PALEOENVIRONMENTAL INTERPRETATIONS OF THE KARGINIAN (MID-WISCONSIN) INSECT FAUNAS FROM THE CENTRAL PART OF WESTERN SIBERIA AND ADJACENT AREAS

The end of the Karginian (Mid-Wisconsin) interglacial is characterized by gradual cooling and drying of climate. According to paleobotanical data (Arkhipov, Volkova, 1994), at that time forest-tundra covered the northern part of Western Siberia, while dry forest-steppe predominated in its central part. Entomological data have been obtained at three sites from the central part of West-Siberian plain located at maximum distance of 344 km from each other between the eastern slope of the Ural Mts and latitudinal part of the Irtysh river. The site Nikitino (57°34' N, 63°17'E) is dated 28,460±800 and 24,480±580 years BP, age of Nizhnyaya Tavda (57°41' N, 66°12' E) is 27,400±335 years, and of Skorodum (57°47' N, 70°58' E) is 26,500±550. Insect faunas found there consist of species that at present never occur together. They include arctic (Pterostichus pinguedineus, Curtonotus alpinus), boreal (Notiophilus reitteri) and subboreal (Pogonus spp., Stephanocleonus spp.) species, as well as Poecilus ravus inhabiting steppes to the south-east of Baikal Lake and in Mongolia, and Cymindis mannerheimi living in mountains of Northern Tyan-Shan. The faunas have been determined as “extinct”, but composed of extant species. It was hardly possible to determine temperature characteristics of the environment, because temperature intervals of these species (counted on the bases of the coldest and the warmest months) do not overlap. I suggest that these faunas existed in cool and dry climate (T_max +15°C, T_min –25°C, precipitation not more than 400 mm per year) with numerous warm local habitats. The obtained data have been compared with the results of carpological analysis that showed both arboreal and herbaceous xerophilous vegetation.