Antrim Shale  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Paleozoic
 ...upper Paleozoic
 ....Antrim Shale
RTUpper Devonian
 Michigan
 Lower Mississippian
SNUpper Devonian and Lower Mississippian. Indexed with ages as applicable. Added to Thesaurus in 1985.