OUCC Proceedings 6 (1974)
El Cuevon de la Pruneda (Cueva de Puron)
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Grid Ref. 5181 975
This cave was surveyed to Grade 3a and described to the then limit of exploration in the report of the 1970 expedition. The opinion expressed in that article, that a through trip would be improbable, proved to be unduly pessimistic, despite the logical premise upon which it was based.
The remainder of the cave was penetrated on July 20th, one party having entered by the sink as before, and the second entering by the resurgence; a through trip was made in each direction. The downstream party surveyed back to pitch 2 from the resurgence on their way out. Indeed the 1970 party had been almost within sight of daylight when they halted above the third pitch for want of tackle. The length of newly surveyed passage was 235 metres, giving a total surveyed length of 611 metres for the whole cave.
Briefly, the upper part of the cave begins with two penetrable entrances, normal and flood sinks, which lead to a large and boulder strewn passage. After narrowing at one point, the streamway develops into a series of cascades and pools. The first pitch is made up of two of these cascades, descending at a steep angle. The second pitch drops into another deep pool, the exit from which is a tall, narrow rift. This leads to a larger passage with water up to 1.5 metres deep in one long shelving pool, followed by a series of short cascades. The subsequent stream passage contains water filled potholes from 1 - 2 metres deep in the floor. Two large chambers, the first with a sandy floor, and the second with boulders, carry the stream to a small passage, blocked by substantial boulders. A large flood bypass, with several deep potholes, gives access to the third pitch, where the stream reappears. This pitch is in effect a scalloped slope, set at 300 to the vertical; a ladder as a handline is all the tackle required. A traverse from the top of pitch 3 leads to an extensive passage, which was not surveyed but which has an estimated length of 200 metres. This contains a number of small chambers at various levels. Because the passage is dry and muddy, the few decorations in this part of the cave are not particularly impressive. The route from the bottom of pitch 3 to the resurgence is wide, but liberally bestrewn with boulders and occasionally low roofed. The stream emerges into a small wooded valley from a cave mouth 5 metres wide and 2.5 high.
Puron provides a very enjoyable through trip, particularly the sections in the streamway. It is in fact possible to make the trip from sink to resurgence without tackle: all the pitches are free climbable, to anyone who interprets that in a liberal fashion.
(Speleogroup exploration in the 1980s showed this cave to have multiple abandoned resurgence exits).