Reconstructed Holocene Climate Change Based On Geochemical Records Of The Lacustrine Sediment Core (HTL2) From Inner Mongolia,China

There have been some questions on the forcing and regional variability of EASM precipitation.It's important to reconstruct Holocene climate change with high quality because it can help to understand spatial and temporal patterns of Holocene climate change and associated dynamics.In this paper,we investigate the total carbonate content?TOC?,total nitrogen?TN?,carbon isotope composition(?¹³C),grain size and iron oxide?Gt/Hm?records with high resolution from HTL2 Lake in the Inner Mongolia to illustrate the climate change during 13,000²50 cal.yr BP,and explore the hydroclimatic changes and the mechanism of climate changes by comparing with the proxy-inferred palaeoclimate time series.The results are as following:?1?On the base of 10 AMS¹⁴C dates,the Bacon Bayesian model provides support of calibrated age and depth for HTL02 core.Supported by this age model,we use organic,lithology,grain size and iron oxide records to reconstruct the environment and climate change during 13,000²50 cal.yr BP.During 13,000¹1,500 cal.yr BP,the large grain size and poorly sorted sediment of HTL2 core indicate an alluvial or fluvial deposit environment with low lake level.The low TOC suggests poor vegetation under dry climate.The low values of?¹³C and high Gt/Hm reflect a cold climate.During 11,500⁸000 cal.yr BP,the small mean grain size and high sorted coefficient reflect a lake environment.The increase of TOC reflects a vegetation amerolition under regional wetting climate.The increase of?¹³C and decrease of Gt/Hm reflect the increase of temperature.During the middle Holocene?8000⁶000cal.yr BP?,the increase of mean grain size and poor sorted sediment reflect a drastic increasing in hydroconditions in realtion with increasing precipitation though the strata data indicate a reduced water table.The increasing TOC also indicatethe wettest climate of the Holocene,corresponding to the high temperature reflected by low Gt/Hm and high?¹³C.During 6000³400 cal.yr BP,the decrease of TOC reflect the decrease of precipitation,which means the environment is not suitable for the development of vegetation.The increasing Gt/Hm and decreasing?¹³C reflect the cold environment at this stage.During 3400²50 cal.yr BP,the decreasing of TOC reflects the low primary productivity of the lake and/or the poor vegetationin the watershed.The increasing of?¹³C values reflect a higher temperature which is also reflected by the decreasing Gt/Hm.?2?The dry climateduring the early Holocenemay be induced by the still high latitude ice sheet residuals and low atmospheric CO₂ concentration.During the middle Holocene?8000⁶000 cal.yr BP?,the solar radiation in the northern hemisphere was high in summer,the AO/NAO was more positive,the ENSO was more negative and the surface water temperature in the western equatorial Pacific increased,resulting in the strengthening of the western Pacific subtropical high and enhanced the heat between the sea and land.The drying climate of the late Holocene may be a direct response to the decreasing of procession-induced NH summer insolation.?3?The YD,11.1,10.3,8.2 and 5.9 kyr events were clearly recorded by TOC of the HTL2 core.Of them,the YD can be correlated with records of northern China and Northern Hemisphere,suggest a global or continental significance.