Numerical experiments on the depositional process of turbidites in the southern part of Okinawa Trough based on cores from Expedition KH-21-3
Abstract
Okinawa Trough is an actively rifting back-arc basin and an important area for examining the tectonic history of Ryukyu subduction zone. Past studies showed that the primary sources of sediment deposition in the southern part of Okinawa Trough were Taiwan and East China Sea continental shelf. The main process of sediment transportation to Okinawa Trough was turbidity currents in addition to hemipelagic sediment transport. Estimating sediment flux from Taiwan and local sediment input from volcanic arcs into this region is vital for understanding the development of Okinawa Trough and the temporal changes in orogenic activity in Taiwan. However, the scale and source of turbidity current events related to the depositional process within the region are still unclear. The KH-21-3 expedition surveyed the southern part of Okinawa Trough, and four piston cores were obtained (Jan. 23th, 2021 to Feb. 8th, 2021). A visual examination of the cores found that turbidites from one core contained volcanic ash while the other three did not, which indicates that the source of the former was potentially the Ryukyu Arc, while the source of the later three were most probably Taiwan. This information can be used as a constrain to the inundation area of turbidity currents from Taiwan. To examine the turbidity current events that produce the inundation area observed, we conducted numerical experiments using a 2D shallow water equation model considering sediment transport of multiple grain-size classes. The results indicated that flow duration of over 30 minutes. Flow concentration of above 0.01 was necessary for deposits to reach the area of interest. To attain this condition, sediment volume provided to a turbidity current should exceed 240,000 m3 for a single event. Although still in the preliminary stages of the investigation, such estimates of sediment supply may provide constraints on reconstructing the uplift-denudation process in Taiwan.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMEP35D1349C