The magnetic polarity stratigraphy and correlation of the upper Siwalik sediments from the Bhittani Range, North West Frontier Province, Pakistan

Abstract

Two sections were sampled in the Bhittani Range, the first at Bain Pass consisting of 60 sites through 2200 m of section and the second along the North West Frontier Province Road north of Pezu consisting of 25 sites through 1000 m. Both sections are in rocks known to range in age from the late Pliocene and Pleistocene based on a vertebrate fauna of Pinjor age. After partial thermal demagnetization a series of magnetozones were established, ten at Bain Pass and six at Pezu, which can be correlated to each other and to the standard magnetic time scale. The sediments from the long section at Bain Pass span the time from the middle Gauss to the uppermost Brunhes Chron. The Jaramillo and Olduvai subchrons are present within the Matuyama Chron. A short normal magnetozone is present in the section preceding the Olduvai subchron which corresponds in age to the Réunion subchron. Based on the rate of sedimentation during lower Matuyama time which would be 0.95 m/1000 y for the Bain Pass section, the Réunion subchron would span at least 25 000 y. The section at Pezu Pass begins within the Olduvai and ends between the Jaramillo and the Brunhes/Matuyama boundary. The sedimentation rate determined at this section is 0.77 m/1000 y. The rate of sedimentation in this region was much higher than over comparable time spans previously determined from the eastern Salt Range. The folding of the Bhittani Range must have occurred less than 730 000 years ago, since Brunhes-age sediments have been deformed.