Paired sulfur and carbon isotope analysis of Brazilian Ediacaran carbonate rocks and inferences on the West Gondwana marine biogeochemical cycles

Abstract

Great biological innovations associated with major geochemical disturbances characterize the Ediacaran geological record, at the end of Neoproterozoic Era, which are attributed to the final oxygenation of Earth's surface environments. Carbon and sulfur stable isotopes studies are key tools for inferences of major oxidation events in the marine environment, close related in time with the appearance of complex metazoan assemblages. Despite the existence of punctual Ediacaran intervals presenting coupled carbon and sulfur isotope anomalies worldwide, an increasing number of studies point to complex geochemical models which vary from basin to basin, given local paleoenvironmental/paleogeographic controls. These results justify the need of detailed isotope geochemistry studies integrated with a proper sedimentological/stratigraphic assessment. For this purpose, the current doctorate project entitled "Carbon and sulfur biogeochemical cycles in the Brazilian Ediacaran record" (FAPESP #2016/11496-5) investigate two different Ediacaran settings from Brazil, aiming to provide and compare the coupled carbon and sulfur isotope evolution from each context. In the central-east Brazil, the Bambuí Group, São Francisco Basin, corresponds to an Ediacaran epicontinental basin with a very poor fossil record and major carbon isotope disturbances probably associated with basin restriction. On the other hand, the Corumbá Group, South Paraguay Belt (central-west Brazil), encompasses a rich paleontological record in a dynamic Ediacaran carbonate platform. The paired carbon and sulfur isotope study (organic carbon-carbonates and sulfide-sulfate pairs) will allow improvements in inferences about the carbon and sulfur biogeochemical cycles of each context of the West Gondwana (restricted marine vs open marine). This will lead to advances in the reconstruction of geochemical dynamics and life distribution on the Ediacaran marine settings. This Research Internship Abroad (BEPE) requirement is intended to be developed at the Department of Stable Isotope Geochemistry of the Institut de Physique du Globe de Paris, France, which has excellent scientific conditions to carry out carbon and sulfur isotope investigations applied to ancient environments.