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Radiometric dates of key rock units indicate that a remnant Late Mesozoic ocean of the Huatung Basin is still preserved today east of the South China Sea (SCS). We integrate regional geology with a Cretaceous oceanic basement in the vicinity of the Huatung Basin to reconstruct the Huatung Plate east of the Eurasian continent. Results of geophysical investigations, four expeditions of deep-sea drilling and a renaissance of regional geology allow us to propose a hypothesis that the mechanism responsible for the SCS opening was raised from strike-slip fault on the east. The hypothesis suggests that the SCS opening could highly relate to the strike-slip faults inherited from Late Mesozoic structures onshore–offshore the SE Cathaysia Block to develop rhombic-shaped extensional basins en echelon on the thinned Eurasian continental crust in the Early Cenozoic. It was followed by sinistral strike-slip movements along the boundary between the Eurasian Plate and the Huatung Plate driven by oblique subduction of the Huatung Plate to the northwest coupled with slab-pull force by southward subduction of the Proto-SCS to open up the triangle-shaped oceanic East Sub-basin in the Early Oligocene (33/34 Ma). The spreading ridge then propagated southwestward in the step-over segment between the Zhongnan-Lile and the Red River strike-slip fault systems to open the triangle-shaped oceanic Southwest Sub-basin by 23 Ma. The plate boundary fault was subsequently converted into the Manila Trench when the Eocene Sierra Madre arc of the Huatung Plate had moved from the south to its present latitude by the Middle Miocene. [ABSTRACT FROM AUTHOR]

The outer rise on the distal periphery of a subduction system is caused by emplacement of an accreted load onto the flexed oceanic lithosphere. By examining the bathymetry and free-air gravity anomaly data collected by satellite observations and marine reflection seismic data collected during the TAIGER project, we demonstrate the characteristics of the flexural outer rise seaward of the Manila Trench. The region of the outer rise on the westernmost periphery of the Manila subduction system is characterized by the positive free-air gravity anomaly seaward parallel to the Manila Trench and the morphological rise at the south of the Manila subduction system. A flexure simulation is performed based on the flexural profiles along the southern Manila Trench-outer system and the resulting effective elastic thickness values may provide an alternative aspect for the spreading rates of the South China Sea basin. Since both the western periphery of the Taiwan collision belt and Manila subduction belt are dominated by the strain regime of extension of flexural origin, it appears that the strain regime of flexural extension associated with the flexural forebulge of the Western Taiwan Foreland Basin to the north, and the strain regime of flexural extension associated with the outer rise seaward of the Manila Trench to the south are meridionally interconnected. This revised understanding of the strain regime of flexural extension origin west of the Taiwan-Luzon convergent belt provides an alternative point of view on the strain regime offshore SW Taiwan. [ABSTRACT FROM AUTHOR]

The Kenting Plateau has documented unusual topographic low relief surfaces that straddle the topographic crest of the northern Manila accretionary prism. It has a dimension of 35 km x 30 km and the water depth ranges from 60 m to 600 m. In the northern part, the plateau is comprised of an even surface having an average water depth of 500 m while in the SE part, there is an elevated flat area "Kuroshio Knoll", having a water depth of 60-70 m and a dimension of 3 km x 7 km. In order to document the submarine erosion, we have combined bathymetric data, Acoustic Doppler Current Profiler (ADCP) data and reflection seismic data with samples (gravity cores and gravels) collected from the plateau and its nearby perched basins. The southern part of the plateau comprises of hard rocks and relatively few mud diapirs as compared to the northern part which is abundant in mud diapirs along with a few mud volcanoes. One branch of the Kuroshio Current passes through this plateau and enters into the South China Sea. The thickness of the Kuroshio current is around 600 m. The velocity of the Kuroshio Current observed from the ADCP data on the Plateau surface reaches up to 0.5 m/s and up to 1 m/s on top of the Kuroshio Knoll, indicating erosion on the plateau surface, in particular on the Kuroshio Knoll. The P-wave velocity of the gravels collected from the plateau ranges from 3.2 - 4.5 km/s, implying the burial depth of parent rocks of the gravels in the range of 2.3-4 km below the seafloor. The parent rocks have been uplifted due to erosion of the plateau, as a result of isostatic rebound. The sand and silt contents of the cores collected in basins around the plateau show a decreasing trend in grain size away from the plateau, suggesting that submarine erosion is effective, thereby accumulating coarser sediments on the plateau and removing fine particles from the plateau, depositing in distal regions. Along with the erosion-induced isostatic rebound, the seismic lines in the plateau show the doubly-vergent thrusts on both sides of the plateau, which contribute towards the growth of the prism. [ABSTRACT FROM AUTHOR]

The Kenting Plateau is characterized by unusual low relief surfaces that straddle the topographic crest of the northern Manila accretionary prism off southern Taiwan at 400–700 m water depth. Multibeam bathymetric data, reflection seismic data, Acoustic Doppler Current Profiler (ADCP) data, surface grab samples, and sediment cores were collected in and around the Plateau to identify evidence of erosion in the Kenting Plateau and understand how the morphological evolution has been influenced by submarine erosion over geological time scales. The most distinctive feature on the Kenting Plateau is a 3 km × 7 km bean-shaped flat elevated platform (Kuroshio Knoll) revealed by multibeam bathymetry. Seismic data show almost no reflections beneath the seafloor and erosional truncations at the seafloor, especially in the Plateau's eastern half, evidencing widespread erosion. The P-wave velocity of the gravels recovered from the top of the Plateau ranges from 2.2 to 4 km/s. After comparing the velocity with the borehole data from nearby basin the burial depth of the parent rocks was found to be around 2 to 4 km below the seafloor, indicating that the parent rocks have been uplifted and gravels were formed due to erosion of the Plateau. The truncation of the seafloor shown on seismic sections suggests significant erosion on the Plateau. Sand content of the sediment cores decreases away from the Plateau, suggesting that sediment transport is effective in this area with high energy deposition, thereby accumulating coarse sediments on the Plateau and removing fine particles away from it. The presence of a dune field migrating northward of the Plateau, parallel to the Kuroshio Current also evidences active sediment transport in the area. Flow velocity of the Kuroshio Current observed from the ADCP data is very high, reaching up to 1.8 m/s on top of the Kuroshio Knoll (SE domain). We thus interpret that the observed intense erosion is caused by the Kuroshio Current, while the uplift of the Kenting Plateau is partially due to isostatic rebound caused by sediment removal through erosion and compression of the accretionary wedge. The higher sedimentation rate and coarser in grain size during sea level lowstand (20,000–12,000 yrs. BP) suggests that the erosion was more intense during the glacial period compared to that of deglacial period (< 12,000 yrs. BP) as seen from the MD97–2145 core. Submarine erosion is predominant throughout the Plateau, and it controls the geomorphology of the Plateau, especially the Kuroshio Knoll. • Ocean current plays an essential role in shaping ocean floor. • Observed Kuroshio Current in the Kenting Plateau is up to 1.8 m/s. • Intense Kuroshio Current shaped the Kuroshio Knoll into flat topped elevated surface. • The parent rocks of the gravels were buried 2 to 4 km below the seafloor. • Decrease in grain size and sand content away from the Plateau indicates the Plateau acts as source for the sand. [ABSTRACT FROM AUTHOR]