RECENT ADVANCES IN GEOCHRONOLOGY AND GEOARCHAEOLOGY AT THE ATAPUERCA KARST SYSTEM

Caves act as sediment traps in that the influx of material tends to stay there preserving the record of the depositional and environmental processes. Therefore, cave deposits provide excellent locations for the study of human activity in the past. That is the case in the so called Atapuerca karst system, developed in Cretaceous limestones in the northern Iberian Plateau, Spain. For over thirty five years the archaeological sites in the Atapuerca karst have yielded a vast amount of fossils, including human, and lithic tools in sediments that span almost a million and a half years. The site, added to UNESCO's World Heritage List in 2000, has become a key Eurasian paleoanthropologic and paleontologic locality as it holds the oldest human fossils and lithic tools and therefore is key to understand the earliest hominid expansions out of Africa. A variety of geoarchaeological approaches have been used to decipher the significance of the sedimentary record and the karst system evolution, and their interaction with human activity during the Pleistocene. Dating the cave deposits is crucial and is based on magnetic reversal stratigraphy in combination with absolute dating techniques including Uranium-series, Electron Spin Resonance on fossil teeth and quartz grains, thermoluminescence, and cosmogenic burial dating. Specifically paleomagnetism and rock magnetism have been used as the first line of defense in establishing the temporal framework of the sedimentary infill. Both sediments and flowstones are generally excellent recorders of the geomagnetic polarity of the past and therefore have been used to establish the main reversals in the Pleistocene such as the Matuyama-Brunhes boundary and to detect the presence of Subchrons such as Jaramillo. Because the discussion of early hominin dispersals into Europe is centered on the timing these events occurred, obtaining precise chronologies for the cave deposits is of paramount importance. On the other hand, methods such as the Anisotropy of Magnetic Susceptibility are extremely powerful to interpret the depositional history of sediments and paleoflow directions in sediments. This talk will discuss recent paleomagnetic and rockmagnetic results and their implication on the Atapuerca karst system evolution and on the early Pleistocene settlements in Eurasia.