Geomorphic features such as drainage captures, knickpoints, paleochannels, and wind-gaps have long been observed in the Amazon region and typically thought to result from climate change and intraplate tectonics. The influence of rock type as a trigger of these landscape transients is largely overlooked. In the eastern Guiana Shield of the Amazon Craton, shield rivers flow over to the sedimentary rocks of the Amazon Basin across a sharp lithologic transition before their confluence with the Amazon River. This transition is marked by an expressive main escarpment (ME) formed over resistant sandstones of the basal units of the Amazon Sedimentary Basin. Here, systematic patterns of divide migration and river captures provide a natural laboratory to study the influence of rock type in landscape transience in a cratonic setting. Through quantitative geomorphologic analysis of the topography, drainage divides, and rivers, we investigate if this sharp lithologic transition contributed to the observed patterns of drainage rearrangement. The results revealed that rivers of larger drainage areas flowing across shorter lengths over the resistant rocks of the ME systematically capture neighbouring basins. We argue that, as tributaries draining the shield respond to downcutting and/or base-level fall of the Amazon River, bedrock incision and knickpoint propagation are differentially slowed down by the resistant rocks according to their incision capacity, generating a series of transients such as drainage capture and divide migration. The widespread and systematic geomorphic features suggest this mechanism could be an important autogenic control of drainage network rearrangement in the Amazon region and other postorogenic landscapes as well. The protracted exhumation of resistant rocks in cratons and intraplate settings may keep landscapes in perpetual disequilibrium depending on their lithological complexity and offer an exceptional natural laboratory to study landscape dynamics associated with rock type.
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