Estimation of nutrient input into Late Ediacaran marine systems via numerical box modelling of Li isotope data of carbonate rocks from the Corumbá and Bambuí Groups, Brazil

Abstract

he rise of the first complex organisms at the end of the Ediacaran period (635 to 541 Ma) is one of the most intriguing episodes in the history of the Planet. The causes for such move of life to its complex forms remain unclear. An enhanced influx of nutrients into the ocean via chemical weathering of large continental masses is one of the leading hypotheses to explain it. This high nutrient availability may have driven biological activity thus leading to life radiation. However, this hypothesis is still poorly tested at the global scale, and detailed geochemical studies on marine sedimentary successions of the Terminal Ediacaran are required. Two of these successions are in Brazil: the Corumbá Group (west Brazil) and the Bambuí Group (east central). They are the targets of the post-doctoral project "Chemical Weathering and nutrient input into Late Ediacaran ocean and their relationship to life diversification" (FAPESP #2017/00399-1), which is currently applying a combination of Rare Earth Elements mass fractions and lithium (Li) isotopes in carbonate rocks to track the chemical weathering inputs into late Ediacaran marine systems. Particularly, Li isotopes have emerged as one of the most promising tools to quantify weathering influxes to ancient basins. This Research Internship Abroad proposal aims to estimate Li influxes to marine systems via numerical box models and check their relationships to the biogeochemical record. Duplicate tests will also be performed to assure the quality of the Li isotope measurements implemented in Brazil. The project will be supervised by Prof. Dr. Simone Kasemann at the MARUM-Center for Marine Environmental Sciences, University of Bremen, Germany, who has broad experience with chemical weathering proxies.