One of the global characteristic features of the Eocene is the extensive development of carbonate platforms in various regions of Tethys. Paleogene sequences of the Shillong Plateau from west to east are exposed in the steep Garo, Khasi and Jaintia hills. In the Khasi and Jaintia hills, Paleogene successions are represented by alternating carbonates and siliciclastics and provide datable micropaleontological fossils, whereas in the Garo Hills, which is in the south-western part of the Shillong Plateau, the Paleogene succession is mainly represented by siliciclastics and fewer carbonates. As the carbonates in this area are mostly marly, the recovery of carbonate microfossils is difficult. Accurate age assignment is important to correlate the sedimentary successions of the Khasi, Jaintia and Garo hills, which are mostly time transgressive and different lithologies were deposited at the same time. A detailed palynological investigation of 65 samples from the 25-m-thick sedimentary succession of the Siju Formation, Western Garo Hills, has yielded well-preserved and diverse organic-walled dinoflagellate cysts and calcareous nannofossils. Dinoflagellate cysts (Heteraulacacysta porosa, H. leptalea) and nannofossils (Discoaster barbadiensis, D. saipanensis, Reticulofenestra bisecta, R. erbae, and R. reticulata) indicate a middle Eocene age (Bartonian) for the studied section. The synthesis of nannofossils and dinocysts with records from India and Australia reveals a major late Bartonian transgression in the Indo-Pacific known as the ‘Kirthar transgression’.

The evolution and diversification of ancient megathermal angiosperm lineages with Africa-India origins in Asian tropical forests is poorly understood because of the lack of reliable fossils. Our palaeobiogeographical analysis of pollen fossils from Africa and India combined with molecular data and fossil amber records suggest a tropical-African origin of Dipterocarpaceae during the mid-Cretaceous and its dispersal to India during the Late Maastrichtian and Paleocene, leading to range expansion of aseasonal dipterocarps on the Indian Plate. The India-Asia collision further facilitated the dispersal of dipterocarps from India to similar climatic zones in Southeast Asia, which supports their out-of-India migration. The dispersal pathway suggested for Dipterocarpaceae may provide a framework for an alternative biogeographic hypothesis for several megathermal angiosperm families that are presently widely distributed in Southeast Asia.

Many plant families lack substantive fossil records, limiting our understanding of their origin and evolution. The abundance and preservation potential of pollen through geological time have helped to overcome such limitations and have provided reliable fossils for reconstructing biogeographical history and character evolution in many angiosperm families. Here, using scanning electron microscopy, we identified six Ebenaceae-type fossil pollen grains from early Palaeogene sediments of western India. Phenetic and phylogenetic analyses using pollen characters of fossil and extant taxa reavealed affinities of these fossils to three genera of Ebenaceae (Euclea, Royena and Diospyros). Furthermore, our divergence dating analysis using these fossils as priors suggested a Gondwanan origin for the family during the mid-Cretaceous [c. 107 Mya, 95% highest posterior density (HPD): 100–112 Mya] and supports the boreotropical and ‘out of India’ dispersal hypotheses as the most probable explanations for the present global distribution of the family. The study also supports the dispersal of the family into India, from Africa, through the Kohistan–Ladakh Arc during the Palaeocene. Finally, comparative phylogenetic analyses suggest significant synapomorphic and phylogenetic signals for a few selected pollen characters in Ebenaceae. Our findings have important implications for understanding the biogeography and evolution of the highly diverse and ecologically and economically important family Ebenaceae.

A combined biostratigraphic study of dinoflagellate cysts and foraminifera was carried out on Early Cretaceous subsurface well cutting sediments from well A（DNG）（2800–2746 m depth） from the Krishna-Godavari Basin, India.The last appearance datum of marker species of dinoflagellate cysts and planktonic foraminifera was considered for the construction of the biostratigraphic framework. The study shows dominance of Early Cretaceous marker dinoflagellate cysts Cassiculosphaeridia magna, Cribroperidinium perforans, Hystrichodinium voigtii, Kleithriasphaeridium eoinodes, and planktonic foraminifera Hedbergella aptiana, Hedbergella mitra, Hedbergella praelippa, Hedbergella tardita, Microhedbergella miniglobularis and Hedbergella mitra species. In addition to this, the dinoflagellate cyst data were compared with the dinoflagellate biozones of Austral and Tethyan provinces. Based on earlier micropalaeontological records from the Krishna-Godavari Basin and the present study, a latest Barremian-early Aptian age has been determined for the earliest marine transgression in the Krishna-Godavari Basin. The early marine incursion during late Barremian-earliest Aptian in the Krishna-Godavari Basin compared to Albian age in Cauvery Basin suggests the opening of east coast from north to south.