Holocene Environmental Changes Of Gun Nuur In The Northern Mongolian Plateau

The Mongolian Plateau, located in the arid and Semi-arid area and sensitive to climate and environment changes, is basically under the influences of three global-scale climate systems: East Asian winter monsoon, East Asian summer monsoon .westerlies. So Mongolian Plateau might have been important in recording the Holocene global climatic events. This thesis focuses on one lacustrine sediment in the Mongolian Plateau in attempt to provide more regional Holocene climatic information based on AMS-constrained multi-proxy chrono-sequences obtained from Gun Nuur lake core. The multi-proxy includes carbonate content, total carbon (TOC), C/N ratio, grain size, magnetic susceptibility, stable carbon isotope of organic matters and stable oxygen isotopes of carbonates. The following is a brief summary of our reconstructed Holocene climatic and environmental history of the study area.1. The multi-proxy records from the Gun nuur lake core suggest four stages of climate changes: (1) cold conditions sustained till 8.3¹⁴C ka BP, (2) wanning climate with increasing humidity occurred in 8.3-6.3 ¹⁴C ka BP, (3) warm and humid climate dominated during the period of 6.3-2.0 ¹⁴C ka BP., and (4) the climate became cooler since 2.0 ¹⁴C ka BP.2. The multi-proxy records from the Gun nuur lake core indicate the of Holocene in Northern Mongolia Plateau is from 8.3 ¹⁴C ka BP and the climate during the interval of the last glacial stage and the Holocene is characteristic by higher temperature, more precipitation, increased vegetation coverage, and the climate and environment of Gun nuur lake area had been improved.3. The Holocene Climatic Optimum is during 6.3².0 ¹⁴C ka BP,which the climate has been warmer and more humid, the multi-proxy records from theGun Nuur lake core documented five sub-stages of climatic fluctuations. Three great precipitation events are found during 6.3—5.7ka B.Pf 5.0³.7ka B.P. and 2.6².0ka B.P. periods, among which the maximum one is during 5.0³.7ka B.P.4. The Holocene climate and environmental change records retrieved both from lacustrine sediments in the Mongolian Plateau are generally consistent of the lower boundary of the Holocene and temperature drop event in Northern Mongolia Plateau during 2.0 ka B.P. But the Holocene Climatic Optimum last long time, which is the multi-proxy records of the Gun nuur lake core suggested.