- Usage in publication:
-
- Pratt Point member*
- Modifications:
-
- Named
- Dominant lithology:
-
- Obsidian
- Rhyodacite
- AAPG geologic province:
-
- Aleutian Islands province
- Alaska Southwestern region
Summary:
Named as member of Little Sitkin dacite (new). Type locality designated on north side of Pratt Point along coast of Little Sitkin Island, Rat Islands group, Aleutian Islands, AK. Forms long narrow body of obsidian, 200 to 700 ft wide and about 2 mi long extending from rim of Little Sitkin crater to coast north of Pratt Point. Unit's obsidian (chemically a rhyodacite) ranges from light-gray to white in color with plagioclase, pyroxene and hornblende phenocrysts, and locally, small pink devitrification spherulites. Ranges from slightly to very vesicular. Apparently has been extruded contemporaneously from same vent of Little Sitkin dacite. Geologic map of Little Sitkin Island shows age is Quaternary.
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 ([ ]).