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394 Facies (2007) 53:389–400
rounded or subangular mud peloids and ostracods, heavily
impregnated with iron oxides.
The total organic matter content is very low and mostly
consisting of small particles of inertinite and fungal remains.
Lithofacies type 5
Along the Punta Bassano succession, 10 cm–1 m thick,
often discontinuous layers of intraformational breccias are
present showing Xat-lying clasts orientation.
MF8 The microfacies is a rudstone characterised by a low
percentage of carbonate matrix, often dolomitised, and
angular limestone clasts (2–20 cm). The texture of clasts is
quite homogeneous, represented by mudstone (MF1) and
laminated wackestone (MF4).
Lithofacies type 6
Clayey marl and marl intervals, which vary in thickness
from a few centimetres to several metres, are irregularly
distributed along the succession (Fig. 5).
MF9 The dark grey clayey marls and marls, yellow to
ochre on the weathering surface, are characterised by poor
and less diversiWed microfauna consisting of ostracods.
Sporadically, thin-shelled bivalves occur.
The total organic matter content is quite high and mostly
represented by vitrinite, amorphosed phytoclasts, fungal
hyphae, cutinite (leaf remains) and less abundant inertinite.
The percentage of sporomorphs varies from low within the
lowest clayey marls intervals to quite abundant upwards.
The maximum is reached around 30 m where the spo-
romorph assemblage is dominated by circumpolles fre-
quently in tetrad status.
Facies interpretation
In the following discussion, the microfacies characterising
the Punta Bassano succession are interpreted in terms of
palaeoenvironment. Their lateral distribution along a car-
bonate ramp is reconstructed, extending from a peritidal
setting to a shallow subtidal zone passing over a high-
energy shoal facies (Fig. 4).
The laminated fenestral wackestone (MF4) can be inter-
preted as algal or microbial mat deposits related to upper
intertidal to supratidal environment of a tidal Xat (peritidal
zone; Flügel 2004), swept by gentle tidal currents. Fenestral
fabric results from grain bridging and/or gas bubble forma-
tion associated with decomposition of organic material. In
addition, most peloids of this facies are thought to have
been formed by shrinking of originally cryptalgal and
123
Fig. 5 Stratigraphic section of the Upper Triassic Punta Bassano ᭤
carbonate succession showing sample locations, biostratigraphically
diagnostic organisms and depositional systems
muddy laminae owing to desiccation and/or salinity varia-
tions (Fischer 1964; Martini et al. 1989; Carillat et al.
1999).
Mudstone (MF1) and Wne-grained peloidal wackestone/
packstone (MF2) occur in lagoonal-peritidal environment.
The low biotic diversity of foraminifers and ostracods indi-
cates high-stressed habitat in very shallow restricted areas,
where great Xuctuations in salinity and temperature proba-
bly occurred. Under such conditions, short-term exposures
with evaporite precipitation may have taken place as testi-
Wed by corresponding mineral molds.
The bioclastic packstone (MF3) and the ostracod/peloi-
dal packstone to grainstone (MF5) are considered to have
originated as a storm deposit in the backshoal lagoon on the
carbonate ramp. The main textural criteria to validate our
interpretation is the presence of distinct diVerences in grain
sizes of these layers and of under- and overlying beds (i.e.
mudstones and wackestones) (Aigner 1985). These storm
layers are Xat-bedded, bioclast-dominated and coarse
grained. In MF3 redeposited, crinoids are present, which
are derived from open-marine environments. The relative
abundance of lithoclasts (MF3), comprising distinctly
microfacies, and rounded grains point to high-energy
events and erosion in a peritidal environment. The concen-
trations of mixed lagoonal and open inner-ramp marine
biota together with abundant peloids reinforce the proposed
depositional model.
The lumachelles microfacies (MF6) may originate from
short-term events (Kidwell 1991). Based on the packing of
skeletal elements, which is mud-supported, the deposition
takes place in an open-marine setting on a carbonate mid-
ramp. A low-energy environment below the wave base is
proposed. The presence of coated bioclasts with micrite
envelopes indicates that during the decline of storm inten-
sity, the material coming from very shallow environments
was transported by oVshore-directed bottom currents.
In the Wne- to coarse-grained non-laminated packstone/
grainstone (MF7), restricted diversity of bioclasts (only
ostracods) and dominance of micritic peloids indicate depo-
sition in the inner ramp, perhaps peritidal, settings with
poor connection with the middle ramp. The absence of lam-
inations, evaporitic signature and of subaerial exposure
may exclude deposition in evaporitic arid platform interi-
ors, where this facies would also occur.
In the Punta Bassano succession, peritidal intraforma-
tional breccias (MF8) are interpreted to have formed
by synsedimentary deposition of eroded carbonates proba-
bly related to storm events. However, the more thick and
discontinuous brecciated bodies may result from the