Further paleomagnetic results from the Silurian of the Yangtze Block and their implications

Silurian redbeds were sampled at two localities in northeastern Guizhou and Yunnan provinces of China for paleomagnetic study. Progressive thermal demagnetization revealed multiple magnetic components from these samples: a low unblocking temperature component (A) of recent origin, a post-folding middle to high unblocking temperature component (B) probably acquired during late Mesozoic time, and a pre-folding high unblocking temperature component (C). Two statistically distinguishable groups of directions were further recognized from the C component with one (C1) having more easterly declination than the other (C2) and both having a of shallow inclination. The paleomagnetic pole from the C1 magnetization coincides with a pre-folding pole reported from the coeval rocks in neighboring southern Sichuan Province; its relation to the apparent polar wander path (APWP) for the Yangtze Block (YB) suggests that the C1 magnetization was probably acquired during the Silurian. By the same argument, the C2 magnetization was probably acquired sometime between the Silurian and Carboniferous. These results reconfirm the equatorial position for the YB during mid-Paleozoic time and clockwise rotation of the YB since at least the mid-Cambrian.