Geomorfologia fluvial, mudanças ambientais e evolução do megaleque do Rio São Lourenço, quaternário do pantanal mato-grossense
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Data
2011-04-19
Autores
Corradini, Fabrício Anibal [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O megaleque fluvial do São Lourenço é um sistema deposicional que vem sendo construído pelo rio São Lourenço, desde o Pleistoceno, na porção nordeste da bacia sedimentar do Pantanal Mato-Grossense. Com base na interpretação de imagens orbitais e de dados de campo, foram reconhecidos três grandes compartimentos geomorfológicos no megaleque: a) uma extensa planície fluvial pleistocênica dissecada; b) um cinturão de meandros de idade holocênica, ainda ativo nas porções média/superior do megaleque, mas abandonado na sua porção distal; um lobo deposicional moderno composto por vários lóbulos deposicionais. Depósitos de diferentes compartimentos foram amostrados com vibrotestemunhador, sendo as facies sedimentares descritas e interpretadas em termos de processos e de ambientes deposicionais. As idades dos depósitos dos diferentes compartimentos foram obtidas por meio de datação pelo método de luminescência oticamente estimulada (LOE), o que permitiu a proposição de um modelo evolutivo para a área estudada. Na planície aluval dissecada foram reconhecidas paleorredes de canais distributários formados por lobos ativos durante o Pleniglacial médio, entre 64,8 e 28,5 ka AP. A planície aluvial dissecada foi submetida a processos erosivos, existindo na sua superfície uma rede de canais tributários, que drenam as águas das chuvas para as planícies fluviais periféricas dos rios Cuiabá e Piquiri. A maior evidência do evento de dissecação, que do final do Pleistoceno ao Holoceno superior, é a existência de um vale inciso na porção media/superior do megaleque, cortando os depósitos pleistocênicos dos lobos antigos. O vale tem direção N65E, condicionado pela falha de São Lourenço, e nele se encontra alojado o cinturão de meandros formado por agradação fluvial...
The São Lourenço fluvial megafan is a depositional system which has been built by the São Lourenço river since the Pleistocene in the northeastern region of the Pantanal sedimentary basin of Mato-Grosso State. Based on the interpretation of orbital images and collected data field, three major geomorphological compartments of the megafan were recognized: a) an extensive fluvial plain dissected in the Pleistocene; b) a meandering belt of Holocene age, still active in middle and upper parts of the megafan but abandoned in its most distal portion; and c) a modern depositional lobe consisting of several depositional lobes. Deposits of different compartments were sampled with vibrocorer and the recovered sedimentary facies have been described and interpreted in terms of processes and depositional environments. The ages of the deposits of the different compartments were obtained from dating by the optically stimulated luminescence method (OSL), which allowed the proposition of an evolutionary model for the study area. In the dissected alluvial plain, distributary paleochannels were recognized and formed lobes during the active Middle Pleniglacial, between 64,8 and 28,5 ka BP. The dissected alluvial plain was subjected to erosion, identified through the existence on its surface of a tributary drainage network which drains rain water to the peripheral alluvial plains of the Cuiabá and Piquiri rivers. The strongest evidence for dissection of the event, which starts from the late Pleistocene to the Holocene, is the existence of a valley in the middle/upper portion of the megafan, cutting through the Pleistocene deposits of ancient lobes. The valley has a N65E direction, conditioned by the São Lourenço fault, and it is housed in the fluvial meandering belt formed by aggradation of the valley during the Holocene. The heights of the... (Complete abstract click electronic access below)
The São Lourenço fluvial megafan is a depositional system which has been built by the São Lourenço river since the Pleistocene in the northeastern region of the Pantanal sedimentary basin of Mato-Grosso State. Based on the interpretation of orbital images and collected data field, three major geomorphological compartments of the megafan were recognized: a) an extensive fluvial plain dissected in the Pleistocene; b) a meandering belt of Holocene age, still active in middle and upper parts of the megafan but abandoned in its most distal portion; and c) a modern depositional lobe consisting of several depositional lobes. Deposits of different compartments were sampled with vibrocorer and the recovered sedimentary facies have been described and interpreted in terms of processes and depositional environments. The ages of the deposits of the different compartments were obtained from dating by the optically stimulated luminescence method (OSL), which allowed the proposition of an evolutionary model for the study area. In the dissected alluvial plain, distributary paleochannels were recognized and formed lobes during the active Middle Pleniglacial, between 64,8 and 28,5 ka BP. The dissected alluvial plain was subjected to erosion, identified through the existence on its surface of a tributary drainage network which drains rain water to the peripheral alluvial plains of the Cuiabá and Piquiri rivers. The strongest evidence for dissection of the event, which starts from the late Pleistocene to the Holocene, is the existence of a valley in the middle/upper portion of the megafan, cutting through the Pleistocene deposits of ancient lobes. The valley has a N65E direction, conditioned by the São Lourenço fault, and it is housed in the fluvial meandering belt formed by aggradation of the valley during the Holocene. The heights of the... (Complete abstract click electronic access below)
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Geomorfologia, Geomorphology
Como citar
CORRADINI, Fabrício Anibal. Geomorfologia fluvial, mudanças ambientais e evolução do megaleque do Rio São Lourenço, quaternário do pantanal mato-grossense. 2011. 164 f. Tese - (doutorado) - Universidade Estadual Paulista, Instituto de Geociências e Ciências Exatas, 2011.