Cretaceous and Early Tertiary paleomagnetic results from the Lanping basinand its geological implications

After detailed paleomagnetic sampling and thermal demagnetization for Creta ceous and Early Tertiary rocks from the Lanping basin, Western Yunnan, a gr oup of higher temperature characteristic components were revealed. The dire ctions from both the Jinxing and Yunlong formations pass reversal test at 9 5% confidence level, and a positive fold test is achieved at the 99% confid ence for the Nanxin and Futoushi formations. It implies that this group of directions may represent a primary magnetization formed during the formatio n of the rocks. Comparing with geological time scale, we note that Nanxin f ormation can be correlated with Cretaceous Albian, Cenomanian and Turonian stages, Futuoshi formation matches with Coniacian and Santonian stages. In comparison with available lower-middle Cretaceous paleomagnetic results fro m Eastern China a paleolatitude difference of 11.5 degrees +/- 7.6 degrees is confirmed between Indochina and Easter China. It corresponds a significa nt southeastward displacement (>1000km) and accompanied with clockwise rota tion of 15 degrees-20 degrees of Indochina relative to Eastern China along the Red River fault since late Cretaceous time, which resulted from the col lision and penetration of India into Asia.