Isotope geochemistry and biomarkers in Archaean terranes and in their modern analogues systems: environmental constraints and ecology of early Earth life

Abstract

This research project has the major goal of identifying the environmental constraints and chemical signatures of life in the anoxic systems prevailed in the Archean. Archean sedimentary sequences have the potential to record the early oxygen generation in the atmosphere (around 3.0 Ga), and the subsequent build-up of sulfate and sulfide in the oceans (developing euxinic systems) near the transition to the Paleoproterozoic. This project proposes a major scientific advance in this research field by simultaneously applying different proxies to Archean sedimentary sequences from the São Francisco Craton and in sediment cores from modern anoxic basins (meromictic lakes - permanently stratified systems) to reconstruct the environmental conditions that provided life in the early Earth. The combined study of Archean rocks and recent sediments from meromictic lakes, known as modern analogues of early Earth systems, will support the understanding of the processes and the triggers for anoxia and help their interpretation in the geologic record. This integrate study will be conducted by using a combination of isotopic geochemistry (´13C; ´15N; ´34S), trace elements (e.g., U, V, Mo, Ni, As, Cu, Mn, Zn, Se), and organic biomarkers (okenone and isorenieratene) techniques, to provide information about changes in environmental conditions and support inferences of how they interacted with life in the early Earth.