Zubiburua Cave:
The Zubiburua cave system (also called Isuntza I-II), is an endokarstic phenomenon that is found in the municipality of Lekeitio, near the Isuntza bridge. It is a cavity with a total development of 308 meters, with a maximum unevenness of 9.22 meters. Its mouth was altered by the construction of an old police barracks (later used as a Civil Guard barracks), and was hidden by it until its demolition at the end of the last century. Currently, the entrance is closed by a gate with a door, since its interior safeguards an electrical installation for lighting the nearby public road.
Despite being on a vadose floor level, some parts of them are periodically flooded by seepage waters. At the genetic level, the cave would be part of the multilevel system of the karst of Mount Lumentza, and forming a vadose floor of it. Below Isuntza, the complex of the Armintxe-Atea-Zubieta caves would develop (formed in at least 3 different levels), which have undergone major modifications due to the urban processes that have taken place in the municipality. Above, there would be 3 levels that would make up the paleontological site of Garratxa III, discovered in 2015 by the speleology group ADES, and the decorated cave of Lumentza (popularly known as Garratxa).
At the expense of a more in-depth geological study of it, it would be a cave in which the traces of phreatic dissolution are mostly visible. However, lithochemical formations abound in the forms of beautiful stalagmites, flows, and stalactites of all kinds (fistulous, eccentric, etc.), as well as specific phenomena of clastic dissolution (accumulations of large blocks, etc.). Despite being surrounded by archaeological and paleontological sites, no signs of prehistoric frequentation have been discovered in the cave. We can only highlight the existence of two eroded streams located in sectors far from the entrance, covered with claws of the cave bear. This could be due to the fact that this cave was closed in prehistoric times, and that it was discovered when the building that housed the police headquarters was built.
The cave has been monitored, between 2015 and 2019, by the Department of Zoology and Biology of the UPV / EHU and the speleological group ADES. This action was aimed at counting the bats that the cavity houses, through in situ recognition and counting using echolocation techniques. Between 2017 and 2018, a specific archaeological experiment was carried out framed in the doctoral thesis of María Ángeles Medina-Alcaide, from the Department of Geography, Prehistory and Archeology of the UPV / EHU. This action was carried out independently of the aforementioned actions of the cave fauna study group.
Agreement between the City Council of Lekeitio and the International Institute for Prehistoric Research of Cantabria:
In September 2021, an agreement was signed between the Lekeitio City Council and the IIIPC to:
• Establish a regime for access to the cave, as well as a calendar, to avoid damage to its ecosystem. The cave will remain closed in the period from October to March.
• Monitor the environmental parameters of the cave (temperature and relative humidity, as well as CO2).
• Carry out a geomorphological documentation of the cave, documenting its formation phases (sedimentation / erosion) of geological and anthropic origin.
• Carry out a cleaning of the cavern, removing the residues accumulated in it for years (charred organic residues, plastics, etc.).
• Proceed to the design of an experimental program, in areas previously monitored and exhaustively documented photographically (both before, during and after the procedure). The objectives of these processes will be the following.
o Know the prehistoric lighting systems. An artificial fireproof pavement will be used to collect the waste generated (this will allow us to know the amount of waste generated in these activities, allowing it to be compared with the known archaeological record). Those areas with good ventilation will be selected based on the results of the monitoring process. Likewise, the gases emitted (CO2, CO, etc.) will be measured, ending the experimental program at the moment in which a potentially dangerous environment for fauna and scientists working in it begins to be generated. In any case, the use of the Isuntza cave would be limited to small fire processes whose affectation would be barely perceptible (e.g. grease lamps, small hearths, small torches).
o Know the processes of the operative chain of Palaeolithic graphic activity (painting, engraving, sculpture, etc.). For the execution of the graphic activity, little significant canvases will be previously selected, to reduce the landscape impact on the cavity. In addition to this, exhaustive photographic documentation of them will be carried out, both prior to the experimental process, and during and after it. An artificial pavement will be placed for the collection of subsequent waste (this will allow knowing the amount of waste generated in these activities, allowing it to be compared with the known archaeological record). The activity will be limited to the meticulous execution on a micro scale of the graphic activity execution processes, in addition, it will try to recover the used supports after the activity, cleaning the used canvases with aseptic distilled water, as well as covering with small sediments clayey furrows generated.
• Design a dissemination program both at the teaching level (aimed at undergraduate, master or doctorate students from different universities) as well as general dissemination (aimed at the inhabitants of the municipality, as well as different interested visitors). This would make it possible to show a natural cavity unknown to the general visitor, while observing in situ the procedures of an archaeological experiment. The knowledge generated will allow us to delve into the knowledge of the first human populations that inhabited the Lea-Artibai region, and that left us the impressive art samples that are preserved in some of its cavities (Atxurra, Armintxe, Lumentxa, etc.) .
Gas extractor installed to evacuate the waste generated and avoid affecting the cave