water flow in the Barbados Accretionary Complex

We present a simple analytic kinematic model of the Barbados accretionary complex assuming a porosity depth law and deformation by pure vertical shear. The model is applied to two sections, a northern one with a 900‐m‐thick basin sedimentary column near 16°N and a southern one with a 4.5‐km‐thick one to the south. This simple model is compatible with growth of the Barbados accretionary complex since 50 Ma assuming a constant subduction rate and a constant basin sedimentary column equal to the present one. This conclusion is not affected by reasonable changes in the porosity depth law. It suggests that the totality of the entering sedimentary column is either accreted or subcreted to the wedge. The accretion velocity decreases dramatically with age and its variation should be taken into account in any quantitative model. The average strain rates show remarkably different distributions between the two sections, the thinner wedge having a much higher rate in a narrow area at the toe. We then use the model to compute the sediment grains flow, the fluid flow, and their thermal effects. These effects are small and do not exceed 5% of the heat flow in the absence of other internal flows. In contrast the thermal effect of the burial of the slab can result in a lowering of the surface heat flow by as much as 40%. The temperature at the base of the wedge on its arc side is close to 300°C on the southern section and half that amount on the northern one. This high temperature could account for the absence of large earthquakes to the south and their presence to the north. The amount of water discharged, if collected by faults over the whole toe area, is unable to account for some of the manifestations observed over the toe or seaward of the toe in the Barbados area. We suggest two possible other sources. One, for the southern section, is the Orinoco fan area. The other, for the northern section, might be seismic pumping at the limit of the seismogenic zone, along the backthrusts between the accretionary wedge and the forearc basin.