- Usage in publication:
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- Monument Hill bentonitic member*
- Modifications:
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- Named
- Dominant lithology:
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- Shale
- Bentonite
- AAPG geologic province:
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- Powder River basin
- Williston basin
Summary:
Named as a member of the Pierre shale for exposures at Monument Hill, sec 32, T56N, R68W, Crook Co, WY in the Powder River basin. Consists of impure bentonite and siltstone. Some calcareous and barite concretions. Marine fossils. Commonly forms a scarp. Thickness about 150 ft. Type section not given. Overlain and underlain by unnamed shale members. Exposed along the west side of the Black Hills in northeastern WY and southeastern MT in the Powder River and Williston basins. Late Cretaceous in age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Monument Hill bentonitic member*
- Modifications:
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- Overview
- Age modified
- AAPG geologic province:
-
- Powder River basin
- Williston basin
Summary:
Member of Pierre shale on western rim of Black Hills, WY in Powder River basin. Conformably overlain and underlain by unnamed parts of Pierre shale. Correlated with Verendrye shale member and lower part of overlying Virgin Creek shale member in west-central SD and the lower part of Bearpaw shale in central MT. Late Cretaceous in age. Age refined to Campanian.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Monument Hill bentonitic member*
- Modifications:
-
- Biostratigraphic dating
- Overview
- AAPG geologic province:
-
- Powder River basin
- Williston basin
Summary:
A member of Pierre shale. Lists index fossils and discusses their stratigraphic and geographic distribution in Powder River basin and southernmost part of Williston basin. Shows faunal zonation. Late Cretaceous (Campanian) in age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Monument Hill bentonitic member
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Powder River basin
Summary:
A member reassigned to Bearpaw formation in the northeast part of Powder River basin, WY and MT. Underlain conformably by a black to gray shale member; overlain conformably by a dark shale member. Late Cretaceous in age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Monument Hill bentonitic member*
- Modifications:
-
- Overview
- AAPG geologic province:
-
- Williston basin
- Powder River basin
Summary:
Member of Pierre shale. Present in Carter Co, MT and the northern part of Crook Co, WY in Williston and Powder River basins. Lists fossils and describes measured section in the SE1/4 sec 12, T9S, R55E, Carter Co, MT where member is 219 ft thick, and about 202 ft below base of Fox Hills sandstone. Overlain and underlain by unnamed shale member. Not present in southern Crook Co and Weston Co, WY in Powder River basin. Late Cretaceous in age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Monument Hill bentonitic member*
- Modifications:
-
- Overview
- AAPG geologic province:
-
- Powder River basin
Summary:
Member of Pierre shale. Map shows distribution of outcrop in northern Crook Co, WY and part of Carter Co, MT in the Powder River and Williston basins. Lists fossils and describes lithologic variations. Late Cretaceous (Campanian) in age.
Source: 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 ([ ]).