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Morphological and chemical properties of Microtektite grains from Bay of Bengal (IODP Expedition: 354)
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  • Masud Kawsar,
  • M C Manoj,
  • Kohki Yoshida,
  • Alan Baxter,
  • Brendan Reilly
Masud Kawsar
Birbal Sahni Institute of Palseosciences

Corresponding Author:masudbsip@yahoo.com

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M C Manoj
Birbal Sahni Institute of Palaeosciences
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Kohki Yoshida
Shinshu University
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Alan Baxter
University of New England Australia
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Brendan Reilly
Oregon State University
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This study reports the presence of Australasian microtektites in a deep-sea core (U1452) retrieved during International Ocean Discovery Program (IODP) Expedition 354: Bengal Fan. These microtektites are found within a foraminifera-rich calcareous clay layer beneath the Brunhes–Matuyama (B–M) magnetostratigraphic boundary. Most of them are spherical and are less than one millimeter in diameter. Typical splash (dumbbell, teardrop, button etc.) and irregular-shaped forms were recovered. The most abundant microtektites are pale green in color, followed by opaque, pale brown, translucent and transparent varieties. They are characterized by various surficial attributes including pits, mounds, grooves and fractures. Geochemical analyses suggest that the major oxide compositions are very similar to Australasian microtektites, Australasites reported elsewhere and also to the average composition of upper crustal rocks. Transparent bottle green microtektites are relatively richer in MgO content and lower in silica to other microtektites found in U1452. Minor and trace elements show a wide range of distribution and individual samples show variation. Differences in minor and trace elements concentration are possibly due to the contamination from the impact ejecta. Other than microtektites, presence of possibly polymetallic exsolution texture, shocked minerals and unmelted and partly melted ejecta within the microtektite-bearing layer in the northern Indian Ocean provides further evidence that the Australasites and Australasian microtektites might have been formed by the impact of an extraterrestrial projectile at ~0.8 Ma, somewhere in Indochina.