Evolução geomorfológica e dinâmica hidrossedimentar da Planície Fluvial Paraguai-Corumbá, Quaternário do Pantanal
Carregando...
Data
2017-09-22
Autores
Macedo, Hudson de Azevedo [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
A Bacia Hidrográfica do Alto Paraguai (BAP) é constituída por áreas que apresentam características distintas no que concerne aos aspectos tanto biológicos como físicos, tendo o Pantanal como a mais evidente destas e sendo constituído por diversos sistemas hidrogeomorfológicos, com o rio Paraguai como espinha dorsal desses sistemas. As planícies fluviais do rio Paraguai, dentro do Pantanal, possuem dinâmica hidrossedimentar peculiar e grande importância por serem o principal coletor deste imenso trato deposicional. Considerando sua importância e as peculiaridades hidrogeomorfológicas deste sistema, a presente pesquisa visa investigar a evolução quaternária e a dinâmica hidrossedimentar atual da Planície Fluvial Paraguai-Corumbá (PFPC). Para o desenvolvimento deste trabalho, dados de sensoriamento remoto, sedimentológicos e geocronológicos foram utilizados para o estudo da evolução geomorfológica da planície. Dados hidrossedimentares (levantamento em campo e dados secundários) possibilitaram a compreensão da dinâmica hidrossedimentar da área. O mapeamento geomorfológico permitiu identificar três unidades geomorfológicas na área, que possuem feições fluviais deposicionais. A PFPC é composta por cinturões de meandros e rede de paleocanais na bacia de inundação. Paleocinturão de meandros foi reconhecido na PFPC e exibe paleoformas deposicionais que indicam condições hidrossedimentares diferentes das atuais. A bacia de inundação do rio Paraguai apresenta uma drenagem formada por formas canais-elevados. Na porção sul da bacia, esses canais convergem para formar canais meandrantes com espiras de meandros semelhantes aos existentes em região mais ao sul do Pantanal. A origem e evolução dessas associações morfológicas estão condicionadas tanto por fatores climáticos como pela configuração da área em relação à bacia hidrográfica. Com base no mapeamento, interpretação dos compartimentos geomorfológicos reconhecidos na área e datações absolutas das formas, esquema evolutivo da geomorfologia da planície foi proposto: 1) Formação de canais-elevados na bacia de inundação do rio Paraguai, durante o Pleniglacial (50 – 20 ka AP); 2) Formação do antigo cinturão de meandros do rio Paraguai, no final do Pleistoceno e início do Holoceno, truncando as formas canal-elevado na bacia de inundação; 3) Com a progressiva melhora climática e aumento das vazões no Holoceno superior, avulsão ocorreu no rio Paraguai na altura da baía do Castelo, construindo seu cinturão atual. As gerações de formas identificadas e mapeadas, que resultaram em um padrão de sobreposição de diferentes estilos fluviais, registram significativas mudanças paleoambientais e paleo-hidrológicas que vêm ocorrendo desde o Pleniglacial. No que diz respeito à dinâmica hidrossedimentológica, levantamentos hidrossedimentares revelaram que a PFPC é um sistema hidrogeomorfológico complexo e peculiar, com perturbações na descarga do rio Paraguai, geradas por pelo menos dois fatores: a configuração geológico-geomorfológica e a hidrologia da área. Ambos propiciam o aparecimento de fenômeno hidrológico ainda pouco estudado no Pantanal: efeito remanso (backwater effect), responsável por perturbações nas vazões do rio Paraguai, que tem sua morfodinâmica também alterada.
The Upper Paraguay River Basin (UPRB) is constituted by areas with distinctive characteristics, both biological and physical, with the Pantanal being the most evident of these areas and being composed by several hydrogeomorphological systems, with the Paraguay River as the trunk of these systems. The fluvial plains of the Paraguay River within the Pantanal have a peculiar hydrosedimentary dynamics and great importance because they are the main collector of this huge depositional tract. The present research investigates the Quaternary evolution, as well as the current hydro-sedimentary dynamics of the Paraguay River, in the Paraguay-Corumbá River Plain (PFPC). For the development of this research, remote sensing, sedimentological and geochronological data were used. Hydro-sedimentary data (field survey and secondary data) allowed the understanding of the hydro-sedimentary dynamics. Through geomorphological mapping three geomorphological units were identified in the area: 1) The floodbasin of the Paraguay River presents a drainage formed by elevated-channels. On the southern portion of the floodbasin, these channels converge into meandering channels with scroll bars, similar to those present in the southern Pantanal region. The origin and evolution of these morphologies are influenced both by climatic factors and the arrangement of the area relative to the basin; 2) Depositional fluvial landforms composed of abandoned meander belt on the floodbasin. This meander belt shows depositional landforms indicating different hydro-sedimentological conditions; 3) Active meander belt of the Paraguay River. With the inclusion of chronological data, an evolutionary sequence of the geomorphology of the area was proposed: 1) formation of elevated-channels in the Paraguay River floodbasin during the Pleniglacial (50 - 20 ka AP); 2) formation of the former meandering belt of the Paraguay River, at the end of the Pleistocene and early Holocene, truncating the elevated-channel forms in the floodbasin; 3) With the progressive climatic changes and increasing river discharge in the upper Holocene, an avulsion occurred in the Paraguay River near Castelo Bay, and built the current single-channel meander belt. The identified and mapped landforms, which produced overlapping fluvial styles, have recorded paleoenvironmental and paleohydrological changes since the Pleniglacial. Hydro-sedimentary surveys revealed that the Paraguay-Corumbá plain is a complex and peculiar hydro-geomorphological system, with disturbances in the Paraguay River discharge created by at least two factors: 1) The geological-geomorphological arrangement; and 2) The hydrology of the area that facilitate backwater effect, a hydrological phenomenon that is poorly studied in the Pantanal wetland. This phenomenon causes disturbances in the Paraguay River discharge and morphodynamics.
The Upper Paraguay River Basin (UPRB) is constituted by areas with distinctive characteristics, both biological and physical, with the Pantanal being the most evident of these areas and being composed by several hydrogeomorphological systems, with the Paraguay River as the trunk of these systems. The fluvial plains of the Paraguay River within the Pantanal have a peculiar hydrosedimentary dynamics and great importance because they are the main collector of this huge depositional tract. The present research investigates the Quaternary evolution, as well as the current hydro-sedimentary dynamics of the Paraguay River, in the Paraguay-Corumbá River Plain (PFPC). For the development of this research, remote sensing, sedimentological and geochronological data were used. Hydro-sedimentary data (field survey and secondary data) allowed the understanding of the hydro-sedimentary dynamics. Through geomorphological mapping three geomorphological units were identified in the area: 1) The floodbasin of the Paraguay River presents a drainage formed by elevated-channels. On the southern portion of the floodbasin, these channels converge into meandering channels with scroll bars, similar to those present in the southern Pantanal region. The origin and evolution of these morphologies are influenced both by climatic factors and the arrangement of the area relative to the basin; 2) Depositional fluvial landforms composed of abandoned meander belt on the floodbasin. This meander belt shows depositional landforms indicating different hydro-sedimentological conditions; 3) Active meander belt of the Paraguay River. With the inclusion of chronological data, an evolutionary sequence of the geomorphology of the area was proposed: 1) formation of elevated-channels in the Paraguay River floodbasin during the Pleniglacial (50 - 20 ka AP); 2) formation of the former meandering belt of the Paraguay River, at the end of the Pleistocene and early Holocene, truncating the elevated-channel forms in the floodbasin; 3) With the progressive climatic changes and increasing river discharge in the upper Holocene, an avulsion occurred in the Paraguay River near Castelo Bay, and built the current single-channel meander belt. The identified and mapped landforms, which produced overlapping fluvial styles, have recorded paleoenvironmental and paleohydrological changes since the Pleniglacial. Hydro-sedimentary surveys revealed that the Paraguay-Corumbá plain is a complex and peculiar hydro-geomorphological system, with disturbances in the Paraguay River discharge created by at least two factors: 1) The geological-geomorphological arrangement; and 2) The hydrology of the area that facilitate backwater effect, a hydrological phenomenon that is poorly studied in the Pantanal wetland. This phenomenon causes disturbances in the Paraguay River discharge and morphodynamics.
Descrição
Palavras-chave
Pantanal, Rio Paraguai, Geomorfologia fluvial, Hidrossedimentologia, Mudanças paleoambientais, Pantanal wetlands, Paraguay River, Fluvial geomorphology, Hydrosedimentology, Paleoenvironmental changes