The Blake Ridge Diapir is the southernmost in a series of about 20 diapiric structures rising from depth within sediments of the Carolina Trough near 32º30.5'N, 76º11.5'W, in a water depth of 2170 m (Fig. 1).
The Blake Ridge and adjacent Carolina Ridge are areas with BSRs. Seismic reflection profiles show that the BSR shoals from 0.5 to 0.3 s (two-way traveltime sub-bottom) over the crest of the Blake Ridge Diapir and that a small fault extends upward from the doming BSR to the seafloor over the diapir (Paull et al., 1995). Ocean Drilling Program (ODP) Site 996 consisted of five holes that were located along a 80-m-long east-west transect across a mussel bed, which is presumably part of a chemosynthetic community fed by gas-charged fluids migrating along the fault system (Paull et al., 1995). Holes 996A, 996B, and 996C were located in this mussel bed. Holes 996D and 996E were 40 m to the east and west, respectively (Fig. 2).
The sedimentary sequence consists primarily of nannofossil-bearing clay and nannofossil-rich clay. Hard carbonate beds were encountered in two zones between 5 and 20 mbsf, and between 30 and 50 mbsf (Paull, Matsumoto, Wallace, et al., 1996). The maximum age of the recovered sediments is about 1.0 m.y. Gas hydrates were recovered from all five holes. The hydrates were white and occurred as massive pieces, platy fracture fillings, and vertically oriented rod-shaped nodules (Paull, Matsumoto, Wallace, et al., 1996).