Arenig - Geochronology

Geochronology

In the geologic timescale, the "Arenig" or Arenigian refers to an age of the Lower Ordovician epoch, between 478.6 ± 1.7 and 471.8 ± 1.6 million years ago, contemporary with the more recently proposed Floian by the ICS, based on a section in Sweden (Diabasbrottet quarry) and with the same boundaries. The Arenigian and Floian are the upper part of the Lower Ordovician and follow the Tremadocian (Gasconadian in North America) which is the lower part. Either is followed by the Middle Ordovician ICS Dapingian or by the Llanvirnian of older chronologies. The Arenigian 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.