Biostratigraphy of the Upper Pleistocene (Upper Neopleistocene) of the Southern Urals

摘要

This paper is a synthesis of the previously published and unpublished materials dealing with the stratigraphy of the Upper Pleistocene (Upper Neopleistocene according to the Russian stratigraphic scheme) of the Southern Urals. It is the second review about the characteristics of the Pleistocene deposits of the easternmost part of Europe. It follows a previous paper concerning the biostratigraphy of the Late Middle Pleistocene of this region. The deposits which constitue the regional stratigraphic units are characterized. The results of the mammalian, malacological and palynological investigations as well as the radiocarbon data provide the basis for the stratigraphical subdivision and the reconstruction of the palaeoenviron-ments. The main geological and biotical events of the Southern Urals region which took place during Late Pleistocene are characterized in the paper. Erosional processes became active at the beginning of Kushnarenkovo time when uplift took place in the Urals and when the Late Chosarian regression began on the Caspian Sea basin territory. Fluvial deposits can be observed at the base of the second terrace which developed above the floodplain. A soil was formed on the subhorizontal surfaces. Forest-steppe and steppe landscapes characterized this interval. The climate was warm and humid. The Saigatka horizon formed under cold conditions. Slope processes and solifluction were the main relief-forming processes and fluvial erosion processes became weaker. Floodplain sediments accumulated in the river valleys and formed the upper parts of the second terraces above the floodpain which were intensively eroded. The plains were covered by steppe and the mountainous areas were occupied by tundra and forest-tundra landscapes. The next erosional cycle began during the following Tabulda period, because of the lowering of base level of the erosion and increased uplift of the territory. The fluvial sediments now form the lower parts of the first terraces above the floodplain. A soil was formed on the watersheds. Sites contain Late Palaeolithic artifacts. The floral association was close to Southern Uralian flora of the present-day. The climate was moderately warm in the plains and drier and cooler in the mountains. The subsequent Kudashevo event can be correlated with the Late Glacial when the climate became colder. Loess-like sediments and floodplain deposits form the upper parts of the first terrace above the flood-plain and cover the watersheds, where they contain cryogenic structures. The climate was moderately cold. Late Palaeolithic sites attributed to the Kudashevo time are known in the Southern Urals region. The stratigraphical positions of the main Upper Neopleistocene localities of the Southern Urals are discussed. The Southern Urals subdivisions are correlated with the Western European stratigraphical scheme (Eemian-Weichselian interval).