Usage:
Twentymile Sandstone of Mesaverde Group (CO)
Twentymile Sandstone Member of Williams Fork Formation of Mesaverde Group (CO*)
Geologic age:
Late Cretaceous*
Type section, locality, area and/or origin of name:
Not designated. Named from development in and around Twentymile Park, Routt Co., CO (Fenneman and Gale, 1906).
AAPG geologic province:
Green River basin*
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 ([ ]).