Atmospheric oxygenation three billion years ago

TY - JOUR

T1 - Atmospheric oxygenation three billion years ago

AU - Crowe, Sean

AU - Døssing, Lasse Nørbye

AU - Beukes, Nicolas J.

AU - Bau, Michael

AU - Kruger, Stephanaus J

AU - Frei, Robert

AU - Canfield, Donald Eugene

PY - 2013

Y1 - 2013

N2 - It is widely assumed that atmospheric oxygen concentrations remained persistently low (less than 10 -5 times present levels) for about the first 2 billion years of Earth's history. The first long-term oxygenation of the atmosphere is thought to have taken place around 2.3 billion years ago, during the Great Oxidation Event. Geochemical indications of transient atmospheric oxygenation, however, date back to 2.6-2.7 billion years ago. Here we examine the distribution of chromium isotopes and redox-sensitive metals in the approximately 3-billion-year-old Nsuze palaeosol and in the near-contemporaneous Ijzermyn iron formation from the Pongola Supergroup, South Africa. We find extensive mobilization of redox-sensitive elements through oxidative weathering. Furthermore, using our data we compute a best minimum estimate for atmospheric oxygen concentrations at that time of 3 × 10 -4 times present levels. Overall, our findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300-400 million years earlier than previous indications for Earth surface oxygenation.

AB - It is widely assumed that atmospheric oxygen concentrations remained persistently low (less than 10 -5 times present levels) for about the first 2 billion years of Earth's history. The first long-term oxygenation of the atmosphere is thought to have taken place around 2.3 billion years ago, during the Great Oxidation Event. Geochemical indications of transient atmospheric oxygenation, however, date back to 2.6-2.7 billion years ago. Here we examine the distribution of chromium isotopes and redox-sensitive metals in the approximately 3-billion-year-old Nsuze palaeosol and in the near-contemporaneous Ijzermyn iron formation from the Pongola Supergroup, South Africa. We find extensive mobilization of redox-sensitive elements through oxidative weathering. Furthermore, using our data we compute a best minimum estimate for atmospheric oxygen concentrations at that time of 3 × 10 -4 times present levels. Overall, our findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300-400 million years earlier than previous indications for Earth surface oxygenation.

U2 - 10.1038/nature12426

DO - 10.1038/nature12426

M3 - Letter

C2 - 24067713

SN - 0028-0836

VL - 501

SP - 535

EP - 538

JO - Nature

JF - Nature

IS - 7468

ER -