辽南黄土光释光年代地层探讨

本文依托辽南地区七顶山黄土沉积剖面,对黄土年代地层进行光释光(OSL)测年研究,结合古地磁数据资料,并与东部丘陵平原区已有释光年代比较,结果表明,七顶山黄土堆积的开始时代为中更新世早期。相当于黄土高原的马兰黄土堆积时代为晚更新世,离石黄土与马兰黄土的分界年代为100～110ka左右,这与黄土高原的研究结论相一致,反映地球轨道参数控制的气候变化。马兰黄土的堆积时间集中在末次冰期的早期(MIS4-5d)和晚期(MIS2),对应时代分别为86～113ka和22～31ka,而在末次冰期中期(MIS3),由于较高的气温和丰沛的降水及地势条件的影响,造成本区大约4～5万年的地层缺失。中国东部丘陵平原区年代地层学研究显示马兰黄土堆积是比较连续的,具体原因有待进一步深入探讨。

Study on the Loess Layer in the South of Liaoning Province Using the Optically Stimulated Luminescence

According to the optically stimulated luminescence(OSL) dating method as well as the correlation with the OSL and TL dating results of the hill and plain regions in eastern China,the authors studied the typical Qidingshan loess profile.The results indicated that the time of the loess accumulation of Qidingshan was from the early stage of the middle Pleistocene,while the Malan loess accumulated since the 100～110 ka.During the last glacial cycle,the Malan loess was mainly deposited in the early and late stage of the last glacial cycle and the relative absolute OSL ages were 22～31 ka and 86～113 ka.There is about 40～50 ka loess layer absence in Qidingshan profile as possibly the higher temperature,plentiful precipitation and landforms.However,this phenomenon did not appear in the other sites in the southern of Liaoning province.The relative continually loess deposits show the loess accumulation affected not only by the climate but also by the geomorphology even in the same district.Moreover,the OSL dates reflect that the loess unusual accumulation in the south of Liaoning province.The reason may be that the quartz grains were influenced by the source of dust and transport distance.