Usage:
No current usage.
(†River Portal Mica Schist (CO) is same as Black Canyon Schist. See Black Canyon.)
Geologic age:
Paleoproterozoic
Type section, locality, area and/or origin of name:
Not designated. Named from exposures in vicinity river portal of Gunnison tunnel, on north side of Gunnison River, in T. 49 N., R. 7 W., Montrose Co., CO (Hunter, 1925).
AAPG geologic province:
Southern Rocky Mountain region
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 ([ ]).