82° 81° 80° 79° 78° EXPLANATION West Virginia county boundaries A West Virginia Geology by map unit Quaternary Modern Reservoirs Qal Alluvium Permian or Pennsylvanian Period LTP d Dunkard Group LTP c Conemaugh Group LTP m Monongahela Group 0 25 50 MILES LTP a Allegheny Formation PENNSYLVANIA LTP pv Pottsville Group 0 25 50 KILOMETERS LTP k Kanawha Formation 40° LTP nr New River Formation LTP p Pocahontas Formation Mississippian Period Mmc Mauch Chunk Group Mbp Bluestone and Princeton Formations Ce Obrr Omc Mh Hinton Formation Obps Dmn Bluefield Formation Dbh Otbr Mbf MARYLAND LTP pv Osp Mg Greenbrier Group Smc Axis of Obs Mmp Maccrady and Pocono, undivided Burning Springs LTP a Mmc St Ce Mmcc Maccrady Formation anticline LTP d Om Dh Cwy Mp Pocono Group Qal Dhs Ch Devonian Period Mp Dohl LTP c Dmu Middle and Upper Devonian, undivided Obps Cw Dhs Hampshire Formation LTP m Dmn OHIO Ct Dch Chemung Group Omc Obs Dch Dbh Dbh Brailler and Harrell, undivided Stw Cwy LTP pv Ca Db Brallier Formation Obrr Cc 39° CPCc Dh Harrell Shale St Dmb Millboro Shale Mmc Dhs Dmt Mahantango Formation Do LTP d Ojo Dm Marcellus Formation Dmn Onondaga Group Om Lower Devonian, undivided LTP k Dhl Dohl Do Oriskany Sandstone Dmt Ot Dhl Helderberg Group LTP m VIRGINIA Qal Obr Silurian Period Dch Smc Om Stw Tonoloway, Wills Creek, and Williamsport Formations LTP c Dmb Sct Lower Silurian, undivided LTP a Smc McKenzie Formation and Clinton Group Dhl Stw Ojo Mbf Db St Tuscarora Sandstone Ordovician Period Ojo Juniata and Oswego Formations Dohl Mg Om Martinsburg Formation LTP nr Otbr Ordovician--Trenton and Black River, undivided 38° Mmcc Ot Trenton Group LTP k WEST VIRGINIA Obr Black River Group Omc Ordovician, middle calcareous units Mp Db Osp St. Paul Group Mh Beekmantown or Lower Ordovician Group Do Ob LTP nr Allegheney and Obps Pinesburg Station Dolomite Mmcc Monongahela Mg Obrr Rockdale Run Formation Basin Osp Obs Stonehenge Formation Cambrian and pre-Cambrian Period KENTUCKY Mbf Otbr Cc Conococheague Formation LTP p Mbp Dh Ob Elbrook Formation Mh Ce Dmt Kanawha- Cwy Waynesboro Formation Mbp Sct Mmp Dm New River WEST Ct Tomstown Dolomite Basin VIRGINIA Ca Antietam Formation Ob Dmu Ch Harpers Formation LTP p Cw Weverton-Loudon Formation CPCc Catoctin Formation 37° Axis of the Burning Springs anticline Base from U.S. Geological Survey digital data, 1:100,000, 1983, Geology from West Virginia Division of Environmental Protection, 1998, Universal Transverse Mercator projection, Zone 18 1:250,000, Universal Transverse Mercator, Zone 17, North American Datum of 1983; based on Cardwell and others, 1968, Geologic Map of West Virginia Figure 3A. Major geologic formations in West Virginia..