Arrow Creek Bed of Mowry Formation of Colorado Group (MT)
Arrow Creek Bed of Bootlegger Member of Blackleaf Formation of Colorado Group (MT)
Arrow Creek Member of Colorado Shale (MT*)
early Late Cretaceous (Cenomanian)*
Type section: on north side of Arrow Creek, in sec. 23, T. 18 N., R. 10 E., 4.5 mi northeast of Geyser, [approx. Lat. 47 deg. 18 min. 40 sec. N., Long. 110 deg. 24 min. 30 sec. W., Geyser 7.5-min quadrangle], Judith Basin Co., MT (Reeside and Cobban, 1960).
Central Montana uplift*
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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).