MATIENZO CAVES PROJECT
Matienzo '86 - Connections
Cave exploration around Matienzo during 1986
amended from an original article by Juan Corrin in Caves & Caving 35
The hills surrounding the Spanish Village of Matienzo are of Cretaceous limestone. Flowing across the impermeable floor of the basin is a river which comes out of the limestone at the southern end and disappears back into the ground at the northern side. The depressions two longest caves are just where you would expect to find them, behind the resurgence and beyond the sink. These two caves have not always been known - it was in the early 70s that serious pushing and exploration was started and it was only in August 1986 that the Carcavueso sink system was really opened up.
The 1986 British Expedition built on the effort of previous groups and succeeded in increasing our underground knowledge of the region. Some 7km of new passage was discovered and we connected together four caves to produce a system which is now Spains 4th longest.
But first the cave complex at the southern end which has kept cavers occupied for
years, both in the cave and above it. The top entrance to the South Vega System
(Azpilicueta - site 333) lies 300m above the Vega arm of the depression and the trek can
be tedious when carrying rope to tackle up the cave. Virtually all of the holes at high
level appear to have a phreatic origin - Azpilicueta is an exception. it is a relatively
young vadose cave which is a series of pitches separated by narrow and sometimes
meandering canyons. There is a short, stream-excavated bedding section at a depth of 140m
with a few formations. Downstream leads to the caves finest feature - a 100m pitch
broken by a couple of ledges. The bottom of the big pitch marks the end of the vertical
section of Azpilicueta. From the bouldery chamber a number of passages radiate. The
Reñada, valley entrance lies to the north, but major passage goes off to the east and to
the west - where it is heading towards another major system (and hopefully a connection).
Spanish cavers have been exploring this system at Alisas and they have reached a depth of
about 300m and a length of approximately 3km. This year, Giga Hall beyond sump 1 was
entered via Azpilicueta and the second sump bypassed by burrowing through a choke.
Disappointingly, only half a kilometre of passage was entered with another sump barring
further progress towards Alisas.
Seventeen years is quite a time to have a caving area laid aside by Spanish authorities for almost purely British exploration. The situation certainly wouldnt happen in Britain - theres no way Ingleborough would be left for the Spaniards to explore. It might be thought that this length of time would have been enough to finish off the area but every year something appears which firmly puts down that idea. New cave passage and entrances are often found right next to known caves. Two hundred yards from Uzueka (site 107) is another entrance in trees which was missed until this year. The 3m wide, 5m high gaping aperture was discovered from inside Uzueka. So we now have another entrance - this one cuts out the tight squeeze before Quadraphenia but has its own disadvantages involving a spot of crawling and a hands-and-knees section through half metre deep mud.
As well as underground work, exploration above ground has also been carried out. The first problem to be overcome in "shaft bashing is finding and getting to them when the ground is covered with a mixture of brambles, creepers, trees and gorse. A timely fire just before the caving season clears the area and makes finding the caves quite straightforward. One such area, within sight of the camp and two hundred metres above Carcavueso, held half a dozen holes, one going to a tight depth of fifty metres. Another surface search to fill in blanks in the three dimensional mazes that surround the depression involved Torca de Mostajo (site 71), another complicated cave which quite probably is going to "go big In the future. The cave heads north along the western side of the depression. To the west and north of the cave ties territory that is incompletely trodden. The depression of Cobadal is apparently floored with sandstone that drains water towards Mostajo and Matienzo with very strongly draughting holes. This years expedition saw the opening up of a couple of these but they all, disappointingly, closed down. There will be more visits to this area in the future.
And so to the main story of the 1986 expedition - the connections in the Four Valleys
System. When Lank Mills first visited the area in 1969, the only speleological hints for a
world class cave was a river sinking at Carcavuezo, a river resurging at Secadura, 3km to
the north-east - and lots of horizontally bedded limestone in between. The straightforward
objective was to enter Carcavuezo and emerge at Secadura - the reality has been much more
complicated and has taken 17 years to explore at least some of the possible connections.
As often happens in caving, new faces can bring a fresh approach and enthusiasm to
looking at old caves. Carcavuezo was the place where the unexpected was uncovered. The
river at Matienzo sinks, a short distance from the campsite, into an impenetrable mess of
boulders. After heavy rain the small holes cannot drain the swollen river and so, to try
to cope with the flooding problem the locals have dug a large trench which carries the
overflow a couple of hundred metres to another sink. This is a heap of decaying logs but
on the bank to one side a small hole can be excavated of its annual debris deposits to
eventually lead down, through draughting passage, to the underground river. Carcavueso was
first dug out and entered in the early 1970's, and it takes little imagination to
visualise these slimy-walled passages, with rubbish squashed into roof cracks, full of
flood water. Andy Hall, Jim Davis and Simon Chandler on a scouting trip into the cave came
across a small drop down on the right of the river which led to a tortuous and flood-prone
route between boulders. They popped up into a roomy passage which was still open and going
when they emerged a few hours later with the good news. The next day a large team was
assembled and split into three groups to push and survey the most obvious routes. The link
through to Cueva Llueva was discovered and more open routes were noted.
There is no doubt that the 1986 expedition has provided a climax in a series of parallel caving explorations carried out over the last 17 years. The 32km long Four Valleys System is now an almost integrated complex of caves where it is possible to travel underground through to 3 of the depressions. The Llueva-Secadura connection to the resurgence has yet to be opened up.
These contain area maps and references to the dozens of other articles published.