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The destroyed site(s) of Koskobilo (Olazti, Navarre, Northern Iberian Peninsula) have yielded unique archaeo-paleontological evidence in the Western Pyrenees region. The quarry uncovered a karstic site with faunal remains in 1940, and fossils were recovered both in situ and from the quarry dump. Ten years later, while the quarry was still working, a new visit to the dump yielded a large lithic assemblage and additional fossil remains with a different taphonomic pattern, which has been interpreted as the remains coming from a different site or zone within the same karst system. Here we re-study the paleontological evidence and provide new dating on a speleothem covering a Stephanorhinus hemitoechus tooth, which has yielded a minimum date of c. 220 ka for part of the assemblage. In total, the fossil assemblage comprises 38 mammal and six avian taxa and three fish remains. The faunal evidence indicates that in 1940 a mix of taxa from both the Middle and Upper Pleistocene were recovered, and it is difficult to assign most of them to a concrete period. However, based on biochronological criteria some of the identified taxa (e.g., Ursus thibetanus, Ursus cf. deningeri, Cuon cf. priscus, Macaca sylvanus, cf. Megaceroides) could be roughly contemporaneous with the dated rhino tooth, which would provide a new window to the Middle Pleistocene of the region, with deposits from MIS 7d and/or older. Despite the difficulties in studying this collection, recovered without stratigraphic context and in a salvage operation, Koskobilo has yielded an important paleontological assemblage which helps to understand the paleoecology of the Middle Pleistocene human occupations in the Western Pyrenees.

The archaeopaleontological collection from Koskobilo is composed of hundreds of fossil and thousands of lithic remains, mostly recovered during the middle part of the 20th century. Here we present the complete paleontological study of the collection, which includes 36 mammal taxa, 6 avian taxa and a small fish vertebral collection. Additionally we have performed direct dating of a speleothem crust covering one of the rhinoceros teeth, which provides a minimum of 219 ka for part of the collection, the rest being from the Upper Pleistocene, mixed with some Holocene/recent elements. The paleontological collection from Koskobilo is one of the most important in the Western Pyrenees due to the scarcity of the local Middle Pleistocene fossil record and the rarity of some of the taxa represented, such as Ursus thibetanus, Macaca sylvanus and cf. Megaceroides.

© 2014 Elsevier Ltd and INQUA. The western Pyrenean area contains extensive karst areas, however, their genesis and development are still mostly unknown. In this work, we make a general description of the karst landscape in different karst areas: 1) Rasa type; 2) Cone-type karst; and 3) Alpine-type karst. The first two types are present in the littoral area, where geomorphological evolution mostly depends on sea level and climatic changes. We focused our study in two karst areas of the littoral cone-type karst. We correlate different caves created from different stable water table levels. Three representative caves are studied in detail, studying their stratigraphic record based on allostratigraphy. Finally we dated the different phases of speleothem formation in the three caves. Using all this information, we defined four stable paleowater table levels, at 50, 150, 220 and 350masl, controlled by sea level changes and isostatic uplift events. The lowest level is the youngest, with an age of c. 1Ma. We discovered that the interior of the three caves display very similar endokarst allostratigraphic sequences, characterized firstly by an erosion phase, a fluvio-karst input, flowstone speleothem formation and finally dripping speleothem formation. The chronological data shows a correlation between these phases and Pleistocene climatic phases; the erosion phase is related to the falling sea level, fluviokarst detrital input is related to cold (glacial) stages and the formation of speleothems is related to the warmest (interglacial) moments and high sea level periods.