LATE PLEISTOCENE AEOLIAN SEQUENCE AND PALEOCLIMATIC SIGNIFICANCE IN SOUTHERN LIAONING,CHINA
The aeolian deposit in southern Liaoning,an important Quaternary aeolian deposit in Eastern China,records climate oscillations of evident importance for revealing changes in regional palaeoclimate and the East Asian monsoon.The section,named the LHC section(39° 14′54″N,121°40′39″E),has a width of about 30 m and a thickness of about 800 cm.The sampling thickness of this study was 544 cm,and samples were collected at 2 cm intervals.The lithologies of the strata are upper layer of topsoil(0～20 cm),light greyish-yellow sandy layer(20～54 cm),dark greyish-yellow sandy layer(54～280 cm),greyish-yellow medium-coarse sand(280～460 cm),and brown silty sand layer(460～544 cm).A chronological framework of the sedimentary stratigraphy in the study area was established using the optically stimulated luminescence(OSL)dating technique,the age range of the profile is calculated to be around 71.7～61.7 ka,49.4～42.4 ka,ca.23.0 ka and the aeolian sedimentary history since the Late Pleistocene was reconstructed using lithological and proxy indicators.The study obtained several important results:(1)The LHC section preserves historical climate records since the Late Pleistocene.The luminescence dating results revealed ages concentrated in three stages,corresponding to MIS 5a～MIS 4,MIS 3b,and MIS 2,respectively.A time gap of approximately 19 ka exists between 23.0 ka and 42.4ka,and another gap of approximately 12 ka exists between 49.4ka and 61.7 ka.These two age gaps correspond well to MIS 3a and 3c,respectively.It is speculated that aeolian activities were interrupted during MIS 3 c and MIS 3 a under the influence of warm and humid climate.This age discontinuity phenomenon is also present in some areas along the east coast.(2)Due to the sensitive response to changes in the East Asian monsoon of the LHC profile in southern Liaoning,we were able to observe that the MS of the LHC profile suddenly decreased to a value close to that of the last glacial period during the stage 5 a/4 transition,while the Md(φ)decreased to a value equivalent to the value of the MIS4 stage.Subsequently,MS and Md(φ)increased synchronously.Therefore,the grain size data indicate a brief winter monsoon fluctuation in the study area,which is consistent with the climate of the glacial period at that time.(3)During the periods of 66.8～66.2 ka,48.1～47.5 ka,and 22.9～22.3 ka,the Md(φ)values of the LHC section showed significant peaks,indicating multiple strengthening of the East Asian winter monsoon effect,which corresponds to the H events(H6,H5,H2)recorded in GRIP ice core and Hulu cave stalagmites.
万方数据
维普
