Tanne à la R'Noïlle

The galerie des aveugles is a fissure gallery, not very high and 0.5 to 1 m wide. The salle des cris-taux follows a widening of the gallery. The puits du Pessimiste (P 18) gives access to a chamber 7 m in diameter. The active network includes a low-gradient meander, 1 m wide and several metres high. The galerie de l'Obélisque is shaped like a 3 m diameter pressure conduit. The galerie des 3 cierges is a pressure-conduit gallery formed along a bedding joint, overdeepened by a secondary stream over about ten metres of depth. The pit begins with a small collapse doline; a narrow diaclase allows descent in opposition to the top of the puits Carole. This diaclase opens at the surface through 2 orifices, thus forming 2 P 20 at the surface. The P 176 is bordered along half its circumference by a ledge 0.5 to 1 wide; at the north-west end of this ledge, a window opens onto a 30 m shaft that rejoins the P 176. A platform 4 m below the lips of this shaft allows an easy start. The puits Carole is slightly bell-shaped; its section, 3 to 4 metres by 6 to 8 metres at the top, becomes 15 metres by 20 metres at its base. The bottom of the shaft consists half of a massive rock bed and half of a stony floor 2 metres lower (elevation -206). Two galleries open at the base of this shaft thanks to the F6 fault: one to the west leads to the réseau Aval, the other to the east leads to the réseau Amont.

The active network is traversed by a stream of 2 to 5 l/second at low water. The water flows on the Hauterivian bedrock. The active network ends downstream at a duck-under after 35 m of travel; upstream, an 80 m navigation leads to a duck-under. The semi-active network has an upstream part and a downstream part: upstream, the gallery gives access via 2 parallel shafts to a 2nd part of the active network which, on both sides, after a short traverse, ends at duck-unders; downstream, the gallery gives access via a 6 m step to the active network. In the active network, upstream, a quick traverse leads once again to a duck-under; downstream, as soon as the general westward direction is left for a northward direction, the slope steepens and steps appear, the shape of the gallery changes, and finally there is the sump at -275 m. The galerie du Coccyx ends at a duck-under (elevation -269).

After the bivouac chamber, a crawl gives access to a shaft blocking the passage; the continuation is opposite after descending and ascending 4 m in this shaft. The junction with the semi-active network can be made in 2 ways: through a low passage (on the left) and a pressure-conduit-shaped gallery 0.5 wide, or through a small meander followed by a trickle of water. Below the start of the galerie des aveugles, the puits du Pessimiste (P 18) gives access to a chamber 7 m in diameter, then a step leads to a 1st part of the active network (elevation -228 m). In the active network, several starts exist: the 1st on the left forms the galerie de l'Obélisque; on the left, it rises gradually to rejoin the active network higher up; on the right, it constitutes the upper part of the active gallery before finally leaving it and forming the galerie du Coccyx. At the same level as the previously mentioned start, but on the right, the galerie des 3 cierges begins.