Marnes de Foncouverte is a geological formation in France. It is primarily known for its rich deposits of marl, a type of sedimentary rock that is composed of calcium carbonate and clay. The name “Marnes de Foncouverte” literally translates to “Marls of Foncouverte,” indicating the location of these deposits in the commune of Foncouverte, in the Charente-Maritime department of southwestern France.