Paleoclimate Changes During Holocene Recorded By Lake Sediment In Central East Inner Mongolia

Inner Mongolia,situated in the marginal region of Asian Monsoon and Westerlies,is sensitive to climate changes.Lots of studies have been carried out here.However,there are still many inconsistencies that need more records with reliable age control and proxy analysis.Therefore,lake sediments from Dali Lake and Haolaihure Paleolake in Central East Inner Mongolia were analyzed.(1)Paleoenvironment reconstructed from Dali Lake sediment and six lake shore profiles shows: the lake fluctuated frequently from Last Deglaciation to Younger Dryas(YD),and declined after the end of YD at ~12.3 cal ka BP;then the lake level raised gradually to 1274 m a.s.l.at ~10.0 cal ka BP,indicating increased precipitation;10.0-6.6 cal ka BP was a high lake level stage with a warm and wet environment,it was a climatic optimum period;6.6-1.0 cal ka BP,the lake level began to decrease,with asimilar lake level with early Holocene at ~4.9-4.6 cal ka BP,indicating a gradually dry condition;after 1.0 cal ka BP,the lake level declined and the environment deteriorated greatly.(2)The environmental evolution process reconstructed from Haolaihure Paleolake shows: the climate was relatively cold and dry in 12.2-8.7 cal ka BP,but improved after YD ended at ~11.3 cal ka BP;8.7-4.6 cal ka BP was a warm and wet period,with a deterioratestage at 7.1-6 cal ka BP but then recovered;the climate was still warm but less humid than previous period in 4.6-3.7 cal ka BP;the climate moderated again in 3.7-2.2 cal ka BP and character with warm wet condition;after 2.2 cal ka BP,the climate deteriorated greatly and the regional environment was cold and dry.(3)It is shown that the regional climate was controlled by Asian Monsoon during early and mid-Holocene,but switch to Westerlies in late Holocene.However,there are some differences on detail.(4)Eight cold dry climate events are recorded by Haolaihure Paleolake at 0.3(LIA),1.3,2.9,4.4,7.9,8.9,9.5 and 11.6 cal ka BP(YD).Six of them could be compared with ice-rift events in North Atlantic,illustrating the interaction are also clear in climate transitional region.