The Rodionovo section. In 2002 we studied the 350 cm thick interglacial peat exposed in a section located on the left bank of the Pechora River, 5-6 km downstream from Rodionovo village, Komi Republic. The fen peat layer, sandwiched between two Middle Pleistocene tills, extends over 20 m along the Pechora River. The black, plastic, laminated and strongly compacted peat was frozen in the middle of the unit.

53 pollen samples have been taken in 10 cm intervals starting from the clay beneath the peat and toward the base of the upper till. Five local pollen assemblage zones (LPAZ) were indentified in the diagram. The pollen spectra reflect predominance of birch-spruce forest with the admixture of fir, pine and deciduous trees (elm, oak, hornbeam) indicative of the upper climatic optimum of an interglacial. The abundance of pollen grains of spruce, presence of fir and deciduous trees, as well as Osmunda spores supports such a conclusion. The lower climatic optimum of this sequence was discovered by Duryagina and Ponomarenko (1993) in the clay with plant remains lying beneath the peat. The pollen spectra of this layer reflect the dominance of spruce-birch forest with an admixture of Abies and deciduous trees.

²³⁰Th/U dates of the Rodionovo peat. We used "total dissolution" technique for extraction of U and Th from peat samples. The topmost and basal layers (50 cm thick each) show a higher uranium content. These layers act as geochemical barriers for U and Th. The middle part of the peat layer contains a minimum amount of uranium (0.4-0.5 ppm/g organic sample) and is considered to be an almost closed system for U and Th. Applying the isochron plot and the TSD technique we have obtained the "isochron-corrected" ²³⁰Th/U date of 249.6 + 15.7/-10.8 kyr (9 samples, depths 128-198 cm). This age correlates with MIS 7 (186-242 kyr; Bassinet et al, 1994). The Rodionovo interglacial sequence is younger then the Likhvin (Holstein) interglacial sediments in the Bolshaya Kosha section. Additional data are necessary to support this conclusion.

The work was supported by the INT AS (project N 01-0675).

Reference:

Arslanov Kh. A., MaksimovF.E., Kuznetsov V.Yu., ChernovS.B., Velichkevich F.Yu., Razina V.V., Savelieva L.A., Baranova N.G. ²³⁰Th/U isochron dating and paleobotanical study of the Middle Pleistocene interglacial section Rodionovo, northeastern European Russia. Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 12.