Geographical structure of the territory is formed during the long geological history and contains relic, progressive and conservative elements of different age. Present environments in the north of West Siberia is a complex mosaic of forest, bog, tundra, lake, terrace, flood plain geosystems, morainic complexes, fragments of sea terraces and aeolian formations.

The aeolian system was formed in the Late Pleistocene (Zemtsov, 1976), mainly during dry parts of the 1850 year rhythm. The sand sources were ancient dunes with old forests, deflated lakes with sandy floors and young terraces with unstable vegetable cover. Stratigraphic data in the Pur river valley allow to distinguish 5-6 stages of the development of aeolian processes. Presently a new stage is probably in the bud. It is stimulated by the aridification tendency on the one hand and by antropogenic influence on the other hand. The processes of the forest recuperation and bog development slow down in dry years and are halted in epochs of the meridian circulation. So the environment keeps a potential for large-scale aeolian activity. Sections studied by the authors suggest seven relatively cool intervals separated by warmer intervals. The cool intervals in their terminal dry phases ended with activation of aeolian processes.

Seven humid intervals with culminations at 11 850, 10 000, 8 150, 6 300, 4 450, 2 600 and 750 years ago have been known (Maksimov, 2005). One of the earliest humid interval (14,220 yrs BP, SOAN-5667) has been characterized by integrated analysis of paleocarpologic and palynologic information. In this analysis we took into account that succession processes are faster in low moist terrains than on watersheds. The lowermost peat sample between two sand formations shows arboreal pollen as 71.1%, herbs 37.4%, spores 7.2% with poorly developed or emaciated grains of pine pollen. In the uppermost sample arboreal pollen is 55.4%, herbaceous 25% and spores 3.9%. Redeposited grains of Pinus Haploxylon, Apiaceae are characteristic. Rare pollen grains of deciduous plants occur at the background of numerous sedges. This period was probably transitive from warmer and drier to a cooler and more humid environment. A growing diversity of herbaceous species is noted by carpological analysis. Only one scale of birch relates to the arboreal assemblage but there are species typical for boreal forest, tundra, bogs and oxbow lakes. Some discrepancies between the two sets of factual data are intrinsic for the two methods.

The succession of palaeogeographic events to a large extent agrees with the rhythmic model of the Holocene by Maximov (1972). The ideal rhythmic cause, being the basis of environmental change in the area, is greatly modified by regional factors, such as cooling influence of the ocean, ice sheets, permafrost, relict moisture, and by the position of the region within the continental sector of Eurasia, by peculiarities of circulation and tectonic processes, availabilty of local refugia (southern slopes of the Sibirskye Uvaly with their barrier effect, the Lower Yenissei Upland).

Reference:

Micharevich M.V., Baryshnikova O.N., Nenasheva G.I. Integrated environmental studies in the West Siberian north as related to the problems of paleogeographic correlations. Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 64.