Geology Reference
In-Depth Information
(a)
30
400
4
3
2
1
0
0.02
99%
95%
90%
AR(1)
25
94
20
26.7
19.1
17.4
21.7
15
10
0.03
0.04
Cycles/kyr
0.05
5
26.7
21.7 19.1 17.4
0
0
0.01
0.02
0.03
Cycles/kyr
0.04
0.05
0.06
(b)
30
99%
95%
90%
400
4
3
2
1
0
0.02
AR(1)
25
19
24
22
20
95
128
15
10
0.03
0.04
Cycles/kyr
0.05
5
19
24 22
0
0
0.01
0.02
0.03
Cycles/kyr
0.04
0.05
0.06
Figure 4.22
Robust red noise modeling of astronomically tuned Arguis ARM time series compared with 2π
multitapered spectra. (a) The twice eccentricity-tuned series with estimated ρ = 0.9070 and (b) twice eccentricity then
precession index-tuned series with estimated ρ = 0.9190 (Figure 5.5 in Chapter 5). All peaks exceeding the 99% CL are
labeled in periodicity (kyr). The insets zoom in on the obliquity and precession index bands. In (a), despite tuning to
the eccentricity two times, the 128 kyr component of the orbital eccentricity is not resolved; but subsequent precession
index tuning resolves the 128 kyr component. The average Δt of both series is 3 kyr, or an average f
nyq
= 0.1667 cycles/
kyr. The spectra were computed using the SSA-MTM toolkit, with robust red noise parameters set for a 0.033 cycles/
kyr median filter, linear fitting and 6 dof for all frequencies.
blurs their appearance in an averaged power spectrum. Therefore, in the
stratigraphic domain, assuming an arbitrarily strict CL is ill advised.
Instead, reporting multiple CLs, as has become customary, provides
information about the relative statistical significance of spectral peaks.
Later, for example upon astronomical tuning, high CLs can be demanded
of the data (Figure 4.22). Accumulation rate effects can be preliminarily
assessed using time-frequency techniques (Section 4.3.7).
4.3.6.2 Harmonic F-Test
Thomson (1982) developed a multitaper test for harmonic (spectral) lines,
i.e., power that is consistently confined to single frequency bins in a time
series, as for example, the two sinusoids in the test time series in Figure 4.17.
The K eigencoefficients (the Fourier coefficients of each of the K eigentapered
