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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).