Neoarchaean

The Neoarchaean Eon is the third and final eon of the Archaean Supereon. It spanned from 2.8 to 2.5 billion years ago. This period is characterized by significant geological and biological developments that laid the groundwork for the Proterozoic Eon.

Geologically, the Neoarchaean saw the further assembly of continents. Large continental landmasses began to form through processes of accretion and stabilization of existing crustal fragments. This era is marked by the formation of major cratons, which are the stable, ancient cores of continents. Volcanic activity remained prevalent, contributing to the thickening of the crust and the formation of new rock formations. Mountain-building events, or orogenies, also occurred, further shaping the nascent continents.

Biologically, the Neoarchaean is a crucial period for the evolution of life. By this time, prokaryotic life, such as bacteria and archaea, was well-established. Evidence suggests that photosynthesis, likely anoxygenic at first and then evolving towards oxygenic photosynthesis by cyanobacteria, was becoming more widespread. While oxygenic photosynthesis did not lead to a significant rise in atmospheric oxygen during the Neoarchaean, it marked a pivotal step in the biochemical evolution of life. The increasing biological activity, particularly photosynthesis, may have begun to influence ocean chemistry, setting the stage for future atmospheric changes. The fossil record from this eon includes stromatolites, layered structures formed by microbial communities, and microfossils providing glimpses into early life forms. The Neoarchaean ended with the Precambrian/Cambrian boundary.