Koskobilo, a world lost in Burunda

Asier Gómez Olivencia, Joseba Rios-Garaizar, Mikel Arlegi

The Burunda valley is part of the Sakana corridor, a natural pass that connects the Alava plain with Pamplona / Iruña and is delimited by the end of the Massif de Aizkorri and Sierra de Aralar to the north, and by Urbasa-Andia to the south. In fact, the Roman road that ran from Asturica Augusta (Astorga) to Burdigala (Bordeaux), passing through Iruña-Veleia and Pompaelo (Pamplona-Iruña), among other towns, used this natural route. In this environment, the exploitation of the Albian limestone of the Koskobilo hill (Olazti, Navarra) during the 20th century uncovered the oldest quaternary deposit in Navarra.

In 1940 the quarry work uncovered a vertical chasm in Koskobilo. Among the sediments of that chasm, various fossil remains appeared and the foreman of the quarry sent a large canine to Máximo Ruiz de Gaona . In addition to being a teacher and micropaleontologist, Máximo Ruiz de Gaona was a multifaceted naturalist, and contributed to the fields of vertebrate paleontology and archeology. This find interested him a lot and, as he himself relates, in addition to recovering fossils from the sediments of said chasm, already almost completely destroyed, he recovered many others in the two slag heaps located on the slopes of Koskobilo ( Figure 1 ) . Ruiz de Gaona sent these fossils to Federico Gómez Llueca, paleontologist at the Museum of Natural Sciences (Madrid) for their classification, providing a list of at least 26 species of vertebrates, among which the first beaver remains discovered in the Iberian Peninsula stood out. , as well as the presence of rhinoceros and hippopotamus remains.

Ten years later, in April 1950, with the intention of recovering more fossils, Ruiz de Gaona returned to visit the quarry dumps, but his main find was an important set of flint lithic industry of more than 5,000 pieces. His study indicated the presence of pieces from different Paleolithic times, among which the Solutrean industries stood out, and also suggested that the flint came from nearby outcrops in the Sierra de Urbasa, about 5 km from Koskobilo. This find interested the prestigious prehistorian J.M. de Barandiarán, which in 1955 recovered from the dumps a small set of paleontological remains and 1,146 remains of lithic industry ( Figure 2 ). These last remains were studied by María Amor Beguiristáin in 1974, who indicated the paleolithic aspect of this group with various cultures represented. During the 70s, Ruiz de Gaona also published unpublished material from Koskobilo from his private collection and of undoubted Palaeolithic origin, including five clearly Solutrean leaf tips, as well as three bifaces whose typology would indicate an industry prior to the Upper Paleolithic. Ruiz de Gaona's interest in understanding the origin of these lithic pieces leads him to speak with the quarry staff, and based on these testimonies, he tries to “imaginatively rebuild” the destroyed site: a cavern approximately 40 m long. horizontal and not very wide. Based on the fragmentation of the bones, Ruiz de Gaona relates the site from which he personally extracted remains in 1940 with the cavern, where humans left their remains of lithic industry, which he would discover 10 years later. The humans would use the cavern, fracture the bones of the animals to extract the marrow and throw them down the chasm, which would be located near the mouth of the cave. Despite a certain historiographical debate, the vision of this “site” was set by Barandiarán and Vallespí in 1984 who highlighted the presence of three cultures s: Mousterian of Acheulean Tradition (MTA), Perigordian (currently called Gravettian) and Solutrean. Later in the 90s, Jesús García Gazólaz attributes a series of four bifaces from Koskobilo to the end of the Acheulean period, in what is currently considered Middle Ancient Paleolithic and chronologically located at the end of the Middle Pleistocene (300-100 thousand years before the present) .

For 15 years one of our lines of research has been related to the study of the oldest human occupations in the Western Pyrenees, as well as their paleoecological conditions, excavating sites such as Arlanpe (Lemoa, Bizkaia) and reviewing various paleontological collections such as that of Punta Lucero (Zierbena, Bizkaia). Paleontological studies indicate that hippos disappeared from Western Europe after the last interglacial, about 117,000 years ago. For this reason, the presence of this species in Koskobilo was especially interesting because it could indicate that we were (at least in part) facing a Middle Pleistocene site. Therefore, with this working hypothesis in mind, we decided to re-study the collections that were conserved from this site, since it had been destroyed by the quarry. We established three complementary lines of work: the review of the paleontological collection, the prospecting of the environment of the site and its dumps, and the study of the existing bibliography up to that moment.

In 2016 we conducted several surveys in the area of ​​the old quarry where we recovered new evidence of lithic industry, but also some bone remains. The review of the publications on the lithic industry and the study of the remains recovered in these last surveys indicated that there were several chronologies represented in the Koskobilo collection deposited in the Museum of Navarra. Likewise, the preliminary study of the paleontological collection also indicated the presence of fauna from the Middle Pleistocene (the presence of the macaque and the Tibetan bear, which we will talk about later) and the Upper Pleistocene (such as the cave bear; Figure 3 ). In addition to knowing the species that were represented by the fossil remains, we were also interested in the process by which these remains had accumulated in the deposits: were they, as proposed by Ruiz de Gaona, the result of human activities? The study of the bone surfaces indicated that there were two large groups. On the one hand, the small paleontological collection recovered by Barandiarán in 1955, together with the remains that we had recovered in 2016, consisted for the most part of unidentifiable fragments of the diaphysis of long bones, and presented cut marks and anthropic manipulation. On the other hand, the paleontological collection recovered by Ruiz de Gaona in 1941 was composed mainly of fossil remains that could be classified taxonomically, did not present (with one exception) cut marks, and presented evidence of having been altered by carnivore activity. With the evidence available to us, we proposed that in fact in Koskobilo archaeo-paleontological remains had been recovered from at least two different sites that could belong (or not) to the same gallery system. On the one hand there would be the chasm discovered in 1940, from which Ruiz de Gaona recovered most of the paleontological collection, whose fossils represent different moments of the Middle and Upper Pleistocene, and in whose accumulation carnivores had participated. On the other hand, most of the lithic remains from the Upper Paleolithic, which were thrown into the dump at some indeterminate time between 1940 and their discovery in 1950, as well as most of the fauna remains with cut marks would surely correspond to a second deposit, which was completely destroyed by the work of the quarry and whose remains were recovered directly from the dumps.

Note that the cave bear molar, in addition to being larger, in line with its larger body size, also has a more complicated cusp pattern. Asiatic black bear remains have been attributed to the Middle Pleistocene while cave bear remains have been attributed to the Upper Pleistocene. Drawings made by Amaia Torres Piñeiro.

For detailed work on the fauna remains we have a large group of researchers: paleontologists from different specialties, geologists and archaeologists, with the intention of getting the maximum amount of information from the collection. The results were worth it. Interestingly, the supposed hippo remains that had initially aroused our interest in the site turned out to be the remains of a large wild boar canine (tusk). On the other hand, we were able to date a speleothem that covered a tooth of the rhinoceros species Stephanorhinus hemitoechus which provided a minimum age of 220 thousand years for this tooth ( Figure 4 ) and therefore extension for part of the paleontological collection. This collection consisted of 38 mammalian taxa, from rhinos to bats (including 4 species of bear), 6 bird taxa, including one species that no longer inhabits the Iberian Peninsula (the black grouse, Lyrurus tetrix ), and three fish vertebrae ( Figure 5 ). The detailed study confirmed our preliminary results: the existence among the remains recovered in 1940 of fossils from both the Upper Pleistocene and the Middle Pleistocene, although in many cases, due to the fact that certain species had broad chronologies, it was not possible to ascribe these remains to any of the those periods. Among the fossil remains, the remains of two of the bear species stood out: the ancestor of the cave bears (Deninger's bear Ursus cf. deningeri ) and the Asiatic black bear (or Tibetan bear, Ursus thibetanus ; Figure 3 ). It is also worth noting the presence of remains of other species, of cuon ( Cuon cf. priscus ), of Barbary macaque ( Macaca sylvanus ; Figure 6 ) and giant deer that we attribute to the genus Megaceroides . Based on the biochronological data available to us, these species could have been contemporaneous with the rhinoceros remains dated to the Middle Pleistocene (in MIS 7d or earlier), providing data from chronologies that are very little represented in the fossil record of the western Pyrenees. The importance of the study of these species for the study of human evolution is their contemporaneity with the last pre-Neanderthals, which helps us to better understand the ecosystem in which these hominins inhabited and exploited. These fossil remains probably accumulated in an interglacial moment, similar to the current one, in which the faunas were very diverse, and where horses, deer, bison, giant deer and rhinos were hunted by lions, leopards, cuones, wolves and hyenas. Likewise, on the banks of the Arakil, overflowed by beaver dams, two species of bears would come down to drink water, and groups of macaques could be seen on the limestone slopes of Koskobilo. The deposits (or levels) of these chronologies are very scarce in the western Pyrenees, among which we can basically cite the lower levels of Arlanpe (Dima, Bizkaia), the lower levels of the Lezetxiki I and Lezetxiki II deposits (Arrasate, Gipuzkoa) , and the remains of Deninger's lion and bear from Santa Isabel de Ranero (Karrantza, Bizkaia).

80 years ago Ruiz de Gaona saved from its destruction an important paleontological collection of what was the oldest quaternary site in Navarra, Koskobilo. Currently the quarry that destroyed the sites is abandoned, but new archaeological work in the area promoted by the Aranzadi Science Society and directed by Daniel Ruiz González will provide more information on Prehistory in Burunda.

For learn more:

Arlegi, M., Rios-Garaizar, J., Rodríguez-Hidalgo, A., López-Horgue, MA, Gómez-Olivencia, A. 2018. Koskobilo (Olazti, Nafarroa): new findings and review of the collections. Munibe Antropologia-Arkeologia 6 9, 21-41 . doi: 10.21630 / maa.2018.69.07

Arlegi, M., Rios-Garaizar, J., Rodríguez-Hidalgo, A., Gómez-Olivencia, A. 2018. New data on the collection archaeo-paleontology of Koskobilo. In: Badiola, A., Gómez-Olivencia, A., Pereda Suberbiola, X. (Editors). Fossil record of the western Pyrenees. Assets of paleontological and geological interest. Social projection. Vitoria-Gasteiz, Central Publications Service of the Basque Government-Eusko Jaurlaritzaren Argitalpen Zerbitzu Nagusia, pp. 209-212. ISBN: 978-84-457-3437-7

Astibia, H., Murelaga, X., Pereda-Suberbiola, X., 1996. Máximo Ruiz de Gaona as a vertebrate prehistorian and paleontologist. Prince of Viana. Science Supplement XVI- Num 14/15 65-76.

Barandiarán, I., Vallespí, E., 1984. Prehistory of Navarra, Navarra Archeology Works. Government of Navarra, Pamplona.

Gómez-Olivencia, A., Arlegi, M., Arceredillo, D., Delson, E., Sanchis, A., Núñez-Lahuerta, C., Fernández-García, M., Villalba de Alvarado, M., Galán, J., Pablos, A., Rodríguez-Hidalgo, A., López-Horgue, MA, Rodríguez-Almagro, M ., Martínez-Pillado, V., Rios-Garaizar, J., van der Made, J. The Koskobilo (Olazti, Navarre, Northern Iberian Peninsula) paleontological collection: new insights for the Middle and Late Pleistocene in Western Pyrenees. Quaternary International . doi: 10.1016 / j.quaint.2020.06.005

Ruiz de Gaona, M., 1941. A site of Pleistocene mammals in Olazagutía (Navarra). Bulletin of the Royal Spanish Society of Natural History 39, 155-160

Príncipe de Viana. Science Supplement Year 1996, Number 14-15. Dedicated to: Tribute to Máximo Ruiz de Gaona: Naturalist and Paleontologist (1902-1971)

About the authors: Asier Gómez Olivencia ( @AsierGOlivencia ) is a Ramón y Cajal researcher at the Geology Department of the UPV / EHU Faculty of Science and Technology and an active member of the Prehistory Department of the Aranzadi Science Society. Joseba Rios-Garaizar ( @jorios ) is a researcher and manager of lithic collections at the National Center for Research on Human Evolution (CENIEH). Mikel Arlegi ( @ArlegiMikel ) is a postdoctoral researcher at the UPV / EHU and the Université de Bordeaux.

The article Koskobilo, a lost world in Burunda has been written in Cuaderno de Cultura Científica .

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