Paleomagnetic directions recorded in 820 to 780 million year old rocks from South China exhibit large amplitude changes that vary rapidly, which have been interpreted to indicate extraordinarily fast motion of Earth's crust and mantle, up to 90° within a 5 million year span, with respect to the spin axis of the core. This hypothetical phenomenon, called rapid true polar wander (TPW), could be responsible for dramatic global environmental change at that time.
To test this theory, the team collected over 1,000 samples from a well exposed section where the incongruous directions are found. Their measurements suggest that some of the rocks acquired a new magnetic signal during a pervasive remagnetization event in South China around 440 million years ago, long after original deposition of the rocks. New hematite growth has a demagnetization spectrum that partially overlaps or completely obscures the original magnetic signal, which was previously unrecognized. This implies that rapid TPW is likely an artifact of magnetic overprinting in ancient rocks from South China.
Their new results suggest that South China was in a relatively stable position at high latitudes 809 to 804 million years ago. They find no evidence to support exceptionally fast continental drift or an abnormal geomagnetic field geometry during that time.
You can read the full paper here and a summary here.
Citation: Tonti-Filippini, J. A. D., Robert, B., Muller, É., Paul, A. N., Dellefant, F., Wack, M., et al. (2024). Middle Neoproterozoic (Tonian) polar wander of South China: Paleomagnetism and ID-TIMS U-Pb geochronology of the Laoshanya Formation. Journal of Geophysical Research: Solid Earth, 129, e2023JB027634.