The Mesoproterozoic eon, often regarded as mundane and static, lays the foundation for dramatic transformations in Earth’s physical and biological evolution during the subsequent Neoproterozoic.
A conspicuous absence of glaciation suggests a billion years of warm climates, yet the relationship between temperature and greenhouse gas concentrations remains enigmatic. Separately, contradictory estimates of atmospheric oxygen levels convolute our understanding of how they influenced biological evolution.
Our gas analyses from 1.4 Ga primary fluid inclusions directly constrain Mesoproterozoic oxygen and carbon dioxide concentrations to 3.7% modern levels and 10 times preindustrial levels, respectively.
Our results show this was a period of equable climate and that atmospheric oxygen concentrations, at least transiently, surpassed the metabolic requirements of early animals long before their emergence.
Astrobiology
