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  • Usage in publication:
    • Principio Creek Member*
  • Modifications:
    • Named
  • Dominant lithology:
    • Schist
    • Andesite
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Higgins, M.W., 1977, Six new members of the James Run Formation, Cecil County, northeastern Maryland, IN Sohl, N.F., and Wright, W.B., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1976: U.S. Geological Survey Bulletin, 1435-A, p. A122-A127.


Summary:

Principio Creek Member named in this report as one of eight members of James Run Formation of Glenarm Group. Unit is dark-gray to dark-green, medium-grained biotite-feldspar schist, possibly meta-andesite, with relict plagioclase phenocrysts, epidosite inclusions, and metavolcanic rocks. Thickness 610 m. Underlies unnamed felsite member of James Run Formation; probably partly equivalent to parts of Happy Valley Branch Member and parts of Port Deposit Gneiss. Age is early Paleozoic.

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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