Climate changes and the formation of fluvial terraces in central Amazonia inferred from landscape evolution modeling

Autor(es)

do Prado, Ariel Henrique ; de Almeida, Renato Paes ; Galeazzi, Cristiano Padalino ; Sacek, Victor ; Schlunegger, Fritz

• Tipo de documento: Artigo Científico
• Fonte: EARTH SURFACE DYNAMICS; v. 10, n. 3, p. 15-pg., 2022-06-02.

Resumo

Climate changes have been considered an essential factor controlling the shaping of the recent alluvial landscapes in central Amazonia, with implications for explaining the biogeographic patterns in the region. This landscape is characterized by wide floodplains and various terrace levels at different elevations. A set of older terraces with ages between 50 and > 200 ka occupy the higher portions of central Amazonia, whereas multiple terraces next to floodplains occur at lower elevations and display ages of a few thousand years. These lower terraces, referred to as middle-lower terraces, reveal what can be perceived as a stochastic pattern both in space and time. Despite the widespread occurrence of these geomorphic features, no process-oriented analysis has been conducted to explain their formation. Here, we develop a landscape evolution model referred to as SPASE (Sedimentary Processes and Alluvial Systems Evolution) to explicitly account for fluvial erosion and deposition in combination with lateral channel migration to explore the controls on terrace development. The model results show that the higher terraces were deposited under the condition of a higher base level for the basins upstream of the confluence between the Solimoes and Negro rivers. The subsequent decrease in the base level initiated a phase of gradual incision, thereby resulting in the current fluvial configuration. The model also predicts that high-frequency climate changes resulted in the construction of middle-lower terraces at various elevations which, however, are all situated at lower elevation than the higher terrace levels. Our model shows that dry-to-wet shifts in climate, in relation to the modern situation, yield a landscape architecture where middle-lower terrace levels are better preserved than wet-to-dry changes in climate, again if the current situation is considered as reference. Finally, our results show that fast and widespread landscape changes possibly occurred in response to high-frequency climate changes in central Amazonia, at least since the Late Pleistocene, with great implications for the distribution and connectivity of different biotic environments in the region. Because of this short timescale of response to external perturbations, we suggest that the streams in central Amazonia possibly also respond in rapid and sensitive ways to human perturbations. (AU)

• Processo FAPESP: 18/02197-0 - Modelos quantitativos integrados para a sedimentação fluvial quaternária e a distribuição dos biomas de várzea e terra firme no oeste e centro da Amazônia
• Beneficiário: Ariel Henrique Do Prado
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 18/23899-2 - Projeto de Perfuração Transamazônica: origem e evolução das florestas, clima e hidrologia dos trópicos da América do Sul
• Beneficiário: André Oliveira Sawakuchi
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 17/06874-3 - Dinâmica fluvial e depósitos sedimentares no Rio Amazonas: providenciando ferramentas para decifrar a evolução paleogeográfica da Amazônia e depósitos de grandes rios no registro rochoso
• Beneficiário: Cristiano Padalino Galeazzi
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 16/03091-5 - Caracterização das heterogeneidades e modelagem de análogos de reservatórios em depósitos fluviais e eólicos
• Beneficiário: Liliane Janikian Paes de Almeida
• Modalidade de apoio: Auxílio à Pesquisa - Regular