• PRIYANKA SHANDILYA

      Articles written in Journal of Earth System Science

    • Rajgad GPB: A megaporphyritic flow field, Western Deccan Volcanic Province, India

      PRIYANKA SHANDILYA POUSHALI CHATTERJEE KONDEPUDI PATTABHIRAM MAKARAND BODAS KANCHAN PANDE VIVEK S KALE

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      We describe the distribution and characters of a megaporphyritic basalt flow field that was arguably the earliest described ‘giant phenocryst basalt’ (GPB) from the Deccan Volcanic Province (DVP). It is a marker horizon exposed in a > 30,000 $km^{2}$ area below the Mahabaleshwar Formation in the western DVP. Its presence, distribution and stratigraphic importance as a regional marker horizon are enumerated. Available geochronological and paleomagnetic data suggest that the stratigraphic position of the Rajgad GPB coincides with polarity reversal in Chron 29 recorded from the basaltic lava sequence of the Western DVP.

    • Geometry and age of a mafic dyke emplaced along the Bhetkheda–Mohana Lineament, Central Narmada valley, Deccan Volcanic Province

      SHILPA PATIL PILLAI KONDEPUDI PATTABHIRAM GAURI DOLE xDOLE PRIYANKA SHANDILYA DEVDUTT UPASANI KANCHAN PANDE VIVEK S KALE

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      The Bhetkheda–Mohana Lineament is traced as a continuous lineament across nearly 100 km in the central Narmada valley across the Deccan Trap basalts and their basement of Proterozoic sediments. While a major length of this lineament is occupied by a basaltic dyke, there are segments where the dyke is completely absent, and the lineament is represented by a regional fracture/shear/fault zone. At its eastern extremity, this dyke is exposed intruding along the axis of a synclinorium of the Vindhyan Supergroup sediments, as a 4-km long string of hillocks of picturesque columnar jointed basalt. It has the presence of ignimbrites and a thin basaltic flow (resting on the sediments) surrounding it, suggesting the presence of an eruptive vent. This dyke intrudes the Mandleshwar Formation lava flows dated at 67–66 Ma and is associated with the Narmada dyke swarm. It has given $^{40}$Ar/$^{39}$Ar age of 66.6±0.5 Ma. Its chemical characters conform to those of the basaltic flows of the Malwa Traps, indicating a common source and emplacement history. This is a unique example of a dyke that was emplaced along a preexisting fracture zone cutting through the Proterozoic basement as well as the Deccan Trap lavas, with a distinct petrological identity with the host lava flows, indicating its feeder relation. It endorses the comparison of the Icelandic mode of fissure-fed flood basalts with the eruptive history of the Deccan Volcanic Province.

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