Magnetic polarity stratigraphy of Upper Siwalik Sub-Group, Soan Valley, Pakistan: implications for early human occupance of Asia

The results of a detailed paleomagnetic study of a 68 m section of Upper Siwalik sediments in the Soan syncline, northern Pakistan, are presented. A palaeolithic artefact and other pieces of struck quartzite were found in situ in a gritstone/conglomerate horizon near the base of the section. Incremental thermal demagnetization was used to remove later magnetic overprints in these sediments, since alternating field demagnetization was shown to be inappropriate. With the exception of the lowest stratigraphic level, the Upper Siwalik sediments examined in the Riwat section show reverse polarity magnetization. The declination values are consistent with a 16° (±4°) counterclockwise rotation of the Soan syncline tectonic block since deposition of the sediments. On the basis of the palaeomagnetic analyses and the tectonic and stratigraphic context of the section, our current best estimate of the age of the artefact-bearing horizon is 2.0 ± 0.2Ma.