Ordovician Period
From 488.3 +/- 1.7 To 443.7 +/- 1.5 Ma
Start Defined By: Conodont, lowest occurrence of Iapetognathus fluctivagus;
just above base of Cordylodus lindstromi conodont Zone. Just below lowest
occurrence of planktonic graptolites.
End Defined By: Graptolites, lowest occurrences of Parakidograptus
acuminatus and Akidograptus ascensus.
Start Based On: Gradstein, Ogg, Smith, _A Geologic Time Scale 2004_
End Based On: Gradstein, Ogg, Smith, _A Geologic Time Scale 2004_
-- Overlaps With --
North American Stage: Ibexian (491 - 471.8)
-- A Substage of --
Eon: Phanerozoic (542 - -5.5012e-005)
Era: Paleozoic (542 - 251)
-- Preceeded By --
Period: Cambrian (542 - 488.3)
Epoch: Late Cambrian (501 - 488.3)
Australian Stage: Payntonian (491 - 488.3)
Regional Stage: Dolgellian (492.5 - 488.3)
Russian-Kazakhian Stage: Batyrbayan (491.5 - 488.3)
-- Followed By --
Period: Silurian (443.7 - 416)
Epoch: Early Silurian (443.7 - 422.9)
Sub-Epoch: Llandovery (443.7 - 428.2)
ICS Stage: Rhuddanian (443.7 - 439)
Australian Stage: Keiloran (443.7 - 433)
Chinese Stage: Longmaxian (443.7 - 438)
North American Stage: Medinan (443.7 - 438)
Regional Stage: Alexandrian (443.7 - 436)
-- Contains the Following Epochs --
Epoch: Early Ordovician (488.3 - 471.8)
Epoch: Middle Ordovician (471.8 - 460.9)
Epoch: Late Ordovician (460.9 - 443.7)
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