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Observation of forearc seafloor deformation along the North d'Entrecasteaux Ridge-New Hebrides Island Arc collision zone from Nautile submersible

Abstract:

Observations indicated strong compressional deformation and dewatering of an accretionary mass. Outcrops of highly tectonized nannofossil clay, chalk and calcareous volcanic siltstone were examined and found to be smoothed and grooved from persistent downslope transport of sediment eroded from the upper forearc slope and islands of the arc. These sediments were directed from the nearshore and upper slope areas by a submarine canyon that is disrupted in mid-slope by the growing deformational front. From mid-slope, sediments are transported by sheet flow through many swales and gullies to the flat seafloor at the base of the slope, where the sediments are deposited as turbidites. Fluvial-like processes appear to be occurring along the deformation front as indicated by scour holes and depressions. -from Authors