• B Nageswara Rao

      Articles written in Journal of Earth System Science

    • Structural mapping based on potential field and remote sensing data, South Rewa Gondwana Basin, India

      Swarnapriya Chowdari Bijendra Singh B Nageswara Rao Niraj Kumar A P Singh D V Chandrasekhar

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      Intracratonic South Rewa Gondwana Basin occupies the northern part of NW–SE trending Son–Mahanadi rift basin of India. The new gravity data acquired over the northern part of the basin depicts WNW–ESE and ENE–WSW anomaly trends in the southern and northern part of the study area respectively. 3D inversion of residual gravity anomalies has brought out undulations in the basement delineating two major depressions (i) near Tihki in the north and (ii) near Shahdol in the south, which divided into two sub-basins by an ENE–WSW trending basement ridge near Sidi. Maximum depth to the basement is about 5.5 km within the northern depression. The new magnetic data acquired over the basin has brought out ENE–WSW to E–W trending short wavelength magnetic anomalies which are attributed to volcanic dykes and intrusive having remanent magnetization corresponding to upper normal and reverse polarity (29N and 29R) of the Deccan basalt magnetostratigrahy. Analysis of remote sensing and geological data also reveals the predominance of ENE–WSW structural faults. Integration of remote sensing, geological and potential field data suggest reactivation of ENE–WSW trending basement faults during Deccan volcanism through emplacement of mafic dykes and sills. Therefore, it is suggested that South Rewa Gondwana basin has witnessed post rift tectonic event due to Deccan volcanism.

    • Three-dimensional Moho depth model of the eastern Indian shield and its isostatic implications


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      The Singhbhum Craton, Singhbhum Mobile Belt along its northern, eastern, and western edges, and Chotanagpur Gneissic Complex farther north are all parts of the Precambrian eastern Indian shield. Modern isotope dates and associated geological evidence suggest that these crustal units may be one cratonic block that developed sequentially between 3.55 and 1.00 Ga. The region has always been the focus of numerous geoscientific studies due to its complex evolutionary history and abundant mineralisation. We used the terrestrial gravity data from the Gravity Map Series of India and the EGM2008 global gravity dataset in the Bay of Bengal to model the 3D Moho geometry of the eastern Indian shield and the adjoining Bay of Bengal by inverting the gravity data. The Bouguer gravity data were filtered at several levels before applying the Parker–Oldenburg iterative inversion procedure. The Moho depth measurement is then computed by presuming a constant density contrast. The effects of sediments were eliminated from gravity data by collecting thickness and density details of the sediment from a worldwide sedimentary thickness map CRUST1.0 and applying a correction comparable to the Bouguer correction that uses the density difference of 0.24 g/cm$^3$. Spectral analysis is used to fix a reference depth level and the low-frequency range associated with Moho deflection in the Bouguer anomaly filtered for sedimentary overburden. We subsequently executed the gravity inversion of a basic two-layer structure having aconstant density difference of 0.40 g/cm$^3$ across the Moho fixed at an average depth of 35 km. The gravity inversion analysis shows that the Moho depth within the Bay of Bengal is between 18 and 24 km. In the continent, the Moho depth varies from 34 km near the coastline to 38 km towards the Singhbhum Cratonand Chhotanagpur Gneiss Complex. In the northern portion of the region, the Moho depth increases to over 40 km underneath the convergence of the Mahanadi–Damodar Gondwana basins and the Ganga foreland basin.

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