VERTICAL-AXIS BLOCK ROTATIONS IN SOUTHWESTERN CHINA SINCE THE CRETACEOUS - NEW PALEOMAGNETIC RESULTS FROM HAINAN-ISLAND

A paleomagnetic study of Early Cretaceous redbeds from Hainan Island, South China, reveals a pre-folding remanence from six sites, with a me an direction of D=4.3 degrees, I=41.8 degrees, k=51.5, alpha(95)=9.4 d egrees. The results suggest that Hainan Island may have been rotated s imilar to 10 degrees counterclockwise about a vertical axis since the Early Cretaceous. This rotation is likely to have occurred during the mid-Tertiary, when large scale left-lateral motion occurred along the Red River Fault as a result of the indentation of the Indian Plate int o Eurasia causing extrusion of the Indochina Block, and opening of the South China Sea. A comparison of Early Cretaceous paleomagnetic resul ts from South China indicates that local rotations are widespread in t he western part of the South China Block, Such rotations have to be ta ken into account when examining pre-Cenozoic tectonic kinematics of So uth China, and constructing apparent polar wander path(s) for the regi on.