Researcher 3A/72

Cruise summary report

Cruise Info. 
Ship name (ship code)Researcher (3175)
Cruise identifier3A/72
Cruise period1972-05-14 — 1972-06-11
Port of departureBarry, United Kingdom
Port of returnLowestoft, United Kingdom
ObjectivesPart of the Anglo-French effort to produce geological and geophysical maps of the channel. This was a complementary survey to the British Hydrographic Office's bathymetric survey observing gravity and magnetics using their Decca Hifix chain. Due to westerley gales only about half of the expected cover was achieved.

To carry out a gravity and magentic survey in part of the English Channel, west of Cherbourg.

Leg 1: Sailing delayed by bad weather, on departure Researcher made direct passage to the Channel Islands. Work began on 15th May using Hifix fixing, and good gravity, magentic and bathymetric data were recorded. The MS 47 was tried on the first two lines but was not satifactory at the survey speed. The I.G.S. data logger was installed in Plymouth. On 22nd May Researcher sailed for Jersey.

Leg 2: South west-westerly gales persisted and work was only possible in the Bays of St Bricuc and Mont St. Michal and in the partial lee of the Channel Islands. Most of the time between 23rd May to 2nd June was spent in harbour but alterating the proposed survey lines allowed operation in sheltered waters, 1200km of lines were run. Daily profiles of magnetics, gravity and bathymetry, and anomaly and track maps of mercartor projection wer obtained. This leg was brought to a premature end due to the computer generator catching on fire.

Leg 3: Delayed start due to bad weather but it was good for the rest of the project. Able to log on magnetic tape using the ship's logger installed in Jersey. Profiles could be plotted of the data. The ships echo sounder was used to measure depth until it failed. The ship then sailed for Lowestoft and conducted a number of short gravity lines run in the Wash.
Chief scientistMichael C Tully (Institute of Geological Sciences, Edinburgh)
Cruise reportResearcher 3A/72 cruise report researcher3a_72.pdf (0.27 MB) 
Ocean/sea areas 
GeneralEnglish Channel
SpecificWestern English Channel
Geology and geophysics 
Multi-beam echosoundingQuantity: track kilometres = 1112
Long/short range side scan sonarQuantity: track kilometres = 274
Single channel seismic reflectionQuantity: track kilometres = 2391
Gravity measurementsQuantity: track kilometres = 3862
Magnetic measurementsQuantity: track kilometres = 3540