IODP SEDIS - Thesaurus -

Hirnantian
BT	Chronostratigraphic Units
	.Phanerozoic
	..Paleozoic
	...Ordovician
	....Upper Ordovician
	.....Hirnantian
BT	Chronostratigraphic Units
	.Phanerozoic
	..Paleozoic
	...Ordovician
	....Upper Ordovician
	.....Ashgillian
	......Hirnantian
RT	Bala
SN	Europe. Upper stage of Ashgillian. Below Llandoverian. Added to Thesaurus in 1993.