Partition between collision and subduction accretionary prisms along an inherited transcurrent fault zone: New insights on the Taiwan fold and thrustbelt

A new geotectonic framework of the Taiwan orogen is presented in accordance with the hypothesis of an oblique arc-arc collision. The colliding Luzon a re is physically connected to the eastern Coastal Range in which a subducti on complex remnant is preserved and backthrust with intra-are sediments in a small retroforeland basin. A southern and extinct extension of the Ryukyu are is characterized in western Taiwan. It displays a duplex structure (Ta nanao and Backbone horses and Lishan triangle zone) between a buried floor thrust located in the are crust and a roof thrust developed in the are cove r (Hsuehshan Range and South Backbone Range). Westward the basal thrust cli mbs in the sedimentary series of the western proforeland (Foothills and Hen gchun Peninsula) and dies out in a buried tip line. The northern part of th e orogen, including all the Tananao are core, is shown as an intra-oceanic- continental are-are collision belt characterized by an unroofed duplex culm ination above a leading floor thrust and both proforeland and retroforeland basins. The southern part, which displays a roof thrust sequence above a b uried duplex, is shown as an accretionary prism built in a transition zone between continent and oceanic subduction (transition from the Asian contine ntal crust, including the former Ryukyu are, to the oceanic Old Philippine Sea crust). The partition is believed to be induced by a deep intracontinen tal transcurrent fault zone able to influence the difference in shortening, duplex pattern, and leading thrust depth. The evolution was controlled by the Ryukyu subduction (backarc extension, are magmatism extinction, and coo ling and intra-arc collapse) until the early middle Miocene (around 15 Ma) and then it was controlled by the Luzon are progression (continental subduc tion, collision, indentation, and hinterland uplift and frontal thrust prop agation).