NEOGENE MAGNETIC POLARITY STRATIGRAPHY OF SOME FLUVIATILE SIWALIK SECTIONS, NEPAL

The magnetostratigraphy of five new sections through the Neogene Siwal ik Group of Nepal is presented. Rock magnetic experiments and detailed thermal demagnetization experiments prove that haematite is the carri er of a primary DRM or a PDRM. After stepwise thermal demagnetization of specimens from all sections, directions of characteristic remanent magnetization were obtained. The results show a positive reversal test and exhibit inclination errors of about 20 degrees. Due to gaps in ex posures and extremely variable demagnetization behaviour of the haemat ite-bearing sediments, the resulting polarity sequences are poorly def ined for some parts of the sections. However, double-sampled parts of some sections yield similar results. A correlation with the Surai Khol a section (Appel, Rosler & Corvinus 1991) is proposed, based on rock m agnetic parameters. AMS results from three of the sections prove the e xistence of primary sedimentary magnetic fabrics in these sections wit h systematic orientations of minimum and maximum susceptibility axes. Correlation with a standard polarity timescale indicates that the ages of all new sections lie within the age limits of the Surai Khola sect ion.