Usage:
Isom Formation (NV*,UT*)
Isom Formation of Needles Group (UT*)
Subunits:
(alphabetical): Baldhills Tuff Member (NV*,UT*), Blue Meadows Tuff Member (UT*), Hole-In-The-Wall Tuff Member (NV*,UT*).
Geologic age:
early Tertiary (Oligocene)*
Type section, locality, area and/or origin of name:
Type locality: south slope of east-west ridge north of Isom Creek, in northwest part Iron Springs district, in sec. 5, T. 35 S., R. 12 W., Three Peaks quadrangle, Iron Co., UT (Mackin, 1960).
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 ([ ]).