The origin and evolution of the Proterozoic Cuddapah basin located in the eastern Dharwar craton and its relationship with adjoining geotectonic terrains towards east, remained a subject of considerable debate for several decades. In the present study, an attempt has been made to decipher the deep crustal seismic structure and tectonics of the northern part of the Cuddapah basin and adjoining terrains, like Nellore Schist Belt, Eastern Ghats Belt and Nizampatnam Bay, by reprocessing the Deep Seismic Sounding data acquired along the Alampur-Koniki-Ganapeswaram profile. During Paleo-Mesoproterozoic period, this zone underwent prolonged sedimen-tation, magmatism, oceanic subduction, multiple accretion and continent-continent collision. Our modelling results, based on the first arrival refraction and wide angle reflection travel times data, reveals presence of 1.9 km thick sediments below the Nallamalai Fold Belt and 2.8 km in the Kurnool basin on its western side. In com-parison, a much thicker Gondwana and Proterozoic succession is recorded in coastal basins, located east of the Eastern Ghats Belt, indicating wide-spread Proterozoic sedimentation during Columbia and Rodinia super-continental assembly periods, than hitherto known. A 50 km wide hidden ridge structure known as Darsi-Addanki high which is bounded by two major faults, is mapped below the Nellore Schist-Eastern Ghats Belt region, that separates the Proterozoic basins on either sides. This feature, which parallels the east coast, may corresponds to collisional structure, formed by the India-east Antarctica collision, after the cessation of Meso-proterozoic supra-subduction. Related up-dipping of upper crustal layers can clearly be seen east of the hidden ridge structure below the bay of Nizampatnam. Further, for the first time, we introduced floating reflectors to match the strong reflection phases, which are restricted to upper and mid-crustal level below the Nallamalai basin and Nellore Schist Belt. Presence of unprecedently thick (up to 20 km) high velocity (Vp: 7.0-7.4 km/s) differentiated magma layer above the Moho, would indicate crust-mantle thermal perturbation and massive subcrustal erosion. An unusual 5-10 km thick metasomatized LVZ, characterized by Vp: 7.0 km/s, is also mapped in the upper part of the lithospheric mantle. This study supports presence of a totally different allocthonous geological terrain, east of the Cuddapah basin.
