Evolution of Makran Accretionary Prism Structure and Development of Stratigraphic Sequence

The Makran accretionary prism is located in the northern Arabian Sea, at the junction of the Eurasian Plate, the Arabian Plate, and the Indian Plate. The accretionary prism was formed by the northward subduction of the Arabian Plate beneath the Eurasian Plate, which began in the late Cretaceous period and entered the formal development stage in the Oligocene. The current plate convergence rate is about 3.65 cm/yr in the west and 4.2 cm/yr in the east, with a total sedimentary thickness of over 7000 m within the accretionary prism. Based on seismic data from the sea and stratigraphic comparisons from the land, the Cenozoic strata in the sea are divided into three sets of sequences: Sequence III (34-11.6 Ma) is characterized by interbedded mudstone and Makran sandstone from Himalayan sources, controlled by gentle thrust faults, and extensively developed mud diapirs, forming the main skeleton of the accretionary prism, corresponding to the Hoshab Panjgur Formation of the Oligocene to Middle Miocene in the Pakistani land; Sequence II (11.6-5.3 Ma) is a piggyback basin filling deposit, mainly composed of coarse-grained sediments, developed in conjunction with thrust faults. The sedimentary center is located in the north and the thickness decreases southward, corresponding to the Parkini Formation of the Upper Miocene in the continental domain; Sequence I (5.3 Ma present) shows a prism-shaped progradation, with continuous southward migration of continental shelf slope breaks, and the development of numerous submarine canyons, landslides, and semi oceanic sediments, corresponding to the Hinglaj Ormara Formation of the Pliocene Quaternary in the continental domain. During the Late Miocene to Early Miocene, a series of early formed and strongly active thrust faults developed; Since the Neogene at night, shallow normal faults with late development and weak activity have mainly formed in the area of the accretionary prism. During the Cenozoic era, the subduction front continued to move southward, and the northern thrust fault was deeply buried and developed gravity slip. Fluid leakage and mud volcanoes were widely developed. The joint control of subduction geometry, sedimentary flux, and plate boundary action provides important examples for studying the geological evolution and resource potential of oceanic accretionary prisms.