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Major episodes of geologic change - Correlations, time structure and possible causesPublished data sets of major geologic events of the past about 250 Myr (extinction events, sea-level lows, continental flood-basalt eruptions, mountain-building events, abrupt changes in sea-floor spreading, ocean-anoxic and blackshale events and the largest evaporite deposits) have been synthesized (with estimated errors). These events show evidence for a statistically significant periodic component with an underlying periodicity, formally equal to 26.6 Myr, and a recent maximum, close to the present time. The cycle may not be strictly periodic, but a periodicity of about 30 Myr is robust to probable errors in dating of the geologic events. The intervals of geologic change seem to involve jumps in sea-floor spreading associated with episodic continental rifting, volcanism, enhanced orogeny, global sea-level changes and fluctuations in climate. The period may represent a purely internal earth-pulsation, but evidence of planetesimal impacts at several extinction boundaries, and a possible underlying cycle of 28-36 Myr in crater ages, suggests that highly energetic impacts may be affecting global tectonics. A cyclic increase in the flux of planetesimals might result from the passage of the Solar System through the central plane of the Milky Way Galaxy - an event with a periodicity and mean phasing similar to that detected in the geologic changes.
Document ID
19930071454
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Rampino, Michael R.
(New York Univ.; NASA, Goddard Inst. for Space Studies, NY, United States)
Caldeira, Ken
(Pennsylvania State Univ. University Park, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 114
Issue: 3-Feb
ISSN: 0012-821X
Subject Category
Geosciences (General)
Accession Number
93A55451
Funding Number(s)
CONTRACT_GRANT: NGT-5070
CONTRACT_GRANT: NAGW-1697
Distribution Limits
Public
Copyright
Other

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