Geology Reference
In-Depth Information
Analyses of cycle & megacycle
stacking showing frequencies
consistent with M
ilan
kovitch forcing
Milankovitchian forcing
not present in cycle &
m
egacycle stacking
Prec.
Ecc.
4.2 kyr
Prec.
1.7 kyr
???
Interpreted cycle periodicities
Fig. 1.
Comparison of proposed cyclic driver periodicities for individual cycles and megacycles at the Latemar section.
Both 'Pure Milankovitch' (Goldhammer
et al
., 1987; Preto
et al
., 2004) and 'Mixed Milankovitch and sub-Milankovitch'
(Zühlke, 2004) interpret Milankovitchian composite eustasy to have infl uenced the development of Latemar cycle stack-
ing. The millennial model does not recognize the infl uence of Milankovitchian forcing on the development of cycles or
megacycles at the Latemar.
Note
: Prec., precession; Ecc., eccentricity; ???, no periodicity defi ned.
bundling and a cross-correlative statistical fi t
of Latemar and Mendola sections supports the
conclusion that an interplatformal (hence
allocyclic) mechanism drove the development of
both cyclic successions. Comparative sedimento-
logical analysis considering rates of deposition
of equivalent facies in Holocene environments
suggests that these cycles accumulated over
multimillennial timescales.
preserved with short sections accessible in road
cut (Venzo & Fuganti, 1965; Prosser & Selli, 1991).
The absolute geometry of the Anisian-Ladinian
carbonate buildup at Mendola Pass is not known,
but appears to have involved a broad shelf that
allowed for the deposition of low-energy carbon-
ates (e.g. mud-prone lagoons and tidal fl ats).
Anisian-Ladinian buildups in the Dolomites
are common, most of which are limited to isolated
buildups tens of square kilometres in area. During
the Anisian-Ladinian times, active faulting
related to incipient rifting of Pangaea was ongo-
ing (Doglioni, 1987, 1988). Most of the Anisian-
Ladinian-age structures have been interpreted
in relation to a regional N70°E structural grain
that includes extensive left-lateral strike-
slip faulting (e.g. Stava Fault) and associated
fl ower structures, many of which are cut by late
Ladinian volcanic intrusions (Doglioni, 1988).
Such an active tectonic regime almost certainly
provided unique subsidence histories from local-
ity to locality. Differential subsidence affecting
active carbonate platforms in the Alpine Triassic
has been discussed in a number of studies span-
ning Middle and Late Triassic ages, including
LOCATION AND GEOLOGICAL SETTING
The Latemar Platform is an approximately 5 km
diameter carbonate platform of Anisian-Ladinian
age located in the Dolomites of northern Italy near
the town of Predazzo (Fig. 2). While the platform
is of comparative importance in this study, in
order to investigate the possibility of an allocyclic
driver for the Latemar cycles attention is focused
on the cyclic succession preserved at Mendola
Pass (located 30 km northwest from the Latemar
near Bolzano), where over 500 m of Anisian-
Ladinian-age cyclic platform interior strata of
the Dolomia della Val d'Adige Formation are
