Omar Formation - Accomack Member: (VAQoa;0)

State	Virginia
Name	Omar Formation - Accomack Member:
Geologic age	Quaternary
Original map label	Qoa
Comments	Accomack Member; Coastal Plain, East of Chesapeake Bay From expanded explanation (ref. VA002): 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.
Primary rock type	sand
Secondary rock type	gravel
Other rock types	silt; clay or mud; peat
Lithologic constituents	Minor Unconsolidated > Peat Unconsolidated > Fine-detrital > Clay Unconsolidated > Fine-detrital > Silt Unconsolidated > Coarse-detrital > Gravel Unconsolidated > Coarse-detrital > Sand
Map references	Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/ [https://www.dmme.virginia.gov/commerce/]
Unit references	Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000 Digital Representation of the 1993 Geologic Map of Virginia - expanded explanation: 2003, Commonwealth of Virginia, Department of Mines, Minerals, and Energy, Divsion of Mineral Resources, Publication 147, 85 pp Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/ [https://www.dmme.virginia.gov/commerce/]
Geographic coverage	Accomack