Coupled Cr and Mo isotope investigations of post-GOE Paleoproterozoic sediments: Testing the hypothesis of an oxygen overshoot in atmospheric O2 levels
Mineralogy, Petrology and Geochemistry
Final Report Abstract
In summary, this projected investigated the elemental and Cr isotopic composition of various 2.5 to 2.0 billion-year-old terrestrial and shallow-marine sediments from the Fennoscandian Shield in Karelia (NW Russia). The results of this project indicate that (1) Cr was mobilized on the Paleoproterozoic continents to due increasing atmospheric oxygen levels during the Lomagundi-Jatuli Event and produced soluble Cr(VI) that was transported to the oceans, (2) positive δ53Cr values in Lomagundi-Jatuli sediments record the presence of a marine Cr(VI) pool and thus an oxygenated ocean-atmosphere system, (3) the presence of positive δ53Cr values in post-Lomagundi sediments indicates that the ocean-atmospheric system remained well oxygenated at least until 2.0 Ga, (4) the positive δ53Cr values in organic- and phosphorous-rich sediments of the 2.0 Ga Zaonega Formation identify Cr drawdown by sinking organic particles in high productivity post-Lomagundi oceans. Consequently, the outcome of our project identified a highly dynamic Cr redox cycling in the early Paleoproterozoic.
Publications
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(2019): Cr isotopes in 2.5 to 2.0 billion-year-old sediments from Fennoscandia as tracer for Paleoproterozoic atmospheric oxygen levels. IODP/ICDP Kolloquium at the University of Cologne
Eickmann, B., Kleinhanns, I.C., van Zuilen, M., Schoenberg, R.
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(2020): The onset of oxidative weathering traced by uranium isotopes. Precambrian Research 338
Brüske, A., Martin, A.N., Rammensee, P., Eroglu, S., Lazarov, M., Albut, G., Schuth, S., Aulbach, S., Schoenberg, R., Beukes, N., Hofmann, A., Nagler, T. and Weyer, S.
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(2020): Weathering, alteration and reconstructing Earth's oxygenation. Interface Focus 10
Planavsky, N.J., Robbins, L.J., Kamber, B.S. and Schoenberg, R.
