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National Geologic Map Database
Map showing publication footprint
  • Usage in publication:
    • Carreras Siltstone*
  • Modifications:
    • Named
  • Dominant lithology:
    • Siltstone
  • 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:

Rocks named the Unibon Shale by Semmes (1919) in the extreme east-central part of the Ciales quadrangle, and eastward into the Corozal quadrangle, are here redefined as the Carreras Siltstone and the name Unibon is abandoned. Consists of fine-grained, thin- to medium-bedded light-colored bands or laminae of mixed reworked ash and epiclastic particles. Is in fault contact with the informal basalt tuff member of the Pozas Formation in the Ciales quadrangle and grades downward into thick arkosic conglomerate in the Corozal quadrangle. Unconformably underlies the San Sebastian Formation. Thickness ranges from several hundred to more than 1,000 m. Age is either Late Cretaceous (Maastrichtian) or early Tertiary (Paleocene or younger) based on meager fossil evidence.

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


Map showing publication footprint
  • Usage in publication:
    • Carreras Siltstone*
  • 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 Carreras Siltstone occurs in central Puerto Rico and consists of tuffaceous siltstone, minor volcanic sandstone, tuff, limestone, limestone breccia, and calcareous sandstone. Grades downward into arkosic conglomerate. Maximum estimated thickness is 600 meters. The Carreras is of early Paleocene(?) age.

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


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

Asterisk (*) indicates usage by the U.S. Geological Survey. Other usages by state geological surveys.

"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 ([ ]).