Timing of the North‐South China collision from new middle to late Mesozoic paleomagnetic data from the North China Block

Abstract

We collected paleomagnetic samples from 43 sites of Middle and Upper Jurassic and Cretaceous rocks along a 250 km wide east‐west trending belt located north of the suture between the North and South China Blocks. In each case, laboratory treatment isolates dual polarity, antipodal magnetizations that are demonstrably pre‐folding. The paleomagnetic poles show very good coherence with coeval poles from other localities from the North China Block (NCB), suggesting the apparent polar wander path (APWP) from the NCB is not distorted by post‐Middle Jurassic local vertical axis block rotations. A comparison of the NCB APWP with that from the South China Block suggests that collision continued after the Early Jurassic and ended no later than the Late Jurassic. A cusp in the NCB APWP coincides with a marked angular unconformity that separates Middle Jurassic from Upper Jurassic and younger sediments. Together, these observations indicate that the scissor‐like collision and associated deformation ceased at the Middle to Late Jurassic boundary (∼159 Ma). The time of rapid (1°/Ma) relative angular velocity between the two plates (225 to 190 Ma) coincides with a peak in U‐Pb and Ar‐Ar dates obtained from metamorphic rocks in the suture. The combined Late Jurassic and Cretaceous paleomagnetic data from both blocks suggest that the united China plate traveled 2000 km north relative to Eurasia during the Late Jurassic before docking in the Cretaceous. This younger collision event is also marked by a cusp on the Cretaceous part of the Eurasian APWP.