Usage:
Twilight Gneiss (CO*)
Geologic age:
Paleoproterozoic*
Type section, locality, area and/or origin of name:
Composes Twilight Peak, west of Animas River, Needle Mountains 15-min quadrangle, San Juan Co., southwestern CO (Cross and Howe, 1905).
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 ([ ]).