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Nair, R. R.
- Holocene Limestones of Part of the Western Continental Shelf of India
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Authors
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa-403004, IN
1 National Institute of Oceanography, Dona Paula, Goa-403004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 20, No 1 (1979), Pagination: 17-23Abstract
Dredging on the western continental shelf of India has shown that the most common rock types outcropping on the irregular topography of the outer shelf (70-90 m) are algal limestones and shelly limestones containing superficial ooids and pelletoids, while those on the upper continental slope (130-180 m) are algal bryozoan limestones. The limestones have a radiocarbon age ranging between 9,000 and 11,000 years. Depositional environment on the continental shelf during the Holocene appears to be characterised by shallow waters in association with lagoon-barrier beach environment.- Heavy Minerals in the Sediments on the Outer Continental Shelf between Vengurla and Mangalore on the West Coast of India
Abstract Views :178 |
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Authors
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa 403004, IN
1 National Institute of Oceanography, Dona Paula, Goa 403004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 22, No 1 (1981), Pagination: 32-38Abstract
Fifty-eight sediment samples from the outer continental shelf between Vengurla and Mangalore were analysed for heavy mineral content. The heavy minerals consist of principally opaques, hornblende, epidote, garnet, sillimanite, hypersthene and zircon, with minor amounts of andalusite, augite, kyanite, monazite, muscovite and tremolite-actinolite. This mineral assemblage and the distribution pattern define four heavy mineral provinces on the continental shelf from Vengurla to Mangalore. Further, the mineral assemblage suggests derivation from mixed metamorphic and igneous terrain with a predominant contribution from metamorphic rocks.- Surficial Sediments of the Continental Shelf off Karnataka
Abstract Views :178 |
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Authors
N. H. Hashimi
1,
R. R. Nair
1
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa 403004, IN
1 National Institute of Oceanography, Dona Paula, Goa 403004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 22, No 6 (1981), Pagination: 266-273Abstract
The continental shelf in this area is about 80 km wide and the edge of the shelf varies between 90 and 120m water depth. Geologically modern fine-grained clastic sediments occur between the water depths of 15 to 50m corresponding to a distance of about 40 km from the coast. Beyond 50 m to the shelf edge are calcareous sands. Noncarbonate components of these deep water sands are essentially quartz, many of which are heavily iron-stained and are attributed to the presence of rich iron formation on the land. The carbonate components in the outer shelf sediments are mainly foraminifers, pelecypods, gastropods, pteropods, and ooids, while ooids and pteropods are absent on the inner shelf. X-ray mineralogy of the silt fraction of the sediments shows the presence of quartz, calcite, aragonite and orthoclase as major minerals. Some of the sedimentary processes effecting the distribution of these sediments are discussed.- Clay Mineral Distribution on the Kerala Continental Shelf and Slope
Abstract Views :192 |
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Authors
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa 403 004, IN
1 National Institute of Oceanography, Dona Paula, Goa 403 004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 24, No 10 (1983), Pagination: 540-546Abstract
Seventy-five sediment samples collected from the Kerala continental shelf and slope during the 17th and 71st Cruises of RV Gaveshani were analysed by X-ray diffraction for clay mineral content. The distribution of total clay < 4μ fraction) indicates low percentages < 10%) on the outer shelf and high percentages on the inner shelf (20 to 50%) and upper continental slope (11 to 47%). The clay minerals are composed of montmorillonite (smectite), kaolinite, illite and gibbsite and the nonclay minerals are quartz and feldspar. Kaolinite and gibbsite have low values on the outer shelf and high values on the inner shelf and slope, while illite increases in the offshore direction. However, montmorillonite behaves differently from others in having high values on the outer shelf and low values on the inner shelf and slope. These variations in the clay mineral distribution have been attributed to differences in the energy of the various environments and due to size segregation of the minerals.- Morphology of a Coral Bank, Western Continental Shelf of India : A Multibeam Study
Abstract Views :238 |
PDF Views:1
Authors
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa-403 004, IN
1 National Institute of Oceanography, Dona Paula, Goa-403 004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 41, No 1 (1993), Pagination: 33-37Abstract
Morphology of a living coral bank (Gaveshani Bank) is described using multibeam swath bathyrnetric survey system Hydrosweep. The bank has a height of 42 m, length of 2 km and a maximum width of 1.66 km, with steep flanks and flat top. It has a north-souh orientation and occupies an arca of about 3 sq km. A 100% coverage obtaincd in the present study enables us to determine the exact morphology of the bank. A comparison with the single beam echosounding data reveals that the dimensions (length and breadth) and areal extension of the bank are much larger than previously known.Keywords
Coral Bank, Morphology, Multibeam Bathymetry, Western Continental Shelf of India.- Holocene Sea Level Fluctuations On Western Hndian Continental Margin: An Update
Abstract Views :175 |
PDF Views:1
Authors
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa-403 004, IN
2 Birbal Sahni Institute of Palaeobotany, Lucknow-226 007, IN
1 National Institute of Oceanography, Dona Paula, Goa-403 004, IN
2 Birbal Sahni Institute of Palaeobotany, Lucknow-226 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 2 (1995), Pagination: 157-162Abstract
A new Holocene curve is generated for the western Indian continental margin. While constructing this curve careful selection of the dates were made by giving due considerations to the genetic characteristics of the dated material. This new curve shows a low at 100 m depth around 14,500 years BP and a rise to 80.m depth around 12,000 years BP showing a rate of ˜10m/1000 years which was followed by astillstand for about 2,000 years. From 10,000 to 7,000 years it rose at a very high rate (˜20 m/1000 years). Beyond 7,000 years BP it showed minor fluctuations.Keywords
Holocene, Sea Level Fluctuation, Sea Level Curve, Arabian Sea, West Coast of India.- Bathymetric Study of the Neotectonic Naini Lake in Outer Kumaun Himalaya
Abstract Views :180 |
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Authors
N. H. Hashimi
1,
M. C. Pathak
1,
P. Jauhari
1,
R. R. Nair
1,
A. K. Sharma
2,
S. S. Bhakuni
2,
M. K. S. Bisht
2,
K. S. Valdiya
2
Affiliations
1 National Institute of Oceanography, Goa - 403 004, IN
2 Department of Geology, Kumaun University, Nainital - 263 002, IN
1 National Institute of Oceanography, Goa - 403 004, IN
2 Department of Geology, Kumaun University, Nainital - 263 002, IN