Shell Rock Formation of Cedar Valley Group (IA)
Shell Rock Formation (IA)
Shell Rock Limestone (IA)
(alphabetical) all in IA: Mason City Dolomite Member, Nora Member, Rock Grove Member.
early Late Devonian (Frasnian)
Typical development along Shell Rock River between Rockford and Nora Springs and on northward, also about Mason City and to the north and northwest. Named from Shell Rock River (Thomas, 1924).
Reference section (subsurface): FM-4 core, in sec. 31, T. 96 N., R. 18 W., Floyd Co., IA (Witzke and others, 1988).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
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