U-Th dating has been used to estimate growth periods of the speleothems in the caves of South Siberia and Mongolia, corresponding to themochrons over the last 500 000 years, with their intervals indicative of formation of perennially frozen strata in Siberia during cryochrons and of desert invasion in Mongolia.
The caves of the southern geocryological zone are notable for the multiple alternation of thermochrons and cryochrons, and the northern part of the zone has shown no speleothems younger than 400 000 years old, thus implying a long continuous existence of cryochron.
The growth-period dates correspond to those obtained in the paleoclimate studies involving marine isotope stages (MIS 1-11) and paleoclimate record in the bottom sediments of Lake Baikal and suggest a relationship between global temperature and permafrost existence.
The comparison between the data obtained in this study and PWP SST (Sea Surface Temperatures of the Pacific Warm Pool) has shown that 0.5° 1.0°C rise in global temperature in contrast to the pre-industrial period of the late Holocene can only lead to degradation of discontinuous permafrost in South Siberia and to degradation of Gobi Desert, and ~1.5°C rise, to the level of MIS-11, can lead to significant permafrost degradation to latitude 60° N and to the occurrence of wet conditions in Gobi Desert.
Vaks, A., Gutareva, O. S., Breitenbach, S. F. M. Avirmed, E., Mason, A. J., Thomas, A. L., Osinzev, A. V., Kononov, A. M., Henderson, G. M. Speleothems Reveal 500,000-Year History of Siberian Permafrost // Science. 2013. 340, 6129, pp. 183-186.