The main goal of this paper is to characterize the Coxim earthquake occurred in June 15th, 2009 in the Pantanal Basin and to discuss the relationship between its faulting mechanism with the Transbrasiliano Lineament. The earthquake had maximum intensity MM V causing damage in farm houses and was felt in several cities located around, including Campo Grande and Goiânia. The event had an mb 4.8 magnitude and depth was 6 km, i.e., it occurred in the upper crust, within the basement and 5 km below the Cenozoic sedimentary cover. The mechanism, a thrust fault mechanism with lateral motion, was obtained by P-wave first-motion polarities and confirmed by regional waveform modelling. The two nodal planes have orientations (strike/dip) of 300°/55° and 180°/55° and the orientation of the P-axis is approximately NE-SW. The results are similar to the Pantanal earthquake of 1964 with mb 5.4 and NE-SW compressional axis. Both events show that Pantanal Basin is a seismically active area, under compressional stress. The focal mechanism of the 1964 and 2009 events have no nodal plane that could be directly associated with the main SW-NE trending Transbrasiliano system indicating that a direct link of the Transbrasiliano with the seismicity in the Pantanal Basin is improbable.

Resumo O leque do Negro é um sistema deposicional aluvial que vem sendo construído pelo rio Negro na borda sudeste do Pantanal desde o Pleistoceno. Sua superfície apresenta feições geomorfológicas e drenagem atuais e reliquiares. O rio Negro flui de leste para oeste e integra a Bacia Hidrográfica do Alto Paraguai (BAP), sendo afluente da margem esquerda do rio Paraguai. A bacia de drenagem do rio Negro é um grande anfiteatro de erosão localizado no planalto de Maracaju-Campo Grande, esculpido em rochas paleozóicas e mesozóicas da Bacia do Paraná e em rochas neoproterozóicas do Grupo Cuiabá. O contato entre o planalto e a planície é marcado por escarpa retilínea de direção NNE. O rio Negro apresenta, no planalto, comportamento obsequente em relação ao mergulho das camadas da Bacia do Paraná. A evolução geomorfológica do leque do Negro teve início com a construção de um lobo antigo na saída do planalto, de provável idade pleistocênica, seguido de avulsão para SE e formação do lobo pré-atual, que termina na vazante Santa Clara. O sítio deposicional holocênico é representado pelo lobo atual, formado sobre depósitos distais do megaleque do Taquari, e por uma planície de meandros embutida em vale inciso na porção superior do leque. Terrenos com inúmeras lagoas, semelhantes às da Nhecolândia, ocorrem entre os lobos, constituindo formas relictas preservadas dentro da área do leque do rio Negro.Palavras-chave: rio Negro, leque fluvial, Bacia do Pantanal. Abstract Geomorphological zonation of the Negro river fluvial fan, southeastern border of the Pantanal Basin.The Negro fluvial fan is a depositional system located on the southeastern border of the Pantanal wetland and has been evolving since the Pleistocene. Its surface exhibits modern and relict geomorphological features, such as channels and paleochannels. The Negro River flows westward and belongs to the Upper Paraguay drainage basin. Theater-headed valleys characterize the catchment area on the Maracaju-Campo Grande Plateau, where the Negro River shows an obsequent behavior in relation to Paleozoic and Mesozoic sedimentary strata of Parana basin. A conspicuous NNE escarpment is the natural limit between the source area on the plateau and the depositional setting on the Pantanal wetland. The geomorphological zonation allowed to establish an evolution started in the late Pleistocene when unconfined flows given rise to formation of a proximal lobe. During a period dominated by erosion an incised valley has cut older deposits on the upper fan. Sedimentation during Holocene times has been taken place on the modern distal distributary fan lobe and on the meander belt that aggraded the incised valley.

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