The prehistoric porch and its sealing

The contribution of 3D geomorphology

The current entrance networks do not permit visualisation of the physiognomy of the prehistoric entrance to the cave. Geomorphological surveys combined with 3D laser scanning have made it possible both to understand how the cave was sealed and also to reconstruct the prehistoric porch.

The collapse of the cliff and the sealing of the prehistoric cave

Evaluation by means of 3D data of the volume having fallen from the cliff, compared to that of the scree which conceals the cave, emphasises that the collapse of the cliff which dominated the prehistoric porch was the sole cause of its closure. Geomorphological surveys of the scree and the area of the collapse have suggested that the sealing process occurred in three stages. Cosmogenic dating carried out in the area of the collapse has enabled the dating of three phases of collapse: around 29,400, 23,500 and 21,500 years BP. Comparing these dates with those for charcoal and bone indicates that the first collapse marks the end of the second period of human occupation (Gravettian), while the end of animal occupation follows the second collapse of the cliff (23,500 years BP). The final collapse definitively sealed the prehistoric entrance.

The reconstruction of the prehistoric porch

The geomorphological survey, combined with the 3D data, has enabled an accurate understanding of the position and morphology of the walls and ceiling of the original cave porch; the survey carried out on the base of the entrance scree made possible the determination of the archaeological floor contemporary with prehistoric occupations. On the basis of these landmarks, a reconstruction of the prehistoric entrance to the cave has been carried out: it was a majestic entrance almost 10 m in height and 15 m across.