Browsing by Author "Sunil Bajpai"

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Biostratigraphy, palaeoenvironment and sea level changes during pre-collisional (Palaeocene) phase of the Indian plate: Palynological evidence from Akli Formation in Giral Lignite Mine, Barmer Basin, Rajasthan, Western India
(International Union of Geological Sciences, 2020) Vandana Prasad; Prem Raj Uddandam; Shailesh Agrawal; Sunil Bajpai; Indrabir Singh; Ashish K. Mishra; Anupam Sharma; Madhav Kumar; Poonam Verma
Giral Lignite Mine succession (Akli Formation) from Barmer Basin, Rajasthan yielded rich assemblage of dinoflagellate cysts and compared with the global dinoflagellate zonation schemes, and a Danian- Thanetian age is proposed. Within a precise biostratigraphic control, changes in the terrestrial and marine palynomorphs allowed the construction of relative sea level fluctuation curve and the development of depositonal succession in a sequence stratigraphic framework. Based on the lithological and palynological content, the Giral Lignite Mine succession is divided in to five units. Unit 1 (lower 7.8 m) is interpreted as transgressive deposit formed in an open bay setting during rise in the relative sea level representing the Transgressive Systems Tract (TST). The age is Danian on the basis of dinoflagellate cyst assemblages. Unit 2 (16.5 m) consists of 5-6 laterally occurring lignite bands. It is deposited during decrease of sea level and increased detritus supply in essentially salt marsh environment during Highstand Systems Tract (HST). Unit 3 (3.42 m) is shallow marine facies of Thanetian age deposited in a restricted setting represents a Transgressive Systems Tract. Unit 4 (0.9 m) is marked by a return to coastal marsh depositional conditions, possibly representing a Highstand Systems Tract. The erosional surface at the top of Unit 4 is interpreted as a Sequence Boundary. Unit 5 (9.3 m) is highly oxydized and is devoid of any organic matter content. Two major marine flooding surfaces identified in the Giral Lignite Mine succession can be correlated with the Maximum Flooding Surfaces (MFS) at 60.7 Ma and 57.9 Ma corresponding to the eustatic curve. Based on the dinoflagellate biostratigraphy Danian- Thanetian age has been assigned to the lignite bearing succession of Giral Mine. Western Indian margin consist of large-scale lignite deposits in Kutch, Cambay and Rajasthan Basin. The proposed Danian-Thanetian age of lignite bearing succession of Giral Mine is much older than the late Thanetian-early Ypresian age of lignite successions of Cambay and Kutch Basins of Gujarat. The present study suggests a significantly diachronous development of lignite deposits on the western peninsular margin of India. © 2020 International Union of Geological Sciences. All rights reserved.
Middle Eocene (Bartonian) vertebrate fauna from Bandah Formation, Jaisalmer Basin, Rajasthan, Western India
(Taylor and Francis Ltd., 2021) Krishna Kumar; Pragya Pandey; Sunil Bajpai; Debasish Bhattacharya; Bindhyachal Pandey
A small vertebrate faunal assemblage of late Middle Eocene (Bartonian) age is described from the Bandah Formation, a shallow marine deposit in the Jaisalmer Basin of Rajasthan state, Western India. The Bandah assemblage comprises representatives of selachians (sharks, rays), crocodilians, turtles and archaeocete cetaceans (archaic whales). The mammalian component of this fauna, though represented by fragmentary specimens, allows identification of two archaeocete taxa for the first time from the Palaeogene of Rajasthan: an unnamed protocetid close to Babiacetus and an andrewsiphiine remingtonocetid (Kutchicetus sp.). Occurrence of Eocene cetaceans in the Jaisalmer Basin brings to light a new, potentially rich cetacean-yielding horizon in India, and has the potential to allow a better understanding of early whale evolution in the Indian subcontinent. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Recent advances on phanerozoic biodiversity, bioevents and climate in India
(2012) Sunil Bajpai; G.V.R. Prasad; Vandana Prasad; J.A.I. Krishna; Anindya Sarkar
In the present write up, a synthesis of the research done in the last four years in vertebrate palaeontology, palynology, ammonoid biostratigraphy and stable isotope geochemistry is presented. SB and GVR discuss the issues relating to Cretaceous-Palaeogene (K-Pg) boundary bioevents in India and their linkage to Deccan volcanism, Jurassic and Cretaceous diversity of dinosaurs and elasmobranchsorigin and evolution of archaic mammals of Cretaceous - Early Eocene age during the northward flight of India, their biogeographic relationships, evolution of whales and Neogene mammals. In a related discussion, VP discusses on the time of origin of grass family Poaceae and rice tribe Oryzeae based on the analysis of late Cretaceous dinosaur coprolites and sediments bioevents at the K-Pg boundary in Um Sohryngkew River section in Meghalaya, NE India and the effects of environmental stress from Deccan volcanism on Palaeogene flora presently restricted to Western Ghats, the role of dinoflagellates in dating the highly diversified mammal-bearing levels within the Vastan lignite mine, and the presence of dipterocarp angiosperm trees in the Early Eocene of India and thus supporting the "out of India Dispersal" hypothesis for this group of plants. JK presents a comprehensive picture on the refined Triassic and Jurassic ammonoid biozonation in the Himalayan and western Indian regions, respectively, sequence stratigraphie framework of Mesozoic marine sequences of India, and the relationship between major tectonic events of the Indian ocean and sea level changes. AS discusses the relevance of isotopic studies across Permo-Triassic boundary and Eocene/Oligocene boundary in understanding the extinction of plants and the role of silicate weathering in the Himalaya, respectively, forced regressive event in the Palaeogene of the Himalayan foreland basin linked to the early phases of Himalayan uplift, development of palaeosols with the expansion of C4 vegetation in GangaBrahmaputra delta plain during the last glacial maximum (LGM), and different episodes of monsoon intensification that coincide with major pulses in the Himalayan uplift based on hydrogen isotopic studies of Quaternary Siwalik palaeosols. © Printed in India.