The Stratigraphic Record of Oxygen Isotope Stage 5 on the Maryland Inner Shelf

by Marguerite A. Toscano, Univ of South Florida, St. Petersburg, United States,

Document Type: Proceeding Paper

Part of: Coastal Sediments


Present knowledge of Holocene transgressive coastal/shelf systems, while extensive, cannot directly address the effects and consequences of an extended period of relatively high sea levels following a short-lived extreme highstand. Such a scenario occurred during the last interglacial, oxygen-isotope stage 5, leaving peak sea level (substage 5e) deposits landward of the present barrier shoreline, followed by deposition of a thick shelf mud sequence extending from onshore to offshore, that does not fit into Holocene transgressive stratigraphic models. An integration of seismic, lithologic, geochronologic and paleoclimatic evidence from the thick late Pleistocene mud on the Maryland inner shelf revealed the unique nature of last interglacial transgressive-regressive episodes, their sea levels, depositional regimes, and resulting stratigraphy. Lowered, but relatively high, sea levels have implications as to sedimentary sources and depositional environments along what we now view as a sandy, eroding transgressive coast. Late stage 5 deposits on the North Carolina, Virginia, Maryland, Delaware, and New Jersey coasts are all characterized by thick, laminated mud accumulations with thin fossil lenses. Each coastal compartment in this series is proximal to one or more major drainage systems (Susquehanna-Chesapeake, Delaware, and Hudson). One explanation for the mud deposition would involve changes in estuarine dynamics during slightly depressed sea levels, increasing riverine outflow in combination with an excess of glacially-derived fine sediments. These interpretations, along with detailed data, may be applied to modelling the future of the present interglacial.

Subject Headings: Geology | Mud | Seas and oceans | Sediment | Sea level | Drainage systems | Estuaries | Shoreline protection | United States | Maryland | Delaware | North Carolina | Virginia | New Jersey

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