Characterization of loess in central Spain: a microstructural study |
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Authors: | R Garcia Giménez R Vigil de la Villa J A González Martín |
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Institution: | 1.Departamento de Geología y Geoquímica, Facultad de Ciencias, C/ Francisco Tomás y Valiente, 7,Universidad Autónoma,Madrid,Spain;2.Departamento de Geografía, Facultad de Filosofía y Letras, C/ Francisco Tomás y Valiente, 1,Universidad Autónoma,Madrid,Spain |
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Abstract: | The purpose of this paper is to characterize the materials developed in the middle Tajo River valley, Central Spain. These
sediments are loess, the characterization of which has not been reported in the international bibliography. The sediments
are related to the next geological context and their characterization is indispensable to locate the said material in the
adequate environment. A few different methods have been employed in this study, such as the pipette method (for determining
the grain size) and separation of the light and heavy minerals of the sand fraction by using bromoform. The mineralogical
composition was determined by XRD and textural study was accomplished by SEM/EDX. The loessic materials are silt-clay or sandy-silt
that are quite unstable. The mineralogical composition shows quartz, feldspar, calcite and clay minerals. Some samples show
gypsum; this mineral and calcite present dissolution and stability problems. The heavy minerals starting from the sand fraction
are tourmaline, zircon, garnet, staurolite, sillimanite and biotite associations. The studies carried out with SEM show that
the quartz grain surfaces present etch pits typical of the wind-blown origin. |
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