8000-6000 year-old anthropically broken stalagmite structures up to 2km deep in the cave of Saint-Marcel, France: Traversing and using underground caves during the Early Holocene.

Abstract The cave of Saint-Marcel is known for its extensive network (64 km of galleries) and its history of human occupation (Middle Paleolithic and Neolithic) in the entrance area. Close observation of the main network reveals areas with high concentrations of broken speleothems, which are usually attributed to the first tourist visits of the 19th century. However, archaeo-geomorphological mapping of the broken speleothems, many of which are lying on the floor and sealed by stalagmite regrowth or crust, indicates intentional organisation of the underground space into speleothem supply zones and zones in which the speleothems were used to build structures. Age estimates of the stalagmite seals on these human-made structures suggest that the structures were a result of human activity that occurred between the end of the Upper Palaeolithic and the European Mesolithic. These age estimates radically change the way we look at the broken speleothems in the cave of Saint-Marcel and the structures associated with them. They bring to light the engagement of past human communities with the deep underground environment, at more than 1.5 km from the cave entrance, which can only be accessed by crossing obstacles (pits) that are considered to be difficult to cross today. Our findings as well as ongoing research highlight the unequivocal archaeological significance of the cave.