of significant permeability increase within the decollement with increasing pore pressure

(Screaton et al., 1997).

Fluid Flow and Pore Pressures

 Evidence for fluid flow at the Barbados accretionary complex comes from the

presence of low-chloride anomalies observed along the decollement (Kastner et al.,

1993). It has been suggested by Bekins et al. (1995) that smectite dehydration is the most

likely mechanism for low-chloride anomalies. In contrast, Fitts and Brown (1999)

suggested that low-chloride anomalies occur as a result of artificial squeezing of

sediments released from smectite interlayers during pore water sampling. However, even

after accounting for the effects of sample squeezing process, the low-chloride anomaly is

still 12% fresher than seawater (Fitts and Brown, 1999) supporting the clay dehydration

as a possible explanation for low-chloride anomalies. The clay dehydration reaction

takes place at temperatures between 60-160 C (Perry and Hower, 1970). Based on

kinetic modeling of clay dehydration in the Barbados accretionary complex, Bekins et al.

(1995) estimated the peak reaction window to be at 50 km arcward of the deformation

front. Thus, if the fluid released from smectite dehydration is responsible for the

observed low-chloride anomalies at the toe of the prism (Site 948), then pore fluids must

migrate over 46 km to reach Site 948 (Bekins et al., 1994).

 Heat flow anomalies have also been observed at the Barbados accretionary

complex from temperature measurements (Fisher and Hounslow, 1990) and surface heat

flow surveys (Foucher et al., 1990). Seafloor heat flow values near the toe of the

complex range from 96 to 192 mW m-2 (Fisher and Hounslow, 1990) and are well above

the 53-55 mW m-2 expected for 90 Ma oceanic lithosphere (Ferguson et al., 1993). One

of the possible explanations for the observed heat flow anomalies is fluid flow along the