1980 - National Institute of Oceanography

covered during the cruise. In addition, 29 water samples, 46 grab samples, 4 dredge
samples, 4 core samples and 12 bottom photographs were taken.
The surveys indicated that the continental shelf from the shore to a depth of
60-75 m is marked by even topography because of the clay cover.
Cruise 73 (Chief Scientist—H.N. Siddiquie)
This cruise of 19-days duration was from 13 April to 1 May. It was sponsored
by the ONGC for the development of offshore oilfields. The work included: survey
of the pipeline routes from South Bassein to Direction Bank, from Direction Bank up
to the shore and shallow seismic surveys at South Bassein and Direction Bank.
During this cruise, more than 290 line km of echosounding, 660 line km of
ORE mud penetrator profiling, 1060 line km of sparker and 120 line km of magnetic
surveys were carried out.
Along the proposed pipeline route (from Bassein to Direction Bank), the depth
varied from 51 m at Bassein to 65 m on the southern side and 41 m at the Bank.
From Direction Bank along the route the depth ranged from 45 m at the Bank to
55 m towards east and 15 m near the shore.
Cruise 74 (Chief Scientist—H.N. Siddiquie)
This 12-days cruise from 4 to 15 May was carried out in continuation of the
earlier cruise. During the cruise shallow seismic profiling on the Bassein structure and
the post-lay survey of the pipelines from Bassein to Bombay High were carried out.
In all, 20 lines were surveyed in the south Bassein and the pipeline profiling
was done along 50 lines. Over 673 line km of echosounding. 200 line km of side
scan sonar and 671 line km of shallow seismic profiling were carried out.
The depth on south Bassein ranged from 38 to 69 m and increased, in the
northern and eastern sides and also in the southern and western sides- The pipeline
was crossed, in 64 tracks and the pipes were seen in 43 tracks. Along 52 tracks, the
pipelines were very well covered by 2.2.5 m thick sediments and in the remaining 2
tracks, the pipelines apparently were on the seabed or were covered by a thin sediment
only.
Cruise 75 (Chief Scientist—M.G.A.P. Setty)
This 14-days cruise from 21 May to 3 June was devoted to the study of oceanographic
conditions in the MONEX square ( between 11-15°N and 68-71° 31' E) during
the onset of southwest monsoon. Another aspect of the cruise was to study primaryproductivity,
nannoplankton and extra cellular liberation of photosynthates at
various depths of the euphotic zone.
The cruise covered a distance of 3892 line km. in which 50 stations were
worked. Data on phosphate, nitrate, nitrite, ammonia and silicate were collected at
all the stations.
At the request of BARC, sediment samples from deeper parts of the sea were
collected for their use- Radon activity was also studied during the cruise.
14