Format: ORAL

Harshita Bhatia1,2, Gaurav Srivastava1,2, R.C. Mehrotra1

1 Birbal Sahni Institute of Palaeosciences, 53 University Road, Lucknow 226 007, India 2 Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India

India plays a crucial role in understanding current biogeographical patterns in paleotropical flora, as its vegetation has likely experienced more changes than any other tropical region. This is attributed to the Indian plate traveling a distance of ~9000 km from the Southern to the Northern Hemisphere. Climatic changes have led to the extension of the majority of the lineages that contribute for its rich diversity of evergreen forests. However, very little evidence for this rich history comes from the examination of the present-day flora of the Indian subcontinent. Deciphering the story of the origin of the modern-day flora is important for the conservation of this highly biodiverse flora. In South Asia, the evergreen forests are confined to the Western Ghats and northeast India, influenced by the South Asian Monsoon (SAM) or Indian Summer Monsoon (ISM). The evolutionary history and relationship of these evergreen forests with SAM are still poorly known. Here, we present a detailed study on the late Oligocene megafossil record from Makum Coalfield, northeast India, using qualitative and quantitative techniques of paleoenvironmental reconstructions. Qualitative data indicate the presence of mostly megathermal plant families and the dominance of tropical wet evergreen taxa with modern-like floristics diversity. Quantification of climate by using the Coexistence Approach (CA) and CLAMP (Climate Leaf Analysis Multivariate Program) methodologies indicates a tropical warm, humid, and seasonal climate during the late Oligocene. Moreover, leaf physiognomic data obtained from CLAMP indicate the presence of a modern-like SAM during the late Oligocene. Our study suggests that the initiation of modern like evergreen forests and SAM have occurred synchronously during the late Oligocene in South Asia.