Geology and structure of the Serre Massif upper crust: a look in to the late-Variscan strike–slip kinematics of the Southern European Variscan chain

ABSTRACT A new geological-structural map of the southern Serre Massif (SM), in the south-central part of the Calabrian-Peloritani-Orogen (CPO), is provided. CPO is a ribbon-like microplates puzzle, originally belonging to the southern European Variscan Belt and, later involved into the Alpine geodynamics of the central Mediterranean Area. The SM represents one of the key European Variscan basement relicts, because of its exhumation mechanisms as well as for the absence of any Alpine metamorphic overprint. This map has the aim to better delineate the sequence of the Variscan blasto-deformational relationships consisting in a prograde multistage history, followed by an extensional/transpressional multistage retrograde evolution, which triggered the intrusion of the former plutonic products. The mylonitic fabric resulted finally replaced by the effects of the late- to post-kinematic plutonic intrusions coeval with a former late-Variscan exhumation stage, followed, during Mesozoic, by carbonate platform sedimentation, before to be completed exhumed during the Oligocene-Miocene Alpine stages.

The initial crustal thickening stage, averagely aged from 360 to 340 Ma (e.g. Fornelli et al., 2020), was followed by the activation of deep-seated strike-slip shear zones, within an overall contraction regime, linked to the mutual movement of Gondwana and Laurussia, operating from 344 to 300 Ma (Figure 1(a)).
The subsequent counter-clockwise rotation of the African plate triggered the former stages of the Alpine orogenesis, causing the further fragmentation of the original southern European Variscan chain. This stage was favored by the activation of new crustalscale shear zones which controlled the Oligocene-Miocene microplates movement of the western Mediterranean realm (Figure 1(b) and Figure 2) (Brandt & Schenk, 2020;Cirrincione et al., 2015;Festa et al., 2016Festa et al., , 2020Ortolano et al., 2020a).
In this geodynamic scenario, is born the Calabria-Peloritani-Orogen (CPO), mostly interpreted as a southward shifted fragment of the original European continent, drifted, in the present-day position, as a consequence of the slab roll-back of the subducting Ionian microplate (i.e. a relic of the neo-Thetyan oceanic crust) (Haccard et al., 1972;Malinverno & Ryan, 1986), controlling also the opening of the Tyrrhenian basin (Figure 1(b)).
The unitary geodynamic evolution of the CPO basements units is still discussed by various authors (e.g. Alvarez & Shimabukuro, 2009;Cirrincione et al., 2015;Critelli, 2018;Critelli et al., 2017), that distinguished at least two main sectors: (a) the northern sector, including the Catena Costiera and Sila Massif, where oceanic units are located between the overlying pre-Mesozoic continental crustal rocks and the underlying carbonate Apennine units (Appendix 1 -Geological framework); and (b) the southern sector, including the Serre and Aspromonte Massifs in the central-southern Calabria and the Peloritani Mountains in the north-eastern Sicily, where only continental crust-derived units occur (Appendix 1 -Geological framework).
Within the southern CPO it is possible further subdivide the Serre Massif from the Aspromonte and Peloritani Mountains, in view of the pervasive Oligocene Alpine metamorphic overprint recognized only in the central and eastern sector of the Aspromonte Massif Fazio et al., 2015bFazio et al., , 2018Fazio et al., , 2020Ortolano et al., 2005Ortolano et al., , 2015Pezzino et al., 2008) and along the boundary between the two uppermost units of the Peloritani Mountains (Cirrincione et al., 2012a). The Serre Massif is indeed devoid of any Alpine metamorphic overprint and it is constituted by an almost complete continental crustal section, totally surfacing after an asymmetric tilting, due to the extensional (Festa et al., 2013) vs. transpressional exhumation (Fiannacca et al., 2021) of the original southern European Variscan basement (Cirrincione et al., , 2012aFazio et al., 2018;Ortolano et al., 2015).
In particular, this new geological-structural map delineates the boundary among the intermediate (i.e. the late Variscan granitoids), to the upper portion (i.e. the SPC and the MPC) of the Serre Massif metamorphic crustal section, and its Mesozoic sedimentary sequence (Figure 2), with a special look into the exhumation mechanisms of this original southern European Variscan basement crust.
2. The geological-structural map of the Serre Massif upper crust

General outlines
The geological-structural map of the southern Serre Massif covers an area of ∼290 km 2 in the CPO central-southern edge, and represents a revised merge of two original geological surveys (1:10000 scale).
Base map consists of contour lines (drawn every 50 m, labeled every 100 m), derived from the Digital Terrain Model (DTM) downloaded from the geodata website of the Calabrian Region (5 meters per pixel), also used to obtain the used hillshade effect (i.e. a virtual shaded relief) as well as the others geomorphological features (see supplementary material-SM1).
This new geological-structural map holds detailed information related to the tectono-metamorphic, -magmatic and -sedimentary evolution of the upper continental crust of the Serre Massif crustal section ( Figure 2). The metamorphic and plutonic complexes here outcropping are mainly characterized by the superposition of an upper low-grade metamorphic complex (Stilo-Pazzano Complex -SPC) on a relatively high-grade metamorphic one (Mammola Paragneiss Complex -MPC), along a late-Variscan lowangle tectonic detachment (Figure 2) (Appendix 1; 2). Both the complexes share the same static metamorphic overprint related to the contact metamorphism due to the emplacement of the late-Variscan plutonic suite of the Serre Batholith (Angì et al., 2010;Bonardi et al., 1987;Cirrincione et al., 2012b;Festa et al., 2013;Fiannacca et al., 2015Fiannacca et al., , 2017Fiannacca et al., , 2019Rottura et al., 1990), followed by the final intrusion of late to post-Variscan felsic to mafic dykes (Romano et al., 2011).
The map runs along the preserved primary boundary between the Serre Batholith and the metamorphic units, along which, a variably thick contact aureole occurs (Appendix 2).
To the south, the map intercepts the geological boundary between the Serre and the Aspromonte Massifs, where an already active deep-seated strikeslip fault system occurs. According to Ortolano et al. (2013Ortolano et al. ( , 2020a, Cirrincione et al. (2015) and Tripodi et al. (2018), this strike-slip system was recently interpreted as the natural continuation of the meso-to neo-Alpine strike-slip mylonitic Palmi Shear Zone (Appendix 1 -Geological framework).

Mammola paragneiss complex (MPC)
The MPC rocks crop out in the central part of the map with continuity from Mammola Village to Mt S. Andrea, and subordinately in the westernmost part. It is mainly composed of a paragneiss-micaschist sequence with local leucocratic orthogneiss and subordinate meter intercalations of amphibolite.
Field and microscopic investigations (see SM2) permitted the identification of two different metamorphic cycles: (a) an elder eo-Variscan polyphase syn-orogenic metamorphism (D 1 → M 1 and D 2 → M 2 phases) ended with a retrograde mylonitic evolution (D 3 → M 3 ) followed by (b) a late-to post-tectonic metamorphic overprint (M 4 ), caused by the intrusion of the late-Variscan granitoids.
The structural features are mainly linked to the retrograde shearing evolution of the first cycle (D 3 → M 3 ), often characterized by transpressional-type structural features along the widely preserved pervasive subvertical foliations (Figure 3(a)). Kinematic indicators, lying on the XZ plane of the finite strain ellipsoid, are consistent with a dextral shear sense and an ENE tectonic transport in the present-day geographic coordinates (Figure 3(ad)). Two different types of isoclinal fold sections lying on YZ plane of the finite strain ellipsoid are observed: (a) the first one is clearly in continuity with the mylonitic foliation with axes parallel to the stretching lineation, here interpreted as a syn-shearing oblique folding formation (Figure 3(e)) rather than a post-mylonitic isoclinal folding (Festa et al., 2018); (b) the second one, preserves an axial plane foliation S 1 in low strain domains lined up along the mylonitic foliation (Figure 3(f)). In the michaschist levels a centimeter wavelength microfolding forms a less developed S 2 foliation (Figure 3(g)).
Attitudes orientation pattern of the field foliation (S 3 ) maintains a similar distribution from the easternup to the western-sector of the central mapped area, showing a well-developed single girdle distribution of poles to planes, consistent with a folding system characterized by a sub-horizontal or less inclined axis, oriented from NE-SW to ENE-WSW (Figure 4 (a,b)) (Appendix 2). Obtained π axis is very well consistent with the b 4 measured axes (Figure 4(a,b)), which can be ascribed to a late-Variscan deformational stage D 4 , due to the syn-compressional emplacement mechanism of the pluton, as testified also by the parallel orientation between the primary contact with granodiorite body and the average axis of the folding system ( Figure 2) (Appendices 1, 2). Stretching-lineation L 3 shows a main ENE-WSW trend with a subordinate NE-SW one. The first one is parallel with the oblique-fold axes b 3 highlighting the syncinematism of both structures (Figure 3(e); Figure 4(a)), differently, the less preserved NE-SW L 3 trend can be interpreted as linked to an early-D 3 extensional deformative stage, alternatively plunging to NE or SW as response to the D 4 dispersion ( Figure 2; Figure 4(a)).

Stilo-Pazzano complex (SPC)
The SPC includes lower greenschist facies metapelites interbedded with minor metalimestone and metabasite. It extends continuously along the north-eastern portion of the map, from Stilo, Pazzano and Bivongi to Popelli villages. Minor outcrops are in Caturello riverbed and near Martone village. Another important bodies of the SPC phyllites extensively crop outs at the base of the Mesozoic Monte Mutolo sedimentary sequence ( Figure 5), as well as located between the two tributaries of the Antonimina River (i.e. The Portigliola and Cortaglia rivers), where spotted phyllites crop outs directly in contact with the migmatitic paragneisses of the Aspromonte Unit. Similarly to the MPC, two metamorphic cycles have been recognized after field and microscopical investigations (see SM2): (a) an elder Variscan polyphasic regional metamorphism (D 1 → M 1 and D 2 → M 2 phases) followed by a less evident retrograde mylonitic stage (D 3 → M 3 phase) and (b) a thermal overprint due to the intrusion of late-Variscan plutonic suite (M 4 ). The first deformational phase (D 1 ) determined an isoclinal folding (b 1 fold axes, spanning from a main NW-SE orientation to a subordinate E-W direction) ( Figure  4(b)) of the S 0 surface, associated with the development of an axial plane foliation (S 1 ) (Figure 6(a)). The subsequent deformational stage (D 2 ) produced the crenulation of the S 1 with consequent micro-folding formation from centimetric-up to submillimetrewavelength ( Figure 6(b)). The D 2 stage is linked with the development of a new incipient to pervasive surface (S 2 ) and an axial culmination lineation (L 2 ) with very variable orientation spanning from the main NE-SW to NNE-SSW and a minor cluster oriented to SE (Figure 4(b)). The D 3 deformational stage experienced in MPC lithotypes is not well observable in the SPC rocks, even though, widespread unrooted lenses of isoclinal folds (Figure 6(c)) can be interpreted as linked with the same early-D 3 mylonitic phase already observed in the MPC. Moreover, the local preservation of sub-vertical foliation (Figure 6 (d)), can be linked to the late-D 3 transpressional phase well recognized in the MPC (Figure 6(d ′ )). The late-to post-kinematic intrusion of the plutonic body emplacement extensively produced spotted phyllites. This last metamorphic phase produced: (a) in peripheral contact aureole zone, 0.5-2 mm sized ellipsoidal cordierite spots, overgrowing locally on preexistent fabrics; (b) approaching the contact, an abrupt texture variation with the transition to foliation-lacking hornfels, where cordierite gradually leaves the place to biotite and andalusite porphyroblasts (Figure 6 (e)) (Appendix 2).
The following D 4 deformational stage is correlated, also in this case, to the syn-to late-kinematic intrusion of the main granodiorite body, as testified by the same main rotation axis b 4 observed in the MPC, always sub-parallel with the primary contact with the granodiorite batholith. This suggests that the syn-compressional emplacement of the main plutonic body, caused the folding of the main foliation that, in the case of the SPC phyllites, correspond to a S 1≡ S 3 parallel foliation. Aplite-pegmatite dyke intrusions closed the second stage of the static cycle.
During the Mesozoic period, thin sea carbonate sediments were deposited on the SPC phyllites, interrupted by more or less wide gaps probably due to repeated emersion testified by paleosols or moderate Cutting according to the YZ ellipsoid section (B 3 is the axis of the oblique folding generated during the strike-slip movement. S 3 is the mylonitic field-foliation). (f) Axial plane foliation preserved within a relic of isoclinal folding (S 1 is the relic axial plane foliation preserved as low-strain domain within the S 3 mylonitic field-foliation. B 1 is the axis of the isoclinal folding event produced during the first recognized deformational phase D 1 ). (g) Subperpendicular foliation produced by a centimeter wavelength crenulation in micaschist levels (B 2 stay for wavelength centimeter axis produced during the D 2 event. See text for more explanation). (h) Post-tectonic paraconcordant dyke and late-tectonic dyke characterized by supra-solidus deformative structures (h ′ '). (i) Discordant post-tectonic aplitic dyke. thicknesses of 'Verrucano' type clastic deposits (Bonardi et al., 1984). This initial sedimentation was replaced by dolomite covered in turn by whitish and pearl-gray calcarenites and calcirudites, sometimes with a pinkish micritic matrix, breccias and reef limestones with ellipsactinias, corals and gastropods, and light gray calcarenites and calcirudites with Clypeina jurassica.

Aspromonte unit
The Aspromonte Unit (AU) lithotypes crop out only in the southwestern part of the map along the right bank of the Cortaglia river, along which an already active deep-seated strike-slip fault system, occurs (Apollaro et al., 2019) (Appendix 1). The lithotypes consist of migmatitic paragneisses (Figure 7(a,b)) intruded by  Late-Variscan small-sized plutonites (Figure 7(c,d)), represented by syn-to post-tectonic magmatic bodies compositionally varying from monzogranites to finegrained leucogranodiorites. These lasts are interpreted as different from the adjacent southern termination of the Serre Massif main plutonic body, principally, in view of the different host rocks, namely migmatitic paragneiss to the south of the Cortaglia alignment and phyllites just crossing the strike-slip system to the north) (Figure 6(d)).
The Cortaglia River tectonic alignment has an ENE-WSW orientation, and is evidenced by the presence of strongly tectonized areas, characterized by unconsolidated ultracataclasites from granitoid parent rock (Figure 7(e,e ′ )).
The differences between the rocks to the north and to the south of this tectonic alignment are highlighted by the occurrence, to the south, of mylonitic leucocratic orthogneisses characterized by a total absence of recovery processes (Figure 7(f,f ′ )), very different from the mylonitic rocks of the MPC rocks, strongly recovered by the temperature increase due to the late-Variscan plutonic body emplacement. This last evidence highlights as the development of the mylonitic fabric in the AU rock types is due to the late-Alpine overprint mainly preserved in the central-eastern part of the Aspromonte Massif (Bonardi et al., 1984;Cirrincione et al., 2008Cirrincione et al., , 2015Cirrincione et al., , 2017Fazio et al., 2015b;2018;Heymes et al., 2010;Ortolano et al., 2005;Pezzino et al., 1990;2008;Platt & Compagnoni, 1990).

Stilo-Capo d'Orlando formation
During the Apennine phase of the Alpine orogenesis, the Mesozoic sedimentary succession of the SPC was partly covered by the late Oligoceneearly Miocene syn-orogenic deposition of the Stilo-Capo d'Orlando Formation. This formation consists of conglomerates produced by the action of flow of debris or masses (debris flow or mass flow) along submarine paleocanyons, of clays with silty intercalations, frequently engraved by channeled conglomerates, corresponding to slope deposits and from thick turbidite arenaceous layers (Bonardi et al., 2003). This rests directly on the crystalline basement and on the Mesozoic carbonate sedimentary succession, cropping out extensively along the eastern margin of the map.

Antisicilide Unit
The Antisicilide Unit lies, in tectonic contact, on the Stilo Capo d'Orlando formation (Gioiosa Ionica and Antonimina areas) and, locally, on the crystalline basement. The provenance and type of emplacement of the Antisicilide Unit are widely debated by numerous authors, results interposed between the Capo d'Orlando flysch and the Middle -Upper Miocene terrigenous succession. The Unit is dated Upper Cretaceous -Lower Miocene and is made up of variable lithologies grouped into: greenish-reddish pelites with a scaly texture, often in a chaotic position, intensely affected by shear phenomena.

San Pier Niceto Formation
It is a succession of Serravallian-Tortonian age, composed of different lithofacies characterized by frequent lateral-vertical variations. It is mainly constituted by a siliciclastic lithofacies consisting of homogeneous banks of coarse fossiliferous sands with Clypeaster sp. The sandstones locally contain conglomerates and have sedimentary structures of the turbidite type.

Basal limestones
The unit is made up of white-yellow vacuolar limestones and strata of stratified marly limestone, of metric thickness, with pelitic intercalations of centimeter thickness (Critelli et al., 2016). Sometimes there are intercalations of gypsumarenites and gypsumsylthites with centimetric lamination. The limestones, of Messinian age, are organized in massive banks, slightly slow, of plurimetric thickness intercalations of clayey marl, sometimes laminated of centimeter.

Mount Canolo Formation
The Messinian age Monte Canolo Formation is composed, starting from the base, by sandy levels, subordinately gravelly, from moderately thickened to very thickened, of brown color; the layers have medium thickness, sometimes with lenticular geometries, generally supporting a sandy matrix, and conglomerates. They are polygenic and heterometric, from sub-angular to angular, subordinately sub-rounded, slightly to moderately cemented; the rounded clasts are made up of granite and gneiss, differently the more angular clasts derive from micaschists and phyllites (Critelli et al., 2016a(Critelli et al., , 2016b.

Calcarenites and Trubi
At the base of the formation there are generally calcareous-marly rhythms; this rhythmicity is referable to the Milankovitch cycles which give to the formation, a characteristic stratification with alternating gray and whitish levels of marls and very rich in calcareous plankton marly limestones (Zanclean-Piacenzian). This formation is well exposed to the south of the Fiumara Torbido. The position of this formation is generally paraconcordant on the Trubi Formation; however, the contact between the two stratigraphic units is locally erosive (Critelli et al., 2016a).

Discussion
This work synthetized two field surveys made during the PhD thesis of Angì (2008) and the field activities within the Geological and Geothematic Italian Cartohography Project (CARG) with the realization of the Sheet N°590 (Polino et al., 2015).
Results confirm that the Serre Massif differs considerably from the adjacent Aspromonte-Peloritani orogenic system, in view of the different tectonic structure (Appendix 1 -Geological framework) and the absence of any Alpine metamorphic overprint. This is testified, for instance, by the different recognized mylonitic fabric where: (a) Aspromonte Unit mylonites, linked to the compressive late-Alpine mylonitic event built-up the Aspromonte Massif nappe-like edifice, are characterized by scanty recrystallized ribbon-like quartz levels ( Figures SM3b ′ ; b ′′ ) ; (b) Serre Massif mylonites, linked with the late-Variscan strike-slip deformation subsequently interested by late-to post-kinematic granitoid emplacement, are instead characterized by strongly recovered ribbon-like quartz levels ( Figure SM3a ′ ; a ′′ ) .
This late-Variscan retrograde mylonitic phase, better recognized in the MPC rather than in the SPC was here subdivided into an early extensional retrograde stage, mostly visible at the thin section scale (SM2), followed by a transpressional stage, which probably triggered the initial plutonic body intrusion.
This hypothesis is also supported by recent studies on the Serre Massif batholite construction characterized by an overaccretion mechanism (Fiannacca et al., 2017), rather than a dominant extensional uplift controlled by a core complexing model exhumation (Festa et al., 2013), as testified by the clear granitoid deformation microstructures from submagmatic to low-temperature sub-solidus conditions, characterized by an internal granitoid fabric consistent with a shortening axis roughly oriented NW-SE, constrained by Anisotropy of magnetic susceptibility (AMS) study (Fiannacca et al., 2021). The NW-SE shortening axis observed in the granitoid bodies can be strictly correlated with the attitudes orientation pattern of the mylonitic field foliation (S 3 ) which maintains a distribution of poles to planes consistent with a folding system characterized by a sub-horizontal or less inclined axis, oriented from NE-SW to ENE-WSW and by stretching-lineation L 3 characterized by a main ENE-WSW trend (Figure 4(a,b)) (Appendix 2); structures constantly consistent with the activity of a dextral type strike-slip tectonics, which can be ascribed to the late-D 3 transpressional stage and in line with the palinspastic reconstruction of the EVSZ activity (Figure 1(a)).
In this new tectonic framework the Serre Massif can be considered as belonged to the same geodynamic realm scattered throughout the Alps, the Corsica-Sardinia-Maures-Tanneron Massif, and the Northern Apennines, until late-Carboniferous time (Figure 1 (a)), where, during the interval from 330 to 300 Ma, the activity of the EVSZ affected all these massifs, locally triggering the emplacement of the late-Variscan granitoids, playing a key role in the evolution of the subsequent Alpine-Apennine cycle, acting as a pre-existing tectonic barrier (Carosi et al., 2020).
More in particular, the upper crustal levels of the Serre Massif geological evolution can be subdivided into an orogenic metamorphic cycle where the first deformational stage (D 1 ) is associated with the development of a penetrative and pervasive surface (S 1 ), more evident in the SPC rather than in the MPC rocks where it is preserved as relict isoclinal fold hinges within mylonitic foliation (Figure 3(f); Figure 6(a); Figure 8). D 1 is followed by a D 2 crenulation stage, better observable in the SPC rocks ( Figure 6(b); Figure 8). These two prograde stages, consistent with the eo-Variscan crustal thickening phase, were followed by an early-retrograde extensional mylonitic stage (early-D 3 ), linked with the collapse of the orogen and a consequent crustal thinning stage, which brought also to the detachment of the more surficial levels of the original crustal section sequence (i.e. SPC) from the more high-grade MPC. This former extensional tectonic detachment was followed, in turn, by the mostly preserved transpressional stage, with the formation of an extensively pervasive mylonitic foliation (Figure 3(a-e); Figure  8). This last event triggers pluton intrusion which, in its former emplacement stage, was involved in the same stress field of the late-D 3 mylonitic stage, as suggested by the occurrence of late-tectonic dykes characterized by clear evidence of supra-solidus deformative structures (Figure 3(h,h ′ )) and confirmed by the same regional shortening axis consistent with the dextral shear-sense tectonics both in the basement rocks and in the granitoids. Finally, the late-Variscan plutonic emplacement continued with post-tectonic intrusion of paraconcordant (Figure 3 (h)) to discordant dykes (Figure 3(i)), characterized by sharp contacts and devoid of any evidence of supra-or sub-solidus deformations.

Conclusion
The new geological map of the southern Serre Massif is a useful contribution to the geodynamic reconstruction of the late-Paleozoic scenario of the southern European Variscan belt: it permits to delineate the sequence of the Variscan metamorphic evolution, where, after a prograde multistage metamorphism, follow a pervasive retrograde evolution, controlled by an initial extensional mylonitic stage, linked with the initial collapsing of the orogen, replaced by a transpressional mylonitic stage, which triggered the intrusion of the former plutonic products under the same stress field of the mylonitic event. Mylonites were finally sutured by the late-to post-kinematic granitoid intrusion, producing quasistatic overprints with the recovery of the mylonitic fabric, before being exhumed, for the first time, at the end of the Palaezoic with the 'Verrucano' sedimentation, before to be covered by the Mesozoic carbonate platform sedimentation, and definitively exhumed at the end of the Oligocene with the unrooting from its original Variscan basement crust contemporaneously to the deposition of the syn-orogenic Stilo Capo d'Orlando formation and the backthrusting of the Antisicilide unit.

Software
The geological-structural map of the Serre Massif upper crust was mainly designed by means of the ArcGIS ® software. In fact, thanks to its functionalities of data managing and storing, ArcGIS ® allowed the map digitization and the database structuring to be properly accomplished.
Taking advantage of specific ArcGIS ® toolboxes, such as 'Hillshade' and 'Contour', the extrapolation of useful topographical features from DTM was performed. Moreover, thanks to a new ArcGIS-based Python-toolbox (i.e. ArcStereoNet -Ortolano et al., 2021), the collected structural data have been studied with statistical analysis techniques and then plotted within lower-hemisphere equal-area stereonets. The statistical algorithms applied to data include density contour functions, clustering, and mean vectors extraction, together with the classic cluster and girdle analysis techniques (e.g. M.E.A.D. + Fisher and Bingham algorithmssee Ortolano et al., 2021 for details).
Since it operates within the ArcGIS ® environment, ArcStereoNet merges its data analysis and plotting functionalities with the classic GIS features, including various data selection tools. In this view, the Graph To Hyperlink tool (included within the Arc-StereoNet toolbox), which allows connecting via hyperlink the results of statistical analysis with the geographic location of the selected structural data, was used to extract and display the mean field foliations and the stretching lineations along the entire map (Appendix 2). Firstly, the structural data were manually grouped based on their geographic location. Consequently, the mean azimuth/dip values were extracted for each group and displayed at the corresponding centroid coordinates of the group. Finally, only the statistically consistent main foliation average values were maintained (i.e. those extracted from a number of data greater than 20 units).
The final editing and assemblage of map, geological sections, stereoplots, legends, and any other graphical element were accomplished by means of the GIMP software.

Data
The supplementary materials include a detailed description of the petrographical and geomorphological features of the over 120 samples from the mapped area and three explanatory figures.

Data availability statement
The data that support the findings of this study are openly available in 'Figshare' at http://doi.org/10.6084/m9. figshare.14601396.

Disclosure statement
No potential conflict of interest was reported by the author(s).