RRS Discovery D93A
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | RRS Discovery (74E3) |
| Cruise identifier | D93A |
| Cruise period | 1978-05-26 — 1978-06-13 |
| Status | Completed |
| Port of departure | Lisbon, Portugal |
| Port of return | Ponta Delgada, Portugal |
| Purpose | Research |
| Objectives | The main objectives of this cruise were two-fold. The first objective was a study of the deep crust and upper mantle structure associated with the Azores-Biscay Rise using seismic refraction and gravity profiles, Three refraction lines were planned to be shot on the crest and flanks parallel to the ridge axis while three gravity and seismic reflection profiles were to be obtained across the ridge. This work represented an extension of an already completed, and similarly executed, study of Kings Trough, in order to establish the relationship (if any) of Kings Trough to the anomalous Azores-Biscay Rise.
The second objective was a detailed study of crustal ageing along a flowline. The band between 45 and 46N east of the Mid-Atlantic Ridge was chosen for study, particuarly crust between 0 and 40million years old where the greatest ageing changes are believed to occur. The study was planned to consist of unreversed NS and reversed EW refraction profiles shot with a airgun and explosions out to 50kms range. An ancillary experiment was designed to seek for any azimuthal anisotropy in the upper part of young oceanic crust which is liable to be caused by cracks and fissures known to be preferentially orientated parallel to the Mid-Atlantic Ridge axis. |
| Chief scientist | Robert B Whitmarsh (Institute of Oceanographic Sciences Wormley Laboratory) |
| Cruise report |  (0.77 MB) |
| Ocean/sea areas | |
| General | North East Atlantic Ocean (limit 40W) |
| Track charts |  |
| Measurements | |
| Physical oceanography | |
| Surface measurements underway (T,S) | Quantity: track kilometres = 4445 Description: T only |
| Other physical oceanographic measurements | Quantity: number of profiles = 1 Description: sound velocity stations |
| Meteorology | |
| Incident radiation | Quantity: track kilometres = 4444.8 |
| Routine standard measurements | Quantity: track kilometres = 4444.8 |
| Other meteorological measurements | Quantity: number of observations = 4445 Description: sea and swell |
| Geology and geophysics | |
| Core - soft bottom | Quantity: number of cores = 7 |
| Single-beam echosounding | Quantity: track kilometres = 4445 |
| Single channel seismic reflection | Quantity: track kilometres = 1850 |
| Seismic refraction | Quantity: number of stations = 6 |
| Gravity measurements | Quantity: track kilometres = 4444.8 |
| Magnetic measurements | Quantity: track kilometres = 4444.8 |
