• Sheela Kusumgar

      Articles written in Journal of Earth System Science

    • The Neogene/Quaternary boundary in India: A review

      D P Agrawal D K Bhatt Sheela Kusumgar R K Pant

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      The Neogene/Quaternary boundary has been variously defined in different continents. A global review of the problem shows that only the Olduvai event on the palaeomagnetic timescale may provide an universally acceptable isochronous datum for delineating this boundary. The N/Q boundary in the Siwaliks, Kashmir and the Andamans in India is defined in the light of recent research.

    • Geochemistry and magnetostratigraphy of deccan flows at Anjar, Kutch

      A D Shukla N Bhandari Sheela Kusumgar P N Shukla Z G Ghevariya K Gopalan V Balaram

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      Chemical analysis of nine Deccan flow basalts at Anjar, Kutch, western India, indicates that all, except the uppermost flow F-9, are alkaline. In their major and trace element composition, the alkali basalts resemble Ocean island basalts (OIB). Similarities of many diagnostic trace element ratios (e.g. Sm/Nd, Ba/Nb,Y/Nb and Zr/Nb) are similar to those found in the Réunion Island basalts. The uppermost basalt is tholeiitic and chemically resembles the least contaminated Deccan basalt (Ambenali type). The Anjar basalts have iridium concentration ranging between 2 and 178 pg/g. Some of these values are higher by about an order of magnitude compared to the Ir concentration in other basalts of the Deccan. A synthesis of chemical, palaeomagnetic and geochronologic data enables us to construct a chemical and magnetic stratigraphy for these flows.

      The three flows below the iridium enriched intertrappean bed (IT III) show normal magnetic polarity whereas all except one of the upper basalts show reversed magnetic polarity. The sequence seems to have started in polarity zones 31N and probably continued up to 28R or 27R. The results presented here support the view that Deccan volcanism in Kutch occurred on a time span of a few million years.

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