- Usage in publication:
-
- Arrow Creek member*
- Modifications:
-
- Original reference
- Dominant lithology:
-
- Bentonite
- Tuff
- AAPG geologic province:
-
- Sweetgrass arch
Summary:
Pg. 8, 14 (fig. 8), 38, 39, 40, 41, 42, 43, 44. Arrow Creek member of Colorado shale. Consists of bentonite, tuff, and porcelanite. Thickness 40 feet in type area. Underlies Mowry member. In Teigen area, the bentonite is 2.5 feet thick and is about 50 feet below Mowry member. Thickens northwestward, and top of member gradually approaches base of Mowry. Age is Early Cretaceous.
Type section: on north side of Arrow Creek, in sec. 23, T. 18 N., R. 10 E., 4.5 mi northeast of Geyser, Judith Basin Co., MT. Forms conspicuous white outcrop for 35 mi between Belt Butte and Stanford.
Source: US geologic names lexicon (USGS Bull. 1200, p. 142).
- Usage in publication:
-
- Arrow Creek Member*
- Modifications:
-
- Biostratigraphic dating
- Geochronologic dating
- AAPG geologic province:
-
- Sweetgrass arch
Summary:
Arrow Creek Member of Colorado Shale. Sample collected from a 10-m-thick bentonite bed, bracketed by the NEOGASTROPLITES CORNUTUS ammonite zone, in "Lower horizon," Arrow Creek Member of Colorado Shale, in SE/4 NW/4 sec. 17, T. 18 N., R. 10 E., Judith Basin Co., MT (Sweetgrass arch). K-Ar age on biotite-sanidine pair 95.3 +/-1.0 Ma (weighted mean). Age is Early Cretaceous (Albian).
Source: Modified from GNU records (USGS DDS-6; Denver GNULEX).
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 ([ ]).