摘要
通过柴达木盆地南八仙剖面磁性地层学研究，建立了部分上油砂山组磁极性序列，认为该剖面时代为7．5～9．0Ma。从320块样品的古地磁数据分析，揭示了一组高温特征剩磁分量，在95％置信度下通过倒转检验（B级），说明这组高温分量很可能代表岩石形成时的原生剩磁，其特征剩磁方向为：地理坐标下为Dg＝358．5°，Ig＝40．5°，k＝28．5，α95＝4．2，层面坐标下为Ds＝1．0°，Is＝41．5°，k＝34．0，α95＝3．8；相应的极位置为λp＝75．9°N，φp＝270．5°E，dp＝2．8°，dm＝4．6°。通过与同时代柴达木盆地及邻区的古地磁极对比，说明中中新世以来柴达木地块整体上没有经历明显旋转运动，阿尔金断裂活动致使肃北等毗邻断裂带地区发生了构造旋转。
Abstract
Based on the magnetostratigraphic study at Nanbaxian section,Qaidam basin,a magnetic polarity sequence of Shangyoushashan Formation has been established.The magnetostratigraphic result suggests the age of 7.5 9.0 Ma.A stable high temperature characteristic remanence component is isolated by stepwise thermal demagnetization from 320 samples through a positive reversal test at the 95% confidence level,which may possibly represent the rock’s primary remanence.The mean direction is D g=358.5°,I g=40.5°,k=28.5,α95 =4.2,D s=1.0°,I s =41.5°,k =34.0,α95 =3.8,corresponding to a paleopole atλp=75.9°N,φp =270.5°E,d p=2.8°,d m=4.6°.In comparison of this paleomagnetic poles from the Qaidam basin with those from adjacent region,no tectonic rotation in Qaidam basin has been identified;however the tectonic rotation of Subei basin has been occurred and resulted from the left-slip of Altyn Tagh fault since Middle-Miocene.
基金项目
中国地质调查局基础研究项目(1212011121267)
中国地质调查局基础研究项目(1212011120964)
国家自然科学基金(41172177)
NETL
NSTL
维普
万方数据