Part of the Zirconian Era
Hephaestean Period - Jacobian Period - Canadian Period
The Jacobian Period is the first period of the Zirconian Era, and the fourth of the Hadean Eon. The Jacobian begins at the time from which the oldest known crustal materials - detrital zircons - are known and ends with the challenged dating of the Nuvvuagittuq greenstone belt. While liquid water may have been present on the surface as early as the Hephaestean Period, it was during the Jacobian that the first oceans and the atmosphere were formed. It has also been theorized that the first life had evolved during the Jacobian, but whether or not the Jacobian biota were the ancestors of modern lifeforms is debatable. Some would contest that the Late Heavy Bombardment that began during the Procrustean Period would have destroyed any life that had existed previously. However, given how quickly life would re-emerge, it is much more likely that it never was wiped out, but simply dwindled in number due to the bombardment. If this is the case, the life of the Jacobian would be the oldest living ancestors of all modern lifeforms.
The Jacobian is not further subdivided into epochs.
Jacobian Timescale:
Jacobian Period - 4404-4280 MYA