Ferricretes em arquivos fluviais quaternários: desdobramentos para a dinâmica fluvial recente no quadrilátero ferrífero/MG

Abstract

Previous studies show the regional occurrence of ferricretes associated with Quaternary alluvial sediments in the Quadrilátero Ferrífero. These studies also pointed out that ferricretes may have slowed down the river incision in some valley sand that ferricretes are not forming in current conditions. In order to test these hypotheses, this study carried out new analyses in the Conceição and Mango river valleys. Undisturbed ferricrete samples were collected for micromorphological characterization and sediment samples were collected for Optically Stimulated Luminescence dating (OSL).The results confirm the previously raised hypotheses. In the Conceição River valley, along accumulation time at the depositional level with ferricretes found in the valley floor was observed, in contrast to a very young flood plain without ferricretes, similar situation to the Mango River valley. Differences in preservation of the N3 ferricrete in relation to the water level in the Conceição River valley and the identification of a new microestructure to the ferricrete in Mango River valley show that these materials are under going slowt ransformation and degradation rather than under formation.