Palaeomagnetic suitability of a new section with a potential lower boundary for the Quaternary on the left bank of the lower River Danube

Abstract

A first palaeomagnetic study has been carried out on a new section with a potential lower boundary interval for the Quaternary, Dolynske 3. Recently, the Matuyama-Brunhes boundary (at 780 ka) was detected in the adjacent section of Dolynske 2. The current study focuses on the hydromorphic palaeosols, loesses and pedosediments of the Bogdanivka to Kryzhanivka units. Taking into account previous palaeomagnetic data from other sections of the loess/soil formation of Ukraine, the Gauss-Matuyama boundary (2.58 Ma) could be expected to be at the top of the Bogdanivka soil unit. However, rock magnetic and magnetostratigraphic results from the Dolynske 3 section indicate an extremely low concentration of the ferrimagnetic minerals and the absence of a characteristic component of magnetisation due to the influence of hydromorphism. Only two samples from the Bogdanivka and Berezan units show a clearly defined reversed polarity; the rest of the samples were uninformative and were rejected from the interpretation. Given the unsuitability of hydromorphic palaeosols and loesses for magnetostratigraphic studies, the determination of the Gauss-Matuyama boundary requires additional, including methodological, research on other sections of Ukraine. The stratigraphic completeness of the composite Dolynske section, its geomorphological location within the Pliocene Danube terraces and convenient geographical setting allow offering it for study as a reference section for the loess/soil formation in Europe. In addition, the Dolynske 3 section potentially may be regarded as a complete continental analogue of the Calabrian and Gelasian with both palaeomagnetic boundaries. Thus, the Dolynske section deserves research on many aspects of the Quaternary, including correlations of loess-palaeosol, alluvial and marine facies, the influence of hydromorphism on palaeomagnetic properties of rocks, «structures» of climatic rhythms in the Calabrian and Gelasian, as part of a separate international project.