| dc.description.abstract | The head of Gaoping Submarine Canyon (GPC) is connected with the river mouth of the Gaoping River. When extreme events such as typhoons and earthquakes, river floods and submarine landslides around the GPC may generate turbidity currents and transport sediments to the downstream of GPC and the deep South China Sea. The terrestrial sediments will spread from the river mouth and temporarily deposited on the Gaoping Shelf, upper Gaoping Continental Slope or at the head of GPC during fair weather conditions. Extreme events or the gas emission on the sea bed may resuspend the sediments or even trigger submarine landslides and turbidity currents move downward of the Gaoping Slope, and/or downstream of GPC. Nepheloid layers can also be generated and transport downward at the same time. Aside from the abundant sediment supply, the tectonic activities of the Manila accretional wedge form the complex topography in this area, which plays an important role in affecting sediment dispersal and the development of GPC. In this research, multi-beam bathymetry data, sediment cores, multi-channel seismic profiles and sub-bottom profiles are applied to analyze the relationship among the topography, sediment distribution and tectonic activities along the GPC.
The upper reach of GPC is a meandered channel without depositional levee. We call the margin of the canyon as the “canyon margin”. Hyperpycnites generated after the onshore floods were recorded at the head of GPC. After passing through the Xiaoliuqiu Bend, GPC develops in between the mud-diapiric ridges. Turbidity currents in the upper reach is restricted inside the canyon.
The canyon course of the middle reach is straight, the upper-middle reach is interpreted as erosive setting with bypassing turbidity currents. The platform on the west of the middle reach is dominated by muddy sediments, the turbidity currents are mainly restricted in the canyon as well. The only possible point of overspill is the south margin of the platform on the south of the middle reach.
The meandered lower reach consists of two segments. The upper-lower reach has depositional levees and experienced lateral channel migration. A lot of slump scarps scattered along both sides of the canyon. The height of canyon walls is relatively low, turbidity currents spill over the levees easily and deposited in the slope basins. Turbidites are found on a submarine ridge 170 meters above the surrounding seafloor and 15 kilometers away from the canyon margin. The lower-lower reach develops through a series of submarine ridges, initially meandered between two ridges, then cuts through few ridges and finally merges with the Manila Trench. | en_US |