Kahi mélange complex in Kurram and Waziristan, NW Pakistan: An integrated approach for tectonic implications to India–Afghan suturing

Abstract

The Kahi mélange complex in the Waziristan and Kurram sector (N–W Pakistan) is one of the several Neotethyan ophiolite–mélange complexes exposed along the westernmost margin of the Indian plate, preserving significant information on pre, syn and post–collision tectono–stratigraphic evolution of collision tectonics between the Indian plate and the Afghan block. It consists of highly dismembered ophiolitic and sedimentary units. Petrographic and field observations of mafic and ultramafic rocks within the ophiolitic unit, reveal a complete, but dismembered ophiolite suite similar to the Waziristan Ophiolite (WO) to its southwest. The sedimentary units consist of syn–orogenic deposits, turbidites and slope sediments of Campanian age as constrained by the Late Cretaceous radiolarians (Stichomitra communis Squinabol) and planktonic foraminifera (Rodotruncana Calcarata). From the structural point of view, the dismembered ophiolitic units represents the highest tectonic edifice. It’s overthrusting onto the Campanian sedimentary unit constraints the onset of the collision between the Indian plate and Afghan block to the Late Cretaceous. The subsequent obduction of combined ophiolite–sedimentary units over the brecciated Late Paleocene Lockhart Formation of Indian plate margin constraints the time of the end of the collisional stage. The unconfirmable deposition of the marine Patala Formation, Late Paleocene–Early Eocene in age, above the Kahi mélange complex documents the closure of Neotethys in the Early Eocene. In conclusion, our findings document that the Kahi mélange complex represents a typical polygenetic mélange formed by the superposition of two different dismembered units (the ophiolitic and the sedimentary units) coupled as a result of at least two tectonic events in a subduction–accretion setting related to the collision between the Indian plate and the Afghan block.