Submarine Outcrop Evidence for Transpressional Deformation Within the Nankai Accretionary Prism, Tenryu Canyon, Japan - Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin - page 197

Submarine Outcrop Evidence for Transpressional
Deformation Within the Nankai Accretionary
Prism, Tenryu Canyon, Japan
Nicholas W. Hayman, Kurtis C. Burmeister, Kiichiro Kawamura, Ryo Anma,
and Yasuhiro Yamada
Abstract The Tenryu submarine canyon lies within the eastern edge of the Nankai
Trough, Japan, and exposes the internal structure of the Nankai accretionary
prism. SHINKAI 6500 submersible dives within Tenryu Canyon in 2008 collected
important new data on the structural geology of well-bedded, Pleistocene turbidite
sequences of fine-sand, silt, and mud. These data include estimates of the strike
and dip of bedding, and of the joints and faults that cut these strata. Most strata are
involved in broad, east-west trending first-order folds (trench parallel) that typify
the accretionary prism structure. Aside from the trench-parallel fold hinges and
faults, tight outcrop-scale folds and broader <1 km-scale folds have hinge-lines that
plunge to the north (trench perpendicular). These trench-perpendicular folds are
associated with outcrop-scale evidence for strike-slip faulting and appear to culmi-
nate in an oblique imbricate thrust zone near the trace of the Tokai thrust, an approx-
imate equivalent to the 'megasplay' out-of-sequence thrust in the NanTroSEIZE