11:30 AM - 11:45 AM
[SIT07-08] Accretion vs. tectonic erosion in Cenozoic margin of southwest Japan
Such an age gap in the ancient accretionary complex would be one of the signals for tectonic erosion in the past. Recently, a hypothesis that a tremendous amount of tectonic erosion has taken place during Early Cretaceous and middle to late Miocene time has proposed based on age gaps in the accretionary complex. Such age gaps in the accretionary complex, however, do not automatically imply that tectonic erosion has taken place, as other interpretations such as no accretion, cessation of subduction, and/or later tectonic modification, are also possible. In the case of the middle to late Miocene period, for example, a drastic tectonic change after the opening of the Japan Sea and clockwise rotation of southwest Japan may be linked to ridge subduction or a switch in subduction from the Pacific to Philippine Sea Plate. Recent drilling in the forearc of the Nankai Trough suggests that the accretion was renewed at ~6 Ma after igneous activity intruding the early Miocene accretionary prism. Kimura et al. (2014) interpreted that the subduction ceased between ~12 Ma to ~8 Ma due to the transference of subduction from the Pacific Plate to the Philippine Sea Plate, as opposed to the "continuous subduction with subduction erosion" viewpoint. These different scenarios need to be tested in the future.
von Huene, R. & Lallemand, S. 1990. Tectonic erosion along the Japan and Peru convergent margins. Geological Society of America Bulletin, 102, 704-720.
Kimura, G., Hashimoto,Y., Kitamura,Y., Yamaguchi,A. & Koge, S. 2014. Middle Miocene swift migration of the TTT triple junction and rapid crustal growth in southwest Japan ? A review, Tectonics 33, 1219?1238, doi:10.1002/2014TC003531.