Paradigm shift in determining Neoproterozoic atmospheric oxygen

Nigel J. F. Blamey , Uwe Brand , John Parnell , Natalie Spear , Christophe Lecuyer (1) , Kathleen Benison , Fanwei Meng , Pei Ni

1 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement

We present a new and innovative way of determining the oxygen level of Earth's past atmosphere by directly measuring inclusion gases trapped in halite. After intensive screening using multiple depositional, textural/fabric, and geochemical parameters, we determined that tectonically undisturbed cumulate, chevron, and cornet halite inclusions may retain atmospheric gas during crystallization from shallow saline, lagoonal, and/or saltpan brine. These are the first measurements of inclusion gas for the Neoproterozoic obtained from 815 +/- 15-m.y.-old Browne Formation chevron halite of the Officer Basin, southwest Australia. The 31 gas measurements afford us a direct glimpse of the composition of the mid-to late Neoproterozoic atmosphere and register an average oxygen content of 10.9%. The measured pO(2) puts oxygenation of Earth's paleoatmosphere similar to 100-200 m.y. ahead of current models and proxy studies. It also puts oxygenation of the Neoproterozoic atmosphere in agreement with time of diversification of eukaryotes and in advance of the emergence of marine animal life.

Domaines: Planète et Univers [physics]

Nigel J. F. Blamey, Uwe Brand, John Parnell, Natalie Spear, Christophe Lecuyer, et al.. Paradigm shift in determining Neoproterozoic atmospheric oxygen. Geology, 2016, 44 (8), pp.651-654. ⟨10.1130/G37937.1⟩. ⟨hal-02331393⟩