10:45 AM - 11:00 AM
[SCG45-07] Marine and earth science surveys in the Okinawa Trough for the IODP Scientific Drilling: Hakuhomaru KH-21-3 cruise preliminary reports
Keywords:Okinawa Trough, Scientific Drilling, Normal fault, Backarc basin, Monsoon, Paleoenvironment
We conducted a research cruise (KH-21-3 cruise) on the Okinawa Trough by R/V Hakuhomaru. In this presentation, we report the outline and preliminary results on the cruise. Two legs (Leg 1 and Leg 2) were carried out on this cruise for the IODP Scientific Drilling.
[KH-21-3 cruise Leg 1] The Okinawa Trough is a back-arc basin located on the Eurasian plate, and has been undergoing rifting since 2 Ma. Especially, the rifting in the southern part of the Okinawa Trough started about 0.1 Ma, but there are still no reports of basaltic oceanic crust. In the KH-21-3 cruise Leg 1, we find the detailed normal faults that construct the graben, the lithology and age of sediments that filled the graben, the heat flow and rocks in the knoll to understand the geohistory from Quaternary to present on the Okinawa Trough. In KH-21-3 cruise Leg 1, we conducted the seismic survey, SBP, swath bathymetry, gravity, magnetic and XCTD observations, piston coring, rock sampling by dredge, heat flow measurements and plankton sampling in the southern part of the Okinawa Trough.
[KH-21-3 cruise Leg 2] The northern part of the East China Sea has large salt fluctuations in summer, and the IODP site U1429 (Danjo Basin) is an important site for elucidating the history of changes in the Asian monsoon. However, the coring at U1429 in 2013 was blocked by a sand layer (thickness unknown) at a depth of 200 m below seafloor. Therefore, in the KH-21-3 cruise Leg 2, in order to extract the effective drilling sites, we investigate the geological structures in the southeastern part of the U1429 site. In KH-21-3 cruise Leg 2, we conducted the seismic survey, sediment sampling by piston coring, seafloor surface sediment sampling using multiple coring, SBP, swath bathymetry, gravity, magnetic and XCTD observations and plankton sampling in the Danjo Basin.
[KH-21-3 cruise Leg 1] The Okinawa Trough is a back-arc basin located on the Eurasian plate, and has been undergoing rifting since 2 Ma. Especially, the rifting in the southern part of the Okinawa Trough started about 0.1 Ma, but there are still no reports of basaltic oceanic crust. In the KH-21-3 cruise Leg 1, we find the detailed normal faults that construct the graben, the lithology and age of sediments that filled the graben, the heat flow and rocks in the knoll to understand the geohistory from Quaternary to present on the Okinawa Trough. In KH-21-3 cruise Leg 1, we conducted the seismic survey, SBP, swath bathymetry, gravity, magnetic and XCTD observations, piston coring, rock sampling by dredge, heat flow measurements and plankton sampling in the southern part of the Okinawa Trough.
[KH-21-3 cruise Leg 2] The northern part of the East China Sea has large salt fluctuations in summer, and the IODP site U1429 (Danjo Basin) is an important site for elucidating the history of changes in the Asian monsoon. However, the coring at U1429 in 2013 was blocked by a sand layer (thickness unknown) at a depth of 200 m below seafloor. Therefore, in the KH-21-3 cruise Leg 2, in order to extract the effective drilling sites, we investigate the geological structures in the southeastern part of the U1429 site. In KH-21-3 cruise Leg 2, we conducted the seismic survey, sediment sampling by piston coring, seafloor surface sediment sampling using multiple coring, SBP, swath bathymetry, gravity, magnetic and XCTD observations and plankton sampling in the Danjo Basin.