NEWLY PROPOSED ALLOSTRATIGRAPHY FOR QUATERNARY SEDIMENTS OF THE RUSSIAN PLAIN: CHRONOLOGIC AND CLIMATIC IMPLICATIONS

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 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. Paleosols present within the studied composite sections represent periods of attenuated sedimentation and hence, define seven depositional megacycles (glacial-interglacial periods) over the past ca. 800 ka. A major unconformity below the Don Till (MIS 12) within the fourth megacycle (from the present day) is believed to represent a ca. 180 ka hiatus. Correlations of these results to other records within and outside the Russian Plain region help to corroborate the newly developed stratigraphy. The teleconnection between magnetic susceptibility at Sebryakova-Mikhailovka and the orbitally tuned grain size rations of the Baoji section (China) suggest that the all-time Pleistocene European glacial maximum and Asian maximum desert expansion are correlative. Eurasian-scale relationships such as this will provide new insight to climate modelers in order to understand climate-forcing mechanisms at hemispheric scales.