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The northeast Taiwan margin provides an excellent example of the route of sediment flux from a small mountainous river, the Lanyang River, to a deep-sea basin, the Southern Okinawa Trough (SOT), via a very narrow（8–14 km in width）Ilan Shelf at different time scales. Based on seismic and sub-bottom chirp profiles and onshore borehole and offshore core data, we identify three echo types on the Ilan Shelf that delineate sheets of sediment, mass movement deposits, and echoes indicative of igneous activity. By recognizing lithofacies and seismic facies changes, the Last Glacial Maximum Unconformity and maximum flooding surface are correlated in onshore cores and offshore reflection seismic profiles. With the aids of sequence stratigraphic analysis, the postglacial sedimentation rates on the Ilan Shelf are estimated to range from 0.04 to 1.53 cm/yr. Considering its sediment budget in a source-to-sink system, the Ilan Shelf can be regarded primarily as a temporary trap for fluvial sediment discharged from the Lanyang River. Overall, it has trapped at least 50% of the discharged sediment during the Holocene, and the bulk of sediment was transported, primarily via mass movement to SOT. We deduce that earthquake-induced faulting, axial incision in the channel, and retrogressive failures appear to be triggers for mass wasting, which then combined with channel transport, can play leading roles in rapid downslope transportation to the trough. This inference is indicated by high deposition rates in the western end of SOT and widely distributed mass transport deposits observed in the shallow strata of SOT. We found that the deep strata of SOT are deformed by normal faults, indicating that the sediment accommodation space is structurally controlled by the active back-arc extension. This study documents that frequent typhoons and flooding events, together with strong tidal currents, are significant agents of sediment input over the short term. In contrast, earthquakes and volcanic events occasionally affect sediment dispersal from the Ilan Shelf to SOT. • We firstly present sediment dispersal patterns of the Ilan Shelf since the Last Glacial Maximum. • Combining seismic and well data onshore and offshore, we exhibit Ilan Shelf as a buffer zone temporarily storing sediments within the S2S system. • Mass wasting processes combined with channel transport play leading roles in rapid downslope sediment transportation from the Shelf to SOT. • Ilan Shelf plays as a temporary trap for at least 50% of fluvial sediment discharged from the Lanyang River during the Holocene. [ABSTRACT FROM AUTHOR]

Abstract: Distribution and architecture of slope basins across a continental slope vary as a consequence of accommodation forming, sediment dispersal rates, canyon cutting, sediment filling and different sediment transporting mechanisms. The area offshore Southwestern Taiwan is generally recognized as having active tectonics and high sediment deposition rates. In the Gaoping Slope, slope basins are formed by the developments of folds, faults and diapiric intrusions. Portions of the sediments discharged from the Taiwan mountain belt have been trapped in these basins in the Gaoping Shelf and Gaoping Slope. The rest of the sediments were transported to deep sea areas through submarine canyons. This complex system of folds, faults, diapirs, slope basins, submarine canyons, and sediment deposits has also readjusted the morphology of the Gaoping Slope. This study examines the linkage between accommodation spaces of tectonic and sedimentary processes in the Gaoping Slope through seismic facies analysis. Four seismic facies which include convergent-symmetrical facies, convergent-baselapping facies, chaotic facies, and parallel and drape facies, and different deposition patterns have been recognized in the Gaoping Slope basins. The thick mud layers which are regarded as the source of diapiric intrusions are first observed beneath the basin. Strata records show that the accommodation spaces in various slope basins have increased or decreased during different stages of basin evolution. Because of the competition between regional tectonism (accommodation space variations) and sediment routing distance from provenance to depository (sediment input variations), most under-filled basins lie in the lower slope domain in the Gaoping Slope, but also in the upper slope domain east of the Gaoping Submarine Canyon. This observation suggests that in the inner Gaoping Slope west of the Gaoping Submarine Canyon, sediment deposition rate is higher than the basin subsidence rate, the topography of the upper slope domain there is “healed”, and most sediments are overfilled in the slope basins now. Besides the sequential steps of sedimentary disposal in the filling-and-spilling model, we have also observed evidences which indicate that mass movements and submarine canyons in the area have significantly changed the sediment dispersal patterns in the slope basins of the Gaoping Slope. We suggest that although filling-and-spilling is a key sedimentary process in the Gaoping Slope, tectonic activities, mass wasting events and canyon feeding processes have diversified sediment transporting mechanisms from the inner to outer slopes in the area offshore Southwest Taiwan. [Copyright &y& Elsevier]

Newly compiled bathymetry, sub-bottom profiling and seismic data are used to illustrate seafloor morphology, submarine canyon networks and stratigraphic framework in Huatung Basin (HB) and an adjacent sub-basin, named as East Luzon Arc Basin offshore east Taiwan. Based on seismic facies characteristics and isopach maps, three major stratigraphic sequences are recognized and we suggest that they could be resulted from pre- and syn -Taiwan arc-continent collision. Based on the sediment thickness and sedimentation rates, ages of the HB strata could be estimated. Pelagic sediments formed the lower HB sequence which follows the HB basement reliefs since 50–102 Ma. Then, the initiation of Taiwan orogen and Luzon Arc volcanic activities changed the deposition pattern after 5 Ma, and mass transport deposits developed in middle HB sequence. After rapid uplift of the Taiwan mountain belt since about 1.5 Ma, complex canyon-levee systems and thick strata formed the upper sequence in the northern HB. In contrast, sediment thickness is thin and no submarine canyon developed in southern HB. The seafloor in South Huatung Basin is flat, except in its eastern part where couple basement ridges appeared. In North Huatung Basin, canyon-levee complex and sediment waves are the most distinct morphological features in the drainages of two submarine canyons. We propose a three-stage process for sediment wave development: (1) sediment gravity flow can initiate a base of sediment wave; (2) wavy geometry begins to develop; (3) sediment waves continuously aggrade due to overbank sediments in the canyon-levee system. This study presents the evolution of sedimentary processes in a deep-sea basin and how the deposition patterns were affected by the convergent tectonics. • We report stratigraphic framework and sediment waves of Huatung Basin firstly. • Major stratigraphic sequences above oceanic basement of Huatung Basin are mapped. • Geological evolution of sedimentary processes & sediment wave fields in the basin are presented. • The age of Huatung Basin is estimated based on calculated sedimentation rates & sediment thickness. [ABSTRACT FROM AUTHOR]