Geochemical and mineral magnetic footprints of provenance, weathering and pedogenesis of loess and paleosols from North Bulgaria

• Published in: Catena (Giessen) 2024-08, Vol.243, p.108131, Article 108131
• Main Authors: Jordanova, Diana, Jordanova, Neli
• Format: Article
• Language: English
• Subjects: age determination; Bulgaria; Carpathian region; catenas; compliance; floodplains; Loess; Lower Danube; Magnetic susceptibility; magnetism; Major, trace and REE geochemistry; paleoecology; paleosolic soil types; Paleosols; Pleistocene epoch; provenance; Serbia; soil formation; tephra; Tephra chronostratigraphy; tuff
• ISSN: 0341-8162; 1872-6887
• DOI: 10.1016/j.catena.2024.108131

•New major, trace and REEs data for Lower Danube loess and paleosols.•Floodplain sediments of Danube tributaries from NW Bulgaria are possible local dust sources.•REEs signature of bulk tephra from second loess allowed robust tephrochronologic dating.•Background and pedogenic magnetic susceptibilities are reliable proxies of dust source and weathering. Loess–paleosol sequences (LPSs) from the Lower Danube region are valuable archives of paleoenvironmental changes during the glacial–interglacial epochs of the Pleistocene. The present study reports a compilation of major, trace and rare earth elements data on bulk material from loess and paleosols samples from nine LPSs from the Bulgarian part of the Lower Danube area and 14 floodplain sediments from localities along the Danube and five of its Bulgarian tributaries. Analyses are complemented by measurements of magnetic susceptibility and its frequency dependence. The obtained results suggest that loess from the Bulgarian plain of the Lower Danube area is characterized by a systematically higher amount of Ti-bearing minerals, hosting higher Cr content as compared to loess from the Romanian plain, Serbia and central European loess. Source–specific geochemical fingerprints revealed compliance with the signature of the floodplain sediments of Danube tributaries fed by the Western Carpathians and the local floodplain sediments from Danube tributaries in NW Bulgaria. The distinct geochemical signal of the bulk material from the visible 20 cm-thick tephra layer in the second loess at the Suhia Kladenetz profile allowed for tephro-stratigraphic correlation of this tephra with Taurano Yellow tuff from the Campanian volcanic field and corresponding tephra layers from regional palaeoarchives. This correlation led to the establishment of a robust chronologic marker for the second loess L2 of Lower Danube loess with an age estimate of 159.3 ± 1.6 ky. Comparison between weathering indices and frequency dependent magnetic susceptibility showed that the weathering of unstable phyllosilicate minerals is linearly related to the increased content of a strongly magnetic pedogenic fraction. Calculated background magnetic susceptibilities along a W – E transect exhibit a systematic decrease and dependence on the Cr/V ratio, revealing the effect of sediment fining along with the changing amount of the mafic component.