Aven de l'Érable

The entrance is circular (0.8 metre in diameter) and two steps of 3 and 2 metres lead into a stony chamber. Two gallery starts, quickly choked, appear to the northwest and southeast. The continuation that was dug open is Un narrow passage under collapsed strata in the west wall of the chamber. This low passage, 4 metres long, opens into a fairly vast gallery cluttered with blocks. On the north side it rises 13 metres to -2 m, very close to the surface.

On reaching this gallery, Un conduit descending through the blocks and Un step lead onto a choked gallery. Another side passage is accessible through the west wall; it is 10 metres long. On the south side the gallery descends, narrows slightly at blocks detached from the roof, then regains a good size over 15 metres of length. The floor is flat and calcited, then the ceiling lowers and almost meets the floor. On the left side, Un petit trou dug open in the calcite gives onto Un narrow P11 that ends in two small fissures in primary schists reached at about -18 m. Halfway down the shaft Un dug-open crawl leads into a well-formed gallery but quickly blocked. At the bottom, the primary terrain prevents any development. Above, the gallery rises but stops at blocks that would need to be cleared.

To the east is a very concretion-covered chimney (flowstone, dog-tooth spar) that must not be damaged; it rises to -12 m. The upper galleries are choked by concretion.

Alveolina limestones of the Ypresian (Eocene). The thickness of the limestone at this point is about 18 m. The dip is almost nil. One reaches the contact with the primary (Acadian schists, c3) which limits penetration. It should be noted that the Aven des Lacs, located 200 m to the north, descends more than 50 m, thus crossing the Tertiary and penetrating into the Primary which must here be limestone (Archaeocyathus limestones - Georgian).