Geology Reference
In-Depth Information
(a)
Brunico/
Brunic
(b)
SS49
Italy
Mid-Triassic palaeogeography and
strike-slip tectonics of the Dolomites
Bressa
n
one/
Brixen
MERANO
SS49
SS244
Mediterranean Sea
Put
ia
Fanes
Tre Cime
Or
tisei
S
. Christina
Corvara
SS38
BOLZANO/
BOZ
E
N
Misurina
Ortisei
S
ella
Cortina d'Ampezzo
Cortina
d'Ampezzo
SS48
Mendola Pas
s
BOLZANO/
BOZEN
Sass
.
Arabba
Sciliar
Canazei
Cerne
ra
M
endol
a/
M
endel
P
ass
SS52
Pieve
diCadore
E45
Pelmo
C
atinaccio/
Ros
e
ngarten
SS42
Latemar
Moena
SS43
Egna
SS51
Predazzo
Latemar
SS48
Mar
molada
Civetta
San
Roen
Trodena
Lucan
o
BELLUN
O
Predazzo
TRENTO
Agnello
A27
SS51
San Martino
Agordo
North
0
10 km
SS47
SS50
Vittorio
Veneto
E45
FORESLOPE
PLATFORM
BASIN
VOLCANICS
(CALDERAS)
PLUTONIC
BODIES
STRIKE-SLIP FAULT
THRUST FAULT
NORMAL FAULT
N
EXPLANATION
SS47
Scale (km)
Major Road/Highway
Road
CITY /
Large Town
Town / Village
Carbonate Buildup
0
10
20
Ala
Fig. 2.
(a) Location of the study areas. Geographical locations of Mendola Pass and Latemar in the Dolomites, northern
Italy. (b) Palaeogeographical and palaeotectonic reconstruction of the Dolomites during the Ladinian, after Doglioni (1988)
& Bosellini (1991). Note the series of strike-slip faults adjacent to the Latemar buildup. Active sinistral transtension related
to the rifting of Pangaea has been recognized in the Dolomites, although quantifi cation of subsidence per locality within
the regime has not been established.
Bosellini & Hardie (1985), Doglioni (1987, 1988),
Jadoul
et al
. (1992), Carulli
et al
. (1998), Brack &
Muttoni (2000), and Cozzi (2000).
without a consistent, well-defi ned intertidal
facies. The absence of a clear intertidal facies was
taken as direct evidence of rapid exposure of the
platform top to the vadose zone: a 'Waltherian
skip' in the shallowing-upward facies succession
as a direct result of sea-level fall (Goldhammer
et al
., 1987, 1990). Palaeobathymetric relations
between the platform interior and reef margin
facies estimated the reef top to be 2-3 m deeper
than the platform interior (Goldhammer &
Harris, 1989). The absence of subaerial exposure
diagenesis in the margin therefore constrains the
high-frequency sea-level amplitudes to around
2-3 metres.
The above interpretation was modifi ed by
Egenhoff
et al
. (1999) who reinterpreted the
oncolitic-bioclastic grainstones beneath expo-
sure caps as possible intertidal deposits (Fig. 3,
Microfacies 4), although oncoids have been
previously associated with subtidal channels
(Demicco & Hardie, 1994). Preto
et al
. (2004)
went on to recognize peloidal packstones-to-
grainstones with weakly developed fenestral
cyanobacterial laminae in several cycles (see
Preto
et al
., 2004, lithofacies 2), interpreting their
presence as a record of supratidal conditions.
FACIES AND CYCLES
The metre-scale platform interior cycles at
Mendola Pass and Latemar share the general trend
of having a shallowing-upward facies succession
within each cycle. However, the facies inter-
nal to the cycles at the two localities are notably
different.
Latemar cycles
At Latemar, facies within cycles 'shallow-
upward' from a peloidal wackestone-packstone
through an oncolitic, lithoclastic grainstone that
is capped by a dolomitic caliche crust indicat-
ive of subaerial exposure (Goldhammer
et al
.,
1987; Egenhoff
et al
., 1999; Preto
et al
., 2001,
2004; Zühlke
et al
., 2003) (Fig. 3). This succes-
sion was originally interpreted by Goldhammer
et al
. (1987) as shallowing-up from shallow sub-
tidal through to the subaerial exposure cap, but
