Reconstructing Taiwan from the Cretaceous to present

Abstract:

We present a revised analysis of the plate tectonic framework of Taiwan since the Late Cretaceous, a time when subduction polarity was still opposite to what is observed at present (westward subduction of the Pacific Plate, as opposed to eastward subduction of Eurasia at present). We place our reconstructions within a global plate tectonic frame, and discuss the consequences of subduction zone reversal for the evolving passive margin. Based on existing models (Seton et al. 2012, Zahirovic et al. 2014), we show that clockwise rotation of the Philippine Sea Plate results in complete subduction of the Proto South China Sea. This eastward-directed subduction results in a propagating subduction polarity flip along the Chinese passive margin, changing from westward-directed Pacific subduction, to present day eastward Eurasian subduction. This is independent of northward subduction of the Philippine Sea Plate underneath Eurasia in the Taiwan area. Our reconstructions yield a new model for the collisional history of Taiwan, which reconciles the pre-collisional architecture with the metamorphic conditions of the Cenozoic orogeny, and makes predictions about timing of peak-pressures, as well as the timing of collision and present subduction zone reversal. We argue that Taiwan is the result of a first collision between the Luzon Arc and a continental fragment, which rifted off the passive margin either during opening of the Proto South China Sea, or later, during opening of the South China Sea, and a second collision with the Chinese Passive margin proper. We constrain timing of collision to 6.5 and 3.5 Ma, respectively. An interesting implication of our model is that the first collision does not necessarily propagate along strike, which may explain facies distributions in the foreland, as well as uniform metamorphic conditions in the Tananao Complex. The orogeny potentially propagates from north to south only since its recent collision at 3.5 Ma.