New insights into the Cosquer art cave hydrogeological functionning (France)

International audienceThe Cosquer cave supports and protects some paleolithic paintings and engravings, dated to more than 31,000 years (Cal BP, Valladas et al. 2016). It’s a coastal cave, located in the Calanques massif, near Marseille in south of France. This area is well-known for its karstic landscape, in the white urgonian limestones (Barremian, early cretaceous). Nowadays, the cave has no water-free entrance. The only way to access to the cave is to dive to a submarine entrance giving access to a karst conduit connected with the non-flooded part of the cave. During paleolithic times, the seawater level was lower (down to 135 m). The access to the cave to the paleolithic men was flooded by the Mediterranean Sea rise around 10,000 years (Cal BP, Lambeck & Bard 2000). This specific location of the cave offered a protected area for the conservation of the rock art: no man entrance during the historical time, climatic and environmental steady conditions. Moreover, the karst also protected the rock art because it limited the sea-level rise within the cave. Indeed, the water level inside the Cosquer cave is lower than the sea-level, although only a tens of meters of limestones separate the cave to the sea. Obviously, the cave is a confined environment and is an interesting case-study to understand the impact of permeability contrasts between open karst features and the surrounding matrix. The aims of this work are: (1) to present a first long pressure time series ever recorded in the Cosquer cave, (2) to show which phenomena control the water level variation inside the cave, in order to answer to the following questions: when, how high and why the water level varies in the cave