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The inner Apennines (Italy) are characterized by scattered outcrops of continent‐derived orogenic metamorphic units exposed along the Tyrrhenian coast from northern to southern Apennines. At least since the 1970s, some peculiar rocks exposed on Zannone Island (central Italy) have been described as the only Paleozoic‐Triassic metamorphic complex linking those exposed in the northern—with those in the southern Apennines. Assessing the protolith nature, thermobaric conditions, and structural features of what is accepted to be the metamorphic unit of Zannone is, therefore, crucial to elucidate the early paleotectonic evolution of the Apennines‐Tyrrhenian orogenic system. To that end, we interpreted seismic reflection profiles offshore Zannone, we carried out mesoscale and microscale structural investigations of representative outcrops on the island, performed X‐ray diffraction analysis, and K‐Ar and U‐Pb geochronology of representative clay gouge and syntectonic carbonate veins. Results show that the metamorphic rocks of Zannone can actually be reinterpreted as belonging to nonmetamorphic siliciclastic turbidites, likely deposited in foredeep settings, and coeval to the Oligocene‐Miocene Macigno Fm. of the northern Apennines. The turbiditic sequence was overthrust by Triassic dolostone in the early Miocene (~22 Ma), weakly deformed at

The nucleation and concentration of asbestos in rocks are mostly associated with mechanisms of fibre formation, combined with the water-dependent mineralogical alteration produced during the serpentinization of ultramafic masses. Very little is known about the structural settings and tectonic histories that influence and control the occurrence of asbestos in non-serpentinized rocks diffusely embedded within tectonized ophiolitic suites. Focusing on a case history provided by a tectonized metagabbro from the Ligurian Alps (northern Italy), a multiscale structural–petrographic approach is used to investigate the relationships between rock fabric and fibrous amphibole growth within the metagabbro. Meso- to microstructural observations are used to document the role of structurally controlled fluid–rock interactions in localizing the growth of fibrous amphibole during ductile-to-brittle shearing (mylonitic foliation to shear veins). A qualitative structural scenario is provided to illustrate the growth of asbestos amphiboles in shear veins during the progression of shear deformation towards semi-brittle rheological conditions. The mechanisms of the structurally controlled growth of fibrous amphibole in non-serpentinized rocks imply an examination of the tectonic boundary conditions that are at the origin of the concentration of asbestos in ophiolitic rocks involved in orogenic belt construction.

The Eocene-MioceneMianeh-Hashtroud igneous district in NW Iran is part of the Turkish-Caucasus-Iranian collision zone, a key region to decipher the assembly and differentiation of Gondwana-derived terranes along the Alpine-Himalayan convergence zone. Major inherited tectonic structures control in space and time the Mesozoic-Cenozoic transition from oceanic subduction to continental collision in the region. The geology of the study area is dominated by a polyphase, long-lived magmatic activity, spanning from similar to 45 to similar to 6 Ma. The igneous products are subalkaline to alkaline, with intermediate to acid compositions and a high-K calcalkaline to shoshonitic affinity. Evidence of crustal contamination is attested by inherited zircons in the oldest (Eocene-Oligocene) samples, with ages spanning from Neo-Archean to Paleocene. The Sr-Nd isotopic compositions of the Eocene-Oligocene samples plot close to the Bulk Silicate Earth estimate, whereas the Miocene samples document stronger crustal contamination. The lack of correlation between Nd-Sr isotopes and SiO2 supports a scenario of magma differentiation of different magma batches rather than crustal contamination. Major oxide and Sr-Nd isotopic variation lead us to suggest that magmatism is the consequence of re-melting of earlier underplated (Mesozoic-Tertiary) magmatic products, controlled by amphibole-dominated fractionation processes. Regional scale correlations show long-lived Cenozoic magmatism in NW Iran and Caucasus region, where the main porphyry and epithermal deposits occur. We propose that the Cenozoic collisional magmatism and the associated mineralisation at the junction between NW-Iran and Caucasus was controlled by the activity of a major, lithosphere-scale inherited boundary, transverse to the convergence zone. In such a geodynamic setting, the along-strike segmentation of the lithosphere slab generated asthenospheric melts, their upwelling into the metasomatised supra-subduction mantle wedge and the potential activation of different mantle and crustal sources, with consequent mineral endowment in the region. (C) 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

A better understanding of intraplate deformation requires the knowledge of the space–time scales involved in its development and to decipher possible links with the dynamic evolution of the plate boundaries. Central Iran provides an ideal test site to approach this scientific issue, since it is characterised by a prolonged history of Mesozoic–Cenozoic intraplate deformation that has been interfering with the spatio-temporal re-organization of the Zagros convergence zone along the Eurasia plate boundary. This study focus on the Doruneh Fault (DF) region that is considered as the northern mechanical boundary of the Central East Iranian Microcontinent. By combining field investigations with apatite low-temperature thermochronology, we present a revised tectono-stratigraphic scenario for the DF region, typified by a punctuated history of fault-related exhumation, burial and cooling history back to the Upper Cretaceous. When framed at regional scale, these results attest that the Zagros convergence zone, and its hinterland domain were fully mechanically coupled since ca. 40–35 Ma, a time lapse that is here referred as to the onset of continental collision along the Arabia–Eurasia plate boundary. In this scenario, the DF region operated throughout the Cenozoic as a major zone of residual stress accommodation and transfer in the hinterland domain of the Zagros convergence zone. Results of this study also suggest that the tectonic evolution along the Arabia–Eurasia plate boundary was modulated by the plate-boundary dynamics and by the modes of tectonic reactivation of the intracontinental weak zones of Central Iran and at its tectonic boundaries.

International audience; Unravelling the evolution of supradetachment basins developed in the hanging wall of low‐angle detachment faults may be an invaluable tool in reconstructing the tectonic evolution of highly extended terrains. These basins may record major regional tectonic events related to the exhumation of metamorphic core complexes, and the reconstruction of their evolution helps to quantify the amount of extension accommodated by such processes. Here we present stratigraphic and structural field evidence and micropaleontological constraints to the Neogene‐to‐Quaternary evolution of the supradetachment Gediz Graben that developed on top of the exhuming Central Menderes Massif (SW Turkey). This basin displays three different structural styles during its evolution: (i) it initiated as a ramp basin following the activation of the Gediz Detachment in the Middle Miocene; (ii) evolved as a half graben during the Late Miocene following the activation of high‐angle brittle faults at its southern margin; and (iii) reached its final symmetric graben configuration in Late Pliocene (?) – Quaternary times following the activation of its northern margin. New micropaleontological data document a short‐lived upper Tortonian marine episode in the basin, and major along‐strike variations in exhumation are documented on its southern margin. Our reconstruction shows how sedimentary basins originally formed in the hanging‐wall of detachment faults may eventually end up in tectonic contact with the mylonitic footwall. Finally, we highlight the importance of magmatism in localizing the deformation in highly extended terrains and in controlling the evolution of supradetachment systems.

Recent works documented Neogene to Quaternary dextral strike-slip tectonics along the Kuh-e-Sarhangi and Kuh-e-Faghan intraplate strike-slip faults at the northern edge of the Lut Block of Central Iran, previously thought to be dominated by sinistral strike-slip deformation. This work focuses on the evidence of Quaternary activity of one of these fault systems, in order to provide new spatiotemporal constraints on their role in the active regional kinematic scenario. Through geomorphological and structural investigation, integrated with optically stimulated luminescence dating of three generations of alluvial fans and fluvial terraces (at ~53, ~25, and ~6 ka), this study documents (i) the topographic inheritance of the long-term (Myr) punctuated history of fault nucleation, propagation, and exhumation along the northern edge of Lut Block; (ii) the tectonic control on drainage network evolution, pediment formation, fluvial terraces, and alluvial fan architecture; (iii) the minimum Holocene age of Quaternary dextral strike-slip faulting; and (iv) the evidence of Late Quaternary fault-related uplift localized along the different fault strands. The documented spatial and temporal constraints on the active dextral strike-slip tectonics at the northern edge of Lut Block provide new insights on the kinematic model for active faulting in Central Iran, which has been reinterpreted in an escape tectonic scenario.

Recent surging of renewed industrial interest in the exploration of low and medium enthalpy geothermal fields makes the accurate assessment of the geothermal potential essential to minimise uncertainties during both exploration and exploitation. The Torre Alfina field is a case of abandoned, but promising, geothermal field of central Italy where the roles of the internal structural setting and of the recharge areas on the hydrothermal circulation are largely unconstrained. In this paper, field structural data integrated with geomorphic lineament analysis document the occurrence of post-orogenic deformation structures controlling the compartmentalisation of the Torre Alfina geothermal field. Strike-slip and subordinate normal fault systems (with associated network fractures) cut and dislocate the internal architecture of the reservoir and prevent its hydraulic connection with Mount Cetona, considered to be the recharge area and where hydrothermal manifestation, including travertine deposition, occurs. 230Th/234U radiometric dating of superposed travertine units gives 200, 120 and 90ka respectively, inferred to correspond to the age of the fossil hydrothermal circulation during tectonic activity. The results have been used for illustrating a new geological conceptual model for the Torre Alfina area where the geothermal system is composed of different compartments. Tectonic structures define the main boundaries between compartments, helping the understanding of why productive and non-productive wells were found in apparently similar structural settings within the Torre Alfina field. © 2013 Elsevier B.V.

This study is the first documentation of syn-diagenetic non-tectonic contractional deformations observed in two Pleistocene thermogene travertine deposits from the late Miocene-Pleistocene Tuscan extensional-hydrothermal province (Italy). The deposits consist of primary porous beds hosting secondary bed-parallel carbonate veins. The porous beds are generally flat-lying, particularly in the upper section of the deposits, whereas the veined beds frequently form undulated structures. These structures are up to a few meters in wavelength, are mostly confined within the lower-middle section of the deposits, and are here mostly interpreted as folds. Field observations, U-Th geochronology, and stable isotope analyses are used to characterize the origin of veins and folds. Radiometrically-determined age inversions, structure overprinting relationships, downward growth of vein crystals, deformation of primary sedimentary structures, and downward increasing frequency of veins and folds show that the undulated travertine beds can be mainly interpreted as the product of syn-diagenetic hydrothermal rejuvenation causing non-tectonic veining and folding. The non-tectonic hypothesis is also supported by the absence of contractional deformation in the travertine-hosting sediments. The folds were generated by complex mechanisms including bending and buckling caused by laterally-confined volume expansion during syn-diagenetic circulation of mineralizing fluids and related incremental veining. Modeling some folds with the Biot-Ramberg's buckling equation shows a vein-to-host travertine viscosity ratio between 1.5 and 4, confirming the syn-diagenetic origin of folds. Veining and folding changed some original properties of travertines including rheology, fabric, porosity, and chronological sequence. The identification of these structures and related changes of rock properties (e.g., age rejuvenation) is relevant for the proper interpretation of thermogene travertines as recorders of many geological processes including paleoclimate oscillations, earthquake occurrences, hydrothermal circulations, and uplift or incision rates. Synthesizing, the studied thermogene travertines appear more like sedimentary-hydrothermal-hybrid zoned deposits rather than pure sedimentary systems uniquely responding to the superposition law. © 2017 Elsevier B.V.

By studying a quarried site exposed in the Ligurian Alps (northern Italy), this work aims to assess the impact of the tectonic structures on the exploitable rock volume characteristics/properties and, more in general, on the three-dimensional quarry architecture for its future exploitation. A field-based, multidisciplinary dataset has been integrated within a 3D geological model performed in a Geographical Information System (GIS) environment. The spatial distribution, geometry, and internal fabric of the main tectonic structures (mainly represented by faults and fracture networks) have been recognised as responsible for a structural compartmentalisation within the study area. In situ geomechanical measurements (uniaxial strength by using a Schmidt hammer) have been compared with distribution of the tectonic structures. A simulation of the influence of the tectonic structures on the rock mechanical behaviour has been performed in GIS. We conclude that occurrence of tectonic structures determines a first order degree in geodiversity at quarried sites, influencing both intrinsic (lithology and petrography) and secondary (mechanical) properties of the excavated rock volume. Consequently, understanding and reconstructing the deformation style and intensity of the tectonic setting constitute a further geological exploration criterion for assessing strategy of rock excavation and exploitation. The identification of tectonic structures is relevant to face frequently documented problems in active quarrying, such as mass movement and slope failure, reduced rock-mass quality, or non-exploitable quarry domains.

The reactivation of faults and shear zones is a widely documented process and represents a fundamental characteristic of deformation in the continental lithosphere. The Ross Sea in Antarctica mainly owes its present-day configuration to an extended period of early Paleozoic subduction-related crustal accretion and the subsequent Mesozoic–Cenozoic tectonics of the West Antarctic Rift System. It thus represents an ideal setting in which to study reactivation processes. This study uses the 40 Ar- 39 Ar laserprobe technique in conjunction with mesostructural, microtextural, and nanotextural analyses to unravel the style and timing of a newly discovered mylonite-pseudotachylyte association from the rift shoulder in northern Victoria Land of Antarctica. Pseudotachylyte-bearing fault rocks overprint a reverse ductile shear zone developed in a Cambrian granite, within an overall transpressional right-lateral kinematic scenario. In situ 40 Ar- 39 Ar analyses of biotite from the mylonite mainly yielded ages of 460–440 Ma, suggesting that ductile shearing occurred during the early Paleozoic orogenic cycle. In contrast, in situ data on the pseudotachylyte matrix yielded scattered and much younger ages of ca. 120–66 Ma. Younger ages of ca. 50 Ma were derived from step-heating experiments on matrix specimens obtained through microtexturally controlled microsampling. Taking into account the possible effects of analytical artifacts due to sample irradiation and of Ar loss due to the ultrafine grain of the matrix, coseismic faulting is assigned to the middle Eocene. Results indicate a minimum 390 m.y. period of tectonic quiescence and prove that brittle reactivation occurred in response to a totally different stress regime. Regionally, the study confirms a post–early Eocene age for the activation and propagation of intraplate dextral strike-slip tectonics in Victoria Land.

""Anisotropy of magnetic susceptibility (AMS). analysis has been carried out in the thermometamorphic. aureole surrounding the Late Miocene Monte Capanne. pluton (Elba Island, Central Italy). The identification and. separation of the main carriers of the magnetic susceptibility. by low-temperature and high-field AMS measurements. demonstrate that a correct knowledge of the. magnetic fabric is needed in order to use AMS for tectonic. interpretations. Magnetic fabric data, combined with. structural data from the aureole, and their comparison with. data from the pluton itself, were used to constraint the. mode of pluton emplacement. Results document an intimate. linkage between the magmatic flow pattern and the. syn-metamorphic fabrics acquired during pluton emplacement. in the host rocks. The magnetic\\\/structural fabric in. the aureole rocks is dominated by flattening deformation. and no systematic relationship with any regional tectonic. feature is observed. These results suggest that local processes. induced by magma ascent in the upper crust might. have played a primary role in space generation for pluton. emplacement in the Tuscan Magmatic Province, suggesting. a revaluation of the modes of pluton emplacement during. the post-orogenic evolution of the northern Apennine system. as a whole.""

In recent years, many studies have addressed the effect on human health caused by asbestos exposures. As asbestos is a group of fibrous minerals that mainly occurs in mafic and ultramafic rocks (ophiolitic sequences), a close relationship between asbestos occurrence and the geological history of host rocks should be expected. By reviewing the existing literature and presenting characteristic examples, it is proposed a direct correspondence exists between the presence of fibrous minerals in ophiolites and the rock fabric systematics due to the combined activity of deformation, metamorphism/metasomatism, and rock/fluid interaction. Understanding the geological factors that may be at the origin of the nucleation/growth of fibrous minerals constitutes a necessary requirement for developing a methodological and analytical procedure to evaluate asbestos hazard (AH) in the natural prototype (ophiolitic rocks). A parameterisation of the AH in function of the main geological processes that produce the rock fabric systematics in different tectonic/geodynamic settings is discussed. A geological multidisciplinary approach (based on geological-structural field evidence combined with textural, mineralogical, petrological, and geochemical investigations) is proposed as the prerequisite for the evaluation of AH in natural environments. This approach, in particular, can provide a robust basis to formulate a procedural protocol finalised to the mitigation of asbestos effects in environments where these effects are still a real threat.

The Uluguru Mountains of eastern Tanzania represent a key area to unravel the tectonic history of Gondwana assembly along the Neoproterozoic East African Orogen. On the basis of combined structural and 40Ar/39Ar geochronological investigations, we have re-interpreted the structural architecture of the region. Texturally-late, ductile to cataclastic low-angle tectonic contacts are recognized, which delimit the contacts between the main lithological units that form a post-metamorphic, NW-verging nappe stack. 40Ar/39Ar geochronology places this nappe-forming event at c. 550 Ma, post-dating tonalitic dyke emplacement at c. 580 Ma. Results from this study (i) demonstrate that a distinct and later episode of convergence occurred in the region at c. 55 Ma, when previous structural elements of the East African Orogen were finally juxtaposed; and (ii) extends models involving the polyphase assembly of Gondwana to East Africa. © 2008 Blackwell Publishing Ltd.

The Neogene–Quaternary Albegna basin (southern Tuscany, central Italy), located to the south of the active geothermal field of Monte Amiata, hosts fossil and active thermogene travertine deposits, which are used in this study to reconstruct the spatio-temporal evolution of the feeding hydrothermal system. Travertine deposition is controlled by regional tectonics that operated through distributed N-S– and approximately E-W–striking transtensional fault arrays. The geochronological data set (230Th/234U, uranium-series disequilibrium) indicates a general rejuvenation (from >350 to

An integrated structural, anisotropy of magnetic susceptibility (AMS) and paleomagnetic study was carried out on Plio-Pleistocene sedimentary basins in eastern Sicily. These basins belong to three main tectonic domains: the Tyrrhenian hinterland domain, the Catania foredeep domain, and the Hyblean foreland domain. We sampled 329 oriented samples from 25 sites in selected areas from the different tectonic domains. The AMS is typical for weakly deformed sediments, with a magnetic foliation sub-parallel to the bedding plane, and a well-defined magnetic lineation. The orientation of the magnetic lineation is strongly controlled by the main tectonic deformation recorded in the basins. Structural and AMS data define a transition from NW–SE extension in the Tyrrhenian hinterland domain, to E–W compression in the Catania foredeep domain, to E–W extension in the Hyblean foreland domain, respectively. Reliable paleomagnetic results have been obtained in 12 out of 25 sampled sites. Data show that no significant rotations occurred in any of the studied basins at least since the middle Pleistocene. These results allow us to define an upper limit to the large rotations about vertical axes that have been previously found in the Calabria and Sicily regions.

The Miocene Aljibe thrust imbricate (Flysch Trough), in the external zone of the Gibraltar Arc, shows large changes in structural style towards the foreland. Rheological variation of the decollement rocks—Triassic evaporitic rocks and Mesozoic limestones—appears to be the main factor controlling the contrasts in structural style that characterise adjacent wedge domains. In order to test this hypothesis, we carried out analogue experiments involving three-dimensional variations of decollement material. A plate of viscous material was placed in the central part of the models, at the base of the sand multilayers. Different geometries of the viscous plate were used. Experimental results show a strong link between the rheological properties of the decollement material and the structure of the overlying thrust wedge. These results compare well with the internal geometry and vergence distribution in the Aljibe thrust imbricate. Indeed, the tectonic style of the wedge can be explained as a consequence of variations of rock type along the basal decollement.

Mt. Overlord and Mt. Melbourne are part of the fossil-to-active eruptive centre belt of the McMurdo Volcanic Group, located along the western shoulder of the West Antarctic Rift System in north Victoria Land (Antarctica). The formation and localisation of these volcanic centres are intimately connected to the regional fault patterns associated with Neogene transtensional stretching in the West Antarctic Rift System. This study reports about 900 structural data of faults and fault-related joints affecting the Miocene–Pliocene deposits of Mt. Overlord and the Plio-Quaternary deposits of Mt. Melbourne. Fault surfaces strike along three main directions (NW–SE, NE–SW, and N–S) with high (> 70°) dip angles. The reconstructed fault geometries and kinematics document a NW–SE strike-slip fault system having dextral motion in the Mt. Overlord area, which evolves into a more complex structural architecture characterised by transtensional deformations in the Mt. Melbourne area, where volcanism is still active. The fault array can be reconciled with principal and subordinate deformation structures developed at the termination region of NW–SE intraplate strike-slip fault systems inducing oblique rifting in the West Antarctic Rift System. The structural dataset, integrated with available geochronological constraints, gives rise to a two-step (Miocene-to-Holocene) tectonic scenario in which the spatial migration of the volcanic activity towards the eastern boundary of the Transantarctic Mountains occurred during the evolution of the West Antarctic Rift System.

Field data on Cenozoic faults and the McMurdo dyke arrays in the Reeves Glacier–Mawson Glacier area, Victoria Land, Antarctica, allow us to support noncoaxial transtensional tectonics along the N–S-trending western shoulder of the Ross Sea. Dyke injection within a crustal-scale right-lateral strike-slip shear zone is testified by magma filled, tension gash-like arrangements within some master fault zones, and by the left-stepping arrangements of dykes in the intrafault zones. The noncoaxiality of deformation is shown by the re-activation of many dyke walls as right-lateral strike-slip faults. This suggests an increase in the strike-slip component over time along the western shoulder of the Ross Sea. Our data support the relevance of transtensional to strike-slip tectonics for triggering melting and controlling the geometry and modes of magma emplacement.

The Neogene tectonic evolution of the western Mediterranean region is accompanied and outlasted by diffuse magmatism. This study describes the tectonic setting, the petrography and geochemistry of the Early Miocene granitic dyke swarm that occurs in the Oued Amter area, in the core of the Alboran Domain of the Moroccan Rif. The structural setting indicates dyke intrusion assisted and controlled by strike-slip tectonics that operated through conjugate, NW–SE left-lateral and NE–SW right-lateral fault strands. The overall composition of the dykes (the high SiO2 contents (69–77 wt.%), coupled with low concentrations of TiO2, MgO, FeO, CaO), the high 87Sr/86Sr (0.719–0.722) and the low 143Nd/144Nd (ca. 0.5120) values point to a predominantly crustal origin of these magmatic bodies, compatible with a process involving muscovite–(biotite) dehydration melting of fertile metasedimentary sources. The isotopic signature is similar to that of the basement rocks of the Alboran Sea, suggesting for a similar crustal source for the Early Miocene felsic magmatism of the Betic–Rif realm. When framed within the regional setting, these data are used to propose a synthetic geodynamic model for the Early Miocene tectonic and magmatic evolution of the western Mediterranean region.

Late Cenozoic strike-slip tectonics and active faulting in Central Iran have been extensively described in the last decades. This study presents results of integrated structural and geomorphological analyses along the Kuh-e-Sarhangi Fault, a major NE-SW striking brittle deformation zone that cuts across the basement and Neogene-Quaternary cover successions at the north-western edge of the Lut Block. Structural investigations document post-Neogene NE-SW dextral transpressive tectonics and geomorphic evidence support a Late Quaternary age for the faulted alluvial fan deposits along the bedrock range fronts. Northward, the nearly parallel Great Kavir (Doruneh) Fault is known to have active left-lateral strike-slip kinematics, and its easternmost segment was considered as the northern margin of the Lut Block. The new findings impose reconsideration of the current regional kinematic models, with implications on the seismogenic fault networks of Central Iran. © 2013 Elsevier B.V.

Alpine orogens in the central Mediterranean region have revealed the concomitance of crustal extension in back-arc domain and crustal shortening in frontal domain. Quantitative data of deformation in the frontal orogenic wedges are necessary to understand how the shortening-extension pair evolves in terms of structures, orogenic transport, timing, and exhumation rate. This paper deals with kinematics and ages of the frontal thrust systems of the Calabria-Peloritani Arc (Italy) exposed in the eastern Sila Massif. We first present structural fieldwork, onshore and offshore well log data, and new apatite fission-track (AFT) thermochronology. Then, we describe the structural architecture of the studied area as an ENE-verging stacking of thrust sheets involving basement units and syn-orogenic sediments. The AFT study documents that thrust sheets entered the partial annealing zone from 18. Ma to 13. Ma. This Early-Middle Miocene thrusting phase was coeval with exhumation of high-pressure/low temperature metamorphic rocks in the hinterland of the orogen (Coastal Chain area), mainly driven by top-to-the-W extensional tectonics. Opposite kinematic shear senses (contractional top-to-the-E and extensional top-to-the-W) and different exhumation rates (slow in the frontal, more rapid in the hinterland) are framed in a tectonic scenario of a critically tapered orogenic wedge during the eastward retreating of the Apennine slab. © 2012 Elsevier B.V.

Geological mapping coupled with structural investigations carried out in the Voltri Massif (eastern Ligurian Alps, Italy) provide new data for the interpretation of the tectonic context controlling main fabric development during exhumation of its high-pressure core. The Voltri Massif is here interpreted as a c. 30 km-long eclogite-bearing, asymmetric dome formed by the progressive verticalisation of the regional, second-phase mylonitic foliation developed during retrogressive greenschist metamorphic conditions. In this light, the exhumation history is driven by a ductile-to-brittle extensional process, operating through low-angle, top-to-the-W multiple detachment systems. A Late Eocene-Early Oligocene age for this extensional episode is proposed on the basis of structural correlations, stratigraphic and radiometric constraints. In this scenario, the Voltri Massif is interpreted as an extensional domain developed to accommodate the Late Eocene-Early Oligocene arching of the Western Alps-Northern Apennines orogenic system. © Springer-Verlag 2008.

[1] In this paper, new paleomagnetic results from the Calabrian Arc are presented, together with a critical review of all paleomagnetic data collected in the last decades in southern Italy. Our study is focused on the upper Miocene to middle Pleistocene deposits of the Crati extensional basin, a sector of the arc where an abrupt change in the sense of paleomagnetic rotations is observed. Paleomagnetic data indicate that the Crati basin underwent a uniform clockwise (CW) rotation of about 15–20 in its central and southern part, whereas the northern sector is organized in small-scale fault-bounded blocks, which rotated independently. We interpret this pattern of deformation as the evidence of the complex nature of this area, which represents the boundary between two domains characterized by opposite rotations: the southern Apennines, which rotated counterclockwise, and the Calabria and Sicily, which rotated CW. Integrating these new paleomagnetic data with paleomagnetic data from southern Italy, we reconstruct the history of paleomagnetic rotations through time. Paleomagnetic rotations highlight the peculiarity of the formation of the Calabrian Arc curvature and imply that either an oroclinal bending model or a progressive arc model cannot be simply applied to the Calabrian Arc formation. We describe a realistic tectonic-geodynamic model, where the progressive curvature of the Calabrian Arc is framed within the space-time evolution of the Ionian subduction system.

An integrated structural and paleomagnetic study was carried out on Neogene- Quaternary clastic sedimentary sequences exposed in north Calabria to defi ne the brittle postorogenic evolution of the inner sector of the Calabrian arc. The structural, mineralogical, and magnetic fabric data presented in this paper suggest that the postorogenic basins of north Calabria originated and developed under an extensional tectonic regime that has been active since the middle Miocene. Results were used to defi ne the spatial and temporal evolution of the extensional fault systems in the framework of extensional processes active in the backarc region of the southeastward-migrating Apennine subduction system. Our data indicate that regional backarc extension operated in the brittle crust, and the data trace a continuous evolution from low- to high-angle extensional faulting. Paleomagnetic data show that this continuous extensional process was accompanied by complex interactions among faultbounded crustal blocks. In fact, the extensional domain is subdivided into different structural compartments, separated by the adjustment in the fault strike imposed by the regional rotation pattern.

The Ross Sea region of the East Antarctic plate provides evidence for intraplate tectonic activity in 13 Cenozoic times. Still unresolved are the cause, timing and kinematics of this intraplate tectonism. By 14 integrating and discussing the different (kinematic and temporal) signals of Cenozoic tectonism, intraplate 15 dextral shearing is recognized as the main tectonic regime controlling the structural architecture of the Ross 16 Sea region from the Mid-Eocene (c. 40–50 Ma) onward. We speculate that propagation and persistence of this 17 tectonic regime through time constitutes a feasible seismogenetic framework to explain past and current 18 tectonism in the Ross Sea region.

The polymetamorphic Alpujarride nappe Complex is one of the main constituents of the internal zones of the Alpine Betic–Rif chain. Still under debate are the tectonic processes involved in exhumation of its deep-seated portions, metamorphosed under high-pressure conditions during the Alpine crustal thickening. A systematic study of the exhumation-related ductile and brittle fabric observed in the different Alpujarride units reveals, independently from the metamorphic grade and age of the protoliths, a common sequence of deformation events. It involves early progressive top-to-the-N/NE ductile shearing, followed by a major top-to-the-N post-metamorphic extensional faulting event, which produced a complex re-organisation of the whole nappe pile. We propose that ductile exhumation of the deep-seated Alpujarride nappe piles was mainly completed before the onset of the post-orogenic extensional processes associated with the Early Miocene Alboran rifting. A switch from an early ductile underthrusting regime (Paleogene in age) to semibrittle-to-brittle extension (Early Miocene onward) is here proposed as responsible for the exhumation history of the Alpujarride Complex.

The nappe-structured belt of Calabria constitutes the eastward termination of the southern branch of the Alpine Mediterranean belt that delimits the northern edge of the Africa plate. Contrasting hypotheses for the origin and tectonic significance of the north Calabrian nappe edifice have been proposed, and kinematic data from north Calabria have been used to support different interpretations of the Alps-Apennines linkage and the polarity of the Tethyan subduction in the Apennine region. We reconstruct the architecture of the north Calabria nappe edifice through a multidisciplinary approach which integrates structural investigations with metamorphic thermobarometry and 40Ar/39 Ar geochronology. Results from this study indicate that north Calabria consists of a Tertiary nappe stack, resulting from superimposed top-to-the-west extensional shearing (late Oligocene to middle Miocene in age) onto a previously structured top-to-the-east compressional belt (Eocene to Oligocene in age). This study also documents that the top-to-the-west extensional tectonics was achieved by means of regionally sized extensional detachment fault systems, stretching apart and translating as allochthonous fragments the previously accreted units. Thinning operated by top-to-the-west extensional detachment tectonics also resulted in the direct juxtaposition of non-Alpine or slightly Alpine metamorphosed units (upper plate complex) onto the previously exhumed deep-seated portions of the orogenic wedge, metamorphosed under blueschist facies metamorphic conditions (lower plate complex). These findings support a new tectonic scenario for the orogenic history of north Calabria, which may be adequately framed within the Tertiary Apennine-Tyrrhenian system evolution. Copyright 2004 by the American Geophysical Union.

We present the results of field investigations carried out at the southern termination of the Priestley Fault, a major Cenozoic right-lateral strike-slip fault system in northern Victoria Land, Antarctica. The Priestley Fault was originally traced from offshore seismic profiles. Its onshore prosecution was inferred from the regional geological picture. Our work provides the first robust dataset on the kinematics and structural architecture of the Priestley Fault. The fault system includes a principal displacement zone (PDZ), where most horizontal displacement is accounted for, and a transtensional splay zone (TSZ) in the southern side consisting of a major basin at the fault tip, the Terror Rift, and minor ones paralleling it cratonward. Part of the strike-slip displacement is transferred by fault splaying from the principal displacement zone to the basin-boundary faults in the transtensional splay zone. The principal displacement zone is characterised by strongly transpressive deformation and this contrasts with the extensional component occurring in the transtensional splay zone. Such a contrast is only apparent because the two regions are kinematically linked. Transfer of the residual right-lateral strike-slip displacement from the tip region of the principal displacement zone to the basin-boundary fault systems of the Terror Rift represents the most effective displacement compensation mechanism at the termination of the Priestley Fault. It provides an additional solution for reducing the well known and still fully unsolved discrepancy between large translations of adjacent crustal blocks and the lack of comparable displacement values in their boundary strike-slip fault systems. The unquestionable evidence of intense Cenozoic brittle deformations in north Victoria Land imposes a re-examination of the regional tectonic framework, commonly interpreted as the mere result of the Early Paleozoic Ross Orogeny.