Climate and Tectonic Aspects of the Quadrilátero Ferrífero (Central Brazil) From the Perspective of Pleistocene Alluvial Fans

Abstract

This study presents data related to the unconsolidated alluvial fans of the Quadrilátero Ferrífero, a little-studied geomorphological and sedimentary feature located in southeastern Brazil. These alluvial fans were submitted to stratigraphic survey and dating by Optically Stimulated Luminescence (OSL). The description and interpretation of the sedimentary facies evidenced a lack of aggradational processes, which are inactive. About 40% of the identified facies are plastic (Gmm) and pseudoplastic (Gcm) debris flows interspersed with occasional channel-filling facies (Gt), hyper-concentrated (Sm) and mud (Fm) flows. The geochronological data elucidated the importance of the SAR protocol, where the quartz grains demonstrated high sensitivity and adequate dose-response curves, allowing better reflections and reliability of determined ages. The unconsolidated alluvial fans of the Quadrilátero Ferrífero had their genesis throughout the Pleistocene, mostly in a dry climate, with vegetation retraction and sedimentary filling of river valleys. The Cenozoic tectonics acted on the surface of the fans through the strong fluvial incision in the Holocene, caused by uplifts of the Brazilian continental shelf.