Imaging Mesozoic Sediments in Deccan Volcanic Province of India: Inferences from Seismic and Gravity Studies

Abstract

Imaging sub-basalt Mesozoic sediments in the Deccan Volcanic Province (DVP) of India is a major challenge for hydrocarbon exploration. However, long-offset coincident seismic reflection (CDP) and refraction/wide-angle seismic reflection techniques may be applied for imaging sub-trappean Mesozoic sediments with proven success. The CSIR-NGRI executed several such deep seismic profiles with maximum offsets less than 100 km along with other geophysical methods like magneto-telluric, deep-resistivitysounding and gravity surveys in the DVP covering Kutch, Saurashtra and Deccan Syneclise regions of India during the last three decades with an aim of integrated geophysical modeling. This has been sponsored and supported by the ONGC and OIDB. We used some of the selected deep seismic profile data in the DVP to image low-velocity-layer (LVL) like Mesozoic sediments, hidden below the high-velocity-layer (HVL) corresponding to basalts/traps. We applied ray-trace inversion of travel time data, robust tomographic inversion and advanced seismic imaging techniques to obtain seismic sections and velocity models. The derived velocity models delineate thick sub-basalt Mesozoic sediments in the south of Kutch, north-western part of Saurashtra and western segment of Deccan Syneclise along with extension of trap and basement configuration with details shown through fence diagrams. They are further constrained and corroborated by the corresponding density models obtained from inversion of residual Bouguer gravity anomaly data. The results provide an insight of the presence of hydrocarbon bearing sub-trappean Mesozoic sediments hidden in the DVP.