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                          Cayugan North American Stage
 
                      From 421.3 +/- 2.6 To 416 +/- 2.8 Ma
 
  Start Defined By:  Imprecise.  May be near base of Saetograptus 
     leintwardinensis graptolite zone.
  End Defined By:  Graptolite, lowest occurrence of Monograptus uniformis.
 
  Start Based On:  Gradstein, Ogg, Smith, _A Geologic Time Scale 2004_
  End Based On:  Gradstein, Ogg, Smith, _A Geologic Time Scale 2004_
 
 -- Overlaps With --
  Sub-Epoch:     Ludlow         (422.9 - 418.7)
  Chinese Stage: Miaogoalingian (422 - 418.7)
 
 -- A Substage of --
  Eon:              Phanerozoic   (542 - -5.5012e-005)
  Era:              Paleozoic     (542 - 251)
  Period:           Silurian      (443.7 - 416)
  Epoch:            Late Silurian (422.9 - 416)
  Australian Stage: Melbournian   (428.2 - 416)
 
 -- Preceeded By --
  ICS Stage:            Gorstian (422.9 - 421.3)
  North American Stage: Niagaran (438 - 421.3)
 
 -- Followed By --
  Period:               Devonian       (416 - 359.2)
  Epoch:                Early Devonian (416 - 397.5)
  ICS Stage:            Lochkovian     (416 - 411.2)
  Chinese Stage:        Lianhuashanian (416 - 413)
  North American Stage: Ulsterian      (416 - 391.8)
 
 -- Contains the Following Sub-Epochs --
  Sub-Epoch: Pridoli (418.7 - 416)
 
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