Resumo

ARIZA, Juan P et al. Remote sensing and magnetism applied to study land paleozoic in central andes, San juan, Argentina. Geoacta [online]. 2014, vol.39, n.1, pp.138-153. ISSN 1852-7744.

Remote sensing and magnetism as applied to the study of Paleozoic terranes in the western Precordillera (31º20’ S), San Juan, Argentina are examined. In this contribution, RGB band ratios and supervised and non-supervised classification techniques were performed on Landsat 7 Enhanced Thematic Mapper (ETM+) satellite images. The study area corresponds to a part of the Argentine western Precordillera. In order to shed light on the stratigraphic and structural issues in the surroundings of the upper course of the San Juan River, the RGB band ratio (7/5, 5/4, 3/1) was applied. The results of digital processing in combination with field controls allowed us to postulate that the reddish-brown and yellowish-brown shades represent silicoclastic sedimentary levels, while light green and green colors correspond to levels where basic igneous rocks predominate. Moreover, supervised and non-supervised classifications have not contributed significantly to the present study due to their serious limitations regarding the differentiation of geological units. This limitation could be related to the spectral variability of the rocks from the study area. To complement this, the regional structural fabric was established by processing a Digital Elevation Model (DEM) and the obtained results allowed us to interpret three sets of fractures that, in order of importance, are: a NW-SE system, a N-S system and an E-O system. A survey of field structures was performed in order to control the accuracy of the structural interpretation made by the DEM processing. The study of the magnetic susceptibility of the rocks provided a very significant tool for field work and the range of variation of this parameter for each lithologic group was established. The combined analysis of the above-mentioned multidisciplinary evidence allowed us to reassert that the area is the result of a complex and polyphase deformation history and that the modern structure of the western Precordillera has been controlled by ancient lineaments that result from its complex evolution. The application of alternative mapping techniques and satellite imagery and DEM processing in addition to the study of magnetic properties constitute a powerful tool to use in detailed geologic-structural studies.

Palavras-chave : Remote sensing; Digital elevation model; Magnetic susceptibility; Band ratio.

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