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E. Tondi et al. / Journal of Structural Geology 37 (2012) 53e64 57

Fig. 5. (a) Plots of the poles and (b) contoured stereonet plots (Schmidt distribution method), lower hemisphere projection, of orientations for compactive shear bands with left
(blue)-and right (red)-lateral sense of slip (data with unknown kinematics are in black). The mean great circles are also illustrated. The photos show (c) the displaced sedimentary
markers, as well as (d) the mutually crosscutting relationships of the two conjugate sets of compactive shear bands.
In Fig. 11, the cumulative frequency distributions of the three 4. Discussion
aforementioned dimensional parameters are best fitted by negative
power-law (Mandelbrot, 1983): At Cala San Nicola, the two sets of compactive shear bands at
N ðSÞ ¼ aS D (1) high-angle to bedding are similar to those documented by Tondi
(2007) in carbonate grainstones cropping out at San Vito Lo Capo
where N is the number of features having a size greater than or Peninsula (NW Sicily). These two sets include both single bands and
equal to S (e.g. the fault length), a is a measurement of the sample zones of bands. Strike-slip faults are present, as well, and consist of
size, and the power-law exponent D represents the slope of the best zones of compactive shear bands, discrete slip surfaces and cata-
fit line, which some authors interpreted also as the fractal dimen- clastic fault rocks, and hence represent a more evolved deformation
sion (Childs et al., 1990; Scholz and Cowie, 1990). The analysis state in the carbonate grainstones. The steep compactive shear
shows that for single bands, zones of bands and faults, the presence bands are coeval and form a pair of conjugate sets striking N-S (left
of data breaks in the thickness and displacement distribution lateral) and NW-SE (right-lateral), respectively. The acute angle
between: (i) single bands and zones of bands, and (ii) faults (Fig.11a defined by the two conjugate sets is about 45 and is likely
and b). controlled by the specific deformation mechanism responsible for

Fig. 6. Different types of interaction and linkage of single compactive shear bands, photograph (a) and map (b). Numbers refer to sites discussed in the text.