Tomographic imaging of large volcanic province due to intense magmatism in the Mahanadi delta of eastern India

We have derived a 2D tomographic P-wave velocity image of the shallow upper-crust (8.0 km depth) using first-arrival seismic refraction data along the 120 km E–W trending profile in the Mahanadi delta of eastern India. The tomographic image depicts smooth velocity variations of Quaternary (1.8–2.0 km/s) and Gondwana sediments (3.5–4.5 km/s) lying above the basement (5.9–6.1 km/s), which is highly distorted due to the presence of deep basinal faults. These faults reach maximum 6.0 km depth forming the Cuttack depression (Gondwana graben) in which thick (3.0 km) column of Gondwana sediments are deposited. The basement was uplifted forming Chandikhol ridge in the west and Bhubaneswar ridge in the east of the profile with anomalous high-velocity (5.5 km/s) dyke intrusions imaged on either side of the graben having high-velocity (6.5 km/s) magmatic intrusives lying below the basement.These dykes are volcanic in nature and fed by the large volcanic activity during Early Cretaceous period due to rifting of the Indian Plate from East Gondwana. This event is followed by the formation of an Early Cretaceous Volcanic Province (ECVP) in the rift zones of the Mahanadi and Lambert grabens, which were conjugate to each other before breakup of India and Antarctica. The signature of ECVP is imaged as magmatic intrusives below the basement and intruded to shallow depths through the conduits and deep basinal faults.

► Tomographic image in Mahanadi delta show new insights of shallow Gondwana tectonics. ► Basement configured show horsts and grabens having large-scale volcanic activity. ► High-velocity intrusive with dykes imaged are due to Early Cretaceous volcanism. ► Thick (3.0 km) Gondwana sediments imaged in the graben is potential for hydrocarbon. ► The breakup of India and Antarctica has led to formation of large volcanic province.