Geologic Map of the National Parks in the National Capital Region, Washington, D.C., Virginia, Maryland, and West Virginia By Scott Southworth and Danielle Denenny Open-File Report 2005–1331 U.S. Department of the Interior U.S. Geological Survey ii U.S. Department of the Interior Dirk Kempthorne, Secretary U.S. Geological Survey P. Patrick Leahy, Acting Director U.S. Geological Survey, Reston, Virginia 2006 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 Suggested citation: Southworth, Scott, and Denenny, Danielle, 2006, Geologic map of the National Parks in the National Capital Region, Washington, D.C., Virginia, Maryland, and West Virginia: U.S. Geological Survey Open-File Report 2005-1331, available only online at: http://pubs.usgs.gov/of/2005/1331/. 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 reproduce any copyrighted material contained within this report. iii Contents Introduction .................................................................................................................................................. 1 Background .................................................................................................................................................. 1 Previous Studies .......................................................................................................................................... 1 Methodology ................................................................................................................................................. 2 Physiographic Setting ................................................................................................................................. 2 Geologic Setting and Chronology ............................................................................................................. 2 Types of Rock ................................................................................................................................................ 4 Isotopic Ages of Rocks, Landforms, and Deposits.................................................................................. 4 Fossils 5 Great Valley of the Valley and Ridge Province......................................................................................... 5 Antietam National Battlefield and National Cemetery, Maryland............................................... 5 Introduction ................................................................................................................................. 5 Geologic Setting.......................................................................................................................... 5 Bedrock ........................................................................................................................................ 5 Tomstown Formation ......................................................................................................... 5 Waynesboro Formation..................................................................................................... 6 Elbrook Limestone ............................................................................................................. 6 Conococheague Limestone ............................................................................................. 6 Structure ...................................................................................................................................... 6 Surficial Deposits........................................................................................................................ 6 Landforms .................................................................................................................................... 6 Blue Ridge Province..................................................................................................................................... 6 Catoctin Mountain Park, Maryland................................................................................................... 6 Introduction ................................................................................................................................. 6 Geologic Setting.......................................................................................................................... 7 Bedrock ........................................................................................................................................ 7 Catoctin Formation ............................................................................................................ 7 Loudoun Formation............................................................................................................ 7 Weverton Formation.......................................................................................................... 7 Harpers Formation............................................................................................................. 8 Structure ...................................................................................................................................... 8 Surficial Deposits........................................................................................................................ 8 Landforms .................................................................................................................................... 8 Western Piedmont Province....................................................................................................................... 8 Monocacy National Battlefield, Maryland ...................................................................................... 8 Introduction ................................................................................................................................. 8 Geologic Setting.......................................................................................................................... 9 Bedrock ........................................................................................................................................ 9 Ijamsville Phyllite ............................................................................................................... 9 Araby Formation................................................................................................................. 9 Frederick Formation .......................................................................................................... 9 Structure ...................................................................................................................................... 9 iv Surficial Deposits........................................................................................................................ 9 Landforms .................................................................................................................................... 9 Manassas National Battlefield Park, Virginia............................................................................... 10 Introduction ............................................................................................................................... 10 Geologic Setting........................................................................................................................ 10 Bedrock ...................................................................................................................................... 10 Groveton Member of the Bull Run Formation ............................................................. 10 Diabase.............................................................................................................................. 10 Thermally Metamorphosed Rocks................................................................................ 10 Structure .................................................................................................................................... 10 Surficial Deposits...................................................................................................................... 10 Landforms .................................................................................................................................. 10 Eastern Piedmont Province....................................................................................................................... 11 Prince William Forest Park, Maryland ........................................................................................... 11 Introduction ............................................................................................................................... 11 Geologic Setting........................................................................................................................ 11 Bedrock ...................................................................................................................................... 11 Mafic and Ultramafic Rocks .......................................................................................... 11 Phyllite11