| Composite stratigraphic sequences from four localities along a ca. 700 km long north-south transect between Moscow and Volgograd, Russia have yielded new information as to the timing and history of Quaternary events over the last ca. 800 ka. Lithostratigraphic and pedostratigraphic analyses, supported by physical data, geochemical data, and micromorphological investigations allowed for the development of an allostratigraphic scheme that was used as a tool for correlations spanning significant distances. Optical dating techniques were used to temporally constrain that portion of the allostratigraphic framework younger than ca. 150 ka, whereas the identification of the Brunhes/Matuyama boundary (ca. 780 ka) constrains the oldest portion of the observed loess-paleosol record. The resulting chronostratigraphy (sensu lato) and geochronology allow reinterpretations of the Quaternary evolution of the Russian Plain. Major advantages of the newly proposed stratigraphy include: (1) correlation of the Likhvin Interglacial soil to MIS 9; (2) correlation of the Muchkap Interglacial to MIS 11, and; (3) association of the Don Glacial to MIS 12 rather than its generally accepted association with MIS 16. The latter is a major change to the chronostratigraphic record that significantly alters Middle Pleistocene geologic history and climatic interpretations.; Pedogenic events identified from field observations, laboratory data and micromorphological investigations have yielded evidence of latitudinal bio-climatic shifts. The most auspicious of the warm periods during the last ca. 400 ka was the Muchkap (Holsteinian) Interglacial during which forest-influenced pedogenesis was interpreted at Sebryakova-Mikhailovka ( ca. 50°N), where arid steppe currently prevails. Furthermore, based on pedogenic evidence, most major interglacial events (MIS 11, 9, and 5.5) of the last ca. 400 ka appear to have been warmer and possibly more moist than the present-day climate. (Abstract shortened by UMI.)... |
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