A large (∼ 25,000 km2) field of migrating sediment waves on the gently dipping seaward wall of the Manila Trench in the northern South China Basin parallels the trench floor for 450 km and extends up the wall to 900 m above the trench floor. Wavelengths range from 200 m to 5 km, and amplitudes range from 5 to 50 m. The internal structure of the waves generally suggests upslope migration. These waves have characteristics common to migrating waves that were deposited by thermohaline (contour) currents at other locations throughout the world. However, the regional setting and sediments of these South China Sea waves, together with the apparent absence of contour-current activity within the South China Basin indicate that the waves probably formed by turbidity currents or related down-slope flows that moved southward along the Manila Trench floor. These sediment waves thus demonstrate that downslope, gravity-induced flows can create fields of migrating waves that are of regional extent and are morphologically identical to sediment waves deposited by thermohaline-induced contour currents.

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