Sediment Dynamics In Lacustrine Environments — Northern Amazon

Abstract

Lakes are features found in Brazil’s northern region, commonly formed in sandy-clay layers of the Plio-Pleistocene, in a setting of the extensive flat surface, and under a high precipitation rate. Our goal in this work is to understand the sediment transport dynamic and its relation to the hydrological behavior of the regional lacustrine system. Two lakes were selected, Lago do Italiano (LIT) and Lago do Bicho (LB), situated in the municipality of Bonfim in the state of Roraima, Brazil. The lakes differ in hydrological regime, depth, and vegetation. The methodology involved bibliographical and remote sensor data and field surveys followed by laboratory processing. The results revealed that the lakes are composed of sandy materials, with layers what reach 95% of sand. The grains is medium to fine texture, with morphology angular (0 a 50%) and subangular (18% a 43%) grains, disposed at different depths. The grains’ morphology suggests that their sediment provider source is near and, at the same time, indicates a low energy environment. Concerning the mineralogical attributes, the sediments are of a quartzose nature, which permits their correlation with the arenites of the Boa Vista Formation, a sub-cropping unit. The sediment input is controlled by the seasonal oscillation of the groundwater level and inundation pulses that reach the fluviolacustrine plain of the Tacutu River in which the lakes are inserted.