Magnetic Characteristics of Different Soil Types from Bulgaria

Magnetic studies of different soil types can provide valuable information about palaeoenvironmental conditions at the time they were formed. Results of investigations of rock-magnetism of genetically different soil types, which developed over varying time intervals (Meadow Chernozem - formed during the last 6000 years BP; Leached Cinnamonic soil - formed since the 3rd-2nd century BC and Pellic Vertisoil - the oldest, formed since the Late Pliocene) are presented. The soil profiles of the Leached Cinnamonic and Pellic Vertisoil are characterized by lower values of magnetic susceptibility, as compared to that of the parent materials. It is shown that using percentage frequency-dependent susceptibility (Xfd%) and viscous remanent magnetization (VRM), pedogenic alteration could be detected even in such circumstances. The variations of the parameters measured along the depth of the studied Meadow Chernozem soil profile are characterized by gradual smooth magnetic enhancement, pointing to the absence of secondary redistribution of pedogenic magnetites. In contrast to this case, the two other profiles (Leached Cinnamonic and Pellic Vertisoil) show magnetically enhanced lower (illuvial) horizons due to processes of acid destruction and re-precipitation of the original pedogenic ferromagnetic minerals down the profiles. These specific magnetic properties are of particular importance in using susceptibility variations as a palaeoclimatic proxy record.