Stratigraphy of Miocene through Lower Pleistocene Strata of United States Central Atlantic Coastal Plain

Abstract

Miocene, Pliocene, and Pleistocene strata were deposited in two embayments in the central Atlantic Coastal Plain, the Salisbury to the north and Albermarle to the south. Both embayments underwent local tectonics, and no single area within either has a continuous section. Deposition in both embayments began in early Miocene time. In the Salisbury embayment, the early deposits were largely biogenic (Fairhaven Member of the Calvert Formation), and the center of deposition was located in Maryland. Relatively continuous clastic deposition commenced in the late early Miocene and continued through the middle Miocene (Plum Point Marl Member of the Calvert Formation and the Choptank and St. Marys formations). Deltaic deposition began in the northern part of the embayment, as seen in the Calvert and Kirkwood formations and influenced environments west of the delta lobe. The center of deposition in the Salisbury embayment shifted southward into Virginia during late Miocene time (“Virginia St. Marys” beds) and continued there through the early and middle(?) Pliocene (Yorktown Formation); only the southeastern part of the embayment received sediments in the late Pliocene and early Pleistocene (uppermost part of the “Yorktown” Formation). Environments throughout this time were largely inner shelf (less than 60-m depths), and some marginal-marine to nonmarine intervals. The Albemarle embayment in North Carolina received largely biogenic and biochemical deposition during the early and early middle Miocene (Pungo River Formation). This was followed by uplift in the late middle and late Miocene. Clastic sedimentation started near the Miocene-Pliocene boundary and continued with minor hiatuses throughout much of the Pliocene and into early Pleistocene (Yorktown, uppermost part of the “Yorktown,” Duplin, Croatan, and Waccamaw formations). Some Pungo River strata formed in middle-shelf environments as deep as 100 m; most younger strata were deposited in inner-shelf environments (less than 60-m depth), but some in marginal-marine intervals.

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“…Deposition of the Calvert Formation has been described as muddy inner to middle shelf deposition alternating with heavily fossiliferous shoreface and inner shelf sands (Godfrey and Smith 2010). In the GEWA area, the lower Plum Point Member is interpreted as having been deposited in a protected embayment roughly north of the modern Potomac River, and in an inner shelf setting south of it (Gibson 1982(Gibson , 1983. The prevailing climate during deposition of the formation is thought to have been warmer than the present, with subtropical to warm tropical estuarine and shallow marine waters (Gottfried et al 1994), and a warm temperate coastal flora on land, comparable to that found today on the coasts of South Carolina and Georgia, or along the Gulf of Mexico from Florida to Texas (Berry 1916).…”