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EARTH SCIENCE

Platte Canyon High School
Bailey, Colorado

Time Scale

GEOLOGIC TIME SCALE

Ordovician

after Harland et al., 1982

  =========================================================
Period Epoch Age Ma age Comments
      438  
Ordovician Ashgill Hirnantian    
Rawtheyan    
Cautleyan    
Psugillian 448  
Caradoc Onnian    
Actonian    
Marshbrookian    
Longvillian    
Doudleyan    
Harnagian    
Costonian 458  
Llandeilo Late    
Middle    
Early 468  
Llanvirn Late    
Early 478  
Arenig   488  
Tremadoc   505