Saumitra Misra

Publications (28) View all

• Source

  Available from: Trina Bose

  Article: Meteoritic Impacts and Climatic Changes in Pliocene–Pleistocene Epoch

  Trina Bose, Ajoy K. Bhaumik, Saumitra Misra
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  ABSTRACT: During the Pliocene–Pleistocene epoch, covering last ∼5.2Ma of Earth’s history, altogether 34 terrestrial meteoritic impact craters are known. Most of these craters (29) have diameter ≤10km, among which 11 craters fall in 1,000 to 100m range, and 7 are still smaller in dimension and of recent age. The age versus impact-frequency plot shows that the meteoritic impacts during this time period occurred in discrete intervals but have a periodicity that shows the best possible coincidence with the ∼425Ky climatic cycles observed by Fourier analysis and FFT filtering of composite high resolution benthic foraminiferal δ18O record. This observation is also supported by Monte Carlo test with 71% success where meteoritic impact(s) shows coincidence with climatic cooling within our error limit. The newly observed climatic–meteoritic cycle may be same with the ∼400Ky Milankovitch cycle or it is a different newly understood cycle relating both the climatic variation and meteoritic impact events.
  Earth Moon and Planets 04/2012; 101(3):141-151. · 0.67 Impact Factor
• Source

  Available from: geosocindia.org

  Article: Sources of monazite sand in southern Orissa beach placer, eastern India

  N. Sulekha Rao, Saumitra Misra
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  ABSTRACT: This paper intends to explore whether there is an important source for monazite beach placer of the Gopalpur-Chhatrapur-Rushikulya coast, Orissa, in the adjacent Eastern Ghat Mobile Belt (EGMB). Petrographic and mineralogical studies were conducted on all the rock types constituting the EGMB exposed over a stretch extended up to ∼20 km landward from the estuary of the River Rushikulya that is believed to transport the major bulk of sand to the Gopalpur-Chhatrapur-Rushikulya beach. Heavy mineral population was concentrated using bromoform and percentages of each heavy mineral constituting the population were estimated for all the potential source rock types. Isodynamic separation and XRD techniques were deployed for precision identification of every heavy mineral present. The study identified the granitoid (or migmatite) basement rock as by far the major contributor of monazite to the Chhatrapur beach sand. The study also reveals that charnockite is an important contributor of orthopyroxene as well as garnet, although the sillimanite-garnet-quartz schist (khondalites) is also an important source for the latter. On the other hand, garnet-quartz schist and garnet-biotite-quartz schist may also contribute substantial quantity of pyroxene and garnet. The high grade metasedimentary rocks, in general, could be the major sources for rutile, while ilmenite, magnetite and zircon in the beach sand have their sources perhaps in all the varieties of rocks constituting the EGMB.
  Journal of the Geological Society of India 04/2012; 74(3):357-362. · 0.60 Impact Factor
• Article: Structural and anisotropy of magnetic susceptibility (AMS) evidence for oblique impact on terrestrial basalt flows: Lonar crater, India

  Saumitra Misra, Md. Arif, Nathani Basavaiah, P.K. Srivastava, Anand Dube
  Geological Society of America Bulletin 03/2010; · 3.79 Impact Factor
• Source

  Available from: Md. Arif ...

  Article: Structural and anisotropy of magnetic susceptibility (AMS) evidence for oblique impact on terrestrial basalt flows: Lonar crater, India

  Saumitra Misra, Md. Arif, Nathani Basavaiah, P.K. Srivastava, Anand Dube
  Geological Society of America Bulletin 03/2010; · 3.79 Impact Factor
• Article: Target rocks, impact glasses, and melt rocks from the Lonar impact crater, India: Petrography and geochemistry

  Shiloh Osae, Saumitra Misra, Christian Koeberl, Debashish Sengupta, Sambhunath Ghosh
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  ABSTRACT: Abstract— The Lonar crater, India, is the only well-preserved simple crater on Earth in continental flood basalts; it is excavated in the Deccan trap basalts of Cretaceous-Tertiary age. A representative set of target basalts, including the basalt flows excavated by the crater, and a variety of impact breccias and impact glasses, were analyzed for their major and trace element compositions. Impact glasses and breccias were found inside and outside the crater rim in a variety of morphological forms and shapes. Comparable geochemical patterns of immobile elements (e.g., REEs) for glass, melt rock and basalt indicates minimal fractionation between the target rocks and the impactites. We found only little indication of post-impact hydrothermal alteration in terms of volatile trace element changes. No clear indication of an extraterrestrial component was found in any of our breccias and impact glasses, indicating either a low level of contamination, or a non-chondritic or otherwise iridium-poor impactor.
  Meteoritics & Planetary Science. 01/2010; 40(9‐10):1473 - 1492.