Page 87 - Carbonate Sedimentology and Sequence Stratigraphy

78 WOLFGANG SCHLAGER

A) B)
Fig. 5.8.— Analysis of bedding rhythms in search
of orbital cycles - a case study from the Triassic of
the Southern Alps. A) Measured section with litho-
facies ranked according to presumed water depth
(maximum depth on the right). B) Spectrogram of
apparent frequency (cycles/m) throughout the sec-
tion. The spectrogram was constructed from 121
overlapping line spectra such as the one shown in
C. Lateral shifts of peaks are attributed to changes
in sedimentation rate. These sedimentation-rate
changes were compensated for by assuming that
the spectral peak at 1.6 cycles/m represents the
short precession cycle with an estimated Triassic
period of 17.8 ky. D) Power-spectral analysis of the
time series after tuning to the short precession cy-
cle, P2. Shown is 1.5 π multitaper spectrum with
arrows indicating peaks that passed the F test for
significance at the 95% level or better. E1 – E3 =
eccentricity cycles, P1 – P2 = precession cycles.
Peaks in between may represent obliquity cycles.
After Preto and Hinnov (2003), modified.

C)

D)