K-T magmatism and basin tectonism in western Rajasthan, India, results from extensional tectonics and not from Réunion plume activity

Abstract

Evolution of sedimentary basins took place in the Barmer, Jaisalmer and Bikaner regions during K-T (Cretaceous-Tertiary) time in western Rajasthan, India. These intra-cratonic rift basins developed under an extensional tectonic regime from early Jurassic to Tertiary time. Rift evolution resulted in alkaline magmatism at the rift margins. This magmatism is dated at 68.5 Ma and has been considered to be an early phase of Deccan volcanism. Deccan volcanism, sedimentary basin development and the alkaline magmatism of western Rajasthan have thus been considered to be the products of Reunion plume activity. However, sedimentary basin evolution began in western Rajasthan prior to Deccan volcanism and K-T alkaline magmatism. Gondwanaland fragmentation during the Mesozoic caused the development of the rift basins of Gujarat and western Rajasthan. This resulted in the opening of the Jurassic rift system and mildly alkaline magmatism at ca. 120 Ma in western India. This event is pre-K-T and plume activity has not hypothesized for it. Continental fragmentation under an extensional tectonic regime during K-T time resulted in the magmatism and basin tectonism in western Rajasthan. Crustal development during the K-T period in western Rajasthan results from an extensional tectonic regime and is not the manifestation of Reunion plume activity. Key wordsK-T magmatism, mantle plume, western Rajasthan, extensional tectonics, K-T basins