Usage:
Pony Express Limestone 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 occurrence in Pony Express Mine, Ouray district, southwestern CO (see Burbank, 1930).
Reference section: east-facing cliffs bordering the 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 ([ ]).