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Radhakrishna, M.
- Petrogenesis of the Perinthatta Anorthosite, Northern Kerala, India
Authors
1 Department of Marine Geology and Geophysics, Cochin University of Science & Technology, Cochin - 682 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 50, No 4 (1997), Pagination: 501-509Abstract
The anorthosite pluton has textural and trace element characteristics typical of a magmatic cumulate. A soda-rich intermediate magma is inferred to be the parent. Rare earth element based modelling shows that the anorthosite was derived from a parental melt having hundred times chondritic REE with a slightly fractionated pattern probably derived by the melting of granulitic or edogitic source.Keywords
Petrogenesis, Anorthosite, Proterozoic Magmatism, Kerala.
- Estimates of Effective Elastic Thickness along the Southwest Continental Margin of India using Coherence Analysis of Gravity and Bathymetry Data - Geodynamic Imlication
Authors
1 201/C, ISM House, Thakur Village, Kandivali (East), Mumbai - 400 101, IN
2 Department of Earth Sciences, IIT Powai, Mumbai, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 4 (2008), Pagination: 593-595Abstract
No Abstract.Full Text
- Geophysical Structure of Western Offshore Basins of India and its Implications to the Evolution of the Western Ghats
Authors
1 201/C, ISM House, Thakur Village, Kandivali (East), Mumbai-400 101, IN
2 Department of Earth Sciences, IIT Powai, Mumbai, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 4 (2008), Pagination: 595-596Abstract
No Abstract.Full Text
- Geophysical Structure of Western Offshore Basins of India and its Implications to the Evolution of the Western Ghats
Authors
1 E and P Division, Essar Oil Ltd, Mumbai 440 034, IN
2 Dept of Marine Geology and Geophysics, Cochin University of Science and Technology, Fine Arts Avenue, Cochin 682 01 6, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 3 (2007), Pagination: 445-458Abstract
Western Ghats lies to the east of two prominent basins of western offshore viz( 1 ) Mumbai offshore basin (2) Konkan-Kerala offshore basin. These basins have evolved in a divergent continental margin setting as a consequence of break up of Madagascar in Mid Cretaceous and Seychelles in Late Cretaceous from Indla. The basic framework of the Western Continental Margin of India was established by the end of Cretaceous.
The Surat depression in the north and the Vengurla Arch in the south define Mumbai offshore basin. Shelf marglin basin marks its western limit. The width of the shelf is -230 km. The entire shelf from the coast towards the shelf margin zone is segmented by basement controlled NW-SE to N-S faults giving rise to many horst graben features. The Konkan-Kerala basin located south of the Vengurla Arch has an average width of - 75 km. Eastern fringe of the basin extends to the land along the Kerala coast where outcrops of Miocene are preserved. In the west a number of NNW-SSE trending Laxmi-Laccadive and Koil-Comorin ridges separated by depressions are identified. The basin is more differentiated in Eocene/Oligocene section with N-S trending horsts and grabens.
The seismic data in the basins show prominent N-S fault trends. The data further indicate the presence of strike-slip movement and associated flower structures. Therefore, the geophysical and drillng data in the western offshore support a plate tectonic model for structural styles as a result of fragmentation initliated by transform faulting. The basins came into existence in late Cretaceous and evolved through Tertiary. Extensive lava flows at 65 Ma are attributed as a fissure type eruption through transform faults during Deccan volcanism. The Western Ghats may therefore, be the result of rifting and severe faulting with initial uplift and tilt to the east. The west coast of India was further elevated during the Tertiary in successive phases. The removal of vast quantities of rocks from the onshore its deposition in the offshore basins and the associated flexuial responses might have resulted in the present day Western Ghats escarpment.
Keywords
Geophysics, Structure, Evolution, Offshore Basins, Western Ghats.- Estimates of Effective Elastic Thickness along the Southwest Continental Margin of India Using Coherence Analysis of Gravity and Bathymetry Data - Geodynamic Implications
Authors
1 Department of Marine Geology and Geophysics, School of Marine Sciences, Cochin University of Science and Technology, Fine Arts Avenue, Cochin - 682 016, IN
2 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 3 (2007), Pagination: 475-487Abstract
The southwest continental margin of India has evolved due to rifting between India and Madagascar at 88 Ma and subsequent seafloor spreading. During this period, several major ridges and horst-graben structures were formed at the margin. In the southern most part, the Comorin Ridge aligned along the margin, is another topographic feature believed to be related to the earliest phase of margin evolution. In the present study, Coherence analysis of gravity and bathymetry data of the region based on Maximum Entropy Spectral Estimation (MESE) method is used to understand the regional geodynamic processes and lithospheric strength that controls the flexure and basin evolution. The study brings out effective elastic thickness (Te) values of 5-10 km along the Konkan and Kerala basins, and the Comorin Ridge at the margin and 5-8 km along the Chagos Laccadive Ridge north of the equator. The elastic thickness values increase southward and maximum Te value of 10 km is observed below the Comorin Ridge. These results, combined with the earlier estimates of Te indicate low strength < 15 km for the lithosphere below the western margin, but not as low as that observed below plume affected margins. The observed low elastic strength at the margin will have implications on long term topographic evolution of the Western Ghats.
The Marion Plume seems to have played limited role in the rifting and evolution process of the western margin. In the absence of such an active plume role, the substantial partial melt zone observed in the Comorin Ridge region based on geomagnetic induction models can be alternatively explained by invoking the convective partia1 melting model. The Comorin Ridge might have been emplaced as an oceanic basement high due to large-scale volcanism during the onset of seafloor spreading. Absence of diagnostic magnetic signature associated with the isostatic gradient over the Comorin Ridge that marks the Ocean Continent Boundary indicates that active volcanism due to strong convection might have blurred the crustal transition in the Comorin Ridge region.