Archean Eon

Part of the Terrestrial Geologic Timescale

Hadean Eon - Archean Eon - Proterozoic Eon

The Archean Eon begins with at the time at which Earth's oldest known rocks - the Acasta Gneiss - were formed, and ended at the time from which the first glacial deposits are known. The Late Heavy Bombardment that had terrorized the planet since the late Hadean ended during this eon. Early life either re-evolved or survived the Bombardment, and the oldest known fossils - stromatolites - are known from this eon.

The Archean was previously subdivided into four eras, none of which were subdivided further into periods and were defined entirely chronometrically before the proposal published in the GTS2012. A scheme with this system may be found in the Alternate section of this site.

The Archean is subdivided into three eras: the Paleoarchean, the Mesoarchean, and the Neoarchean.

Archean Timescale:

Archean Eon - 4030-2420 MYA

-Paleoarchean Era - 4030-3490 MYA

--Acastan Period - 4030-3810 MYA

--Isuan Period - 3810-3490 MYA

-Mesoarchean Era - 3490-2780 MYA

--Vaalbaran Period - 3490-3020 MYA

--Pongolan Period - 3020-2780 MYA

-Neoarchean Era - 2780-2420 MYA

--Methanian Period - 2780-2630 MYA

--Siderian Period - 2630-2420 MYA