Thrust fault reflections on wide-angle seismics: Modeling by a new approach and implications to Neoproterozoic collision

Abstract. Collisional events contemporaneous to the global Grenvillian (~1.1 Ga) and the East African (~550 Ma) orogens created a major fold and thrust belt system in the south Indian shield. The Cuddapah basin Eastern Boundary Thrust (CEBT), a significant part of this system, is believed to have evolved by fragmentation and amalgamation of continental blocks in this region. The Cuddapah basin in the eastern Dharwar craton of south India has a long Paleo-Neoproterozoic geological history. Deep seismic near-vertical reflection profiling is the most successful geophysical technique utilized to delineate such complex crustal structures of the orogens. Here we utilize observations on a refraction /wide-angle reflection profile for the first time, to delineate the structure of the CEBT. We developed a novel modeling approach for this purpose utilizing the 'localized phantom horizons' consistent with the limited-extent discrete reflector segments of the continental crust in the region. A detailed velocity model and geometry of the structure inferred here, by synthetic seismograms modeling of unequivocal seismic reflections, provide clues on the evolution of the CEBT. Another thrust, the Eastern Ghats Thrust (EGT), related to the Eastern Ghats orogen, contemporaneous with the Columbia supercontinent is also identified. Integrating these modeling results, inferred velocity structure, observed steep gradient bipolar gravity anomaly and other geological data, we interpret the CEBT as a collisional suture juxtaposing the Cuddapah basin and the Eastern Ghats mobile belt.