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Russian Geology and Geophysics

2020 year, number 7

PERIODIZATION OF HOLOCENE CLIMATIC CYCLES BASED ON SYNCHRONOUS VARIATIONS IN THE MAGNETIC AND GEOCHEMICAL PARAMETERS OF THE SEDIMENTS OF LAKE BOL’SHOE YAROVOE (southwestern Siberia)

L.R. Kosareva1, V.P. Shcherbakov1,2, D.K. Nurgaliev1, N.G. Nurgalieva1, N.K. Sycheva2, V.V. Antonenko1, D.M. Kuzina1, V.G. Evtyugin3
1Institute of Geology and Petroleum Technologies, ul. Kremlevskaya 4/5, Kazan, 420111, Russia
2Borok Geophysical Observatory, Borok 142, Yaroslavl Region, 152742, Russia
3Kazan Federal University, ul. Parizhskoi Kommuny 9, Kazan, 420111, Russia
Keywords: Lacustrine sediments, Holocene climate, magnetic properties, ferrimagnetic components, magnetotactic bacteria, coercive spectra

Abstract

Variations in the magnetic and geochemical properties of the sediments of Lake Bol’shoe Yarovoe (Altai Territory) were studied. The data were derived from five core columns (up to 4.5 m long) covering a time interval of more than 8000 years. In addition, coercive spectra were obtained for 792 samples taken every 2 cm. Coercive spectra were then used to identify soft magnetic (10-15 mT) and hard magnetic (35-50 mT) components. The soft magnetic component is detrital, and the hard magnetic component is biogenic, which is confirmed by microscopic studies. Moreover, the samples contain micrometeorite particles. Variations in geochemical properties allow reconstruction of the environmental history of the lake. Sediments in the lower part of the section vary both in the content of ferrimagnetic components and in geochemical properties, which indicates a sharp environmental change between ~6100 and ~7600 years ago. Alternation of warm (dry) and cool (humid) periods is observed higher in the section, between ~4100 and ~6100 years ago. It has been found that the variations in the magnetic components are consistent with the environmental changes and can be used for the historical reconstruction.

DOI: 10.15372/RGG2019148