Magnetic-Polarity Stratigraphy of the Siwalik Group of the Shinghar and Surghar Ranges, Pakistan
Abstract
Four stratigraphic sequences were measured and sampled from the Shinghar and Surghar Ranges, Pakistan, for detailed magneto-stratigraphic studies of the fluviatile Neogene and Quarternary Siwalik Group. The samples were subjected to blanket thermal demagnetization at 500˚C. Some of the samples, particularly, those from the pale brown siltstone/claystone units, were further subjected to 600˚C to isolate the stable primary component of magnetization used to established the magnetic-polarity-reversal sequences. This sequence was correlated to the MPTS with the aid of fossils collected from the nearby Dawood Khel area (Hussain et al., 1977) and from the Shinghar Range during paleomagnetic sampling. This correlation suggests that deposition of the Siwalik Group in this area began during basal Chron 11 (11.8 m.y.B.P.) and continued till the late Matuyama Chron (0.85 m.y.B.P.). These studies indicate that the Siwalik sedimentation in this area started later than that of the Potwar Plateau.
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