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Geological Society, London, Special Publications; 1998; v. 140; p. 19-29;
DOI: 10.1144/GSL.SP.1998.140.01.04
© 1998 Geological Society of London

The Flux of Extraterrestrial Material to the Earth: Determination by Astronomical and Statistical Techniques

Galactic periodicity and the geological record

W. M. Napier

Armagh Observatory, College Hill, Armagh BT61 9DG, UK

Precisely dated impact craters, major geological disturbances and mass extinction peaks were used to investigate statistically the hypothesis that global terrestrial phenomena are triggered by the Galactic environment through bombardment episodes. Strong temporal correlations were found between events in these datasets, and in aggregate they were found to have a periodicity of c. 27 ± 1 Ma corresponding to the half-period of the Sun’s vertical oscillations within the Galactic disc. Global disturbances appear to be forced in quasi-periodic fashion through a combination of impacts and prolonged climatic stress, the latter as a result of stratospheric dusting by debris from very large short-period comets.





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S. Kelley
The geochronology of large igneous provinces, terrestrial impact craters, and their relationship to mass extinctions on Earth
Journal of the Geological Society, 2007; 164: 923 - 936.
[Abstract] [Full Text] [PDF]