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Geologic periodicities and the GalaxyNew geologic and astronomical developments are reviewed that have recently led to the proposal of various Galactic theories to explain the temporal pattern of impact craters on earth. Linear and harmonic time series analyses have revealed that two dominant periodicities about equal to 33 + or - 3 Myr and 260 + or - 25 Myr underlie the geologic record of terrestrial impact cratering and global tectonic phenomena. It is argued that purely terrestrial mechanisms cannot account for the cratering cycles as being preservational artifacts; cratering rather appears to influence tectonism, possibly through perturbations of mantle convection. Galactic models proposed to explain the two long-term periodicities are reviewed critically. The most likely explanation for the 33 Myr cycle involves the comparatively stable half period of vertical oscillation of the solar system about the Galactic plane. The 260 Myr cycle may be related to rare encounters with Galactic spiral arms during the revolution of the solar system around the Galactic center.
Document ID
19870046841
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Rampino, Michael R.
(New York University NY, United States)
Stothers, Richard B.
(NASA Goddard Institute for Space Studies New York, NY, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1986
Subject Category
Astrophysics
Accession Number
87A34115
Funding Number(s)
CONTRACT_GRANT: NCC5-16
CONTRACT_GRANT: NASA TASK III
Distribution Limits
Public
Copyright
Other

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