QUATERNARY GLACIAL SEQUENCES IN MONGOLIA – EVIDENCE OF CLIMATIC ASYNCHRONY

Late Pleistocene and early Holocene glacial advances are well documented in the high mountain ranges of Asia. In central Asia, these advances are roughly correlated to dates from moraines and lake cores in the Himalayas, Karakorum, and Tian Shan. Such a long distance correlation is a poor substitute for absolute ages on moraines in central Asia - as Mongolia and other central Asian countries receive most precipitable water from ambient westerly flow off the North Atlantic Ocean and across Eurasia, not from monsoonal rains derived from tropical sources to the south. In order to further constrain late Pleistocene and early Holocene climate in Mongolia, in-situ 10-Be samples were collected from granitic boulders on terminal and prominent recessional moraines in the Hangay and Altai ranges, and the Lake Hovsgol region between 2008 and 2012. The weighted mean age (n=18) of recessional moraines exhibits two peaks, one at 12.5 ± 1 and a second at 15.5 ± 1 ka. Last Glacial Maximum terminal moraine ages (n=17) exhibit 4 individual weighted mean peaks of 17 ± 1, 22 ± 1, 26 ± 1, and 36 ± 2 ka, respectively. Differences in the timing of late Quaternary glacial equilibrium, as recorded in the spatio-temporal position of moraine sequences both within Mongolia and across central Asia, likely reflects inherent variability and complexity in moisture source and amount during colder intervals in this intracontinental setting.