Year: 2020
Type: article
Abstract: Widespread deposition of iron-rich sedimentary rocks (ironstones) occurred during the Sturtian ice age, the earlier of two Cryogenian 'Snowball Earth' glaciations.However, the reasons for the termination of Cryogenian Iron Formation (CIF) deposition remain poorly understood.Here we report a multi-isotope (Fe-C-S) study of the Xinyu CIF in South China that can directly address this question.The isotopic compositions of these multivalent elements exhibit remarkable covariance at the top of the Xinyu CIF that reflects progressive redox stratification during iron oxide deposition.Iron oxide deposition ended abruptly due to the titration of ferrous iron as pyrite following a large influx of riverine sulfate.Although termination of CIF deposition is commonly attributed to oxygenation, our data show that at least in some Cryogenian ocean basins, CIF deposition ended with the spread of euxinic rather than oxygenated waters.
Source: Geochemical Perspectives Letters
Institutions: Nanjing University, University College London
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W3045104237