1. Magnetic survey, western Gulf of Aden
Four days at the beginning of the cruise were reserved for completing a magnetic survey begun by the University of Newcastle during Shackleton Cruise 2/75. The object of the survey was to obtain profiles along the spreading direction in order to look for the two-stage spreading history already postulated for the Red Sea (Girdler and Styles, 1974).
2. Seismic refraction experiment, East Sheba Ridge
Following work done on the Mid-Atlantic Ridge (Whitmarsh, 1975) this experiment was designed to see whether a shallow zone of low-velocity material also underlay the median valley of the Sheba Ridge, using IOS pop-up bottom seismic recorders (PUBS).
3. Subduction zone off the Makran coast, Gulf of Oman
First motion studies of earthquakes near the Makran coast (McKenzie, in preparation), and other evidence, suggest that an incipient subduction zone should exist offshore. Participants from the University of Cambridge wished to obtain seismic reflection and gravity profiles over the continental margin in the search for a zone of compression. Two long seismic refraction lines were also planned.
4. Reflection profiles across the Murray Ridge
Since the work of Barker (1966) little more has been done to investigate Murray Ridge. Two reflection and gravity profiles were planned across the ridge to shed further light on its origin.
5. Passage track over Owen Basin
A long passage track, from the East Sheba Ridge to the Murray Ridge, down the axis of the Owen Basin, was planned as a preliminary investigation for the following cruise.
Robert B Whitmarsh (Institute of Oceanographic Sciences Wormley Laboratory)