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Lower Pleistocene deposits in east part of the Favignana ...
base of some conglomerates, displaying broad but gen-
eral shallow (several tens of cm) channels. Crude planar
cross-bedding is visible in topmost part of the section. In
the western sector the conglomerates can reach 3 me-
ters thick. There are lenses, up to 1.5 meters thick,
composed by calcarenites rich in mollusc shells that
display in their lower part crude lamination, that be-
comes more chaotic upwards (Fig. 5b). The upper part
of the sequence consists of thick-bedded conglome-
rates, displaying erosive base with planar westward
cross-bedding, locally underlined by lag of single, ellip-
soidal pebbles. Decreasing of size of clastics is visible
(Fig. 5c) landwards. In some localities, homogenous
medium-grained calcarenites, up to several tens cm
thick, enriched in pelitic material, show a medium bed-
ding. The sequence generally stops with coarsening-up
strata, homogenous in their lower part, showing low-
angled lamination near the top, covered by laminated
bioturbated calcirudites (Fig. 5d) with eastward dipping
and muddy drapes. Somewhere channelized conglome-
ratic beds with pebbles, rhodolihts and shell fragments,
in which the size of clastics and thickness of layers is
decreasing eastward, can be observed. Conglomerates
show a cover of oblique cross-bedded layers, generally
dipping toward ESE, pervasively bioturbated and topped
or by a bundled part (Fig. 5e) and by horizontal lami-
nated or wave laminated calcarenites. Calcirudites with
rhodoliths crop out eastward, almost up to Lido Burone
Locally. Broad and deeply incised erosional channels,
NW-SE and N-S directed, filled up by stack of oblique
and locally sinuosinoidal cross laminated material with
very coarse grained material concentrated in the middle
part of inclined layer (Fig. 5f), can be observed. Thin,
pelitic horizons separate individual laminated set. The
calcirudites in Punta Lunga are locally cut by Scolithos-
type traces (Fig. 5d) and on the upper surface there is
characteristic network of Thalassinoides (Fig. 5g) and
sporadic Ophiomorpha (Fig. 5h). This can represent
Cruziana and Skolithos ichnofacies (BROMLEY, 1996;
SEILACHER, 1967) or Thalassinoides Skolitus Suite of
D’ALESSANDRO et al. (1993).
Facies association B, mainly deposited by storm
waves of high magnitudes, could represent a portion of
the upper shoreface zone (ELLIOt, 1986; CLIFTON,
2006). Size of detrital material and seeward inclination
of cross-bedding show that coarse detrital material, to-
gether with rhodoliths and Serpulids, was probably de-
rived from shoreline, by back currents generated by ex-
ceptionally strong storms. Bodies of sediments rich in
fragments of bivalve shells chaotically distributed
represent storm deposits. Single coarse-grained body
was probably formed during a very short time amount
(about few hours?). Erosive channels, perpendicular or
oblique to the shoreline, probably created by local rip
currents can also be seen. Visible in exposures bodies
and structures probably not represent all events which
took place in this area as due to the strong erosion
processes, which are suggested by preserved sedimen-
tary structures, erosional surfaces specially, part of se-
diments was reworked by subsequent storms. Gravel
containing dunes, generated by strong storm current
migrated generally seawards, but sporadic occurrence
2 Sediments similar to Facies Association C are also exposed in area of Punta Marsala.
157
of landward inclined cross-bedding implies occasionally
shore-ward movements of dunes. Longshore currents
played less important role than currents more and less
perpendicular to the shoreline. Sediments of fair weath-
er, represented by medium scale cross bedding, are
preserved only locally. The lack of trace fossils in the
lower part of sequence could be en efect of conditions
existing during that period (strong current and wave ac-
tions), which was probably unfavorable for development
and/or preservation of epi- and infauna (D’ALESSANDRO
& BROMLEY 1996). Only at the end of the development
of Facies Association B sequence, locally, in sheltered
area, were formed favourable, calm habitats that al-
lowed to develop and preserve extensive nets of Tha-
lassoinoides and Skolithos. The coexistence of Skoli-
thos and Thalassoinoides indicates moderate turbu-
lence D’ALESSANDRO, LOIACONO & BROMLEY (1993).
MCILROY (2004) sugessts that it can be an effect of par-
tially isolation of that area by bars.
3.3 Facies Association C, coarser fraction
This Facies Association, that stretches eastward
(seaward) from the previous one Facies in the area of
Lido Burrone up to Punta Fanfalo2 (Fig. 1c), is dominat-
ed by coarse and medium-grained calcarenites, whose
thickness not exceed 20 meters. Generally the coarser
fraction consists in shell fragments and the sediments
typically present traces of Echinoidea. Direct relation to
the Facies Association B is partly obliterated by faults
(ABATE et al., 1995). The visible part of the sequence
starts with a layer of calcirudite with rhodolithes and
shell fragments, similar to those of Facies Association
B, covered by thin calcarenite strata with trough cross
laminations or ripple cross-lamination. Inclination of
cross-bedding structures is generally southwestwards
and less common towards S-SSE (Punta Burrone,
western outcrop) and WSW (Punta Fanfalo, eastern
outcrop). The main part of Facies Association C is cha-
racterized by occurrence of thick beds (up to two m) of
thick-bedded calcarenites, often sub-horizontal lami-
nated, mostly well-sorted, coarse to medium-grained
with channels filled up by cross-bedded calcarenites
(Fig. 6a). There are also thick (up to 1 m) tabular cross-
stratified calcarenites, covered by ripple cross-laminat-
ed ones. Locally, shallow (up to tens of centimeters
deep) channels broad occur, filled-up by cross-
laminated calcarenites (Fig. 6a). Several beds contain
numerous dispersed shells of pectinids and Echinoidea
(see the upper part of Fig. 6b) and, less commonly, of
Brachiopods, Dentalium and Cardium. Molluscs in life
position or forming layers of convex-up oriented bivalve
shells (Fig. 6c), together with fragments of Echinoidea
and – more rarely – rhodoliths, heve been observed in
some oucrops (Lido Burrone, Punta Fanfalo). These
organic remains may form lags above erosional lower
surfaces (Fig. 6d). In Punta Burrone area planar bifur-
cated structure, similar to mangrove tye roots (Fig. 10h)
have been discovered.
This generally low-energy Facies Association, lo-
cally with mollusc shells in life position, was developed in
relatively deep, quiet environment within shoreface zone.
Longshore currents from NNE dominate, favouring