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Understanding overpressure, fluid flow, and sediment compression behavior is critical for evaluating the stability of continental slopes. Integrated Ocean Drilling Program (IODP) Expedition 308 was aimed at testing a multidimensional flow model by examining how physical properties, pressure, temperature, and pore fluid composition vary within low-permeability mudstones that overlie a permeable and overpressured aquifer (see the “Expedition 308 summary” chapter). We drilled, logged, cored, and made in situ measurements in a region of very rapid Pleistocene sedimentation: the Ursa Basin (Fig. F1).

We took whole-core geotechnical samples for shore-based consolidation tests (Table T1). Consolidation tests simulate how porosity evolves with effective stress under one-dimensional gravitational compaction caused by sedimentation. The transition from recompression to virgin compression behavior provides an estimate of the maximum in situ effective stress the sample has undergone (Becker et al., 1987; Casagrande, 1936). The experiments also provide insight into how permeability evolves with burial and compression.

Consolidation properties were determined from results of constant rate of strain consolidation (CRSC) tests on intact samples.