Cobble selection in the Quaternary terraces of the Segre river: the case of black quartzites and n12 archaeological unit of Roca dels Bous (Eastern Pre-pyrenees, Iberia) - Roy Sunyer, Miquel; Roda Gilabert, Xavier; Plasencia Figueroa, Francisco Javier; Benito-Calvo, Alfonso; Mora Torcal, Rafael (2014)