The Neoarchean (pronounced /ˌniː.oʊ.ɑrˈkiː.ən/, also spelled Neoarchaean) is a geologic era within the Archaean. It spans the period of time from 2,800 to 2,500 million years ago—the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. Oxygenic photosynthesis first evolved in this era and was accountable for the oxygen catastrophe which was to happen later in the paleoproterozoic from a poisonous buildup of oxygen in the atmosphere, produced by these oxygen producing photoautotrophs, which evolved earlier in the Neoarchean.
