TRIASSIC PALEOMAGNETIC DATA FROM SOUTH CHINA AND THEIR BEARING ON THETECTONIC EVOLUTION OF THE WESTERN CIRCUM-PACIFIC REGION

We report Early and Middle Triassic paleomagnetic data from the south Chinese provinces of Fujian and Guangxi. The characteristic magnetizat ion of the rocks in each case is concluded to be a primary remanence t hat passes the fold test. The Triassic pole from western Guangxi and f our other Triassic and Late Permian poles from three provinces that li e on undisputed parts of the Yangtze craton are well clustered. This s uggests that Guangxi (except the southeast part) was also a part of th e Yangtze craton, at least since the Triassic and probably since the L ate Permian. With respect to the Yangtze craton, between the Early Tri assic and the Late Cretaceous, Fujian may have been rotated 121 +/- 9 degrees counterclockwise and displaced 22 +/- 9 degrees north, or rota ted 59 +/- 9 degrees clockwise and displaced 3 +/- 9 degrees south, de pending on the hemisphere in which the magnetization was acquired. Bas ed on consistency with other paleomagnetic results, and in accordance with the geologic data from the area, the former interpretation is pre ferred. A remarkable coincidence of Mesozoic poles for south China and south Korea is observed which, if true, implies that the South China Block (except for the displaced terranes in the coastal provinces) and Korea may have been part of the same continental landmass from the Tr iassic onwards. This is consistent with some geologic observations sug gesting affinities between the two places. It also implies that the ma jor fault zones in north China (e.g., the Tan-Lu fault) are unrelated to major fault zones in southeast China (e.g., the Changle-Nanao fault ), with the former probably associated with the suturing of north and south China and the latter influenced by proto-Pacific plate motion.