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Free keywords:
crustal structure, Dharwar craton, Poisson's ratio, receiver functions, shear velocities
DDC:
550 - Earth sciences
Abstract:
Teleseismic data from six broad-band stations on the south Indian shield have been analysed, primarily to examine the differences in the crustal structure between the eastern and western units of the Archaean Dharwar craton. SV receiver functions for these stations have been computed and modelled down to the Moho level in terms of Poisson's ratio and shear wave velocities. Results show that the crust for the entire Dharwar craton is mainly simple, and has a low (about 0.25) Poisson ratio. It is usually thinner and less complex than the adjacent Proterozoic crust. However, the western Dharwar craton crust (thickness 41 km) with a gradational Moho boundary, is substantially (>7 km) thicker than its eastern counterpart (thickness 34 km). No substantial differences in average crustal S velocities (3.6-3.8 km s 1) were found. The eastern Dharwar crust below the Proterozoic Cuddapah basin was also found to have remained relatively simple and undisturbed. The continental margin to the west of the Dharwar craton appears to have shifted further west off the coast, where a possible west coast fault has down-thrown a continental crustal block under the seas. The crust constituting the Deccan volcanic province in the western Indian shield is found to be similar to that of the eastern Dharwar craton. The crust underneath the neighbouring Godavari graben is significantly different from the Dharwar crust and resembles that of a typical rift-valley.
