PALEOMAGNETIC FEATURES OFSINO-KOREA PLATE IN LATE PALEOZOIC ERA
Lin Wanzhi, Shao Jian and Zhao Zhangyuan(Department of Geology, Beijing University)
Abstract / With a view to further ascertaining tie relative position of the Sino-Korea Plate in late Paleozoic Era and investigating the migration of various plates in Asia, a total of 70 paleomagnetic hand specimens of Carboniferous and Permian sediments were collected along the Qiligou section and the West Valley (Due-rping) section at Xishan, Taiyuan on Shanxi anteclise which, lying in the middle of the North China Platform, were relatively stable during the late evolution stage of the platform. These hand specimens were cut into 140 samples which, after being subjected to heating demagnetization, were measured for remanent magnetization one by one. The average magnetization, paleolatitude and paleopole for every sampling site were thus obtained. The data acquired indicate the following facts. (1) Average paleolatitude of sampling sites during Permian was 24.9° and the difference in latitude between Sino-Korea Plate and Siberia Plate at that time was about 1200km larger than the present difference; paleolatitude in Carboniferous was averagely 16.2° and the difference in latitude between these two plates was some 2100km larger than the present difference. It is tentatively presumed that the Sino-Korea Plate must have lain within low-latitude area in late Paleozoic, in the process of migration from low latitude to high latitude. (2) The formerly-defined Permian strata are of negative polarity with the exception of the middle portion of Shiqianfeng Formation which possesses positive polarity. This formation, according to a comparison of documents available, is preliminarily assigned to Triassic.