Early Paleozoic paleomagnetic poles from the western part of the North China Block and their implications

被引:104
作者
Huang, BC [1 ]
Yang, ZY
Otofuji, Y
Zhu, RX
机构
[1] Chinese Acad Sci, Inst Geophys, Beijing 100101, Peoples R China
[2] Kobe Univ, Fac Sci, Dept Earth & Planetary Sci, Kobe, Hyogo 6578501, Japan
[3] Chinese Acad Geol Sci, Inst Geomech, Beijing 100081, Peoples R China
基金
中国国家自然科学基金; 日本学术振兴会;
关键词
North China Block (NCB); early Paleozoic; paleomagnetism; paleogeography; Apparent Polar Wander Path (APWP);
D O I
10.1016/S0040-1951(99)00098-0
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We collected 917 oriented drill-core samples (124 sites) from 22 units spanning the Early Cambrian to Middle Ordovician formations of the North China Block (NCB) to construct an apparent polar wander path (APWP) of the early Paleozoic for the NCB. Sampling areas are located in the Helanshan, Tongchuan-Hancheng and Yuncheng-Luliang regions along the margin of the Ordos Basin. Characteristic remanent magnetizations for five periods between the Cambrian and Ordovician are isolated from 281 samples by careful demagnetization. Directions cluster around northwesterly direction with upward shallow inclination and its antipode after tilt correction. Reliability of these five directions is ascertained through positive fold and reversal tests. The five Cambrian and Ordovician paleopoles plot in the present Atlantic Ocean, which is consistent with previously reported paleomagnetic poles. A newly constructed APWP between the Cambrian and Ordovician indicates that the NCB was located in the Southern Hemisphere around 15 degrees S during Cambro-Ordovician time. Motion of the NCB between the Early and Middle Cambrian comprised: a counterclockwise rotation of 22.3 degrees +/- 7.0 degrees and a northward latitudinal displacement of 7.2 degrees +/- 6.8 degrees. Combining the paleobiogeographic and paleoclimatic data with the paleomagnetic implies that the NCB was probably located in East Gondwana in the Early Cambrian, and may have separated from Gondwana in post-Early Cambrian time. The NCB is also inferred to have been located close to Siberia and North America during the Middle Ordovician. (C) 1999 Elsevier Science B.V. All rights reserved.
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页码:377 / 402
页数:26
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