Central Indian tectonics revisited using aeromagnetic data

Abstract

Aeromagnetic data, covering 600,000 km 2 of Central India, have been analysed for the first time to throw light on the various tectonic blocks of the region, ranging in age from the Archean to the present. Existing geotectonic models are based on inadequate data and studies of relatively small regions. From the aeromagnetic data, we use the analytic signal and Euler deconvolution, to elucidate the subsurface structure of the region and redefine the tectonic elements. Contrary to the belief that the Central Indian shear defines the edge of the Central Indian craton, we find that the Sukinda thrust merges with the Tan shear to demarcate the edge of the Bastar and Eastern Ghat blocks by a shear that extends for approximately 1000 km in length. We call this the Main Peninsular shear. Magnetic anomaly data can thus play a crucial role in understanding the tectonic elements of a region with large surface cover.

Crustal density structure across the Central Indian Shear Zone from gravity data

“…The regional E-W gravity gradient and structural grain on the CITZ is concordant with the CISZ while the N-S gravity gradient and structural grain of the Bastar Craton is discordant with it. The aeromagnetic map of the Central India also shows that the contours of CITZ are oriented in E-W direction in contrast to the NW-SE Dharwarian trend which appears to dominate the Bastar Craton (Rajaram and Anand, 2003). Gradient analysis of gravity data thus validates the contention that CISZ separates two distinct Precambrian crustal domains, which have been brought in juxtaposition due to northward subduction of the Bastar Craton below the Bundelkhand Craton (Bhowmik et al, 1999;Acharyya and Roy, 2000;Roy and Prasad, 2003;Roy et al, 2006;Mall et al, 2008).…”

“…It was proposed that the crustal scale CISZ bounding these domains has allowed the juxtaposition of Bundelkhand and Bastar cratons during Palaeo-to Mesoproterozoic period (Yedekar et al, 1990;Bhowmik et al, 1999;Roy and Prasad, 2003). Though the complimentary geophysical studies addressed the nature of deep crustal structure across the CISZ (Mishra et al, 2000Rajaram and Anand, 2003;Mall et al, 2008), the proposed evolutionary models are still under debate (e.g., Naganjaneyulu and Santosh, 2010).…”

“…Several geophysical studies employing active seismology (e.g., Sain et al, 2000;Tewari and Kumar, 2003;Murty et al, 2008), potential field data (e.g., Mishra, 1992;Verma and Banerjee, 1992;Singh and Meissner, 1995;Singh, 1998;Rajaram and Anand, 2003) and magnetotelluric (e.g., Gokarn et al, 2001;Patro et al, 2005;Naganjaneyulu, 2010;Naganjaneyulu and Santosh, 2010; provide deep insights into the crustal structure and tectonic evolution of the CITZ. In contrast the only coincident seismic reflection and refraction/wide-angle reflection study along Seoni-Kalimati profile provided some vital information about its crustal configuration (Reddy et al, 1996).…”

Mapping of magnetic basement in Central India from aeromagnetic data for scaling geology

“…The crustal anomaly map generated after gridding the data at 1 km interval, represented in Fig. , is found to depict signatures of major geological and tectonic units of Central India (Rajaram and Anand ). We used these data and selected 143 blocks of dimension 100 km × 100 km with an overlap of 50 km.…”

“…Aeromagnetic map of the Central India overlain by the main geological and tectonic units. Geological units are shown by different symbols, whereas abbreviations of the geological units are the same as described in Figure (Geological Survey of India ; Rajaram and Anand ).…”