Aeolian dust accretion outpaces erosion in the formation of Mediterranean alpine soils. New evidence from the periglacial zone of Mount Olympus, Greece

Abstract

Soil formation in Mediterranean periglacial landscapes remains poorly understood as the interplay between erosion and aeolian dust accretion in providing parent materials, and mineral weathering and pedogenesis, as dominant post depositional processes, depends on a variety of local and regional factors. Herein, we investigate the balance between erosion and aeolian dust accretion in the formation of an alpine soil profile along an erosional gradient in the periglacial zone of Mount Olympus in Greece. We applied a wide range of analytical methods to 23 samples, from a soil profile developed in a glaciokarstic plateau, from colluvial sediment horizons interbedded in postglacial scree slopes and from modern Sahara dust samples deposited on the snowpack. Colluvial sediment horizons exhibit high concentrations of calcite rich sand and represent the local erosion products. The soil B horizon developed on a glaciokarstic plateau contains high amounts of fine earth and is rich in quartz, mica, plagioclase, clays, and Fe-Ti oxides. Based on its physical and textural characteristics the soil profile is partitioned in a surficial weathered Bw and a lower illuvial Bt horizon that overlies the local regolith composed of fragmented glacial till and slope wash deposits. Radiogenic isotope systematics, textural and mineralogical analysis show that the contribution of Sahara and locally sourced dust to the development of the soil B horizon ranges between 50 and 65%. Cryoturbation results in fine earth translocation from Bw to the Bt horizon, whereas weak pedogenetic modifications of aeolian and bedrock-derived minerals result in magnetic mineral weathering and secondary clay formation. Our findings reveal that, aeolian dust accretion is the dominant process in providing alpine soil parent material and that cryoturbation, weak pedogenesis, and clay mineral alteration occur within the Mediterranean periglacial zone of Mount Olympus.