Sulfur record of rising and falling marine oxygen and sulfate levels during the Lomagundi event
- 22 October 2012
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 109 (45), 18300-18305
- https://doi.org/10.1073/pnas.1120387109
Abstract
Carbonates from approximately 2.3-2.1 billion years ago show markedly positive δ(13)C values commonly reaching and sometimes exceeding +10‰. Traditional interpretation of these positive δ(13)C values favors greatly enhanced organic carbon burial on a global scale, although other researchers have invoked widespread methanogenesis within the sediments. To resolve between these competing models and, more generally, among the mechanisms behind Earth's most dramatic carbon isotope event, we obtained coupled stable isotope data for carbonate carbon and carbonate-associated sulfate (CAS). CAS from the Lomagundi interval shows a narrow range of δ(34)S values and concentrations much like those of Phanerozoic and modern marine carbonate rocks. The δ(34)S values are a close match to those of coeval sulfate evaporites and likely reflect seawater composition. These observations are inconsistent with the idea of diagenetic carbonate formation in the methanic zone. Toward the end of the carbon isotope excursion there is an increase in the δ(34)S values of CAS. We propose that these trends in C and S isotope values track the isotopic evolution of seawater sulfate and reflect an increase in pyrite burial and a crash in the marine sulfate reservoir during ocean deoxygenation in the waning stages of the positive carbon isotope excursion.Keywords
This publication has 53 references indexed in Scilit:
- Oxygen overshoot and recovery during the early PaleoproterozoicEarth and Planetary Science Letters, 2011
- Global nature of the Paleoproterozoic Lomagundi carbon isotope excursion: A review of occurrences in Brazil, India, and UruguayPrecambrian Research, 2010
- A review of the stratigraphy and geological setting of the Palaeoproterozoic Magondi Supergroup, Zimbabwe – Type locality for the Lomagundi carbon isotope excursionPrecambrian Research, 2010
- Animal evolution, bioturbation, and the sulfate concentration of the oceansProceedings of the National Academy of Sciences of the United States of America, 2009
- The carbon cycle and associated redox processes through timePhilosophical Transactions Of The Royal Society B-Biological Sciences, 2006
- Evidence for Paleoproterozoic cap carbonates in North AmericaPrecambrian Research, 2005
- Accumulation rates from well-dated late Neogene carbonate platforms and marginsSedimentary Geology, 2005
- The sulfur isotopic evolution of Phanerozoic seawater based on the analysis of structurally substituted sulfate in carbonatesChemical Geology, 2004
- Volcanic gases, black smokers, and the great oxidation eventGeochimica et Cosmochimica Acta, 2002
- Accumulation Rates of Carbonate PlatformsThe Journal of Geology, 1993