Prepared in cooperation with the Maryland Geological Survey Geologic Map of the Frederick 30’ × 60’ Quadrangle, Maryland, Virginia, and West Virginia By Scott Southworth, David K. Brezinski, Avery Ala Drake, Jr., William C. Burton, Randall C. Orndorff, Albert J. Froelich, James E. Reddy, Danielle Denenny, and David L. Daniels Pamphlet to accompany Scientific Investigations Map 2889 2007 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Dirk Kempthorne, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: 2007 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Cover: Color-shaded-relief image of the Frederick 30´ × 60´ quadrangle showing high topographic elevations in shades of red and low topographic elevations in shades of blue. The hillside is illuminated from the east. The highest elevation is 1,920 ft above sea level on Blue Ridge at the southwestern part of the map area in Loudoun County, Va., and the lowest elevation is 140 ft above sea level along the Potomac River at Great Falls, Montgomery County, Md. The higher elevation regions, such as the ridges of the Blue Ridge province, portions of the Great Valley of the Valley and Ridge province, and Sugarloaf Mountain and parts of the Westminster terrane in the Piedmont province, are in contrast to the lower elevation region of the Culpeper and Gettysburg basins, Frederick Valley, and Potomac River val- ley within the Piedmont province in the eastern half of the map area. The elevation differences are a function of rock hardness and different erosion histories. Image produced by David L. Daniels, USGS, using a 5-m digital elevation model of USGS. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to repro- duce any copyrighted materials contained within this report. Suggested citation: Southworth, Scott, Brezinski, D.K., Drake, A.A., Jr., Burton, W.C., Orndorff, R.C., Froelich, A.J., Reddy, J.E., Denenny, Dani- elle, and Daniels, D.L., 2007, Geologic map of the Frederick 30´ × 60´ quadrangle, Maryland, Virginia, and West Virginia: U.S. Geological Survey Scientific Investigations Map 2889, scale 1:100,000, 42-p. text. ISBN 978-1-4113-1165-7 iii Contents Introduction.....................................................................................................................................................1 Great Valley Section of the Valley and Ridge Province ...........................................................................2 Geologic Setting ....................................................................................................................................2 Lower Paleozoic Sedimentary Rocks .......................................................................................4 Tomstown Formation ..........................................................................................................4 Waynesboro Formation ......................................................................................................4 Elbrook Limestone ..............................................................................................................4 Conococheague Limestone and Big Spring Station Member ....................................4 Beekmantown Group .............................................................................................................4 Stonehenge Limestone and Stoufferstown Member ....................................................4 Rockdale Run Formation ....................................................................................................4 Pinesburg Station Dolomite ..............................................................................................5 St. Paul Group ......................................................................................................................5 Chambersburg Limestone .................................................................................................5 Martinsburg Formation .....................................................................................................5 Structure.................................................................................................................................................5 Metamorphism ......................................................................................................................................5 Blue Ridge Province ......................................................................................................................................5 Geologic Setting ....................................................................................................................................5 Mesoproterozoic Rocks ..............................................................................................................6 Neoproterozoic Rocks ................................................................................................................6 Cobbler Mountain Alkali Feldspar Quartz Syenite of the Robertson River Igneous Suite .........................................................................................................6 Metasedimentary Rocks of the Fauquier Group and Swift Run Formation ...............6 Metadiabase and Metarhyolite Dikes .............................................................................7 Metavolcanic and Metasedimentary Rocks of the Catoctin Formation ....................7 Paleozoic Clastic Metasedimentary Rocks of the Chilhowee Group ..................................7 Loudoun Formation .............................................................................................................7 Weverton Formation ...........................................................................................................7 Harpers Formation ..............................................................................................................8 Antietam Formation ............................................................................................................8 Carbonaceous Phyllite .......................................................................................................8 Tomstown Formation East of Catoctin Mountain ...........................................................8 Structure.................................................................................................................................................8 Mesoproterozoic ..........................................................................................................................8 Neoproterozoic ............................................................................................................................8 Paleozoic .......................................................................................................................................9 Folds ......................................................................................................................................9 Cleavage ...............................................................................................................................9 Faults .....................................................................................................................................9 Mesozoic .......................................................................................................................................9 Metamorphism ......................................................................................................................................9 iv Mesoproterozoic ..........................................................................................................................9 Paleozoic .....................................................................................................................................10 Piedmont Province.......................................................................................................................................10 Geologic Setting ..................................................................................................................................10 Culpeper and Gettysburg Basins ............................................................................................10 Chatham Group .....................................................................................................................10 Manassas Sandstone ......................................................................................................10 Bull Run Formation ...........................................................................................................11 Catharpin Creek Formation .............................................................................................11 Mount Zion Church Basalt ..............................................................................................11 Meriden Group ......................................................................................................................11 Midland Formation ............................................................................................................11