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Geologic Unit: Challis

Challis Volcanics (ID*,MT?)
/Challis Volcanic Group (ID*)
[A group [or supergroup] name combines a geographic name with the term "group," [or “supergroup,”] and no lithic designation is included (ACSN, 1961, 1970; NACSN, 1983).]
[Discrepancy concerning areal extent. See remarks under "Publication History".]

Geologic Province:
Idaho Mountains province*
Snake River basin*
Areal Extent:

Type Locality:
Not designated. Named from Challis National Forest and town of Challis, Custer Co., ID (Ross, 1930).
Named from town of Challis, Custer Co., ID (Ross, 1934).

Unit Name History:
First used (Ross, 1930).
Named (Ross, 1934).
Revised (Ross, 1937; Anderson, 1957).
Revised, raised to group rank (Anderson, 1961).
Age modified; Isotopic dating (Cater and others, 1973).
Isotopic dating (Staatz, 1979).
Revised (Hobbs, 1980; Foster, 1982).
Overview (Leonard and Marvin, 1982).
Isotopic dating (Marvin and Mehnert, 1988).
Mapped 1:250k; Overview; Revised, raised to group rank (Fisher and others, 1992).
Mapped 1:250k (Ruppel and others, 1993).
Mapped 1:24k; Overview, incl. sedimentary formations (Skipp and others, 1994).
[Discrepancy in GNU records (USGS DDS-6) concerning the areal extent of this unit. The GNU comprehensive file GEONAMES indicates this unit extends into MT as the Challis Volcanics (explanation and reference not given). Denver GNULEX does not. Uncertain if used by the Montana Geol. Survey. --unresolved.]

Note: If you need more information, please contact Nancy Stamm (
Asterisks (*) indicate usage by the U.S. Geological Survey. Other usages by state geological surveys.

"No current usage" implies that a name has been abandoned or that it has fallen into disuse. Former usage and, if known, replacement name given in parentheses ().

Slashes (/) indicate unit name usage violates the 1983 North American Stratigraphic Code. This violation may be explained within brackets ([ ]).

U.S. Department of the Interior, U.S. Geological Survey, Reston, VA, USA
Database project personnel
Last modified: 15-Jan-2013