Biogenic silica and organic carbon fluxes provide evidence of enhanced marine productivity in the Upper Ordovician-Lower Silurian of South China

Abstract Biogenic silica is a powerful palaeoproductivity proxy in palaeomarine environments and is significant within shale gas reservoirs, demonstrating the association of marine hydrocarbon source rocks with the abundance of micro-siliceous fossils, yet detailed studies that investigate this strong alliance in the Ordovician-Silurian transition are still lacking. The bulk of TOC in marine sediments is commonly assumed to have been derived predominantly from marine phytoplankton, with modern ocean surveys indicating good correspondence between silica content and primary productivity. This study discovers a strong positive correlation between biogenic silica (Bio-Si) and TOC in the Upper Ordovician-Lower Silurian Wufeng and Longmaxi formations of South China in the Jiaoye 41-5 (R = +0.68, p(α)