Structural evolution from Paleogene extension to Latest Miocene-Recent arc-continent collision offshore Taiwan: comparison with on land geology

Abstract

Marine structures observed in seismic profiles across the NE South China Sea–Taiwan Strait–Luzon Arc region show that they are comparable to those observed onshore Taiwan. The Hanjiang Depression and Dongsha Uplift off the SE China coast extend to the Penghu Basin and Penghu Platform, respectively, in the Taiwan Strait, while the Tainan Basin in the south of Penghu Platform is connected to the Chaoshan Depression south of the Dongsha Uplift. The Hanjiang Depression and the Penghu Basin are composed of Paleogene syn-rift sequences on the Mesozoic basement and are unconformably overlain by Neogene post-rift strata. Similar successions are found underneath the coastal plain or have been thrust up as a fold-and-thrust belt bordering the Peikang Basement High onshore central Taiwan.East of the Manila Trench, off southwestern Taiwan, parts of the Tainan Basin are thrust into the submarine syn-collision accretionary wedge (the fold-and-thrust Kaoping Slope) in the initial arc-continent collision zone. They have also been exposed in the fold-and-thrust Western Foothills south of the Peikang Basement High in southern Taiwan during an advanced stage of arc-continent collision since the Late Pliocene. Further east, the pre-collision accretionary wedge (the Hengchun Ridge) shoals northward to the Hengchun Peninsula, with Late Miocene turbidites unconformably overlain by Plio–Pleistocene shallow-marine slope basin sequences. In the arc domain, east of the arc-prism boundary fault, the western forearc sequences in the North Luzon Trough are deformed. Two normal-faulted intra-arc basins occur on the eastern part of the Lanhsu Island in the Luzon Arc. The scenario of the deformed forearc sequences and the development of the two intra-arc basins in the initial arc-continent collision zone are analogous to the Lichi Mélange–Taiyuan Basin and the intra-arc basins in the southern Coastal Range, eastern Taiwan.Additionally, the lateral change in the marine structure from the passive Asian continental margin to the Manila subduction system is comparable to the temporal evolution from Paleogene normal faulting, through Neogene subduction, to Latest Miocene-Recent arc-continent collision observed onshore Taiwan.