Combined analyses of bathymetry, piston cores, 3.5-kHz echograms, and seismic reflection data reveal that sedimentation patterns in the eastern Sunda forearc are strongly influenced by vigorous deep- and bottom-water circulation. The affected region is located at the intersection of the Sumba Ridge and the Sawu-Timor Ridge, which together form a barrier to the outflow of Pacific Ocean Deep Water from the Sawu Sea to the eastern Indian Ocean. Bottom currents associated with the outflow have eroded a gap in the sill at a water depth of 1150 m, between the islands of Sumba and Sawu. Southwest of the gap, the widespread exposure of well-consolidated, middle Miocene to Pliocene foraminiferal chalks and oozes along the Sumba Ridge suggests that up to 1 km of overburden has been removed by the deep (1–1.5 km) currents. The eroded sediments have been subsequently deposited as muddy contourites in a thick (> 1km) sediment drift in the adjacent Sumba Basin. The drift consists of an elongated mound composed of reworked calcareous ooze and is bounded by moat-like channels. The influence of contour currents on trench-slope sedimentation can be significant and should be considered during studies of modern forearc systems and ancient subduction complexes on land.
Global contourite distribution database, version 2, more
Global contourite distribution database, version 3, more