Elevated Concentrations of Cosmic Dust
in Wisconsin Stage Polar Ice

  Paul A. LaViolette

Meteoritics (1983) 18: 337 - 338

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Main Paper:
Evidence of High Cosmic Dust Concentrations

in Late Pleistocene Polar Ice

 Paul A. LaViolette

Meteoritics (1985) 20: 545 - 558


The cosmic dust concentration in the solar system during the last ice age was investigated by means of eight samples from taken from a depth of 1215-1279 m in the Camp Century ice core (77°10'N, 61°08'W).  Dust filtered from these samples was analyzed for the presence of the cosmic dust indicators iridium and nickel using the neutron activation analysis technique.  This study was carried out to test the hypothesis that the climatic change toward the end of the Last Ice Age was triggered by an incursion of nebular material into the Solar System. The analytical results are consistent with this hypothesis.  Concentrations of Ir and Ni in the ice were one to two orders of magnitude higher during the latter portion of the Last Ice Age (19,700 - 14,200 years BP)* as compared with current levels. Ir and Ni levels in 6 out of 8 samples suggest a total cosmic dust influx rate of about 0.5 - 3 X 10^7 tons/yr to the Earth's surface as compared with about 1 - 7 X 10^5 tons/yr for the current influx.  Elemental concentrations in 6 of the 8 dust samples range from 6 - 96 ppb for Ir and <60 to 3200 ppm for Ni.  It is concluded that a major fraction of this invading dust would have been of submicron size in which case the concentration of light scattering particles would have been sufficient to significantly alter the light transmission properties of the Solar System and substantially affect the Earth's climate.  These results mark the first time that cosmic dust deposition rates have been estimated for prehistoric times using the polar ice record.

* correction: The ice core depth sampled in this study actually spanned the period 38,650 to 78,500 years BP.  Since the time this paper was published, a new chronology was established for the Camp Century ice core that pushed back the above quoted date range to a much earlier time.

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