Spergen Formation  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Paleozoic
 ...Carboniferous
 ....Mississippian
 .....Upper Mississippian
 ......Meramecian
 .......Spergen Formation
RTIowa
 Kentucky
 Missouri
 Illinois
 Indiana
SNS Indiana, Illinois, E Iowa, W Kentucky and E Missouri. Added to Thesaurus in 1985.