Early Ordovician

thumb|Rock from the Skiddaw Group, of Ordovician (Tremadocian) age, at Scawgill Bridge quarry in [[Cumbria, England, UK]]

The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician series. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.

first epoch of the Ordovician Period

thumb|right|Arenig Fawr, the mountain which lends its name to the geological series In geology, the Arenig (or Arenigian) is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval.