Neoarchean

Neoarchean is a subdivision of the Archean Eon in the geological timescale, spanning roughly from 2.8 to 2.5 billion years ago. The term reflects distinctive crustal growth and geochemical signatures recognized in rocks of this interval, and it lies between the Mesoarchean and the Paleoproterozoic.

Geology and crustal development during the Neoarchean include the continued expansion and stabilization of continental crust, leading to the formation of large cratons and the development of greenstone belts and granitoid intrusions. This period is interpreted as a time of active crustal differentiation and tectonic processes consistent with evolving plate tectonics, though the exact styles of deformation may have varied regionally.

Biological activity during the Neoarchean was dominated by microbial ecosystems. Fossil evidence such as stromatolites and microfossils indicates ongoing photosynthetic life, including cyanobacteria, in shallow marine and coastal environments. While photosynthesis contributed to localized oxygenic production, atmospheric and oceanic oxygen levels were generally low compared with later eons; the major global rise in oxygen occurred later, in the Paleoproterozoic.

The Neoarchean is important for understanding early crust formation, the stabilization of continental-scale landmasses, and the early evolution of life on Earth. It precedes the onset of major atmospheric oxygenation and offers insights into how early Earth environments supported complex geological and biological development.