British Speleological Expedition to the Cantabrian Mountains of Northern Spain, 1965
in conjunction with the "Espeleologos de Penalba", Leon
|British Speleological Expedition 1965 Report|
Situated high on a plateau and taking the surface drainage from several square miles during the wet season, Marques looked the most promising of the Spanish caves so far seen.
The Spanish cavers had told us that after 300 m, the cave suddenly became very tight and they had explored no further.
The entrance, in Devonian limestone, 18 feet wide by 30 feet high, led into a large cavern which suddenly narrowed down to the stream bed as a pebbly crawl, emerging in the side of a larger cross passage. Up to the left was a small hole with a fair draught blowing and to the right several stone pools of 1-4 feet radii. This passage leads into a rift passage up to 40 feet wide and blocked at the lower end by boulders of probably the more shattered and topographically predominant Carboniferous limestone.
A tight squeeze through a triangular slit led to a cross passage junction, one of which was a high (70 feet) rift containing very fine formations. Straight on the passage opened into a chamber 80 feet high, 70 feet long with a crescent side-passage going off, also containing some small formations. The chamber narrowed to the size of the former passage and then dropped below a boulder choke into a crawl. Here several members pushed through a second choke but had to retire on encountering a third approximately 600 m from the entrance.
The system had been extended to over twice its originally explored length and depth. Digging was tried in the final boulder choice but the position seemed almost impossible.