A 443.9-m-thick, virtually undisturbed section of postimpact deposits in the Chesapeake Bay impact structure was recovered in the Eyreville A and C cores, Northampton County, Virginia, within the “moat” of the structure's central crater. Recovered sediments are mainly fine-grained marine siliciclastics, with the exception of Pleistocene sand, clay, and gravel. The lowest postimpact unit is the upper Eocene Chickahominy Formation (443.9–350.1 m). At 93.8 m, this is the maximum thickness yet recovered for deposits that represent the return to “normal marine” sedimentation. The Drummonds Corner beds (informal) and the Old Church Formation are thin Oligocene units present between 350.1 and 344.7 m. Above the Oligocene, there is a more typical Virginia coastal plain succession. The Calvert Formation (344.7–225.4 m) includes a thin lower Miocene part overlain by a much thicker middle Mio-cene part. From 225.4 to 206.0 m, sediments of the middle Miocene Choptank Formation, rarely reported in the Virginia coastal plain, are present. The thick upper Miocene St. Marys and Eastover Formations (206.0–57.8 m) appear to represent a more complete succession than in the type localities. Correlation with the nearby Kiptopeke core indicates that two Pliocene units are present: Yorktown (57.8–32.2 m) and Chowan River Formations (32.2–18.3 m). Sediments at the top of the section represent an upper Pleistocene channel-fill and are assigned to the Butlers Bluff and Occohannock Members of the Nassawadox Formation (18.3–0.6 m).

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.