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Crustal structure and tectonics of the Ninetyeast Ridge from seismic and gravity studies

DRS at CSIR-National Institute of Oceanography

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Title Crustal structure and tectonics of the Ninetyeast Ridge from seismic and gravity studies
 
Creator Krishna, K.S.
Neprochnov, Y.P.
Rao, D.G.
Grinko, B.N.
 
Subject crustal structure
tectonics
seismic refraction profiles
grvity data
bathymetric data
ridges
 
Description Seismic reflection and refraction, gravity, and bathymetric data across and along the central part of the Ninetyeast Ridge were analyzed to determine the crustal structure of the ridge and to understand its tectonics. The ridge in the study area rises to approx. 3.5 km above the seafloor of adjacent ocean basins. Basement is covered by sediments up to 0.8 km thick but exposed at some locations. Seismic refraction and gravity models of the ridge show that the crustal thickness is approx. 22 km, greater than the average thickness (7 km) of oceanic crust estimated in the Central Indian and Wharton Basins. The ridge is compensated by flexure of layers 2A, 2B, and 3A to the extent of approx. 2 km and by a 12 km thick deep crustal body (layer 3B) of underplated material. Upper crustal velocities (layer 2A) beneath the ridge are lower, up to 3.4 km s sup(-1) than in adjacent basins because of weathering process and hydrothermal circulation of the waters in the tectonized blocks. While velocities in deep crustal body (layer 3B) are higher, up to 7.8 km s sup(-1) and seem to be resulted from magmatic rocks accreted within the lithosphere. Steep downward faulting of approx. 2 km along the eastern flank of the Ninetyeast Ridge possibly originated because of compressional and extensional stresses applied along the 89 degrees E Fracture Zone (FZ). The stresses are interpreted as resulting from multiple ridge jumps of Wharton spreading centers during the Late Cretaceous and middle Eocene. The velocity-depth model suggests that the rocks of layers 2A and 2B and layer 3A are exposed on the eastern flank of the Ninetyeast Ridge and 90 degrees E FZ, respectively. They are consistent with basalt, dolerite, and gabbro rocks, collected from the fault scarps. The central part of the ridge between 1 degree N and 11 degrees S has uniformly deepened by approx. 0.7 km and is bounded by major sublatitudinal deep-seated fractures. It is interpreted that the deepened structural block and associated fractures resulted from the activity of the intense deformation of the central Indian Ocean
 
Date 2009-01-07T10:43:42Z
2009-01-07T10:43:42Z
2001
 
Type Journal Article
 
Identifier Tectonics, Vol.20; 416-433p.
http://drs.nio.org/drs/handle/2264/1561
 
Language en
 
Rights Copyright [2001]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
 
Publisher American Geophysical Union