SEA LEVEL AND CLIMATE HISTORY OF THE DELMARVA PENINSULA OVER THE PAST 40,000 YEARS: A RADIOCARBON DATE PERSPECTIVE

Radiocarbon (RC) dates from organic sediments in coastal deposits have been used to track sea levels and periglacial deposition over the past 40,000 years in the middle Atlantic Coastal Plain. The Delaware Geological Survey Radiocarbon Database contains 514 radiocarbon dates from the Delmarva Peninsula collected from offshore, coastal, and upland depositional environments. Evaluating the geographic distribution, depositional environment, and elevation of the samples, coupled with pollen data, have highlighted the following observations regarding Holocene and late Pleistocene sea level and climate history of the Delmarva Peninsula: 1) Organic sedimentation was continuous in the region throughout the last 40,000 yrs., but was geographically variable as follows (observations 2-5). 2) RC dates from Holocene coastal and offshore deposits mark the rise of sea level since 12,000 yrs B.P. 3) Samples from beneath modern coastal and offshore deposits yield dates between 22,000 and 40,000 yrs B.P. Limited pollen data suggest that these dates from are from non-marine periglacial bogs and not marine deposits as has been previously assumed. 4) Periglacial organic deposition on the uplands in the Cypress Swamp Fm. and adjacent to modern streams was active between 15,000 and 40,000 yrs B.P., was less active between 10,000 and 15,000 yrs B.P., and was not active between 8,000 and 4,000 yrs B.P. The period of non-deposition may coincide with a period of dry conditions during the early Holocene documented elsewhere in North America. 5) Modern swamp deposition in the uplands began about 4,000 yrs B.P. and continues until the present.