Magnetostratigraphy and magnetic susceptibility of the best developed Pleistocene loess-palaeosol sequences of Ukraine: implications for correlation and proposed chronostratigraphic models

Abstract

We provide a revised magnetostratigraphy and magnetic susceptibility stratigraphy of the most complete and thickest (to nearly 60 m) loess-palaeosol sequences in Ukraine spanning the past 1 My: the Roksolany (Black Sea Lowland) and Vyazivok (Dnieper Lowland) sections. The Matuyama–Brunhes boundary has been detected in both sequences in stratigraphically different palaeosol units according to current regional chronostratigraphic schemes. Hypotheses of a large magnetic lock-in depth at Vyazivok and lithostratigraphic incompleteness at Roksolany do not resolve this inconsistency. Instead, new chronostratigraphic models following the Chinese loess designation system, which are supported by correlation of the magnetic susceptibility records with the marine isotope record and established magnetostratigraphic control points, are proposed. We conclude that the Matuyama–Brunhes reversal in the Roksolany and Vyazivok sections belongs to the same palaeosol unit, the Shyrokyne (according to our nomenclature, the U-S7), which corresponds to MIS 19. This novel interpretation resolves the inconsistency of the stratigraphic position of the Matuyama–Brunhes boundary in Ukrainian loess, ends long-standing debate regarding the chronostratigraphy of the Roksolany section, and allows precise correlation of the most representative loess-palaeosol sequences of Ukraine with those in the Danube Basin and the Chinese Loess Plateau. It is considered that the Roksolany Tephra in MIS 6 loess unit can be related to the L2 Tephra which is widely distributed in southeastern European loess records and lacustrine archives. In the light of our results, the Roksolany sequence may serve as a national lectostratotype of the Middle Zavadivka (U-L4) loess unit corresponding to MIS 10. Additionally, a generalized pedostratigraphic column of the past 1 My for central and southern Ukraine has been constructed and correlated with the Hungarian, Serbian and Chinese loess stratigraphies, as well as with the marine isotope record down to MIS 25.