MAGNETOSTRATIGRAPHY OF THE MIOCENE PLEISTOCENE SURAI-KHOLA SIWALIKS IN WEST NEPAL

Magnetostratigraphic age dating has been carried out on sandstones of a well-exposed continuous 5500 m thick Miocene-Pleistocene section in the Surai Khola area (West Nepal). The section is situated in the Siwalik Range which consists of molasse sediments from the Himalaya. Progressive demagnetization and isothermal remanence experiments prove that haematite is the carrier of the characteristic remanent magnetization (ChRM) throughout the entire section. The final polarity sequence is based on 436 samples, of which 233 have normal and 203 reverse polarity. Antiparallel mean directions of the normally and reversely polarized samples indicate that the ChRM is of primary origin. Comparison of the polarity sequence with a standard polarity time-scale yields a time period for the section between chron 1r or chron 2r (Matuyama) and probably chron 5AB (between 1-2 Myr and about 13 Myr).