U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database
Map showing publication footprint
  • Usage in publication:
    • Rio Abajo Formation*
  • Modifications:
    • Named
  • Dominant lithology:
    • Tuff
    • Breccia
    • Conglomerate
    • Lava
  • AAPG geologic province:
    • Caribbean region
Publication:

M'Gonigle, J.W., 1977, The Rio Abajo, Pitahaya, and Daguao Formations in eastern Puerto Rico, IN Contributions to stratigraphy: U.S. Geological Survey Bulletin, 1435-B, p. B4-B6.


Summary:

Named Rio Abajo Formation for Rio Abajo, Humacao quadrangle, PR. Consists of andesitic volcaniclastic tuff, breccia, conglomerate, and lava flows; medium-gray to brownish-gray, speckled. Unit is greater than 600 meters thick. Base and top of formation is not exposed; it is in fault contact with the Pitahaya Formation and informal Late Cretaceous Mambiche sequence; may unconformably underlie Pitahaya Formation to west of study area. Age is considered Early(?) Cretaceous.

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


Map showing publication footprint
  • Usage in publication:
    • Rio Abajo 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 Rio Abajo Formation occurs in central Puerto Rico and consists of crystal-lithic tuff and interbedded volcaniclastic sandstone and breccia with abundant clasts of embayed quartz and bipyramidal quartz crystals. Tuff facies is locally metamorphosed to phyllite or hornblende schist near contacts with the San Lorenzo batholith. Maximum estimated thickness is 600 meters. The Rio Abajo is of Early Cretaceous age.

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 ([ ]).

Accessibility FOIA Privacy Policies and Notices

USA Gov U.S. Department of the Interior | U.S. Geological Survey
Supported by the National Cooperative Geologic Mapping Program
Page Contact Information: Personnel
Page Last Modified: Thu 04 Apr 2024 03:30:48 PM MDT