Thermal conductivity of ODP Leg 110 holes

Thirty-four sediment and mudline temperatures were collected from six drill holes on ODP Leg 110 near the toe of the Barbados accretionary complex. When combined with thermal conductivity measurements these data delineate the complicated thermal structure on the edge of this convergent margin. Surface heat-flow values from Leg 110 (calculated from geothermal gradients forced through the bottom-water temperature at mudline) of 92 to 192 mW/m**2 are 80% to 300% higher than values predicted by standard heat flow vs. age models for oceanic crust, but are compatible with earlier surface measurements made at the same latitude. Measured 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 fluid through the complex along sub-horizontal, high-permeability conduits, including thrust faults, the major decollement zone, and sandy intervals. Simple calculations suggest that this flow is transient, occurring on time scales of tens to tens of thousands of years. High heat flow in the vicinity of 15°30'N and not elsewhere along the deformation front suggests that the Leg 110 drill sites may be situated over a fluid discharge zone, with dewatering more active here than elsewhere along the accretionary complex.