JURASSIC PALEOMAGNETIC CONSTRAINTS ON THE COLLISION OF THE NORTH AND SOUTH CHINA BLOCKS

This paper reports a paleomagnetic study of Jurassic rocks from the Ordos Basin in the North China Block (NCB). A recent remagnetization and a high-temperature and/or high-coercivity component with dual polarities have been isolated. The Middle Jurassic pole (74-degrees-N, 233-degrees-E, A95 = 5-degrees) is roughly consistent with previous results, and the Lower Jurassic pole (82-degrees-N, 286-degrees-E, A95 = 7-degrees) is located between the late Triassic and Middle Jurassic poles. These results, combined with paleomagnetic results from adjacent blocks, suggest that 1) the pole for the NCB suffered an angular displacement of 47-degrees +/- 8-degrees between the late Triassic and Middle Jurassic, 2) the SCB underwent final accretion to the NCB in the Middle Jurassic, and 3) accretion of the NCB to Siberia was not complete until the late Jurassic and possibly even until the early Cretaceous.