Paleomagnetism of a well-dated marine succession in South China: A possible Late Cambrian true polar wander (TPW)
Paleomagnetism of a well-dated marine succession in South China: A possible Late Cambrian true polar wander (TPW)
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华南地区古老的海洋序列的古地磁学：可能是晚寒武世真极漂移（TPW）
DOI：
10.1016/j.pepi.2018.01.009
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发表时间：
2018-04-01
影响因子：
2.3
通讯作者：
Yang, Zhen-Yu
中科院分区：
文献类型：
--
作者：
Jiao, Wen-Jun;Li, Yong-Xiang;Yang, Zhen-Yu
寒武纪真极移（TPW）假说一直存在争议，主要是因为古地磁数据的质量和/或保真度以及它们的年代控制的不确定性。验证TPW假说需要具有足够空间和时间分辨率的高质量古地磁数据。在这里，我们提出了一个连续的中国南方寒武纪浅海序列的古地磁结果，详细的生物地层提供了特殊的年代限制。从这个石灰岩为主的序列中收集了43个古地磁样品。逐步热退磁一般揭示三分量磁化。低温和中温部件可以通过类似于330摄氏度的温度进行清洗，而高温部件（HTC）通常从类似于350摄氏度到类似于450摄氏度进行隔离。一个积极的褶皱测试和地层中存在的反极性，以及岩石磁性数据以及扫描电子显微镜（SEM）和透射电子显微镜（TEM）的结果，共同表明，HTC可能是主要的。一个方向性的转变发生在下-中寒武统和上寒武统地层之间的继承，并初步解释为类似57度的极移从类似500.5至494 Ma。由于极移速率太快，不可能是构造成因，因此极移被解释为代表晚寒武世TPW。这TPW出现同时代的Steptoean正碳同位素偏移（SPICE）和主要三叶虫的质量迁移，表明TPW和晚寒武世生物和气候变化之间的潜在联系。由于拟议的TPW事件是非常好的日期，它应该是通过检查其他世界各地的部分测试。
The Cambrian true polar wander (TPW) hypothesis remains controversial largely because of the uncertainties in the quality and/or fidelity of the paleomagnetic data as well as their chronological control. Testing the TPW hypothesis requires high-quality paleomagnetic data of sufficient spatial and temporal resolutions. Here, we present paleomagnetic results of a continuous Cambrian shallow marine succession from South China where available detailed biostratigraphy provides exceptional chronological constraints. Forty-three sites of paleomagnetic samples were collected from this limestone-dominated succession. Stepwise thermal demagnetization generally reveals three-component magnetizations. Low- and intermediate-temperature components can be cleaned by similar to 330 degrees C, and the high-temperature component (HTC) was isolated typically from similar to 350 to similar to 450 degrees C. A positive fold test and the presence of reversed polarity in the strata, together with rock magnetic data as well as the scanning electron microscopic (SEM) and transmission electron microscopic (TEM) results, collectively suggest that the HTCs are likely primary. A directional shift of the HTCs occurs between the lower-middle Cambrian and the upper Cambrian strata in the succession and is tentatively interpreted to indicate a similar to 57 degrees polar wander from similar to 500.5 to 494 Ma. Because the rate of polar wander is too fast to be a tectonic origin, this polar wander is interpreted to represent a Late Cambrian TPW. This TPW appears coeval with the Steptoean positive carbon isotope excursion (SPICE) and the major trilobite mass extinctions, suggesting a potential link between the TPW and the Late Cambrian biotic and climatic changes. Because the proposed TPW event is exceptionally well-dated, it should be testable through examination of other worldwide sections.