[3ch101-11] R13 [Regular Session]Subduction zones and on-land accretionary complexes

[R13-O-11] Examining the characteristics of turbidites in the southern part of Okinawa Trough using numerical experiments based on cores from Expedition KH-21-3

*Zhirong Cai Cai¹, Hajime Naruse¹, Ken Ikehara², KH-21-3 Shipboard Scientists (1. Department of Geology and Mineralogy, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, 2. Institute of Geology and Geoinformation, National Institute of Advanced Industrial Science and Technology)

Keywords:Turbidity Current, Turbidite, Numerical Experiment

Okinawa Trough is an actively rifting back-arc basin and an important area for examining the tectonic history of the Ryukyu subduction zone (Arai et al., 2017). Past studies showed that the main sources of sediment deposition in the southern part of Okinawa Trough were Taiwan and the East China Sea continental shelf (Milliman & Kao, 2005; Katayama, 2007). The main process of sediment transportation to the Okinawa Trough was turbidity currents in addition to hemipelagic sediment transport. Estimating sediment flux from Taiwan as well as local sediment input from volcanic arcs into this region is important for understanding the development of the 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 is still unclear. The KH-21-3 expedition surveyed the southern part of Okinawa Trough and four piston cores were obtained. Each core contained more than one turbidite unit. In order to better understand the origin and scale of turbidity current events that resulted in turbidites in the southern part of Okinawa Trough, we conducted a 2D numerical experiment of turbidity current events using a shallow water equation model that reproduced turbidites in borehole cores. This presentation will contain a preliminary report of the characteristics of turbidites within the cores obtained from KH-21-3 and results from numerical experiments. Reference: Arai, R., Kodaira, S., Yuka, K., Takahashi, T., Miura, S., and Kaneda, Y. (2017), Crustal structure of the southern Okinawa Trough: Symmetrical rifting, submarine volcano, and potential mantle accretion in the continental back-arc basin, J. Geophys. Res. Solid Earth, 122, 622– 641, doi:10.1002/2016JB013448. Katayama, Hajime (2007): Budget and transport process of terrigenous sediments in the East China Sea. Chishitsu News, 634, 15-20.