Coastal Response to Late Pliocene Climate Change

Abstract The middle Atlantic Coastal Plain records the late Pliocene transition from typical marine deposition and coastlines of the Tertiary to that of fluvial-estuarine-marine of the Quaternary. The Early Pliocene Yorktown Formation (4.5-3.0 Ma) and Late Pliocene Chowan River Formation (approx. 2.8 Ma) record dominantly marine deposition in temperate to warm temperate climates with moderate- to low-sedimentation rates in a tectonically controlled basin. The Late Pliocene Bacons Castle Formation in Virginia (2.3-2.0 Ma) and the upper Beaverdam Formation of Delaware (2.3-2.0 Ma?) contain deposits with indicators of high rates of sedimentation, abundant sediment supply, an Appalachian source, and a cool terrestrial climate. Deposition was in response to a colder climate in the source area associated with Northern Hemisphere glaciation at approximately 2.4 Ma. Mechanical weathering and colluviation during a colder period moved sediment into the transport system that was later moved and deposited by high-discharge streams flowing into the coastal plain during subsequent warming. Deposition during the ensuing transgression kept pace with sea-level rise with some progradation of coastline. Later, Quaternary erosion and deposition in the region incised and partially reworked these late Pliocene deposits.