Magnetic properties of lake Kandrykul sediments (Republic of Bashkortostan, Russian Federation)

Abstract

Relevance. It is known that sedimentary deposits in modern lakes with high sedimentation rates contain detailed paleoclimatic, paleobiological, paleoecological and magnetic records. The study of these parameters allow creation of paleoreconstructions and prediction of future climate behavior. Aim. To identify ecological and climatic events and trends during the Late Quaternary, based on magnetic properties of rocks. Some climate-dependent parameters are not properly used, we are showing that magnetic parameters are sensitive indicators of climate change. Object. Sediments of the Lake Kandrykul (Republic of Bashkortostan). Materials and methods. A set of petromagnetic studies was carried out, including measurements of magnetic susceptibility, normal remanent magnetization in external magnetic field of up to 1.5 T, as well as differential thermomagnetic analysis on induced magnetization and scanning electron microscopy on selected samples. Normal magnetization curves were used to set apart dia-/paramagnetic, ferromagnetic and superparamagnetic components. Results. Seismoacoustic studies showed that the lake bed is smooth, without sharp changes. The maximum water depth is about 16 m, the thickness of sediments reaches 7.5 m. Magnetic susceptibility was measured for three core columns, and the results show good correlation of this parameter between all the cores. Thermomagnetic analysis was used to determine magnetic minerals composition. The Day–Dunlop plot showed the presence of single, pseudo-single and multidomain grains. The authors determined the contribution of dia/para-, ferro-, and superparamagnetic components to the overall magnetic susceptibility. The paper considers the variations in magnetic susceptibility, para-, ferromagnetic components in the context of the Holocene climate changes. Conclusions. Variations in magnetic properties reflect climate changes (i.e. deposition environment). Six zones with different depositional conditions were distinguished based on magnetic susceptibility and its component changes. Additionally, zones with single-domain particles were highlighted based on hysteresis parameters variations. These zones most likely are associated with the remains of magnetotactic bacteria. Joint analysis of paramagnetic, ferromagnetic susceptibility and hysteresis parameters produced information on the effect of total humidity on the bioproductivity of the lake.

Keywords

• lake sediments
• magnetic properties
• hysteresis parameters
• biogenic magnetic grains
• paleoclimate
• paleoenvironment reconstruction