Unveiling Crustal Dynamics and Thermal Structure in the Krishna-Godavari offshore Basin using Seismic, Magnetic, and Gravity Data

The Eastern Continental Margin of India (ECMI) is a passive, magma-poor margin that formed during India’s separation from Antarctica in the Early Cretaceous period. The margin extends for approximately 2000 kilometres from the Cauvery Basin in the south to the Mahanadi Basin in the north, encompassing multiple river-fed sedimentary basins, including the Bengal, Mahanadi, Krishna–Godavari, Palar, and Cauvery basins. Geophysical methods, such as seismic, gravity, and magnetic surveys, have been instrumental in analysing the ECMI's nature and evolution. While detailed multichannel seismic imaging, particularly along the ION1000 profile in the Krishna-Godavari offshore basin, has enhanced our understanding of ECMI’s crustal structure, significant gaps remain in comprehending its rift architecture in relation to the surrounding geology. Additionally, critical thermal characteristics, such as Curie point depths and heat flow patterns have not been investigated in the ECMI till date.

In this study, we utilized magnetic, gravity, and multichannel seismic data to investigate the rifting processes, subsurface structure, and thermal characteristics of the Krishna-Godavari offshore basin and surrounding areas. In addition to reinterpreting the ION1000 profile, we conducted a thorough analysis along the ION1200 and ION1240 profiles using both qualitative and quantitative methods. This allowed us to refine the structural framework of the region. Radially averaged spectral analysis of magnetic data was used to estimate Curie depths, from which heat flow values were derived, providing insight into the geothermal framework of the margin. Gravity data analysis enabled us to estimate Moho depths through non-linear inversion, giving a more precise configuration of the crust-mantle boundary.

Qualitative analysis of the ION1200 and ION1240 profiles helped us to identify structural domains associated with rifting processes, while quantitative analysis revealed the patterns of tectonic subsidence and depth anomalies. These findings indicate significant subsidence and outer margin collapse in the exhumed domain, with no evidence of crustal thickening during rifting. Variations in heat flow values are attributed to substantial sediment accumulation that acts as a thermal insulator over old oceanic crust. This study presents a comprehensive model for the evolution of the ECMI, illustrating how deep crustal processes, mapped through seismic, gravity, and magnetic methods, influence the overlying sedimentary structure and thermal characteristics of the passive margin, ultimately shaping its geological and geothermal framework.