Grotte du Moulin de Laguenay

The accessible part of the Grotte is developed over only 35 metres, in a N-S direction. The entrance zone is collapsed. The current entrance is a narrow crawlway that forms “(…) a one-metre-long, 50 cm diameter passage descending towards the entrance collapse.” The current entrance is therefore narrow and opens into a scree of large blocks. The vault is locally flat along the limestone slabs or shows “vault channel”-type scours, evidence of secondary excavation by flow over a fill occupying the original drain. Beyond the scree, the fill slopes gently towards the back. The gallery is then 6 m wide, for a height of about 3.50 m. In the centre of the cavity, a muddy depression with a flat floor about fifteen metres long and 4 metres wide on average is bordered by banks of gravel and especially of sand and silt along the south wall. Towards the back of the cavity, the clay-silt fill rises fairly quickly (over about 6 metres) up to beneath the decorated part. The Grotte continues as a small inaccessible squeeze.

Speleothems are locally present but weakly developed (small soda straws and calcite coatings).

The hypothesis of a natural collapse and piping is not compatible with the flat-floored morphology and the almost permanent presence of water or of 20 centimetres of liquid clay. It seems more plausible that a large part of the sandy material was mined in the past. The bank would be a remnant of the original fill. This is a hypothesis to be tested.