Análise morfoestrutural e geomorfométrica no escarpamento da margem passiva do Nordeste oriental do Brasil

Abstract

Considering the Eastern Northeast as a vast scenario of morphostructural domains linked to the post-rift evolution of the opening of the South Atlantic and to possible Cenozoic tectonic pulses, a conspicuous example is the Jatobá Sedimentary Basin Southern Border, where the presence of blocks raised above the regional summit, which equal their topographical quotas (or even exceed them), adjacent crystalline massifs and anomalies linked to local fluvial patterns. Thus, this work proposed the investigation of the post-rift topographical evolution mechanisms acting in the area, from morphostructural conditions and evidences in the drainage, using morphological and morphometric parameters, taking, for comparative purposes of the evolution of the landscape in the short term, the summit surfaces of the sedimentary Plateau of Jatobá/PE and of the Massif of Mata Grande/AL, having as sector of interest their respective escapes. From the application of sinuosity indexes of the mountain front (SFM), slope index of the normalized channel (kSN), Hypsometric Integral (IH), Ratio Depth/Height of Valley (RFAV) and by the extraction of relief lineaments, observed the presence of anomalies in drainage patterns (such as knickpoints and rectilinear patterns) and relief compartments (such as plateau ruptures and alignment with the main regional structural trends of preferential NW-SE direction), corroborating the hypothesis that Cenozoic tectonic movements , by the maintenance of erosive escarpments on sedimentary plateaus whose topographic levels are similar to crystalline plateaus, on the same raised surface in a context of passive margin. The results allowed the visualization of possible structural control in the area – especially in the sedimentary sector – since there, the lowest values of the indices used were concentrated, higher density of lineaments, anomalies in the drainage network and concordances between patterns of channels and main structural trends (mainly in the NE-SW and NW-SE directions) of the area, reinforcing the hypothesis of post-rift reactivations, responsible for the lifting of sedimentary blocks and older deposits, above the regional somital summit.