Reconstructing climate and soil formation processes in the Atxoste rock-shelter (Upper Ebro Valley, Northern Spain): A preliminary geoarchaeological view of human communities during the Pleistocene-Holocene transition in the Ebro Valley and Cantabrian Spain

Abstract

Natural, anthropic and post-depositional formation processes can affect the formation of sediments in rock shelters. Geoarchaeological analyses were carried out on a series of samples of compact and loose sediments provenient from the 1995 to 2005 excavation campaigns at the Atxoste shelter. This work focuses on climate reconstruction of the Upper Ebro Valley, comparing it with results of previous studies of the area and its surroundings, as well as the Cantabrian region. We also point out the problem of sediment conservation when analyzing sites containing Pleistocene/Holocene and/or Mesolithic/Neolithic transition stratigraphies. Thanks to the geoarchaeological study we have differentiated three climatic events: - The end of the Pleistocene as a period characterized by cold, humid conditions and with probable seasonal droughts. - The Pleistocene-Holocene transition that corresponds to a climatic moment in which the indicators of cold climate have practically disappeared. - The beginning of the Holocene, when a significant and rapid climatic improvement takes place, with an increase in temperatures, a decrease in rainfall but maintaining the humidity. The identification of the different post-depositional processes has been key to identifying the state of the recovered archaeological material. Therefore, this study is based on the geoarchaeological analysis, approaching the period central to this paper (Pleistocene-Holocene transition). This is crucial in order to obtain a better understanding of the paleoecology and archaeological aspects.