The significance of aeolian sand accumulations located in the Mangabril area (middle Guadiana river valley, Spain) is discussed on the basis of morph-sedimentary data, optically stimulated luminescence (OSL) dating, and archaeological record. Mengabril sands are composed mainly of sand-sized particles (80,32%), however, due to Its high content of silt (12,18%) and clay (7,5%) can consider them as so-called clay-dunes (or maybe we should talk rather of "silt-dunes"?). This kind of mixed dune have been described elsewhere in the Iberian Peninsula (mainly in La Mancha), but while there have been dated before the mid-Holocene, the dates obtained by OSL and the archaeological record in Mengabril place them specifically during the arid periods located in the Chalcolithic, Roman times until Antonine dynasty and from early to high Middle Age.