Magnetic study of Late Pleistocene loess/palaeosol sections from Siberia: palaeoenvironmental implications

Rock-magnetic properties, including anisotropy of magnetic susceptibility, were investigated in detail for two loess/palaeosol sections in south-weste rn Siberia (Bachat and Kurtak). The results obtained agree with the 'Alaska n' type of susceptibility variations for the Kurtak section, showing maximu m susceptibility values in loess horizons and minima in palaeosols. For the Bachat section the palaeoenvironmental record, expressed through susceptib ility, is not clear, in spite of the geographical proximity of the two sect ions. Instead, frequency-dependent magnetic susceptibility (FD%) discrimina tes well between loess and palaeosol units, showing maxima in pedocomplexes and minima in loess units. This suggests certain pedogenic formation of fi ne ferrimagnetic grains in soils. Studies of anisotropy of magnetic suscept ibility (AMS) reveal a well-defined sedimentary magnetic fabric for both se ctions. Different origins of loess deposition, pure aeolian at Bachat and a eolian affected by secondary processes at Kurtak are reflected in the AMS p atterns. The two sections also show different high-temperature behaviour of magnetic susceptibility. While for the Bachat section only one type of the rmomagnetic curve was found, the Kurtak section shows different behaviour f or loess and palaeosol units. Magnetic properties of samples from the two s ections are discussed in terms of palaeoclimatic and depositional condition s.