The stratigraphic characterization of cenozoic sedimentary deposits of the Sardinha River Basin, south portion of the Quadrilátero Ferrífero (MG), and the establishment of a geochemical background

Abstract

This work presents the results of the sedimentological and geochemical studies carried out in the Sardinha River Basin, which is situated in the southern portion of the Quadrilátero Ferrífero, in the State of Minas Gerais (BR). This study was based on the faciological characterization of vertical profiles from cutbank and terrace deposits, mineralogical and chemical data related to identified facies, and to the active drainage sediments of the main tributary (bars and channel). Sampling of the recognized facies and current sediments totaled 54 samples. The mineralogy was obtained by X-ray diffraction and the geochemical data was obtained by inductively coupled plasma optical emission spectrometry (ICP-OES). Chemical data were submitted to a principal component analysis (PCA) and used for the application of the tukey inner fence (TIF) method, which allowed for the establishment of background values of the following elements: Fe, Mn, Al, Ba, Cu, Zn, As, Ni, Cr and Co. The PCA results indicate a strong relationship between Mn and current sediments from the Sardinha River. Others geochemical patterns were highlighted by high concentrations of Fe and Mn, related to sand and gravel sediments from bar and channel features, and by high levels of Al and K, associated with fine sediments from the flood plains and oxbow lake deposits. The background results indicate a high background value for As (32.89 mg/kg) and anomalies that refer to high concentrations of Al, Cu, Zn, Ni and Cr, suggesting geogenic sources. Conversely, anomalies that refer to high values of Co, Ba and Mn are related to anthropogenic sources.