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to generate both successions (see Schlager (1981)
for rates). If one considers low-energy carbonate
tidal fl ats as sediment sinks rather than sediment
sources (e.g. Ginsburg
et al
., 1977), source sedi-
ments would need to be produced at rates that are
even higher than 0.7 m kyr
1
in order to generate
enough sediment to fi ll the tidal-fl at sink.
However, the paucity of evidence for millennial
cyclicity of shallowing-upward carbonate suc-
cessions in the Holocene and Pleistocene must
be considered with the fact that biotic, climatic
and oceanic conditions have changed through-
out geological time. It is possible that the cyclic
drivers in the Triassic were unique to that period
and cannot be compared with those operating in
the Holocene and Pleistocene. Indeed, it may be
that in this case comparative sedimentology has
met its useful limit as a temporal reference, and
that its only appropriate use in Mid-Triassic
carbonates is as a tool for identifying facies and
depositional environments.
The conclusion that processes with millennial
periodicities formed the depositional cycles at
the Latemar section comes from palaeomagnetic
analysis, the dating of platform interior ash beds,
and the correlation of these dates to basinal
deposits proximal to the Latemar Platform.
The decision to rely on these techniques to a
greater degree than comparative sedimentology
and/or statistical analyses of the cyclic succession
is one that must be made in order to accept the
millennial model.
placement of the shorter Mendola Pass section
within the Latemar succession. Harmonic analysis
identifi ed the full suite of stacking pattern
frequencies in both sections, and spectral coher-
ency and cross-phase analysis confi rmed signifi c-
ant coherency and phase-locking between the
cyclic signals of both localities.
These results have the following implications
for high-frequency cyclostratigraphic forcing of
sedimentation on the Latemar Platform.
1
The current state of knowledge regarding
Holocene and Pleistocene composite eustasy,
the formation of shallowing-upward cycles,
and the rates at which these cycles and their
component facies form indicate that carbonate
allocycles in modern environments form as the
result of multimillennial processes (Tables 1
and 2). If the drivers and depositional rates that
have been identifi ed for these cycles can serve
as a comparative model, it is then likely that the
depositional cycles at Mendola Pass and in the
Latemar section, as well as their conspicuous
bundled stacking patterns, formed as the result
of composite eustatic forcing.
Resolving the issue of millennial forcing
2
versus composite Milankovitch forcing by
comparing the ancient to the modern record
is diffi cult because metre-scale carbonate allo-
cycles stacked with millennial periodicities
remain undiscovered in modern carbonate
sedimentary settings. In addition, a purely sub-
Milankovitch scale cyclic driver that would act
to form bundled carbonate megacycles remains
undiscovered in modern settings.
At the present time, eustatic oscillations involv-
CONCLUSIONS
3
This work has undertaken a new examination
of the issue of allocyclicity in the origin of the
Latemar Platform cycles of the Middle Triassic of
the Dolomites, northern Italy. This involved the
measurement and analysis of a coeval cyclic plat-
form carbonate formation external to the Latemar
locality, 30 km to the northwest at Mendola Pass.
The objective was to determine if the Mendola
Pass succession contained a stratigraphic sig-
nal comparable to the one found in the Latemar
succession. Both successions have metre-scale
cyclic bedding with a shallowing-upward deposi-
tional theme, with each cycle exhibiting subtidal
(<10 m water depth) to supratidal successions of
subfacies. Biostratigraphic ties were established
between the two successions and statistical corre-
lation analysis of measured cycle thickness series
from the two localities allowed for stratigraphic
ing Milankovitch cycle driven composite
eustasy are still the most likely explanation
for the record of cyclic stratigraphy observed
at Mendola Pass and in the Latemar sec-
tion either in the form of pure Milankovitch
forcing (Goldhammer
et al
., 1987) or mixed
Milankovitch and sub-Milankovitch forcing
(Zühlke
et al
., 2003).
If one accepts the conclusion that Latemar and
4
Mendola allocycles and allocycle bundles were
formed at millennial periodicities, one must
also accept one of the following conclusions:
(a) That the controls on the sedimentary sys-
tem, including amplitudes and periodicities
of composite eustatic drivers and sustained,
very high (
0.7 m kyr
1
) sedimentation rates
in areas of rapid subsidence are unique to
Mid-Triassic carbonate systems.
