Extension Related Magmatism and Basin Evolution in Northwestern Part of the Cuddapah Rift, India

Spatial distribution and field relationship of igneous intrusives viz. basic dykes, pink granite-leucogranite-tourmaline pegmatites and quartz reefs across interface between the Neoarchean Gadwal schist belt (Basement) and the Proterozoic Cuddapah basin have been documented. The Cuddapah basin is a half graben (rift) developed at right angle to the basement and displays two sets of faults: (1) NE-SW longitudinal and (2) NW-SE transverse. The longitudinal faults oriented parallel to basin margin have controlled sedimentation, subsidence and uplift. The transverse faults extending from rift shoulder (basement) right into central part of the basin are post depositional faults and imparted en-echelon pattern to the basement-basin interface. Sedimentary facies, depositional environments and basin setting indicate that the basin fill was deposited in a rift setting over the northwestern part of the epeiric sea embayment that flooded on to the Dharwar batholith of the Eastern Dharwar craton. Basin evolution stages have been outlined. Basin uplift/inversion is controlled by reverse faults and is viewed as a cause and effect to the post Cuddapah extension related magmatism which is attributed to magma underplating in the environs of the northwestern part of the Cuddapah rift at crustal levels.