New Data on Paleogeography of Quaternary Coast Sediments of the Rivers of the European North of Russia Using Isotope-Geochemical Methods

Abstract

(1) Background: The Quaternary river bank deposits of the European North of Russia contain several mollusk fossils that can give important past-climate information which is relevant to understand the evolution of climate in the Holocene period and predict future scenarios on climate change. (2) The purpose of the research: reconstruction of the main physical and chemical parameters of the habitat of mollusks based on the determination of the species of mollusks and the study of the isotope-geochemical composition of shells and their host deposits. (3) Object of study: Quaternary deposits of coastal outcrops of the rivers of the European North of Russia: Pechora Sula, Peza, bivalve shells, and their fragments. (4) Results: The revealed macrofauna complexes represented by bivalves (Arctica islandica, Hiatella arctica, Mytilus edulis, Tridonta borealis, Mya truncata, Neptunea despecta) were determined and the variations of δ13C and δ18O (‰) isotopes in the studied fossil bivalve shells were calculated. The data on the concentrations of chemical elements in fossil shells were determined and summarized. The content of elements in mollusk shells varied within the following limits: Fe 101.7−403.3 µg/g (Vastyansky Kon’, river Pechora), Mg 0.38–2.61 µg/g (Vastyansky Kon’, river Pechora), Ba 18.27–60.44 µg/g (village Oksino-River Sula), and Sr 1128.3–2275.34 µg/g (Vastyansky Kon’-village Oksino, river Pechora). The ratio between the elements varies within Ba/Sr 0.011–0.041 (village Oksino- River Sula) and Mg/Fe 0.01–0.15 (Vastyansky Kon’- village Oksino, river Pechora).