库车坳陷克拉苏河新生代沉积岩磁组构特征与古流向分析  

Characteristics of magnetic fabrics and paleocurrent directions of Cenozoic sediments in the Kelasu River,Kuqa Depression

作　　者：张志亮[1] 沈忠悦[1] 汪新[1] 唐鹏程[1] 余养里[1] 赵博[1] 潘小青[1] 石林权[1] 

机构地区：[1]浙江大学地球科学系,杭州310027

出　　处：《地球物理学报》2013年第2期567-578,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41072155和40672019)资助

摘　　要：塔里木盆地库车坳陷克拉苏河沿岸发育良好的新生界地层.我们对克拉苏河沿岸新生界剖面分A、B两段进行系统采样,获得定向岩芯样品1700余块.岩石磁学研究表明,新生代沉积岩中磁性矿物以赤铁矿为主,含有少量磁铁矿;磁组构测试结果显示,两段剖面磁面理均较磁线理发育,最小磁化率主轴近于直立,显示原生沉积组构.A剖面磁化率主轴к1的偏角指示古流向.库姆格列木群沉积时的古水流方向为NEE—SWW向,至苏维依组沉积时,流向变为NNE—SSW向.河流古流向在苏维依组形成时发生急剧变化,说明南天山此时可能发生了明显的隆升,且以北西部隆升为主;B剖面为吉迪克组、康村组和库车组粗粒碎屑岩,磁组构显示к1-к2构成的磁面理与层理面小角度相交,к3呈叠瓦状分布,可以用来指示古水流方向.从吉迪克组至库车组下段,古流向均为NNW—SSE,但逐渐偏东,暗示天山在此期间处于缓慢的隆升期或东西部处于同步隆升,且西部隆升速度快于东部.Cenozoic strata developed well along the Kelasu River, Kuqa Depression, Tarim Basin. A total of 1700 reoriented core samples were collected systematically from the two Cenozoic sections （A and B） at the two banks of the Kelasu River. Rock magnetism analysis shows that hematite and subordinate magnetite are dominant magnetic carriers in the Cenozoic sediments. The results of AMS indicate that the magnetic foliation of the two sections is more obvious than the magnetic lineation, and the minimum magnetic axes （K3） is nearly perpendicular to bedding planes, which illustrates a primary sedimentary fabric. The maximum magnetic axis （K1） was used to indicate the paleoeurrent directions in section A. The paleoeurrent of Kumugeliemu （KMGLM） Fro. was in NEE--SWW, while it turned to NNE--SSW when Suweiyi （SWY） Fro. was deposited. The sharp turning of the paleocurrent direction during the deposition of SWY Fro.suggests that southern Tianshan might have experienced a rapid uplift, especially in its northwestern part. The imbrication of Ka is also an indicator of the paleocurrent direction. From JDK Fm. to the lower part of Kuqa Fm. , the paleocurrent was in NNW--SSE,with a tendency to turn to the east. It implies that the southern Tianshan was uplifting slowly or the east and west of the Tianshan were rising simultaneously, with a larger rate in the west than in the east during this time.

关 键 词：磁组构 古流向 库车坳陷 新生代 克拉苏河 

分 类 号：P318[天文地球—固体地球物理学]