Changes in Chany lake and surrounding landscape in the second half of Holocene

Chany Lake is one of the most large in Russia. It is situated in the narrow area where three natural zones shifted. Consequently, it is the unique natural record of changes in environmental conditions. The square of the lake has changes from 15,000 to 1,500 km 2 for the two centuries of observations. Mode of water level fluctuation stays within every 30-40 years. The time, when Chany lake appeared, associates with the end of glacial period around 12,000 years ago, and Early Holocene deposits are absent in consequence of drying up in Holocene optimum and erosion. But detailed history of lake origin and development is unknown. We carried out the complex study of the drill sample of Chany Lake bed deposits (Yarkovo stretch) by such methods as radiocarbon dating, sedimentological analysis, palynological, chironomid and diatomic analysis. It allow to reconstruct the stages of lake development, depositional condition, landscape development and climatic changes more completely. It was established that Yarkovo stretch had originated as the shallow boggy oligotrophic basin around 10,000 ya. But conditions had changed around 3,600 ya: the lake had become the shallow light-salted eutrophic water body with high percentage of macrophythes. During the 3,600-3,400 ya, the lake was surrounded by pine forest; climate was slightly cooler then modern. The birch outliers have spread since 3,400 ya. After 2,000 ya, the lake became deeper. The forest-steppe with extensive birch outliers have spread and lake have been shallow, eutrophic, light-salted in the period of 1,000-500 ya. But after 500 ya the depth and salinity had increased, the climate had become cooler, the steppe meadows have spread around the lake, reflected the modern steppification.