Tectonics in the Cuddapah fold-thrust belt in the Indian shield, Andhra Pradesh, India and its implication on the crustal amalgamation of India and Rayner craton of Antarctica during Neoproterozoic orogenesis

摘要

Neoproterozoic orogenesis in East Antarctica and India led to the amalgamation of northern Prince Charles Mountains-Rayner complex of Antarctica with the Krishna Province of India along the present eastern coast of India with the development of ～990-900 Ma old fold-thrust belt. The frontal part of the fold-thrust belt [henceforth called the Cuddapah fold-thrust belt (CFTB)], recognized in the intercratonic, Palaeoproterozoic-Neo-proterozoic Cuddapah Basin, includes two frontal thrust sheets carried by the eastern Velikonda and the western Nallamalai thrusts, along with a part of the undeformed foreland, constituting frontal part of a larger fold-thrust belt now fragmented and separated in different continents of Gondwanaland. Therefore, the intercratonic deformation now preserved in the Palaeoproterozoic-Neoproterozoic Cuddapah Basin is related to the collision of the Indian shield to the Antarctic block during the amalgamation of the Rodinia Supercontinent. CFTB is dominated by quasi-plastic deformational structures, representing exhumed deeper level fault-propagation folding related to the Velikonda thrust, while the Nallamalai thrust represents the forelandward thrust of the CFTB dominated by elastico-frictional deformation structures.