Geochemistry and shock petrography of the Crow Creek Member, South Dakota, USA: Ejecta from the 74-Ma Manson impact structure
نویسندگان
چکیده
The Crow Creek Member is one of several marl units recognized within the Upper Cretaceous Pierre Shale Formation of eastern South Dakota and northeastern Nebraska, but it is the only unit that contains shock-metamorphosed minerals. The shocked minerals represent impact ejecta from the 74-Ma Manson impact structure (MIS). This study was aimed at determining the bulk chemical compositions and analysis of planar deformation features (PDFs) of shocked quartz; for the basal and marly units of the Crow Creek Member. We studied samples from the Gregory 84-21 core, Iroquois core and Wakonda lime quarry.
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