Preliminary Magnetic Mineralogical Studies of the Neopleistocene-Holocene Sediments from Lake Turgoyak

Abstract

This article reports on some preliminary findings of a study on the seismoacoustic profiling of the basin of Lake Turgoyak (Southern Urals) and the magnetic properties of its bottom sediments. In the eastern depressions, the lake sediments are up to 8 m thick. The radiocarbon dating of the sediment samples suggests that the lake is at least 25 000 years old. The seismoacoustic data reveal that the lower part of the section, which is composed of the dense Neopleistocene sediments, accumulated when the water level was lower. The Holocene sediments are poorly consolidated silts up to 4 m thick. The magnetic properties of the sediments were found to be indicative of the environmental conditions and fluctuations in the lake level. The high-amplitude variations in the scalar magnetic values of the sediments point to frequent changes in the sedimentation conditions. The sediments with the highest magnetic susceptibility (χ), natural remanent magnetization (NRM), coercive force (Bc), coercivity of remanence (Bcr), saturation magnetization (Ms), and magnetization remanence (Mrs) are likely to have formed during the periods when sedimentary material was transported by ice, often with a significant influence from wind.

Keywords

• lake sediments
• radiocarbon dating
• paleolimnology
• seismoacoustic profiling
• petromagnetic properties
• coercive spectroscopy
• thermomagnetic analysis