Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

K. V. L. N. S. Sarma ¹, M. V. Ramana ¹, G. P. S. Murty ¹, V. Subrahmanyam ¹, K. S. Krishna ¹, A. K. Chaubey ¹, M. M. Malleswara Rao ², S. L. Narayana ²

Affiliations
1 National Institute of Oceanography, Donapaula, Goa - 403004, IN
2 National Institute of Oceanography, Regional Centre, Visakhapatnam-530023, IN

Abstract

Analysis of the total intensity magnetic data over the western Andaman shelf has been carried out for determination of depth to magnetic basement using the Analytical signal and Werner Deconvolution methods. The basement depths are refined with optimisation procedure of iteration modelling. The depths Derived from these methods match well with the acoustic basement mapped by the seismic reflection survey across the Andaman shelf. The interpretation by these methods demonstrates the rapid utility in virgin areas forderiving the first order basement configurationquickly. The gradual slope of the basement from west to east on the western Andaman shelf may be attributed to the ongoing process of the subduction of the older crust in the Sunda Trough.

Keywords

Marine Geophysics, Andaman Sea.

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L. V. Subba Raju ¹, K. S. Krishna ¹

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

Abstract

Complete descriptions and basic facts of nine gravity stations of Marmugao harbour are presented. They exhibit a maximum Bouguer difference of 2.12 mGal in an overall distance of about 2 km. Keeping in view the limited amount of data, certain broad and tentative conclusions regarding crustal structure are drawn.

Keywords

Gravity Stations, Crustal Thickness, Goa.

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D. Gopala Rao ¹, K. S. Krishna ²

Affiliations
1 Department of Geology, Osmania University, Hyderabad - 500 017, IN
2 National Institute of Oceanography, Dona Paula, Goa - 403 004, IN

Abstract

Compressional wave velocities (Vp) and index properties of 70 mini- gabbroic rock- core samples of 2.5 cm diameter x 2.1 cm long from 157.1 m below seafloor in Hole 1105A of the Atlantis Bank, Southwest Indian Ridge, were measured in the laboratory. Comparison of the Vps and onboard lithostratigraphy revealed that the Vps of the gabbros and olivine gabbros are very close and have the values 6.74±0.04 and 6.7±0.07 km/s , respectively. Oxides and oxide olivine gabbros have markedly lower Vps (6.53±0.076 and 6.59±0.077 kds) respectively as abundance of Fe-Ti oxide ' minerals vary as a result of alteration processes. They are also consistent with well-log results of Hole 1lO5A and Hole 735 B from the bank. The mean bulk density of the rocks is 2.93±0.15 gm/c³. The other index properties - porosity, void ratio and grain density and their means are consistent with model populations of the rock minerals.

Keywords

Compressional wave velocities, Physical properties, Cores, Gabbroic rocks, Atlantis Bank, Southwest Indian Ridge.

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P. Divakar Naidu , G. C. Bhattacharya ¹, A. K. Chaubey ¹, K. S. Krishna ¹

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

Abstract

No Abstract.

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