Original paper
Changes of the base levels in the Ivaí and Paraná Rivers confluence zone (Southern Brazil): Denudational reflexes in the evolution of the upstream drainage network
do Couto, Edivando Vitor; dos Santos, Leonardo José Cordeiro; de Sordi, Michael Vinicius; Bourlès, Didier; Braucher, Régis; Salgado, André Augusto Rodrigues; Léanni, Laettitia; Ferreira, José Hilário Delconte
Zeitschrift für Geomorphologie Volume 62 Issue 1 (2018), p. 23 - 40
published: Dec 20, 2018
published online: Sep 11, 2018
manuscript accepted: Jul 16, 2018
final revised version received: Jul 10, 2018
manuscript revision requested: Apr 23, 2018
manuscript received: Feb 6, 2018
ArtNo. ESP022006201002, Price: 29.00 €
Abstract
Large river confluence zones are highly flexible and dynamic environments over time. The changes of the base levels in the confluence zone and their reflexes in the evolution of the upstream drainage network are foundation for the reconstruction of the past of landscapes. This paper aims to comprehend the changes on the base levels in the Ivaí and Paraná Rivers confluence zone (Southern Brazil) and the denudational reflexes in the Ivai River’s tributaries morphodynamics. The results are based on river-borne 10Be concentrations were measured in fluvial sediments from 14 catchments draining both sides of the downstream Ivaí River (DIR) to quantify the catchment-wide long-term denudation rates and river profile analysis of the main tributaries which flow to the downstream Ivaí River near the confluence between Ivai and Paraná rivers. The dynamics and quaternary evolution of the small tributaries from both sides of the Ivaí River was studied. We mapped as morphological evidence a drainage rearrangement map presenting elbows of capture, low divides and over-dimensioned valleys, knickpoints and χ-maps. The DIR network presents typical morphologies of drainage rearrangement in which predominant features are associated with fluvial capture and, the drainage channels exhibit several knickpoints. It has been determined that, while for the left bank of the Ivaí River there is it is determined an average denudation rate of 10.9 (±2.7) m Myr–1, for the right bank it is 6.4 (±1.30) m Myr–1. These denudation rates evidence a major stream power and a more heterogenic drainage pattern on the left river bank. The data demonstrate that changes in the regional base level caused by changes in climate and tectonic movements directly affected the confluence areas of the Paraná and Ivaí Rivers, resulting in deepening of the main thalweg, which consequently caused the rejuvenation of the tributary rivers and induced the regressive erosion of the tributary of the confluence zone.
Keywords
Ivaí River • Paraná watershed • fluvial rearrangement • 10Be cosmogenic nuclides