2021 Volume 127 Issue 3 Pages 133-143
The 3D seismic geomorphological analysis for the late Quaternary sediments in the Joetsu buried submarine canyons and the western flank of the Umitaka Spur in the southeastern Toyama Trough, central Japan, reveals the characteristic depositional patterns caused by outbreaks of mass movements or turbidity currents on the surrounding flanks of the Umitaka Spur. In the Joetsu buried submarine canyons, 3D seismic survey data show evidence of lateral inflow sedimentation event, possibly caused by slope failure on the northern flank of the Umitaka Spur. At the foot of the western flank, the amplitude map on a sequence boundary horizon demonstrates a parallel elongated depositional pattern, which may reflect slope gully structures formed by abrupt turbidity currents flowing down the western flank of the spur. The 3D top surface display of chaotic mound structures seen on a seismic section demonstrates several kilometer wide debris flow lobes with an undulation pattern or a smooth pattern on the surface, reflecting the composed materials. Because previous studies pointed out that pockmarks, slope failures and related slope gully structures frequently develop on the present seafloor on and around the Umitaka Spur and Joetsu Knoll, it is suggested that these characteristic sedimentation events revealed in this study were caused by gas hydrate dissociation related to relative sea level changes during the Late Quaternary.
