Interpretación paleoambiental de depósitos siliciclásticos en el sector de Esquivias (Cuenca de Madrid)

Abstract

The occurrence of kerolite-stevensite bearing lithofacies in Neogene Madrid Basin has special outstanding in the Esquivias deposit (Toledo>. In tliis zone Mg elays are bounded at top and bottom by two detrital units. In tliis paper the mineralogical association and sedimentological features of sandy facies related to lower detrital unit (arenas 1), magnesie unit (arenas 2) and upper detrital unit (arenas 3> has been studied. Granulometrie results are: high centile, median values ranging between 0.12 and 0.20 mm. (80¡xm % in arenas 2) and good sorting with ranging between 1.58 and 2.07 (up to 4.5 in arenas 2). The sandy facies mineralogy aJways shows feldspars (Ca-Na>K> predominance over quartz and variable content in mica. Heavy mineral assemblages mainly are made up of: biotite, zircon, apatite, tourmaline, garnet and andalusite. Olten these minerals, even apatites, show euhedrail grains, sometimes with unweathered surfaces. Siliciclastie alluvial sedimentation in saline-alkaline lacustrine environment and semiarid climatie conditions are inferred.