THE MATUYAMA-BRUNHES BOUNDARY AND THE NATURE OF MAGNETIC REMANENCE ACQUISITION IN THE LOESS-PALAEOSOL SEQUENCE FROM THE WESTERN PART OF THE EAST EUROPEAN LOESS PROVINCE

Abstract

Loess-palaeosol sequences from the western part of the East European loess province were palaeomagneticaly studied. The position of Matuyama-Brunhes boundary was found in the sequence at Zahvizdja (East Carpathian Foreland) overlying the surface that corresponds to the VI Dniestre terrace. This boundary is located within the accu- mulation horizon of an interglacial soil devoloped during the time equivalent of oxy- gen isotope stage 19. The lowermost palaeosol of this sequence, located just below the soil containing the Matuyama-Brunhes boundary record, can thus be correlated with oxygen isotope stage 21 and the VI Dniestre terrace was developed during oxy- gen isotope stage 22. Samples from the palaeosols (especially from their accumulation horizons) revealed the presence of secondary (postdepositional) components of mag- netisation, some resistant to alternating field demagnetisation even as high as 100mT. Fine-grained maghemite is most probably the carrier of these components. Subsequent thermal demagnetisation can remove them, to establish the primary palaeodirections. Hematite and magnetite are the main carriers of remanent magnetisation of the loess layers. The degree of possible delay of remanence aquisition in loess sequences was assessed on sediments from three sections sampled in the Volhynia and Lublin Up- lands. Good correlation of directional changes recorded in coeval segments of loess sections shows that the characteristic magnetisation of aeolian deposits from western part of the East European loess province is approximately syndepositional.