Source identification of morainic materials in soils of the Three Lakes region (Switzerland) using the fingerprinting technique

Abstract

In regions of mid- to high-latitudes, soil development patterns are intricately associated with the Quaternary glaciations, which have reworked sediments and deposited a layer of heterogeneous superficial moraines having both autochthonous and allochthonous components. While the allochtony of the morainic material in the Swiss Plateau is widely accepted, the specific proportion of various geologic origins of the soil parent material remains largely unexplored. Fingerprinting techniques have emerged as valuable tools for accurately estimating the origin of the parent material composition. They may unveil the distinct contributions of different rock types to the overall soil composition. In total, 166 sites were analysed for their geochemical composition and the relative contribution of several rock components to them, such as carbonate, sandstone and three groups of rock granite (incl. granite, granulite and gneiss), gabbro (incl. gabbro, Allalin-gabbro and diorite) and serpentinite (incl. serpentinite and eclogite). For each site, an optimal set of elements (between 11 and 17) was selected. Thereby, a three-step statistical selection process was employed that included the range tests, the Kruskal-Wallis tests and a discrimination function. We identified eight key elements – Al, Ca, P, Fe, Mn, Sb, La, and Sm – which consistently appeared across all sites during the selection process. The geochemical composition of the soils of the Three Lakes Region was mainly determined by a mixture between granitic material (53.6%) and sandstone (21.6%) with a smaller contribution of serpentinite, gabbroic and carbonate material. The findings highlight that the FingerPro model can effectively identify the sources of geochemical composition in soils. One major difficulty in such calculations was, however, that sandstones had a relatively variable composition owing to their different origins.