11:00 〜 11:15
[SIT20-08] Set-up timing of the dextral oblique subduction in the Nankai Trough
★Invited Papers
キーワード：付加体、南海トラフ、斜め沈み込み、沈み込み帯
The oblique subduction and its tectonic effect in the upper plate is a key to understanding the crustal dynamics in the convergent plate boundary. The Nankai Trough is a traditional margin of the oblique subduction. Many models suggest that a dextral oblique subduction initiated at ~3 to 2 Ma based mainly on the start of dextral movement of the Median Tectonic Line (MTL) and crustal up-down deformation in southwest Japan.
A recent structural and tectonic analysis of the forearc basin and accretionary prism off the Kii Peninsula, suggests that the subduction, accretion and forearc sedimentation started at ~6 Ma and the rapid growth of outer wedge has been taken place since ~2.2 Ma due to accelerated terrigenous sediment supply from the uplifted mountains on land. The dextral strike-slip faulting along the out-of-sequence thrust occurred in transition zone between the inner and outer wedges.
Kimura et al. (2022) examined the structure of the northern edge of the Kumano forearc basin in the inner wedge off the Kii Peninsula and concluded that the subduction, accretion, backward and forward thrusting started at ~6 Ma. The vergence of thrust and folds is consistent with northwestward dextral oblique relative plate motion between the Amurian and the Philippine Sea Plate.
The slab of the Philippine Sea Plate extends for ~350 km beneath southwest Japan according to the seismic tomographic data (Wu et al, 2016), which is consistent with ~ 6 Ma continuously oblique subduction with a rate of ~ 6 km/yr. The delayed onset of the dextral crustal movement in the upper plate at ~3-2 Ma could be triggered by the arrival of the new slab at the depth beneath MTL.
References
Kimura et al., (2022) Geochemistry, Geophysics, Geosystems, 12(11). In review.
Wu, J., Suppe, J., Lu, R., & Kanda, R. (2016). Journal of Geophysical Research: Solid Earth, 121(6), 4670-4741.
A recent structural and tectonic analysis of the forearc basin and accretionary prism off the Kii Peninsula, suggests that the subduction, accretion and forearc sedimentation started at ~6 Ma and the rapid growth of outer wedge has been taken place since ~2.2 Ma due to accelerated terrigenous sediment supply from the uplifted mountains on land. The dextral strike-slip faulting along the out-of-sequence thrust occurred in transition zone between the inner and outer wedges.
Kimura et al. (2022) examined the structure of the northern edge of the Kumano forearc basin in the inner wedge off the Kii Peninsula and concluded that the subduction, accretion, backward and forward thrusting started at ~6 Ma. The vergence of thrust and folds is consistent with northwestward dextral oblique relative plate motion between the Amurian and the Philippine Sea Plate.
The slab of the Philippine Sea Plate extends for ~350 km beneath southwest Japan according to the seismic tomographic data (Wu et al, 2016), which is consistent with ~ 6 Ma continuously oblique subduction with a rate of ~ 6 km/yr. The delayed onset of the dextral crustal movement in the upper plate at ~3-2 Ma could be triggered by the arrival of the new slab at the depth beneath MTL.
References
Kimura et al., (2022) Geochemistry, Geophysics, Geosystems, 12(11). In review.
Wu, J., Suppe, J., Lu, R., & Kanda, R. (2016). Journal of Geophysical Research: Solid Earth, 121(6), 4670-4741.