Geomorphological evolution of lower river terraces and abandoned meanders of an alluvial segment of the Jacaré-Guaçu river (São Paulo/Brazil)

Author(s)

Éverton Vinícius Valezio

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências
• Defense date: 2022-02-02

Examining board members

Archimedes Perez Filho; José Cândido Stevaux; Marcos Roberto Pinheiro; Eduardo Souza de Morais; Felipe Gomes Rubira

• Advisor: Archimedes Perez Filho

Abstract

Allogenic factors responses on the evolution of fluvial systems are present in the landscape and provide support for paleoenvironmental reconstruction. The current work aimed to understand the environmental conditions and its impact on morphogenesis of alluvial valley located in the medium course of the Jacaré-Guaçu River (SP). The methods applied to understand the landscape evolution consisted of detailed mapping of alluvial forms and features using aerial photographs (1:25,000), unmanned aerial photogrammetric survey, Rapideye and CBERS-2B orbital image, elevation data of Shuttle Radar Topography Mission (SRTM) and ALOS/PALSAR satellite; Optically Stimulated Luminescence (OSL) dating and textural analysis of low-terrace and floodplain deposits; and application of morphometric parameters in the fluvial plain, abandoned, and current meander bends. The results indicated the presence of meanders with superior planimetric dimensions in breadth, width, length, radius of curvature, and depth in the low-level terrace (T1); meander bends with intermediate dimensions in portions of the floodplain and smaller dimensions in the current and recently abandoned meanders, with three sectors differing in hydrological conditions. The identified low river terrace characterized by sandy deposits on the left bank dated from 7,920 ± 1,400 and 7,895 ± 1,480 years BP, and the ancient river channel dated from 14,915 ± 1,380, 75,790 ± 8,820, and 85,070 ± 9,650 years BP, representing a remnant of the migration dynamic in the river. In the floodplain, the left and right bank deposits have similar ages, varying between 2,910 ± 405 and 3,370 ± 300 years BP. The asymmetry of the fluvial plain in relation to the fluvial channel layout, as well as the direction of the tributary channels, suggested neotectonic processes, which favored the lateral migration of the river to the northern sector and the erosion of older alluvial deposits on the right bank. Furthermore, the climatic factor occurred concomitantly, as responsible for conditioning the type of transported load and the morphology of the meander bends. The established and remnant floodplain forms and their respective measurements and dating, suggest changes in the precipitation and runoff dynamics in the last thousands of years, resulting in the undersizing of the Jacaré-Guaçu river as a response to the climatic implications after the Last Glacial Maximum (AU)

• FAPESP's process: 16/24390-0 - Geomorphological evolution of lower river terraces and abandoned meanders of an alluvial segment of the Jacaré-Guaçu river (São Paulo, Brazil)
• Grantee: Éverton Vinícius Valezio
• Support Opportunities: Scholarships in Brazil - Doctorate