Preliminary Rock Magnetic and Paleomagnetic Data from a 14.5 m Core of Lake Kotokel Sediments (Baikal Region)

Abstract

AbstractLake Kotokel is a medium-size freshwater lake located close to the eastern coast of the Lake Baikal. Kotokel lake lacustrine sediments preserve a unique archive of vegetation and climate history for at least the last 46 kyr. Here we present the first preliminary rock magnetic and paleomagnetic data for Lake Kotokel. A 14.5 m long sediment core was retrieved from a water depth of 3.6 m in the southern part of the lake. Magnetic susceptibility (MS) and its anisotropy were measured from 385 oriented samples. The characteristic component of the natural remanent magnetization (ChRM) was obtained using stepwise alternating field (AF) demagnetization. Results of our rock magnetic analyses were interpreted in conjunction with available paleoclimatic and paleobotanical data. The response of magnetic properties to climatic changes is illustrated by the correlation of MS values with vegetation change in the region as indicated by spore-pollen and diatom data. The ancient geomagnetic field is poorly recorded in the studied sediments. Paleomagnetic directions in the upper part of the core are randomly distributed due both to very weak remanence as well as to mechanical perturbation of sediments, most likely caused by degassing processes in soft gyttja. Unstable and scattered ChRM directions result from secondary mineralogical modifications, such as dissolution of primary magnetic grains and growth of secondary magnetic minerals, caused, in turn, by environmental changes in the study area.KeywordsRock magnetismPaleomagnetismLake sedimentsBaikal regionPaleoclimate