Consolidation characteristics of outer Bengal Fan deposits (Table 1)

The state of consolidation of outer Bengal Fan deposits is closely related to their depositional history. Early Pleistocene sediments are underconsolidated, i.e., fabric strength is lower than under equilibrium with the present overburden stress, at depths greater than 60-80 mbsf. This may be due to rapid accumulation (>15-20 cm/k.y.) and overlying low-permeability (<10**-7 cm/s) deposits. The underlying Pliocene sediments are overconsolidated, i.e., fabric strength is higher than in equilibrium with the present overburden stress; at Sites 717 and 719 the sediments are slightly overconsolidated, whereas at Site 718 the overconsolidation is significant. Overconsolidation is explained by erosion that occurred during the early Pleistocene for which a stratigraphic gap was recorded in the drilled cores. The eroded section is estimated to be in the range of 10-40 m at Sites 717 and 719, respectively, and 130-150 m at Site 718. Below 250-300 mbsf the most sediments are normally consolidated. The amount of erosion seems to be related to block rotation and uplift due to intraplate deformation.