Accretion Rate of Extraterrestrial Matter: Iridium Deposited 33 to 67 Million Years Ago

@article{Kyte1986AccretionRO,
  title={Accretion Rate of Extraterrestrial Matter: Iridium Deposited 33 to 67 Million Years Ago},
  author={Frank T. Kyte and John T. Wasson},
  journal={Science},
  year={1986},
  volume={232},
  pages={1225 - 1229}
}
Iridium measured in 149 samples of a continuous 9-meter section of Pacific abyssal clay covering the time span 33 to 67 million years ago shows a well-defined peak only at the Cretaceous/Tertiary boundary. In the rest of the section iridium ranges from a minimum concentration near 0.35 nanograms per gram in the Paleocene to a maximum near 1.7 in the Eocene; between 63 and 33 million years ago the mean iridium accumulation rate is approximately 13 nanograms per square centimeter per million… 

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