COMPARTIMENTAÇÃO MORFOESTRUTURAL E NEOTECTÔNICA DO SISTEMA FLUVIAL GUAPORÉ-MAMORÉ-ALTO MADEIRA, RONDÔNIA-BRASIL

Abstract

The morphodynamic study of Guaporé-Mamoré-Alto Madeira fluvial system has been based on geomorphological and structural data analysis and interpretation. The Cenozoic morphodynamic shows a lithological, climatic and tectonic control, that is main responsible by actual development of the landscape. The fluvial geomorphology and morphological evidences of neotectonic structures nave allowed subdivide the study area in three morphostructural realms: Realm I comprehends the Guaporé and Mamoré hidrographic basin, installed in Beni Subandine Basin; Realm II cross the Guajará Mirim - Porto Velho Structural High, and extends from Mamoré river nearest of Guajará Mirim Structural Barrier to Porto Velho City, where it is named Madeira river; Realm III extends from Porto Velho to Madeira river mouth in Amazonas river, along to Madre de Dios-Itacoatiara structural lineament. The evidences of neotectonic activity are marked by anomalies in the morphology of the fluvial depositional system and anomalies in the drainage network. In the Realms I, the pattern in the structural lineaments show a NW-SE trend, probably, related to sinistrai transpressive faults, cutted to NE-SW e NW-SE transcurrent lineaments, that control the rectangular and pounded lakes. The neotectonic activity observed in the Realm II, is marked by the drainage network control in the trend N-S, with changes NNE-NNW, maybe associated to thrust faulting related to Cenozoic evolution of Andean Orogenesis. The Realm III is strongly controlled by Madre de Dios - Itacoatiara Transtentional Lineament in trend N60E. Therefore, the neotectonic model in the study area is controlled by E-W compressive vector, responsible by growthing or creation of new N-S thrust fault, NE-SW destral transtensive lineaments and NW-SE sinistrai transpressive lineaments.