Indo-Eurasian Plates’ Collision and the Evolution of Pak-Iran Makran Microplate, Pishin-Katawaz Fault Block, Porali Trough and the Axial Belt
Nusrat K. Siddiqui¹ and Ishtiaq Ahmed Khan Jadoon²
¹Consulting Geologist, 112/II, Street-32, Phase-VI, D.O.H.A., Karachi
²Department of Earth Sciences, COMSATS Institute of Information Technology, Abbottabad
Plate tectonics, as shown by the animation of Shell International, represents emergence of a microplate to the west of the northward drifting Indian Plate (IP) by Early Eocene, which was subsequently accreted to the Eurasian Plate (EP) to occupy its southwestern margin. This microplate is proposed to be designated as Pak-Iran Makran Microplate (P-IMM). By Early Eocene, the P-IMM, the Central Iranian/Lut and the Afghan microplates kept pace independently with the northward drifting Indian Plate and later coalesced with the EP. The P-IMM that represents the south-western block of the EP stretches from Zendan Fault in Iran to Ornach-Nal Fault in Pakistan. The eastern part of P-IMM is represented by the Makran Accretionary Prism (MAP) in Pakistan. The northern border of P-IMM coincides with the Jiroft Fault in Iran, which is interpreted to extend eastward along the northern margin of the MAP and most likely truncates/joins the Chaman Fault.
By Oligocene, the converging IP and the Afghan microplate bordered a NE-SW oriented sea, with the presence of P-IMM in the SW. This ‘Remnant closing Sea’ (Neo-Tethys) received Oligocene-Miocene flysch from the NE, and is now represented by the Pishin-Katawaz Fault Block (P-KFB). This entire set-up was exposed to a synchronized dynamic environment. The plates were converging, the Oligocene-Miocene depositional trough was shrinking, the Axial Belt was evolving, Porali Trough was opening as the IP was rotating anti-clockwise, followed by the post-Miocene E-W compression in a transgressional setting. In this setting, the initially NE-SW oriented Pishin-Katawaz trough was stretched and compressed, sandwiched between the IP and the Afghan microplate. The left-lateral Chaman Fault (CF) and its northern extension, the Moqur Fault in Afghanistan mark the boundary between Afghan microplate and the Pishin-Katawaz Fault Block. In SW the Pishin–Katawaz deposits are in geological continuity with the P-IMM through a stretched narrow zone. The eastern margin of P-KFB is faulted, all along, against the Axial Belt. The Axial Belt itself is proposed to represent Permian? to Eocene sedimentary rocks interbedded with volcanics and coloured mélanges and imbricated as a result of Himalayan orogeny. This entire kinematic and dynamic history is spread over a period of at least 55 million years (Ma).
AAPG Search and Discovery Article #90160©2012 PAPG/SPE Annual Technical Conference, 3-5 December 2012, Islamabad, Pakistan.