蒲宗文, 杨振宇, 仝亚博, 赵越, 王恒. 青藏高原东南缘保山地体上新世地壳旋转变形运动的古地磁学研究及构造意义[J]. 地质通报, 2018, 37(5): 759-775.
    引用本文: 蒲宗文, 杨振宇, 仝亚博, 赵越, 王恒. 青藏高原东南缘保山地体上新世地壳旋转变形运动的古地磁学研究及构造意义[J]. 地质通报, 2018, 37(5): 759-775.
    PU Zongwen, YANG Zhenyu, TONG Yabo, ZHAO Yue, WANG Heng. Paleomagnetic study of Pliocene lacustrine strata in the Baoshan Basin at the southeastern edge of the Tibetan Plateau[J]. Geological Bulletin of China, 2018, 37(5): 759-775.
    Citation: PU Zongwen, YANG Zhenyu, TONG Yabo, ZHAO Yue, WANG Heng. Paleomagnetic study of Pliocene lacustrine strata in the Baoshan Basin at the southeastern edge of the Tibetan Plateau[J]. Geological Bulletin of China, 2018, 37(5): 759-775.

    青藏高原东南缘保山地体上新世地壳旋转变形运动的古地磁学研究及构造意义

    Paleomagnetic study of Pliocene lacustrine strata in the Baoshan Basin at the southeastern edge of the Tibetan Plateau

    • 摘要: 青藏高原东南缘受印度板块的持续挤压发生了强烈的陆内变形,前人的研究结果显示,保山地体中新世以来发生强烈的旋转变形,因此,在保山盆地东南缘上新世湖相沉积地层中采集了30个采点(约300块定向样品),其中160块样品分离出了特征剩磁分量,通过了褶皱检验和倒转检验,代表了沉积地层形成时的原生剩磁分量。地层产状校正后剩磁平均方向为:Ds/Is=20.2°/37.1°,Ks=59.7,α95=4.8°,N=16;对应古地磁极为:北纬67.9 °、东经205.7°,A95=2.6。通过与保山盆地东缘科研钻井磁性地层结果进行对比,可以确定羊邑剖面年代为6±0.2Ma;与10Ma东亚构造稳定区古地磁参考极对比发现,保山盆地发生了19.2°±6°的顺时针旋转,表明保山地体上新世以来平均顺时针旋转速率为3.2°±1.0°/Ma,如此快速的旋转速率印证了保山地体和腾冲地块古近纪和中新世古地磁研究所揭示的大角度顺时针旋转变形量。

       

      Abstract: The southeastern part of the Tibetan Plateau has been strongly deformed by the penetration of the Indian Plate since the early Cenozoic. A large clockwise rotation of the Baoshan Terrane was reported through previous paleomagnetic studies. The authors therefore carried out a paleomagnetic study of the Pliocene lacustrine strata in the Baoshan Basin. A total of about 160 samples were treated by thermal demagnetization, and the characteristic remanent magnetism components (ChRMs) were isolated from these sam-ples along the Yangyi section (YYN), southeastern part of Baoshan Basin. Site-mean direction from the YYN is Ds/Is=20.21°/37.1°, Ks=59.7, α95=4.8°, N=16 after tilt correction, which give a paleomagnetic pole at 67.9°N, 205.7°E, A95=2.6°. The ChRM directions of the YYN section pass the fold and reversal tests, indicating that it represents the primary remanent magnetization during the formation of sedimentary rocks. The results reveal that the Baoshan Terrane has suffered from a clockwise rotation about 19.2°±6° relative to the paleomagnetic reference pole of East Asia since the Pliocene. Based on a comparison with the magnetostratigraphic results of the drilled core on the east margin of Baoshan basin, the authors hold that the age of the sampled strata of the YYN section is 6±0.2Ma, and a mean rotating rate of the Baoshan basin is about 3.2°±1.0°/Ma. This result is consistent with the large clockwise rotation of the Baoshan basin since the Miocene revealed by Oligocene and Miocene paleomagnetic studies of the Baoshan Terrane and Tengchong Block.

       

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