Palaeoproterozoic oxygenated oceans following the Lomagundi–Jatuli Event

• Published in: Nature Geoscience
• Main Authors: Mänd, Kaarel, Lalonde, Stefan V., Robbins, Leslie J., Thoby, Marie, Paiste, Kärt, Kreitsmann, Timmu, Paiste, Päärn, Reinhard, Christopher T., Romashkin, Alexandr E., Planavsky, Noah J., Kirsimäe, Kalle, Lepland, Aivo, Konhauser, Kurt O.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Nature 2020
• Subjects: VDP::Mathematics and natural science: 400::Geosciences: 450::Stratigraphy and paleontology: 461; VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Stratigrafi og paleontologi: 461; VDP::Mathematics and natural science: 400::Geosciences: 450::Mineralogy; petrology; geochemistry: 462; VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Mineralogi; petrologi; geokjemi: 462; Arctic
• Online Access: https://hdl.handle.net/10037/19269; https://doi.org/10.1038/s41561-020-0558-5

The approximately 2,220–2,060 million years old Lomagundi–Jatuli Event was the longest positive carbon isotope excursion in Earth history and is traditionally interpreted to reflect an increased organic carbon burial and a transient rise in atmospheric O 2 . However, it is widely held that O 2 levels collapsed for more than a billion years after this. Here we show that black shales postdating the Lomagundi–Jatuli Event from the approximately 2,000 million years old Zaonega Formation contain the highest redox-sensitive trace metal concentrations reported in sediments deposited before the Neoproterozoic (maximum concentrations of Mo = 1,009 μg g −1 , U = 238 μg g −1 and Re = 516 ng g −1 ). This unit also contains the most positive Precambrian shale U isotope values measured to date (maximum 238 U/ 235 U ratio of 0.79‰), which provides novel evidence that there was a transition to modern-like biogeochemical cycling during the Palaeoproterozoic. Although these records do not preclude a return to anoxia during the Palaeoproterozoic, they uniquely suggest that the oceans remained well-oxygenated millions of years after the termination of the Lomagundi–Jatuli Event.