Usage:
Bilk Creek Sandstone Member of Wanakah Formation of San Rafael Group (CO*)
Geologic age:
late Middle Jurassic (Callovian)*
Type section, locality, area and/or origin of name:
Named from exposures along highway opposite mouth of Bilk Creek, about 6 mi west of Telluride, San Miguel Valley, [approx. Lat. 37 deg. 56 min. 54 sec. N., Long. 107 deg. 55 min. 16 sec. W., in sec. 36 (unsurveyed), T. 43 N., R. 10 W., Gray Head 7.5-min quadrangle, San Miguel Co., Uncompahgre National Forest], southwestern CO (Goldman and Spencer, 1941).
Reference section: east-facing cliffs bordering Gunnison River, western Black Canyon, Montrose Co., southwestern CO (O'Sullivan, 1992).
AAPG geologic province:
Paradox basin*
Piceance basin*
San Juan 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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).