Geomorfologia e cronologia dos depósitos da planície fluvial no Alto curso do rio Paraná, MS/SP
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Data
2018-04-04
Autores
Oliveira, Stefânia Cristino de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O conhecimento da evolução geomorfológica da planície fluvial do rio Paraná, no trecho a montante da barragem de Porto Primavera, é ainda precário, visto que a maioria dos trabalhos publicados sobre este curso fluvial teve como foco o trecho a jusante da represa. Neste contexto, o objetivo desse estudo foi investigar a sucessão de eventos geológicos responsáveis pela evolução e configuração atual do sistema fluvial do Alto rio Paraná, no trecho entre as Usinas Hidrelétricas de Jupiá e Porto Primavera (divisa entre os Estados de São Paulo e Mato Grosso do Sul). Dados de sensoriamento remoto, sedimentológicos, geocronológicos e perfis topobatimétricos foram utilizados para o desenvolvimento da pesquisa. Quatro compartimentos geomorfológicos foram identificados sendo que três destes compartimentos foram datados: Unidade 1, terraço elevado com presença de lagoas circulares e semicirculares; Unidade 2, terraço intermediário com pequenas lagoas e áreas encharcadas (idade LOE de 60.532 ± 6.068 anos); Unidade 3, terraço baixo com paleocanais preservados (idade LOE de 39.774 ± 2.798 anos); e Unidade 4, planície fluvial atual (idade LOE de 8.884 ± 1.576 anos). As unidades geomorfológicas definidas foram correlacionadas com unidades de trabalhos anteriores localizadas a jusante da área estudada. A Unidade 1, Unidade 3 e Unidade 4 são consideradas extensões das unidades geomorfológicas Taquaruçu, Fazenda Boa Vista e Rio Paraná, respectivamente. A Unidade 2 é um compartimento com características morfológicas singulares, portanto, não correlacionáveis com unidades apresentadas em trabalhos anteriores. Também foram identificadas duas zonas de knickpoints que ocorrem, provavelmente, devido a mudanças litológicas no talvegue do rio. Além disso, no trecho estudado o rio Paraná apresenta sinuosidades que podem estar relacionadas com o aporte sedimentar dos afluentes. Registros sedimentares dos depósitos da planície fluvial do rio Aguapeí indicam que o rio apresentava canal com alta energia há aproximadamente 8 mil anos, quando o clima era mais seco que o atual. Posteriormente, cerca 2 mil anos ao presente, a região passa a ter características climáticas semelhantes as atuais.
The knowledge of the geomorphological evolution of the Paraná River fluvial plain in the stretch upstream of the Porto Primavera dam is still precarious, since most of the published works on this fluvial course focused on the stretch downstream of the dam. In this context, the objective of this study was to investigate the succession of geological events responsible for the evolution and current configuration of the river system of the Upper Paraná River, between the Jupiá and Porto Primavera Hydroelectric Plants (between the States of São Paulo and Mato Grosso do Sul). Remote sensing data, sedimentological, geochronological and topobatimetric profiles were used for the development of the research. Four geomorphological compartments were identified and three of these compartments were dated: Unit 1, raised terrace with circular and semi-circular ponds; Unit 2, intermediate terrace with small ponds and soaked areas (OSL age from 60,532 ± 6,068 years); Unit 3, low terrace with preserved paleo canals (OSL age from 39,774 ± 2,798 years); and Unit 4, current fluvial plain (OSL age from 8.884 ± 1.576 years). The defined geomorphological units were correlated with units of previous works located downstream of the studied area. Unit 1, Unit 3 and Unit 4 are considered extensions of the geomorphological units Taquaruçu, Fazenda Boa Vista and Rio Paraná, respectively. Unit 2 is a compartment with unique morphological characteristics, therefore, not correlated with units presented in previous works. Two zones of knickpoints have also been identified that probably occur due to lithological changes in the river thalweg. In addition, in the studied section the Paraná River presents sinuosities that may be related to the sedimentary contribution of the tributaries. Sedimentary records of the deposits of the fluvial plain of the Aguapeí River indicate that this river presented a channel with high energy approximately 8 thousand years ago, when the climate was drier than the present one. Later, about 2,000 years to the present, the region will have similar climatic characteristics to the current ones.
The knowledge of the geomorphological evolution of the Paraná River fluvial plain in the stretch upstream of the Porto Primavera dam is still precarious, since most of the published works on this fluvial course focused on the stretch downstream of the dam. In this context, the objective of this study was to investigate the succession of geological events responsible for the evolution and current configuration of the river system of the Upper Paraná River, between the Jupiá and Porto Primavera Hydroelectric Plants (between the States of São Paulo and Mato Grosso do Sul). Remote sensing data, sedimentological, geochronological and topobatimetric profiles were used for the development of the research. Four geomorphological compartments were identified and three of these compartments were dated: Unit 1, raised terrace with circular and semi-circular ponds; Unit 2, intermediate terrace with small ponds and soaked areas (OSL age from 60,532 ± 6,068 years); Unit 3, low terrace with preserved paleo canals (OSL age from 39,774 ± 2,798 years); and Unit 4, current fluvial plain (OSL age from 8.884 ± 1.576 years). The defined geomorphological units were correlated with units of previous works located downstream of the studied area. Unit 1, Unit 3 and Unit 4 are considered extensions of the geomorphological units Taquaruçu, Fazenda Boa Vista and Rio Paraná, respectively. Unit 2 is a compartment with unique morphological characteristics, therefore, not correlated with units presented in previous works. Two zones of knickpoints have also been identified that probably occur due to lithological changes in the river thalweg. In addition, in the studied section the Paraná River presents sinuosities that may be related to the sedimentary contribution of the tributaries. Sedimentary records of the deposits of the fluvial plain of the Aguapeí River indicate that this river presented a channel with high energy approximately 8 thousand years ago, when the climate was drier than the present one. Later, about 2,000 years to the present, the region will have similar climatic characteristics to the current ones.
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Palavras-chave
Rio Paraná, Compartimentação geomorfológica, Datação LOE, Depósitos quaternários, Paraná river, Geomorphological zonation, OSL dating, Quaternary deposits