DEGLACIAL TO HOLOCENE SEDIMENTARY RECORDS FROM CHESAPEAKE BAY

Multiproxy data from a radiocarbon-dated sediment core collected off the mouth of the Patuxent River in Chesapeake Bay provide a detailed record of terrestrial and estuarine response to climate and sea-level changes during the last ~18 ka. Core MD03-2663 was collectedby the R/V Marion Dufresne at 37 m water depth in the mainstem of Chesapeake Bay and recovered 17 m of sediments. Pollen assemblages throughout the core are dominated by either Pinus or Quercus pollen, but significant fluctuations in abundance of subdominant pollen types suggest forest responses to climate changes associated with the last deglaciation. The basal 3.5 m consists of massive, coarse sands, and Picea, Abies, and Pinus banksiana are common elements of pollen assemblages. Pinus strobus, indicating warmer, wetter conditions, is abundant in assemblages isolated from massive sands between 11 m and 13.5 m; based on radiocarbon dating, we tentatively correlate this unit with the Bølling-Allerød. Pollen of Pinus banksiana, Picea, and Abies, indicating a return to cooler and drier conditions, are more abundant between 11 and 8.8 m; radiocarbon dates of woody fragments isolated from the sands and silty clays of this unit indicate that it represents the Younger Dryas. This unit appears to be conformably overlain by 6.5 m of laminated early Holocene sediments with abundant pollen of Tsuga, Carya, and other temperate hardwoods. Pinus-dominated assemblages in the upper 2.3 m of the core were deposited during the late Holocene, and Ambrosia abundance indicates that the upper 1.1 m was deposited after Colonial land clearance. These data document the response of forest communities fluvial/estuarine sedimentation to climate associated with the deglaciation and early Holocene sea-level rise that formed the modern Chesapeake Bay estuary.