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SOUTHEAST-DIRECTED BACKTHRUSTING AND CRUSTAL THICKENING IN THE MASSANUTTEN SYNCLINORIUM: ROCKINGHAM AND PAGE COUNTIES, VIRGINIA. Matthew HELLER, Steven WHITMEYER, Christopher HOLLAND, David ARNETTE, Mark CARTER, and Lorrie COINER. Virginia Department of Mines, Minerals and Energy
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SOUTHEAST-DIRECTED BACKTHRUSTING AND CRUSTAL THICKENING IN THE MASSANUTTEN SYNCLINORIUM: ROCKINGHAM AND PAGE COUNTIES, VIRGINIA Matthew HELLER, Steven WHITMEYER, Christopher HOLLAND, David ARNETTE, Mark CARTER, and Lorrie COINER Virginia Department of Mines, Minerals and Energy Division of Mineral Resources James Madison University Department of Geology and Environmental Sciences
Laurentian Realm Axial Realm Piedmont Goochland Peri-Gondwanan Realm Carolina
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Charlottesville and Front Royal 30- x 60 Minute Quadrangles West of Blue Ridge (Rader and Gathright, 2001) 10miles
Devonian shale Siluro-Devonian silt / sandstone Silurian sandstone Ordivician shale / sandstone Cambro-Ordivician carbonate Brent (1960) and Allen (1966) 1 1 2 2 5miles
Rader and Gathright (2001) Devonian shale Siluro-Devonian silt / sandstone Silurian sandstone Ordivician shale / sandstone Cambro-Ordivician carbonate 1 1 5miles
Northwest portion of Elkton West 7.5’ quadrangle 2 miles
NW SE
Northwest portion of Elkton West 7.5’ quadrangle 2 1 1 2 miles
NE Page Valley Laird Knob 2 3 Page Valley Laird Knob
Looking NE Page Valley Laird Knob
SW Laird Knob 1 2nd 1st Laird Knob 1 2nd 1st
Bedding Overturned Bedding n=64 Cleavage n=17 n=45 2 miles
Bedding Overturned Bedding n=64 Cleavage n=17 n=57 2 miles
SE NW Looking NE
Millboro / Needmore Wills Creek / Bloomsburg Massanutten Upper Martinsburg Lower Martinsburg Edinburg Lincolnshire / New Market Beekmantown Conococheague Southeast portion of Tenth Legion 7.5’ quadrangle 2 miles
NW SE
CONCLUSIONS • 1:24,000-scale mapping confirms the existence of a significant backthrust in Page and Rockingham counties • Displacement along this fault may be up to 1 km • Minor structures suggest additional displacement within the footwall • Backthrusting clearly post-dates development of northwest vergent folds and locally changes the vergence of the Massanutten Syncline • Crustal thickening due to backthrusting may be a factor in the present day relief of the Massanutten range
ACKNOWLEDGEMENT Mapping for this project was completed under the STATEMAP Program with assistance from the U.S. Geological Survey