1980 - National Institute of Oceanography

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3.3 Geological Oceanography 3.3.1 Geological and geophysical surveys to assess the petroleum and mineral prospects of the continental margins of India 3.3.2 Regional geology and manganese nodule deposits in the Arabian Sea and Central basin of the Indian Ocean 3.3.3 Geochemistry of the sediments of the continental margins of India 3.3.4 Sediments of the western continental margin of India 3.3.5 Foraminifera as indicators of pollution in the marine environment Detailed studies are being made on the continental margins, marginal base, morphology of the sea floor (Arabian Sea, Bay of Bengal and Central basin of the Indian Ocean) and its underlying structures as well as on the physical and chemical properties of the sediments, to determine mineral and petroleum prospects. Foraminifera in relation to pollution formed the part of the studies. Work was carried out on five projects as follows: 3 3.1 Geological and geophysical surveys to assess the petroleum and mineral prospects of the continental margins of India Geological and geophysical studies were carried out on the continental margins off Mormugao, Mangalore, Cochin and Bombay and these covered 3036 line km of echosounding, 972 line km of side scan sonar, 1873 line km of shallow seismic profiling and 2462 line km of magnetic surveys. Underwater camera was also operated at 16 stations. The work dene on the various topics is described below: (1) Geomorphology (a) Mormugao to Cochin: The continental shelf upto a depth of about 40m but in some areas upto 25 m only (Off Cochin) is marked by an even topography due to clay cover. Beyond this depth, the topography is uneven and on the shelf off Cochin, at a depth of about 50 m, a series of pinnacles and ridges are prominent and another set of ridges is seen before the shelf-break. A rock outcrop off Netrani Island identified on the echogram and also from seismic and magnetic records followed by dredging was found to be amphibolite, indicating that the ancient rocks of Dharwar extend upto the middle of the shelf with a thin sediment cover. A pro- 37
minent 30-35 km wide flat terrace at a depth range 350-400m off Quilon and a ridge of about 700 m off Cochin were recorded. (b) Off Bombay: The shelf-break in the area occurs at a depth of about 97 m and 210-270 km from the shore. The shelf upto a depth range of 60 to 75 m and from 115 to 130 km away from the coast is marked by an even topography. Beyond these depths, the topography is uneven and is marked by numerous pinnacles. Isolated basins of even topography are also seen at some places· (c) Lakshadweep: Geomorphological maps of Chetlat, Kiltan, Bitra, Kadmat and Amini atolls were prepared. The maps indicate that the reef is wider on the windward, i.e., W, NW and SW side than on the leeward eastern side. The reef on the windward side is marked by a number of prominent terraces which probably indicate the changes in the sea level or the stages in the growth of the reef. The sand ridges and gravel trains indicate that in most of the lagoons and on the windward side, the direction of the sediments is SW to NE. In some lagoons, due to wave refraction, the direction of sediment movement is from NW to SE also. The radio carbon dates of the storm beaches range from modern to 2975 ± 1000. BP and indicate clustering between 3000 to 2000 BP and from present to 500 BP. The younger storm beaches towards the shore suggest that parts of the islands have grown by about 30 m in the last 2780 years (Chetlat), 120 m in 1620 years (Kiltan) and about 100m in 470 years (Minicoy). The absence of the storm beaches on some of the islands, younger beaches towards the shore and clustering of ages and the lack of lateral and chronological continuity can be explained by periodic stormy conditions rather than by the changes in the sea level. The number of storms in the Arabian Sea has varied from a minimum of 1 in 1949 to 10 in 1893, 1926 and 1930. It is very likely that such changes would have occurred in the past also. 2. Surficial Geology (a) Off Mormugao-Mangalore: More than 10 m thick clay was observed near the coast which thins out beyond 40 m depth and the underlying sands are exposed on the outershelf. Seismic records show that about 3 m acoustically transparent clay overlays a reflector. Another undulating reflector at about 10 m is also seen. (b) Off Cochin-Quilon: The shelf between the depths of about 25 to 40 m is covered with clays and beyond this depth, sand is exposed. On the outer shelf, prominent reflectors are seen at 35-40m and 50-60 m depth ranges which apparently dip seawards. At the shelf edge, a number of transparent layers are present. Their formations have a low dip at the shelf edge which steepens along the slope and some of the formations are underlain by transparent horizons. The slope appears to be disturbed and faulted with many anticlinical features some of which lie at a depth of about 300 m. On the upper slope, a prominent synclinal depression with about 150 m thick sediments is seen. This is followed seaward by an uplift and an anticline. The outer slope is marked by a well-defined faulted trough followed by a ridge rising to about 400 m. Beyond this depth another depression occurs. 38
Page 1 and 2: NATIONAL INSTITUTE OF OCEANOGRAPHY
Page 3 and 4: ANNUAL REPORT 1980 16 NATIONAL INST
Page 6 and 7: 1 Director's Report The year marks
Page 8 and 9: as development of offshore oilfield
Page 10 and 11: 2 Major Scientific Highlights • R
Page 12: Research Activities
Page 16 and 17: Summaries of the cruises 66 to 84 a
Page 18 and 19: Using IOSN, zooplankton samples wer
Page 20 and 21: Cruise 76 (Chief Scientist—M.G.A.
Page 22: participated in the cruise. They co
Page 25 and 26: the meteorological parameters have
Page 27 and 28: Distribution of temperature (A), sa
Page 29 and 30: 3.1.3. Studies on land-sea interact
Page 31 and 32: INSTRUMENTS INSTALLED IN THE INSTIT
Page 33 and 34: Sumatra low oxygen concentration wa
Page 35 and 36: 7. Studies on some major constituen
Page 37 and 38: 2. Chemical investigation on marine
Page 39 and 40: Twentyfour hydrocarbon-utilizing st
Page 41: amount of silt gets carried away by
Page 45 and 46: terrace (350-400m depth range), a b
Page 47 and 48: sample is high in the inner shelf t
Page 49 and 50: 2. Effluent discharge sites studies
Page 51 and 52: 2. Extracellular production Studies
Page 53 and 54: (ix) Marine fauna at Malvan: Intert
Page 55 and 56: Kandelia rheedii and Rhizophora muc
Page 57 and 58: 9. Microbiological studies Water sa
Page 59 and 60: (d) Artemia culture: A one acre sal
Page 61 and 62: to determine the heavy metal concen
Page 63 and 64: Technical Assistance Programme. Thi
Page 66 and 67: 3.6 Marine Instrumentation 3..6.1 D
Page 68: The buoy is expected to be launched
Page 71 and 72: 2. Cruise Reports (cruise Nos. 66 t
Page 73 and 74: (i) 'Monex' data of CSTD, MBT, XBT,
Page 75 and 76: Location of Headquarters & Regional
Page 77 and 78: sections, 18°N across the Bay of B
Page 79 and 80: A.3 Protection of marine environmen
Page 81 and 82: The industrial effluents discharged
Page 83 and 84: chlorinity values (0·02%o). Signif
Page 85 and 86: Major peaks were noticed in the mon
Page 87 and 88: and geochemistry of the continental
Page 89 and 90: showed that: (a) out of 50 tracks i
Page 91 and 92: and fishing harbour areas. The surv
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Some clients of NIO 1 Alkali and Ch
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3.10.2 Culture of mussels, oysters
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machine. 4.3 Library With the acqui
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Λ view of Library A view of worksh
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18. Dr. E. G. Silas " Cochin. 4. Dr
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7. Dr. B. N. Desai " Scientist-in-C
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5.8 Grievance Committee 1. Dr.V. V.
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Junior Research Fellows Shri M. Dil
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Scientists Shri V· S. Rama Raju Dr
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Visit of Chief Minister of Goa, Dam
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7 Colloquia Speaker Subject Date 1
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8 Awards, honours and membership of
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— Member, Biosphere, Forest and W
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period of six months (January to Ju
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Dr. R. Sen Gupta participated and d
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International Seminar on India and
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3. Various low-cost equipment for h
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Dr. A. B. Wagh 11 Radio Talks 1 2 3
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Fondekar, S.P., R.S. Topgi and R.J.
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Nair, Vijayalakshmi R., 1980. Produ
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Setty, M.G.A.P., R. Williams and K.
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Madhupratap, M., 1980. Progresss in
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NATIONAL INSTITUTE OF OCEANOGRAPHY
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1980 - National Institute of Oceanography

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