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  • Usage in publication:
    • Purcell Branch Formation*
  • Modifications:
    • Named
  • Dominant lithology:
    • Diamict
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Pavlides, Louis, 1989, Early Paleozoic composite melange terrane, central Appalachian Piedmont, Virginia and Maryland; its origin and tectonic history, IN Horton, J.W., Jr., and Rast, Nicholas, eds., Melanges and olistostromes of the U.S. Appalachians: Geological Society of America Special Paper, 228, p. 135-193.


Summary:

A block-in-metadiamictite melange in north-central VA is here named the Purcell Branch Formation, for Purcell Branch, Prince William Co. It consists of dark-gray metadiamictite matrix enclosing exotic blocks, several m to several hundred m in length. Rocks of the Purcell Branch are regionally metamorphosed to greenschist facies. The melange formed in a Cambrian-Ordovician back-arc basin or marginal basin that lay on the continentward side of an island arc system (Central Virginia Volcanic-Plutonic Belt) that had formed in Cambrian time. Diamictite was thrust on and across basement rocks during the Taconic Orogeny.

Source: GNU records (USGS DDS-6; Reston GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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