Usage:
Thumb Member of Horse Spring Formation (AZ*,NV*)
Geologic age:
Tertiary*
Miocene, middle*
Type section, locality, area and/or origin of name:
Type section: Thumb Valley north of Lake Mead, Clark Co., NV (Longwell, 1963).
Principal reference section: Lat. 36 deg. 37 min. 30 sec. N., Long. 114 deg. 56 min. 45 sec. W. (Bohannon, 1984).
AAPG geologic province:
Great Basin 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 ([ ]).