Geotectonic Evolution of Kohistan
Abstract
Kohistan Zone is located on the north-western tip of the Himalaya and constitutes a tectonic unit in the Indo-Pakistan-Eurasia suture zone between Himalaya and Karakoram. Its characteristic nature distinguishes it from the surrounding well known geological provinces of Hazara and Kashmir on one side and Gilgit, Baltistan and Chitral on the other side. Most of Swat and Dir belong to Kohistan along with the southern part of Gilgit, Chitral and northern Hazara. The Kohistan Zone is bounded by two megashears: the Hini-Chalt-Yasin-Drosh fault lying to the north, which extends into Baltistan through Tissar-Hashupa in Shigar Valley and Machelu in Shyok Valley. Another is recently deciphered Main Mantle Thrust traversing the southern periphery of Kohistan. In addition, there exists a series of late thrust tectonic features, the two prominent among them being the Hazara syntaxial bend located on the south and a dominant Naze of Nanga Parbat - Haramosh massif on the northeast, which was considered by Wadia to be a horst of the Indian Peninsula, but the author interprets it as a transverse antiform fold. These major tectonic features, located in the vicinity of the Kohistan Zone, have played a major part in the evolution of its structural history. A chronological account of various tectonic episodes is presented in this paper.
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