Magnetostratigraphy and Sedimentology of the Hazara Intermontane Basin, Pakistan
Abstract
The Hazara Intermontane Basin (named herein) is nestled within the Hazara Hill Ranges located on the hanging wall of the Main Boundary Thrust. The Havelian Group represents the fill of this basin and consists of unconsolidated silts, sands and gravels. Paleomagnetic investigations of the silts consisted of both thermal and alternating-field demagnetization experiments for nearly all of the sites of the two measured and sampled stratigraphic sections sampled. All sites are normally polarized and correlated with the Brunhes Chron (0.73Ma to present). Sedimentological analysis shows that the Havelian Group was deposited as a sandur, a large, silt-laden plain of glacio-fluvial sediments consisting of fluvial gravels and sands, and windblown loess. It is interpreted that this sandur emerged from valleys of the Hill Ranges which contained Alpine-type glaciers in their upstream reaches. Minimum sedimentation rates determined for the Havelian Group range from 0.07 to 0.27mm/yr, and are remarkably similar to those determined for the Potwar loess (Rendell, 1988). No evidence was found to suggest that the Havelian Group was deposited as a result of tectonic activity in the foredeep.
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