Soil properties, micromorphology, and mineralogy of Cryosols from sorted and unsorted patterned grounds in the Hornsund area, SW Spitsbergen

Abstract

Patterned grounds are probably the most interesting features produced by natural processes acting on the Earth's surface. Such features occur mainly in polar areas and in high mountains indicating that the origin of patterned grounds is related to frost action and cryoturbation. In spite of the many studies concerning the mechanism of the formation and the various forms of patterned grounds, very little attention has been paid to the qualitative and quantitative analyses of their mineral composition, and especially the mineralogy of the clay fraction. The analysis of the mineralogy of clay fraction is very important due to the finest particles (especially clay minerals) may play a crucial role in cryoturbation and cryosegregation as the particles are mainly responsible for accumulation of water and rheological properties of the ground. Thus, the main aim of the present study was to verify the hypothesis that the presence of swelling clay minerals in parent material favors the development of sorted patterned grounds. To verify the hypothesis, the physical, chemical, micromorphological, and qualitative and quantitative mineralogical properties of Cryosols from sorted and unsorted patterned grounds in the Hornsund area (SW Spitsbergen) were determined. The obtained results show that Turbic Cryosols from sorted patterned grounds featuring clear frost cracking, frost segregation, and cryoturbation are characterized by a lack of clearly developed soil horizons, loamy texture and low content of soil organic matter. Haplic Cryosols show better developed soil horizonation and contain lower amounts of the silt and clay fractions, higher content of the sand fraction and soil organic matter in comparison with Turbic Cryosols exhibiting strong cryoturbation. Micromorphological analysis of Turbic Cryosols indicates frost action manifested by a vesicular microstructure; round, oval, and deformed (mammillated) vesicles as dominant voids; vertically-oriented rock fragments; and silt and silt–clay cappings occurring on rock fragments. In addition, the occurrence of Fe–Mn nodules showing a sharp boundary indicates mixing of soil material. Micromorphology of the studied Turbic Cryosols indicates that cryoturbation prevails over cryosegregation. The soil material of the studied Cryosols is composed mainly of quartz, K-feldspar, plagioclase, dioctahedral mica (muscovite and/or illite), biotite, augite, hornblende, garnet, chlorite, swelling clays (smectite, vermiculite), goethite, and in some cases also calcite and traces of kaolinite. Majority of the minerals are most likely primary minerals inherited from parent material due to weak chemical weathering in the severe Arctic climate conditions and relatively young soils. However, weak chemical weathering of biotite and formation of vermiculite and mixed layered clay minerals also take place. Quantitative mineralogical analysis shows that besides texture and moisture, the mineral composition of soil material may also play some role in the susceptibility to cryoturbation and the formation of sorted and unsorted patterned grounds. However, the small differences in mineral content between the studied Turbic Cryosols and Haplic Cryosols indicate that the mineral composition of parent material is not a crucial characteristic responsible for the formation of sorted patterned grounds.