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Geologic Unit: Swarthmore
Map showing publication footprint
  • Usage in publication:
    • Swarthmore granodiorite*
  • Modifications:
    • Named
  • Dominant lithology:
    • Granodiorite
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Postel, A.W., and Jaffe, H.W., 1957, Lead-alpha determinations of the Swarthmore granodiorite and associated rocks: Pennsylvania Academy of Science Proceedings, v. 31, p. 120-123.


Summary:

Name Swarthmore introduced in this report to replace preempted name Springfield granodiorite. Study indicates that lead-alpha ages of zircon of Wissahickon schist are older than those of Swarthmore granodiorite and related rocks and that all of the ages are younger than Precambrian. Age of Swarthmore given here as late Paleozoic.

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


Map showing publication footprint
  • Usage in publication:
    • Swarthmore Granodiorite*
  • Modifications:
    • Age modified
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Lyttle, P.T., and Epstein, J.B., 1987, Bedrock geologic map of the Newark 2 degrees quadrangle, New York, New Jersey, and Pennsylvania: U.S. Geological Survey Miscellaneous Investigations Series Map, I-1715, 2 sheets, scale 1:250,000 [http://ngmdb.usgs.gov/Prodesc/proddesc_9892.htm]


Summary:

Age of Swarthmore Granodiorite changed to Ordovician.

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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