Interaction between flow regime and sedimentation in the upper reach of Gaoping submarine canyon, offshore SW Taiwan
Reporter: Shih-Lin Tseng
Abstract
This research examines the influence of a submarine canyon on the dispersal of sediments discharged by a nearby river and the sediment movement on the inner shelf. The study area covers the river mouth of the Gaoping river (KPR), shelf, and submarine canyon (KPRSC) located off SW Taiwan on a wave-dominated micro-tidal coast. Three comprehensive 1-month field experiments were carried out in 2000, 2002 and 2004 during the flood seasons of the river. Objectives of this study are to investigate particle dynamics from a source-to-sink perspective in the KPRSC with the emphasis on the effect of particle size on the transport, settling, and sedimentation along the pathway. Methods and tools for this research include collecting particle samples, concurrent hydrographic profiling, water sampling and sediment box coring. Particle samples from sediment traps were analyzed for mass fluxes, grain-size composition, total organic carbon (TOC) and nitrogen (TN), organic matter (OM), carbonate, biogenic opal, polycyclic aromatic hydrocarbon (PAH), lithogenic silica and aluminum, and foraminiferal abundance. Samples from box cores were analyzed for grain-size distribution, TOC, particulate organic matter (POM), carbonate, biogenic opal, water content, and 210 Pb ex . Water samples were filtered through 500, 250, 63, 10 μm sieves and 0.4 μm filter for the suspended sediment concentration of different size-classes. Results show that the river and shelf do not supply all the suspended particles near the canyon floor. As suspended particles settle through the canyon, their size composition shows a downward fining trend. Correspondingly, the substrate of the canyon is composed largely of hemipelagic lithogenic mud. Sediments core analysis show post-depositional disturbances such as hyperpycnic and turbiditic deposits on the canyon floor. These deposits indicate the occurrences of erosion and deposition related to high density flows might be an important process in submarine canyon sedimentation.
References
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