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National Geologic Map Database

Geologic Unit: San Juan

Usage:

San Juan Tuff (CO*)
San Juan Formation (CO*)
San Juan Breccia (CO*)


Subunits:

(alphabetical): Canyon Creek Member (CO*), Sneffels Member (CO*).


Geologic age:

early Tertiary (Oligocene)*


Type section, locality, area and/or origin of name:

Notable exposures in Telluride district, [San Miguel, San Juan, and Ouray Cos., Telluride quadrangle], southwestern CO (Cross, 1896).
[Widely distributed in northwestern part of San Juan Mountains, in Telluride, Silverton, and Montrose quadrangles. Extends to north of Montrose and Uncompahgre quadrangles into West Elk Mountains (Gunnison National Forest).]


AAPG geologic province:

Paradox basin*
San Juan Mountains province*


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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).