Reappraisal of the relative importance of dynamic topography and Andean orogeny on Amazon landscape evolution

Autor(es)

Bicudo, Tacio Cordeiro ^[1] ; Sacek, Victor ^[1] ; de Almeida, Renato Paes ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Sao Paulo - Brazil

^[2] Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Earth and Planetary Science Letters; v. 546, SEP 15 2020.
• Citações Web of Science: 0

Resumo

The Cenozoic landscape of northern South America evolved under the influence of different geodynamic processes, culminating in the formation of the largest drainage basin on Earth, the Amazon drainage system. The orogeny of the Andean cordillera and the increase in surface denudation induced an asymmetric influx of sediments in Amazonia, which caused an eastward propagation of the Andean sedimentary wedge, reversing the topographic gradient and driving the drainage flow towards the Atlantic Equatorial margin. The low-relief topography of lowlands in Amazonia is also a factor that propitiates this reversal. Concomitantly, variations in the subduction angle of the Nazca plate under the continental lithosphere during the Miocene also contributed to create dynamic topography that perturbed the surface and modified the drainage pattern through time. In the last decade, both surface processes during Andean orogeny and dynamic topography were invoked independently to explain the formation of the present Amazon drainage system connecting the Andes and the equatorial margin. However, hitherto these mechanisms were not considered in a single model, hampering the evaluation of the contribution of each factor on the evolution of the Amazon River. To quantify the combined effect of the different geodynamic processes, in the present work we used numerical models that integrate orogeny, surface processes, dynamic topography and flexural isostasy of the lithosphere. In our results, we present new numerical scenarios for the Cenozoic landscape evolution of Amazonia, showing that the dynamic topography may have affected the environmental evolution in western Amazonia, favoring the development of a megawetland in this region before the establishment of the Amazon River as a transcontinental river. We conclude that, although the formation of the Amazon drainage system can be explained without the influence of mantle convection, variations in dynamic topography may have anticipated the establishment of the transcontinental drainage system a few million years. Furthermore, the stratigraphic evolution and the total Cenozoic sedimentation preserved in the Solimoes Basin is a function of the temporal variations in the amplitude of dynamic topography in northern South America. (C) 2020 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 17/24870-5 - Evolução da bacia hidrográfica do Rio Amazonas: soerguimento dos Andes, clima e outros processos geodinâmicos
• Beneficiário: Victor Sacek
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 17/00461-9 - Desenvolvimento de eletrodos impressos modificados por azul da Prússia e análogos para dispositivos analíticos integrados
• Beneficiário: Juliano Alves Bonacin
• Modalidade de apoio: Bolsas no Exterior - Pesquisa