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ago with Hardie
et al
. (1986) and has subsequently
stimulated a vigorous debate regarding the driv-
ing mechanisms and depositional environments
required to generate the succession. Goldhammer
et al
. (1987) proposed that the cyclic succession of
over 500 depositional cycles (<1 m average thick-
ness) on the Latemar Platform (the Dolomites,
northern Italy) is a sedimentary record of compos-
ite glacio-eustasy, driven by Milankovitch orbital
forcing. This interpretation was based on several
lines of evidence, including (a) the shallowing-
upward facies succession within each cycle
(thicker subtidal unit overlain abruptly by a
thin centimetre-scale, subaerial cap); (b) a pre-
valent 5:1 bundling of the 'fundamental' metre-
scale cycles into lower-frequency 'megacycles';
(c) time-series analysis of the cyclic succession
showing agreement with predicted Triassic astro-
nomical frequencies (Goldhammer
et al
., 1987,
1990; Goldhammer & Harris, 1989; Hinnov &
Goldhammer, 1991; Hinnov
et al
., 1997; Preto
et al
., 2001, 2004).
The Goldhammer
et al
. (1987) interpretation that
the high-frequency cyclicity at Latemar is attribut-
able to Milankovitch forcing was challenged by the
dating of zircons extracted from time-equivalent
basinal deposits and ash-fall tuffs preserved in
the Latemar Platform interior, as well as relative
dating provided by biostratigraphy (Brack
et al
.,
1996; Mundil
et al
., 1996, 2003; Zühlke, 2004).
These authors suggested that the entire Latemar
succession was deposited in between 2-4 Myr
(in contrast to the 9-12 Myr indicated by the
Milankovitch forcing interpretation), which
demands much shorter periodicities for composite
cyclic drivers (approximately 4.2 kyr per cycle),
i.e. the fundamental shallowing-upward cycles
are taken out of the Milankovitch frequency bands
(Zühlke
et al
., 2003). As a result, the driving mech-
anism for the Latemar cycles was reinterpreted to
be a periodic sub-Milankovitch process and the
driver for the megacycle bundling as operating on
Milankovitch timescales (Zühlke, 2004).
Most recently, Kent
et al
. (2004) argued that
most, if not all, of the 540-m-thick Latemar cyclic
succession is restricted to a single magnetochron.
Since magnetic reversals occur on average every
0.5 Myr, they suggested that the entire succes-
sion represents no more than about 0.8 Myr and
that individual Latemar cycles represent 1.7 kyr
durations. Independently, Emmerich
et al
. (2005)
attempted to correlate the U-Pb dates from tuffs
in the basinal Buchenstein beds (Mundil
et al
.,
1996) to dates in the Latemar Platform interior
(Mundil
et al
., 2003) using the biostratigraphic
markers of Brack & Rieber (1993). These results
suggested that individual Latemar cycles repre-
sent 0.9-1.97 kyr (Emmerich
et al
., 2005). Both
works effectively place both the Latemar cycles
and megacycles into the sub-Milankovitch band.
In particular, the 'millennial model' of Emmerich
et al
. (2005) is set apart from the previous models
in that no link to Milankovitch forcing of Latemar
cycles or megacycles is implied. Since publication
of this research, Hinnov (2006) has questioned
the interpretation of the palaeomagnetic data in
Kent
et al
. (2004) as a primary magnetic polarity
signal. Here it is further shown that the correla-
tion of Emmerich
et al
. (2005) results in a Latemar
chronostratigraphy with two age reversals (see
Fig. 7b in Emmerich
et al
., 2005), raising further
questions. These questions, and other issues
raised by these millennial models, will be explored
further in the discussion section.
While arguments surrounding the origin and
drivers of cyclic sedimentation at Latemar con-
tinue within the pure Milankovitch, sub-Milanko-
vitch, and millennial models, the conclusion that
the Latemar cycles are a sedimentological record
of an extrabasinal forcing mechanism was never
questioned (for a summary of the three sets of
Latemar cycle period interpretations, see Fig. 1).
However, Blendinger (2004) challenged the valid-
ity of recognizing shallowing-upward cycles at
Latemar altogether, proposing that cycle-capping
facies (dolomitic caliches, pisoids, tepees, etc.) are
the products of post-burial hydrothermal diagen-
esis rather than the products of early diagenesis in
the vadose zone. Blendinger (2004) stated (p. 21)
that 'an alternative interpretation to eustatically
controlled cyclicity and repeated subaerial expo-
sure is provided by diagenesis in a hydrothermal
fi eld.' However, the interpretations of Blendinger
(2004) are clearly open to debate (Blendinger,
2005a,b; Preto
et al
., 2005; Peterhänsel &
Egenhoff, 2005).
If the deposits at Latemar (as well as other
time-equivalent platforms with similar platform-
interior facies successions) cannot be confi dently
determined to be allogenic through sedimento-
logical and cyclostratigraphic analysis internal
to the platform, the only hope for the validation
of an allogenic driver is to identify temporally
equivalent deposits elsewhere that are cyclostrati-
graphically analogous. In this case, a succession
of upper Anisian to lower Ladinian cyclic plat-
form interior stratigraphy located approximately
30 km northwest of Latemar at Mendola Pass was
measured and analysed for possible periodic
signals. Identifi cation of comparable stacking,
