Palynological and stratigraphic investigations of four deep wells in the Salisbury Embayment of the Atlantic Coastal Plain

Abstract

Use of palynological zones defined by Brenner and Doyle from the Cretaceous outcrop belt in Maryland, Delaware, and New Jersey permit correlation of the Cretaceous section in four wells drilled to basement in the Salisbury Embayment in the Eastern Shore of Maryland and in Accomack Co., Virginia. These correlations, supplemented by electric log correlations between wells, clarify the Mesozoic depositional history of the outer margin of the Atlantic Coastal Plain. The bulk of the Cretaceous section consists of continental to marginal is marine sediments correlative with and probably older than the outcrop Potomac Group (Aptian-lower Cenomanian?). Lower Cretaceous palynlogical assemblages also occur in at least the top of basal "red beds" considered Triassic or Jurassic by earlier authors. Dinoflagellates and lithological criteria indicate several transgressive-regressive cycles within the generally transgressive Potomac sequence, with maximum marine incursions in the Late Albian and the Early Cenomanian. Equivalents of the lower Raritan Formation of New Jersey (middle-upper Cenomanian?), absent at the Maryland outcrop, are recognized for the first time in the Taylor and Bethards wells. Potomac and lower Raritan equivalents are separated from overlying Magothy equivalents (upper Santonian-lower Campanian) by a major regional unconformity. Well data suggest that further downdip, under the continental shelf, most of the formations should be marine and contain abundant organic matter. Given sufficient heat and trapping structures, oil and gas may have accumulated.