Pollen Assemblage Features And Environmental Significance Of Lop Nor Sediments Between Late Pleistocene And Early Holocene

Lop Nur is located in the southeast of Xinjiang,China.It is one of the driest places in the world.The environmental change in Lop Nur is the representative of the ancient climate and environment change of the mountainous region of Tarim Basin and its surroundings.Therefore,research on climate and environment change in this area is very valuable for researches on Global Change,ecological environment preservation and resources development and utilization of the drought desert area.This article studied the TDP₃ section of the Lop Nur,based on the AMS14 C of sediments of section,With the help of statistical methods6.9¹3.5ka cal.a B.P.climate and environment change sequence of the Lop Nur is established,according to the pollen assemblage features of the sediment of the Late Pleistocene epoch.The following conclusions are obtained:?1?The climate and environment of TDP₃?0-2.2m?section change sequence is established: 6.9¹3.5ka cal.a B.P..?2?The results of PCA?Principal Componen Analysis?showed that : The first principal component may be the humidity of region;The second principal component may be altitude;The third principal component may be the light of the sun;The fourth principal components may be the humidity of local.?3?The pollen assemblages in the Lop Nur region were characterized by the herbaceous pollen whose percentage is up to 93.6% with Atemisia and Chenopodiaceae as the dominant pollen types since late Pleistocene;the second common group is the gramineae pollen;the woody pollen is relatively spare and its percentage is below 13.4% with ephedra ? picea ? nitraria as the dominant pollen types;the percentage of fern spores is less than1.26%.The plant types in the region had few changes since late Pleistocene.?4?according to the pollen assemblage features,Climatic and environmental evolution sequence are reconstruced as follows: As a whole,the background of the drought does not change,there are a series of changes in temperature and humidity based on the background of the drought.Stage of evolution be divided into three: 13.5¹1.3ka cal.a B.P.was a arid period,and the trend became stronger with the time;11.3⁸.3kacal.a B.P.was a warm-humid period,and the trendbecame more arid;8.3⁶.9kacal.a B.P.was a warm-humid period,though obviously weaker than in the period of 11.3⁸.3kacal.a B.P..Based on the pollen assemblage features,the waves of cold and warm,dry and moist mode in the area of the Lop Nur in the period of 6.9¹3.5ka cal.a B.P.are shown.The establishment of the environment change sequence makes the achievement of the climate and environment change study of the middle of the late Pleistocene of the Lop Nur,which provides some basis for forecasting in this area the extreme climate conditions and unexpected environmental events that may occur in future hundreds and thousands of years.