Geochemical and Mineralogical Contributions in the Study of Sedimentary Rock (Barreiras Formation) Soils, Recife/Brazil: Implications for Landslides

This study contemplates the geochemical and mineralogical characterization with spatial analysis of the following soil parameters of the “Alto de Santa Tereza” hillside in Recife/Brazil: granulometric; morphoscopic; compositional; chemical; and mineralogical. The general objective of the present study is report on how the weathering in the soil of the slope influenced on the occurrence of landslides. For this purpose, particle size analysis, X-ray diffraction, X-ray fluorescence, Scanning Electron Microscopy, and binocular lens observation were performed. On the studied slope, it was possible to identify two distinct sedimentary facies for the Barreiras Formation sediments: alluvial fans and fluvial channels/floodplains. Featuring, for the most part, sandy-clayey soil with prismatic and spherical, sub-angular to angular quartz grains, moderately selected. Kaolinite and quartz are the predominant minerals in the samples, and silicon oxides and aluminum are the components with the highest percentage. It was noticed that there is a relationship between Ki (silica/alumina ratio) and Kr (silica/alumina ratio and iron oxide) for the studied soils, the Ki values increase linearly with the increment in Kr. The weathering indices demonstrate that the studied soils of Barreiras Formation presented intense chemical alteration. The locations of the previous landslides in region of Recife show that most of the landslide occurrences are associated with the highly weathered zone.