Morphology, seismic characteristics and development of the sediment dispersal system along the Taiwan–Luzon convergent margin

Abstract

The sediment dispersal system along the convergent margin between Taiwan and Luzon links the terrestrial and shallow marine sediments from the source areas nearby Taiwan orogen to the ultimate sink in the northern Manila Trench. Using seismic reflection profiles and bathymetry mapping we determine three distinct morpho-tectonic features of the Penghu Submarine Canyon, deep-sea Penghu Channel and oceanic Manila Trench which are linearly interconnected to form a longitudinal sediment route. Seismic profiles show characteristic features of truncated strata along canyon walls and cut-and-fills in canyon bottom. Deformed and uplifted bathymetric ridges and troughs and volcanic intrusions with unstratified and chaotic seismic facies are associated with the Penghu Channel. The seismic facies of the trench wedge are characterized by sub-horizontal and conformable layers of sediment stacking upwards to the trench floor. The sediment wedge adjacent to the inner lower slope is deformed to blind folds and thrust faults as precursors of the accretionary prism. The most prominent seismic characteristics is wide-spread undulating reflectors on the seafloor along the west edge of the sediment dispersal system and the toe of the South China Sea Basin floor, suggesting a large sediment wave field with a turbidity currents origin. The location, orientation and geometry of this sediment routing system are mainly controlled by underlying tectonics in progressive changes from arc–continental collision in transition to subduction. The deep-sea Penghu Channel is formed by compression in transitional zone of the North Luzon Ridge region, neither subduction nor channel erosion. The sediments in northern Manila Trench are mainly transported by turbidity currents via the upslope deep-sea Penghu Channel and Penghu Canyon and trench axis is filled up to a flat-floor trench wedge without sediment ponding. A four-stage development of sediment dispersal system in Taiwan–Luzon convergent margin from Early Miocene to present is proposed. It consists of (1) initiation of the Manila Trench around 22 Ma during subduction stage, (2) formation of the deep-sea Penghu Channel about 6.5 Ma in transition stage, (3) submarine canyons forming in slopes southwest of Taiwan during incipient collision around 0.4 Ma, and (4) in the present late collision stage the modern Penghu Canyon developed.