Lithic materials in high fluvial terraces of the rivers Cinca-Alcanandre (N sector of the Ebro Basin)

MONTES RAMÍREZ, L.; DOMINGO MARTÍNEZ, R. ; UTRILLA, P.; RODRÍGUEZ-OCHOA, R.; PEÑA-MONNÉ, J. L.; SAMPIETRO VATTUONE, M. M.

Congreso; XVII Congreso Mundial UISPP; 2014

The findings of Palaeolithic tools linked to Quaternary accumulations in the Ebro Basin are very scarce, with some exceptions such as the Najerilla valley ensembles (La Rioja). Recently, we have localised some materials on the higher fluvial terrace levels from the interfluve Alcanadre ? Cinca ? Noguera Ribagorzana (Level Qt1). Today these reliefs are platforms and isolated hills, around 200 m above the main rivers. They are composed of gravels that come from the Pyrenean and Pre-Pyrenean ranges and show in the top the development of petrocalcic horizons (caliches), that can reach a thickness of up to 2-5 m such as in Saso de las Fitas (Alcanadre river) and in Sierra de San Quílez (Cinca river). The palaeomagnetism and the development degree of the petrocalcic horizons could date these two high terraces in 0,9-1 million years. The prehistoric materials found at those terraces are scarce but significant: in las Fitas we have found some cores and pebbles that have been knapped to simple morphologies, either uni- or bifacial, on quartzite and similar rocks; in San Quílez there are some archaic handaxes and a trihedral piece knapped on flint. As they were on top of both terraces, they must be younger that them, without any further precision. A third quaternary formation between the courses of the Cinca and the Noguera Ribagorzana, Mina de Olriols, shows a different disposition. It is an alluvial fan - terrace deposited by a lateral stream. Its position, altitude and lesser development of petrocalcic horizons could locate it topographically in Middle Pleistocene levels. It could be related to the Cinca river´s terraces Qt5 to Qt6 (178/151 ky to 98 ky respectively). This deposit holds some stratified remains, obtained from a section left by a quarry exploitation: a 0-type cleaver made on black basalt and some scarce bone splinters. The soil study and the analysis of the eolized pieces will help us to precise the chronology of the prehistoric remains from Saso de las Fitas and Sierra de San Quílez. As for Mina de Olriols, we seek to assess the chronology of the geological strata by means of an OSL dating, in order to confirm or discard the relationship between this area and the dated quaternary terraces.