Four climatholiths of the Upper Pleistocene are used in Siberia as regional stratigraphic horizons: Kazantsevo, Zyrjanka, Karginsky, and Sartan. Their geochronological basis is discussed in this paper. A conclusion is made that they are erroneously correlated in the official stratigraphie scheme. New detailed data obtained by international teams on key sections of Arctic Siberia suggest an alternative division of the Upper Pleistocene. A new version of chronostratigraphic scheme of West Siberia is proposed for discussion. The new scheme for the lower Upper Pleistocene is based on well-known key sections of the Karginsky and Zyrjanka Horizons. The main thermomer of the Upper Pleistocene is represented by the Malaya Kheta and Karginsky strata with geochronometric marks corresponding to early marine isotope stage 5. The complex of the last glaciation (Zyrjanka Horizon) is dated within a broad interval from 100 to 50 kyr BP. Two new horizons with stratotypes on the Yamal Peninsula are proposed for the second half of the Upper Pleistocene. These are the cold Var'yakha interstadial about 50-30 kyr BP and the Syoakha cryomer 30-11 kyr BP. The new horizons are in good paleoclimatic correspondence with the Middle and Late Pleniglacial of Europe.