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Washington County
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Diabase Sills and Dikes (Triassic) Pinesburg Station Dolomite (Ordovician) Rockdale Run Formation (Ordovician) Stonehenge Limestone (Ordovician) Conocheague Limestone (Cambrian) Elbrook Limestone (Cambrian) Waynesboro Formation (Cambrian) Tomstown Dolomite (Cambrian) Antietam Formation (Cambrian) Harpers Formation (Cambrian) Weverton Formation (Late Precambrian ?) Loudoun Formation (Late Precambrian ?) Metarhyolite and Associated Pyroclastic Sediments (Late Precambrian ?) Catoctin Metabasalt (Late Precambrian ?) Granodiorite and Biotite Granite Gneiss (Precambrian)
Pocono Group (Mississippian) Hampshire Formation (Devonian) Chemung Formation, Parkhead Sandtone, Ballier Formation & Harrell Shale (Devonian) Hamilton Group, Tioga Metabentonite Bed & Needmore Shale (Devonian) Oriskany Group (Devonian) Helderburg Formation & Keyser Limestone (Devonian) Tonoloway Formation (Silurian) Wills Creek & Bloomsburg Formations (Silurian) McKenzie Formation (Silurian) Clinton Group (Silurian) Tuscarora Sandstone (Sulurian) Juniata Formation (Ordovician) Martinsburg Formation (Ordovician) Chambersburg Limestone (Ordovician)  
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