V. Vijaya Rao

Evolution of Proterozoic Aravalli Delhi Fold Belt in the northwestern Indian Shield from seismic studies

A deep seismic reflection study across the Aravalli Delhi Fold Belt, situated in the northwestern part of the Indian Shield, has revealed a deep penetrating 25-km-wide crustal-scale thrust fault, dipping reflections from the upper crust to the Moho and a divergent reflection fabric. Paleo-subduction zones and island-arc signatures are identified from the present study. Seismic images of the crust reveal tectonics of the region with two distinct episodes of rifting, sedimentation, collision and suturing corresponding to the Aravalli and Delhi orogenies. Plate tectonic processes were responsible for the evolution of the Paleoproterozoic Aravalli and Mesoproterozoic Delhi Fold Belts with the juxtaposition of the Bundelkhand craton in the east and the Marwar craton in the west. A 50-V m electrical conductor, extending to a depth of 25 km, and a steep gradient gravity anomaly of 70 mGal, extending all along the strike of the fold belt with conspicuous lows on either side, correlate well with the deepseated dipping reflections/sutures inferred from the seismic reflection data. The present study suggests that a high-velocity, thick crust was produced in the Proterozoic orogens of the region. q 2000 Elsevier Science B.V. All rights reserved.

Structure and tectonics of the Proterozoic Aravalli-Delhi Fold Belt in northwestern India from deep seismic reflection studies

Abstract Seismic imaging of the crust along a 400-km-long deep seismic reflection profile across the Palaeo/Mesoproterozoic Aravalli-Delhi Fold Belt, in the northwestern Indian Shield, brings into focus its complex structure and provides clues to understand the geological processes involved in the evolution of this belt. The reflectivity pattern varies considerably for different crustal units along the profile. The deep-crustal reflection data image two sets of oppositely dipping strong reflection bands, from upper- to lower-crustal levels. These are identified as the signatures of the collision corresponding to Aravalli and Delhi orogeny. The data also exhibit a clear Moho and strong lower-crustal reflections near the collision boundaries. A stack of dipping reflections from the top of the Moho to the surface is identified as a major thrust fault indicating that the Proterozoic collision and deformation were primarily thick-skinned in nature

Deep seismic reflection study over the Vindhyans of Rajasthan: Implications for geophysical setting of the basin

This paper presents results of high-resolution deep seismic reflection profiling of the Proterozoic Vindhyan basin of the Rajasthan area along the Chandli-Bundi-Kota-Kunjer profile. Seismic images have been used to estimate the thickness of Vindhyan strata as well as to understand the tectonic framework of the basin. The results are constrained by gravity, magnetic and magnetotelluric data. The study reveals gentle SE-dipping reflection bands representing the Vindhyan strata. The seismic sections depict gradual thickening of the Vindhyan succession towards southeast from Bundi. The velocities of the upper and lower Vindhyans are identified as 4.6-4.8 km/s and 5.1-5.3 km/s. The NW limit of the Vindhyan basin is demarcated by the Great Boundary Fault (GBF) that manifests as a 30 km wide NW dipping thrust fault extending to a depth of 30 km.