Geomorphotectonics of the Basement in a Part of Upper Son Valley of the Vindhyan Basin

Abstract

Ground magnetic survey of part of central India covering the Vindhyan Basin of the upper Son valley region has delineated some subsurface vsolcanogenic Proterozoic rifts below the Vindhyan cover and several faults which have controlled the tectonics of the region. The magnetic map in general shows four distinctly different domains with magnetic anomalies differing both in amplitude and their nature. In general, the Vindhyan basin is characterized by low amplitude broad anomalies while the Mahakoshal (lower Proterozoic) Group depicts large amplitude sharp anomalies due to the presence of high susceptibility (2-19 í— 10^-3 CGS units) ferruginous rocks in them. The domain boundaries are either faults or indicate formational contacts between the different types of rocks with contrasting susceptibility values.

The subsurface basement relief map of the Pre-Vindhyan topography determined by 2-dimensional Harmonic Inversion of the magnetic data reveals an asymmetric graben structure with the southern boundary fault between the Vindhyans and the Mahakoshals as the most prominent linear structure.