- Usage in publication:
-
- Gemuk group*
- Modifications:
-
- Named
- Biostratigraphic dating
- Dominant lithology:
-
- Siltstone
- Chert
- Volcanics
- AAPG geologic province:
-
- Alaska Southwestern region
Summary:
Named after Gemuk River. Type locality designated as favorable exposures north of lower middle course of Gemuk River, southwest of Kuskokwim River, southwestern AK. Extends northward about 15 mi from northwest side of Gemuk River Valley into drainage basins of Atsaksovluk and Chikululnuk Creeks, and northeastward about 15 mi into headwater area of main fork of Holokuk River. Comprises chiefly dense dark massive siltstone with interbeds of chert, volcanic rocks, limestone, graywacke and breccia. Volcanic rock consists chiefly of andesitic lava. Is estimated to be 15,000 to 25,000 ft thick. Base is not exposed. Conformably underlies Kuskokwim group (new). Fossils of Late Triassic and Early Cretaceous age were collected from group. Correlation and stratigraphic relations suggest age range of Carboniferous(?), Permian(?), Triassic, and Early Cretaceous.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Gemuk Group*
- Modifications:
-
- Age modified
- Biostratigraphic dating
- AAPG geologic province:
-
- Alaska Southwestern region
Summary:
(advance copy). Age is Triassic and Early Cretaceous based on stratigraphic relations and fossils (pelecypods and others).
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 ([ ]).