Geology Reference
In-Depth Information
(a)
C18n.2n
C18n.1n
C17n.3n
C17n.2n
C17n.1n
10
C18r
C18n.1r
C17r
C17n.2r
C17n.1r
C16r
8
6
4
2
0
100
200
300
400
Meters upsection
500
600
700
800
(b)
150
356.5 kyr
231.7 kyr
GTS2004 paleomag reversal scale:
1000 m/4.35 myr=230 m/myr
53 m
133.5 kyr
100
30.7 m
24.3 kyr
5.58 m
22.8 kyr
50
(
63.5 kyr
)
5.25 m
(14.6 m)
20.6 kyr
4.73m
0
0
0.05
0.1 0.15
Cycles/meter
0.2
0.25
Figure 6.4
Figure from Kodama et al. (2010) showing the ARM data series for the Arguis Formation (a) and its tie
to the magnetostratigraphy measured for this rock magnetic cyclostratigraphic study. The MTM power spectrum
(b) for the untuned ARM data series tied to time via the magnetostratigraphy with the robust red noise (red)
confidence limits of 90% green, 95% blue, and 99% purple shows significant peaks in the precessional band (~5 m)
and short (30.7 m) and long (82 m) eccentricities. Source: Kodama, Anastasio, Newton, Pares & L. A. Hinnov 2010.
Reproduced with permission of John Wiley & Sons, Inc.
stretch the time series into 405 kyr intervals (tuning 1). Then the minima
observed at roughly 100 kyr intervals for the 405 kyr tuned ARM series were
matched to 100 kyr minima in the theoretical eccentricity (Laskar et al. 2004)
for the Eocene. Finally, the twice-tuned series was filtered (Gaussian band pass)
at the 100 kyr scale and the filtered time series was tuned to theoretical eccen-
tricity. The multiple tuning procedure was checked with the MTM power
spectra of the series at each tuning step. Basically, the tuning enhanced the 400,
122, and 94 kyr peaks (eccentricity) as expected, but also enhanced preces-
sional peaks at 21.7, 19.1, and 17.4 kyr which matches the theoretical peaks at
this time period (23.2, 20.4, and 18.8 kyr) quite well. An additional preces-
sional-scale peak at 26.7 kyr also emerges in the power spectrum that doesn't fit
with the theoretical Eocene precessional spectrum suggesting that too much
tuning may not be justified. The precessional peaks after two tunings (to long
and short eccentricities) resolve into two precessional peaks at 23 and 18.2 kyr
