Middle-Upper Pleistocene bio-climatic and magnetic records of the Northern Black Sea Coastal Area

摘要

Loess-palaeosol sequences are widespread in the northern Black Sea coastal area. Unlike the quasi-continuous loess-palaeosol series in Central Asia and the Loess Plateau of China, the incomplete geological record of loess-palaeosol successions in Europe provokes different stratigraphical interpretations for different sections. Despite a long history of investigation, many uncertainties still remain in the geochronology of the regional stratigraphy. In this study, some of the most representative loess-palaeosol sections of Moldova, the Dniester Republic, Southern Ukraine and Southern Russia were examined. A multidisciplinary approach was used to establish stratigraphical markers. Seven palaeosols/pedocomplexes are distinguished within the Brunhes chron in the loess-palaeosol sequence in the studied area. The position of the Matuyama-Brunhes (M-B) reversal is drawn at the base of the Kolkotova palaeosol complex in the Khadzimus section. The Jaramillo subchron was revealed at the base of the loess formation. This magnetostratigraphic framework is confirmed by biostratigraphical data. Small mammals are valuable, serving as very important evidence for long-distance correlation. Paleopedological data combined with magnetic susceptibility profiles provide additional stratigraphic control for a loess-palaeosol correlation. The results allow us to conclude that the main paleoenvironmental changes occurred ca. 1 Ma ago when lagoon and alluvial sedimentation was replaced by increasing loess accumulaton. During some intervals, erosion or variation in the loess sedimentation rate at different sites are responsible for the variability of the loess-palaeosol alternation. The correlation of the loess-palaeosol succession in the Brunhes chron with marine oxygen isotope stages suggests that the beginning of the loess-palaeosol formation of the Middle Pleistocene was forced by more pronounced long paleoclimatic cycles than are noticed prior to the M-B reversal.