Katian

EtymologyName formalityFormalUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitAgeStratigraphic unitStageTime span formalityFormalLower boundary definitionFAD of the graptoliteLower boundary GSSPBlack Knob Ridge section, Oklahoma, United States
34°25′50″N96°04′29″W / 34.4305°N 96.0746°W / 34.4305; -96.0746Lower GSSP ratified2006Upper boundary definitionFAD of the graptoliteUpper boundary GSSPWangjiawan section, Wangjiawan, Yichang, China
30°59′03″N111°25′11″E / 30.9841°N 111.4197°E / 30.9841; 111.4197Upper GSSP ratified2006

The Katian is the second stage of the Upper Ordovician. It is preceded by the Sandbian and succeeded by the Hirnantian Stage. The Katian began 452.8 million years ago and lasted for about 7.6 million years until the beginning of the Hirnantian 445.2 million years ago. During the Katian the climate cooled which started the Late Ordovician glaciation.