History of Development of Ak-Khol Lake Depression (South-Western Tuva) in Late Pleistocene and Holocene According to Geological, Geomorphological and Archeaological Data
Alpine depressions of the south-eastern Altai and south -western Tuva are the places of concentration of a large number of archeological sites from Paleolithic to the Mongol empire. The existence of the archeological cultures in these depressions was directly related to the climate-dependent evolution of a hydrological system in Pleistocene and Holocene. A correlation of the results of geological and geomorphological studies with a mapping of archeological features in the Ak-Khol Lake depression (south-western Tuva) was carried out in this work. In Late Pleistocene a peak watermark of a ice-dammed lake reached here 2380 m below the sea-level that is180 m above the present level. Radiocarbon dating of the buried soils showed that the lakes, dammed initially by the glacier, then by moraine, were lowered more than 2220 m below the sea-level long before 8.5 thousand years ago. After a break of a moraine dam, fluctuations of the lake level were determined by the climatic changes. All archeological sites mapped in the depression and dated from the Late Bronze Age to the Turkic time are disposed above 2220 m below the sea-level. This one, as well as the absence of erosion traces, testify that during the last 3 thousand years the lake level did not rise above this watermark. These conditions determined the development of the basement of the Ak- Khole Lake alpine depression by nomadic peoples.
Keywords: Southwestern Tuva, Ak-Khol lake alpine depression, dammed lakes, late Pleistocene - Holocene, mapping of archeological features, geological and geomorphological studies, radiocarbon dating, paleohydrological reconstructions.