Transient fluid flow through the toe of the Barbados Accretionary Complex: Constraints from ocean Drilling Program Leg 110 heat row studies and simple models

Thirty‐four sediment and mud line temperatures were collected from six drill holes on Ocean Drilling Program (ODP) leg 110 near the toe of the Barbados accretionary complex. When combined with thermal conductivity measurements from sediment cores and results from earlier surveys, these data delineate the complicated thermal structure on the edge of this convergent margin. Heat flow values at the seafloor of 92–192 mW m −2 are 80–300% higher than those predicted by standard heat flow versus age models for oceanic crust but are compatible with earlier seafloor measurements made in this area at the same latitude. Heat flow tends to decrease downhole at four sites, suggesting the presence of heat sources within the sediments. These results are consistent with the flow of warm fluids through the complex along high permeability conduits, including thrust faults, the major décollement zone, and sandy intervals. Simple calculations suggest that this fluid flow is transient, occurring on time scales of tens to tens of thousands of years. Fluid flow velocities along the décollement zone, estimated with a simple thermal model, are about 10 −7 m s −1 , 100 times faster than predicted by numerical, steady state analyses. The estimated maximum sediment permeability within the décollement zone, which was based on the above fluid flow velocity, is about 10 −12 m 2 , also 100 times higher than that calculated numerically. High heat flow in the vicinity of 15°20′N and not elsewhere along the deformation front suggests that the leg 110 drill sites may be situated over a prism‐water discharge zone, with dewatering more active here than elsewhere along the accretionary complex.