Significance of the Ukrainian loess-palaeosol sequences for Pleistocene climate reconstructions: rock magnetic, palaeosol and pollen proxies

Abstract

Variations of rock magnetic parameters in loess-palaeosol sequences, related to climatic and environmental conditions during their formation, are a powerful tool for palaeoclimate reconstruction. Combined enviromagnetic study of loess deposits in Ukraine and its assessment for the palaeoreconstruction purposes are carried out in the framework of the National Research Foundation of Ukraine project 2020.02/0406 ‘Magnetic proxies of palaeoclimatic changes in the loess-palaeosol sequences of Ukraine’. Environmental/climatic reconstructions of the past are fulfilled using a significant number of palaeoindicators: morphology and lithological properties of palaeosols and loesses, their pollen assemblages and a wide range of magnetic characteristics. In this paper, we present a multi-proxy approach to palaeoenvironmental reconstructions, and introduce preliminary results obtained from magnetic susceptibility of loess-palaeosol sequences in the northern (at Vyazivok), central (Stari Kaydaky) and southern (Roksolany) parts of the Ukrainian loess belt. The amplitudes of palaeoclimate change established using magnetic proxies are well correlated with the lithological, palaeopedological and palynological patterns of the sites, and with the global oxygen-isotope scale (MIS). Ongoing studies of the Stari Kaydaky section confirm the correlation of the Upper Zavadivka (S3) soil unit and Lower Zavadivka (S4) soil unit with MIS 9 and MIS 11, respectively (this was proved earlier at the Vyazivok and Roksolany sites). The underlying Lubny (S5) pedocomplex likely corresponds to MIS 13, and the Martonosha (S6) pedocomplex to MIS 15. Palaeomagnetic investigations at Stari Kaydaky have not so far reached the Lower Shyrokyne unit, in which the Matuyama—Brunhes boundary has been detected at Roksolany and Vyazivok. The Upper Shyrokyne (S7S1) palaeosol unit has normal polarity and is preliminarily correlated with MIS 17.

Early–Middle Pleistocene Magnetostratigraphic and Rock Magnetic Records of the Dolynske Section (Lower Danube, Ukraine) and Their Application to the Correlation of Loess–Palaeosol Sequences in Eastern and South-Eastern Europe

“…Furthermore, well-developed rubified palaeosol S5 has been equated to S4 corresponding to the very warm interglacial MIS 11. Here, we have adopted the latter suggestion [28] because it is consistent with magnetic susceptibility patterns of the Ukrainian MIS 9-11 soils and corresponds more closely with the general palaeoclimatic reconstructions obtained from the central Ukrainian loess-palaeosol sequences [47,52,150,155,235]. Furthermore, based on our record for MIS 9 and MIS 11 from Roksolany and Vyazivok [150], and the similar palaeosol succession patterns, the former SK-S4 soil unit at Stari Kaydaky [10,11] has been recently reinterpreted as a lower member of the SK-S3 pedocomplex, whereas the well-developed rubified palaeosol SK-S5 below has been renamed as SK-S4 and correlated with MIS 11 [235].…”

“…Based on the position of the MBB in the underlying Shyrokyne unit and the general assumption about the presence of a single MIS 13-15 pedocomplex in Eurasia [292], in Ukraine in particular, the S6 unit at Roksolany and Vyazivok has been previously correlated with MIS 17 [150]. However, recently at Stari Kaydaky [235], we have preliminarily correlated the Martonosha (SK-S6) unit with MIS 15. In contrast to MIS 15, MIS 17 was a relatively cold interglacial as was recorded by global reference curves [141,242,286].…”

“…The K-S5 pedocomplex at Kurortne/Prymorske has been correctly correlated with the Lubny unit previously [48,162] (Table 3). In global reference curves [141,242,286], the MIS 13 interglacial is colder than MIS 15 and especially MIS 11, which better explains the weaker development and relatively colder climate of the Lubny stage, in comparison with the preceding Martonosha period and succeeding Early Zavadivka period [235].…”

“…Additionally, we compare our magnetostratigraphic and magnetic susceptibility records from Dolynske with those from well-known loess-palaeosol sequences in the Middle Dnieper area, at the Vyazivok and Stari Kaydaky sites, which we investigated formerly with a combined palaeomagnetic and rock magnetism approach [150,234,235].…”

“…It contains two middle dark-brown chernozem-like soils, with an underlying sandy layer, and an overlying reddish-brown sandy gleyed soil [162]. We correlate D-S5 (like we did previously at Roksolany) with the Lubny unit corresponding to MIS 13 [235]. Although the referred pedocomplex is well-developed in loess records from northern and central Ukraine, the climate of the Lubny warm stage (represented by chernozems, meadow brown, grey forest and, in lower parts, gleyed soils), is commonly characterized as less warm than that of the Early Zavadivka (expressed by strong rubified brown forest soils) [47,52,55,155,183,284] related to MIS 11 [179].…”