Tectonic rotation in the western South-Dabashan orogenic belt in late Mesozoic

A paleomagnetic study was carried out on Early-Middle Jurassic sediments in the Zhenba area, the western South-dabashan orogenic belt. Stepwise thermal demagnetization isolated the characteristic high temperature component (HTC) (D=37.1A degrees, I=46.1A degrees, alpha (95)=10.1A degrees), which passed the fold test. By comparing the corresponding pole of HTC (57.6A degrees N, 196.6A degrees E, A95=9.9A degrees) with coeval reference poles for the Sichuan basin, we detected a 26.5A degrees A +/- 9.0A degrees clockwise rotation of the study area relative to the stable Sichuan basin. We interpret that this rotation was caused by obstruction of the Hannan block during thrusting of the Dabashan, and occurred around Early Cretaceous.