Rock-magnetic and paleomagnetic investigation of the Dolni Vestonice Loess Paleosol Sequence.

Abstract:

Loess-Paleosol sequences (LPS) are important archives of Quaternary continental climate and environmental change, and are known for recording reversing magnetic fields, in particular in China. In Europe, the use of LPS with relatively high sedimentation rates as archives of paleosecular variation would both improve their chronology and provide additional knowledge about paleomagnetic field variations over this continent. Here, we present a detailed rock-magnetic and paleomagnetic study of the Dolni Vestonice (DV09) LPS located in the Czech Republic, covering the last 140 kyr. A major objective of this study is to investigate the possibility of extracting a reliable record of paleosecular variation of the Earth’s magnetic field, both in direction and intensity. Vibrating sample magnetometer (VSM) and Magnetic Properties Measurement System (MPMS) characterizations were carried on 286 bulk samples. The anisotropy of low-field magnetic susceptibility (AMS) was determined on 632 oriented samples. Measurements of remanent magnetizations (natural (NRM), anhysteretic (ARM) and isothermal (IRM)), after stepwise alternating field (AF) demagnetizations, were achieved on 212 oriented samples. Rock-magnetic parameters first allowed describing down-sequence changes in the magnetic mineralogy, as well as concentration and grain size of the magnetic assemblage. Characteristic remanent magnetizations (ChRM) were isolated through a principal component analysis (PCA). The Fisher mean of the population of ChRMs yields a declination and inclination of 14° and 63.2°, respectively, with a 95% confidence limit of 1.7°, where declinations range from -101.3° to 69.3° and inclinations from 31.3° to 87.3°. Relative paleointensity (RPI) proxies were tentatively established using several normalizers of the NRM, such as ARM, IRM, and magnetic susceptibility. Quantitative comparison between bulk rock-magnetic and paleomagnetic data permit to describe the significant influence of changing environmental conditions on the paleomagnetic signal at DV, while AMS data constrain the depositional and post-depositional history providing insight into possible particle orientation biases. Lastly, the reliability of DV09 RPI data is further tested by comparing with regional and global RPI records.