塔里木盆地腹地玛扎塔格山隆升时限探讨及其环境意义

摘要

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,岩生主要以灰黄色泥岩、粉砂质泥岩为主.本文以其中出露完全的一段河湖相泥岩、粉砂岩为研究对象,共采集古地磁样品130块16个采点.通过岩石磁学研究,说明主要载磁矿物是磁铁矿,107块样品的磁化率各向异性结果显示地层校正后其最小轴近直立,并且磁面理较磁线理发育,具有沉积组构特征.地层校正后磁化率各向异性最大轴的方向指示了早更新世时研究区域NWW-SEE的古流向.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研究限定研究剖面时代约为1.3～0.9Ma.从而推测玛扎塔格剖面中第四纪地层记录的最近一次构造活动时间约为0.8Ma,即早更新世末中更新世初.河湖相泥岩、粉砂质泥岩的岩性特征代表了当时温湿的气候.研究区近东西向的古流向与玛扎塔格山脊近于平行,附合快速隆升构造地貌特征,暗示该套地层沉积时代(1.3～0.9Ma)对应了玛扎塔格山的快速隆升过程.%The Maza Tagh 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 Maza Tagh Mountain. 16 sites 130 samples were collected from grey yellow mudstones and sand-mudstones. Rock magnetism show the magnetite is the principal carriers of natural remnant magnetization. Thermal demagnetization revealed normal and reversed polarity. Anisotropy of magnetic susceptibility measurements on 107 samples shows a subvertical minimum susceptibility axis in tilt and strong foliation, which indicate their primary depositional nature. The direction of the maximum susceptibility axis in tilt announced the NWW-SEE paleo-current directions. The high resolution magnetostratigraphic results suggest the age of these strata is from 1. 3 ～ 0. 9Ma The time of the newest uplift recorded in this section is about 0. 8Ma. The lithology features of the Lower Pleistocene strata suggest that the paleo-climate is warm and wet The transfer of paleo-current directions imply that the existence of paleo-great lake in the central Tarim basin at Lower Pleistocene and the dramatic uplift of the western of the West Kunlun Mountain at the end of Pleistocene.