Saturday, 15 July 2006

Paleosols and Pedosediments of the Early-Middle Pleistocene Red Sediments (Scythian clays) of the Southern Russian Platform.

Svyatoslav A. Inozemtsev, Moscow State Univ, Dept of Soil Science, Leninskie Gory, Moscow, Russia and Andrey E. Dodonov, Geological Institute, RAS, Pyzhevskii per.7, Moscow, Russia.

Paleosols formed at the Early-Middle Pleistocene transition carry information about landscape development during the transition from the warm (non—glacial) to cold (glacial) biosphere. Scythian clays is a formation of the continental red-colored, carbonate loamy and clayey sediments, widely spread on the south of the Russian Platform. We studied paleosols and pedosediments from the Scythian clay formation in a number of geological sites: low Don valley (exposures Sarkel and Nagavskaya), middle part of Kuban valley (Temijbeckskaya), low part of Laba valley (Novolabinskaya). The paleosol profiles are 70-130 cm thick, with the set of horizons B1kg – B2k – BCk (A horizon is absent). Paleosols have brown or mottled color, loamy clay to clayey texture, subangular blocky – prismatic structure. They have various pedofeatures: well developed stress cutans and abundant neoformed carbonates; ferruginous neoformations are concentrated in the upper part of paleosol profiles. Neoformed carbonates are presented by concretions and clay-carbonate nodules. Ferruginous pedofeatures are presented by mottles and rusty-yellow nodules. The following pedogenetic processes took part in the paleosol formation: aggregation, migration and precipitation of carbonates, gleyzation, vertic processes. The main tendency in the development of Scythian clays is the gradual transition from sub-aquatic to sub-aeral conditions of sedimentation. Within the set of the studied geological cuts we observed the transition from the pedosediments on the early stages of formation of Scythian clays (site Nagavskaya) to polycyclic pedocomplexes with differentiated soil profiles on the later stages (sites Temijbeckskaya and Novolabinskaya). This reflects slowing down of sedimentation and increase of duration and intensity of pedogenesis. Thus, in the south of the Russian Plate there is a detailed pedogenic record of the last transition from the warm paleoclimates to the cold ones.

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