Biodiversity during the Deccan volcanic eruptive episode

Abstract

This paper gives a detailed overview of biotic assemblages recovered from the Deccan trap intercalated sedimentary sequences (infra- and intertrappean beds) of peninsular India as a result of extensive research done during the last 20 years. The infra- and intertrappean beds contain remnants of Gondwanan forms such as myobatrachinae frogs, pelomedusid turtles, dinosaurs (i.e. titanosaurids and abelisaurids), and mammals. Apart from these Gondwanan elements, the infra- and intertrappean beds also contain forms of Laurasian affinity though recently doubt has been cast on such relationships. Based on previous fossil records, Laurasiatic forms were considered to be represented by a great variety of micro- and megavertebrate assemblages such as discoglossid and pelobatid frogs, anguid lizards, alligatorid crocodiles, palaeoryctid mammals, charophytes and ostracodes. The biotic assemblages show a remarkable similarity between the infra- and intertrappean beds indicating a short time period for the deposition of these Deccan volcano-sedimentary beds. The recovered biotic assemblages strongly indicate a Maastrichtian age for the initiation of Deccan volcanic activity and the sedimentary beds associated with it. The Cretaceous/Tertiary boundary as such remains to be defined in any known sections in sedimentary sequences in so far investigated localities of peninsular India. What have been identified are Maastrichtian age beds in the east-central and western Narmada river region on the basis of pollens, vertebrate assemblage and planktonic foraminiferas in infratrappean offshore sequences. A Palaeocene intertrappean bed at Lalitpur (Uttar Pradesh) that is among those lacking dinosaurian remains but having palynological assemblages similar to those from well established Palaeocene sequences, suggests the presence of Palaeocene intertrappeans, but the K/T boundary is yet to be properly defined.