Understanding the interrelations between accretionary wedge imbrication, large-scale shale diapirism, and incoming sediment dynamics in subduction collisional environments is crucial for unraveling the intricate processes governing the evolution and deformation of subduction zones. The Makran subduction collisional zone in the Northern Arabian Sea stands as a paradigmatic illustration of low-angle subduction complex worldwide formed by the convergence of Arabian plate underneath Eurasian plate in the Early Cretaceous, followed by Middle Miocene renewed subduction. In this study, we adopted seismic sequence stratigraphic analysis, 3D structural geological modeling, petrophysical evaluation, overburden gradient, overburden pressure, fracture pressure gradient analyses to comprehend the interrelations of wedge imbrication, large-scale shale diapirism, and incoming sediment dynamics. Our results reveal that the substantial tectonic shortening, imbricate thrust faulting triggered by Middle Miocene renewed subduction, coupled with a continuous influx of sediments, synergistically contributed to the remarkable accumulation of sedimentary succession (∼7.5 km) and subsequently generated regional shale diapirs due to high fluid overpressure from under-thrusted sediments. The formation and deformation mechanism of imbricate structure and fluid overpressure within Makran subduction collisional zones are controlled by plate convergence (obliquity and velocity) , the material properties of the wedge and the décollement (friction, cohesion, and deep fluid overpressures), isostatic response (uplift and subsidence), and external surface processes, including erosion and sedimentation. The tectonic reconstruction and deformation mechanisms model shows four phases, e.g. (1) initiation of subduction and accretionary wedge formation in Eocene, (2) N-dipping imbricate thrust faults and large-scale shale diapirs triggered by Middle Miocene renewed subduction, (3) development of large-scale shale diapirs in Middle Miocene to Pliocene together with syn-deposition, (4) thrust deformation ceases, development of post depositional system, large-scale shale diapirs-induced structuration, formation of shallow fluide scape pipes. This research enhances our understanding of subduction zone dynamics shedding light on the complex processes shaping subduction collisional environments.
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