- Usage in publication:
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- Ardmore bentonite bed
- Modifications:
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- Original reference
- Dominant lithology:
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- Bentonite
- AAPG geologic province:
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- Williston basin
- Chadron arch
Summary:
Pg. 3, 23-34. Ardmore bentonite bed of Pierre formation. Bentonite bed about 4 feet thick. Occurs near base of Pierre formation. Commercially important. Age is Late Cretaceous.
Named from exposures near Ardmore, [in northwest part of T. 12 S., R. 4 E.], Fall River Co., southwestern SD.
Source: US geologic names lexicon (USGS Bull. 1200, p. 129).
- Usage in publication:
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- Ardmore bentonite bed*
- Modifications:
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- Age modified
- AAPG geologic province:
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- Chadron arch
Summary:
A bed in the Sharon Springs member of Pierre shale on the south rim of the Black Hills, SD on Chadron arch. Late Cretaceous in age. Age refined to Campanian.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore bentonite bed*
- Modifications:
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- Overview
- AAPG geologic province:
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- Chadron arch
- Williston basin
Summary:
A bed near base of Sharon Springs member of Pierre shale. Shows correlation and stratigraphic relations in 15 stratigraphic sections in Fall River, Custer, Pennington, and Meade Cos, SD on Chadron arch and in Williston basin.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Bed*
- Modifications:
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- Areal extent
- AAPG geologic province:
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- Chadron arch
- Denver basin
- Williston basin
- Powder River basin
- Bighorn basin
Summary:
Is the basal bed of Sharon Springs Member of Pierre Shale where member has been recognized in SD, WY, and MT; in the area near Chadron in northwestern NE; and along the Front Range in northern CO. Includes as a part of Ardmore the underlying thin shale parting and the 8-in-thick bentonite in Fall River Co with its equivalents elsewhere. Marks contact between the hard, fissile shale of Sharon Springs Member and the dark platy shale of Gammon Ferruginous Member. Is of Late Cretaceous age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Bed*
- Modifications:
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- Areal extent
- AAPG geologic province:
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- Bighorn basin
- Powder River basin
Summary:
Widely recognized bed assigned to: Claggett (near base) Shale in central-south MT; Mesaverde Formation in southern Bighorn basin; Cody Shale in northern Bighorn and Powder River basins.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Bed*
- Modifications:
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- Revised
- Areal extent
- AAPG geologic province:
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- Montana folded belt
Summary:
Ardmore Bentonite Bed assigned to Upper Cretaceous Cokedale Formation in Livingston and Crazy Mountains basin of MT, in Montana folded belt province, and to Upper Cretaceous Two Medicine Formation west of Sweetgrass arch in northwest MT. Data based on well logs.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Bed*
- Modifications:
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- Revised
- AAPG geologic province:
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- Williston basin
Summary:
Ardmore Bentonite Bed assigned to Pembina Member of Pierre Shale in ND, Williston basin.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Bed*
- Modifications:
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- Areal extent
- AAPG geologic province:
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- Denver basin
Summary:
Ardmore Bentonite Bed geographically extended into Denver basin of northeast CO.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Beds*
- Modifications:
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- Revised
- Areal extent
- AAPG geologic province:
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- Williston basin
- Powder River basin
Summary:
Stratigraphic rank modified from Ardmore Bentonite Bed to Ardmore Bentonite Beds of Sharon Springs Member of Pierre Shale. Modification made because Ardmore generally includes more than one bed. Extended into Black Hills of WY and SD, Powder River and Williston basins, where Ardmore replaces Pedro Bentonite Bed [of Mitten Member of Pierre Shale]. Term Pedro is abandoned. Ardmore can be recognized far beyond areal limits of Sharon Springs in marine rocks throughout northern Great Plains where it is assigned to other formations (such as Claggett Shale in MT). Bentonites occur near base of Sharon Springs and serve as useful time marker at base of fossil zone 2 of Gill and Cobban (1965, USGS Prof. Paper 392-A). Late Cretaceous age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Ardmore Bentonite Bed*
- Modifications:
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- Revised
- AAPG geologic province:
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- Powder River basin
Summary:
Newly assigned as a bed in the basal part of the unnamed upper part of the Steele Shale in the subsurface on the west side of the Powder River basin, WY in Converse, Johnson, western Campbell, and Sheridan Cos, WY and Big Horn Co, MT. Is newly assigned as a bed at or near base of the Mitten Member of Pierre Shale in subsurface on the east side of the Powder River basin in western Niobrara, northeast Converse, eastern Campbell, and Weston Cos, WY and Powder River Co, MT. Overlies Gammon Ferruginous Member of Pierre where Ardmore forms basal part of Mitten. Late Cretaceous age. [Shown on 22 cross sections in OC series.]
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 ([ ]).