Separation of magnetic susceptibility components from magnetization curves

Abstract:

Modern lake sediments are a unique source of information for climate changes, regionally and globally, because all environmental variations are recorded by these sediments with high resolution.

The magnetic properties of Chernyshov Bay (Aral Sea) sediments we investigated from core number 4 (N45^o57'04.2''; E59^o17'14.3'') are taken at far water depth of 9.5 m. The length of the core is 4.16 m. Samples for measurements were taken to plastic sample boxes with internal dimensions 2x2x2 cm. Remanent magnetization curves were measured by coercivity spectrometer for the separate determination of the different contributions to the total bulk magnetic susceptibility. There was measured also magnetic susceptibility using MS2 susceptibility meter. Those operations were done for data comparison between 2 susceptibilities obtained from different equipment.

Our goal is to decipher the magnetic susceptibility signal in lake sediments by decomposing the bulk susceptibility signal of a lake sediment sequence into ferromagnetic (χ_f), dia-/paramagnetic (χ_p) and superparamagnetic (χ_sp) components using data from remanent and indused magnetization curves Each of these component has a different origin: paramagnetic minerals are usually attributed to terrigenous sediment input, ferromagnetics are of biogenic origin, and superparamagnetic minerals may be of either biogenic or terrigenous origin.

Comparison between susceptibility measurements of MS2-Bartington susceptometer and of the coercivity spectrometer has shown good correlation. The susceptibility values measured in two different equipment are fairly close and indicate thus the reliability the proposed method. In research also has shown water level changes in Aral Sea based on magnetic susceptibility.

The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University also by RFBR research projects No. 14-05-31376 – а, 14-05-00785– а.