Contributions of U-Th-Pb dating on the diagenesis and sediment sources of the lower group (BI) of the Mbuji-Mayi Supergroup (Democratic Republic of Congo)

In this paper, we present new age constraints for the lower part of the Meso-Neoproterozoic sedimentary Mbuji-Mayi Supergroup (Democratic Republic of Congo, DRC). This Supergroup preserves a large diversity of organic-walled microfossils, evidencing the diversification of early eukaryotes for the first time in Central Africa. We use different methods such as in situ U-Pb geochronology by LA-ICP-MS and U-Th-Pb chemical datings by Electron Microprobe on diagenetic and detrital minerals such as xenotimes, monazites and zircons. We attempt to better constrain the provenance of the Mbuji-Mayi sediments and the minimum age of the Mbuji-Mayi Supergroup to constrain the age of the microfossils. Results with LA-ICP-MS and EMP provide new ages between 1030 and 1065 Ma for the diagenesis of the lower part of the sedimentary sequence. These results are consistent with data on biostratigraphy supporting the occurrence of worldwide changes at the Mesoproterozoic/Neoproterozoic boundary.