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Fig. 8.19 An example of tuning to long eccentricity for the Arguis Formation (Kodama et al. 2009, 2010). In the upper left
(Step 1) the power spectrum for the ARM cyclostratigraphy tied to magnetostratigraphy (GPTS 2004) shows the band-pass
fi ltering at 400 kyr in gray shading. The red line in the center fi gure is the fi ltered ARM time series plotted on top of the
unfi ltered ARM time series. The fi ltered ARM time series is then tuned to even 405 kyr intervals giving the tuned series in the
bottom of the center fi gure. The power spectrum for the 405 kyr tuned cyclostratigraphy is shown in the upper right (Step 2).
(See Colour Plate 25)
urements clearly identifi ed magnetite as the dominant
magnetic mineral and both studies identifi ed 1 m perio-
dicity in the MTM analysis of the data that was bundled
at 5 m (Fig. 8.20 ).
For the longer 100 m section at Cimon Latemar
these two peaks rise above the 99% confi dence level of
the robust red noise model. Depth rank analysis of the
lithologic facies for both sections also saw a 1 m perio-
dicity bundled at 5 m, again signifi cantly above the red
noise for the 100 m long Cimon Latemar section. The
ARM/SIRM ratio for the Forcellone samples showed
magnetic particle sizes consistent with eolian dust for
the source of the magnetite. A simple orbitally forced
interpretation of the rock magnetic data is that eolian
dust, forced by global aridity beating to precession
modulated by short-eccentricity Milankovitch cycles,
was deposited in the Latemar carbonate platform in the
Triassic. Most importantly for the cyclostratigraphic
interpretation, 1 m of carbonate was deposited over
about 20 kyr and 5 m in 100 kyr. This interpretation
forces the 600+ m thick Latemar sequence to be depos-
ited over 12 million years. It also suggests that sea level
(as recorded by facies depth rank) variations are
beating at the same periodicities as global aridity.
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