钻探揭示的青藏高原东北部黄土地层与第四纪气候变化  

LOESS STRATIGRAPHY AND PALAEOCLIMATE CHANGES DURING QUATERNARY IN NORTHEASTERN TIBETAN PLATEAU REVEALED BY LOESS CORE

作　　者：鹿化煜[1] 王先彦[2] 孙雪峰[2] 王晓勇[3] 弋双文[1] 周亚利[2] 刘全玉[4] 

机构地区：[1]南京大学地理与海洋科学学院,南京210093 [2]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安710075 [3]华东师范大学资源与环境学院,上海200062 [4]安康学院化学与生命科学系,安康725000

出　　处：《第四纪研究》2007年第2期230-241,共12页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40325007和30530050);中国科学院知识创新工程项目(批准号:KZCX2-SW-118)资助

摘　　要：青藏高原地表侵蚀强烈，不利于保存连续的第四纪松散沉积物，难以获得良好的高原环境变化记录。在青藏高原东北部的西宁-互助地区，堆积着厚层黄土，是认识高原第四纪环境演化和气候变化重要的信息载体。但是，由于次生黄土披覆较厚，露头剖面不完整，长久以来，对这套风成沉积没有进行过全面细致的研究。根据钻探岩芯揭示的土壤地层、磁性地层以及磁化率变化，初步认为青藏高原东北部厚层黄土堆积底界的年代大约为2．0Ma。黄土-古土壤序列可以与黄土高原中部的标准黄土地层对比，但青藏高原黄土有着更为复杂的沉积和侵蚀过程。在具有较好年代学控制的基础上，可以重建第四纪气候变化的某些细节。在冰期-间冰期时间尺度，青藏高原第四纪气候变化与中国北方气候变化对应，但是，在早更新世青藏高原古气候变化有幅度大和频率高的特点。根据与标准黄土堆积的时间序列对比，在距今129～71ka，254～188ka，334～279ka，428～385ka，576～471ka，670～658ka，748～706ka，788～760ka，883～853ka，1000～967ka，和1120～1061ka等时间段，青藏高原东北部古气候相对温暖湿润；其间厚层的黄土／砂层堆积，即71～12ka，188～130ka，380—334ka，471—428ka，658～576ka，853～788ka，1273～1265ka和1727～1640ka等时间段则反映了寒冷干燥的气候，可能与冰川发育对应。对高原黄土堆积的环境替代性指标的深入研究，不仅可以揭示古气候变化过程，而且可能为研究青藏高原冰川变化提供有价值的线索。As the highest land in the world, Tibetan Plateau has undergone surface erosion in recent geological time, so that unconsolidated sediments are not well preserved and detailed Quaternary palaeoenvironmental and palaeoclimatic record in this immense area has not been well studied. In the northeastern Tibetan Plateau, there is thick loess deposit which probably offer a good opportunity for studying palaeoclimate and palaeoenvironment changes during the Pleistocene and the Holocene, like the loess deposit in Chinese Loess Plateau. However, the thick loess deposits in Tibetan Plateau are not well investigated because they are always covered by reworked loess, and the pedostratigraphy are not well exposed. During the August-November of 2004, we undertook a drill project at the site with the thickest loess deposit, the drill penetrating the loess and reaching fluvial gravels and pebbles underlying the loess. Two continuous cores with thickness of 182m and 232m were obtained, and the coring recovery is over 95%. Here, we report pedostratigraphy, magnetostratigraphy and magnetic susceptibility of these two cores. The preliminary results show that age of the loess deposit is around 2.0Ma, the stratigraphy of the loess- paleosol sequences in the Tibetan Plateau can be correlated with the typical loess-paleosol stratigraphy in central Chinese Loess Plateau, but the Tibetan Plateau loess deposits have more sedimentary hiatuses. Based on our age control, the climate change during the Quaternary period in this high land can be reconstructed, it can be compared with the glacial-interglacial alternations in North Hemisphere, however, climate changes in Tibetan Plateau seems to have larger amplitude and higher frequency during the Early Pleistocene. On the basis of comparison with time series of the typical Chinese loess sequence, the climate in Northeastern Tibetan Plateau was relatively warmer and wetter during 129 -71ka, 254 - 188ka, 334 - 279ka, 428 - 385ka, 576 - 471ka, 670 - 658ka, 748 - 706ka, 788 - 760ka, 883 - 853ka, 100

关 键 词：青藏高原 黄土地层 第四纪气候变化 钻探 磁化率 

分 类 号：P534.63[天文地球—第四纪地质学] P941.74[天文地球—古生物学与地层学]