Evidence for a gradual rise of oxygen between 2.6 and 2.5Ga from Mo isotopes and Re-PGE signatures in shales
M. Wille, J.D. Kramers, T.F. Nagler, N.J. Beukes, S. Schroder, T. Meisel, J.P. Lacassie, A.R. Voegelin May 2007 Geochimica et Cosmochimica Acta Volume 71, Issue 10, Pages 2417-2435
This article reports geochemical findings concerning the question of how and when free oxygen started to accumulate in the Earth's atmosphere and hydrosphere. The paper reports Molybdenum concentrations and Platin group element and Rhenium (PGE-Re) data from black shales of the Transvaal Supergroup. For comparison, new data is also included from the 3.23 Ga Fig Tree Group, Barberton Greenstone Belt. Such data are important proxies for changes in oxygen levels of the early atmosphere and oceans. The authors report a that the general increase in Mo concentrations and isotope fractionation indicates a gradual rise of oxygen between 2.64 and 2.5 Ga.