Sediments cored from the Barbados Ridge accretionary complex at ODP Sites 671, 672, and 676 are progressively underconsolidated with depth. Very low measured intergranular permeabilities contribute substantially to the probable excess pore-water pressures that account for the underconsolidated behavior. The estimated pore pressures immediately overlying the incipient decollement at the reference site are nearly equal to the overburden stress. Data show that the pore fluids within the fine-grained sediments of the complex are absorbing the tectonic shock of underthrusting as they are accreted, effectively leading to "lubricated subduction" of the underthrust Oligocene and older sediments. Lateral compression and dewatering by fracture permeability is taking place in the accreted section despite apparent underconsolidation, resulting in limited pore-volume reduction and sediment strengthening from east to west on the ridge.

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Physical properties measurements from seven Ocean Drilling Program (ODP) Leg 134 sites in the area where the twin submarine ridges of the d'Entrecasteaux Zone (DEZ) collide with the New Hebrides Island Arc document the subduction processes in the central New Hebrides Trench. The North d'Entrecasteaux Ridge (NDR) and South d'Entrecasteaux Chain (SDC) appear to clog the trench, uplifting Espiritu Santo Island at a rapid rate and helping to form the North Aoba Basin (NAB), a deep depression of the Pacific Plate that traps eroded sediment and ash from the surrounding island volcanoes. Porosity and water content measurements indicate that significantly less fluid exists in the Vanuatu accretionary complex than at other prisms (Barbados and Nankai). This is due, in part, to lithologic differences of sediments being incorporated into the complex from the DEZ, which are more coarse-grained, less porous, and more permeable than the hemipelagic clay-dominated Barbados forearc. Velocity anisotropy observed in the DEZ and NAB at Sites 827-833 suggests that tectonically induced lateral compression is taking place, resulting in pore volume reduction, sediment strengthening, and dewatering of the collision complex through fault-controlled fracture permeability. More fluids and higher porosity material bracketing indurated rocks in the NAB are evidence of rapid burial and alteration of sediment during intense bursts of volcanism associated with tectonic subsidence of the basin, and/or surrounding island belts due to arc-wide lateral compression from collision.