Depth-dependent δ13C trends in platform and slope settings of the Campbellrand-Malmani carbonate platform and possible implications for Early Earth oxygenation
Date
2017-11
Authors
Eroglu, Suemeyya
van Zuilen, Mark
Taubald, Heinrich
Drost, Kerstin
Wille, Martin
Beukes, Nicolas J.
Schoenberg, Ronny
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Elsevier B.V.
Abstract
The evolution of oxygenic photosynthesis is widely seen as the major biological factor for the profound shift from reducing to slightly oxidizing conditions in Earth’s atmosphere during the Archean-Proterozoic transition period. The delay from the first biogenic production of oxygen and the permanent oxidation of Earth’s atmosphere during the early Paleoproteorozoic Great Oxidation Event (GOE) indicates that significant environmental modifications were necessary for an effective
accumulation of metabolically produced oxygen. Here we report a distinct temporal shift to heavier carbon isotope signatures in lagoonal and intertidal carbonates (δ13Ccarb from -1.6 to +0.2 ‰, relative to VPDB) and organic matter (δ13Corg from about -40 to -25 ‰, relative to VPDB) from the 2.58-2.50 Gy old shallow-marine Campbellrand-Malmani carbonate platform (South Africa). This indicates an increase in the burial rate of organic matter caused by enhanced primary production as
well as a change from an anaerobic to an aerobic ecosystem. Trace element data indicate limited influx of reducing species from deep open ocean water into the platform and an increased supply of nutrients from the continent, both supporting primary production and an increasing oxidation state of the platform interior. These restricted conditions allowed that the dissolved inorganic carbon (DIC) pool in the platform interior developed differently than the open ocean. This is supported by coeval carbonates from the marginal slope setting, which had a higher interaction with open ocean water and do not record a comparable shift in δ13Ccarb throughout the sequence. We propose that the emergence of stable shallow-water carbonate platforms in the Neoarchean provided ideal conditions for the evolution of early aerobic ecosystems, which finally led to the full oxidation of Earth’s atmosphere during the GOE.
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Comments
This is a manuscript of an article published as Eroglu, Suemeyya, Mark A. van Zuilen, Heinrich Taubald, Kerstin Drost, Martin Wille, Elizabeth D. Swanner, Nicolas J. Beukes, and Ronny Schoenberg. "Depth-dependent δ13C trends in platform and slope settings of the Campbellrand-Malmani carbonate platform and possible implications for Early Earth oxygenation." Precambrian Research 302 (2017): 122-139. doi: https://doi.org/10.1016/j.precamres.2017.09.018.
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This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.