Micromorphological features of organo-mineral interactions in soils and soil-like bodies of Thala Hills, East Antarctica

Ice-free regions (oases) in East Antarctica have been recognized for their diverse environmental conditions of soil formation. Understanding the biogenic-abiogenic interactions, composition and dynamics of soil organic matter can provide insights into the resilience of Antarctic ecosystems in the face of environmental changes. Therefore, this study is aimed at the investigation of micromorphological features, biogeochemical properties and composition of soil organic matter across various scales in the soil and soil-like bodies of Thala Hills, East Antarctica. The examined soils are typically characterized by shallow profiles, predominantly coarse textures, slightly acidic to nearly neutral pH levels, and very low organic carbon content. Soil horizons studied differed by content of total organic carbon (from 0.42% in the sub-surface horizons to 13.68% in the topsoil Histic horizon in a wind shelter) and nitrogen (from 0.025% to 1.89%). Organomineral interactions are primarily observed in the form of biofilms, which predominantly develop in wind-sheltered areas and rock cavities. Micromorphological analyses revealed a predominance of primary materials, which are significantly modified by cryogenic processes (seen by vertical mineral alignment, cracks, and numerous packing voids) and physical weathering, with minimal influence from chemical weathering. Microscopic examination of soil thin sections indicated that the microfabric of these soils is predominantly composed of coarse detrital skeleton with abundant voids, while soils generally exhibit a low proportion of fine earth material.