Vegetation And Climate Changed During 13,980～4820 Cal. Yr BP In Huitengxile Area Of Inner Mongolia, A Multiple Indicator Investigation Of Lake Sediment Of HTL

A 648-cm-long core of HTL01 were studied in Huitengxile area of Mountain Daqing, Inner Mongolia, China. Based on 13 AMS 14C dates, pollen, grain size and LOI proxies records, detailed vegetation and climate changes during 13,980-4820 cal. yr BP were reconstructed. Furthermore, regional published Holocene climate data were reviewed and analyzed to discuss the possible temporal and spatial patterns of Holocene climate changes throughout the monsoon marginal zone and associated dynamics. The primary recognition and conclusions are as follows:1. A reliable age-depth model was established consulting Bayesian method, through scientific evaluation of the lake reservoir effects by 15 AMS 14C from 13 layers. The age rang of the HTL01 core is between 13,980 and 4820 cal. yr BP.2. The vegetation and climate changes during 13,980～4820 cal. yr BP in Huitengxile area were reconstructed based on the pollen record and reliable chronology. Between 13,980 and 13,830 cal. yr BP, vegetation type of study area was alpine cold desert, the climate was very cold and dry. Between 13,830 and 11,840 cal. yr BP, subalpine meadow expanded, the HTL was Aeolian or alluvial environment, the climate was better than before, but overall still very cold and dry. During 12,390～11,840 cal. yr BP, mountain meadow was expended and Betula in valley of peripheral regions degenerated suggesting a very cold and dry climate. Between 11,840 and 9820 cal. yr BP, mountain meadow steppe continued expend, Betalu and Ulmus increased in number, thus suggesting the climate became warmer and wetter. During 10,490-9820 cal. yr BP Ulmus’s degeneration suggesting temperature declined. Between 9820-5600 cal. yr BP, vegetation changed to grassland with sparse forest, vegetation type was Betula-Ulmus-Quercus broadleaf forest steppe in prophase, coniferous Pinus expended later period and broadleaf-coniferous forest steppe in final phase, indicating the climate was warm and wet.5600-4820 cal. yr BP, broadleaf-coniferous forest steppe degenerated and turned into meadow steppe, the climate became cool and dryer.3. The vegetation and climate changed reconstructed by pollen were supported by the grain size and LOI records. In the Last deglacial vegetation was not developed because organic matter content was at very low level, precipitation was seldom because the content of clay and sand were low and the carbonate content was very high. Since Holocene, the these indicators had a great changed, organic matter content, clay and sand content increased and carbonate content decreased suggesting vegetation was better, the lake expanded and precipitation was increased, the climate was warm and wet and during 7030-5600 cal. yr BP was warmest and wettest. From 5600 cal. yr BP, the climate became colder and dryer.4. The climate cooling events in HTL01core recorded by LOI index record is similar to δ18O of Greenland ice core and hermatite-stained grains of North Atlantic sediments. The contact mechanism between them is worthy of further investigation.