Early Cretaceous Flora from the East Coast Sedimentary Basins of India: Their Chronostratigraphic and Palaeobiogeographic Significance

Abstract

Macrofloristic or microfloristic zonation of Mesozoic successions, with or without independent marine–biostratigraphic age constraints, is extensively utilized in sedimentary basin analyses worldwide. However, precise macrofloral or palynological demarcation of the non-marine Mesozoic successions remains elusive in India. This uncertainty stems from several factors, including unfossiliferous deposits in critical stratigraphic intervals. However, marine fauna (ammonoids, foraminifers) have been well documented from the Mesozoic sequences of India and offer a unique correlation interface. We attempt to establish tie-points between these fauna and the macro and microflora from the East Coast sedimentary basins of India, which include the Cauvery and Palar basins of Tamilnadu, Krishna-Godavari and Pranhita-Godavari basins of Andhra Pradesh and Mahanadi Basin of Orissa. They offer considerable potential to achieve an integrated correlation to establish a higher time resolution. The early Cretaceous lithounits in these basins provide a long-ranging Neocomian-Aptian age. This work aims to provide precise ages to these formations based on biostratigraphically diagnostic taxa, especially palynomorphs and macroflora. These ages are supported by correlation with reports of coeval marine fossils such as ammonoids, foraminifers and dinoflagellates wherever available. Thus, based on the marker taxa precise ages have been assigned to the lithounits of the east coast sedimentary basins. Palaeobiogegraphic studies indicate that latitudinal control on climate was a more important factor in delineating the paleofloristic realms. The development of the angiosperms took place around the Neocomian and their diversification around Aptian-Turonian. Marine routes were established along the margins of the southern continents.