Pleistocene permafrost in Western Transbaikalia

Progressive cooling of the Pleistocene climate led to the formation of perm afrost in the southern part of Eastern Siberia, in particular, in low mount ains and valley floors of the Transbaikal area. It was thought that in West ern Transbaikalia the permafrost first appeared in the Middle Pleistocene a nd was related to the maximum - Riss (Samarovo) - glaciation (Ravsky et al. , 1964. Anthropogene Deposits of the Southern East Siberia. Nauka Press, Mo scow, p. 105 (in Russian), Bazarov, D.B., 1968. The Quaternary Deposits and the Main Stages of the Selenginskoye Midland Development. Ulan-Ude, p. 166 tin Russian); and others). Earlier investigators found evidence of two col d stages in the Tologoi key section (Alesandrova, L.P., Vangengeim, E.A., G erbova, V.G., Golubeva, L.V., Ravsky, E.I., 1963. New data on the Anthropog ene deposits of the Tologoi section (Western Transbaikalia). Quaternary Com mission of the USSR, Bulletin 28, 84-101 (in Russian); Bazarov, 1968). New research in this area, in particular, at the Tologoi key section, resulted in the discovery of cryogenic deformation levels which were older than thos e previously described. They are found below the Brunhes/Matuyama boundary, although above the Jaramillo event of normal magnetization between 0.78 an d 0.99 Ma BP. Eight levels of cryogenic deformations have been established in the Tologoi key sections, with three dated to the Early Pleistocene and five to the Middle Pleistocene. In total, in the Transbaikal area, not less than 10 levels of Pleistocene cryogenic deformations are recognized at the present time. (C) 2000 Published by Elsevier Science Ltd and INQUA. All ri ghts reserved.