Ahearn Member of Chadron Formation of White River Group (SD)
Oligocene, early
Type locality: at standard section for the Chadron formation in Big Badlands on south fork of Indian Creek, from sec. 34, T. 3 S., R. 12 E., to sec. 10, T. 4 S., R. 12 E., Pennington Co., southwestern SD. Named from ranch formerly at mouth of south fork of Indian Creek (Clark, 1954).
Williston basin
Chadron arch
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
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