- Usage in publication:
-
- Rat formation*
- Modifications:
-
- Named
- Dominant lithology:
-
- Andesite
- Breccia
- AAPG geologic province:
-
- Aleutian Islands province
- Alaska Southwestern region
Summary:
Occurs in southeastern part of Rat Island, Aleutian Islands, AK. Contains andesitic rock and conglomerate derived from it. Andesite is porphyritic and has many conspicuous phenocrysts. Rock occurs as thick, columnar-jointed lava flows and massive flow breccia. No fossils were found. Contact with Gunners Cove formation (new) is not exposed. It is inferred that Rat formation is older than Gunners Cove formation and probably is Tertiary or older age.
Source: GNU records (USGS DDS-6; Menlo 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 ([ ]).