RRS Shackleton S4/75

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS Shackleton (74SF)
Cruise identifierS4/75
Cruise period1975-04-18 — 1975-05-07
Port of departureDubai, United Arab Emirates
Port of returnBombay, India
Objectives1. Geophysical study of the Owen Basin
The main objective was to establish the nature and origin of the crust beneath the Owen Basin and to gain some insight into the age of the crust, since it is possible that its history goes back to the break-up of Gondwanaland. It was also planned to relate the deeper reflectors seen beneath the basin to those uplifted on the Owen Ridge which have already been sampled in holes drilled by D.V. Glomar Challenger. The chain of seamounts along the Owen Basin/Sheba Ridge boundary were also to be studied.
2. Organic geochemistry of recent sediments
Three cores were planned at different depths on the continental margin off Masirah Bay to expand the current studies of upwelling regions being undertaken at IOS Wormley.
3. Other geological samling
Dredging of the escarpment at the south end of the Owen Ridge and coring across a leveed channel on the Indus Cone were subsidiary objectives of Cruise 4/75.
4. On-line digital processing of seismic profiles
It was planned to develop at sea simple algorithms for an on-line signal processing system designed to enhance the penetration of seismic reflection profiles.
Chief scientistRobert B Whitmarsh (Institute of Oceanographic Sciences Wormley Laboratory)
Cruise reportRRS Shackleton S4/75 cruise report shackleton3_4_75_data_report.pdf (4.90 MB)  RRS Shackleton S4/75 cruise report shackleton3and4_75.pdf (0.85 MB) 
Ocean/sea areas 
GeneralGulf of Iran (Persian Gulf)
Arabian Sea
Gulf of Oman
Track chartsRRS Shackleton S4/75 cruise track — trk1420a.html RRS Shackleton S4/75 cruise track — trk1420b.html
Geology and geophysics 
Core - soft bottomQuantity: number of cores = 4
Long/short range side scan sonarQuantity: track kilometres = 4630
Seismic refractionQuantity: 80
Gravity measurementsQuantity: track kilometres = 5000
Magnetic measurementsQuantity: track kilometres = 5000