| dc.description.abstract | As an important conduit of sediment transportation in the southwest offshore Taiwan, Gaoping submarine canyon (GPSC) receives a huge amount of terrestrial sediment from the Gaoping river, which transports down to the Manila Trench. The sediment in the GPSC moves in the form of turbidity currents. The study area locates at the head of GPSC, source location of turbidity current showing the most vigorous turbidity current activity compared to the other parts of the canyon. Due to turbidity current erosion and mud diapirism intrusion, the geological structures and seafloor morphology are characterized by strong diversity and variability. Three high resolution sparker seismic profiles and sixteen deep-towed sub-buttom profiles, accompanied by side-scan sonar images were used in this study. After data processing, the sub-bottom profiler (SBP) sections were tied to wells close to coast, identifying the nine geological strata (sequences Sw1 to Sw9) west bank of GPSC and another eight strata (sequences Se1 to Se8) on the east bank.
Integration analysis between high resolution deep towed SBP, side-scan sonar and sparker seismic data with previous hydrogeological wells, we concluded that the paleo-Donggang river could be the dominant sediment supplier for the past thousands of years, despite the Gaoping river being the main one currently. In addition, the sediment could be transported through the canyon by both main canyon and tributaries on the east bank of the GPSC. Moreover, seismic acoustic blanking zones observed in the profiles near the coast could suggest sediment fluid accumulation in the aquifer strata, which may act as a conduit or channel for the seawater and ground water exchange near the coast of Pingtung Plain. On the west bank of the GPSC, two paleo-channels were formed by the erosion caused by coarse-grained sediment during the sea level regression approximately eight thousand years ago. The uplifting of mud diapirism in the area could generate linear seafloor relief and indirectly facilitate the erosion of the paleo-channels. Subsequently, the paleo-channels were filled up later. Additionally, many structures associated with sediment fluid were observed in the seismic profiles and side-scan sonar images. These structures are probably the authigenic carbonate, mud volcanos, mud diapirs, gas plumes, sediment fluid accumulation, etc., all of which could be related to the fluid supplied by mud diapirs in the depths. | en_US |