塔北阿瓦特剖面磁性地层的构建:天山的脉动式隆升  

Magnetostratigraphic construct of Awate section in the north Tarim Basin: The impulse uplift of Tianshan Range

作　　者：荆显辉[1] 沈忠悦[1] 汪新[1] 余养里[1] 潘小青[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》2011年第6期1575-1583,共9页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(40672019)资助

摘　　要：晚新生代以来天山造山带的构造演化过程仍缺少准确的年龄限制.南天山山前新生界地层普遍缺乏古生物化石以及岩浆活动等定年依据,然而地层沉积连续,适合于磁性地层定年.对阿瓦特地区3700 m厚的晚新生代地层进行了详细的磁性地层研究,建立了该地区西域组底部至吉迪克组顶部的磁极性变化序列,共识别出26个负极性和26个正极性带,与CK95国际标准磁极性年代表对比该段地层年龄大致为1.7～15.1 Ma.结合年龄以及深度数据我们计算了研究区新生界地层的沉积速率,11 Ma时沉积速率由22 cm/ka陡降至约7 cm/ka,经历了4 Ma的缓慢沉积后,在6.5 Ma时陆源碎屑物的堆积突然加快,地层沉积速率也由7 cm/ka升至68 cm/ka,形成了巨厚的库车组地层.地层沉积速率的阶段性变化表明天山山脉在新生代的构造演化是一种脉动式隆升的过程.Magnetostratigraphic results of Awate Section from 1606 horizons in Neogene strata between the upper Jidike Formation and the base of the Xiyu Formation in the Kuche Depression of the Tarim Basin, are used to evaluate the tectonic evolution of Tianshan Range. Progressive thermal demagnetization successfully isolated a linear characteristic remanent magnetization of dual polarity between 450 and 680℃, from which a magnetic polarity sequence is constructed. Twenty-six reversed and twenty-six normal polarity chrons can be identified from the composite magnetostratigraphy, which correlate between - 1. 7 and - 15. 1 Ma with the geomagnetic polarity time scale of Cande and Kent. Sedimentation rates from magnetostratigraphic age versus height show a decrease from -22 to -7 cm/ka at -11 Ma and around 6.5 Ma there was another abrupt increase from - 7 to - 68 cm/ka. These episodic changes can be connected with Late Cenozoic impulse uplift of Tianshan Range.

关 键 词：磁性地层 库车坳陷 新生代 脉动隆升 

分 类 号：P318[天文地球—固体地球物理学]