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M. Antonellini et al. / Marine and Petroleum Geology xxx (2013) 1e16 3

Figure 1. (a) Location of the study area; (b) photograph and relative detailed map of small- to medium-offset strike-slip CSB, ZB, and DF exposed in a 200 m long outcrop located
along the coast of Piana di Castelluzzo (San Vito Lo Capo). The images were digitally acquired by helicopter flying at an altitude of about 50 m above sea level; and (c) orientation
data.

and marl fragments with bioclasts (i.e. Vermetus, Serpula, lamelli- the ESE-striking set, left-lateral strike-slip kinematics for the N-
branches, echinoids, algae and corals) spanning in size from sub- striking set and oblique-slip normal kinematics for the NW-
millimeter to a centimetres. Erosional unconformities commonly trending one (Figs. 2a and 3a). The three aforementioned sets, all
separate adjacent carbonate beds. The maximum burial depth sub-vertical, show mutual crosscutting relationships which suggest
these rocks experienced is estimated up to 30 m (Abate et al.,1997). they developed, more or less, contemporaneously (Figs. 2a and 3a).
Thin-section observations are consistent with the presence of both Tondi (2007) documented three different tabular zones (zones I,
intergranular and intragranular porosities (Tondi et al., 2012). II and III) within the outcropping faults (Fig. 2b). Zone I represents
Generally, well-developed intergranular pores form a connected the inner part, which includes the slip surfaces and is characterized
network in 2D; both shapes and sizes of these pores change with by a well-developed, continuous zone of grain size and porosity
the grain size and sorting. Intergranular pores can reach a few mm reduction. Zone II, which bounds on both sides zone I, is a com-
in diameter in the very coarse-grained lithofacies. The overall host pacted grain zone with stylolites localized at the grain contacts;
rock porosity measured by both image analysis (2D) and laboratory generally, in terms of thickness it is one half of zone I. Zone III
measurements of representative cylindrical cores (3D) ranges be- represents a thicker volume, surrounding both zones I and II, in
tween 25% and 45% (Tondi et al., 2012). Even if in small amounts, which porosity reduction is due to precipitation of calcite cements.
microsparry cement is always present at the grain contacts and/or Aiming at gathering enough data to build up two different
within intragranular pores. In addition, syntaxial overgrowth models of the fracture network, one based on a deterministic fully
cement might be present around echinoid plates and spines. descriptive field map, the other one on a Discrete Fracture Network,
we investigated two different outcrops. One of these is located at
3. Methodology San Vito Lo Capo Peninsula, along the marine flat surface of the
Piana di Castelluzzo, the other one at Favignana Island within the
3.1. Structural setting inactive quarry of Cala San Nicola (see Fig. 1 for location). At San
Vito lo Capo Peninsula, we integrated the detailed map (at a 1:25
At San Vito Lo Capo peninsula and Favignana Island, the Early scale) first published by Tondi (2007) with new results of a detailed
Pleistocene carbonate grainstones are crosscut by several small structural and permeability (using a TinyPerm II Portable Air Per-
offset strike-slip shear structures that include: (i) single compactive meameter, Balsamo et al., 2010) survey of the outcropping struc-
shear bands (CSB), (ii) zones of compactive shear bands (ZB) and (iii) tural features (Figs. 3 and 4). At Favignana, we computed the
well-developed faults (DF), with slip surfaces and fault rocks. CSB dimensional parameters (i.e. length, thickness and displacement) of
and ZB are present within fault-bounded rock volumes. The evolving strike-slip structures cropping out at Cala San Nicola (Tondi et al.,
growth processes of these faults, as well as their dimensional pa- 2012) after scan line measurements and detailed structural map-
rameters, are documented in Tondi (2007) and Tondi et al. (2012). ping (at a 1:1 scale). The Favignana outcrop was chosen to develop
The aforementioned structures form a network made up of a the power law distributions that were also used in the models for
dominant set trending ESEeWSW and two subordinate sets San Vito Lo Capo for two reasons: (1) the structure sets orientations
trending roughly NWeSE and NeS(Fig. 2a and b). Markers repre- and their distributions are similar at San Vito Lo Capo and Favig-
sented by the geometry of the step-over zones and bedding/older nana, (2) the length of the outcrops in Favignana allowed for better
structures offsets indicate a right-lateral strike-slip character for data collection to construct the power law distributions.

Please cite this article in press as: Antonellini, M., et al., Fluid flow numerical experiments of faulted porous carbonates, Northwest Sicily (Italy),
Marine and Petroleum Geology (2013), http://dx.doi.org/10.1016/j.marpetgeo.2013.12.003