Análise morfométrica como subsídio à avaliação da influência tectônica no rejuvenescimento topográfico na bacia do Rio Prata, borda ocidental norte da Bacia Sedimentar do Paraná
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Data
2024-02-14
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Universidade Estadual Paulista (Unesp)
Resumo
Abordagens morfométricas adotadas em estudos em ambientes de domínio intraplaca, como a intraplaca brasileira, caracterizados por baixa amplitude tectônica, têm evidenciado a natureza transiente ou o rejuvenescimento destas paisagens, cujo desequilíbrio tem sido comumente associado a variações climáticas e/ou litológicas. No entanto, a influência da tectônica de baixa magnitude no desenvolvimento dos relevos nesses ambientes ainda é pouco compreendida. O objetivo deste estudo foi investigar a geomorfologia de uma porção da borda ocidental norte da Bacia Sedimentar do Paraná com o intuito de reconhecer evidências de influência tectônica. Métricas topográficas, como a análise do perfil longitudinal da drenagem, têm sido eficazes na identificação de perturbações tectônicas, mesmo em regiões intraplaca. A metodologia empregada fundamentou-se na análise integrada de métricas topográficas, tais como perfis longitudinais de drenagem, knickpoints e o índice de inclinação do canal (ksn), juntamente com propriedades morfométricas adequadas para identificação de indicadores tectônicos, incluindo lineamentos morfoestruturais, assimetria de bacia de drenagem, análise do padrão e anomalias de drenagem. A análise dos perfis longitudinais e métricas derivadas revelou uma maior incidência de knickpoints de slope break e vertical step, juntamente com valores mais elevados de ksn nas transições entre as áreas elevadas e rebaixadas. Esses indicadores corroboram a hipótese de influência tectônica no desenvolvimento da paisagem e evidenciam o estado transiente da área de estudo. O mapeamento dos lineamentos morfoestruturais mostrou direções principais N70-80E e N60-70E, consistentes com grandes descontinuidades crustais magnéticas. A presença de sismos alinhados com essas estruturas fortalece a hipótese de que os lineamentos resultam da reativação de fraturas e/ou falhas do embasamento. A análise de drenagem revelou um padrão geometrizado da rede drenagem, evidenciando controle estrutural nos traçados dos canais. Já a análise de fatores de assimetria de drenagem indicou assimetria com direções de basculamentos, em geral, ortogonais a estruturas NE e NW. Os resultados obtidos neste estudo reforçam a suposição da contribuição de estruturas de origem tectônica no rejuvenescimento topográfico. O principal mecanismo tectônico atribui-se às forças compressivas resultantes da interação da deriva da Placa Sul-Americana com a Placa de Nazca, especialmente a terceira fase orogenética da Cadeia Andina, a fase Quéchua. Essas tensões resultaram na elevação e, consequentemente, desencadearam fenômenos tectônicos e/ou reativação de zonas de fraqueza preexistentes.
Morphometric approaches adopted in studies in intraplate domain environments, such as the Brazilian intraplate, characterized by low tectonic amplitude, have highlighted the transient nature or rejuvenation of these landscapes, whose imbalance has been commonly associated with climatic and/or lithological variations. However, the influence of low-magnitude tectonics on the development of reliefs in these environments is still poorly understood. The objective of this study was to investigate the geomorphology of a portion of the western edge of the northern Paraná Sedimentary Basin in order to recognize evidence of tectonic influence. Topographic metrics, such as longitudinal drainage profile analysis, have been effective in identifying tectonic disturbances, even in intraplate regions. The methodology used was based on the integrated analysis of topographic metrics, such as longitudinal drainage profiles, knickpoints and the channel steepness index (ksn), together with morphometric properties suitable for identifying tectonic indicators, including morphostructural lineaments, asymmetry of drainage basin, analysis of drainage patterns, and anomalies. Analysis of the longitudinal profiles and derived metrics revealed a higher incidence of slope break and vertical step knickpoints, along with higher ksn values in the transitions between elevated and depressed areas. These indicators corroborate the hypothesis of tectonic influence on the development of the landscape and highlight the transient state of the study area. Mapping of the morphostructural lineaments showed main directions N70-80E and N60-70E, consistent with large magnetic crustal discontinuities. The presence of earthquakes aligned with these structures strengthens the hypothesis that the lineaments result from the reactivation of fractures and/or basement faults. Drainage analysis revealed a geometric pattern of the drainage network, demonstrating structural control in the channel layouts. The analysis of drainage asymmetry factors indicated asymmetry with tipping directions, generally orthogonal to NE and NW structures. The results obtained in this study reinforce the assumption of the contribution of structures of tectonic origin to topographic rejuvenation. The main tectonic mechanism is attributed to the compressive forces resulting from the interaction of the drift of the South American Plate with the Nazca Plate, especially the third orogenic phase of the Andean Chain, the Quechua phase. These tensions resulted in elevation and, consequently, triggered tectonic phenomena and/or reactivation of pre-existing zones of weakness.
Morphometric approaches adopted in studies in intraplate domain environments, such as the Brazilian intraplate, characterized by low tectonic amplitude, have highlighted the transient nature or rejuvenation of these landscapes, whose imbalance has been commonly associated with climatic and/or lithological variations. However, the influence of low-magnitude tectonics on the development of reliefs in these environments is still poorly understood. The objective of this study was to investigate the geomorphology of a portion of the western edge of the northern Paraná Sedimentary Basin in order to recognize evidence of tectonic influence. Topographic metrics, such as longitudinal drainage profile analysis, have been effective in identifying tectonic disturbances, even in intraplate regions. The methodology used was based on the integrated analysis of topographic metrics, such as longitudinal drainage profiles, knickpoints and the channel steepness index (ksn), together with morphometric properties suitable for identifying tectonic indicators, including morphostructural lineaments, asymmetry of drainage basin, analysis of drainage patterns, and anomalies. Analysis of the longitudinal profiles and derived metrics revealed a higher incidence of slope break and vertical step knickpoints, along with higher ksn values in the transitions between elevated and depressed areas. These indicators corroborate the hypothesis of tectonic influence on the development of the landscape and highlight the transient state of the study area. Mapping of the morphostructural lineaments showed main directions N70-80E and N60-70E, consistent with large magnetic crustal discontinuities. The presence of earthquakes aligned with these structures strengthens the hypothesis that the lineaments result from the reactivation of fractures and/or basement faults. Drainage analysis revealed a geometric pattern of the drainage network, demonstrating structural control in the channel layouts. The analysis of drainage asymmetry factors indicated asymmetry with tipping directions, generally orthogonal to NE and NW structures. The results obtained in this study reinforce the assumption of the contribution of structures of tectonic origin to topographic rejuvenation. The main tectonic mechanism is attributed to the compressive forces resulting from the interaction of the drift of the South American Plate with the Nazca Plate, especially the third orogenic phase of the Andean Chain, the Quechua phase. These tensions resulted in elevation and, consequently, triggered tectonic phenomena and/or reactivation of pre-existing zones of weakness.
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Knickpoints, Perfil longitudinal, Geomorfologia tectônica, Domínio intraplaca, Longitudinal profile, Tectonic geomorphology, Intraplate domain