First reported occurrence of deformation bands in a platform limestone, the Jurassic Calcare Massiccio Fm., northern Apennines, Italy Marco Antonellini a, ⁎, Lorenzo Petracchini a,b , Andrea Billi b , Davide Scrocca b a Department of Biological, Geological and Environmental Sciences, University of Bologna, via San Alberto 163, 48123 RA, Italy b Institute of Environmental Geology and Geoengineering (IGAG), National Research Council, Rome, Italy abstract article info Article history: Received 22 January 2014 Received in revised form 11 April 2014 Accepted 21 April 2014 Available online xxxx Keywords: Limestones Micromechanics Strain localization Breccia Permeability Two sets of thrust compactive shear bands and one set of dip–slip compactive shear bands with, in places, asso- ciated slip surfaces have been recognized for the first time in a peculiar high-porosity grainstones of the Calcare Massiccio Fm., a Lower Jurassic platform limestone deformed during the development of the late Messinian Cingoli anticline of northern Apennines, Italy. The deformation bands have been studied by field mapping, thin section image analysis, back scatter SEM imaging, and pressure pulse decay minipermeametry. The deformation micro-mechanism in the compactive shear bands is controlled by plastic smearing and grain size reduction of soft micrite peloids with rare grain crushing and even rarer pressure solution. Plastic smearing is characteristic of the micrite peloids and is different from mechanisms occurring in other known carbonate deformation bands where the grains are bioclastic fragments and sparite ooids. The syntectonic diagenetic episode that brought to cement precipitation in the high-porosity grainstones of the Calcare Massiccio caused the loss of porosity and a change in deformation style from strain localization accommodated by banding to classical faulting along slip surfaces accompanied by thick zones of gouge and breccia. The permeability reduction from the host rock normal to the slip surfaces with associated compactive shear bands is, on average, an order of magnitude, which is less than what measured across deformation bands in other porous carbonates. We speculate that the diagenetic his- tory provides a conceivable hypothesis to explain the high porosity in a Mesozoic platform carbonate at the time of orogenic compression (late Messinian), so that deformation bands, hitherto unknown in this type of rock, could develop. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Strain localization due to failure in porous granular rocks is a well- documented process in the geologic literature especially in siliciclastic sedimentary rocks (Aydin et al., 2006; Fossen et al., 2007 and references therein). The process of strain localization results in characteristic tabu- lar structures called deformation bands (sensu Aydin, 1978; Aydin and Johnson, 1978), which can accommodate shear and compaction or even dilatancy (Antonellini et al., 1994; Aydin et al., 2006; Fossen et al., 2007). Depending on some rock properties (i.e., grain size, grain sorting, porosity, and clay content) and on the stress state at the time of their formation, deformation bands may be associated with porosity reduction accomplished by grain sliding and rotation, grain crushing, and pore collapse (Antonellini et al., 1994; Fossen et al., 2007). The development of deformation bands in porous rocks has been a matter of interest especially for the possible effect that may have on fluid flow in otherwise excellent reservoir rocks (Nelson, 2001). The literature characterizing the petrophysical properties of deformation bands in siliciclastic rocks is now large and significant (Antonellini and Aydin, 1994; Ballas et al., 2012, 2013; Balsamo and Storti, 2010; Braathen et al., 2013; Faulkner et al., 2010; Flodin et al., 2001, 2004; Fossen and Bale, 2002; Fowles and Burley, 1994; Lothe et al., 2002; Main et al., 2000; Ngwenya et al., 2003; Shipton et al., 2002; Sternlof et al., 2004; Taylor and Pollard, 2000). Some studies, in particular, have investigated how important are deformation bands in controlling fluid flow in a reservoir and how their effect is most influential at the scale of the wellbore and small reservoir compartments (Ahmadov et al., 2007; Antonellini and Aydin, 1994, 1995; Jourde et al., 2002; Manzocchi et al., 1999; Matthäi et al., 1998; Sternlof et al., 2006). As mentioned above, deformation bands are typical of porous siliciclastic rocks but, recently, a few examples of these structures have also been documented in porous carbonate rocks (i.e., poorly- cemented porous grainstones and chalk) both in nature (Balsamo et al., 2008; Cilona et al., 2012; Micarelli et al., 2006; Rath et al., 2011; Rustichelli et al., 2012; Tondi, 2007; Tondi et al., 2006; Tondi et al., 2012; Wennberg et al., 2013) and in laboratory physical experiments (Baud et al., 2009; Baxevanis et al., 2006; Cilona et al., 2012; Vajdova et al., 2004, 2010, 2012; Zhu et al., 2010). More frequently, rather than deformation bands, shear deformation across carbonate strata leads to the development of mirror-like through-going slip surfaces accompa- nied by gouge and breccia zones (Billi, 2005, 2007; Billi and Salvini, Tectonophysics xxx (2014) xxx–xxx ⁎ Corresponding author. Tel.: +39 339 4978001. E-mail address: m.antonellini@unibo.it (M. Antonellini). TECTO-126288; No of Pages 20 http://dx.doi.org/10.1016/j.tecto.2014.04.034 0040-1951/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto Please cite this article as: Antonellini, M., et al., First reported occurrence of deformation bands in a platform limestone, the Jurassic Calcare Massiccio Fm., northern Apennines, Italy, Tectonophysics (2014), http://dx.doi.org/10.1016/j.tecto.2014.04.034