Evaluating the success of astronomical tuning; pitfalls of using coherence as a criterion for assessing pre-Pleistocene timescales

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doi: 10.1029/95PA01454
Author(s): Shackleton, N. J.; Hagelberg, Teresa King; Crowhurst, S. J.
Author Affiliation(s): Primary:
University of Cambridge, Godwin Laboratory, Cambridge, United Kingdom
Other:
University of Rhode Island, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 10(4), p.693-697. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 17 refs.; illus.
Summary: The imprint of orbital variations on the geological record of climatic variability is well documented, especially for the Plio-Pleistocene. There is considerable interest in developing very high resolution timescales through the Cenozoic and into the Mesozoic by tuning geological records to the assumed astronomical forcing. Since the precession signal is so highly amplitude modulated, it is widely believed that high coherence between record and assumed forcing in the precession band is an indication that the timescale is probably correct, because coherence is supposed to provide a measure of the degree of common amplitude modulation. We show that this is misleading; even a sinusoidal variation that has been "tuned" to an insolation record shows highly significant coherence at the 23-kyr and 19-kyr precession frequencies. Coherence is a good indication that the tuning has generated a consistent phase relationship, but complex demodulation is a better tool for assessing the relationship between amplitude modulation in the data and in the hypothetical forcing. Copyright 1995 by the American Geophysical Union.
Year of Publication: 1995
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Astronomical forcing; Cenozoic; Coherence; Eccentricity; Methods; Obliquity of the ecliptic; Paleoclimatology; Precession; Time scales; Tuning methods
Record ID: 1997026641
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute.

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