Silt-sized sediments and gypsum on surface formations in the Ebro valley. A disambiguation of the term gypsiferous silts

Since the 60’s, many authors have reported presence of common silt-sized materials in Ebro valley, on surface formations and positions that given rise to several interpretations, sometimes contradictory. According references, three main terms are used (gypsiferous silts, loess flour-like gypsum) applied silts fine sands with gypsum accumulations. The two first carbonate contents up 40-50%, coarse silty sandy textures, located different positions. Loess normally appears as thick outcrops slopes leeward from wind direction, a limited pedogenesis consisting partial mobilisation between 0 30%. third (gypsum-rich) type has variable spatial distribution, appearing limestone layers, along footslopes, outcropping metric formations, or generalized karstified subsurface Their composition is almost 100% silt- sand size lenticular gypsum. While some claim for an aeolian origin all these materials, only part them (loess) clear origin, while derives on-site weathering gyprock by precipitation calcium- sulfate saturated watertables it occur other arid regions; rest sensu stricto) mainly colluvial-alluvial. This distinction necessary since they differ their geotechnical behaviour properties relevant agricultural land uses, therefore should be taken into account when carrying out geological mappings soil surveys this similar regions.