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首页> 外文期刊>Journal of Asian earth sciences >Magnetic fabric and paleomagnetism of the Middle Triassic siliciclastic rocks from the Nanpanjiang Basin, South China: Implications for sediment provenance and tectonic process
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Magnetic fabric and paleomagnetism of the Middle Triassic siliciclastic rocks from the Nanpanjiang Basin, South China: Implications for sediment provenance and tectonic process

机译：华南南盘江盆地中三叠统硅质碎屑岩的磁性构造和古磁性：对沉积物物源和构造过程的启示

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摘要

A combined magnetic fabric and paleomagnetic study has been carried out on the siliciclastic rocks gathered from a stratigraphic cross-section through the Nanpanjiang Basin, South China, in an attempt to extract the paleoflow information preserved in and, thus, constrain the possible origins of these clastic rocks. The sediments used for this study were formed by sediment-gravity flows along the southern margin of the South China block in the Middle Triassic time (ca. 245-228 Ma). The results show a normal distribution of both low field magnetic susceptibility values and natural remanent magnetization intensities, which along with the monotonic detrital framework mode, mainly comprising quartz and lithic particles, may suggest a single provenance involved in deposition of these clastic deposits. Anisotropy of magnetic susceptibility (AMS) analysis acquires primarily the sedimentary magnetic fabrics, which, in this study, reveal paleoflow directions ranging from NNW to ENE with an overall mean orientation of NE. Demagnetization on a part of samples isolates a characteristic remanent component averaged at D = 44.8°, I = 16.9°, k = 9.7, α_(95) = 6. 5°, n = 55, corresponding to a paleolatitude N8.6° and a clockwise rotation of ca. 45° since the Middle Triassic for the studied cross-section. This mean direction passes fold tests and is consistent with the reference direction expected from the South China block at the 95% confidence level. Restoring this ～45° declination renders an overall northward paleoflow, which, combined with other evidence, suggests a southern provenance for these sediments during deposition in the Middle Triassic time. In terms of the early Mesozoic plate framework of southeastern Asia, a tectonic scenario is proposed here, whereby the nearly N-S convergence of the Indochina and South China blocks and its related Indosinian orogeny in the Middle Triassic caused the formation of the Nanpanjiang foreland basin, which was filled by voluminous detritus shed from the uplifted orogenic belt on its southern side.
机译：通过对华南南盘江盆地地层剖面中收集的硅质碎屑岩进行了磁性结构和古磁学的联合研究，试图提取保留在其中的古流信息，从而限制了它们的可能成因。碎屑岩。用于这项研究的沉积物是由中三叠纪时期（约245-228 Ma）沿华南地块南缘的沉积物重力流形成的。结果表明，低场磁化率值和自然剩余磁化强度均呈正态分布，这与主要由石英和石屑颗粒组成的单调碎屑构架模式一起，可能表明这些碎屑沉积物的沉积涉及单一来源。磁化率各向异性（AMS）分析主要获得了沉积磁性织物，在这项研究中，它揭示了从NNW到ENE的古流向，NE的总体平均方向。对一部分样品进行退磁可以分离出平均剩磁特征分量，其平均值为D = 44.8°，I = 16.9°，k = 9.7，α_（95）=6。5°，n = 55，对应于古纬度N8.6°和约顺时针旋转。自中三叠纪以来45°为研究断面。该平均方向通过了褶皱测试，并且与华南地区在95％置信水平下预期的参考方向一致。恢复到〜45°的偏角将呈现总体北向古流，再结合其他证据，表明这些沉积物在中三叠世时期为南方成因。根据东南亚的中生代早板构架，提出了一种构造场景，即中三叠世印度支那和华南地块的近南北向辐合及其相关的印支期造山运动导致了南盘江前陆盆地的形成。从南部隆起的造山带上喷出的大量碎屑填满了它。

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  • 来源
    《Journal of Asian earth sciences》 |2014年第5期|134-147|共14页
  • 作者

    Jianxin Cai; Xiaodong Tan; Yi Wu;

  • 作者单位

    Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;

    Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;

    Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;

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  • 正文语种 eng
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  • 关键词

    South China block; Nanpanjiang Basin; Siliciclastic rocks; Paleoflow; Provenance;

    机译：华南地块;南盘江盆地硅质碎屑岩;古流;出处;

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