upper Oligocene  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Cenozoic
 ...Paleogene
 ....Oligocene
 .....upper Oligocene
NTChattian
 Chickasawhay Formation
 Egerian
 Suwannee Limestone
RTAnahuac Formation
 Arikaree Group
 Arikareean
 lower Oligocene
 middle Oligocene
 John Day Formation
 Pirabas Formation