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Abstract: Through a large-scale examination of the morpho-sedimentary features on sea floors in the Taiwan–Luzon convergent margin, we determined the main sediment dispersal system which stretches from 23°N to 20°N and displays as an aligned linear sediment pathway, consisting of the Penghu Canyon, the deep-sea Penghu Channel and northern Manila Trench. The seafloor of South China Sea north of 21°N are underlain by a triangle-shaped collision marine basin, resulting from oblique collision between the Luzon Arc and Chinese margin, and are mainly occupied by two juxtaposed slopes, the South China Sea and Kaoping Slopes, and a southward tilting basin axis located along the Penghu Canyon. Two major tributary canyons of the Formosa and Kaoping and small channels and gullies on both slopes join into the axial Penghu Canyon and form a dendritic canyon drainage system in this collision marine basin. The canyon drainage system is characteristic of lateral sediment supply from flank slopes and axial sediment transport down-canyon following the tilting basin axis. The significance of the collision marine basin in term of source to sink is that sediments derived from nearby orogen and continental margins are transported to and accumulated in the collision basin, serving as a temporary sediment sink and major marine transport route along the basin axis. The comparison of the Taiwan–South China Sea collision zone with the Papua New Guinea collision zone of the western Solomon Sea reveals remarkable similarities in tectonic settings and sedimentary processes that have resulted in similar sediment dispersal systems consisting of (1) a canyon drainage network mainly in the collision basin and (2) a longitudinal sediment transport system comprising a linear connection of submarine canyon, deep-sea channel and oceanic trench beyond the collision marine basin. [Copyright &y& Elsevier]

Abstract: Analysis of three-dimensional seismic data and multibeam data from the Pearl River Mouth Basin in the northern South China Sea, reveals numerous focused fluid flow features and associated widespread shallow gas from 500m to 2000m water depth. Shallow gas is usually indicated by acoustic anomalies, such as enhanced reflections, acoustic turbidity, and acoustic blanking. Two types of tectonically and stratigraphically controlled fluid flow related systems are identified. The first type can be observed in the deep strata, including gas chimneys, mud diapirs, mud volcanoes, pipes, and large normal faults, which are usually located over basement highs and are related to overpressure mainly caused by gas generation. The focused fluid flow structures serve as pathways for upward migration of thermogenic fluids from source rocks or gas reservoirs. The second type is a shallow fluid flow system consisting of minor normal faults, migrating canyons, mass transport deposits, contourite, and pockmarks. The minor faults and migrating canyons provide pathways for fluids of thermogenic origin transported by the deep fluid flow system and of biogenic origin generated in the shallow succession. The mass transport deposits and contourite mainly serve as caprock. Small-scale fluid seepage is observed at the modern seabed expressed as pockmarks located above shallow gas accumulations. The distribution of shallow gas is controlled by the combination of these two systems. The focused fluid flow features and shallow gas are poorly studied in the study area and we propose a 3D model of focused fluid flow and shallow gas distribution that can be used more widely in other passive and active continental margins. Our results are important to the understanding of resources (hydrocarbon and gas hydrate) exploration in such a petroliferous basin and they must be taken into account when assessing seabed stability. [Copyright &y& Elsevier]