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National Geologic Map Database

Geologic Unit: Boulder River

Usage:

Boulder River Sandstone Member of Frontier Formation (MT*)


Geologic age:

early Late Cretaceous (Cenomanian)*


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

[Named from] exposures along west side of Boulder River valley, in SE/4 sec. 11, T. 3 S., R. 12 E., McLeod Basin quadrangle, [Sweet Grass Co.], southwestern MT. Member forms almost continuous ridge from Boulder River westward to Yellowstone River south of Livingston (Richards, 1957).
Reference section (of Frontier Formation): on north side of Canyon Mountain, [just southwest of Livingston], in secs. 26 and 27, T. 2 S., R. 9 E., [in vicinity of Lat. 45 deg. 37 min. 37 sec. N., Long. 110 deg. 35 min. 30 sec. W., Livingston 7.5-min quadrangle], Park Co., southwestern MT (Roberts, 1972).


AAPG geologic province:

Central Montana uplift*
Montana folded belt*


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 ([ ]).