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National Geologic Map Database
Geologic Unit: Perchas
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Map showing publication footprint
  • Usage in publication:
    • Perchas Lava Member*
  • Modifications:
    • Named
  • Dominant lithology:
    • Lava
    • Tuff
    • Sandstone
  • AAPG geologic province:
    • Caribbean region
Publication:

Berryhill, H.L., Jr., 1965, Geology of the Ciales quadrangle, Puerto Rico: U.S. Geological Survey Bulletin, 1184, 116 p.


Summary:

The Perchas Lava Member of the Rio Orocovis Formation, here adopted by the USGS, consists of massive amygdaloidal pillow lavas and thin lenticular layers of tuff, sandstone, and breccia. Gradationally overlies the Magueyes Member of the Rio Orocovis; unconformably underlies the Avispa Member in the south-central Ciales quadrangle. Thickness is 1,500 m. Age is Turonian(?) to late Santonian(?) or early Campanian.

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


Map showing publication footprint
  • Usage in publication:
    • Perchas Formation*
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Caribbean region
Publication:

Nelson, A.E., 1966, Cretaceous and Tertiary rocks in the Corozal quadrangle, northern Puerto Rico, IN Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin, 1244-C, p. C9-C10.


Summary:

Rio Orocovis Formation redefined Rio Orocovis Group and Perchas Lava Member redefined Perchas Formation. Overlies the Magueyes Formation; conformably underlies the Avispa Formation.

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


Map showing publication footprint
  • Usage in publication:
    • Perchas Formation*
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Caribbean region
Publication:

Krushensky, R.K., 2001, Geologic map of Puerto Rico with correlation chart and map unit descriptions, IN Bawiec, W.J., and others, Geology, geochemistry, geophysics, mineral ccurrences, and mineral resource assessment for the Commonwealth of Puerto Rico: U.S. Geological Survey Open-File Report, OF-98-38, scale 1:100,000


Summary:

The Perchas Formation occurs in central Puerto Rico and consists of pillowed basaltic lava interbedded with basaltic tuff, volcanic sandstone, and minor hyaloclastite breccia. Unit is lithologically similar to the Magueyes Formation. Maximum estimated thickness is 1500 meters. The Perchas is of Cretaceous age.

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


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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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).