Floian
Key events in the Ordovician
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Key events of the Ordovician Period.
ICS approved stages.
Axis scale: millions of years ago.
ICS approved stages.
Axis scale: millions of years ago.
The Floian is the second stage of the Ordovician. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian stage of the Middle Ordovician. The Floian extended from 477.7 ± 1.4 to 470.0 ± 1.4 million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.