PERMIAN-TRIASSIC MAGNETOSTRATIGRAPHY - NEW RESULTS FROM SOUTH CHINA

Continuous marine sediments of Permian to Triassic age are widely dist ributed over large areas in Southern China. They offer the potential f or developing magnetostratigraphic columns to investigate the polarity status of the palaeomagnetic field. Three carbonate sections on the Y angtze platform, which represent mainly the Upper Permian but also par ts of the Lower Triassic and possibly parts of the uppermost Lower Per mian, contain a long-term main R-N-R-N-R polarity succession throughou t the Permian. This signal is hidden under-strong overprint magnetizat ions of variable origin and can be mostly obtained only from direction al trends of the natural remanent magnetization during demagnetization rather than from clear stable end-point directions. The new Chinese p olarity sequences are in accord with magnetostratigraphic records from the former USSR and Pakistan. Depending on stratigraphic assignment o f the lithological formations studied, either they include the boundar y between the Lower and Upper Permian and give evidence that the Kiama n reversed polarity superchron had ended before the Upper Permian, or the formations all belong stratigraphically to the Upper Permian, with the oldest reversed interval to be correlated with the reversed zone in the Midian stage of the palaeontologically well-dated Nammal sectio n in Pakistan. This zone is preceded by at least one normal polarity z one at Nammal so that the end of the Kiaman superchron would not be ob served in the new Chinese sections.