- Usage in publication:
-
- Circle volcanics*
- Modifications:
-
- Named
- Dominant lithology:
-
- Greenstone
- Chert
- Argillite
- Tuff
- Breccia
- AAPG geologic province:
-
- Alaska East-Central region
Summary:
Named for outcrop of about 15 mi along east bank of Yukon upstream from Circle, east-central AK. Also crops out at Fort Hamlin, at lower end of Yukon Flats, and continuing downstream below Rampart. Composed essentially of basaltic lavas of greenstone habit, including some interbedded sedimentary rocks, mainly chert and argillite, some tuffs and flow breccias. Cut by diabasic and gabbroic intrusive rocks. Is considered to represent the base of Carboniferous System in Eagle-Circle district. Assigned Early Mississippian age on basis of stratigraphic position and correlation with upper part of Rampart group.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Circle Volcanics*
- Modifications:
-
- Age modified
- Biostratigraphic dating
- AAPG geologic province:
-
- Alaska East-Central region
Summary:
Most of samples mapped as Circle Volcanics in northern part of eastern Crazy and Little Crazy Mountains, include chert of two distinct ages --Late Mississippian or Early Pennsylvanian age, and Middle and Late Triassic. Thus age of Circle Volcanics is here considered to be late Paleozoic and Triassic.
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 ([ ]).