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Journal of Structural Geology 37 (2012) 53e64

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Journal of Structural Geology

journal homepage: www.elsevier.com/locate/jsg

Growth processes, dimensional parameters and scaling relationships of two
conjugate sets of compactive shear bands in porous carbonate grainstones,

Favignana Island, Italy
a
a
d
b
c
E. Tondi a, * , A. Cilona , F. Agosta , A. Aydin , A. Rustichelli , P. Renda , G. Giunta d
a Geology Division, School of Science and Technology, University of Camerino, 62032, Camerino, MC, Italy
b
Department of Geological Sciences, University of Basilicata, Potenza, Italy
c
Department of Geological and Environmental Sciences, Stanford University, Stanford, USA
d
Dipartimento di Scienze della Terra e del Mare, Università di Palermo, Palermo, Italy
art i cle i nfo abstract
Article history: Three main sets of deformation bands are identified in the Lower Pleistocene carbonate grainstones of
Received 2 November 2011 Favignana Island (Italy). A bedding-parallel set is interpreted to contain compaction bands, based on the
Received in revised form lack of evidence for shear. The other two sets are oriented at a high-angle to bedding, forming
30 January 2012
a conjugate pair comprised of compactive strike-slip shear bands. In this study, we focus on the com-
Accepted 2 February 2012
Available online 15 February 2012 pactive shear bands documenting their development, as well as analyzing their dimensional parameters
and scaling relationships.
Single compactive shear bands are thin, tabular zones with porosity less than the surrounding host
Keywords:
Offshore Sicily rocks, and have thicknesses and displacements on the order of a few mm. The growth process for these
Pleistocene deposits structures involves localizing further deformation within zones of closely-spaced compactive shear
Compaction bands bands and, possibly, along continuous slip surfaces within fault rocks overprinting older zones of bands.
Deformation bands During growth, single bands, zones of bands and faults can interact and link, producing larger structures.
Fault scaling The transitions from one growth step to another, which are controlled by changes in the deformation
behavior (i.e. banding vs. faulting), are recorded by different values of the dimensional parameters for the
structures (i.e. length, thickness and displacement). These transitions are also reflected by the ratios and
distributions of the dimensional parameters. Considering the lesser porosity values of the structures with
respect to the host rock, the results of this contribution could be helpful for mapping, assessing, and
simulating carbonate grainstone reservoirs with similar structures.
Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction field characteristics are strictly related to the deformation mecha-
nisms that modify the grain sizes and porosity values within the
Deformation bands are tabular zones mm- to-cm thick, which bands. Microscopic observations of natural deformation bands, as
accommodate shear and/or volumetric strain in porous rocks and well as those obtained from experiments on high-porosity lime-
sediments (Engelder, 1974; Aydin, 1978; Aydin and Johnson, 1978; stones (Vajdova et al., 2004; Baxevanis et al., 2006; Baud et al.,
Antonellini and Aydin, 1994; Aydin et al., 2006; Eichhubl et al., 2009; Vajdova et al., 2010; Zhu et al., 2010; Cilona et al.,
2010; Fossen et al., 2011). Many natural examples of deformation Submitted for publication; Vajdova et al., submitted for
bands are reported from siliciclastic sediments (Fossen et al., 2007; publication), show a variety of mechanisms responsible for their
and references therein). In contrast, only a few field examples of nucleation and development: (i) grain sliding with rotation and
deformation bands are described in porous limestones (Micarelli pore collapse; (ii) grain fracturing; and (iii) pressure solution. The
et al., 2006; Tondi et al., 2006a; Tondi, 2007; Rath et al., 2011). first two mechanisms are responsible for the formation of narrow
Deformation bands are easily recognizable because of their lighter- tabular deformation bands with volumetric and shear strain. If the
colour and positive relief with respect to the parent rocks. These volumetric component of this deformation is negative, the product
is known as a compactive (or compactional) shear band (Aydin
et al., 2006; Tondi et al., 2006a; Fossen et al., 2007; Tondi, 2007),
granulation seams (Pittman, 1981) or disaggregation bands (Fossen
* Corresponding author.
E-mail address: emanuele.tondi@unicam.it (E. Tondi). et al., 2007). At more advanced stages of deformation, within the
0191-8141/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jsg.2012.02.003