Geology Reference
In-Depth Information
The final tuning presented here, namely tuning the ARM-filtered precession
signal to the precession index in the mid-summer phase (i.e., ARM maxima to
precession index minima), was undertaken in an attempt to improve the
eccentricity spectrum, which appears to be accomplished (Figure 5.5f ). The
resulting sedimentation rates (Figure 5.5h, bottom series) show strong 405-
kyr variations, which amplify and include ~100-kyr cyclicity toward the top of
the series.
5.4.3
Objective Astronomical Tuning
Objective techniques have recently been developed to model the timescale
problem using statistics. The “average spectral misfit” method (Meyers &
Sageman 2007; Meyers 2008) identifies the sedimentation rate that best
transforms a stratigraphic spectrum to a model astronomical spectrum by
comprehensively testing a range of likely sedimentation rates on a strati-
graphic series and assessing the output spectra with respect to a model
astronomical spectrum. The sedimentation rate with the lowest number of
fits to Monte Carlo-generated randomized spectra is taken as the most
likely solution. A similar “Bayesian Monte Carlo” approach was developed
by Malinverno et al. (2010), which searches for the sedimentation rate that
maximizes a likelihood function defined by the ratio of data and equivalent
red noise spectrum weighted by astronomical frequencies. Both methods
provide statistics on the tested sedimentation rates and preserve the
original phasing of the data, a requirement for interpretation of insolation
forcing and for evaluating lags of astronomical-forced proxies with respect
to a model.
References
Berger, A., Loutre, M.F., & Tricot, C. (1993) Insolation and Earth's orbital periods.
Journal of Geophysical Research
,
98
, 10341-10362. DOI:10.1029/93jd00222.
Berger, A., Loutre, M.F., & Yin, Q.Z. (2010) Total irradiation during any time interval
of the year using elliptic integrals.
Quaternary Science Revieves
,
29
, 1968-1982.
DOI:10.1016/j.quascirev.2010.05.007.
Cande, S.C. & Kent, D.V. (1992) A new geomagnetic polarity time scale for the Late
Cretaceous and Cenozoic.
Journal of Geophysical Research
,
97
, 13917-13951.
DOI:10.1029/92jb01202.
Cande, S.C. & Kent, D.V. (1995) Revised calibration of the geomagnetic polarity
timescale of the Late Cretaceous and Cenozoic.
Journal of Geophysical Research
,
100
, 6093-6095. DOI:10.1029/94jb03098.
Gradstein, F.M., Ogg, J.G., & Smith, A. (2004)
A Geologic Time Scale
. Cambridge
University Press, New York.
Hilgen, F., Lourens, L.J., & Van Dam, J.A. (2012) Chapter 29: The Neogene period.
In: Gradstein, F.M., Ogg, J.G., Schmitz, M.D., & Ogg, G.M. (eds),
The Geologic
Time Scale 2012
, pp. 921-978. Elsevier, Amsterdam.
