The template shows just where the given age models have optimum coherency with the selected orbital model and where in the record discrepancies arise.A new method of dating the long glacial-interglacial ice core records has emerged during the last 10 years.It is based on properties measured on the air extracted from the ice that are used as proxies of local summer insolation.
To obtain a template that closely mimics a given δ18O record, we propose the following steps: (1) generate a preliminary template based on a simple ice mass model, (2) find the Fourier matrix for this model, (3) find the Fourier matrix for the δ18O record to be tuned (if necessary, adjust preliminary sedimentation rate so that maxima appear at the correct spectral lines), (4) import the spectral power distribution from the matrix of the record into the matrix of the template (while preserving phase of template), and (5) generate the new template from the gain‐adjusted template matrix.
The record should now show optimum coherency with the template over the appropriate interval.
The efficiency of this method (“Fourier matrix conjugation”) in producing hybrid templates is illustrated using four examples: (1) testing the stacked record of Prell et al.
(1986) for constant sedimentation rate, (2) testing the date of 790 ka of the Brunhes/Matuyama boundary in Ontong Java Plateau Ocean Drilling Program Hole 805C (Berger et al., 1993a), (3) testing the age scale for a core from the Norwegian Sea containing meltwater events (Jansen, 1989), and (4) checking the age model of Ocean Drilling Program Site 677 (Shackleton et al., 1990) for internal consistency.
It's an almost absolute dating, providing we better understand the link between the influence of the local summer insolation on the snow grains at the surface and the measured properties in the ice, namely the content and the δO2/N2 ratio of the air enclosed in the ice.
Changes in these two properties have already shown convincing correlations with orbitally forced local summer insolation on several Antarctic and Greenland long ice core records.
Moreover, both δO2/N2 and air content have recently been measured for the first time on the same ice core (Vostok).
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Orbital tuning has become an important means of dating deep‐sea sediments of Pliocene‐Pleistocene age.
One approach is to generate a template simulating ice mass history based on Milankovitch forcing for comparison with a given δ18O record.