Displays

The Western Mediterranean-Alpine belt is remarkable for its tectonic complexity, i.e. strong arcuation of plate boundaries, fast trench retreat, upper-plate extension and switch of subduction/collision polarity around the Adriatic plate (Adria). The kinematic evolution of the Western Mediterranean area is enigmatic due to the intermittently motion of small continental plates (Adria, Iberia and Sardinia-Corsica) that are caught between two major plates (Africa and Europe), converging since Cretaceous time. Reconstructing the past motion of these micro-plates is challenging due to the strong deformation of their boundaries but is key to understand the geodynamic evolution of the whole area.

The Neogene tectonic evolution is well constrained using magnetic anomalies and transform zones in the Atlantic Ocean for the motion of Europe, Iberia and Africa, and by reconstructing the amount of convergence along fold-and-thrust belts (Apennines, Alps, Dinarides, Provence) and coeval divergence along extensional basins (Liguro-Provencal and Tyrrhenian basins, Sicily Channel Rift Zone) for the motion of Adria and Sardinia-Corsica. Those reconstructions show that Adria had a slight independent motion from Africa and rotated counter-clockwise of about 5º relative to Europe since 20 Ma. However, uncertainties increase and debates arise as one goes back in time. The main debates concern the past motion of Iberia and where its motion relative to Europe is being accommodated in Mesozoic time. Different kinematic scenarios have been proposed depending on the interpretation of paleomagnetic dataset of Iberia, magnetic anomalies in the North Atlantic, and geological-geophysical record of deformation in the Pyrenees and between Iberia and Sardinia-Corsica. Those scenarios have different implications for the tectonic evolution of the Apennines, especially for the Permian-Triassic paleo-tectonic setting of Sardinia, Calabria and Adria, and for the extent and timing of closure of the Liguro-Piemont Ocean. It is important to discuss those implications to better understand subduction processes in the Apennines and their driving forces.

How to cite: Le Breton, E.: Kinematic reconstructions of the Western Mediterranean area since Triassic time: possible scenarios and their implications for the Apennines, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11301, https://doi.org/10.5194/egusphere-egu2020-11301, 2020.

The Apennine magmatism from Early Permian to present may be considered as the result of a Wilson cycle. Here, the main stages of this magmatic activity will be reviewed from a mantle source perspective in the framework of the Alpine-Apennine system.  The oldest magmatic event is represented by gabbro-derived granulites of Late Variscan age, now occurring as blocks in Late Cretaceous orogenic melanges. Their protholiths  were recognized as deep crustal cumulates derived from MOR-type tholeiitic liquids. This event may be related to the extensive magmatic underplating affecting SW Europe in conjuction with lithospheric thinning and orogenic collapse of the Variscan belt. The subsequent Mesozoic continental rifting preceding the opening of the Jurassic  Ligurian Tethys was mostly amagmatic. Nevertheless, widespread evidence of melt migration in the ascending lithosphere during passive asthenospheric upwelling is testified in the exhumed mantle bodies from the Northern Apennine ophiolites. Mantle rocks showing a considerable geochemical and isotope heterogeneity were a dominant component of the Ligurian Tethys oceanic lithosphere. In contrast, the short-lived magmatism of the Ligurian Tethys (ca. 160-165 Ma) was characterized by uniform N-MORB signatures, both in marginal  and oceanward domains of the basin, which were related to embryonic and slow-spreading ridge type oceanic lithosphere, respectively. The Nd-Hf isotopic contrast between magmatic products and associated mantle rocks (Rampone et al., 1998; Mc Carthy et al., 2015; Barry et al., 2017; this work) is a debated issue,  which could reflect the occurrence of inherited subcontinental mantle or ancient depleted domains in the convecting upper mantle. The subduction initiation in the Northern Apennine was not related to igneous activity. No record  of island-arc magmatism linked  to the Alpine east-dipping subduction stage has been recognized, possibly due to dry, mantle-dominated, subducted lithosphere (Mc Carthy et al., 2018). On the other hand, the collisional calc-alkaline magmatism coheval with the west-dipping Apennine subduction system was found only as clasts in sediments from the nascent orogen (Aveto-Petrignacola Formation). Ancient modifications of mantle sources, possibly related to the previous subduction event, have been proposed for the origin of this magmatism (Mattioli et al., 2012). The imprint of Apennine subduction on mantle sources is strikingly attested by the recent volcanism (< 5 Ma), which includes the unique magmatic associations from Tuscany and Roman provinces. Here, leucite-free (lamproites, shoshonites) and leucite-bearing (kamafugite, leucitite, plagioleucitite) K-rich magmas, were erupted in the former domains, and locally hybridized with anatectic melts. Mantle melting was triggered by post-orogenic extension following the eastward migration of the Adriatic slab. Mantle source modification through recycling of different sedimentary lithologies from the subducted slab may explain the extreme incompatible trace element enrichments and Sr-Pb-Nd-Hf isotopic signatures of the ultrapotassic magmas, coupled with their subduction-related geochemical affinity (Conticelli et al., 2015).  

References

Barry et al., 2017. Sci. Reports 7, 1870 

Conticelli et al., 2015. Lithos 232, 174–196

Mattioli et al., 2012. Lithos 134-135, 201–220.

Mc Carthy and Muntener,  2015. Geology 43, 255–258

Mc Carthy et al., 2018. Geology 46, 1059–1062

Rampone et al., 1998. Earth Planet. Sci. Lett. 163, 175–189

How to cite: Montanini, A.: Magmatism and mantle evolution in the Northern Apennines: a tale of rifting, oceanization and subduction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5328, https://doi.org/10.5194/egusphere-egu2020-5328, 2020.

The Oligocene-Miocene evolution of the westernmost part of the Northern Apennines was constrained firstly by Oligocene E-W regional sinistral shearing and then by Early Miocene shortening and Middle to Late Miocene NW-SE dextral transpression affecting the southern termination of the Western Alps arc (Maritime and Ligurian Alps) and the substrate of the Tertiary Piemonte Basin (TPB), which started to be incorporated, in the same time span, in the Northern Apennines belt

In other words, the dynamics accommodating the different motion of the WNW-directed Adria and SW Alps with respect to the ENE-directed Ligurian-Corso-Sardinian block also controlled the evolution of TPB and its Ligurian substrate since at least the Aquitanian, when a regional conterclockwise rotation began and a deep reshaping of the basin occurred, due to predominant NE-SW shortening concomitant with the Northern Apennines thrust fronts propagation (Burdigalian). On the other side, the infilling of the SW Alps foreland basin was partially controlled also by the resedimentation of non-metamorphic Cretaceous-Paleocene Ligurian units previously deposited along the Briançonnais-Dauphinois continental margin. The subsequent Late Burdigalian to Serravallian extension in the internal side of the SW Alps allowed the creation of accomodation space and the deposition of relevant thickness of sediments in the TPB, during the coeval progressive uplifting of Alpine crystalline and metamorphic units (e.g. the Argentera Massif and Dora-Maira Unit). This Alpine process constrained the shape and evolution of the TPB syn-orogenic sub-basins and their subsequent tectonic paths within the NW Apennines belt, while it was being built. The steps of this Alps-Apennines evolution have been clearly recorded by a set of regional scale, Oligocene to Pleistocene unconformities that can be continuously traced at surface in the southern part of the Piemonte region and in the subsurface of the western Po plain.

We thus remark that the evolution of the westernmost part of the Apennines can be studied largely referring to the Alpine geodynamics, since, although the Alps and the Apennines are two distinct geomorphologic and geophysical entities at the scale of the Western Mediterranean area, they share common synorogenic basins and consistent kinematic evolution in their junction zone of NW Italy.

How to cite: Barale, L., Fabrizio, P., Carlo, B., Anna, D., Andrea, I., and Luca, M.: Oligocene-Miocene tectonics of the SW Alps and western Apennines coupled orogenic belts, as recorded by their internal and external syn-orogenic basins, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17862, https://doi.org/10.5194/egusphere-egu2020-17862, 2020.

We present preliminary results of a structural analysis and 3D modelling project carried out along a transect in the Santerno Valley, between Firenzuola (Tuscany) and the outskirts of Imola. The aim of the project is to combine surface geological and structural data (available thanks to the national geological mapping CARG project and original surveys), with the available subsurface data (2D seismics and a few wells), and obtain a comprehensive 3D framework for deformation in this key area of the Northern Apennines. In addition, by combining geodetic, seismicity and interferometric data with the 3D structural model, we are able to obtain a better picture of the active structures in the area.

Our analysis shows that the studied transect is at the northern periclinal hinge of a regional anticline/window where the Marnoso-Arenacea Formation crops out and is crosscut by several regional-scale thrusts. Subsurface data suggest that these relatively shallow thrusts are rooted at the top of Mesozoic carbonates, that do not crop out in the area. Different balancing algorithms confirm a relevant along-strike variation of slip along these thrusts, that reduce their offset towards the periclinal hinge to the west.

In the more external part of the transect, towards the lower hills and the plain around Imola, a regional-scale pop-up, evidenced by the late-Messinian unconformity, is the main feature in subsurface datasets. This structure is rooted at the base of Mesozoic carbonates and is characterized by large and continuous ramps that can be considered candidates for recent earthquakes in the area.

How to cite: Lorenzo, G., Andrea, B., and Fabrizio, S.: Structural analysis and 3D geological modelling of the Santerno transect in the Northern Apennines (Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22549, https://doi.org/10.5194/egusphere-egu2020-22549, 2020.

Exhumation of subducted high-pressure units is favoured by relatively narrow, high-strain shear zones, where most metamorphic and deformational processes occur. Unfortunately, these are commonly overprinted and/or partly or fully obliterated along the exhumation path by younger fabrics or by metamorphic re-equilibration. Their identification and characterization are, therefore, of primary importance when aiming at reconstructing the deepest (and thus earliest) tectonometamorphic history of high-pressure crustal units.

The Northern Apennines (Italy) offer the opportunity to study a unique setting where continental units (Tuscan Metamorphic Units) were subducted to high-pressure conditions and then exhumed and juxtaposed against non-metamorphic units (Tuscan Nappe). We have studied a well exposed section in the Monticiano-Roccastrada Unit of the Mid Tuscan Ridge (MTR), where a mesoscopic (~20 m length and 5 m high) compressional duplex deforms the Palaeozoic-Triassic quartz-rich metasandstones, metaconglomerates and minor metapelites of the Monte Quoio - Montagnola Senese Unit with a top-to-the-NE sense of shear (Arenarie di Poggio al Carpino Formation; Casini et al., 2007).

Our approach is based on detailed fieldwork, microstructural and petrological investigations. Field observations reveal severe strain partitioning within the duplex between metapelite levels, corresponding to 10-50 cm thick high-strain zones, and metasandstone levels, which form relatively strain-free metric horses. Early generations of quartz veins are highly transposed (sheath folds occur) parallel to the metapelitic high-strain shear zones. Veins are composed of iso-oriented quartz, forming up to several centimetre long single-grain ribbons, Mg-carpholite (XMg~ 0.65) needles and K-white mica marking the stretching lineation. Carpholite in the transposed veins invariably defines the stretching direction of shear zones. These high-P veins coexist with a later generation of less deformed, oblique quartz veins. The mylonitic foliation in the metapelites is defined by quartz, chloritoid, pyrophyllite and K-white mica forming a stretching lineation coherent with the one visible in the veins. Geometrical, cross-cutting and petrographic relations suggest that there has occurred cyclic deformation between brittle and viscous conditions, with the veins forming broadly syn-mylonitic shearing. Thermodynamic modeling results suggest >0.8 GPa and ~350°C for the formation of both the high-pressure veins and the mylonitic foliation.

Shear zones were subsequently folded about the NNW-SSE axis of the regional antiform associated with the MTR. Later brittle overprinting is represented by quart-filled tension gashes and localized C’ planes, mostly within the more competent metasandstone levels, indicating top-to-the-SW reactivation. In summary, our results suggest a cyclic brittle-ductile behaviour occurring at high pressure conditions. This could potentially reflect the repeated alternation between aseismic creep (viscous) and coseismic slip (brittle) during the first stages of the exhumation history of this portion of the northern Apennines, from lower to middle crustal levels in a compressional top-to-the-NE setting. Dating of K-white mica is ongoing to constrain the geodynamic scenario of such shear zone.

Casini, G., Decandia, F.A., Tavarnelli, E., 2007. Analysis of a mesoscopic duplex in SW Tuscany, Italy: implications for thrust system development during positive tectonic inversion. Geol. Soc. London, Spec. Publ. 272, 437–446.

How to cite: Giuntoli, F. and Viola, G.: Cyclic brittle-ductile behaviour recorded in exhuming high-pressure continental units of the Northern Apennines., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6923, https://doi.org/10.5194/egusphere-egu2020-6923, 2020.

The northern Tyrrhenian Sea and the inner northern Apennines (NA) are classically regarded as a late Miocene–Pleistocene back-arc system characterized by crustal extension and acidic magmatism coeval with shortening farther east at the front of the belt. The orogenic prism of the NA, which is well exposed in the easternmost Island of Elba, formed by eastward thrusting, stacking and folding of oceanic and continental units from the Eocene down to the late Miocene. Eastern Elba hosts the historically and economically most important Fe district of Italy, which, in the study area, consists of sulphide- and Fe-rich veins and breccias, in addition to minor massive Fe ore bodies of hydrothermal origin emplaced in actively deforming upper crustal conditions (Mazzarini et al., JSG, 2019). The Zuccale fault (ZF) on Elba is generally interpreted as a major normal fault, which would have greatly facilitated regional E-W extension during the late Miocene. It is an east-dipping low angle fault that displaces the nappe pile by up to 6 km. The fault architecture is complex, although it can be approximated by an exclusively brittle, flat-lying component dated to < c. 5 Ma by K-Ar on illite from fault gouge that cuts through steeper, brittle-ductile and earlier top-to-the E thrust related fabrics (Viola et al., Tectonics, 2018).

Aiming at directly constraining the syn- to post Pliocene evolution of the ZF and the age of the hydrothermal Fe deposits of the historic mining district, we performed hematite (U-Th)/He dating of the low-angle, hematite-decorated principal slip surface of the ZF at the famous Terra Nera section. Hematite samples examined in this study comprise platelet-shaped crystals (specularite), fine aggregates coating fault slip surfaces, massive veins, the fine matrix of breccias, and euhedral millimetric crystals from low strain domains. Ages from the ZF striated fault plane span the ~4.2±0.4 to 3.6±0.4 Ma time interval, fully consistent with available fault gouge illite K-Ar dates. Later NNE-SSW strike-slip faulting, associated with centimetric specularite veins, is constrained to between 2.1±0.2 and 1.7±0.2 Ma, roughly coeval with transient and local reactivation of the ZF as indicated by 1.9±0.2-1.5±0.2 Ma old euhedral, millimetric hematite infilling dilational jogs within the foliated ZF fault zone. Farther north, in the Rio Albano area, mineralised hematite breccias genetically associated with top-to-the E spectacular extensional faults are dated to between 1.6±0.2 and 0.9±0.1 Ma and postdate older ~2.7-2.6 Ma quartz-hematite veins associated with a discrete phase of top-to-the W shearing.

All obtained dates fit our independently built structural model of the investigated area, where clear crosscutting relationships and structural/metamorphic considerations have permitted establishing a sequence of kinematically constrained deformation events. For the first time we have defined the exact timing of deformation in the study area, contributing to the unravelling of the local, long and complex tectonic and mineralization history and to a better constrained regional picture.

How to cite: Viola, G., Derycke, A., Gautheron, C., Mazzarini, F., Musumeci, G., and Garofalo, P. S.: Hematite (U-Th)/He constraints on Plio-Pleistocene deformation and hydrothermalism in the eastern Island of Elba, northern Apennines (Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3258, https://doi.org/10.5194/egusphere-egu2020-3258, 2020.

In extensional tectonic settings, stretched terrains are often associated to lithosphere partial melting and widespread magmatism with plutons emplaced in the thinned crust. Emplacement of felsic magmas, at upper crustal levels, represents the final stage of the magma transfer from profound to shallow depth. In this framework, a mostly vertical permeability controls the magma uprising migration, as induced by dominant transcurrent crustal structures. Nevertheless, the interplay between extension and prolonged heat transfer favors uplift and progressive exhumation of the magmatic bodies, during their cooling.

In this presentation, we show an example of a felsic magmatic intrusion, the Porto Azzurro pluton (inner northern Apennines), emplaced in an extensional tectonic setting and mainly controlled by a regional transfer zone related to the opening of the Tyrrhenian Basin. This is exposed in the eastern Elba Island (Tuscan Archipelago). The hosting rocks of the Porto Azzurro pluton are mainly represented by micaschist, paragneiss and quartzite, affected by contact metamorphism and intense fluid circulation. We have analysed the structures that assisted the pluton emplacement and the ones that deformed the pluton itself during its cooling, from melt-present to brittle conditions, based on the integration among fieldwork, micro-structural, petrological and EBSD analyses. Furthermore, new U/Pb geochronological data on zircons and (U-Th)/He on apatite fission track refined the age of the pluton emplacement and its cooling, adding new data about the pluton history. Existing petrological analyses of the hosting rocks allowed us to better constrain the time-evolution of the thermal perturbation, permitting to frame the deformation and exhumation history of the Porto Azzurro monzogranite in the context of the Neogene extensional tectonics affecting the inner Northern Apennines.

How to cite: Brogi, A., Spiess, R., Caggianelli, A., Langone, A., Stuart, F., Zucchi, M., Bianco, C., and Liotta, D.: The cooling, deformation and exhumation history of the late Miocene syn-tectonic Porto Azzurro pluton in a regional transfer zone (Elba Island, Italy) , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5987, https://doi.org/10.5194/egusphere-egu2020-5987, 2020.

The complex processes affecting the Tyrrhenian-Apennine System are inevitably reflected in Sicily, here considered as an independent plate starting from 5 Ma and located between Europe and Africa plates and Calabria microplate.

In particular the retreat of the Adriatic-Ionian slab and its fragmentation involve Sicily in a process of escape towards east-southeast due to the space that the slab is creating. At the same time Africa acts as an intender during its convergence with the European plate.

We show here the preliminary results of a study that aims to reconstruct the kinematic evolution of Sicily and its role in the framework of the Tyrrhenian-Apennine System.

First of all we found the margins of the plate, searching for lithospheric structures that can be considered as plate boundaries, using different types of data (high resolution bathymetric maps, seismic sections, geodetic data, focal mechanism of recent earthquakes, gravimetric maps, lithosphere thickness maps…) together with the literature.

The margins are:

-The Sicily Channel, characterized by a series of pull-apart basins related to a dextral trascurrent zone (Sicily-Africa margin);

-The Malta escarpment and the Taormina Line characterized by transpression (Sicily-Calabria margin);

-The Drepano-Ustica seamount also characterized by transpression (Sicily Europe margin).

Starting from the structures in the Sicily Channel, we found the Euler pole of rotation between Sicily and Africa using the GPlates software. Thanks to the software we were able to find also Sicily-Europe and Sicily-Calabria poles and the velocity vectors.

Finally, we compared the Euler poles and the velocity vectors with the geological data, trying the best fit of the two and better refine the model.

Key Words: Sicily microplate, Sicily Channel, Malta Escarpment, Tyrrhenian-Apennine System.

How to cite: Penza, G., Macchiavelli, C., Pierantoni, P. P., and Turco, E.: Eastward Tectonic Escape of Sicily Microplate: preliminary results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9351, https://doi.org/10.5194/egusphere-egu2020-9351, 2020.

The Africa Europe collision, which produces the formation of the Alpine arc, in the Mediterranean area is accompanied by passive subduction processes, resulting from the sinking of the remnant Alpine Tethys and the Ionian lithosphere, and from the fragmentation of the Adriatic plate. In this complex deformation, back-arc basins (Alboran, Balearic, Tyrrhenian and Hellenic) and circum - Mediterranean mountain ranges are formed.

In this work we focus our attention on the opening of the Tyrrhenian basin and the contemporary formation of the Apennine chain.

In order to describe the evolution of the geodynamic processes that guided the formation of the Tyrrhenian basin and the Apennine chain we used the plate kinematics technique. Through careful observation of the regional structures we have divided the area of the Apennine Chain and the Tyrrhenian basin into polygons (crustal blocks or microplates) distinguished on the basis of the direction of the Tyrrhenian extension. The boundary between the polygons has been placed coinciding with the large structures that characterize the Tyrrhenian-Apennine area. The rotation poles of the individual polygons, in the frame of reference of the Sardo-Corso block, are based on the Tyrrhenian extension directions that characterize them. The velocity ratio between the polygons was determined by the slip vector of the structure (plate boundary) that separates them. To determine the rotation time of the polygons we used the stratigraphic records of the syn-rift sequences, while the rotation angle of the polygons is obtained comparing the crustal balance with the speed ratios.

Finally, the kinematic framework obtained, included in the global rotation model, allowed us to reconstruct the tectonic evolution of the central Mediterranean during the opening of the Tyrrhenian basin.

Key Words: Tyrrhenian-Apennine System, Non-rigid plate kinematics.

How to cite: Turco, E., Macchiavelli, C., Pierantoni, P. P., Penza, G., and Schettino, A.: The opening of the Tyrrhenian basin and the Apennine chain formation in the kinematic context of Africa - Europe collision, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9727, https://doi.org/10.5194/egusphere-egu2020-9727, 2020.

Fore-arc basins form structurally in response to a variety of subduction zone processes. The sedimentary infill records the tectono-stratigraphic evolution of the basin, and thus, provides information on the dynamic of the fore-arc region. Using seismic reflection profiles and bathymetric data, we analysed the stratigraphy and tectonics of the Paola Basin, deciphering the tectono-sedimentary mechanisms that acted in the forearc of the Tyrrhenian‐Ionian subduction system during the Plio-Quaternary. The Paola Basin is a NNW-SSE trending syncline, bounded by the Coastal Chain to the east and a regional-scale anticline, here called Paola Anticline, to the west. There are no major normal faults bordering the basin. It hosts up to 5.2 km thick Plio-Quaternary deposits, most of them supplied from Apenninic/Sila entry points and transported by longshore currents. The total subsidence reaches the value of ∼5 km. The sedimentary load varies from 60% to 75% of the total subsidence. The Pliocene to Lower Pleistocene sedimentary infill of the syncline displays a strata growth geometry consistent with a continuous rotation of the eastern limb of the Paola Anticline. Crustal folding is the mechanism that better explains the lack of significant normal faults bordering the Paola Basin, its tectonic subsidence and the uplift of the Paola Anticline. During the Late Pliocene - Early Pleistocene, contractional deformation continued, and also strike-slip movements affected both the Paola Anticline and the eastern sector of the basin. This resulted in the growth of the central sector of the Coastal Chain, leading to the definition of the Paola and Crati basins, previously connected in a larger proto basin. Also, strike-slip faults with associated releasing and restraining bends formed in the hinge zone of the Paola Anticline. The bathymetric expression of the strike-slip zone consists of structural highs and depressions that overall form the Paola Ridge. The development of strike-slip tectonics is associated to the trench-parallel component of the upper plate motion occurring in the oblique subduction setting. The growth of the Paola Anticline and Paola Basin was coeval with the opening of the Vavilov and Marsili back arc basins. Thus, extensional and contractional tectonics spatially coexisted along sectors of the upper plate of the Tyrrhenian-Ionian subduction system from Early Pliocene to Early Pleistocene. Since the Middle Pleistocene, the growth of the Paola Anticline and Paola Basin came to an end, and extensional tectonics controlled the evolution of the forearc region.

How to cite: Corradino, M., Pepe, F., Bertotti, G., Picotti, V., Monaco, C., and Nicolich, R.: 3D Architecture and Plio-Quaternary evolution of the Paola Basin: Insights into the Forearc of the Tyrrhenian-Ionian Subduction System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19985, https://doi.org/10.5194/egusphere-egu2020-19985, 2020.

The southern Apennines are a fold-and-thrust belt formed since the lower Miocene until the middle Pleistocene (e.g., Vitale and Ciarcia, 2013). Although a wide literature exists about the geology of this orogenic chain, few are the studies about the kinematics of the major thrusts. With this in mind, this work is aimed to investigate the out-of-sequence regional thrust system exposed in the Campania region. This system is characterized by a frontal ramp exposed along the N-NE side of the platform carbonate ridge forming the regional mountain backbone. The main structure is also exposed as a flat thrust in the Campagna and Giffoni tectonic windows located in the internal sector of the chain. We analyzed several outcrops; in some of them, we observed the Mesozoic carbonates superposed onto the upper Miocene wedge-top basin deposits of the Castelvetere Group. The kinematic analysis of major and minor structures suggests the occurrence of two thrust fault sets: (i) the oldest indicates an eastward tectonic vergence, whereas (ii) the youngest, and more developed, toward the north. In the external zones, the N-S shortening was synchronous with the deposition of the upper Messinian-lowermost Pliocene Altavilla Fm. The origin of this out-of-sequence regional deformation is still matter of debate (e.g., Vitale et al., 2017). In our opinion it was the shallow expression of a deep-seated thrusting episode within the buried Apulian slab. It was dominated by thrust ramps (thick-skinned tectonics) mainly verging to East, and by the N-verging structures associated to lateral ramps.

References

Vitale Stefano and Ciarcia Sabatino (2013) - Tectono-stratigraphic and kinematic evolution of the southern Apennines/Calabria-Peloritani Terrane system (Italy). Tectonophysics, 583, 164–182.

Vitale Stefano, Tramparulo Francesco d'Assisi, Ciarcia Sabatino, Amore F. Ornella, Prinzi Ernesto Paolo and Laiena Fabio (2017) - The northward tectonic transport in the southern Apennines: examples from the Capri Island and western Sorrento Peninsula (Italy). International Journal of Earth Sciences (Geologische Rundschau), 106, 97–113.

How to cite: Ciarcia, S., Prinzi, E. P., Tramparulo, F. D., and Vitale, S.: The upper Messinian-lowermost Pliocene out-of-sequence event in the southern Apennines (Italy): a study about the kinematics of the major thrust faults, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5266, https://doi.org/10.5194/egusphere-egu2020-5266, 2020.

The geodynamic reconstructions of the Apennine-Tyrrhenian system strongly rely on chronological and P-T data derived from the study of ophiolite-bearing units accreted in orogenic belts, frequently affected by HP-LT metamorphic overprint. Consequently, we carried out a detailed geological survey, combined with the study of calcareous nannofossils and the analysis of mineralogical and petrographic features of low-grade metamorphic rocks, in order to reconstruct the tectono-stratigraphic relationships among different formations of the Liguride Complex and perform a critical review of the existing literature on the P-T evolution of the Liguride accretionary wedge exposed in the Pollino area of the Southern Apennines.

A geological-structural survey allowed us to distinguish four major tectonic units, characterized by an overall decrease of metamorphic grade from top to bottom. The tectonic units consist of: i) slices of continental crust rocks consisting of Albitic gneisses, Garnet gneisses and Amphibolites; ii) the Frido Unit Auctorum p.p. with a variable intensity of deformation and HP/LT metamorphic grade. This unit consist of a typical ophiolitic assemblage, including serpentinites with metadoleretites or alterated peridotites, pillow lavas, foliated metabasites, metalimestones and metabreccias, quarzites, and jaspers. The upper part of the succession is made up of calcschists and low-grade metapelites, displaying variable PT conditions from about 7 kbar and 200 °C to 12 kbar and 350 °C. A wide variation of P-T conditions suggests that the Frido Unit consists of different thrust sheets, showing a progressive increase of the metamorphic grade moving from north to south;  iii) the Seluci-Cogliandrino Unit, consisting mainly of metapelites and slices of an upper Jurassic seafloor succession with pillow lavas;  iv) the non-metamorphic Nord Calabrian Unit represented, from the bottom, by ophiolites, shales with pencil cleavage (Crete Nere Formation) and by a prevailing calciclastic unit (Saraceno Formation), topped by thrust top deposits (Albidona Formation).

Calcareous nannofossil assemblages were studied in samples coming from the main successions of the investigated area, in order to provide age constraints for the deformation of the Liguride accretionary wedge. Results show that Frido Unit did not preserve calcareous nannofossils in all analyzed samples, because of the strong deformation produced during the HP-LT metamorphic overprint. In the upper part of the Seluci-Cogliandrino Unit, Eocene inf. CNE4 biozone has been documented. On the other hand, in the lower part of the Saraceno Fm a late Albian age (CC9 p.p.) was documented, based on the occurrence of Eiffellithus turriseiffelii and Hayesites irregularis. Moreover, the occurrence of Discoaster lodoensis, Reticulofenestra dictyoda and Toweius callosus framed the lower stratigraphic interval of the Albidona Fm to the early Eocene (Ypresian; CNE4 p.p.). Based on the above data, the current views on the Cretaceous-Paleogene geodinamic evolution of the southern Apennine thrust and fold belt should be substantially revised.

How to cite: Cavalcante, F., Catanzariti, R., and Prosser, G.: A critical revision of the Liguride complex in the Pollino area (Southern Apennines), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21568, https://doi.org/10.5194/egusphere-egu2020-21568, 2020.

Mylonites are common structural elements in basement complexes. There, strain localization within shear zones occurs at amphibolite to greenschist facieses. More rarely, it also takes place at low-grade to anchizonal conditions in the external portions of orogenic belts. In the present contribution, we document the large-scale architecture, micro-structure, and mineralogy of a prominent shear zone exposed along the southern flank of the Monte Alpi Unit, southern Apennines, Italy. Deformation localized within the Messinian sedimentary protolith topping the carbonates of the Apulian Platform, and in the lowermost tectonic units of the Apennine allochton. Integration of results achieved after field geological mapping, outcrop structural analyses, optical and SEM micropscopy, and X-Ray diffrattometry permits to assess the time-space evolution of the main deformation mechanisms in the aforementioned shear zone. The shear zone involved Messinian shale, sandstones and conglomerates originally deposited in a foreland basin system, and Mesozoic claystones, limestones, and marls that formed in deep basinal environments. Now days, the mylonitic foliation is sub-parallel to the tectonic contact between the Messinian sedimentary cover of the Apulian carbonates and the overlying allochton. Shear-related deformation produced a foliated mylonitic fabric dipping ca. 20° S, and a well-developed, east-trending stretching lineation defined by aligned quartz and/or calcite grains. The conglomeratic levels were boudinaged, and the individual elongated pebbles re-oriented along slip direction. The microstructure of mylonites is characterized by a fine-grained calcite matrix, which shows an intense foliation due to dark bands made up of oxides, organic matter, and minor phyllosilicates. X-ray diffraction data performed on the Messinian shales and Mesozoic claystones, indicate the presence of mixed layer illite/smectite with 80-90% of illite and R1/R3 ordering thus suggesting an high digenetic grade (temperature: 120-140 °C). The two analyzed lithologies mainly differ in the presence of kaolinite, which occurs in the more proximal Messinian facies. Altogether, outcrop-scale kinematic markers such as shear bands, rootles folds and asymmetric porphyroclasts show a consistent top-to-the-east shear sense. Mineralogical and microstructural data indicate that shearing took place at a depth of 6-7 km during the Early Pliocene emplacement of the Apennine allochton on the Apulian Platform, and then exhumed by Late Pliocene low-angle normal faulting, Lower Pleistocene transpression, and Middle-Pleistocene-Holocene high-angle extensional faulting. In summary, the eastward motion of the allochton produced intense and localized low-temperature shearing in sediments on top of the Apulian Platform and in the overlying allochton. A subsequent reactivation of this shear zones as low-angle normal fault during late Pliocene exhumation is envisioned.

How to cite: Prosser, G., Agosta, F., Giuffrida, A., Belviso, C., and Cavalcante, F.: Ductile shearing of Apennine allochtonous units and Messinian terrigenous deposits on top of the Inner Apulian Platform (Monte Alpi, Southern Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19622, https://doi.org/10.5194/egusphere-egu2020-19622, 2020.

In west-directed subduction zones, as the compression moves towards the foreland, the accretionary prism progressively expands to follow the hinge migration towards the east. Although late Miocene foreland propagation implies the shift of the thrust front, in the central Apennines, the effects of the Messinian compression can be observed on a much broader area, implying out-of-sequence thrusting in the rear.

In order to understand the Messinian involvement of the previously formed Tortonian belt-foredeep system, a regional reinterpretation is here provided. The analysis of publicly available 2D seismic reflection lines across the upper and middle Latin Valley and 10 wells enables the identification of two main seismostratigraphic units: i) the Meso-Cenozoic neritic carbonates and ii) the upper Tortonian siliciclastic pelitic and arenaceous turbiditic associations of the Frosinone Formation.

The most evident reflectors are the upper Cretaceous and upper Serravallian top paraconformities, which, due to tectonic repetition can be followed at different depths. We find that minor reflectors can be attributed to the several thrusts affecting folded Meso-Cenozoic neritic carbonates. This observation allows us, together with field and well evidences, to trace several thrust sheets characterized by a general top-to-the NE sense of shear. In a few sections from the Latin Valley (e.g. Line FR-309-80), we recognized the Meso-Cenozoic neritic carbonates being thrusted together with the Tortonian Frosinone Formation, on top of a laterally variably thick siliciclastic succession. This further syn-orogenic unit could be related to the early Messinian sandstones of the Torrice Formation, implying that out-of-sequence thrusting took place in the Latin Valley during the wedge-top sedimentation. The thin-skinned fold-and-thrust fabric is defined by en-échelon distributed thrusts, NNE- and ENE striking tear faults and minor pop-up structures often determining ideal traps for hydrocarbon and geothermal fluids. Finally, conjugated NW-striking high-angle normal faults crosscut the orogenic heritage and sets a horst and graben structure associated with continental deposition and the Volsci Volcanic Field.

The limited oil exploitation over the past century has targeted only the shallower siliciclastic traps and some evidences in the shallower neritic carbornate thrust sheets. At the light of our new interpretation, the deeper carbonate units could be a new focus for hydrocarbon accumulation and may furnish targets for geothermal and/or hydrocarbon research in the area. Future work aims at quantify the Tortonian and Messinian amount of shortening by taking into consideration the adjoining Volsci Range. Finally, our findings bear implications on geodynamic reconstructions and may represent an example of the geometry and kinematic evolution of platform derived thrust sheets and similar belts worldwide associated with W-directed subduction zones.

How to cite: Vico, G. and Cardello, G. L.: Late Miocene thrust tectonics of the Latin Valley: insights from seismic lines (Central Apennines, Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20774, https://doi.org/10.5194/egusphere-egu2020-20774, 2020.

In collisional belts, foredeep turbidites are tracers of the evolution of the orogenic wedge. Syn-depositional tectonics affects the sedimentary facies distribution of the turbidite deposits, while post-depositional tectonics generates the major structures that deform the foredeep basins. The Aquitanian to Burdigalian Cervarola turbiditic succession is one of the main Oligo-Miocene foredeep units that characterize the northwestern portion of the Northern Apennines. The reconstructed sin and post depositional evolution of the Cervarola succession reveals that orogen-transversal tectonic structures strongly and persistently controlled this turbiditic succession, from the time turbidites were infilling the foredeep basin (Aquitanian-Burdigalian) to the time this foredeep deposits became a major and complex thrust sheet of the Northern Apennines orogenic wedge (post-Burdigalian-Present). The syn-depositional history of the Cervarola turbiditic succession has been defined through a detailed facies analysis that has allowed the basin morphology to be accurately constrained. Then, the post-depositional history has been addressed to define the multi-scale deformations preserved in the Cervarola succession through the following approaches: 1) analysis of published geological maps, 2) detailed field mapping, 3) construction of geological cross sections across the major folds, 4) analysis of meso-scale structures and 5) analysis of a seismic reflection profile. The study has outlined that the foredeep basin morphology was tectonically controlled and segmented by compressive structures transversal to the NW-SE basin elongation. The same structures were also present during the post-depositional compressive phases that built up the orogenic wedge and they have been even reactivated in the latest extensional events that have dismembered the mountain range. These orogeny-transversal and long-lasting (~23Myrs) lineaments cross-cut the entire tectonic stacking of the Northern Apennines, affecting tectonic units which suffered different amount of translation during the mountain building, making the reconstruction of the geological evolution possible only with an integrated approach as performed in this work.

How to cite: Piazza, A., Tinterri, R., and Artoni, A.: The “syn” and “post” depositional evolution of a foredeep basin segmented by orogen-transversal tectonic structures: the case of the Cervarola Sandstones Formation, Miocene, Northern Apennines, Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10031, https://doi.org/10.5194/egusphere-egu2020-10031, 2020.

The “Livorno-Sillaro” line represents one of the most important transversal structure of the inner Northern Apennines.  It has been described in the literature as a major strike-slip fault (e.g., Bortolotti, 1966; Carmignani et al., 1994; Pascucci, 2005; Pascucci et al., 2007), and it is divided into two segments, eastern and western. 

A stratigraphic-sequence frame for the late-Quaternary deposits has been developed by using the different facies associations defined through a large subsurface database analysis. Moreover, a correlation has been done between subsoil deposits and the outcropping sediments on the hilly areas (Livorno, Pisa and Cerbaie hills) surrounding the Arno valley.

Additionally, a morphotectonic analysis of the hydrographic networks and relief distribution has been done the Lidar data (DTM), supplied by the Tuscany Region, at the 2 m and 10 m of resolution. Specifically, the river system is particularly sensitive to deformation processes. The fluvial streams are in fact characterized by low geomorphological inertia and, therefore, by response times of a few hundred thousand years to the tectonic processes in progress.

As a result of the integrated multidisciplinary analysis, it was possible to highlight a tectonic activity in the middle Pleistocene -Holocene interval of the western portion of the "Livorno-Sillaro" lineament neglected in the geological literature until now.

References

Bortolotti V. (1966) – La tettonica trasversale dell’Appennino – La linea Livorno-Sillaro. Bollettino della Società Geologica Italiana, Vol.85, pp. 529-540, 3 ff., 1 tav.

Carmignani L., Decandia F.A., Fantozzi P.L., Lazzarotto A., Liotta D. & Meccheri M. (1994) – Tertiary extensional tectonics in Tuscany (Northern Apennines, Italy). Tectonophysics. Vol. 238, pp. 295-315.

Pascucci V. (2005) – Neogene evolution of the Viareggio Basin, Northern Tuscany (Italy). GeoActa. Vol. 4, pp. 123-128.

Pascucci V., Martini I.P., Sagri M. & Sandrelli F. (2007) – Effects of transverse structural lineaments on the Neogene-Quaternary basins of Tuscany (inner Northern Apennines, Italy). Sedimentary Processes, Environments, and Basins: A Tribute to Peter Friend.

How to cite: Sarti, G., Giannico, V. G., Pittaro, D., and Porta, L.: New insight on the sedimentary record related to the late-Quaternary tectonics of the western segment of the “Livorno-Sillaro” (Northern Tuscany, Italy)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19557, https://doi.org/10.5194/egusphere-egu2020-19557, 2020.

A geological mapping project was performed on the 1:10,000 scale in the northern Amerini Mts. (Narni–Amelia Ridge, Central Apennines), coupled with facies analysis and multidisciplinary outcrop characterisation. This project was focused on the Jurassic-Lower Cretaceous succession, in order to reconstruct the Mesozoic palaeogeography and tectono-sedimentary evolution of the study area. This sector of the Apenninic Chain (i.e. Umbria-Marche-Sabina palaeogeographic domain) experienced the Early Jurassic rifting phase, which dismembered the vast Calcare Massiccio carbonate platform. The development of a rugged submarine topography, coupled with drowning of the benthic factories, were the main effects of this normal faulting. The complex submarine physiography, made of structural highs and lows, is highlighted by facies and thickness variations of the Jurassic and Lower Cretaceous deposits. The hangingwall blocks hosted thick (hundreds of metres) pelagic successions, with variable volumes of admixed gravity-flow deposits. These successions onlapped the horst blocks along escarpments, rooted in the rift faults, where the pre-rift Calcare Massiccio was exposed. The tops of footwall blocks (Pelagic Carbonate Platforms or PCPs) were capped by thin (few tens of metres or less), fossil-rich and chert-free, condensed pelagic successions. This rift architecture was evened out at a domain scale in the Early Cretaceous. Successively, Miocene orogenic and Plio-Pleistocene extensional faulting caused uplift and exhumation of the Mesozoic rocks.

In the study area, geothematic mapping associated with the analysis of basin-margin unconformities and successions revealed a narrow and elongated Jurassic structural high (Mt. Croce di Serra - Mt. Alsicci structural high), surrounded by Jurassic basinal pelagites. The PCP-top condensed succession is not preserved. The chert-rich basinal units rest on the horst-block Calcare Massiccio through unconformity surfaces (palaeoescarpments), as marked by the silicification of the (otherwise chert-free) shallow-water limestone. The onlap successions embed megablocks of Calcare Massiccio (hundreds of metres across), detached from their parent palaeoescarpments. Very thin, condensed deposits form discontinuous veneers on the olistoliths of Calcare Massiccio (epi-olistolith deposits) and are onlapped by younger basin-fill pelagites. The beds surrounding the olistoliths are characteristically bent due to differential compaction, as their (newly acquired) strikes mimic the outline of the stiff objects they were burying.

Indirect evidence for a Toarcian, post-rift, tectonic pulse can be locally mapped, and is documented by angular unconformities between the Pliensbachian and Toarcian pelagites, as well as by mass-transport deposits found in the Rosso Ammonitico (Toarcian).

The same goes for millimetric to centimetric neptunian dykes made of Maiolica pelagites cross-cutting the Corniola Fm. (Sinemurian-Pliensbachian). These dykes, coupled with the occurrence of unconformities between Aptian-Albian pelagites (Marne a Fucoidi Fm.) and Lower Jurassic rocks (Calcare Massiccio and Corniola formations), provide evidence for a further Early Cretaceous tectonic phase, recently reported from the southern sectors of Narni-Amelia ridge.

How to cite: Zuccari, C., Cipriani, A., and Santantonio, M.: Mesozoic palaeogeography and tectono-stratigraphic features of the northern Amerini Mts. (Central Apennines, Italy): new constraints on their Jurassic and Cretaceous evolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3871, https://doi.org/10.5194/egusphere-egu2020-3871, 2020.

Recent biostratigraphic, sedimentological and petrological studies in the inner Northern Apennines (Italy) permit to refine the upper Palaeozoic successions of southern Tuscany, allowing new hypothesis to frame these formations in the Permian palaeogeographical scenario of the western Mediterranean domain. The Tuscan pre-Triassic deposits, belonging to the Monticiano-Roccastrada Unit, are generally barren or scarce in term of biomineralized fossiliferous content. They were mostly affected by HP-LT to LP-HT metamorphism that, together with the limited distribution of deposits, made difficult their stratigraphic correlation.

The present study is focused on two metamorphic units (i.e. Filladi e metacalcari di Fosso della Falsacqua Formation and Filladi e quarziti del Torrente Mersino Formation) which age attribution and correlation was strongly debated in the literature.

The Filladi e metacalcari di Fosso della Falsacqua Formation (minimum estimated thickness of about 150 m), cropping out in Monte Leoni area, is mainly characterized by black to dark-grey phyllite, metasiltstones and metasandstones with dark limestone intercalations. Due to the lack of biomineralized fossil content, by lithostratigraphic correlation with other formations cropping out in Tuscany, this formation was differently assigned to late Carboniferous-early Permian or Devonian.

The Filladi e quarziti del Torrente Mersino Formation (minimum estimated thickness of about 200 m) crops out in the Boccheggiano mining area and mainly consists of black to dark-grey quartz-phyllite, quartz metaconglomerates, light-grey quartzites, green phyllites and quartzites and light-grey phyllites. This formation resulted barren of fossil content and has been differently assigned to Ordovician-Silurian, Silurian-Devonian, late Carboniferous-Permian and Triassic by lithostratigraphic correlation with other Tuscan-Sardinian successions.

In the present study, the first finding of a middle Permian well-preserved microflora adds more constrains to the age attribution of these studied formations. This new age assignment permits to correlate the investigated formations with the coheval ones belonging to southern Tuscany (i.e. Farma Formation) and Elba Island (Rio Marina Formation) characterized by a similar microfloral content. Moreover, the occurrence of Gondwana-related sporomorphs, in all the studied formations, points to a new palaeogeographic scenario of the upper Palaeozoic successions from the northern Gondwana margin. The results of this integrated study inclines to consider the fragmentation of the northern margin of Gondwana as a result of several transtensional (pull-apart) basins where different laterally-related depositional environments leaded the sedimentation of these Tuscan middle Permian formations.

How to cite: Spina, A., Brogi, A., Capezzuoli, E., Cirilli, S., and Liotta, D.: Permian sporomorphs from upper Palaeozoic succession of Southern Tuscany (Italy): new constraints for the stratigraphy and palaeogeographic setting of the Tuscan Domain, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10374, https://doi.org/10.5194/egusphere-egu2020-10374, 2020.

The origin and evolution of an orebody hosted in metamorphic terrane is a prime topic in economic geology because they have implications on exploration as well as on related potential geo-environmental health hazards. The Alpi Apuane orebodies has long been known; however, their ore genesis and the relationships with the Apenninic age deformation and metamorphism is still a matter of debate. Indeed, they are still an interesting field of research, as proved by the recent discovery of a remarkable Tl anomaly associated to the baryte ± pyrite ± Fe-oxides ores of southern Alpi Apuane, northern Tuscany, Italy [1]. The present work reports a new detailed field and underground geological-structural investigation, performed from cartographic- to microscopic-scale, integrated by available drill-logs data, of one of these Tl-rich orebodies - the Buca della Vena ore.

The present study gives new insights on some aspect of the ore-forming events and discusses previous interpretations. According to our investigations, the ore settings were acquired during successive geological events related to an early hydrothermal-magmatic phase, likely of Permian age, and to the more recent Apenninic deformations. We suggest that the proto-ore was produced by hydrothermal activity related to the post-Variscan magmatic cycle (documented by the Permian age “Fornovolasco metarhyolite” Fm [2]), causing ore-formation, tourmalinization and hydrothermal alteration halo in the Cambrian-Lower Ordovician phyllites host-rocks. In our model, the ores were then partially exhumed suffering supergene alteration with development of minor Fe-oxides sedimentary mineralizations during the upper Norian-Hettangian. Finally, the previous hydrothermal and sedimentary ores, along with the host-rocks, were involved in the Apenninic orogenesis, and were recrystallized, and partially remobilized acquiring the current mineralogical, textural, and structural settings.

References:

[1] Biagioni, C., D’Orazio, M., Vezzoni, S., Dini, A., Orlandi, P., 2013. Mobilization of Tl-Hg-As-Sb-(Ag,Cu)-Pb sulfosalt melts during low-grade metamorphism in the Alpi Apuane (Tuscany, Italy). Geology, 41, 747-750.

[2] Vezzoni, S., Biagioni, C., D’Orazio, M., Pieruccioni, D., Galanti, Y., Petrelli, M., Molli, G., 2018. Evidence of Permian magmatism in the Alpi Apuane metamorphic complex (Northern Apennines, Italy): New hints for the geological evolution of the basement of the Adria plate. Lithos, 318-319, 104-123.

How to cite: Vezzoni, S., Pieruccioni, D., Dini, A., Molli, G., and Biagioni, C.: Origin and metamorphic reworking of the Buca della Vena Tl-rich orebody (Alpi Apuane, Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19978, https://doi.org/10.5194/egusphere-egu2020-19978, 2020.

An updated revision of the upper Carboniferous-Permian tectonics recorded in Corsica, Calabria and Tuscany is here proposed. We combine our and literature data to document how the sedimentary, tectono-metamorphic and magmatic upper Carboniferous-Permian record fits with a regional-scale tectonic scenario characterized by trascurrent fault systems associated with stretched crustal domains in which extensional regional structures, magmatism and transtensional basins developed. In Corsica, altogether with well-known effusive and intrusive Permian magmatism, the alpine S.Lucia nappe exposes a kilometer-scale portion of the Permian lower to mid-crust, with many similarities to the Ivrea-Verbano zone. The two distinct Mafic and Leucogranitic complexes, which characterize this crustal domain are juxtposed by an oblique-slip shear zone named as S.Lucia Shear Zone. Structural and petrological data document interaction between magmatism, metamorphism and shearing during Permian in the c. 800-400 °C temperature range. In Calabria (Sila, Serre and Aspromonte), a continuous pre-Mesozoic crustal section is exposed. The lower crust portion of such section is mainly made up of granulites and migmatitic paragneisses with subordinate marbles and metabasites. The mid-crustal section includes an up to 13 km thick sequence of granitoids of tonalitic to granitic composition, emplaced between 306 and 295 Ma and progressively deformed during retrograde extensional shearing to end with a final magmatic activity between 295 and 277 Ma, consisting in the injection of shallower dykes in a transtensional regime. The section is completed by an upper crustal portion mainly formed by a Paleozoic succession deformed as a low-grade fold and thrust belt, locally overlaying medium-grade paragneiss units, and therefore as a whole reminiscent of the external/nappe zone domains of Sardinia Hercynian orogen. In Tuscany we document, how late Carboniferous/Permian shallow marine to continental sedimentary basins characterized by unconformity and abrupt change in sedimentary facies (coal-measures, red fanglomerate deposits) and acid magmatism well fit a transtensional setting with a mid-crustal shear zone linked with a system of E-W trending (in present orientation) upper crust splay faults. We will frame the whole dataset in a regional framework of first-order transcurrent shear zones network which includes a westernmost S.Lucia Shear Zone and an easternmost East Tuscan Shear Zone, with intervening crustal domains in which extensional to transtensional shearing occured.

How to cite: Molli, G., Brogi, A., Caggianelli, A., Capezzuoli, E., Liotta, D., Spina, A., and Zibra, I.: Upper Carboniferous-Permian tectonics in Central Mediterranean: an updated revision, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2341, https://doi.org/10.5194/egusphere-egu2020-2341, 2020.