Structural Evolution of Mud-Intrusive and Mud-Extrusive System in the Makran Accretionary Wedge: Tectonic Insights from the India-Arabia-Eurasia Triple Junction

The Makran Accretionary Wedge (MAW) in Pakistan and Iran, situated at the India-Arabia-Eurasia triple junction, provides a unique environment to investigate the mud-intrusive and mud-extrusive system (MIES) within an ultra-slow subduction zone. The MAW formed by northward subduction of the Arabian Plate beneath the Eurasian Plate, with convergence started during the Late-Cretaceous with a renewed phase since Middle-Miocene. This compressional regime has caused intense tectonic imbrication, deformation of pre-existing strata and formation of piggyback basins that preserved detailed records of tectono-sedimentary interactions. We utilized two-dimensional seismic reflection profiles, satellite imagery, and bathymetric data to map and characterize the geometry, spatial distribution, and connectivity of surface and subsurface mud-structures within the MAW. The MIES in this region form a complex plumbing system comprising mud-volcanoes (MVs), mud-diapirs (MDs), feeder-pipes, gas-chimneys, and mud-chambers etc., primarily sourced from the overpressured Makran Turbidite Deposits. These hemipelagic mud-rich deposits undergo compaction and tectonic loading, driving vertical and lateral fluid migration along structural conduits. Our study classifies the mud-structures into four types: (i) deep-sourced MVs, (ii) shallow-sourced MVs, (iii) multisource MVs, and (iv) multisource MDs. These structures typically exhibit conical, bifurcating, and Christmas-tree-like geometries with 75°–105° inclinations, commonly aligned with thrust-related anticlines, reflecting strong structural control. Active mud/fluid migration triggers coastal slope instability and normal faulting. Bottom-simulating reflectors further indicate ongoing fluid migrations and thermogenic gas generation within the MAW. The MAW, shaped by compressional tectonics and distinct sedimentary architecture, offers a valuable model for understanding mud-structures and tectonic processes in convergent margins worldwide.