Geological study of sediments from the Negro and Solimões rivers

Abstract

The Amazon is the largest and most complex ecosystem on the planet, and its entire evolutionary history has been influenced by the dynamics of the Amazon River system. The geomorphological features of sections of the Solimões-Amazonas River have been studied using remote sensing images combined with multitemporal analysis data. Part of the sedimentary deposits is confined within four tectonic depressions formed during the Neomiocene-Pliocene, known as the hemigrabens of Paraná do Ariaú (GPA), Cacau do Pereira (GCP), Cachoeira do Castanho (GCC), and Lago do Miriti (GLM). The objective of this work was to characterize 59 sediment samples from the confluence region of the Negro and Solimões rivers, in the Central Amazon, using instrumental neutron activation analysis (INAA). The experimental results were subjected to cluster and discriminant analyses, revealing the formation of three groups with similar chemical composition. The observed differences are related to the geochemical conditions inherent to each depositional environment.