Neoproterozoic uppermost Haut-Shiloango Subgroup (West Congo Supergroup, Democratic Republic of Congo): Misinterpreted stromatolites and implications for sea-level fluctuations before the onset of the Marinoan glaciation

Abstract

The middle Neoproterozoic carbonate-dominated uppermost Haut-Shiloango Subgroup (Sh8h and Sh8i members) in the Lower-Congo Province of the Democratic Republic of Congo is considered as recording pre-glacial shallow-marine sedimentation with stromatolitic reefs overlain by the Upper Diamictite Formation. We investigated these stromatolitic carbonates in order to highlight their biogenicity. Newly defined lithofacies and geochemical analyses (stable isotopes, major, trace and REE+Y elements) are used to provide insights into the origins of the depositional events that occurred immediately before Marinoan global glaciation. These insights should in turn provide constraints on the models developed for this glaciation event. The series consists of three shaly and carbonate lithofacies: (i) alternating limestones and claystones (lithofacies 1); (ii) nodular wackestones (lithofacies 2); and (iii) clast-supported conglomerates and breccias (lithofacies 3). Lithofacies 1 is...