The southeast Brazilian rifted continental margin is not a single, continuous upwarp: variations in morphology and denudation patterns along the continental divide
Fonte-Boa, T.M.R.; Peifer, D.; Fonseca, A.; Novo, T.A. (2022). The southeast Brazilian rifted continental margin is not a single, continuous upwarp: variations in morphology and denudation patterns along the continental divide. Earth-Sci. Rev. 231: 104091. https://dx.doi.org/10.1016/j.earscirev.2022.104091
In: Earth-Science Reviews. Elsevier: Amsterdam; Lausanne; London; New York; Oxford; Shannon. ISSN 0012-8252; e-ISSN 1872-6828, meer
Rifted continental margins (RCM) are large-scale features of Earth's surface that show substantial morphological variations. Classical escarpment features are the subject of many studies in these settings while other morphologies that characterize this tectonic environment receive less attention. The case of the Brazilian South Atlantic margin, a continental-scale topographically pronounced terrain covering >1000 km of the western South Atlantic rifted margin, is not an exception. Most landscape evolution studies concentrate on the Serra do Mar escarpment system, while other segments with no escarpments have received less attention. Various authors assume the Brazilian elevated continental margin as a well-defined and continuous marginal upwarp instead of a diversified and more complex landscape. Here we debate this issue and explore how the first-order topographic forms and time-space denudation patterns differ along the Brazilian South Atlantic margin. We focus on the continental margin of southeast Brazil (CMSEB) that includes a southern segment featured by a prominent escarpment system and a northern segment where the seaward-facing steep escarpment is absent. We show that, similar to other RCMs, the CMSEB presents a continental drainage divide separating two distinct regions with contrasting denudation patterns, (i) an inland continental interior, characterized by high elevation and relatively low relief with a predominance of apatite fission track (AFT) ages significantly older than South Atlantic rifting event, and (ii) a coastal region characterized by low elevations and high relief with the predominance AFT ages younger than the rifting. However, besides the differential denudation associated with the South Atlantic opening, the margin has experienced substantial post-rift exhumation attributed to rock uplift triggered by the reactivation of inherited basement structures. The morphological differences between CMSEB's southern and northern extensions reflect sectors with contrasting geomorphic evolution supporting the idea that the rifted Brazilian RCM is not a single and continuous tectonic setting. Finally, our findings indicate that tectonic inheritance strongly impacts the denudation pattern, which contributes to the geomorphic diversification along the Brazilian RCM.
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