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Representative photographs of cores collected from the Mississippi Fan and Orca and Pigmy basins during DSDP Leg 96. Fining-upward channel sequences recovered in midfan channel Sites 621 and 622 contain (A) a basal gravel channel lag (621-33,CC), overlain by (B) sands (621-33-2, 105-123 cm), overlain by (C) a passive clay and mud channel fill (621-10-2, 115-133 cm). The sequence drilled at Site 615 on the lower fan includes (D) a carbonate debris flow (615-50-4, 115-133 cm), overlain by (E) thin, cross-stratified silts (615-12-2, 85-103 cm) and interbedded (F) silt and clay laminae (615-11-3, 105-123 cm). Sediments recovered at fan margin Site 616 document an upper mass movement deposit, 100 m thick and typified by (G) high-angle slump material (616-6-6, 20-38 cm). Sediments recovered from intraslope basin Sites 618 and 619 consist of (H) pelagic and hemipelagic clay laminae (619-11-3, 100-118 cm).

Experiments were made in the laboratory to measure the velocity of propagation of compressional and transverse elastic waves in ocean sediments while under varying conditions of compacting pressure. Various attempts to formulate expressions relating velocity with composition are discussed and are found to be not applicable to compacted sediments. The concept of a structure bulk modulus is introduced to account for the observed velocity changes. Shear waves were observed at compacting pressures exceeding 500 kg/sq cm. The effects of hydrostatic pressure and the development of anisotropy are also studied.

A survey of the Mid‐Atlantic Ridge crest in the region of the Kurchatov Fracture Zone (40.5°N) employing a long‐range side‐scan sonar is described. Away from the fracture zone, long straight faults spaced about 2 km apart and parallel to the ridge axis were seen. Almost all of these faults seem to be generated on the median valley floor within a few kilometers of the axis. The inferred heights of the fault scarps are consistent with the fact that most of the uplift in the median valley walls is accommodated on inward facing normal faults of a few hundred meters' throw. The mean height of inward facing fault scarps decreases only slightly outside the median valley, an indication that reverse movements on these faults are not significant processes. The active section of the fracture zone is characterized by a deep trough of 055° trend, which it is believed represents an oblique spreading center. There is no indication of the presence of a transform fault. Oblique faults seen within the fracture zone were probably produced by repeated shearing and healing of the sea floor within the active section and may themselves control the trend of the oblique spreading center. Subsequent vertical movements along some of these oblique faults have produced spectacular serrated walls for the fracture zone valley. The persistence of the fracture zone topography requires that the two sides of the fracture become welded together after leaving the active section.

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