Post-deformation effects of Indo-Eurasia convergence on major geological features of north-central India: New insights from satellite gravity observations

Abstract

The north-central region of the Indian subcontinent, which lies close to the Indo-Eurasian convergence zone, is concealed by ∼66 Ma Deccan volcanics and thick Proterozoic-Tertiary sedimentation, and as such its sub-surface structural configuration is not well understood. In the present study, we analyse high-resolution satellite gravity data over this region in order to probe deep structural fabric of the major geotectonic blocks and associated sedimentary sequences. The residual gravity field, deduced using Finite Element Method, clearly demarcates boundaries of the major geotectonic units of this region, which remained unknown. Our study indicates that the extent of the Bundelkhand cratonic segment is much larger than hitherto known, which extends from the eastern margin of Aravalli-Delhi Fold Belt to almost central part of the Indo Gangetic Plain. Similarly, Shillong Plateau located in northeastern part of India, characterized by a broad high-order positive residual gravity anomaly closure, extends between 86° E to 94° E, far beyond its currently known extent. Importantly, this massif is undergoing in-land rifting due to the regional neotectonic activities associated with Indo-Eurasia convergence and the compressive forces generated between India and Indo-Burmese collision zone. We modelled the gravity anomalies along four N-S profiles across the Narmada-Son Lineament (NSL), which clearly reveal that the Vindhyan sediments, whose extent were considered to be limited to the north of NSL only, was found to be extending further south across this lineament. In addition, a prominent ENE-WSW high-density ridge structure, paralleling the Himalayan arc, is also identified, which is also possibly formed due to N-S stresses, generated by the collision between Indian and Eurasian plates during early Tertiary period.