Tonian true polar wander events recorded by paleolatitudinal variations of South China and its Southern Hemispheric position in Rodinia

Abstract

Tonian true polar wander (TPW) events, first reported from South China (SC), were later confirmed by a paleomagnetic study of Svalbard. However, recent studies have argued that the dispersion of the Tonian paleomagnetic poles in SC may instead have resulted from remagnetization, local rotation, or inclination shallowing. We conducted a detailed paleomagnetic study on the ca. 792 Ma Kaijianqiao Formation in SC. Demagnetization and rock magnetic experiments revealed a primary remanence carried by detrital hematite, which recorded seven geomagnetic polarity reversals. We reviewed the Tonian poles from SC and found that all have various positive field tests, which argue against remagnetization being the cause of their dispersion. Additionally, statistical tests suggest that inclination shallowing has had a minimal influence on these poles. The paleolatitudinal variation of SC during ca. 805−780 Ma demonstrates three stages of fast motion; although they exceed the speed of plate tectonics, they are consistent with the previously proposed TPW event in the late Tonian. Therefore, we explain the dispersion of the 810−750 Ma poles in SC by a combination of TPW and vertical-axis rotation. By comparing the paleolatitudinal variations of SC predicted by seven reconstruction models of Rodinia, we propose that SC was in the Southern Hemisphere during the late Tonian and located on the southern or western periphery of Rodinia.