Biotic perspective of the Deccan volcanism and India-Asia collision: recent advances

Abstract

India's physical and biotic links after its separation from the former assembly of southern continents (Gondwanaland) continue to evoke global interest. Of particular interest is the period from 65 to 45 million years before present, which spans the interval from the terminal phase of India's northward flight as an isolated landmass until its collision with Asia. The faunal response during this period has had profound influence on origins, evolution and the distribution of many of the modern life forms. Recent fossil data from the Deccan intertrappean deposits of peninsular India have revealed extensive endemism among the freshwater ostracods, suggesting India's significant physical isolation around the Cretaceous-Tertiary (K-T) boundary (65Ma), consistent with the geophysical data. The co-existence of Laurasian elements in the Deccan intertrappeans is now better explained in terms of transoceanic (sweepstakes) dispersal rather than the previously proposed direct terrestrial contact between India and Asia near the K-T boundary. Furthermore, the Deccan Traps volcanism has now been shown to be a major cause of the faunal extinctions, including that of dinosaurs, at the K-T boundary. New data from sections near Rajahmundry in the Krishna-Godavari Basin of southeastern India, and Jhilmili, in the Chhindwara district of central India, show that the end of the most massive phase of Deccan volcanism occurred at or near the K-T mass extinctions, demonstrating a cause and effect relationship. Data from Jhilmili also reveal a major marine seaway that existed across India during the K-T transition. This seaway, with major implications for the paleogeography, evolution and biotic diversity during the K-T transition, may possibly have followed the Narmada and Tapti rift zones. Following the Deccan eruptions, the most profound biotic events occurred around the time of India-Asia collision at ~55Ma, which include the sudden appearance of several new mammalian taxa in the Indian subcontinent, as well as the dispersal of ancient Gondwanan taxa to the northern continents (the Out-of-India hypothesis). Recent fossil finds from Gujarat and the Himalaya have established the Indian subcontinent as the centre of origin/early evolution of several major groups of modern mammals, both marine and terrestrial, such as whales, primates, lagomorphs and hoofed mammals including horses.