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V. N. Kodagali ¹

Affiliations
1 National Institute of Oceanography, Donapaula, Goa 403 004, IN

Abstract

Morphometric and slope angle studies carried out on a part of Indian Ocean Basin have shown that gentle slope angle ranges dominate, 92% of the area represented by 0-3° slopes. Young's hypothesis of log-normal distribution of slope angle frequencies is found to be valid for deep sea topographic data also. Elevation-relief ratios and ruggedness values are relatively high for the southern portion of the study area whereas these values are less in the northern portion. Some of the features like abyssal hills and the seamount recorded in the region might have been formed due to volcanism. Some secondary topographic features could have resulted due to post-depositional processes. Slope angle, elevation-relief and ruggedness can be used in inferring certain features in the oceanic surface.

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P. S. Rao ¹, V. N. Kodagali ¹, T. Ramprasad ¹, R. R. Nair ¹

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa-403 004, IN

Abstract

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.

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J. N. Pattan ¹, G. Pratibhan ², C. Prakesh Babu ², N. H. Khadge ¹, A. L. Paropkari ², V. N. Kodagali ¹

Affiliations
1 National Institute of Oceanography, Dona Paula-403004, Goa, IN
2 National Institute of Oceanography, Dona Paula -403004, Goa, IN

Abstract

A closely spaced 75 surface sediments drawn from "Gas Hydrate" Project taken up by National Institute of Oceanography on a regional scale from the Krishna- Godavari Basin (Latitude 15°35' to 16°20' N; Longitude 81° 40' to 82°30E) are analysed for texture, major, and some trace and rare earth elements to understand their source and provenance. Water depth in the study area varies between 300 to 2000 m and there is a WNW-ESE trending sedimentary ridge in the southwestern part of basin. Sediments are mosdy silty clay in nature. Ti - bearing minerals such as titanite and pyrophanite are evident by the strong positive correlation between Ti and Ca (r = 0.89) and Ti and Mn (r =0.67) respectively. An independent behaviour of Zr suggests occurrence of zircon mineral. The strong positive correlation among Al, Fe, Mg and K (r = 0.68 to 0.90) suggests their association with clay. The average total REE (Σ2REE 176±13 ppm) abundance is similar to that of average shale with a flat shale- normalized REE pattern suggest a terrigenous source. High concentration of Fe (6.45±0.43% ), Ti (0.82+0.07%), V (192±23 ppm), Cr (128±13 ppm) and Zr (159±19 ppm) and presence of smectite as a major clay mineral suggest that Peninsular Godavari River has sediment influx from source rocks of Eastern India mainly Deccan Trap, Precambrian and Dharwar formation. Further, it confirms that the role of Ganges-Brahmaputra River sediments to the basin appears to be small compared to the Peninsular rivers.

Keywords

Surface sediments, Geochemistry, Silty clay, Smectite, Titanite, Pyrophanite, Zircon, Bathymetry, Krishna-Godavari Basin, East Coast of India.

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