GRANULOMETRIC ASPECTS AND SOURCE AREAS OF THE SEDIMENTS FROM THE CONFLUENCE OF TOCANTINS AND ITACAIÚNAS RIVERS: MARABÁ-PA CITY, BRAZIL

Abstract

ABSTRACT The Tocantins and Itacaiúnas Rivers, located in Marabá city, southeast of Pará State, represent the main rivers of the region and they are distinguished by the abundance of water resources and sediment transport. The scarcity of sedimentological studies along the confluence of the Tocantins and Itacaiúnas Rivers encouraged this research, in order to provide considerations about the sediment transport and provenance through granulometric analysis and heavy mineral assemblages. The granulometric analysis was based on sediments collected along three profiles I-III, 20 samples total. The transverse profiles I and II, along the Tocantins river, displayed particle size variation due to differences in transport energy. In the longitudinal profile III, along the Itacaiúnas River, there was little particle size variation, indicating high and homogenous flow energy. The identified heavy minerals were zircon, tourmaline, staurolite, rutile, sillimanite, and garnet, which demonstrate a diversity of shapes, roundness, colors, and textures, suggesting igneous, metamorphic and sedimentary sources. The ZTR index (zircon + tourmaline + rutile) indicate a high degree of mineralogical maturity for sediments from the Tocantins River and moderately in the Itacaiúnas River.