Neogene palaeobiogeography of the Indian subcontinent with special reference to fossil vertebrates

Abstract

The geological history of the Indian subcontinent during the Neogene shows firstly, a progressive continentality in sedimentation; secondly, variable climatic trends ranging from warm, tropical rain-forest conditions throughout the Miocene up to the Early Pliocene, with a drier climate in the Pliocene, gradually changing to glacial conditions by the Middle Pleistocene; thirdly, a southerly and easterly shifting of climatic zones; and lastly, a remarkable stability in marine and non-marine sedimentary regimes, with the Himalayas representing the main source of sediments for north India from the Miocene onwards. This stability is also evidenced by marine and non-marine faunas. Thirty to forty percent of the species of the Miocene marine molluscs and elasmobranchs are common to Recent taxa in the Arabian Sea and Bay of Bengal. Pliocene Siwalik fishes are referable to present-day forms in the Indo-Gangetic Plain rivers with the exception of Heterobranchus which is presently restricted to Africa. In contrast to the Palaeogene, coal occurs less frequently in the Neogene. The Neogene also shows a widespread distribution of mammalian faunas, which constitute the main criteria for stratigraphic correlation of non-marine deposits. The occurrence of certain Miocene and Pleistocene plain-dwelling mammals in areas which today are highly elevated (Kashmir) testifies to Neogene impulses of the Himalayan orogeny. Early Neogene (Lower Miocene) mammals from the Indian subcontinent show an inter-mixture between southern Russian and African forms.