Geocronología de los yacimientos achelenses de Pinedo y Cien Fanegas (Valle del Tajo) e implicaciones en la evolución fluvial en el entorno de Toledo (España)

This study presents the first geochronological data from several research projects focused on the chronostratigraphy of the Tagus fluvial terraces in the environs of Toledo city (Central Spain). The research is centered on Middle to Late Pleistocene fluvial terraces with palaeontological and Acheulean sites of similar Palaeolithic technology than those showed by the lithic assemblage of the Pinedo site (Máximo Martín Aguado Collection). This study includes the first IRSL and AAR datings for the fluvial levels at +25−30 m present in the Acheulean sites of Pinedo (Toledo) and Cien Fanegas (Aranjuez). The obtained ISRL dates (>280 ky and 292±17 ky) indicate that these fluvial levels and hence their associated Palaeolithic sites, were formed during the marine isotopic stages MIS 9 and MIS 8, and thus it is possible to correlate them with the Arganda II Unit of the adjacent Jarama valley. However, data from Pinedo suggest that this Acheulean site probably also correspond to the upper Arganda I Unit of the Jarama valley (MIS 11–MIS 9). Although the AAR date (226±37 ky) obtained for the Upper unit of Pinedo has to be carefully considered (due to the scarce stratigraphic data and the low dentine levels found in the Equus sp. analyzed samples), it could indicate that sedimentation of the studied terrace level reached the MIS 7, as may also occur in the Jarama valley (Valdocarros site). In the analyzed sector of the Tagus valley, continuous fluvial sedimentation was favored by the occurrence of Neogene evaporites karst-linked subsidence (upstream) and the presence of an outstanding internal base-level represented by the bedrock incised meander of Toledo (downstream). The dating method used in this study (post-IR- IRSL) has allowed us to obtain the oldest date from fluvial sandy deposits in the Tagus fluvial basin up to the present time.