The study of the detrital sediments in the Ebro river terraces near Zaragoza has demonstrated that in this area karst is not only an active phenomenon at present but also during the Pleistocene. The Ebro River system had mainly braided features related to a general high water availability and was affected by the development ofdolines. The ana/ys/s ofdolines filling shows synsedimentary deformation linked to dissolution processes but probably also to tectonics. The preliminary mineralógica! study reveals the existence of some differences depending on the terrace age and also its own potential in palaeoenvironmental and source area studies