Severe remagnetization revealed from Triassic platform carbonates near Guiyang, Southwest China

An intensive paleomagnetic investigation has been conducted on the Middle and Lower Triassic platform carbonates near Guiyang, Southwest China in the hope of refining a Middle Triassic paleomagnetic pole previously reported from the region. Instead, severe late Cretaceous to Recent remagnetizations have been revealed from all the three rock formations studied. In all cases, the in situ characteristic remanent magnetization (ChRM) directions resemble or fall close to the local present-day Earthʹs magnetic field direction and fail the fold test, despite the presence of dual polarity in two formations. The major magnetic carriers of the remagnetizations are hematite and magnetite. The cause(s) for the remagnetization events cannot be ascertained at present, but weathering in recent time and migrating fluid in the past might be responsible. It is suggested that caution should be exercised when investigating platform carbonate rocks which are prone to late remagnetization.