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National Geologic Map Database

Geologic Unit: Pentagon

Usage:

Pentagon Shale (MT*)


Geologic age:

Middle Cambrian*


Type section, locality, area and/or origin of name:

Type locality: on Continental Divide, in NE/4 sec. 24, T. 25 N., R. 12 W., [Pentagon Mountain 7.5-min quadrangle (1994 ed.), Flathead and Lewis and Clark Co. bdry.], northwestern MT. Named from Pentagon Mountain, which lies approx. 2 mi northwest of type locality, [in NW/4 NW/4 NW/4 sec. 14, T. 25 N., R. 12 W., Pentagon Mountain 7.5-min quadrangle (1994 ed.), Flathead Co., northwestern MT] (Deiss, 1933).


AAPG geologic province:

Montana folded belt*
Sweetgrass arch*


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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).