塔里木盆地南缘新生代沉积:对青藏高原北缘隆升和塔克拉玛干沙漠演化的指示  

Cenozoic sedimentation in the southern Tarim Basin:Implications for the uplift of northern Tibet and evolution of the Taklimakan Desert

作　　者：郑洪波[1] 贾军涛[2] 王可[1] 

机构地区：[1]南京大学地球科学与工程学院,江苏南京210093 [2]同济大学海洋地质国家重点实验室,上海200092

出　　处：《地学前缘》2009年第6期154-161,共8页Earth Science Frontiers

基　　金：国家自然科学基金重点项目(40830107)

摘　　要：塔里木盆地南缘新生代沉积地层厚达万米以上。研究的叶城和阿尔塔什两个剖面分别厚4500m和7000m,基本代表了塔里木南部的新生代沉积。叶城剖面的底界年龄根据磁性地层测定约为8Ma。阿尔塔什剖面的底界年龄根据海相碳酸盐岩87Sr/86Sr的比值与全球Sr同位素曲线对比,约为30～35Ma。从岩性地层分析,剖面的下部为中新统乌恰群,主要由泥岩和粉砂岩组成,沉积相为低能环境的辫状河和曲流河。剖面的中部是上新统阿图什组,由红色泥岩、砂岩夹薄层砾岩以及埋藏风成黄土构成,沉积环境为冲-洪积扇的中远端。剖面的上部是上新统—下更新统西域组,由中粗砾岩夹块状粉砂岩透镜体(埋藏风成黄土)组成,主要是近源洪积扇沉积和风成沉积,以上地层层序可以进行很好的区域对比。塔里木盆地南缘新生代沉积由新近纪红层向上变化为逆粒序砾岩和碎屑流沉积,记录了青藏高原北缘隆升造成的沉积环境的变化,尤其是干旱化气候的阶段性演化。在约8Ma时,叶城和阿尔塔什两个剖面都发育了风成沙丘沉积。而在阿尔塔什剖面,沙丘沉积之下还发育了一套厚层的膏盐沉积,指示了塔里木盆地南缘在此前后已经相当干旱,只是仅凭这些证据还难以判断沙漠发育的规模。而上新世—更新世阿图什组和西域组中发育的埋藏风成黄土沉积,则指示了塔克拉玛干沙漠在此时已经发育到了相当规模,极度干旱的气候条件(可能类似于现在)已经形成。The Yecheng and Aertashi sections comprise ～4.5 km and ～7.0 km of Cenozoic sedimentary successions,respectively.The age control of the two sections is based on magnetostratigraphy,87Sr/86Sr measurement and regional stratigraphic correlation.The lower part of the sections is mainly composed of fine-grained mudstone and fine sandstone,which makes up the Wuqian Group（Miocene）.The palaeoenvironment is low-energy,meandering and braided streams.The middle part is composed of red mudstone,sandstone with thin conglomerate beds,which makes up the Artux Formation（Pliocene）.The paleoenvironment is distal-to mid-fan environment.The uppermost part of the section,known as the Xiyu Formation（Plio-Pleistocene）,consists of cobble and boulder conglomerate intercalated with massive siltstone lenses,which formed as proximal alluvial fan and eolian deposits.The formation of eolian dunes at ～8 Ma and underlying playa lake deposits（as at Aertashi）may indicate an arid,enclosed basin in the southern Tarim at that time.Eolian loess deposition as represented by the siltstone bands in the Xiyu and Artux Formations indicates that the Taklimakan Desert and the regional climate regime may have been fully developed by the Early Pliocene.The onset of eolian sedimentation in the southern Tarim Basin coincided with the uplift of the northern Tibetan Plateau.The Tibetan Plateau uplift resulted in the shift of sedimentary environments northwards into the southern Tarim Basin,and could well have triggered the onset of full aridity in the Taklimakan region.

关 键 词：塔里木盆地南缘 青藏高原北缘 塔克拉玛干沙漠 晚新生代沉积环境 

分 类 号：P534.6[天文地球—古生物学与地层学]