Elemental geochemistry of freshwater snail shells: palaeolimnology of a Holsteinian (MIS 11) deposit from eastern Poland |
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| Abstract: | The elemental shell chemistry of two freshwater snails, Viviparus diluvianus (Kunth) and Valvata piscinalis (Müller) was studied for palaeoenvironmental purposes. The shells were collected from lake sediments from five Holsteinian (Marine Isotope Stage 11) sites in eastern Poland (Ossówka, Hrud II, Roskosz, Ortel Królewski and Szymanowo) and analysed for Ca, Mg, Sr, Mn and Fe. The Fe/Mn molar ratio was used as a redox indicator, with lower values (and high Mn concentrations) pointing to suboxic conditions. These occurred in the beginning of the Taxus zone and during the transition between the Taxus and Pinus‐Larix zones at Ortel Królewski, and in the Holsteinian thermal maximum (Carpinus‐Abies zone) at Roskosz Lake. Strongly reducing conditions, indicated by increased Fe and Fe/Mn values, prevailed at Ortel Królewski palaeolake in the middle of the Taxus zone, in the Pinus‐Larix zone and in the upper part of the Roskosz sequence. Indicators of anoxia correlate with eutrophic conditions, enhanced productivity and oxygen consumption due to organic matter decay. The most distinct environmental changes in the records are comparable to other central and northern European records and to the main climatic oscillations during the Holsteinian, inferred from palynological, malacological and isotopic data. |
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