CONICET | Buscador de Institutos y Recursos Humanos

Mountain glaciers are very sensitive to (past) climatechanges. Paleoglaciation of the Tibetan Plateau and the Himalaya receivedplenty of attention for the reconstruction of past climate and environmentalconditions, whereas few studies have been conducted so far in the adjacentAltai and Sayan Mountains in Siberia, although they promise a complex history.The investigated Sayan Mountains in the Russian Altaiindicate extensive glacial activity during the Pleistocene and a shifting ofthe local Last Glacial Maximum (LGM). Rich glacial residues in terms of moraineridges and erratic boulders in the region provide excellent opportunities toestablish a detailed age chronology using in-situ cosmogenic 10Besurface exposure dating and derive information about paleoclimatic conditions.We present 28 10Be surface exposure agesfrom two sites in the western Sayan Mountains, Ergaki Range and Tuva Uplands.Distinct lateral moraines document the extents of former glaciation during a lastglacial maximum. Several recessional moraines in the Ergaki Range additionallyrecord stillstands or readvances during the last glacial termination.The prominent lateral moraine in the Ergaki Rangeyields three exposure ages of ~19 ka indicating a MIS 2 glaciation. One olderage of 27 ka is interpreted as outlier due to inheritance. The maximum advancescorrelate with the end of the global LGM. Concluding, glaciers in the ErgakiRange existed continuously during the late Pleistocene only varying in theirsize. The well clusteredages of the Ergaki Range provide a robust deglaciation chronology. The readvances/standstills consistently date to ~18 ka (three boulders), 17.5 ka (twoboulders), 17 ka (three boulders), and 16 ka (two boulders), with adeglaciation starting after 16 ka. The valley is not high enough to recordyounger, less extensive glaciation, e.g. during the Younger Dryas and theHolocene. Exposure ages from the Tuva Uplands are more difficult to interpret.The lateral moraine documenting the most extensive glaciation yields threeexposure ages of ~22 ka. The immediately adjacent inner lateral moraine has twoslightly younger and stratigraphically consistent ages of ~21 ka, yet threemore boulders from that moraine are ~27, 31 and 43 ka. At this point, wesuspect these older boulders to have inheritance, but we cannot confidentlyexclude a much older deposition age for both moraines. Analyzing othercosmogenic nuclides, such as 26Al and/or in situ 14C mighthelp to more robustly identify inheritance and complex exposure histories.