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 r egion are associated with a transitional type thinned crust. It contains se veral sedimentary basins where substantial recoverable oil/gas reserves exi st. The northern Cambay graben, northern and eastern parts of the Bombay of fshore and the Konkan coast region that are situated close to western margi n exhibit reasonably high heat flow and geothermal gradients beneath which the asthenosphere is upwarped to a depth of 30-70 km. Temperatures at the d epth of 3 km are estimated to be in the range of 105-260 degrees C. Curie d epth analysis from MAGSAT studies in an area between latitudes 11 degrees N and 19 degrees N and longitudes 65 degrees E and 73 degrees E also indicat es a high geothermal gradient of about 30 degrees C/km within the upper cru stal column. We suggest that the occurrence of oil and gas in these areas m ay be due to catastrophic and geodynamic events which took place in the las t 130 Ma. India's super-mobility, continental breakups, possible bolide imp act and Deccan volcanic episode at the western margin resulted in substanti al lithospheric heating, accompanied by subcrustal melting and rise of isot herms, 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. (C) 2000 Elsevier Science Ltd. All rights reserved.