Drainage anomalous and morphotectonics controls of the terraces evolution Ivinhema river low course – MS

Abstract

Ivinhema River is an important tributary located on the right side bank of Paraná River, which crosses a series of terraces, floodplains and other features of relief. A thorough study was proposed on that river, and based on the investigation performed, it was elaborated. a geomorphologic mapping, a longitudinal profile and dating, by using 14C and Thermoluminescence. Afterwards, it was carried out the identification of block rotation through NW and N diving, limited by antithethic faults, subordinated to the lineament of Paraná River, which have controlled the channel sinuosity, the distribution of the of floodplains and the valley asymmetry. Based on the data collected, it was possible to deduce and evaluate the climatic tectonics and depositional evolution, which occurred since Paleocene to Holocene Period. In Paleocene there was a deposition of oligomitic gravel, usual in arid climate, in the Mio-Pliocene; and a tectonic reactivation has determined the limits of Paraná and Paraguai River basins. In Upper Pleistocene, a sedimentary succession, associated to Paraná and Ivinhema River dynamics, built intertwined channels. In Holocene, a tectonic pulse was responsible for the antithetic faults that uplifted the blocks that were parallel to Paraná River. Finally, in the pluvial phase (Hipsithermal - between 8.000 and 6.000 B.P.), the pattern of Paraná River channel would have changed from intertwined, or braided, to sinuous. Keywords: Ivinhema river, Morphotectonics, Terraces.