GLORIA. Geophysical studies of the continental margin on the eastern edge of the Grand Banks.
The main objectives were to study the structural and sedimentary processes which have shaped the continental margin to the east of the Grand Banks between 41° and 52° N, and to compare the geological history of this margin with that of its conjugate on the eastern side of the Atlantic.
3 double runs made over a measure mile inn the Humber Estuary to calibrate the EM log, runs at 6, 9 and 12 knots. Trans-Atlantic passage made, taking 6 days. During passage equipment towing trials made. All gear was rigged, tested and tuned. A working traverse of the Mid-Atlantic Ridge was abandoned due to bad weather.
26th September start of first survey line, PES and 3.5 kHz fish deployed and GLORIA and the SRP launched. The fish found it difficult to detect sea bed and interfered with the other equipment so was not run again. Took a few days to find the lowest sustainable engine speed at high pitch. Crossing of the Atlantic was faster than expected. Undertook the outer two N-S legs planned for 2/81 but not completed due to electrical problems. Survey continued with SRP, magnetometer, gravity and PES, and GLORIA cable changed.
4 sonobuoy stations, 1 and 2 (1000m3 airgun), 4 and 5 (300m3 airgun).
GLORIA - 2-second pulse every 40 seconds used. Trouble was experienced with interference from the SRP but SRP not normally run. 42 tapes of 8 hours each recorded with a track distance of >2000 miles. 4600 nautical miles of seismic reflection data logged by the 3.5 kHz high resolution SRP over both legs. Compressors gave little trouble and all faults recorded were electrical. Each airgun was run for 5 days. Barringer magnetometer performed well. The gravimeter produced a noisy but acceptable record, average errors of 2.27m gal. 4 sonobuoy stations successfully occupied during the cruise. 1 further buoy failed to transmit useful data.
M L Somers (Institute of Oceanographic Sciences Wormley Laboratory)
North Atlantic Ocean
Geology and geophysics
Quantity: track kilometres = 5600 Description: in total during 1/81 and 2/81
Long/short range side scan sonar
Quantity: track kilometres = 3220 Description: GLORIA, 42 tapes of 8hours each, >2000 miles
Multichannel seismic reflection
Quantity: track kilometres = 7400 Description: 4600 miles in total during 1/81 and 2/81, 6 channel array SRP used
Quantity: track kilometres = 15556.8 Description: in total during 1/81 and 2/81, average errors of 2.27 m gal
Quantity: track kilometres = 10371.2 Description: in total during 1/81 and 2/81, Barringer magnetometer
Other geological/geophysical measurements
Quantity: number of deployments = 4 Description: sonobuoys, 2 with 1000m3 and 2 with 300m3 airgun