Detecting neotectonics in the lowlands of Amazonia through the analysis of river long profiles

• Published in: Journal of South American earth sciences 2020-06, Vol.100, p.102553, Article 102553
• Main Authors: Alves, Fabio Corrêa, de Fátima Rossetti, Dilce, de Morisson Valeriano, Márcio
• Format: Article
• Language: English
• Subjects: Digital elevation model; Knickpoint; Normalized steepness index; Remote sensing; Transient landscape
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2020.102553

There has been a considerable number of studies focusing on the analysis of river long profiles based on stream power incision models aiming to detect areas affected by neotectonics. Most of these studies have successfully uncovered active tectonics in mountainous landscapes, with some examples in areas of low reliefs around the globe. However, this kind of investigation has rarely been used in large tropical lowlands, such as the Amazonian lowlands, where the application of river long profiles is still challenging. The main aim of the present work was to test the functionality of methods based on river profiles to detect neotectonic reliefs in lowland landscapes. The Negro River basin was selected for this investigation, assuming the several indications of tectonic activity during the late Pleistocene and Holocene. We tested the normalized channel steepness index (ksn), with the identification of knickpoints and interpretation of swath profiles, computed from the 30 m digital elevation model provided by the Shuttle Radar Topography Mission. The results showed streams with profiles bounded by a set of knickpoints represented by very low ksn values in the right (average ksn = 8) and left (average ksn = 10) margins of the Negro River. These values contrast with the high range of ksn values generally found for rivers of tectonically active mountainous landscapes. Even with low values, we verified that a slight increase in ksn values was enough to detect transient rivers related with strike slip faults in Amazonia lowlands. The swath profiles also showed sectors on relief compatible with changes in the base level of the tributaries, with the record of knickpoints and an increase in ksn values. The experimental results obtained in this work motivate further quantitative investigation in Amazonian lowlands by testing geological data with new robust techniques from river profiles. •SPIM have mostly been used to detect tectonics in mountainous landscapes.•However, testing these models to detect tectonics in lowland reliefs is needed.•We applied river profile analysis in an Amazonian region dominated by strike slip faults.•Tectonically controlled tributaries had elevation curves with base level lowering.•ksn values were low, with a slight increase in rivers nearby strike slip faults.