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BTChronostratigraphic Units
 .Phanerozoic
 ..Paleozoic
 ...Deadwood Formation
RTLower Ordovician
 Wyoming
 Montana
 Upper Cambrian
 South Dakota
SNUpper Cambrian and Lower Ordovician. In N Black Hills, conformably underlies Aladdin Sandstone. SE Montana, W South Dakota (Black Hills), and E Wyoming. Indexed with ages as applicable.