Sanidine spherules at the Cretaceous–Tertiary boundary indicate a large impact event

@article{Smit1981SanidineSA,
  title={Sanidine spherules at the Cretaceous–Tertiary boundary indicate a large impact event},
  author={Jan Smit and Gerard Th. Klaver},
  journal={Nature},
  year={1981},
  volume={292},
  pages={47-49}
}
The hypothesis that a catastrophic impact of an extraterrestrial body caused the terminal Cretaceous mass extinctions of dinosaurs, planktonic foraminfera and other species is now accepted as respectable following the discovery of a worldwide iridium enrichment in the Cretaceous–Tertiary (K–T) boundary clay1–5. In the basal lamina of the K–T boundary clay of Caravaca (Spain)7 numerous spherules were discovered composed of finely crystallized, almost pure K-feldspar in the structural state of… 
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Chemostratigraphy across the Cretaceous-Tertiary Boundary and a Critical Assessment of the Iridium Anomaly
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Geochemical evidence for an impact origin for a Late Archean spherule layer, Transvaal Supergroup, South Africa
A Late Archean layer rich in sand-sized spherules of former silicate melt in the Monteville Formation (Transvaal Supergroup, South Africa) has Ir concentrations as high as 6.4 ppb and is clearly
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TLDR
A hypothesis is suggested which accounts for the extinctions and the iridium observations, and the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other.
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Closely spaced samples from an uninterrupted calcareous pelagic sequence across the Cretaceous–Tertiary boundary reveal that the extinction of planktonic Foraminifera and nannofossils was abrupt
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TLDR
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TLDR
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