Thermal regime, hydrocarbon maturation and geodynamic events along the western margin of India since late Cretaceous
The passive continental margin of western India and the adjacent offshore region are associated with a transitional type thinned crust. It contains several sedimentary basins where substantial recoverable oil/gas reserves exist. The northern Cambay graben, northern and eastern parts of the Bombay offshore and the Konkan coast region that are situated close to western margin exhibit reasonably high heat flow and geothermal gradients beneath which the asthenosphere is upwarped to a depth of 30-70 km. Temperatures at the depth of 3 km are estimated to be in the range of 105-260°C. Curie depth analysis from MAGSAT studies in an area between latitudes 11°N and 19°N and longitudes 65°E and 73°E also indicates a high geothermal gradient of about 30°C/km within the upper crustal column. We suggest that the occurrence of oil and gas in these areas may be due to catastrophic and geodynamic events which took place in the last 130 Ma. India's super-mobility, continental breakups, possible bolide impact and Deccan volcanic episode at the western margin resulted in substantial lithospheric heating, accompanied by subcrustal melting and rise of isotherms, to eventually enhance the hydrocarbon maturation process. The study indicates that all other sedimentary basins situated on the western margin are also thermally mature and may have high potential for the occurrence of hydrocarbons.