Loess provenance in the westernmost part of the lower Danube Basin, Serbia: Geochemical insights from the Velika Vrbica fluvial–eolian section

Abstract

Our study examined the chemical composition of fluvial and eolian sediments at the Velika Vrbica multisection, located on the bank of the Danube River in eastern Serbia, within the westernmost part of the lower Danube (Dacian) Basin. The multisection comprises two discrete sections: an older 2.7 m thick fluvial section, and a younger 11.2 m thick loess-paleosol sequence (LPS). These are exposed along the sides of a gully incised into a Danube River terrace that is covered by loess. Using luminescence dating, litho- and pedo-stratigraphy, and weathering proxies, we conclude that the fluvial section formed during Marine Isotope Stage (MIS) 6, and the overlying loess spans semi-continuously from late MIS 6 to the present. In order to use only elemental ratios unaffected by weathering and grain-size sorting, and thus serving as reliable provenance proxies, we introduce a novel statistical parameter – the path adherence coefficient (PAC). Along with the PAC, we also employ the well-established R² on geochemical data from the fluvial sediments. We identified Zr/Al₂O₃ and TiO₂/Al₂O₃ ratios as the most reliable provenance proxies, enabling us to discern temporal variations in sediment provenance at the Velika Vrbica LPS. The fine-grained portions of the LPS exhibit a significantly different provenance than that of the Danube River sediments. This difference is attributed to the transport of fine, loessial material over long distances, incorporating multiple sediment sources (likely originating from the Carpathians), from beyond the Danube River alluvium, into the loess. In contrast, the coarser, sand-rich sediment within the Velika Vrbica LPS section, which formed during MIS 2, has a more local provenance, having been derived almost exclusively from Danube River alluvium.