SEVERE REMAGNETIZATION REVEALED FROM TRIASSIC PLATFORM CARBONATES NEAR GUIYANG, SOUTHWEST CHINA

An intensive paleomagnetic investigation has been conducted on the Mid dle and Lower Triassic platform carbonates near Guiyang, Southwest Chi na in the hope of refining a Middle Triassic paleomagnetic pole previo usly reported from the region. Instead, severe late Cretaceous to Rece nt remagnetizations have been revealed from all the three rock formati ons studied, In all cases, the in situ characteristic remanent magneti zation (ChRM) directions resemble or fall close to the local present-d ay Earth's magnetic field direction and fail the fold test, despite th e presence of dual polarity in two formations, The major magnetic carr iers of the remagnetizations are hematite and magnetite. The cause(s) for the remagnetization events cannot be ascertained at present, but w eathering in recent time and migrating fluid in the past might be resp onsible. It is suggested that caution should be exercised when investi gating platform carbonate rocks which are prone to late remagnetizatio n.