早更新世以来青藏高原隆升作用在塔里木盆地腹地的响应

自约55Ma印度-欧亚板块碰撞,青藏高原经历持续挤压,发生多次阶段性隆升作用.晚新生代以来强烈隆升作用不仅造就了青藏高原北部强烈的构造变形效应,还引起了大规模的干旱化.位于塔里木盆地腹地(N38° 40.911′,E80°18.484′)的玛扎塔格褶断带东西向延伸约300km,南缘发育出露连续、完全的早更新世地层,岩性主要以灰黄色泥岩、粉砂质泥岩、粉砂岩为主,含有薄层粗砂岩及砾岩.本文延展了原来研究剖面,共采集古地磁样品90块共9个采点.系统热退磁结果揭示出了正反极性,高分辨率的磁性地层学及野外磁化率研究确定研究剖面时代约为2.2～0.1Ma,对玛扎塔格整个剖面地层的年龄控制提供了限定.利用MS2磁化率仪对野外剖面现场测量,采集209米695点数据.通过与深海氧同位素比对分析,说明磁化率结果不仅较好揭示了全球气候变化,还精确记录了约1.8Ma、1.2Ma、0.9Ma、0.65Ma等多期构造活动,并且直接证明年龄约0.05Ma的地层发生了较强构造变形.青藏高原早更新世以来隆升过程具有脉冲特征,约0.9Ma的强烈隆升使主体达到冰冻圈,起到的屏障效应使塔里木盆地开始较快速干旱化,同时为黄土高原提供了更多风尘物质和增强了对粉尘的搬运能力,导致巨厚的粗粒上砂岩层L9形成.

The response of the Tibet uplift since Lower Pleistocene in the centre of Tarim basin.

The pulse uplift of Tibetan Plateau is a compressing uplift event resulted from the inner continent subduction of Indian Plate since ca. 55Ma. The uplift of northern Tibetan plateau occurred in the Late Cenozoic definitively influenced the tectonic formation and the large scale aridity. The Mazartagh fault zone lies in the central Tarim basin (latitude: N38°40.911', longitude: E80°18.484'), about 300km long in the west-east direction. Lower Pleistocene section is a complete sedimentary sequence and well-exposed section in the south of Mazartagh Mountain. This study extends this section, and 9 sites 90 samples were collected from grey yellow mudstones and siltstone. The high resolution magnetostratigraphic results and magnetic susceptibility suggest the age of these strata is from 2.2~0.1Ma. Magnetic susceptibility was measured on 209m depth surface outcrop of this section, at 10~40cm intervals by using the Bartington MS2 surface sensor. The coincident correlation of magnetic susceptibility to deep-sea oxygen isotope records suggested that this section recorded the global climatic variety. The increase elevation of Tibet might have enhanced the Tarim basin aridification. The magnetic susceptibility peak value area may imply that the uplift in the northern margin of Tibet at ca. 1.8Ma, 1.2Ma, 0.9Ma, 0.65Ma. The uplift of the Tibetan plateau at ca.0.9Ma may have resulted in the increase in dust sources and dust transport capability, as associated with the upper sand layer L9 coarsest loess deposition.