After a long discussion of geological and paleobotanical data, TL-date 130±31 kyr, and PM-dating the Gornaya Subbota peat was accepted as one of key sections of the Kazantsevo Horizon (Arkhipov, 1997). The Chembakchino section contains a peat lens which is U/Th-dated to 114.2 kyr (leachate technique, L/L) and 110.1 kyr (sample dissolution technique, TSD); the Shuryshkary section is dated to 133 kyr (L/L) and 141.1 kyr BP (TSD) (Astakhov et al, 2005); and the Bedoba section has yielded the dates 126.6 kyr (L/L) and 146.5 kyr BP (TSD). The confidence intervals are discussed in this report. Both adding and subtracting (±) of the dates error bars will bring the peat deposits beyond the interglacial interval. However, glacial environments are impossible on account of interglacial nature of macro- and microflora, stratigraphic position of layers with these floras, and other geological data.

All the sections are located in boreal forest. Shuryshkary is situated in the north of the northern taiga subzone along the Ob River (65°55' N, 65°30' E). Gornaya Subbota (59°50' N, 69°55' E) and Chembakchino (60°52' N, 69°48' E) belong to the core of the middle taiga subzone along the lower Irtysh River. Bedoba section on the Angara River (58°47' N, 97°30' E) is in the south of the middle taiga. The latter section, though far east from the Ob River, provides important paleobotanical evidence for comparisons.

All four peat deposits contain rich macro- and microflora studied in detail, but only partially published (Nikitin, 1970; Velichkevich et al, 2004; Volkova, 1966; Arkhipov and Volkova, 1994; Gurtovaya and Krivonogov, 1988, etc.). Comparison of the Bedoba and Gornaya Subbota macrofloras has shown that they contain as many as 50% of common genera, and the difference between them is explained by more easterly location of Bedoba (28° farther to the east). Presence of Azolla interglacialis in both floras is significant. Reconstructions for Gornaya Subbota based on the macroflora show mixed forests with predominance of birch and, from pollen data, the Abies-Picea-Pinus sibirica southern taiga with admixture of deciduous trees. The macroflora based reconstructions at Bedoba show mixed forest of Abies-Betula-Picea, and by pollen data there was a southern taiga with admixture of deciduous plants. In Chembakchino the paludinal macroflora is not impressive, but at the base of the peat there are remains of a birch-spruce forest. The pollen spectra are typical for southern spruce taiga (at the base), Pinus sibirica forest with Abies and deciduous trees (higher up), birch forest (farther to the top) and middle taiga forest of spruce and Siberian pine (at the very top). Vegetation of the Bedoba and Gornaya Subbota sections reflects an optimum and some preceding stages (in Bedoba, three optima are observed), and in Chembakchino there are an optimum and final stages of the interglacial. Shuryshkary is located 6° to the north from Gornaya Subbota, but their macrofloras contain 50% of common taxa. Both peat deposits contain Azolla iterglacialis, but in Shuryshkary also Betula папа, Selaginella selaginoides and other cold-resisting plants have been found. The macroflora based reconstruction for Shuryshkary suggests the northern taiga subzone (Nikitin, 1970), but pollen rather indicate southern taiga with admixture of deciduous plants (Astakhov et al., 2005).

Reference:

Laukhin S.A., Arslanov Kh.A., Maksimov F.E., Kuznetsov V.Yu., Nikonorov Ya.A., Chernov S.B., Tertychnaya T.V. New data on geochronology and paleovegetation of the Kazantsevo time on the lower stretch of the Ob' and Irtysh rivers . Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 52.