RRS Discovery D153
Cruise summary report
|Ship name (ship code)||RRS Discovery (74E3)|
|Cruise period||1984-10-20 — 1984-11-17|
|Port of departure||Falmouth, United Kingdom|
|Port of return||Falmouth, United Kingdom|
|Objectives||1. To deploy Pop-Up Pore Pressure Instruments (PUPPIs) to measure in-situ pore pressure and thus infer pore-water advection velocities at a number of sites, especially near faults, over shallow basement highs, and in areas of suspected non-linear temperature gradients.
2. To take core samples, mainly to provide material for physical properties measurements, both for geotechnical objectives and to complement PUPPI observations.
3. To investigate by seismic profiling an area in the southwest of GME that appeared to be relatively fault free.
4. To obtain continuous photographic coverage of the seafloor across the locations of known sediment faults, to look for any visual consequences of faulting or fault-related pore-water movement.
5. To obtain a photographic traverse from the abyssal plain on to an abyssal hill, to search for variation on occurrence of manganese nodules, number and type of benthos, and evidence of current erosion.
6. To study further the structure of one or more known faults by use of deep-towed, near-bottom seismic profilers.
7. To drop nine penetrators of various sizes and monitor their fall and deceleration within the sediments, using Doppler and other telemetering devices.
8. To test the Penetrator Acoustic Telemetry System (PATSY) which had been developed at IOS for installation in penetrators, to enable telemetry of data from instruments to be carried below the seabed by the penetrators.
9. To deploy an array of analogue and digital Pop-Up Bottom Seismographs (PUBS), to observe the impacts of the penetrators on the seabed, and thus (a) to determine by how much the penetrators deviated from a vertical path through the water and (b) to infer some physical properties of the sediments by modelling the dispersion of Scholte waves generated by the impacts.
10. To test the new digital PUBS and compare its response with the older analogue type.
11. To use the penetrator impacts as signals for a seismic refraction line to study the nature of "transport ridges" hat had been seen on seismic reflection profiles over many of the sediment faults.
12. To attempt to photograph the entry scars left by the penetrators, in order to help assess the amount of disruption and degree of hole-closure involved.
Objectives 1-5 were achieved with almost complete success. 7, 9, 11 and 12 were not achieved because industrial action prevented the penetrators from being loaded on the ship; however the remaining objectives, 8 and 10, were carried out independently and were successfully accomplished.
|Chief scientist||Roger C Searle (Institute of Oceanographic Sciences Wormley Laboratory)|
|Cruise report||(0.99 MB)|
|General||North East Atlantic Ocean (limit 40W)|
|Specific||Great Meteor East/ Madeira Abyssal Plain|
|Incident radiation||Quantity: track kilometres = 6667|
|Routine standard measurements||Quantity: track kilometres = 6667|
|Geology and geophysics|
|Core - soft bottom||Quantity: number of stations = 4|
Description: 6 physical analysis
|Bottom photography||Quantity: number of stations = 4|
|Multi-beam echosounding||Quantity: track kilometres = 6667|
|Single channel seismic reflection||Quantity: track kilometres = 6667|
|Magnetic measurements||Quantity: track kilometres = 6667|