Synsedimentary fault control on the deposition of the Duitschland Formation (South Africa) : implications for depositional settings, Paleoproterozoic stratigraphic correlations, and the GOE
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The Paleoproterozoic Great Oxidation Event (GOE) marks the first significant oxidation of atmosphere and surface environments, and is causally associated with the global disappearance of mass-independent sulfur isotope fractionation (MIF-S). However, fundamental sedimentary aspects of sedimentary successions recording this event (e.g. depositional environment, tectonic setting and stratigraphic correlation) are poorly constrained and often debated, restricting full understanding of causes and effects related to the GOE. In South Africa, MIF-S disappears across the ‘mid-Duitschland unconformity’ (MDU) in the Duitschland Formation (Transvaal Supergroup). New sedimentological observations of the lower Duitschland Formation have identified up to 5 times thicker and more diverse chert-pebble conglomerates than previously documented. New facies observed include lenticular conglomerates which incise cross-bedded dolomites, and imbricated conglomerates. The overlying MDU is angular in nature, recording an ∼15° N dip of the lower Duitschland strata; elsewhere it possesses a disconformable geometry. A new depositional model is proposed where shallow-marine carbonate (ramp) deposition interfaced with wave-influenced Gilbert-type fan deltas in an isolated depocentre produced during synsedimentary faulting. There is no evidence that the MDU formed due to direct glaciation as proposed previously, however glacio-eustatic changes may have had an influence. This study supports lithostratigraphic correlations between the Duitschland and Rooihoogte formations which both register the MIF-S disappearance, but are considered separate lithostratigraphic units, which implies oscillations in MIF-S. The correlation proposed in this study implies a unique MIF-S signal and has important consequences for differentiating true spatiotemporal oscillations in MIF-S chemistry from artificial variations caused by unresolved stratigraphic relations.
Warke , M R & Schröder , S 2018 , ' Synsedimentary fault control on the deposition of the Duitschland Formation (South Africa) : implications for depositional settings, Paleoproterozoic stratigraphic correlations, and the GOE ' , Precambrian Research , vol. 310 , pp. 348-364 . https://doi.org/10.1016/j.precamres.2018.03.001
© 2018 Elsevier Ltd. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1016/j.precamres.2018.03.001
DescriptionMRW was supported by a NERC-studentship through the University of Manchester. MRW also acknowledges financial support from IAS via a postgraduate grant. SS was supported through a Strategy Grant of the Faculty of Engineering and Physical Sciences at the University of Manchester.
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