Arenig

[1] In the geologic timescale, the Arenig or Arenigian refers to an age of the Early Ordovician epoch, between 477.7 and 470 million years ago, contemporary with the Floian of the ICS,[2] based on a section in Sweden (Diabasbrottet quarry) and with the same boundaries.

The Arenig and equivalent Floian are represented in North America by the upper three stages of the Canadian which is followed by the Middle Ordovician Whiterockian which is the lower part of the now shortened Chazyan.

The Arenig rocks were deposited during a sudden worldwide rise in sea level resulting in widespread marine transgression.

[3] The following is a list of Actinocerid genera whose fossils are geochronologically found first in upper Arenig strata.

The following is a list of Endocerid genera whose fossils are geochronologically found first in upper Arenig strata.