Estudio petrográfico de los depósitos recientes de relleno de la laguna Salada de Mediana (Zaragoza, España)

• Autores: Pedro L. López Julián, Juan Miguel A. Mandado Collado
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 6, 1, 2004 (Ejemplar dedicado a: IV Congreso Geológico de España (Zaragoza, 12-15 julio, 2004)), págs. 69-72
• Idioma: español
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• Resumen

  • In the Central Ebro Basin (NE Spain, near Zaragoza) there is an active playa-lake saline system called La Salada de Mediana . This system is located within a little basin without surface drainage and developed on Tertiary sedimentary materials. Dilute surficial waters accumulated in the bottom of that depression, evolve under evaporation to become brines in the spring season, reaching total dryness in summertime. The most recent sediments accumulated in the depression have been studied under the petrographic microscope, after obtaining thin sections of material collected from a profile performed in the central area. Just below the surficial saline crust formed in dessication stages (later spring and summertime), a sedimentary blackish level appear. This layer is a 5 cm thick sedimentary accumulation consisting mainly of alabastrine gypsum crystals, with minor amounts of carbonate particles, clays and organic matter. Below this material a light brown sediment occurs, composed almost entirely of gypsum crystals, lenticular in shape but with an alabastrine nucleus. Such textural variations in depth indicate that an important amount of gypsum accumulated in the depression has been transported by surficial runoff and wind. Precipitación of gypsum from the interstitial saturated brine that soaks this filling sedimentary material takes place mainly as overgrowths covering these clastic particles.