END-MEMBER CHARACTERISTICS OF GRAIN SIZE OF THE SANDY SEDIMENTS IN LIAODONG PENINSULA AND PALEOENVIRONMENTAL EVOLUTION OF THE LAST INTERGLACIAL PERIOD
The Liaodong Peninsula,as an important part of the East Asian aeolian deposition system,is one of the ideal regions for studying the evolution of the East Asian monsoon and palaeoenvironmental changes due to its sensitivity to climate change.In this study,an aeolian sand depositional profile 362 cm in thickness was obtained in the Liaodong Peninsula area,named Ganghua Profile(GH:39°32′13.94″N,121°20′01.63″E;30m a.s.l),and sampled at 2 cm intervals.3 samples were collected at the depth of 152 cm,236 cm and 292 cm for OSL dating,and the age data obtained were 84.0±5.2 ka,78.8±4.98 ka and 96.7±5.2 ka,respectively.Considering the error range of the OSL dating,the grain size and geochemical elements of Ganghua profile and the deep-sea oxygen isotope curves were compared,and strong correspondence was found.Therefore,it is presumed that the profile determined to the period of the Last Interglacial period(MIS5a～5c).Meanwhile,environmental proxy indicators such as grain size and chemical elements were also measured.The grain size data can be decomposed into 4 end-members:EMI is composed of fine silt with a peak value of 5.7 φ,which represents the component transported by the high-level westerly wind from long distance,and it usually exists in the form of floating silt and settles when winds weakens or with precipitation.The peak value of EM2 is 4.0 φ,dominated by coarse silt and very fine sand,which transported in low altitude by the local wind system and its deposition of near-surface coarse grained sediments affected by dust storms;The peak values of EM3 and EM4 are respectively 2.6 φ and 2.2 φ,mainly fine sand,which transported by near-surface saltation in the form of dust storms.In addition,both of them have high contents in the profile(62.52％),indicating that the EM3 and EM4 are the main sediments supply sources in the profile.Moreover,due to the significant positive correlation between EM3 and EM4 and the median size,we believe that the two are sensitive components affected by winter monsoon,indicating the intensity change of winter monsoon.On the basis of the existing research results,we have discussed the climate change in the study area during the Last Interglacial period(MIS 5c～5a).The results show that:The Last Interglacial climate change in the study area can be roughly divided into three stages:(1)During the MIS 5c,the winter monsoon was relatively weakened,the summer monsoon was stronger,the regional pedogenesis was enhanced,and the climate was relatively warm and humid.(2)From the MIS 5b to the early MIS 5a,the climate was dry and cold,and the climatic environment was very harsh.Meanwhile,the fall of sea level contributed to the exposure of the continental shelf in the Bohai Sea,providing sufficient supply of sandy sediments for the deposition.(3)During the MIS 5a,the climate fluctuated frequently and was in the transitional stage of mild and wet,but the climate was relatively colder compared with that of MIS 5c.
万方数据
维普
