Artzainzulo Ref. FC-7

The entrance has proportions of 2 metres high x 15 metres wide and gives way to a gallery of large proportions, 10 x 15 metres and with an approximate length of about 150 metres. The first 10 metres of the cavity consist of topsoil and animal excrement, all of which forms a small ramp; the rest of the gallery has a great inclination, with a great profusion of clastic forms due to decalcification given the traces of chemical corrosion of the blocks. The final 10 metres before the active zone begins have a horizontal floor completely paved by stalagmitic flows. At the end of this gallery there is another one about 10 metres long x 2 metres wide, descending, with a paved floor and corrosion concretions. To its right a new gallery ascends, 1.5 metres wide by one high, with a floor rounded by clays that ascend to a platform where the sediments can be seen in stratigraphic layers, to descend again through a gallery of 2 x 1.7 m and a floor, like the previous one, sedimented with clays. After a 2 m drop one reaches a chamber of 3 x 1 m, with corrosion concretions and a floor paved with stalagmitic flows. The ascending gallery on the left has a strong ascending inclination, sedimented with compact clays like the rest of the cavity, with very exposed rudists; after ascending 25 metres one reaches a platform with a floor of identical characteristics, to descend 12 metres and become blocked with clays. The second descending gallery, with a floor of stalagmitic flows, continues to a chamber with clay sediments and a lake 3 metres long. The fossil gallery on the right is 3 m wide and leads to an ascending gallery with a clay floor up to a kind of platform, to descend with the same floor characteristics. The chamber located before the drop is blocked by blocks and cardos that descend in a ramp to a 12-metre drop to a platform of wedged blocks and then another 8 m drop to the sump.

Lithochemical intakes abound, concentrated in parietal crusts and stalagmitic flows (very marly limestones), with accumulation of clay. In the area of the final 10 metres before the active zone a water deposit and a slight circulation of the same towards the interior of the cavity can be seen; its characteristics are the consequence of a chemoclastic process with lithochemical formations that, together with the decalcification clays, obstruct the passages between blocks causing damming of the water in some places. In the river, which runs along a sedimented floor, there are forms of concretions; it may be that these concretions and sediments of the bed are due to earlier periods of stagnation of the water and, therefore, to its damming, which would lead to the deposit of materials on its bottom and to concretions on the walls due to the rises or falls of the stagnant water at rest, these concretions being part of a lacustrine process.

This is a cave with a water level that may be permanent, with a height difference of 65 metres and a development of galleries of about 450 metres; being close to the spring, it is necessary to be careful in times of flooding in specific stretches of the meander. In the initial gallery there was a small water channel, especially flowing over the flows, and a strong dripping about 50 metres from the entrance. In the active zone the water flow descends through a very narrow vertical lenticular gallery. On reaching the river again, a flow of approximately 2-3 l/s runs through it. Following the river bed one reaches a sump, and in the chamber before the drop a new ascending gallery reaches, after a distance of 10 metres, a river with a flow of 2.5 l/s that sinks through a fissure towards the sump, this contribution being large; the river will at some point become a sump. In the sump it can be seen that a small flow of water comes from the bottom.

Following the active cavity one reaches a point where its route is impassable; from here one ascends through a gallery on the left to meet two others, one ascending on the left and another descending on the right. Through the second descending gallery one continues to a chamber with clay sediments and a lake 3 metres long; past this lake one reaches, following the river bed that reappears, a fork, and continuing through the gallery that carries the water flow one reaches a sump. Descending through the fossil gallery on the right, 3 m wide, one reaches an ascending gallery with a clay floor up to a kind of platform, to descend with the same floor characteristics; through this gallery one reaches a 4 m drop and shortly afterwards another of 5 metres, opening into a new chamber. Descending through the second of these, an excavation front can be seen in the joint towards the sump area.