The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extension

The role of oroclinal bending in the structural evolution of the Central Anatolian Plateau: evidence of a regional changeover from shortening to extensionThe NW-SE striking extensional Inönü-Eskişehir Fault System is one of the most important active shear zones in Central Anatolia. This shear zone is comprised of semi-independent fault segments that constitute an integral array of crustal-scale faults that transverse the interior of the Anatolian plateau region. The WNW striking Eskişehir Fault Zone constitutes the western to central part of the system. Toward the southeast, this system splays into three fault zones. The NW striking Ilıca Fault Zone defines the northern branch of this splay. The middle and southern branches are the Yeniceoba and Cihanbeyli Fault Zones, which also constitute the western boundary of the tectonically active extensional Tuzgölü Basin. The Sultanhanı Fault Zone is the southeastern part of the system and also controls the southewestern margin of the Tuzgölü Basin. Structural observations and kinematic analysis of mesoscale faults in the Yeniceoba and Cihanbeyli Fault Zones clearly indicate a two-stage deformation history and kinematic changeover from contraction to extension. N-S compression was responsible for the development of the dextral Yeniceoba Fault Zone. Activity along this structure was superseded by normal faulting driven by NNE-SSW oriented tension that was accompanied by the reactivation of the Yeniceoba Fault Zone and the formation of the Cihanbeyli Fault Zone. The branching of the Inönü-Eskişehir Fault System into three fault zones (aligned with the apex of the Isparta Angle) and the formation of graben and halfgraben in the southeastern part of this system suggest ongoing asymmetric extension in the Anatolian Plateau. This extension is compatible with a clockwise rotation of the area, which may be associated with the eastern sector of the Isparta Angle, an oroclinal structure in the western central part of the plateau. As the initiation of extension in the central to southeastern part of the Inönü-Eskişehir Fault System has similarities with structures associated with the Isparta Angle, there may be a possible relationship between the active deformation and bending of the orocline and adjacent areas.

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Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault.

10.5194/egusphere-egu21-12153 ◽

2021 ◽

Author(s):

Fabien Caroir ◽

Frank Chanier ◽

Virginie Gaullier ◽

Julien Bailleul ◽

Agnès Maillard-Lenoir ◽

...

Keyword(s):

Fault Zone ◽

Plate Boundary ◽

Fault Zones ◽

North Anatolian Fault ◽

Fault System ◽

Eurasian Plate ◽

Slip Rates ◽

The North ◽

South West ◽

North Aegean

The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10&#176; since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V &#8220;T&#233;thys II&#8221;, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (>300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.

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Low-temperature thermochronology of fault zones

10.5194/egusphere-egu2020-6060 ◽

2020 ◽

Author(s):

Takahiro Tagami

Keyword(s):

Low Temperature ◽

Fault Zone ◽

Fission Track ◽

Thermal Sensitivity ◽

Fault Zones ◽

Fault System ◽

Vein Formation ◽

Fission Track Thermochronology ◽

Mineral Vein ◽

Host Rocks

Thermal signatures as well as timing of fault motions can be constrained by thermochronological analyses of fault-zone rocks (e.g., Tagami, 2012, 2019).&#160; Fault-zone materials suitable for such analyses are produced by tectocic and geochemical processes, such as (1) mechanical fragmentation of host rocks, grain-size reduction of fragments and recrystallization of grains to form mica and clay minerals, (2) secondary heating/melting of host rocks by frictional fault motions, and (3) mineral vein formation as a consequence of fluid advection associated with fault motions.&#160; The geothermal structure of fault zones are primarily controlled by the following three factors: (a) regional geothermal structure around the fault zone that reflect background thermo-tectonic history of studied province, (b) frictional heating of wall rocks by fault motions and resultant heat transfer into surrounding rocks, and (c) thermal influences by hot fluid advection in and around the fault zone.&#160; Geochronological/thermochronological methods widely applied in fault zones are K-Ar (40Ar/39Ar), fission-track (FT), and U-Th methods.&#160; In addition, (U-Th)/He, OSL, TL and ESR methods are applied in some fault zones, in order to extract temporal information related to low temperature and/or recent fault activities.&#160; Here I briefly review the thermal sensitivity of individual thermochronological systems, which basically controls the response of each method against faulting processes.&#160; Then, the thermal sensitivity of FTs is highlighted, with a particular focus on the thermal processes characteristic to fault zones, i.e., flash and hydrothermal heating.&#160; On these basis, representative examples as well as key issues, including sampling strategy, are presented to make thermochronological analysis of fault-zone materials, such as fault gouges, pseudotachylytes and mylonites, along with geological, geomorphological and seismological implications.&#160; Finally, the thermochronological analyses of the Nojima fault are overviewed, as an example of multidisciplinary investigations of an active seismogenic fault system.&#160;References:<ol><li>Tagami, 2012. Thermochronological investigation of fault zones. Tectonophys., 538-540, 67-85, doi:10.1016/j.tecto.2012.01.032.</li> <li>Tagami, 2019. Application of fission track thermochronology to analyze fault zone activity. Eds. M. G. Malusa, P. G. Fitzgerald, Fission track thermochronology and its application to geology, 393pp, 221-233, doi: 10.1007/978-3-319-89421-8_12.</li> </ol>

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Abundance and distribution of Hg and As in the polymetamorphic Precambrian basement of western Canada

Canadian Journal of Earth Sciences ◽

10.1139/e79-207 ◽

1979 ◽

Vol 16 (12) ◽

pp. 2196-2203 ◽

Cited By ~ 1

Author(s):

R. A. Burwash ◽

R. R. Culbert

Keyword(s):

Fault Zone ◽

Shear Zones ◽

Ore Deposits ◽

Fault System ◽

Western Canada ◽

Precambrian Basement ◽

Lake District ◽

Surface Mapping ◽

Mean Values ◽

Abundance And Distribution

mean values of Hg and As in the subsurface Precambrian basement of western Canada are 66 ppb and 1.42 ppm respectively (183 samples). Both figures are close to accepted crustal averages. Plots of cumulative frequency vs. log ppm approach log-normality, but with evidence of small populations enriched in Hg and As and 23% of samples depleted in Hg.Trend surface mapping shows that both Hg and As have regional highs and lows. Several types of multivariate analyses, when applied to petrologic and chemical variables, show that Hg was depleted during both cataclasis and K-metasomatism related to the Hudsonian orogeny. A model for Hg mobility is suggested, with the McDonald–Hay River fault system acting as a conduit for westward migration during the Hudsonian metasomatism. This northeast trending system bisects the Pinchi Lake district Hg ore deposits, which occur along the northwest trending Pinchi fault zone. Mesozoic reactivation of Hudsonian crystalline basement beneath the Omineca crystalline belt may have produced these economic deposits.Multivariate analysis of As values in relation to petrologic variables suggests that As is mobilized during the earlier stages of cataclasis, but finally concentrates locally along major shear zones. The As trend surface high coincides with the area of maximum mylonization along the McDonald fault zone. Concentration of As in major shear zones matches known distributions of niccolite, rammelsbergite, and arsenopyrite in several ore deposits of the western Canadian Shield.

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Inner structure and kinematics of the Sushchany-Perga fault zone of the Ukrainian Shield according to the tectonophysical study

Geofizicheskiy Zhurnal ◽

10.24028/gzh.0203-3100.v43i1.2021.225496 ◽

2021 ◽

Vol 43 (1) ◽

pp. 142-159

Author(s):

S.V. Mychak ◽

L.V. Farfuliak

Keyword(s):

Fault Zone ◽

River Basin ◽

Shear Zones ◽

Thrust Fault ◽

Fault Zones ◽

Ukrainian Shield ◽

Fault Type ◽

Fracture Formation ◽

Five Phases

The field tectonophysical works were carried out in the upper reaches of the Ubort River basin along the Zolnia-Maidan-Kopischany fault. The research aim was determination of the inner structure and kinematics of the Sushchany-Perga fault zone of the western pfrt of the Ukrainian Shield. For investigation of fracturing and structural-textural elements of rocks the structural-paragenetic method of tectonophysics was used. It was determined that formation of the Sushchany-Perga fault zone continued during at least five phases of deformation. They were accompanied by the formation of differently oriented shear zones: Khmelivka, Sushchany, Perga, Rudnia-Khochin, Lopatychi. The Khmelivka and Sushchany shear zones are similar to striking of the Nemyriv and Khmelnik fault zones of the Ukrainian shield, which belong to the Nemyriv stage of faulting (~1.99 Ga). The Rudnia-Khochin and Perga phases are related to the fact that the Sushchany-Perga fault zone was quite active during the junction of the Fennoscandia and Sarmatia microplates. We have established that the development of thrust fault and normal down throw fault type shears, which took place in an area of compression and extension, respectively, is associated with the formation period of the Perga granitoids complex (1.80—1.70 Ga).This alternation of the compression and extension conditions has led to formation of the ore occurrences and deposits within the Perga tectonic joint. This investigation found that the Sushchany-Perga fault zone arose in the Late Paleoproterozoic at the Nemirov stage of fracture formation, simultaneously with Goryn, Lutsk, Teteriv and Nemyriv fault zones as a result of the junction of two ancient microplates — Fennoscandia and Sarmatia.

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Supplemental Material: Tectonic geomorphology and Plio-Quaternary structural evolution of the Tuzgölü fault zone, Turkey: Implications for deformation in the interior of the Central Anatolian Plateau

10.1130/geos.s.12574148 ◽

2020 ◽

Author(s):

N.J. Krystopowicz ◽

et al.

Keyword(s):

Fault Zone ◽

Structural Evolution ◽

Tectonic Geomorphology ◽

Anatolian Plateau ◽

River Profiles

Includes map and tables for all morphometrically analyzed basins and river profiles for the 23 analyzed basins.

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A review of the Pan-African evolution of the Arabian Shield

GeoArabia ◽

10.2113/geoarabia0701103 ◽

2002 ◽

Vol 7 (1) ◽

pp. 103-124 ◽

Cited By ~ 6

Author(s):

Pierre Nehlig ◽

Antonin Genna ◽

Fawzia Asfirane ◽

C. Guerrot ◽

J.M. Eberlé ◽

...

Keyword(s):

Structural Evolution ◽

Sedimentary Basins ◽

Fault Zones ◽

Fault System ◽

Arabian Shield ◽

Geologic History ◽

Lower Paleozoic ◽

The North ◽

Pan African ◽

History Of

ABSTRACT Recent fieldwork and the synthesis and reappraisal of aeromagnetic, geologic, structural, geochemical, and geochronologic data have provided a new perspective on the structural evolution and geologic history of the Arabian Shield. Although Paleoproterozoic rocks are present in the eastern part of the Shield, its geologic evolution was mainly concentrated in the period from 900 to 550 Ma during which the formation, amalgamation, and final Pan-African cratonization of several tectonostratigraphic terranes took place. The terranes are separated by major NW-trending faults and by N-, NW- and NE-oriented suture zones lined by serpentinized ultramafic rocks (ophiolites). Terrane analysis using the lithostratigraphy and geochronology of suture zones, fault zones, overlapping basins, and stitching plutons, has helped to constrain the geologic history of the Arabian Shield. Ophiolites and volcanic-arcs have been dated at between 900 and 680 Ma, with the southern terrane of Asir being older than the Midyan terrane in the north and the Ar Rayn terrane in the east. Final cratonization of the terranes between 680 and 610 Ma induced a network of anastomosing, strike-slip faults consisting of the N-trending Nabitah belt, the major NW-striking left-lateral transpressive faults (early Najd faults), lined by gneiss domes and associated with sedimentary basins, and N- to NE-trending right-lateral transpressive faults. Following the Pan-African cratonization, widespread alkaline granitization was contemporaneous with the deposition of the Jibalah volcanic and sedimentary rocks in transtensional pull-apart basins. Crustal thinning was governed by the Najd fault system of left-lateral transform faults that controlled the formation of the Jibalah basins and was synchronous with the emplacement of major E- to NW-trending dike swarms throughout the Arabian Shield. The extensional episode ended with a marine transgression in which carbonates were deposited in the Jibalah basins. Continuation of the thinning process may explain the subsequent deposition of the marine formations of the lower Paleozoic cover. Our interpretation of the distribution and chronology of orogenic zones does not correspond entirely to those proposed in earlier studies. In particular, the N-trending Nabitah and NW-trending Najd fault zones are shown to be part of the same history of oblique transpressional accretion rather than being two distinct events related to accretion and dispersion of the terranes.

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Structural analysis and metamorphism of the Barlow Fault Zone, Chibougamau area, Neoarchean Abitibi Subprovince: implications for gold mineralization

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2020-0048 ◽

2020 ◽

Author(s):

Pierre Bedeaux ◽

Antoine Brochu ◽

Lucie Mathieu ◽

Damien Gaboury ◽

Réal Daigneault

Keyword(s):

Fault Zone ◽

Gold Mineralization ◽

Structural Evolution ◽

Amphibolite Facies ◽

Fault System ◽

Kinematic Evolution ◽

Facies Metamorphism ◽

Abitibi Subprovince ◽

Northern Portion ◽

Peak Metamorphism

Faults and deformation zones are important features of Archean terranes because of their significance for structural evolution and the formation of large gold districts. In the Chibougamau area, northeastern portion of the Abitibi Subprovince, an Apogee Metal Earth seismic reflection survey identified an association between an exceptional shallow-dipping subsurface reflector zone and the Barlow Fault Zone visible at the surface. This study aimed to reconstruct the kinematic evolution of the Barlow Fault Zone, determine its position within the structural setting of this section of the Abitibi Subprovince, and evaluate its importance for gold potential in the northern part of the Chibougamau area. Structural reconstruction and field observations are compatible with a reverse south-over-north movement related to a ductile north–south shortening event, which culminated with amphibolite metamorphism. Geothermobarometers indicate peak metamorphism conditions of 550 ± 50 °C and 6 ± 1.2 kbar. Results from this study suggest that amphibolite facies metamorphism covers a much wider area within the Chibougamau region than previously documented. The Barlow Fault Zone shares similar geometric characteristics and evolutionary history with other gold-bearing structures in the Abitibi Subprovince, but ultimately it was unable to provide optimal conditions for channelling fluid and precipitating gold. The Barlow Fault Zone is interpreted as a back-thrust fault that belongs to a more extensive south-dipping fault system encasing juxtaposed tectonic slivers. This system, with amphibolite facies metamorphism, is a defining feature of the northern portion of the Chibougamau area and developed during the accretion between the Opatica and Abitibi subprovinces.

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Faults and magma reservoirs along the Southern Andes Volcanic zone (SAVZ): linking oservations and numerical models of stress change controlling magmatic and hydrothermal fluid flow

10.5194/egusphere-egu2020-11473 ◽

2020 ◽

Author(s):

Javiera Ruz ◽

Muriel Gerbault ◽

José Cembrano ◽

Pablo Iturrieta ◽

Camila Novoa Lizama ◽

...

Keyword(s):

Fluid Flow ◽

Stress Field ◽

Fault Zone ◽

Numerical Models ◽

Fluid Pressure ◽

Seismic Inversion ◽

Fault Zones ◽

Fault System ◽

Far Field ◽

Trigger Failure

The Chilean margin is amongst the most active seismic and volcanic areas on Earth. It hosts active and fossil geothermal and mineralized systems of economic interest documenting significant geofluid migration through the crust. By comparing numerical models with field and geophysical data,&#160;we aim at pinning when and where fluid migration occurs through porous domains, fault zone conduits, or remains stored at depth awaiting a more appropriate stress field. Dyking and volcanic activity occur within fault zones along the SAVZ, linked with stress field variations in spatial and temporal association with &#8211;short therm- seismicity and -long term- oblique plate convergence. Volcanoes and geothermal domains are mostly located along or at the intersection of margin-oblique fault zones (Andean Transverse Faults), and along margin-parallel strike slip zones, some which may cut the entire lithosphere (Liqui&#241;e-Ofqui fault system). Whereas the big picture displays fluid flow straight to the surface, at close look significant offsets between crustal structures occur. 3D numerical models using conventional elasto-plastic rheology provide insights on the interaction of (i) an inflating magmatic cavity, (ii) a slipping fault zone, and (iii)&#160;regional tectonic stresses. Applying either (i) a magmatic overpressure or (ii) a given fault slip can trigger failure of the intervening rock, and generate either i) fault motion or ii) magmatic reservoir failure, respectively, but only for distances less than the structures' breadth even at low rock strength. However, at greater inter-distances the bedrock domain in between the fault zone and the magmatic cavity undergoes dilatational strain of the order of 1-5x10-5. This dilation opens the bedrock&#8217;s pore space and forms &#171;pocket domains&#187; that may store up-flowing over-pressurized fluids, which may then further chemically interact with the bedrock, for the length of time that these pockets remain open. These porous pockets can reach kilometric size,&#160;questioning their parental link with outcropping plutons along the margin. Moreover, bedrock permeability may also increase as fluid flow diminishes effective bedrock friction and cohesion. Comparison with rock experiments indicates that such stress and fluid pressure changes may eventually trigger failure at the intermediate timescale (repeated slip or repeated inflation). Finally, incorporating far field compression (iii) loads the bedrock to a state of stress at the verge of failure. Then, failure around the magmatic reservoir or at the fault zone occurs for lower loading. Permanent tectonic loading on the one hand, far field episodic seismic inversion of the stress field on the other, and localized failure all together promote a transient stress field, thus explaining the occurrence of transient fluid pathways on seemingly independent timescales. These synthetic models are then discussed with regards to specific cases along the SVZ, particularly the Tatara-San Pedro area (~36&#176;S), where magnetotelluric profiles document conductive volumes at different depths underneath active faults, volcanic edifices and geothermal vents. We discuss the mechanical link between these deep sources and surface structures.

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Structural evolution of a crustal-scale seismogenic fault in a magmatic arc: The Bolfin Fault Zone (Atacama Fault System)

10.5194/egusphere-egu21-3093 ◽

2021 ◽

Author(s):

Simone Masoch ◽

Rodrigo Gomila ◽

Michele Fondriest ◽

Erik Jensen ◽

Tom Mitchell ◽

...

Keyword(s):

Fault Zone ◽

Large Scale ◽

Damage Zone ◽

Structural Evolution ◽

Crystalline Basement ◽

Fault System ◽

Fault Mechanics ◽

Seismogenic Fault ◽

Magmatic Arc ◽

Atacama Fault System

The nucleation and evolution of major crustal-scale seismogenic faults in the crystalline basement as well as the process of strain localization represent a long-standing, but poorly understood, issue in structural geology and fault mechanics. Here, we addressed the spatio-temporal evolution of the Bolfin Fault Zone (BFZ), a >40-km-long exhumed seismogenic splay fault of the 1000-km-long strike-slip Atacama Fault System. The BFZ has a sinuous fault trace across the Mesozoic magmatic arc of the Coastal Cordillera (Northern Chile). Seismic faulting occurred at 5-7 km depth and &#8804; 270 &#176;C in a fluid-rich environment as recorded by extensive propylitic alteration and epidote-chlorite veining. The ancient (125-118 Ma) seismicity is attested by the widespread occurrence of pseudotachylytes both in the fault core and in the damage zone. Field geological surveys indicate nucleation of the BFZ on precursory geometrical anisotropies represented by magmatic foliation of plutons (northern and central segments) and andesitic dyke swarms (southern segment) within the heterogeneous crystalline basement. Faulting exploited the segments of precursory anisotropies that were favorably oriented with respect to the long-term stress field associated with the oblique ancient subduction. The large-scale sinuous geometry of the BFZ may result from linkage of these anisotropy-pinned segments during fault growth. This evolution may provide a model to explain the complex fault pattern of the crustal-scale Atacama Fault System.

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Role of the deep crustal scale geometry on Western Alps strain partitioning : Insights from S-wave velocity tomography

10.5194/egusphere-egu21-8928 ◽

2021 ◽

Author(s):

Stéphane Schwartz ◽

Ahmed Nouibat ◽

Yann Rolland ◽

Thierry Dumont ◽

Anne Paul ◽

...

Keyword(s):

Wave Velocity ◽

Shear Zones ◽

Western Alps ◽

Crustal Thickening ◽

Variscan Orogeny ◽

Western Boundary ◽

S Wave ◽

Structural Anisotropy ◽

Velocity Tomography

The recent S-wave velocity tomography undertaken at the scale of the Alps by Nouibat et al. (2021) allows a reappraisal of the deep structure of this mountain belt. These geophysical data highlight the role of crustal geometry in the strain field development observed in the Western Alps. The geophysical imagery shows a standard crustal thickness in the foreland, with slow velocities (<3.6 km.s-1) in the lower crust. The occurrence of a sharp Moho offset of 5-12 km is detected beneath the External Crystalline Massifs (ECMs). The ECMs do not show any significant crustal thickening in their frontal parts (<35 km), except for the Pelvoux ECM (35-40 km). Beneath the internal zones, east of the Penninic Frontal Thrust, the crustal geometry is more complex with the presence of an European continental slab subducting locally deeper than 80 km beneath the Adria plate. This slab is overlain by a high-pressure metamorphic orogenic prism. The lower part, corresponding to the Ivrea gravimetry anomaly, shows seismic signatures of serpentinized mantle (Vs between 3.8 and 4.3 km.s-1) whose upper limit is located at 10 km depth below the Dora Maira internal crystalline massif. This new crustal-scale image can be compared to the current deformation pattern, which appears highly partitioned at the scale of the Alpine arc. The internal zones show a transtensional deformation regime, whose activity is distributed along two major seismic lineaments (the &#8216;Piemontais&#8217; and &#8216;Brian&#231;onnais&#8217; ones). The Alpine European foreland shows a transpressional deformation that is more diffuse and associated with vertical displacements in the ECMs. Beneath the Po plain, the seismic activity is deeper (>40 km), and correlates with a transpressional deformation which is localized along sub-vertical lineaments. The deformation of the orogenic prism appears controlled by a deeper and rigid mantle indenter split in two units by a major subvertical serpentinized structure. The upper unit, which indents horizontally and vertically the crustal orogenic prism, is located between 20 and 45 km depth. The lower unit corresponds to the western boundary of the Adria mantle that pinches directly the European slab. The surface observations and geochronological data suggest that the Moho offstets are superposed on European crustal-scale faults trend inherited from the Variscan orogeny, following the East-Variscan strike-slip system. This structural anisotropy was reactivated during the Alpine orogeny as shear zones in a mainly transpressional regime since about 25-30 Ma, as documented by Ar-Ar data on syn-kinematic mica and U-Pb on monazite. The comparison of current seismicity with the kinematics of exhumed shear zones suggests a continuity of this regime since 25-30 Ma, in response to the Adria plate anticlockwise rotation.

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