PI Country:
Japan
PIs:
Fujiwara, T.
Institution:
JAMSTEC
Funding:
MEXT
Ocean:
N. Pacific
Region:
Mariana Trough
Year:
2008
Start Date:
25-Jun-2008
End Date:
6-Jul-2008 see article by Fujiwara et al. 2008 InterRidge Newsletter; Cruise YK08-08 Leg-1 of the Japanese R/V Yokosuka and the submersible Shinkai 6500 took place in the Mariana Trough from 25 June - 6 July 2008 to study the formation of oceanic lithosphere in the active back-arc spreading center. Three submersible dives were devoted to the median valley of the segment center at 17°N. Visual observations provide ground references for sidescan sonar imagery collected in 2003 to discuss volcanotectonic features. Observations confirm that the seafloor is paved with sheet lava flows of high effusion rates. Inferred from sediment cover, sheet lava flows in the axial portion of the median valley are considered to be youngest, with the eastern margin regarded as older than the western margin. The N-S trending tectonic structures (i.e. faults, fissures) oblique to the median valley could be younger than the valley parallel NNW-SSE trending structures.
Ship:
R/V Yokosuka
Equipment:
submersible Shinkai 6500 
