Sediment and organic carbon discharges to the coastal oceans by badlands (English Channel, Normandy, France)

Determining sedimentary and organic carbon fluxes and sources within the sedimentary continuum from land to sea is crucial for improving the understanding of Earth system dynamics, global carbon budgets and associated biogeochemical cycles, especially in the context of Global Change. Among continental sources, marly badlands, characterized by high erosion rates and significant Total Organic Carbon (TOC) contents, are potential contributors of material to the sea. However, data on sediment and TOC yields, fluxes and the contribution of badlands to the marine environment are still limited, particularly in NW Europe and oceanic regions. In this context, the instrumented sites of Vaches Noires cliffs on the western Normandy coast, France, were studied over three years. Suspended Particulate Matter (SPM) and source samples were collected along the eastern part of the cliff. Geochemical analyses, sediment fluxes and yields were obtained and compared with those from local rivers, European badlands and worldwide Small Mountain River systems (SMRs). These first results show that the cliffs exhibited high productivity in terms of sediment and organic carbon (OC) yields, like other studied badlands. Reaching the English Channel, material from badlands can enter and sediment within the Seine estuary, contributing to the Turbidity Maximal Zone and mixing with other OC sources (such as primary productivity and continental OC). Although the contribution of this material to the carbon (C) budget of this interface remains uncertain, it could be significant, especially with the increase in global sea level and major rainfall events.