Atmospheric oxygenation driven by unsteady growth of the continental sedimentary reservoir

- We present data that characterizes the net history of continental sedimentation.
- We show that this sedimentation history covaries with the history of pO2.
- We develop a forward pO2 model based upon this empirical history.
- This model predicts two rises in pO2 separated by three stable plateaus.
- These results suggest that modes in continental sedimentation dictate pO2.

Atmospheric oxygen concentration has increased over Earth history, from ∼0 before 2.5 billion years ago to its present-day concentration of 21%. The initial rise in pO2 approximately 2.3 billion years ago required oxygenic photosynthesis, but the evolution of this key metabolic pathway was not sufficient to propel atmospheric oxygen to modern levels, which were not sustained until approximately two billion years later. The protracted lag between the origin of oxygenic photosynthesis and abundant O2 in the surface environment has many implications for the evolution of animals, but the reasons for the delay remain unknown. Here we show that the history of sediment accumulation on continental crust covaries with the history of atmospheric oxygen concentration. A forward model based on the empirical record of net organic carbon burial and oxidative weathering of the crust predicts two significant rises in pO2 separated by three comparatively stable plateaus, a pattern that reproduces major biological transitions and proxy-based pO2 records. These results suggest that the two-phased oxygenation of Earth's surface environment, and the long delays between the origin of life, the evolution of metazoans, and their subsequent diversification during the Cambrian Explosion, was caused by step-wise shifts in the ability of the continents to accumulate and store sedimentary organic carbon. The geodynamic mechanisms that promote and inhibit sediment accumulation on continental crust have, therefore, exerted a first-order control on the evolution of Earth's life and environment.