On Leg 54 of the Deep Sea Drilling Project, four holes were drilled at Site 424, about 20 km south of the Galapagos Spreading Center (GSC). The holes were situated less than 300 meters from each other on a north-south line in water about 2700 meters deep, near 0°35'N and 86°07'W. The age of the basaltic basement here is about 0.60 to 0.62 m.y. (Hekinian et al., 1978). This particular site was chosen because a major sea-floor hydrothermal system, with associated sediments, occurs in this area (Klitgord and Mudie, 1974; Lonsdale, 1977). The sampling area is characterized by small mounds, 5 to 20 meters high, parallel to the axis of the GSC, and is associated with heat flow (Williams et al., 1974; Crane and Normark, 1977). The mounds are arrayed above faults in the basaltic basement (Lonsdale, 1977). The regional sedimentary blanket is about 30 meters thick. Bottom photographs made of the mounds by Corliss et al. (1978) show that they consist of black crusts with light brown and orange patches and that some are partially covered by organisms (e.g., bivalves). Holes 424 and 424A were located as precisely as possible on two mounds. The sediments are respectively 31 and 34 meters thick. Hole 424B is sampled about 300 meters north of Hole 424 in an area between two mounds. The sedimentary thickness is 38 meters. Finally, Hole 424C, also away from any mounds, was only partially sampled; only 7 meters of sediments in the topmost core was recovered. The sedimentary thickness is 30.5 meters.

Supplement to: Hoffert, Michel; Person, Alain; Courtois, Chantal; Karpoff, Anne Marie; Trauth, D (1980): Sedimentology, mineralogy, and geochemistry of hydrothermal deposits from Holes 424, 424A, 424B, and 424C (Galapagos Spreading Center). In: Rosendahl, BR; Hekinian, R; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 54, 339-376