PBDB Interval Range

450.4 - 443.8 Ma

International Chronostratigraphic Timescale			Ordovician of North America					Ordovician of Britain
Ordovician	Late Ordovician	Hirnantian	Cincinnatian	Gamachian				Ashgill	Hirnantian			443.8
		Katian		Gamachian					Rawtheyan			445.2
				Richmondian					Rawtheyan			446 *
									Cautleyan			448.9 *
									Pusgillian			449.3 *
								Caradoc	Streffordian	Onnian †		449.6 *
				Maysvillian	Rocklandian †/Shermanian/Ashbyan/Kirkfieldian/Blackriveran/Wildernessian/Trentonian/Franklinian							449.8 *
				Edenian								450.4 *
			Mohawkian	Chatfieldian								451.1 *
									Cheneyan			451.5 *
									Burrellian			452.7 *
		Sandbian										453
										Actonian †		453.2 *
				Turinian						Actonian †		453.7 *
										Marshbrookian †	Woolstonian †	454.2 *
										Longvillian †		455.2 *
									Aurelucian			456.8 *
			Whiterockian		Canadian †	Chazyan †/Marmor						457 *
										Soudleyan †/Harnagian/Costonian		457.4 *
	Middle Ordovician	Darriwilian						Llanvirn	Llandeilian/Llandeilo/Late Llandeilo/Middle Llandeilo/Early Llandeilo/Late Llanvirn			458.4
		Darriwilian							Abereiddian/Early Llanvirn			461.3 *
		Dapingian							Abereiddian/Early Llanvirn			467.3
								Arenig	Fennian			468.4 *
				Rangerian								469.1 *
	Early Ordovician	Floian	Ibexian	Blackhillsian		Jeffersonian †	Cassinian †					470
				Blackhillsian					Whitlandian			471.1 *
				Tulean					Whitlandian			473.9 *
									Moridunian			474.3 *
		Tremadocian						Tremadoc	Migneintian			477.7
				Stairsian					Migneintian			480.3 *
				Stairsian					Cressagian			480.8 *
				Skullrockian/Demingian					Cressagian			482 *
				Skullrockian/Demingian								485 *
												485.4
												487.5