VEGETATION AND LAKE LEVELS IN NORTHERN MONGOLIA IN THE LAST 12 500 YEARS AS INDICATED BY DATA OF POLLEN AND DIATOM ANALYSES

Abstract

Bottom deposits of the Dood Nuur (51°20′ N, 99°23′ E), Hovsgol Nuur (50°32′ 101°10′ E), and Gun Nuur (50°15′ N, 106°36′ E) lakes of northern Mongolia are analyzed and discussed. Data of pollen and diatom analyses are used to reconstruct changes in terrestrial vegetation, the chronological succession of which throughout the last 12 500 years is inferred on the basis of the radiocarbon dating. Taiga forests consisting of spruce, larch, pine, and birch species were widespread in the Darhat basin 12300-12500 years ago. A degradation of arboreal vegetation and growing abundance of steppe coenoses took place 10 600-12 200 years ago. The larch-birch-pine forests became dominant again in the Darhat and Hovsgol basins during the Holocene. In the Orhon-Selenga basin, forest coenoses considerably decreased in area 8700-9600 years ago. The pinelarch forests spread over the region to the maximum during the last 8000 years. The lake levels were variable, and these changes did not coincide in the mountain (the Hovsgol and Dood Nuur lakes) and plain regions (the Gun Nuur Lake). The lake level in the first region was low in the middle Holocene (5400-6500 years ago), when the Gun Nuur Lake was at the transgression stage.