Geochemistry and mineralogy of the Late Pleistocene loess-palaeosol sequence in Złota (near Sandomierz, Poland): Implications for weathering, sedimentary recycling and provenance

Abstract

In order to determine the provenance of material, the Late Pleistocene loess-palaeosol sequence in Złota (Poland) was analysed geochemically (ICP-MS, ICP-ES) and mineralogically (QEMSCAN®), investigating simultaneously the weathering signature and effect of sedimentary sorting. A total number of 39 loess and soil samples were tested for the geochemical composition, and 5 for the mineralogy. The investigated samples, compared to upper continental crust, are enriched with elements such as Si, Zr, Hf, Nb, Ta, Th, U and rare earth elements (especially the heavy rare earth elements) related rather to felsic igneous rocks. The enrichment of only two mafic elements (Ti and Cr) can be explained by heavy minerals admixture. Loess in Złota is strongly mixed and homogenized during transportation and/or sedimentary recycling. For each sample the uniform shape of the chondrite-normalized rare earth elements patterns were found, characterized by steep light rare elements (LaN/SmN = 3.45 – 4.08, avg. 3.81), constant negative Eu anomalies (Eu/Eu* = 0.50–0.63; avg. 0.56) and distinctly flat heavy rare earth elements (GdN/YbN = 1.17–1.45, avg. 1.28). The material is not significantly affected by chemical weathering and the post-depositional modifications are not particularly important for the trace element composition both in loess and soils (e.g. Th/U = 3.1–4.65, avg. 3.64; Ce/Ce* = 0.96–1.09, avg. 1.01; LaN/YbN = 6.22–7.93, avg. 6.94). The research reveals that relatively “fresh”, felsic-related parent material has been well-mixed during transportation, but post-depositional alterations (related only to the pedogenesis) have not been intense enough to mask their chemical signature. The investigated material has been probably originated in Scandinavia (likely Norway), but deflated directly from the glacial drift covering the terrain of Poland.