Late Quaternary Sedimentary and Paleo-Enviroment of Jing Peng Palaeo-Lake,Hexigten,Inner Monglia
Palaeo-JingPeng lake,which has been got great attention of scholars at home and abroad,located in Inner Mongolia Hexigten,nearby the arid and semi-arid and sub-humid climatic boundary,and sits on the converging place of such three great morphologic regions as the Greater Hinggan,Yanshan Mountains and Otindag sandy land.Based on field measurement on typical sedimentary section,and chronostratigraphic framework created by OSL,this paper discussed the formation and evolution of palaeo-Lake.And by using analysis on the environmental proxies,Late Quaternary lake evolution and paleoclimate changes were recovered.The study shows that:1、According to detailed geomorphology and sedimentology research in field,this dissertation found more evidence for the existence of the palaeo-lake,and found its highest level can up to 1320 m.2、Age data measured before and previous materials showed that lake basins formed successively in Early Pleistocene,and to middle Pleistocene all basins were filled with water to be lakes,To Qp2-2 and Qp2-3,A local high lake was formed in these basins which located in the east of watershed,and the lake interconnected as beaded distribution;to the late Pleistocene,the lake reaches its peak developmental stage,which crossed the watershed and Covered the entire region,all lakes interconnected together as one to form a super palaeo-lake;since the end of Pleistocene,tectonic activity became intense,lakes ebbed away,rivers were incised strongly to be canyon shape valleys,and some small lakes were left in part of these basins,Since Holocene,strong tectonic activity and cold weather cause lakes shrinked and the rivers into being incised continuously,which formed the water system and surface landscape we can see today.In addition,the lake appeared high level during Qp2-2、Qp2-3 in local area as well as a super palaeolake was formed in Qp3-3,which corresponded to the MIS5 and the MIS3 high Lake level stage of Inner Mongolia Plateau.3、Based on Sedimentary characteristics,particle size characteristics,magnetic susceptibility,element geochemical analysis and pollen analysis of Fushenghao section,and combined with the chronostratigraphic framework,the development of study area’s Paleoclimate since 33.68 ka B.P.can be divided into three major phases:warm and humid climate stage(33.68-26.24 ka B.P.),cold and dry climate phase(14.14-26.24 ka B.P.)and warm and humid climate phase(14.14-8.37ka B.P.).4、Compared the Fushenghao section with the surrounding area such as Xingkai lake and Daihai,and Connected the oxygen isotope records of the deep-sea sediments,the Greenland ice core,Hulu Cave,it could be found that since 33.68ka BP the climate change trend of Fushenghao section was generally consistent with others,which indicated that the study area’s climate change was influenced by global climate change,at least affected by the climate change of northern hemisphere,and the palaeo-lake recorded global or hemispheric scale climate signals.