Home – Home – Jornals – Avtometriya 2005 number 2

Modern conceptions of the evolution of cryogenic area of West Siberia during the last 5 million years are formulated on the basis of paleogeocryological interpretation of the unique paleoclimatic chronicles obtained by a large group of scientists for southern regions of West Siberia and the Siberian Platform as well as on the careful examination of recent publications on the changes of climatic and geocryological conditions during the last 800 000 years. It has been ascertained for the first time that the perennial rock freezing and the formation of the cryogenic strata in West Siberia began 3.1 million years ago. Three cryogenic epochs have been revealed in the range of 3.1-3.0 million years ago. The first epoch (3.10-3.08 million years ago) was the least cold and the shortest. The second epoch (2.82-2.47 million years ago) was remarkable for extremely severe geocryological conditions in cryochrons and severe condition in thermochrons. Consequently the cryogenic strata had been existing steadily for more than 350 000 years. The third epoch (1.92-0.00 million years ago) was notable for the multiple alternation of the aggradational (cryochrons) and degradational (thermochrons) epochs. During only the last 800 000 years 21 cryochrons and 20 thermochrons have been marked out, which differed in duration (from 2 to 60 thousand years) and in heat supply of climate. In the Early and Middle Neopleistocene 11 cryochrons has been revealed during which the rock temperature fell by 8-12