Concretionary horizons, unusual pedogenetic processes and features of sulfate affected soils from Antarctica

Abstract

Although acid sulfate soils have been previously reported in Maritime Antarctica, no detailed study about the nature of the sulfide oxidation process and its effect on pedogenesis has been carried out to this day. The present study evaluate the soil genesis from Barton Peninsula along two toposequences developed under sulfides influence, emphasizing active chemical processes in a typical periglacial environment of Maritime Antarctica, and the unusual formation of petroplintite. Seven pedons were selected, described, sampled and classified according to the U.S. Soil Taxonomy and the IUSS Working Group WRB. Soil morphological, physical, chemical, microchemical and mineralogical properties were analyzed. The geochemical composition (total contents of Al, Ca, Co, Cu, Fe, K, Mg, Na, Ni, S, Si, Ti, Th, V and Zn) was determined with X-ray Fluorescence Spectrophotometer. Unlike previous studies that considered chemical weathering as insignificant in Barton Peninsula, this study demonstrates that some areas have active and pronounced chemical weathering processes (sulfurization and phosphatization), which cannot be underestimated. These chemical processes, together or individually, promote strong soil acidification, release exchangeable bases and accelerate mineralogical changes. Precipitation of secondary crystalline iron oxides, plinthization and petroplintite formation occur in these soils, resulting in unusual pedogenic features, unknown to occur in Antarctica to this day. Further studies on Antarctic soils with petroplinthic horizons, with or without ornithogenesis, deserve attention regarding micromorphological attributes and clarification about these new, unusual pedological processes in periglacial environments and their possible use as indicators of environmental change.