Genesis of ferruginous duricrusts and its linkage to paleoclimates and long-term landscape evolution of the Alto Paranaíba region, Minas Gerais, Brazil

Abstract

Ferruginous duricrusts are ubiquitous in relict paleosurfaces along humid/semi-humid tropical and subtropical zone, such as in South America, India, Africa and Australia. They are often very old and may have been formed since the Late Cretaceous (~ 65 Ma), which characterizes them as a potential marker of paleoclimates and long-term landscape evolution. However, the processes and events related to their formation, transformation and distribution are still obscure. During weathering secondary supergene minerals precipitate in ferruginous duricrusts. They mainly consist in iron oxides (hematite), oxyhydroxides (goethite), kaolinite and gibbsite, often in a polycrystalline arrangement. Thus, a detailed characterization of their micromorphology, mineralogy and geochemistry combined to their age will may be helpful to elucidate their formation processes as well as their relation to paleoclimates and long-term landscape evolution. Our main objective is to identify and characterize different generations of goethite and hematite grains from ferruginous duricrusts that occur in relict paleosurfaces, supposedly of the Lester King's Sulamericana Surface, occurring in a representative catchment of the Alto Paranaíba region (Minas Gerais state, Brazil). Ferruginous duricrusts were described and samples were collected in different layers. Some samples will be selected for micromorphological, mineralogical and geochemical analyses to identify and characterize different generations of goethite and hematite grains that will reveal ancient weathering episodes. These analyses will be carried out at the Institute of Mineralogy, Materials Physics and Cosmochemistry (IMPMC) at the Sorbonne Université in partnership with GEOPS research laboratory (Paris Sud université, France) under the supervision of Dr. Thierry Allard, Dr. Cécile Gautheron and Dr. Cécile Quantin. (AU)