Aven du Lauza

L'Aven du Lauza begins with a crawlway that reaches -3 m at a narrow P.20 with a tight top. A flat slab overhangs a P.16 followed by an inclined joint (T.20) climbable as a scramble that leads to -60 m. A narrow 5 m fault opens into a stretch of gallery choked with blocks. The loose ascending passage connecting with L'Aven François opens mid-gallery. A small forced conduit marks the start of the « Caprices de Jupiter » at -56 m; it emerges 6 m from the bottom of an ascending shaft. Opposite, a rough ascent in a fissure leads to an S-shaped squeeze followed by a low, muddy descending conduit at whose end the « Caprices de Jupiter » end. Two fine shafts (P.11, P.19) with fluted walls lead, after a step down among blocks, to the « Salle de la Perle »: a high joint (up to 30 m) 15 m long and 6 m wide, connecting at roof level with the base of the P.11. To the South, a climb reaches after 20 m a small chamber with an incoming chimney. At the foot of the climb, a crawlway regains the joint one level lower, which turns into a narrow meander choked with blocks hindering progress. A small forced conduit appears: the « Snake Boyau ». 10 m long, it ends in a selective crawlway at the top of a P.23 that requires a somewhat acrobatic move onto a small ledge. The shaft continues as a thin fissure containing a particularly tight passage (old bottom). The cave ends at -165 m at a pinch in the walls at the base of a P.15 that is descended by climbing.

L'Aven François begins with a rather narrow R.8 in several steps, cut by a block 2 m from the bottom. After a squeeze, an R.3 leads to the top of a fine P.25. Nine metres lower, a ledge allows access to other parallel shafts. At the bottom of the shaft, a steep, calcite-cemented scree slope reaches a 10 m stretch of gallery at -52 m. At the base of the scree, a narrow passage in the bottom of a funnel of blocks leads into the loose descending conduit that joins the normal route of the Lauza at -60 m.

Both caves develop in compact limestones with a pale grey patina, grey on fresh fracture, of Middle Devonian age. They follow the same bed oriented N 300°, dipping 50° to 65°. From the « Salle de la Perle » to the end of the « Snake Boyau », the cave follows a conformable oblique fault marked by crushing and calcite veins. The displaced compartment is to the East, while traces of slickensides remain on the west side.

The hydrology amounts to a few seepages during rainy weather.

For the speleomorphology and speleogenesis (hypotheses) of the cave, refer to the article by C. Bès.