Magnetic properties of lake Bannoe sediments (Southern Urals, Russia)

Abstract

Relevance. Lake sediments contain the unique data on mineral composition and physical properties reflecting environmental and climate changes over the past millennia. These data are extremely important for understanding the environmental processes today and in the future. Magnetic minerals and properties are considered as essential to reconstruct sediment supply and climate fluctuations. Aim. To reveal magnetic susceptibility and coercive spectrometric parameters as relevant for lake cores stratification in accordance with climate terms. Object. Core of Lake Bannoe sediments (length is 512 cm). The age of the core is ~12.5 thousand years old. Materials and methods. The magnetic susceptibility was measured using MFK-1A Kappabridge (AGICO). The hysteresis parameters of the studied sedimentary deposits were determined using a coercive spectrometer (J_meter). Induced magnetization based differential thermomagnetic analysis was performed on an auto-registering magnetic torsion balance using the zero method. Results. The magnetic susceptibility of sediments taken from Lake Bannoe ranges from 0.88 to 7,87∙10-7m3/kg. Differential thermomagnetic analysis revealed the presence of magnetite in these sediments. The Day–Dunlop plot indicated that the magnetic grains in the samples of Lake Bannoe are a mix of single-domain and multi-domain (pseudo-single-domain) particles, with multi-domain grains comprising 70 to 92% of the total. Variations in magnetic susceptibility and its components were analyzed in relation to the Holocene climatic stages as defined by the Blytt–Sernander classification. Conclusions. It is found that the variations in magnetic properties of the studied sediments are in harmony with climate stages of the Holocene. Sediments of Lake Bannoe recorded the Bond event #8 (~11100 years ago), as well as regional aridization events which occurred ~4500 and ~2000 years ago. The results obtained during this study complement already existing paleoclimatology data, which will be interesting to a wide range of researchers – from paleoclimatologists to limnologists and ecologists.

Keywords

• magnetic study
• paleoclimate
• lacustrine sediments
• holocene
• conditions of sedimentation