Evaluation of hydrogeologic properties of the Barbados accretionary prism: a synthesis of Leg 156 results

In situ and laboratory studies of permeability, conducted by Ocean Drilling Program scientists from Leg 156, provide constraints on parameters controlling the hydrogeologic system in the Barbados accretionary prism. Results from these studies indicate that core-scale and formation-scale permeability values differ by at least several orders of magnitude and are dependent on pore-fluid pressure and effective stress conditions. Direct measurement from packer experiments and indirect evidence from consolidation tests suggest that pore-fluid pressures are commonly above hydrostatic values and approach lithostatic values within the decollement zone. Permeability and fluid pressure conditions in the Barbados accretionary prism reflect the complexity of the hydrogeologic system of such an active tectonic environment.