laurentide Ice Sheet margin. However, there are a limited number of continuous records of Late Quaternary paleoenvironmental information from the region. We have been working to develop records from late Pleistocene to Holocene wetland sediments within the Delaware Coastal Plain. Our study has focused on the Cypress Swamp Formation, a deposit spanning 145 km² composed primarily of silty sands, but with distinct and laterally continuous organic-rich horizons. In order to characterize the overall accumulation of this sedimentary sequence, we evaluated published mapping and the stratigraphic position of 42 published and unpublished radiocarbon dates taken from throughout the deposit. Detailed stratigraphic analysis was also conducted on a 9 m sediment core from the center of the site, including grain size, organic matter, organic carbon, nitrogen values, and plant wax biomarkers. We identify a distinct organic-rich unit at the base of the sequence deposited from c. 39 to 23 cal ka BP. Organic carbon values generally range from 2-6%, C/N values are consistently greater than 20, and the concentrations of mid- versus long-chain length n-alkanes vary with changes in C/N values. Distinct trends are apparent in the data which show a high degree of variability, particularly from 39 to 32 cal ka BP when C/N values are the highest. A sharp drop in organic carbon and the onset of aeolian sand deposition occurs at c. 23 cal ka BP, a period of time marked by the onset of rapid accumulation throughout the Cypress Swamp Formation, which continued into the early Holocene. We correlate changes in our data to important climate oscillation of late Marine Isotope Stage 3 and the onset of the last glacial maximum to interpret environmental changes in the mid-Atlantic during the late Quaternary. Overall, our data provide new evidence of regional climate changes linked to Northern Hemisphere variations, and expand knowledge of paleoclimate within this region.