Fig. 2: Main sedimentological characteristics of the studied cores.

A Stacked, sharp-based and base-graded event beds comprising recurring facies successions: Base of the successions is formed by ripple cross-laminated silt (F3), which is followed by laminated clay and silt (F2). These deposits are, in turn, overlain by structureless mud (F2C) and/or bioturbated mud (F1B). Red arrow – low-angle ripple cross-lamination. See text for explanation. Core section M0081D-1H-6WR2, 0–30 cm, Southern Japan Trench expanded section. B Close up of the base of a gravity-flow bed, showing ripple cross-laminated silt (F3) that grades upward into laminated clay and silt (F2). The lamination starts with subtle, lateral thickness variation with laminae terminations, followed by parallel lamination and transition to structureless mud (F2C). C Slump-folding and loading structures in clay-silt heteroliths. The uppermost ripple cross-lamination grades laterally into laminated mud (blue arrow). Soft-sediment deformation is restricted to a specific bed interval pointing to syn-sedimentary origin and high initial water content of the sediment. Core section M0082C-1P-1WR6, 63–72 cm, Southern Japan Trench condensed section. D Laminated to cross laminated mud with foresets (red arrow) and down-lapping laminae terminations (yellow arrow). Core section M0082C-1P-1WR6, 74–80 cm, Southern Japan Trench condensed section. E High-contrast 3D-view to pseudo-nodular silt/sand, sunken into structureless mud. Core section M0083F-1H-10WR16, 0–21 cm, Central Japan Trench expanded section. Note that the core margins have bent downwards due to coring process.