Aven de l'Etable (Sca)

The entrance, at ground level, is protected by a rock blade laid across it. It forms the top of a P 19 followed by an inclined plane and then a P 9. At -35, an enlarged constriction opens onto a four-metre drop. A steep, narrow passage, broken by small steps, reaches a junction at -52.

The galleries are of the “post-syngenetic” type; the original syngenetic phase seems visible in a few places in the form of small elliptical or circular conduits cut along bedding joints or fissures. These forms are visible at the top of certain meanders or galleries. At the bottom, in the upstream meander, the formation of the Galerie is clearly visible at the limestone/sandstone? contact; subsequently, the Galerie was incised deeper and shows the classic “keyhole” profile.

Galleries of the “meander” type predominate throughout the cave, except the “Galerie du Crâne” from -63 to -88, which has a gallery profile “in equilibrium” with incasion phenomena (rockfalls).

At many points, clayey, sandy and gravel deposits are noted. In the Galerie du Crâne and the Réseau du Méandre, in several places, these deposits are seen to have remained at different heights on walls or ledges, which shows that they have been incised deeper. These formations are difficult to date without a detailed study, but they still allow the evolution of certain galleries to be conceived.

The geological approach to the cave, as well as to this karst zone, is very difficult. No geologist, to our knowledge, has really worked on this region; moreover it is very difficult to recognize the different terrains. It should be noted that the description of these terrains (Devonian) on the only existing documents (geological maps at 1/80 000 Quillan and at 1/50 000 Limoux) shows major differences: it is therefore understandable that it is hazardous to pronounce on the matter.

That said, we give as location “Lower Devonian” at the entrance, but it is probable that the cave continues into the “Middle Devonian”. Without giving precise terms, we will briefly describe the facies encountered.

The entrance and the Galerie du Crâne develop in grey limestones and dolomites; the stratification is visible and on the order of 30° in direction N 220°.

The réseau du Méandre probably develops in the same formation, but the stratification is barely visible and there are many facies variations.

At -170, one comes up against a very different formation (sandy limestones or sandstones?) which forms the floor of the Galerie terminale. The contact between the two rocks is very sharp. This rock seems little suited to cave development; only very narrow, impenetrable meanders cut into the floor. We have not been able to determine the nature of this formation, but it seems to temporarily slow the speleological penetration of the cave.

As we said above, the descriptions of the terrains are hypothetical and we do not vouch for them. It is a pity that there is very little information about this region and that no one is interested in it from a geological point of view, because the aven would then provide an interesting “geological cross-section”.

The speleothems are moderate and fairly localized. Stalagmitic flows predominate (Galerie du Crâne, series of pits in the réseau du Méandre). In the Galerie du Crâne, a beautiful “drapery flow” can be seen, as well as soda straws and a few helictites. In the “fossil” meander at the bottom, a few pearls and helictites are found in the two small decorated chambers.

The aven is traversed by some seepages and is fairly humid in the rainy season. These seepages are significant enough to episodically form small streams:

• in the Galerie du Crâne, several trickles of water (including that of the entrance pits) join to form a small stream. At -105, a louder sound of water can be heard, which is perhaps the upstream of the stream at -170.
• in the réseau du Méandre, several minor inflows are noted at -130; a small stream (1 l/s in heavy flood) emerges from an impenetrable meander and falls into the 20 m pit.
• At the bottom, a perennial stream runs along the Galerie terminale for a few metres and disappears into an excessively narrow meander. It emerges from a small “sump”.
• Estimated flows: low water about 10 l/minute - average 0.5 l/s - maximum 3 l/s
• Resurgence points (see map)

Dye tracing of this stream will allow us to better define the catchment areas (exclusively underground) of two springs that drain the massif: the source du Gourdou (Théron and Biscaye) at Alet les Bains, and the source de Montjoi. The respective routes are long and presage continuations in this cave and the almost certain existence of a penetrable network beneath this sector.

• Route aven de l’Etable – Gourdou: Length = 10.5 km Vertical drop = 550 m
• Route aven de l’Etable – Monjoi: Length = 6 km Vertical drop = 400 m

Galerie DU CRANE: on the right, a 20-metre meander opens into a sloping decorated gallery 4-5 metres wide, with several side passages. A cascade of gours ends at -88 at a succession of constrictions followed by an R 5 and an R 7. A small inclined gallery leads to a fissure (-105) extended by a small active viscous meander comprising an R3 and a P 7, at the end of which a pinch blocks progress at about -125 (not surveyed since -88).

RESEAU DU MEANDRE: four drops climbed by scrambling lead into a narrow meander that opens after forty metres at the base of an ascending pit. An upper passage (handline to be installed) bypasses the narrow meander. A steep descent leads to a blasted crawlway in the boulders at -67. A short gallery oriented north shows traces of an ancient clay fill at 4-5 metres in height. A ten-metre meander arrives at the top of a series of pits and inclined planes more or less decorated: P 7, inclined plane, P 17, slide, P 8. A formerly severe fissure followed by an R 4 reaches a meander presenting two passages: on the right (NW) the normal route, R 4, P 20, crawlway at -157 then a narrow ascending meander giving onto a P 15 which opens into the terminal galleries; on the left (SE), inclined plane and R 5 and P 7. The meander narrows. In the north wall, an unobvious passage behind a block gives access to a very narrow meander for fifteen metres then wider before the junction with the terminal galleries, 10 metres north of the previous branch.

The terminal galleries comprise an active gallery and a “fossil” meander. The first, 35 metres long, is cut at the contact of a layer of silicified limestone into which the stream disappears after a few metres at -176. The meander presents a “T” profile upstream at the contact of the two rocks. Fifteen metres further on, after a narrowing, it opens into two small superimposed decorated chambers and continues beyond by ascending (height of 10-15 m) to an impassable constriction at -157.

At the beginning of the meander, beneath the access P 15, a descent into the incised floor, composed of small narrow steps, allows the stream to be regained at -200 (lowest point of the cave), which flows in an impenetrable meander.

Since we have been working in the Missègre region, we have made some fine first explorations, but this is the one that holds our attention most, both because of the cave itself and because of the promises it raises. Nevertheless, the work is tedious and will be long to progress as much. To conclude, let us say that the Aven de l’Étable is a fine sporting cave that only asks to be visited more often by the speleologists of the Aude.