Accomack Member of Omar Formation (middle Pleistocene, Mixon, 1985). Light-to dark-gray, light-yellowish-gray, brownish-gray, and yellowish-orange sand, gravel, silt, clay, and peat of south west-trending central upland (altitude 38-50 feet) in Accomack County. Upper part of unit is bounded on east and west by ocean- and bay-facing scarps; lower part present in subsurface of adjacent lowland areas where it is overlain unconformably by Upper Pleistocene and Holocene deposits. In northern part of county, unit is a barrier-back barrier sequence of clean, cross-bedded, gravelly sand (above) and peat, clayey silt, and muddy sand (below); mollusks include Crassostrea, Mercenaria, and Noetia. In southern part of county, fine to coarse, trough cross-bedded sands of barrier-spit origin overlie fine- to very-fine-grained, muddy, nearshore-shelf sand containing Spisula, Ensis, Anomia, and Mulinia. At base of unit, pebbly to bouldery, medium- to very-coarse-grained sand and thick, compact clay-silts constitute the fluvial-estuarine fill of a paleochannel of the Susquehanna River system. Accomack Member and underlying channel fill are as much as 200 feet, or more, in thickness.
Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.
Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.