Mapping of basement structure beneath the Kohima Synclinorium, north-east India via Bouguer gravity data modelling

Abstract

Kohima Synclinorium is one of the most tectonically active corridors of Indian subcontinent and displays complex tectonics of the region. Mapping the basement structure beneath the Kohima Synform is, therefore, vital to provide deep insight into the understanding of the crucial thrust geometry of the region. The vertical gravity gradient anomalies and available geological evidences suggest that the underlying area is occupied by thrust geometry embedded with prominently known tectonic trends of Schuppen Belt (SB), Kohima–Patkai Synclinal (KS–PS) and adjoining Inner Fold Belts (IFB). By keeping in view the massive complex tectonic upheaval in the region, we carried out 2D Bouguer gravity data analysis using the radially averaged power spectral techniques and GMSYS modelling to map the basement depth more precisely. Our results suggest that there is a wide range of heterogeneity in the underlying undulating basement indicating an average sedimentary thickness of the order of 2.2–5.5 km. The gravity PDEPTH modelling results show that source depth varies from 2.5 to 6.5 km. There is an uplifted basement tending towards the southwestern part while gradual deepening of basement was observed towards the eastern part of the study area. The profile modelling results show the presence of basement in a depth range of 2.5–3.8, 3.8–4.0, and 3.8–4.2 km beneath Foreland Basin (FB), Kohima–Patkai Synclinal structures (KS–PS), and Inner Fold Belts (IFB), respectively. The underlying results of integrated profiles, PDEPTH and GMSYS modelling would be useful to understand the detailed basement structure and tectonic trends of Belt of Schuppen (BS), Kohima–Patkai Synclinal structures (KS–PS) and adjacent Inner Fold Belts (IFB) of north-eastern region of India.