Mathematics – Logic
Scientific paper
May 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981e%26psl..53..279m&link_type=abstract
Earth and Planetary Science Letters, Volume 53, Issue 3, p. 279-295.
Mathematics
Logic
23
Scientific paper
Variations in the ratio of 18O/16O as measured in shells of marine calcareous microfossils are primarily dominated by changes in global ice volume; hence these variations provide a set of global time lines in deep-sea sediments. It is likely that the timing of major changes in oxygen isotope values is strongly influenced, if not controlled, by variations in the geometry of the Earth's orbit. Since the variation of orbital parameters can be accurately calculated, the opportunity exists for transforming this orbital chronology into a geological chronology.
Through careful correlation of oxygen isotope records in a set of deep-sea cores from the sub-Antarctic, South Atlantic and equatorial Pacific, we have assembled a composite isotopic section spanning the last 750,000 years with an average sedimentation rate of 2.3 cm/1000 years. A new chronology for this time period was developed by adjusting the ages of the oxygen isotope stage boundaries in this composite section so as to extend the consistent phase relationships that exist between variations in oxygen isotope ratios and changes in obliquity and precession during the last 300,000 years to the entire 750,000-year record. Previously identified difficulties in phase locking precession with the filtered isotopic signal between 365,000 and 465,000 years B.P. have been resolved with the recognition that precessional variations have an average period of 19,000 years and not 23,000 years during this interval. Since this new age model yields the best match between variations in obliquity and precession and their corresponding frequency components in the oxygen isotope record, we believe that it presents the most accurate chronology yet developed for deep-sea sediments.
With this new age model providing the time control, power spectral analyses of South Atlantic and sub-Antarctic chemical and biotic indices show that there is a strong tendency for variance to be concentrated at frequencies corresponding to periods of ~ 100,000, 41,000 and 23,000 years.
Also Department of Geological Sciences, Columbia University in the City of New York, NY 10027, U.S.A.
Hays James D.
Morley Joseph J.
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