Rodinia to India: Signatures of Time and Space on Sediments of East Coast Basins of India and Its Significance on Hydrocarbon Potential

By

Kaushalendra.B Trivedi¹, Sushma Rawat²

(1) Suptdg.Geologist,Oil & Natural Gas Corporation Ltd.,India, Dehradun-248195, India (2) Dy.S.G.,Oil & Natural Gas Corporation Ltd.,India, Dehradun-248195, India

 The structural grain of India is a result of welding of Early and Middle Proterozoic mobile belts, which were wrapped around Archaean nuclei of Karnataka, Jeypore-Bastar and Singhbhum. This anisotropic basement could not withstand the stresses and split along paleosutures during initial rifting from Gondwanaland, the same way as the contiguous Zambezian type basement. These incipient sutures started receiving sediments from nearby elevated provenance through numerous minor fluviodeltaic systems, overlying the glaciomarine/glacio-fluvial prerift (Permo-Carboniferous) sediments. The subsequent block movement along these paleosutures has given rise to different subbasins separated by ridges, accommodating up to 8000m of sediments in some areas. During the final phase of rifting a volcanic episode - the Deccan Trap capped rift sediments. By an estimate, 62% of the world's total hydrocarbon occurrences fall between Pennsylvanian-Turonian age, hence these sediments attain great significance from exploration point of view. Nine rifted Basins considered along the east coast of India are, viz., Cauvery, Palar, Pennar, Pranhita-Godavari, Krishna- Godavari, Mahanadi, Bengal, Surma valley (Bangladesh) & Assam. These basins have recorded the signatures of various tectonic episodes that the Indian plate has undergone on its journey from near South pole to the present day position. These are indicated and very well decipherable on the basis of sedimentation patterns copied on seismic investigations and drilled wells records. In the paper, authors have correlated these signatures with distinct stages of rift evolution and basin building mechanism. The sediments accumulated during these phases attain significance as fossil fuel deposits, as worldwide analogues are available where due to increase in geothermal gradient during rifting; source rock is adequately matured to generate commercial hydrocarbons. A comparative analysis of contemporaneous petroleum systems of NW Australia, E. Africa, & Madagascar was considered to understand the structural settings and identify the future thrust areas for hydrocarbon exploration in the East Coast basins of India.