Dinâmica fluvial quaternária do rio Maracujá, Quadrilátero Ferrífero (MG)

Abstract

This paper objectives the identification and the optic stimulated luminescence dating (OSL) of the depositional events of Maracujá River, analyzing the correlatives alluvial deposits. Results reveals that the 30 alluvial deposits described along the valley corresponds to four depositional events. The oldest event (N4) corresponds to the residual deposits located in hills along the valley, located 10 m above the river. The following event (N3) corresponds to the clayey alluvial deposits with 4 m thick located 2,5 m above the modern river. The event named N2 corresponds to the clayey deposits with 3 m thick located by the riverbed. The most recent event (N1) corresponds to the siltysandy deposits located by the riverbed. The increase of the sediments size between the previous events and N1has been interpreted as a direct response to the mining and gullies which supplies coarse sediments (sand size) throughout the last centuries. This load is not transported by the river, not even during the floods. Therefore, the Maracujá River used to be a meandering, as evidenced by the clayey deposits N4, N3 and N2 and it is changing to braided channel.