Palaeobiogeographic significance of the Deccan infra- and intertrappean biota from peninsular India

Abstract

Extensive work done in the last decade on the sedimentary beds intercalated with the Deccan volcanic flows (infra- and intertrappean) has demonstrated the vast potential of these rocks for vertebrate, invertebrate and plant fossils. The infra- and intertrappean beds, especially those exposed on the eastern margin of the Deccan Traps, produced a large number of fossils which made it possible to establish the age and duration of Deccan volcanism (late Cretaceous-early Palaeocene) with some degree of confidence. Affinities of the late Cretaceous infratrappean vertebrates, such as pelomedusid turtles and sauropod dinosaurs, lie with those of Gondwanan landmasses. It seems more likely that these taxa are relicts of the Gondwanan stock that boarded the Indian plate well before its separation from Madagascar 70-80 Ma ago. Remnants of the former Gondwanaland fauna, such as pelomedusid turtles, leptodactylid frogs and titanosaurid dinosaurs did persist in relatively younger (latest Cretaceous) intertrappean beds. In addition to these Gondwanan elements, the intertrappean beds register many North American, European and Central Asiatic taxa (pelobatid and discoglossid frogs, anguid lizards, alligatorid crocodiles, palaeoryctid mammals, ostracodes and charophytes) suggesting that a contact between India and southern Asia was already established by the end of Cretaceous. An early India/Asia collision, long before the widely accepted early to middle Eocene date, is favoured to explain the presence of Laurasian elements in the late Cretaceous of India.