Morphometric, morphological and sedimentary characterization of eroded alluvial fans: a new glance upon the slope deposits of the Quadrilatero Ferrifero

This article presents morphological, morphometric and sedimentary data of inactive alluvial fans sitting on the medium and high slopes of the Quadrilatero Ferrifero, deriving from the high regions adjacent to the main fluvial valleys. In the survey of morphometric and morphological data, in addition to using topographic maps and images from Google Earth, images from the Sentinel-2 satellite, MSI sensor, in the bands 2, 3, 4 and 8 of 10m spatial resolution were used. These images were obtained based on Javascript programming in the Google Earth Engine (GEE) platform. During field work it was possible to raise facies profiles and interpret the sedimentary processes as well as the paleoenvironmental context in which the alluvial fans were generated. These are deposits with advanced erosion processes caused by human occupation and, mostly, by the high incision of drainage courses that occurred in the Holocene. The dismantling of the deposits reflected in the asymmetry of the alluvial fans, countering, therefore, the traditional semi-conical shapes of this features in arid and semiarid regions of the globe. The alluvial fans studied were generated by high energy unconfined processes, mainly by flows of pseudoplastic debris. By comparing the available ages for the investigated fans, obtained through optically stimulated luminescence, to the paleoclimatic data available for the southeastern Brazilian region, it was possible to conclude that the dated facies were filled in a dry paleoclimate.