A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Subrahmanyam, C.
- On the Relation of Gravity Anomalies to Geotectonics of the Precambrian Terrains of the South Indian Shield
Authors
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 19, No 6 (1978), Pagination: 251-263Abstract
Geological implications of the Bouguer gravity anomalies over the various structural provinces and their boundaries in the South Indian shield are discussed. The widely distributed greenstone belts and granites of Karnataka and Bastar craton show belts of positive and negative anomalies respectively, and control in a significant manner the Bouguer anomaly contour pattern over these low-grade terrains. The high grade Eastern Ghat terrain is divisible into two sectors whose geological and geophysical characteristics differ, as also their relationships with the adjacent low-grade terrains. While both represent deep crustal level ischolar_main zones, the Tamil Nadu-Kerala granulite terrain appears to be exposed due to crustal tilting and continues northward underneath the Archean Karnataka craton. On the other hand, the Coastal granulite terrain is in faulted contact with the adjoining cratons. A strong negative anomaly flanking the western margin of this terrain is caused by downfiexuring of the crust along the cratonic margin.- Geodynamics of the Indian Peninsula and the Indian Plate Margin
Authors
1 National Geophysical Research Institute, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 40, No 2 (1992), Pagination: 191-192Abstract
No Abstract.- 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.
Keywords
Gravity, Coherence, Effective Elastic Thickness, Continental Margins, Comorin Ridge, Konkan And Kerala Basin, Western Ghats, India.- Gas-Hydrates - A Synoptic View
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN