U.S. Geological Survey: Science for a Changing World - USGS visual identifier and link to main Web site at http://www.usgs.gov/

Geologic map of parts of the Westminster and Potomac terranes, Maryland, Virginia, and Washington, D.C. For a more detailed explanation, contact Michael Kunk at mkunk@usgs.gov.      Figure 2. Geologic map of parts of the Westminster and Potomac terranes, Maryland, Virginia, and Washington, D.C. The Pleasant Grove fault separates the Westminster terrane on the west from the Potomac terrane on the east. Geologic map-unit symbols are as follows: CZmg, Mather Gorge Formation; CZmp, chlorite-sericite phyllonite of the Mather Gorge Formation; CZmm, migmatitic Mather Gorge Formation; CZi, Ijamsville Phyllite; CZmb, Marburg Formation; CZsc, Sams Creek Formation; CZsu, undifferentiated metasiltstone, phyllite, quartzite, and metagraywacke; Cs, Sykesville Formation; Cl, Laurel Formation; O, Ordovician plutons; um, ultramafics; JTR , Late Triassic and Early Jurassic rocks; KT, Cretaceous and Tertiary Coastal Plain deposits. Faults are as indicated and are dashed where inferred. Modified from Davis and others (2002).

U.S. Department of the Interior, U.S. Geological Survey
URL: https:// pubs.usgs.gov /circ/2004/1264/html/trip5/fig2.html
For more information, contact Michael Kunk
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