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National Geologic Map Database

Geologic Unit: Twilight

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 ([ ]).