Preprints
https://doi.org/10.5194/esurf-2021-63
https://doi.org/10.5194/esurf-2021-63

  24 Aug 2021

24 Aug 2021

Review status: this preprint is currently under review for the journal ESurf.

Climate changes and the formation of fluvial terraces in central Amazonia

Ariel Henrique do Prado1,2, Renato Paes de Almeida2, Crisitano Padalino Galeazzi2,4, Victor Sacek3, and Fritz Schlunegger1 Ariel Henrique do Prado et al.
  • 1Institute of Geological Sciences, University of Bern, Bern, 3012, Switzerland
  • 2Instituto de Geociências, Universidade de São Paulo, São Paulo, Brazil
  • 3Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil
  • 4School of Earth and Environmental Sciences, Seoul National University, Seoul 21990, Republic of Korea

Abstract. Climate changes have been considered as 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 50’000 and > 200’000 yrs occupy the higher portions of central Amanzonia, whereas multiple terraces next to floodplains occur at lower elevations and display ages of a few thousands of years. These lower terraces, referred to as mid-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 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 Solimões 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 yielded in the construction of mid-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 mid-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 time scale of response to external perturbations, we suggest that the streams in Central Amazonia possibly also respond in rapid and sensitive ways to human perturbations.

Ariel Henrique do Prado et al.

Status: open (until 02 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-63', Anonymous Referee #1, 07 Oct 2021 reply
    • AC1: 'Reply on RC1', Ariel do Prado, 03 Nov 2021 reply

Ariel Henrique do Prado et al.

Model code and software

SPASE_Model Ariel Henrique do Prado https://github.com/Ariel-H-Prado/SPASE_Model.git

Ariel Henrique do Prado et al.

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Short summary
Our work is focused on describing how and why the terrace levels of the central Amazonia were formed during the last 100'000 years. We propose to address this question through a landscape evolution numerical model. Our results show that terrace levels at lower elevation were established in response to dry-wet climate changes and the older terrace levels at higher elevations most likely formed in response to a previously higher elevation of the regional base level.