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Facies (2007) 53:389–400 391
Malatesta 1964; Giunta and Liguori 1973; Abate et al. Facies description
1996, 1999), only one detailed investigation on sedimento-
logical aspects has been attempted (Abate et al. 1982). In The reference section of the Upper Triassic of Punta Bas-
the current paper, a sedimentological and biostratigraphic sano Unit shows a 124-m-thick stratigraphic succession of
approach is used to understand the relationship between carbonate rocks limestone (often dolomitised) with interca-
palaeoenvironmental parameters and change of sedimen- lations of marls, clayey marls and brecciated levels. The
tary facies. limestone, which is characteristically poor in microfauna, is
both micritic with pseudomorph of evaporites and lami-
Materials and methods nated with fenestrae. Six main lithologies and nine microfa-
cies have been recognised. The most frequently occurring
Microfacies and foraminifers analysis was performed litho- and microfacies types are described and illustrated in
through the polarised light on 60 thin sections sampled in Figs. 3 and 4.
the limestones.
Lithofacies type 1
Palynological processing was employed on 20 samples
mostly of clayey marls and marls. Out of these samples, Gray homogeneous limestone medium to thickly bedded
Wve were provided palynological assemblage. Organic mat- (30 cm up to 1 m), showing stratiWcation cycles as
ter was extracted applying standard palynological tech- described by Schwarzacher (2000) (Fig. 3a). Abundant
niques (Monteil 1985). Samples were crushed to a fraction gypsum pseudomorphs identiWed by characteristic lath-like
comprised of between 200 m and 2 mm, and attacked crystal shape are present within the limestone and are evi-
using diluted hydrochloric (HCl 32%) and hydroXuoric (HF dent on the weathering surface (Fig. 3b), which on the Weld
71–75%) acids to destroy, respectively, carbonate and sili- sometimes displays yellow patina. Frequently, the evapo-
cate components. The organic residue was sieved at 11 m ritic minerals have been completely leached to form distinct
in order to remove Wner particles. To prevent organic matter moldic porosity.
degradation, the residue was not oxidised with nitric acid
(HNO3), a process generally used to remove amorphous Three microfacies have been recognised:
organic matter and mounted on slides using polyvinyl alco-
hol and Eukitt glue. The palynological slides were exam- MF 1 The most abundant microfacies is mudstone with
ined under transmitted light. very rare bioclasts, exclusively composed of ostracod shells
and foraminifers. Rounded quartz grains might be abundant
Concerning the ostracods, 15 samples of limestone were and concentrated in thin levels. Organic facies mostly con-
processed using the seldom method of acetolysis (Cras- tain amorphous organic matter, which percentage ranges
quin-Soleau et al. 2005). After the processing, four of them between 40 and 60% of the total content. Subordinate
produced ostracods, which have been observed with a scan- amount of small equidimensional inertinite is also present
ning electronic microscope. associated with rare sporomorphs and vitrinite.
The acetolysis allows us to isolate ostracods, and/or oth- MF 2 Fine-grained peloidal wackestone/packstone, is
ers microorganisms (e.g. foraminifera, brachiopod larvae, found alternating with the above described facies. Miliolid
conodonts) varying from small (0.2 mm) to large (2–3 mm) type of foraminifers (i.e., Hoyenella inconstans) and incer-
size, from highly lithiWed rocks. The four steps of this tech- tae sedis of parathuramminacean type usually occur, while
nique are brieXy presented as follows: (1) Crushing: in ostracod shells are rare. Cloudy calcite pseudospar replace-
order to increase the reaction surface, 400–500 g of rock is ments of evaporite nodules (up to 5 mm) and/or gypsum
reduced to pieces of several cm3. (2) Dehydration: to avoid crystals, has been observed. This fabric became progres-
a later acid attack, the crushed sample must be dried, but sively more common towards the top of the section.
the temperature should not exceed 100°C. (3) Acetolysis:
when the sample has cooled down, it is completely covered MF 3 Bioclastic packstone is subordinately present in this
with pure acetic acid. No eVervescence must occur; it is lithofacies. Coarse bioclastic grains consist of bivalve
either a result of impure acid or incomplete drying. (4) Set- shells and ostracods. Various types of lithoclasts are abun-
tling and washing: when suYcient muddy deposit is pres- dant, including mudstone with rounded quartz grains and
ent, even before the complete disaggregation of the sample, Wnely laminated wackestone (probably of microbial/algal
the acid is Wltered oV and the sample is then washed. For origin). In places, packstone exclusively composed of cri-
ostracods, three sieves are used: the 2-mm mesh retains noidal fragments and minor Wne-grained mud peloids also
non-disaggregated sediment, the 0.5-mm mesh retains occur. This microfacies shows evident stylobedding-type
adults and large forms, and the 0.1-mm sieve retains small diagenetic structures (sensu Logan and Semeniuk 1976).
specimens and larvae.
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