Chemostratigraphy of a Paleoproterozoic BIF-MnF succession - the Voelwater Subgroup, Transvaal Supergroup, South Africa

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When and how the oxygen content of the Earth s atmosphere rose and how this build-up of oxygen reflects the evolution of photosynthesis and early microbial life constitutes an important unresolved question in Earth System Sciences. The rise of atmospheric oxygen may in fact have been efficiently delayed until the late Paleoproterozoic by the deposition of banded iron formations (BIF) and manganese formations (MnF). Until today, the exact origin of BIF and MnF successions, chemical sediments that have no analogue in the Phanerozoic, has not found an unequivocal explanation. The early Paleoproterozoic Hotazel Formation, Transvaal Supergroup, South Africa, is a unique succession of BIF and MnF, accompanied by shallow water stromatolitic dolomites. The succession is virtually undeformed and unmetamorphosed, is extremely well exposed and hosts the world s largest resource of minable manganese ore. The Hotazel Formation is, thus, the ideal unit to conduct a systematic chemostratigraphic study focusing on stable (C, O) and radiogenic (Sr, Pb, Nd, Hf) isotope systematics in order to constrain the factors that controlled precipitation and spatial separation of BIF, MnF and shallow water carbonates during this critical interval of Earth s history.