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 900m thick basin sedimentary column near 16°N and a southern one with a 4.5km thick one to the south. 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. 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 to the toe in the Barbados area. We suggest two possible other sources. One, for the southern sections, 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. -from Authors