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1 Tectonophysics 467 (2009) Contents lists available at ScienceDirect Tectonophysics journal homepage: Re-computing palaeopoles for the effects of tectonic finite strain Graham J. Borradaile, Thomas D. Hamilton Faculty of Science, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1 article info abstract Article history: Received 26 July 2008 Received in revised form 15 November 2008 Accepted 30 December 2008 Available online 11 January 2009 Keywords: Palaeomagnetism Strain De-straining APWP Magnetic fabrics Cyprus The pre-messinian limestone cover ( 58 8 Ma) to the Troodos ophiolite ( 88 Ma) of southern Cyprus is penetratively strained as shown by ubiquitous magnetic fabrics and, in many sites, stylolitic cleavage. These define a gently N-dipping foliation and an N-plunging extension. South-vergent folding and thrusting is well known in very localized whereas the bulk of the strained limestone cover dips gently south, disturbed by faulting. The magnetic fabrics and stylolitic cleavage define the axes of finite strain in all sites studied, and the calcite matrix was suitably ductile to permit the original palaeomagnetic directions to be de-strained assuming continuum behaviour. The optimum de-straining (30 40% shortening in a flattening strain) is compatible with the stylolitic cleavage development, restores bedding to the near-horizontal, and restores the characteristic remanent magnetization vectors (ChRMs) to concentrated, symmetrical Fisherian distributions. The strain-corrected ChRMs yield more reasonable palaeopole locations for the Lefkara and Pakhna Limestone and more uniform micro-plate rotation rates. Corrected palaeopoles reveal a relatively uniform anticlockwise rotation of the Troodos plate since the creation of the late Cretaceous ( 88 Ma) ocean lithosphere. It did not accelerate during the deposition of the limestone cover as required by palaeopoles calculated from data not corrected for finite strain but turned at 1.5 Ma 1 since 58 Ma Elsevier B.V. All rights reserved. 1. Goal We re-examine the rarely testable notion that homogeneous strain may account for the sense, and possibly amount by which palaeomagnetic vectors are re-oriented by regional finite strain. Finite strain is of course one aspect of tectonic deformation which also encompasses translation, rigid body rotation and in some cases volume changes. We shall show that correcting ChRM orientations for finite strain provides for their complete and satisfactory restoration in most cases. In general, the survival of palaeomagnetic vectors is also sensitive to stress (e.g., Kern, 1961; Carmichael, 1968; Pozzi and Aïfa, 1989). Stress is an ephemeral field tensor; it cannot be related to finite strain which is a material tensor (Nye, 1957). Stress (associated with small strains) may remove important magnetic components (demagnetization) or overprint them (remagnetization) (inter alia, Borradaile, 1991, 1992a,b, 1993a,b, 1994, 1996; Borradaile and Jackson, 1993; Borradaile and Mothersill, 1989, 1991; Kern, 1961; Jun and Merrill, 1995; Pozzi and Aïfa, 1989; Ye and Merrill, 1995). However, if the characteristic remanent magnetization (ChRM) vector is carried by rigid grains of low aspect ratio in a ductile matrix, the grains and their suitable resistant ChRM vectors may approximately re-orient like passive linear markers (Borradaile, 1993a,b; Cogné, 1987a,b; 1988; Cogné and Corresponding author. addresses: troodos@tbaytel.net, borradaile@sapphiremagnetics.com (G.J. Borradaile). Gapais, 1986; Cogné and Perroud, 1985; Kligfield et al., 1983; Kodama, 1988; Lowrie et al., 1986), according to continuum-mechanical theory (Flinn, 1962; Ramsay, 1967). ChRM vectors, if passive lines would be expected to spin, mostly indirectly, toward the X-axis of the finite strain ellipsoid where X Y Z are the principal axes. Within the limits of measurement-uncertainty the above mentioned field and laboratory studies confirmed that either hematite or magnetite ChRMs may rotate in a similar sense to that expected of passive linear markers in continuum mechanics (Means, 1976; Bayly, 1992, e.g., here Fig. 3c). These successful verifications used examples with low strain (e.g., slaty or stylolitic cleavage, 40% shortening), near-coaxial strain and homogeneous strain. For folded rocks, which are examples of heterogeneous strain by definition, authors analyzed portions that were approximately homogeneously strained and integrated or compared each differently strained homogeneous portion. Moreover, such previous successful de-straining studies appear to have been fortunate in choosing ChRMs that were carried by coercive magnetic domains, which are most immune to demagnetization or remagnetization. It is easy to understand that room-pressure analog experiments using plasticine produce ChRM orientations and magnetic fabrics develop compatibly with the continuum mechanics concept of passive line rotations (Cogné, 1987a; Borradaile and Puumala, 1989). However, high pressure experiments with natural carbonate-rich rocks or synthetic limestone show that depending on the coercivity of the remanence-bearing grains, different magnetic moments may be preserved, demagnetized, reoriented towards the maximum extension, X or even rotate counterintuitively away from X (Borradaile, 1992a,b, 1994; Borradaile and /$ see front matter 2009 Elsevier B.V. All rights reserved. doi: /j.tecto

2 132 G.J. Borradaile, T.D. Hamilton / Tectonophysics 467 (2009) Mothersill, 1989, 1991; Jackson et al., 1993). Whereas the field studies approximately verify the re-orientation of ChRMs according to the passive line spin hypothesis (Fig. 3c) (inter alia Cogné, 1987a,b, 1988; Cogné and Perroud, 1985; Hirt et al., 1986; Hudson et al., 1989; Kodama, 1988; Kligfield et al., 1983; Lowrie et al., 1986, Stamatakos and Kodama, 1991a,b; Vetter et al., 1989; Werner and Borradaile, 1996), magnitudes of the vector rotation have never been corroborated. The difficulty arises because the vector-mean ChRM direction must be determined statistically from a symmetrical, clustered sample of directions. Strain changes the shape and symmetry of the orientation distribution and complicates the interpretation of its mean-vector in ways that have not been fully appreciated, as we shall show (Fig. 4). The limestone cover to Cyprus's Troodos ophiolite provides conditions that approximate the requirements of passive line behaviour of ChRM as closely satisfied as one is ever likely to encounter in nature. ChRM is borne by very fine-grained pseudo-single domain clastic magnetite (or titanomagnetite) in fine-grained limestone or chalk matrices. Strain is low, mostly 20 40% shortening (Z) perpendicular to a Fig. 1. (a) Outline geological map of Cyprus (Geological Survey Department of Cyprus), with our detailed sampling areas boxed. (b) Young, mainly Miocene and later tectonic features of Cyprus and the surrounding area (Arvidsson et al., 1998; Ben-Avraham et al., 1988; Borradaile and Hamilton, 2004; Kempler and Ben-Avraham, 1987; Robertson et al., 1995).

3 G.J. Borradaile, T.D. Hamilton / Tectonophysics 467 (2009) stylolitic cleavage. Penetrative petrofabrics parallel to cleavage are revealed by anisotropy of magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence (AARM) (Lagroix and Borradaile, 2000; Hamilton et al., 2004). Since AARM isolates the preferred orientation of magnetite, it is a logical de-straining tool for remanences carried by the magnetite. This has been successfully used in the restoration of sedimentary compaction (Jackson 1991; Jackson et al., 1991; Kodama and Sun, 1992; Tan and Kodama, 2002; Borradaile and Almqvist, 2008). Unfortunately, in the limestone studied here the technique is foiled because specimens with sufficient magnetite content for AARMdetermination also have unstable remanences. The analogy between the finite strain ellipsoid and the AMS ellipsoid of a strained rock is imperfect but correspondence of principal axial orientations is usually accepted (Borradaile, 1991, Borradaile and Henry, 1997; Borradaile and Jackson, 2004). The previously reported parallelism of the magnetic fabric ellipsoids with cleavage and extension lineations, confirms the association here. 2. Tectonics and regional geology The Cretaceous Troodos ophiolite of Cyprus formed due to ocean floor spreading events in the Neo-Tethys Ocean (Gass, 1990; Panayides et al., 2000; Robertson, 1990, 2000; Robertson et al., 1995). Ophiolitic plutonic crystallization and transform fault metamorphism occurred in the late Cretaceous at ~90±2 Ma (Spray and Roddick, 1981; Mukasa and Ludden, 1987) and volcanism ceased ~75±5 Ma (Blow, 1969; Mantis, 1970; Delaloye and Desmet, 1979; Delaloye et al., 1980; Irwin et al., 1980; Blome and Irwin, 1985). However, ocean-floor metamorphism for the dike complex (Varga et al., 1999) post-dated primary crystallization by at least 1 Ma (Borradaile and Gauthier, 2006) and probably by as much as 7 to 15 Ma (Staudigel et al., 1986). Thus palaeomagnetic signals are significantly younger than igneous crystallization. The Troodos Ophiolitic terrane subsequently amalgamated with the Triassic Mamonia terrane to the SW and the Post- Carboniferous Kyrenia terrane to the North (Fig. 1a) (Robertson, 2000; Bailey et al., 2000; Panayides et al., 2000; LaPierre et al., 2007, 1995, 2000). After a considerable hiatus, a dominantly upwards shallowing limestone sequence decked the ophiolite terrane above the volcanic sequences, commencing with the Lefkara Group (~58 17 Ma). Near the top of the Lefkara Group, a significant submarine hiatus was caused by a change in global climate and oceanic-circulation. The unconformably succeeding Pakhna Limestone Formation (approximately 17 6 Ma) forms the bulk of the remaining sedimentary rock covering the ophiolite. Stratigraphic history is comprehensively and rigorously reviewed by Vali et al., 1980; Haq et al., 1987; Robertson et al., 1991; Kähler and Stow, 1998; Lord et al., 2000). Lefkara and Pakhna Group stratigraphy is complex; units are diachronous and vary enormously in development, in facies and in thickness around the updomed ophiolite (Fig. 1a). Therefore, precise ages cannot be associated with palaeomagnetic sites. At the present time, we broadly associate palaeomagnetic data to the categories of Lower Lefkara, Upper Lefkara and Pakhna Groups (Fig. 2). Especially south of the Troodos Tectonic Fig. 2. Principal stratigraphic elements of the Troodos terrane (of Fig. 1) in Cyprus. (Geological Survey Department of Cyprus, 1979; and inter alia Haq et al., 1987; Malpas et al., 1990; Robertson et al., 1991; Vali et al., 1980; Kahler and Stow, 1998; Lord et al., 2000; Orsag-Sperber et al., 1989; Panayides et al., 2000).

4 134 G.J. Borradaile, T.D. Hamilton / Tectonophysics 467 (2009) Front, a line which partly corresponds with a fossil transform fault zone (Gass et al., 1994; Fig. 1a), the Lefkara and most of the Pakhna limestone sequences were tectonically deformed by a Late Miocene event, followed by a Messinian (~8 Ma) unconformity. This produced a gently north-dipping stylolitic cleavage at many sites and an N- dipping extension lineation shown by slickenfibres and strain shadows. However, every pre-messinian limestone site we sampled shows a magnetic fabric compatible with the macroscopic stylolitic cleavage. This is revealed by anisotropy of magnetic susceptibility (AMS) and by anisotropy of anhysteretic remanent magnetization (AARM) (Lagroix and Borradaile, 2000; Hamilton et al., 2004). AMS fabrics are mostly controlled by the preferred orientation of clastic magnetite with some contribution from clay minerals. Calcite-rich rocks may have a net diamagnetic bulk susceptibility that produces an inverse fabric (Borradaile and Jackson, 2004; Hamilton et al., 2004). AARM is solely due to the preferred shape orientation of clastic remanence-bearing minerals, magnetite or titanomagnetite. AARM may only be determined in specimens containing sufficient magnetite or titanomagnetite; they are unsuitable for palaeomagnetic work because their remanences are too unstable. The principal axes of the AMS fabric ellipsoid (k MAX k INT k MIN )define a magnetic foliation (k MAX k INT ) sub-parallel to the N-dipping stylolitic cleavage and the magnetic lineation (k MAX ) plunges North (Lagroix and Borradaile, 2000; Hamilton et al., 2004). This is compatible with the Late Miocene (Messinian) south vergent thrusting caused by subduction of the African Plate, to the south of Cyprus (Fig. 1b) (inter alia, Kempler and Ben-Avraham, 1987; Ben-Avraham et al., 1988; Robertson et al., 1995; Arvidsson et al., 1998; Papazachos and Papaioannou, 1999; Borradaile and Hamilton, 2004). Note that the Late Miocene deformation produced widespread tectonic fabrics over southern Cyprus (Lagroix and Borradaile, 2000), and is not restricted to limited areas of prominent folding and thrusting as previously thought (e.g. Yeresa, Limassol Forest, Fig. 1b; e.g., Grand et al., 1993). It is therefore an inescapable conclusion that to some extent the Late Miocene tectonic event may have affected any palaeomagnetic records, including the ChRMs, in pre-messinian (N8 Ma) rocks (Fig. 2). 3. Palaeomagnetic data Palaeomagnetic data were selected from subareas (Fig. 1a) after all of the limestone cover had been regionally sampled for earlier more extensive magnetic fabric studies and pilot palaeomagnetic work. The subareas used here were sampled with strict regard to stratigraphic order, oriented blocks (2 4 kg) being removed in the field from 62 sites. These were shipped to Canada and drilled in geographic coordinates in the laboratory under a water-cooled drill-press. We drilled four to six cores per block, each core being 25 mm diameter 22 mm high. Every core was demagnetized by three cycles of low-temperature demagnetization, followed by thermal demagnetization in a Shaw MMTD80 unit in at least 8 steps including 200, 250, 300, 325, 250, 375, 400, 450, and 500 C. Remanences were measured in an AGICO automatic spinner magnetometer with a precision of better than 0.01 ma/m. Characteristic remanent magnetizations (ChRMs) were isolated by vector analysis of fully demagnetized specimens, using four or more co-linear demagnetization points. Classical field stability tests (Van der Voo, 1993) poorly constrain the primary age of the ChRM. The fold test is inconclusive for Miocene folding of Lefkara and Pakhna Limestone although remanences in clasts of Pakhna and Lefkara limestone are stable in Pliocene conglomerate. Almost anti-parallel ChRM vectors in some Pakhna and Lefkara limestone sites record reversals of the geomagnetic field and therefore favour an ancient and probably primary age (the reversal test; McFadden and McElhinny, 1990; Van der Voo, 1993). The greatest concern for palaeomagnetic interpretation is that the Late Miocene (Pre-Messinian) regional deformation produced widespread N-dipping stylolitic cleavage and concordant AMS tectonic fabrics in the Lefkara and Pakhna Limestone. Commonly, this partly or completely reset their palaeomagnetic signals by demagnetizing vector components, by adding others, by remagnetization or by spinning stable ChRM components due to finite strain. Of course, young viscous magnetizations were acquired by deep parts of the ophiolite sequence also when they were uplifted to suitable levels (Hall et al., 1995, 1997). We exclude sites and lithologies with obviously young viscous remagnetization overprints that occurred mainly during the Pliocene and younger uplift of the Troodos mountain range. 4. Structure, strain and palaeomagnetism For many sites, strain and the development of stylolitic cleavage may have enhanced the clustering or concentration of ChRM directions. This is evident from comparisons of the qualitative cleavage development with the Fisher precision (k) of ChRM directions (Table 1). Of course, AMS permits the magnetic fabrics to be quantified but it is now wellknown that that only the orientations of AMS axes are coaxial with those of the finite strain ellipsoid. AMS magnitudes do not quantify strain magnitudes because a rock's AMS blends contributions from different minerals that have different abundances, mean susceptibility, orientation distribution, and susceptibility anisotropy (Borradaile, 1987, 1988; Borradaile and Henry, 1997; Borradaile and Jackson, 2004). However, in general, the most abundant and most susceptible mineral may dominate the overall AMS fabric and the orientation of the AMS axes is usually coaxial with the finite strain petrofabric, as here. In the strained limestone we describe, traces of clastic magnetite or sometimes clay dictate the rock's AMS axial orientations. These invariably agree with one another as shown by earlier studies of AARM, which isolates the orientation distribution of magnetite (Lagroix and Borradaile, 2000). The tectonic history is rather simple, a single planar fabric was imposed on the calcite matrix, with stylolitic cleavage development (Lagroix and Borradaile, 2000). The AMS foliation due to clay and magnetite preferred orientations is nearly parallel to the stylolitic cleavage and the AMS lineation dips gently northward, as do slickenfibres on the stylolitic cleavage. The ratio between the magnitudes of AMS axes is usually compatible with the symmetry or shape of the finite strain ellipsoid, as shown by many previous studies. Thus, a flat-shaped AMS ellipsoid corresponds to a flat-shaped finite strain ellipsoid and a rod-shaped AMS ellipsoid corresponds to constrictive strain (rod-shaped finite strain ellipsoid). Ratios of the AMS principal magnitudes define the AMS ellipsoid shape but the shapes and orientations of confidence regions for the mean tensor of a sample of AMS specimens may provide even more information on the symmetry and coaxiality of strain and fabric history (Borradaile, 2001a) Palaeomagnetic vectors and finite strain Where beds are tilted without distortion, ChRM vectors rotate with the rock as linear markers and they may be simply restored by backrotation. MacDonald (1980) established rigorously the conditions necessary to restore tilted palaeomagnetic vectors; including by multiple and inclined rotation axes. To determine the ChRM's original Table 1 Fabric category Qualitative fabric feature Fisher's precision (i) Bedding-parallel fabrics alone. kb10 (ii) Penetrative grain alignment and shaping of clasts and fossils due to pressure solution in at least 20% of the specimen, but mostly parallel to bedding k=13.9 (iii) Grain-shaping and pressure solution inclined to k=25.6 bedding in N20% of the specimen. (iv) Discrete (spaced) stylolitic seams inclined to k=30.7 bedding, including the features of (ii). (Cleavage dips gently northward sub-parallel to AMS foliation) Mean unitvector R=0.93 R=0.96 R=0.97

5 G.J. Borradaile, T.D. Hamilton / Tectonophysics 467 (2009) orientation unequivocally this requires a complete knowledge of the orientation of the rotation axis, the rotation angle and, if more than one rotation is involved, the order of the rotations must be known. Where strata have been strained (=changed in shape), de-tilting techniques are entirely inappropriate to restore ChRM directions (Fig. 3a; Borradaile, 1997). There are two fundamental issues. Fig. 3. (a) Most palaeomagnetic studiesrestrict tectonic restorations to situationsinwhichstrata havebeentilted only. Thus, they were affected by rigid bodyrotation andnot by finite strain (=shapechange). Theoutcomes ofrigid body rotation and offinite strain are invariably quite different and thesequence ofsuccessiverigid bodyrotations, orof strains orofanycombination of rotations and strains is an important control on the final state. (b) The simplest case of rigid-body-rotation, tilting about a horizontal axis. The effects are simply predicted as the ChRM vectors move along small circles to which the rotation axis is coaxial. Geological examples may involve non-horizontal rotation axes and multiple tilting events, and may still involve inherent ambiguities, e.g., theoriginaldeclination (Mac Donald,1980). (c) March (1932) and Flinn (1962) pioneeredtheunderstandingofthe fundamentalprinciplesby which passivelinear markers rotate during progressive finite strain. Here are shown movement paths for passive linear markers for a specific finite strain in a coaxial history. Specific results depend on X:Y:Z ratios and the principal axes' orientations and in nature. For simplicity only a coaxial strain history is illustrated (principal strain axes remain fixed relative to material lines). An example of the trajectories of passive linear markers is shown for the finite strain specified. A ChRM vector would follow such a path, if it behaved as a passive marker.

6 136 G.J. Borradaile, T.D. Hamilton / Tectonophysics 467 (2009) Fig. 4. A superficial examination of Fig. 3 may suggest that progressive strainalways improves the concentration of a clusteringof axes or directions. Even for a coaxial strain history this is not always the case. (a) For example, the circular concentration of passive linear markers (cf. Fisher distribution of ChRMs) shown here is progressively dispersed into an elongate, asymmetric concentration. (b d) During this progressivecoaxialstrainhistory, theoriginal concentrationisdispersedinto a bimodaldistribution. (e g) Furtherpossibilitiesfordispersalof concentrations duringprogressive strain exist innon-coaxialstrainhistories (X, Y, Z axes changingorientationwith respect to material lines). Theresulting distribution maybedifficultto interpret interms of finite strain or the orientation and shape of the original distribution.

7 G.J. Borradaile, T.D. Hamilton / Tectonophysics 467 (2009) First, the simple rigid-body rotation process (Fig. 3b) is inappropriate where the material has changed shape. The trajectory of a strained passive linear marker is much more complex, as a simple, coaxial specific example shows (Fig. 3c). The spin-path of the passive line is towards X but not necessarily directly, depending on the ratios of the principal finite strain axes (X Y Z), and their orientations (Flinn 1962), e.g., Fig. 3c. Note that this is a very simple coaxial example of finite strain in which the X, Y and Z axes remain in constant orientation with respect to material lines. Furthermore, analysis is for simplicity restricted to homogeneously strained volumes; those in which straight lines remain straight, parallel lines remain parallel and a single strain ellipsoid describes the state of strain. The notion of passive-line spinning (Fig. 3c) was introduced by March (1932), however full evaluations appeared later (Flinn, 1962; Ramsay, 1967). However, a superficial examination of Fig. 3c may give the false impression that all coaxial finite strain enhances the concentration of passive lines. On the contrary, the initial orientation of the passive lines with respect to X, Y and Z is critical. In palaeomagnetism, the ChRM is a mean-vector of a distribution of directions and therefore the location and scatter of the initial directions complicates matters further. For example, in Fig. 4a we see that a progressive coaxial strain may disperse an initial concentration to a non-fisherian (and also non-bingham) ovoid and asymmetric distribution on the sphere. In another case, we see that coaxial progressive strain may split an initial concentration into a bimodal distribution (Fig. 4b d). In the worst case of markedly non-coaxial strain, initial concentrations of all initial orientations will remain dispersed, oval and asymmetric (Fig. 4e g). Thus, an important criterion of successful de-straining is that the destrained distribution will be symmetric and reasonably concentrated. It is not necessary that the restored distribution will be more concentrated than the distribution in the strained state, as Fig. 4 shows. The second assumption of remanence de-straining invokes noncontinuum issues that in some cases are unknowable (Borradaile, 1997). In reality ChRM vector cannot be a passive line; it is a vector sum of spin-moments from different remanence-bearing minerals (RBM), and from different domains within those grains (Dunlop and Özdemir, 1997). The passive line model can at best only be an approximation that is satisfied within the limits of experimental uncertainty. Even small experimental strains (b8% shortening; Borradaile, 1997) may produce paradoxical changes in the sample's net remanence because lattice distortions permit demagnetization and remagnetization at the grain or domain scale. Nevertheless, the continuum mechanics, passive-line hypothesis for the behaviour of ChRM re-orientation has been moderately successful for a limited range of rock types and weakly strained materials in nature (inter alia Kligfield et al., 1983; Lowrie et al., 1986; Kodama, 1988). The appropriateness of the continuum-mechanics hypothesis is favoured when the matrix is ductile with respect to the RBM and when the RBM grains have a low aspect ratio. This has been verified experimentally with limestone analogues in high pressure triaxial experiments, including incremental straining and remanence measurement during various stages of the experimental strain history (Borradaile, 1991, 1992a,b, 1993a,b; Robion and Borradaile, 2001). ChRM is preserved in grains of a suitable coercivity range, escaping the remagnetization which occurs at low differential stresses and at very low strains. The incremental-strain rock-mechanics experiments showed that the ChRM vectors of suitable coercivity appear to follow passive-line spin trajectories with net spin angles compatible with known strain magnitudes. In this study of natural rocks there are no readily useable finite strain markers such as ooids or suitably abundant fossils) but our experience of stylolitic cleavage is that the grain-microfabric development shown here is associated with 30 40% shortening (Borradaile et al., 1982). An example of the abundant stylolitic cleavage is shown in Fig De-straining passively rotated linear markers As the orientation of a passive line is restored for finite homogeneous strain it simply follows the reverse trajectory of a passive line in progressive strain. This, as well as the more common de-tilting procedure, is achieved in part of our palaeomagnetic software for the Molspin and AGICO spinner magnetometers (SPIN06.EXE). De-straining requires two important items of information. First, the orientation of the finite strain axes (X Y Z) must be known. Stylolitic cleavage is generally regarded as a good approximation to the XY-plane since it is a manifestation of pressure solution; moreover slickenfibres on the stylolitic cleavage usually define the stretching lineation (X). Moreover, these directions are coaxial with the AMS magnetic fabric axes (k MAX k INT k MIN ) (and also with the AARM fabric axes (Lagroix and Borradaile, 2000). Second, we must Fig. 5. Example of widespread stylolitic cleavage in the field, here in the Lefkara Formation, near Lefkara. Orientations of strata and stylolitic cleavage are typical for much of the limestone cover; strata dip gently southward and spaced stylolitic cleavage dips gently northward.