A short duration of the Cretaceous-Tertiary boundary event: evidence from extraterrestrial helium-3.
Analyses of marine carbonates through the interval 63.9 to 65.4 million years ago indicate a near-constant flux of extraterrestrial helium-3, a tracer of the accretion rate of interplanetary dust to Earth. This observation indicates that the bolide associated with the Cretaceous-Tertiary (K-T) extinction event was not accompanied by enhanced solar system dustiness and so could not have been a member of a comet shower. The use of helium-3 as a constant-flux proxy of sedimentation rate implies deposition of the K-T boundary clay in (10 +/- 2) x 10(3) years, precluding the possibility of a long hiatus at the boundary and requiring extremely rapid faunal turnover.
Mukhopadhyay
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Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. sujoy@gps.caltech.edu
Farley
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Montanari
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