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Western Carpathian orogeny has been the subject of intense scientific debate due to the occurrence of enigmatic features, leading several authors to provide contrasting geological models. In this paper, a new interpretation for the tectonic evolution of the Western Carpathians is provided based on the following: (i) an analysis of the stratigraphy of the Mesozoic-Tertiary successions across the thrust belt domains, (ii) a reappraisal of the stratigraphy and sedimentology of the “tectonic mélange” (i.e., the so-called Pieniny Klippen Belt) marking the suture between the Inner and Outer Carpathians, and (iii) the construction of a series of balanced and restored cross sections, validated by 2-D forward modeling. Our analysis provides a robust correlation of the stratigraphy from the Outer to the Inner Carpathians, independently of the occurrence of oceanic lithosphere in the area, and allows for the reinterpretation of the tectonic relationships among the Inner Carpathians, the Outer Carpathians, and the Pieniny Klippen Belt and the exhumation mechanisms affecting this orogenic belt. In order to constrain the evolution during the last 20 Ma, our model also integrates previously published and new apatite fission track and apatite (U-Th-Sm)/He data. These latter indicate a middle-late Miocene exhumation of the Pieniny Klippen Belt. In this study, the recent regional uplift of the Pieniny Klippen Belt is described for the first time using a 2-D kinematic model for the tectonic evolution of the Western Carpathians.

Field data and seismic reflection profiles of various resolutions, calibrated by deep well logs, have been used to unravel the tectonic evolution of the Crati Basin (southern Italy). The study area is located in the northern portion of the Calabrian Arc, a well-developed arc-shaped feature of the circum-Mediterranean belts, consisting of a series of ophiolite-bearing tectonic units and overlying basement nappes. NW–SE oriented left-lateral strike-slip faults exerted a major control on the tectonic evolution of northern-central Calabria, from Middle Miocene to Lower Pleistocene times. Such faults, arranged in an en-echelon geometry and dissecting the pre-existing Late Oligocene–Early Miocene orogenic belt, led to a structural setting including major N-S striking synforms – as the offshore Paola Basin and the Crati Basin are interpreted based on our results – separated by a broad antiformal ridge. Since the Middle Pleistocene, both E- and W-dipping normal faults developed in the southernmost sector of the Crati Basin, probably as a consequence of both uplift of the orogenic edifice and Tyrrhenian back-arc extension. The pre-existing regional strike-slip faults became inactive in this sector of the belt. However, working as persistent barriers, it is envisaged here that they inhibited the southern propagation of the newly formed normal faults, which therefore propagated towards the north. A minimum value of cumulative displacement of ca. 600 m has been unraveled for the central sector of the Crati Basin since Middle Pleistocene times. This yields a vertical strain rate of ca. 0.9 mm/y during the last 700 ka.

To unravel how and where coseismic and interseismic deformation impacts the spatial and temporal patterns of rock uplift of the Lurestan sector of the Zagros Mountains, we performed an investigation of the large‐scale features of topography and river network coupled with 2‐D finite element modeling. Geomorphological analysis and constraints from parameters such as elevation, local relief, normalized channel steepness index (ksn), river longitudinal profiles, and transformed river profiles (chi plots) were used to unravel the time‐space distribution of vertical motions. Whereas the much longer timescale over which topography grows and/or rivers respond to tectonic or climatic perturbations with respect to even multiple seismic cycles, the outputs of the finite element model yield fundamental information on the source of the late part of the spatiotemporal evolution of surface uplift recorded by the geomorphology. Model outputs shed new light into the processes controlling relief evolution in an actively growing mountain belt underlain by a major blind thrust. The outputs illustrate how coseismic slip controls localized uplift of a prominent topographic feature—the Mountain Front Flexure—located above the main upper crustal ramp of the principal basement thrust fault of the region, while continuous displacement along the deeper, aseismic portion of the same basement fault controls generalized uplift of the whole crustal block located farther to the NE, in the interior of the orogen.

Petrographic, petrophysical and fracture analyses were carried out on middle Cretaceous platform carbonates of the southern Apennines (Italy) that represent an outcrop analogue of the Val d’Agri and Tempa Rossa reservoirs of the Basilicata region. The studied outcrops, which are made of interlayered limestones and dolomites of inner platform environment, were selected to study the impact of dolomitization on reservoir properties and the control of dolomite texture on fracture development. Two types of dolomites – both formed during very early diagenesis – were found interlayered, at a metre scale, with micrite-rich limestones (mainly mudstones and wackestones). Dolomite A is fine-to medium crystalline and makes non-planar mosaics. Dolomite B is coarse-crystalline and makes planar-s and planar-e mosaics. The intercrystalline space of the planar-e subtype of dolomite B is either open or filled by un-replaced micrite or by late calcite or saddle dolomite cement. Dolomite A and dolomite B have similar average porosities of 3.7 and 3.1% respectively, which are significantly higher than the average porosity of limestones (1.4%). Their poro-perm relationships are similar, with the notable exception of planar-e type B dolomites, which generally display higher permeability values. The intensity of top bounded fractures is distinctly lower in coarse-crystalline dolomites than in fine-crystalline dolomites and limestones, both at the macro- and the micro-scale. On the other hand neither lithology (i.e. limestone vs. dolomite) nor dolomite crystal size control the intensity of perfect bed-bounded fractures, which is strictly controlled by the fracture layer thickness. Our results provide information that could be used as guidance for the characterization and modelling of fractured carbonate reservoirs made of interlayered limestones and dolomites.

Along convergent plate boundaries, the negative buoyancy of the lithosphere pulls the slab into subduction. Bending and offscraping of the downgoing plate are processes occurring at subduction zones and acting against plate motions. These localised dissipative processes cause extensional deformation in the bulge-foredeep region and thrusting and folding in the thrust wedge respectively. Within this framework, widespread early subduction-related extensional structures affecting pre-orogenic rocks of the downgoing plate of fossil subduction systems, are commonly interpreted as induced by extension occurring in the forebulge-foredeep zone. Slab pull is to date, rarely considered as a potential causative process when interpreting basin-scale pre-shortening extensional structures. The problem of distinguishing slab-pull and foreland flexuring induced extensional structures relates to the fact that for most belts, slab pull and forebulge-foredeep flexuring are expected to produce extension roughly in the same direction (i.e. parallel to the foredeep-belt system) and, when syn-kinematic strata are not available, discriminating between these two processes is arduous. In this work we present a field investigation of basin-scale extensional faults from the downgoing plate of the Oman Mts. fossil subduction system. Syn-kinematic strata indicate that normal fault development largely predated extension in the bulge-foredeep region. Herein, we argue that such faulting occurred during the transition from induced to self-sustained subduction, when the negative buoyancy of the slab started to exceed the resisting forces and the downgoing plate began to be pulled towards the trench. © 2019 Elsevier Ltd

The Val d'Agri area provides the opportunity to analyse active structures in a seismic region for which a large amount of subsurface data is available. This area, which was struck in 1857 by one of the most destructive earthquakes in Italy (MW = 7.03), represents a unique natural laboratory to gain new insights into geometry, modes and rates of faulting controlling crustal deformation in an actively extending orogen. In this study, a crustal geological section through the southern Apennines is discretized into a finite element model (FEM). We present a 2D elastoplastic FEM that reproduces stress perturbations and strain field around the Val d'Agri active fault system. The influence of fault strand activity on interseismic crustal deformation is tested by a series of computer models, whose predictions are compared with the horizontal velocity components of continuous GPS sites in the region and with stress directions and geological data. The best fit with available geological and geophysical constraints is obtained with a 300 km long, 29 km deep model formed by a multilayer including three components having different rheological characteristics and including several shallow, locked fault segments, which branch into a freely slipping major basement fault at depth. Finite element modelling provides new insights into the controversial and widely debated active tectonic setting of the study area, pointing out the fundamental role played by a structural reactivation process involving inherited, long-lived, mature fault systems at depth. Our FEM, reconciling apparently contrasting geological and geophysical constraints from the study area, points to maximum stress build up and strain accumulation at a depth of 15 ± 5 km. Such a depth range is suggested as the most likely one for the nucleation of large events such as the 1857 Val d'Agri earthquake.

A geothermal model for the area of the Basilicata oil fields has been obtained by an analytical procedure. The model takes into account both the temperature variation due to the re-equilibrated conductive state after thrusting and frictional heating. Input parameters include heat flow density data and a series of geologically derived constraints – thrust depth, timing of thrusting, slip rate – obtained by the integration of surface and subsurface datasets. For the top 5 km of the crust, the resulting geothermal curve shows a remarkably good fit with temperatures recorded from deep oil wells. The new geotherm provides a fundamental constraint for rheological and stress accumulation modelling in the seismically active study area. Furthermore, the analytical solution provided in this study may be used as a basis to calculate the relevant geotherm for further areas and/or tectonic settings.

The Patagonian Andes represents a unique natural laboratory to study surface deformation in relation to deep slab dynamics. In the sector comprised between latitudes 41°30′ and 43°S, new apatite (U-Th)/He ages indicate a markedly different unroofing pattern between the “broken foreland” area (characterized by Late Cretaceous to Paleogene exhumation) and the adjacent Andean sector to the west, which is dominated by Miocene-Pliocene exhumation. These unroofing stages can be confidently ascribed to inversion tectonics involving reverse fault-related uplift and concomitant erosion. Late Cretaceous-Paleogene shortening and exhumation are well known to have affected also the thrust belt sector of the study area during a prolonged stage of flat-slab subduction. Therefore, the different ages of near-surface unroofing documented in this study suggest coupling of the deformation between the thrust belt and its foreland during periods of flat-slab subduction (e.g., during Late Cretaceous-Paleogene times) and dominant uncoupling during periods of steep-slab subduction and rollback, even when these are associated with high convergence rates (i.e., > 4 cm/yr), as those documented in Miocene times for the Patagonian Andes. Fil: Savignano, Elisa. Università di Padova; Italia Fil: Mazzoli, S.. Università degli Studi di Napoli Federico II; Italia Fil: Arce, Luis Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Franchini, Marta Beatriz. Universidad Nacional del Comahue; Argentina. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina Fil: Gautheron, C.. Universite Paris-sud Xi; Fil: Paolini, M.. Pan American Silver; Argentina Fil: Zattin, Massimiliano. Università di Padova; Italia

The early stages of southern Apennine development have been unraveled by integrating the available stratigraphic record provided by synorogenic strata (of both foredeep and wedge-top basin environments) with new structural data on the Liguride accretionary wedge cropping out in the Cilento area, southern Italy. Our results indicate that the final oceanic subduction stages and early deformation of the distal part of the Apulian continental margin were controlled by dominant NW–SE shortening. Early Miocene subduction-accretion, subsequent wedge emplacement on top of the Apulian continental margin and onset of footwall imbrication involving detached Apulian continental margin carbonate successions were followed by extensional deformation of the previously ‘obducted’ accretionary wedge. Wedge thinning also enhanced the development of accommodation space, filled by the dominantly siliciclastic Cilento Group deposits. The accretionary wedge units and the unconformably overlying wedge-top basin sediments experienced renewed NW–SE shortening immediately following the deposition of the Cilento Group (reaching the early Tortonian), confirming that the preceding wedge thinning represented an episode of synorogenic extension occurring within the general framework of NW–SE convergence. The documented Early to the Late Miocene steps of southern Apennine development are clearly distinct with respect to the subsequent (late Tortonian-Quaternary) stages of fold and thrust belt evolution coeval with Tyrrhenian back-arc extension, which were characterized by NE-directed thrusting in the southern Apennines.

The main structural characteristics of the Caggiano and Polla faults, exposed in the epicentral area of the 1561 earthquake (Mw = 6.4), southern Italy, have been investigated in detail to assess their spatial and temporal properties, and to evaluate their seismogenic potential. These right stepping normal faults show an overlap of about 7 km and an across strike separation of about 4 km. The geometric relationships between the Caggiano and Polla faults, but also the displacement distribution along each fault, demonstrate that they have been strongly interacting throughout the Pleistocene. Nevertheless, geological evidence of Holocene tectonic activity was mainly recognized along the Caggiano Fault (faulted late glacial deposits) and in the southernmost part of the Polla Fault (faulted deposits of probably Late Pleistocene age). This suggests that the Caggiano Fault can be considered as the most tectonically active fault in the Vallo di Diano Fault System. By calculating Coulomb stress changes, we have constrained modes of mechanical interactions between the two faults in a scenario compatible with the 1561 earthquake. This approach allows us to argue that both the Caggiano and the Polla Faults are probably linked at depth, and part of the same seismogenic structure which may be potentially responsible for composite ruptures with magnitude ≥ 6.5.

The recent earthquake sequences of 2012 (northern Italy) and 2013 (Marche offshore) provided new, fundamental constraints to the active tectonic setting of the outer northern Apennines. In contrast to the Po Plain area, where the 2012 northern Italy earthquakes confirmed active frontal thrusting, the new focal mechanisms obtained in this study for the 2013 Marche offshore earthquakes indicate that only minor thrust fault reactivation occurs in the Adriatic domain, even for a theoretically favourably oriented maximum horizontal compression. Recent seismicity in this domain appears to be mainly controlled by transcurrent crustal faults dissecting the Apennine thrust belt. The along-strike stress field variation from the Po Plain to the Adriatic area has been quantitatively investigated by applying the multiple inverse method (MIM) to the analysis of the entire seismicity recorded from January 1976 to August 2014, from the top 12 km of the crust (fault plane solutions from 127 earthquakes with MW ≥ 4), allowing us to obtain a comprehensive picture of the state of stress over the outer zone of the fold and thrust belt. The present-day stress field has been defined for 39 cells of 1.5° × 1.5° surface area and 12 km depth. The obtained stress field maps point out that, although the entire outer northern Apennines belt is characterized by a sub-horizontal maximum compressive axis (σ1), the minimum compression (σ3) is sub-vertical only in the Po Plain area, becoming sub-horizontal in the Adriatic sector, thus confirming that the latter region is dominated by an active tectonic regime of strike-slip type.

The Monte Alpi area of the Southern Apennines represents the only sector of the thrust belt where the reservoir rocks (i.e. Apulian Platform carbonates) for major hydrocarbon accumulations in southern Italy are interpreted to crop out. Tectonic evolution and exhumation of this area were analysed by integrating stratigraphic and structural data with different organic and inorganic parameters which record the burial and thermal evolution of the sediments (vitrinite reflectance, fluid inclusions, and I/S mixed layers in clayey sediments). Our analyses suggest that the presently exposed Monte Alpi structure suffered a loading of ca. 4000 m, owing to the emplacement of allochthonous units in Early Pliocene times. Available geological data indicate that erosion of the tectonic load occurred since the Late Pliocene, when the area first emerged. This implies an average exhumation rate in excess of 1 mm/year. A model can be constructed which matches the maturity indices and also takes into account intermediate stages of the evolution, resulting from combined structural and fluid inclusion data. By this model, a first stage of exhumation would have taken place at an average rate of about 0.36 mm/year. This was controlled by uplift and erosion associated with both: (i) thrusting at depth within the Apulian carbonates (Late Pliocene), and (ii) strike-slip faulting (Early Pleistocene). A second exhumation stage would have occurred in the last 700 ky at a much faster rate (ca. 4 mm/year) as a result of extensional tectonics. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

Soil gas measurements of different gas species with different geochemical behaviors were performed in the area of the Pecore Plain, a 200m x 300m sized, fault-bounded extensional basin located in the northern Mount Marzano massif, in the axial belt of the southern Apennine chain. The Pecore Plain area was affected by coseismic surface faulting during the M-s = 6.9, 1980 Irpinia earthquake, the strongest and most destructive seismic event of the last 30 years in southern Italy. The collected data and their geostatistical analysis provide new insights into the control exerted by active fault segments on deep-seated gas migration toward the surface. The results define anomalies that are aligned with the NW-SE trending coseismic rupture of the 1980 earthquake along the western border of the plain, as well as along the southern border of the plain where a hidden, E-W striking fault is inferred. Geospatial analysis highlights an anisotropic spatial behavior of Rn-222 along the main NW-SE trend and of CO2 along the E-W trend. This feature suggests a correlation between the shape and orientation of the anomalies and the barrier/conduit behavior of fault zones in the area. Furthermore, our results show that gas migration through brittle deformation zones occurs by advective processes, as suggested by the relatively high migration rate needed to obtain anomalies of short-lived Rn-222 in the soil pores.

The study of Quaternary fault zones in the High Agri Valley (southern Italy) and in the axial zones of the central Apennines, allowed us to collect information on the permeability structure, fluid characteristics, and scaling properties of the main fault zones exposed in the area. Detailed structural mapping allowed us to derive the appropriate values of the fractal dimension characterising different active fault zone patterns and to evaluate the basic parameters needed for assessing the architecture and related permeability structure of the mapped faults. Scan line and scan area analysis helped in constraining the scaling properties of some of the attributes (i.e. fault zone thickness, fracture spacing etc.) of the main fault zones and in defining their validity range. Our results suggest that, in the Apennines, (i) extrapolation of the architectural indices of a fault zone is admissible over three orders of magnitude, and (ii) the composition of the analysed fluid inclusions and related homogenisation temperatures are associated with fault-driven fluid circulation from both superficial and deep (4–6 km) levels.

In this study, surface geological data resulting from a detailed field survey, including structural and biostratigraphic analysis, have been integrated with subsurface (seismic lines and well logs) data in order to reconstruct the tectonic evolution of the external zones of the northern Italian Apennines in the Romagna-Marche foothills and Adriatic Sea areas. This integrated analysis shows: (1) a late Messinian to lower Pleistocene progression of structural development from the hinterland to the foreland of the studied sector of the thrust belt; (2) relatively limited (≤20%), southward increasing, amounts of shortening (obtained by the construction of line-length balanced and restored geological cross sections); (3) a regional deformation style characterized by the presence of backthrusts associated with most foreland-vergent thrust ramps, leading to quasi-symmetric uplift and a low critical taper for the wedge, typical of foreland fold and thrust belts with a weak basal decollement (Triassic anhydrites in the present case); (4) an important influence of basement faulting which, despite a general basement-cover decoupling, appears to control stress localization in the latter, producing linkage of basement and cover stuctures in a combination of thin- and thick-skinned tectonic styles; and (5) contrasting structural styles characterizing deep features, as imaged by seismic reflection profiles, and shallow ones. Deep stuctures consist of growth anticlines bounded by major thrust ramps and back limb back thrusts, separated by broader, open synclines, both involving a Mesozoic-Paleogene, mainly carbonate, passive margin succession. In the crestal zones of major anticlines, shallow structures, affecting Neogene terrigenous foredeep sediments, show a complex pattern of upright to recumbent folds (of tens to hundreds of meters wavelength) related to minor thrusts and backthrusts. Deformation of the Mesozoic-Paleogene multilayer appears to be dominated by thrust propagation in the cores of early formed anticlines developed by buckling instabilities. The overlying Neogene deposits are detached from the carbonate substratum along the base of the foredeep succession. Bedding-parallel slip occurring along this detachment level appears to be accommodated by the complex structures in the crests of major anticlines, where the thrusts lramp to the surface cutting up section. Complex shallow structures, interpreted to accommodate at shallow structural levels the deep deformation, would therefore represent a geometrical requirement for maintaining strain compatibility across the shallow detachment level located at the base of the foredeep succession.

The southern Apennines thrust system developed in Late Cretaceous to Quaternary times in response to deformation processes induced by the convergence between the African and European plates. The structural associations recognized in the area permit us to attribute these processes to three main evolutionary stages: an oceanic subduction, an obduction and a collisional to post-collisional stage. Each stage covers a time period of about 10 7 years and comprises several deformation sequences of similar time scales (about 7–9×10 6 years). In the southern sectors of the chain, in the Calabria–Lucania borderland area, the earliest phases of deformation of the oceanic accretionary wedge are recorded by the metamorphic and structural signature of oceanically-derived rock units. The progressive growth of the southern Apennines thrust system is attested by the overprinting relationships existing among the different structural assemblages characterizing the obduction, collisional and post-collisional stages. The latter includes the Early Pleistocene development of strike-slip faults, which are responsible for strong lateral variations in the crustal structure of the chain, and for the compartimentalization of the system into various sectors displaying different subsurface features.

Based on a detailed structural study performed on a reservoir surface analogue, a fracture permeability model for carbonate reservoirs is proposed. This involves four hierarchical systems, each one assumed to convey fluids exclusively to that of immediately higher order. New basic equations are then provided, simulating hydrodynamic reservoir response. The large scale, first-order structures consist of faults, to which high-permeability structures (damage zones) are associated. At the meter scale, stratabound joint systems, together with bedding joints bounding the mechanical layers, form a connected network transporting fluids to the fault system. At a lower scale, down to crystal size, non-stratabound joints constitute a pervasive and capillary fracture network which conveys fluids within the rock mass. The non-fractured host rock constitutes the lower permeability system (at the crystal scale). As no published works include an effective integration of detailed structural and numerical models, the present study aims at covering a significant gap in the literature, also providing appropriate theoretical basis for subsequent studies on fracture network modeling and reservoir simulation. Besides its application in the field of reservoir development and management, the illustrated model may also be useful in environmental studies involving ground fluids such as e.g. in the field of special/toxic/nuclear waste management.

In the Outer Western Carpathians, previous paleomagnetic studies reported minor and differentiated tectonic rotations of particular thrust-belt segments. Alternatively, large magnitude vertical axis rotations of entire nappes and thrust sheets of regional extent were inferred from the study of Upper Eocene – Oligocene rocks. Paleomagnetic data obtained from the red Weglowka Marls (Senonian to Eocene) indicate that the NE segment of the Outer Western Carpathians was not significantly rotated with respect to the stable European Platform. The Weglowka Marls record a primary magnetization carried by hematite, with intervals affected by secondary reduction processes, associated with reduction to magnetite and pyrhottite. The characteristic remanent magnetization displays dual polarity, passes the fold-test and shows paleomagnetic declinations similar to those expected for stable parts of the European Platform. Anisotropy of magnetic susceptibility (AMS) data show that the analyzed rocks were affected by significant compaction; however they record only a minor tectonic overprint, implying weak internal strain associated with folding and thrusting.

Several tectonic processes have been proposed to be important in the Alpine to the recent evolution of the Polish Outer Carpathians, i.e., Paleogene–Neogene thrusting, post-thrusting extension, Quaternary reactivation of compression. This work tests the effect of these processes on exhumation of the wedge, in order to verify their timing and relative role in shaping the Polish Outer Carpathians. AFT, AHe and ZHe analyses were performed on samples collected along the study region. This allowed the reconstruction of their post-depositional minimum heating, depth of burial and timing of cooling and exhumation. After deposition samples from the innermost units were heated up to temperatures of ca. 60–120 °C (ca. 4–9 km), whereas samples from the outer units were heated to temperatures lower than 60 °C (ca. 4 km). Cooling and exhumation occurred progressively later from west to east (between ca. 25 and 10 Ma in the western sector, between ca. 15 and 5 Ma in the eastern sector). These results have been put in relationship with single structural features to understand the relative role of thrusts and normal faults. In the eastern sector of the study region samples at the footwall of significant normal faults show a higher degree of reset and younger ages than samples located at the hangingwall. This implies that, in this sector, extensional tectonics played an important role in exhumation. However, proper tectonic exhumation only had a minor role, the major exhumation mechanism being erosion, which is enhanced in the footwalls and reduced in the hangingwalls. In the western sector of the Polish Outer Carpathians only in few cases evidence of enhanced erosion to the footwall of major normal faults could be observed based on the present data. In this region the wedge exhumed mainly as a response to thrusting and normal faulting only played a minor role, locally modifying the pattern of erosion. Finally no major exhumation events occurred after Miocene, pointing to a minor relevance of recent compression. Unreset ZHe dates were used to estimate exhumation of source rocks through the ZHe PRZ and to outline the provenance of sediments forming the Polish Outer Carpathians. Exhumation occurred both in response to the Variscan (Late Devonian to Triassic) and Alpine (Late Jurassic to Early Paleocene) orogeneses, suggesting sedimentary provenance both from the southern margin and from the basement heights within the Outer Carpathian basin.

In this work we document a well-exposed example of Late Cretaceous syn-sedimentary extensional tectonics occurring in carbonates of the Apennine Platform of the southern Apennines. Soft-sediment deformation meso-structures and breccia bodies in the hanging wall of hundred metres long faults record a Late Cretaceous extensional stage along NE-SW striking faults. Such a trend becomes about E-W when Cenozoic vertical axis rotation is removed, being consistent with similar structures previously reported in other domains of the southern portion of Adria. This study contributes to identify a regional Albian to Late Cretaceous extensional pulse in the southern portion of Adria, which is proposed to be responsible for the drowning of several sectors of the continental bridge that connected Africa with Adria until Late Cretaceous times, and for the development of an E-W elongated basin that connected the Ligurian and Ionian seas from Late Cretaceous onwards.

The Diamante-Terranova unit is an oceanic-derived element within the thrust and nappe structure of the northern sector of the Calabrian Arc. Its metamorphic and structural signature reveals a long history of SE dipping subduction and collision-related deformation of an oceanic lithospheric section underlying the narrow Diamante-Terranova basin. The deformation history of the Diamante-Terranova unit may be related to three main tectonic phases. The first one is characterized by a structural association which includes features that developed during a progressive deformation related to the evolution of a deep-seated shear zone. Kinematic indicators characterizing subduction-related structures clearly show a top-to-the-northwest sense of overthrust shear. The second tectonic phase that can be recognized in the area is characterized by structures that may be related to the onset of shear deformation induced by a postcollisional northeastward motion of the overriding plate. The third tectonic phase is recorded by brittle features related to the latest tectonic events affecting the Calabrian Arc during the opening of the Tyrrhenian Sea. Shear sense indicators and available radiometric and stratigraphic information, together with plate kinematic data, allowed us to infer the time evolution of this sector of the Calabrian Arc and to assess that the Diamante-Terranova unit cannot be considered as an “Eoalpine” element since its deformation, related to subduction-collision processes, occurred prior to the end of the Cretaceous.

The tectonic evolution of Alpine Corsica and surrounding areas is described through a series of plate reconstructions from the onset of the Alpine convergence in the early Cretaceous (~ 120 Ma) to the early Miocene (~ 19 Ma). The southward subduction of Eurasian lithosphere (Alpine Tethys) beneath Adria and Iberia, and the subduction of Ligure–Piemontese Ocean (Iberian plate) beneath the Adria margin, led to the formation of a trench–trench–trench triple junction close to the northern margin of Adria. During the first phase, from the early Aptian (~ 120 Ma) to the Campanian (~ 75 Ma) the northeastern oceanic part of the Iberian plate subducted beneath Adria along an intra‐oceanic subduction zone between Corsica and Adria. This trench was linked to the eastern Iberian convergent margin (having opposite polarity) through a transform fault. Starting from the Campanian and until the Oligocene (~ 34 Ma) oceanic and transitional crust was obducted onto Hercynian Corsica and Eurasia, giving rise to HP metamorphism within the subducted continental crust. From ~ 40 Ma to the early Oligocene (~ 33 Ma) the onset of continental collision in the Alpine area led to thickening of the subducting Eurasian margin through the formation of the European lower crustal wedge. Finally, from the early Oligocene (~ 33 Ma) to the early Miocene (~ 19 Ma), during the rotation of the Corsica and Sardinia blocks, the Pyrenean–Alpine belt lost its continuity in Gulf of Lyon and Provencal area, while the western Adriatic margin (Apennine domain) became a left‐lateral transpressive belt linking the western Alpine chain with the Calabrian Arc.

In the last decades, multidiscipline investigation of the Apennine mountain belt of peninsular Italy has provided fundamental insights into the genesis and evolution of wedge-top basins. In this study, we focus on shallow-water to conti- nental, Pliocene-Quaternary basins that formed on top of the southern Apennine allochthonous wedge after its emplacement onto a large foreland carbonate platform domain (Apulian Platform). The wedge-top basins analyzed in this study are mostly asymmetric, being bounded to the north by a normal fault showing evidence of synsedimentary activity. The basin succes- sions are generally deformed by open folds and reverse faults resulting from shortening coeval with the sedimentation of the Lower Pliocene to lower-middle Pleistocene, upper part of the basin fill. Anisotropy of magnetic susceptibility data from the basin successions are consistent with a basin evolution characterized by an initial stage of tectonic subsidence controlled by roughly north-northwest-south-southeast-oriented extension, followed by southwest-northeast shortening active during subse- quent basin filling. The latter shortening is marked by a dominant northwest-southeast mean trend of the magnetic lineation obtained from most sites in the study area and is interpreted as a result of upward propagation of deep-seated deformation (tectonic inversion) taking place within the buried Apulian Platform sitting in the footwall to the allochthonous wedge. There- fore, our results emphasize a complex interplay of different tectonic processes controlling wedge-top basin development. Resume : Au cours des dernieres decennies, une etude multidisciplinaire de la chaine de montagnes des Apennins dans la peninsule italienne a donne des apercus de la genese et de l'evolution des bassins sur le prisme d'accretion « wedge-top ba- sins ». Dans cette etude, nous ciblons les bassins d'eau peu profonde a continentaux, datant du Pliocene-Quaternaire, qui se sont formes sur le dessus du prisme allochtone du sud des Apennins, apres sa mise en place sur un vaste domaine de plate- forme de carbonate d'avant-pays (la plate-forme apulienne). Les bassins sur le prisme d'accretion analyses dans la presente etude sont surtout asymetriques, puisqu'ils sont delimites au nord par une faille normale montrant des evidences d'activite syn-sedimentaire. Les successions de bassins sont generalement deformees par des plis ouverts et des failles inverses prove- nant d'un retrecissement contemporain de la sedimentation du Pliocene inferieur au Pleistocene inferieur moyen dans la par- tie superieure du remplissage du bassin. L'anisotropie des donnees de susceptibilite magnetique provenant des successions de bassin concorde avec une evolution du bassin caracterisee par un stade initial de subsidence tectonique controlee par une extension a orientation generale nord-nord-ouest-sud-sud-est, suivie d'un retrecissement sud-ouest-nord-est actif durant le remplissage subsequent du bassin. Ce dernier retrecissement montre une tendance moyenne dominante nord-ouest-sud-est de la lineation magnetique obtenue de la plupart des sites dans le secteur a l'etude et il est interprete comme le resultat d'une propagation vers le haut d'une deformation situee en profondeur (inversion tectonique) qui s'est produit dans la plate-forme apulienne enfouie se trouvant dans l'eponte inferieure du prisme allochtone. Nos resultats soulignent donc une interaction complexe entre les differents processus tectoniques qui controlent le developpement des bassins sur les prismes d'accretion. (Traduit par la Redaction)

In order to obtain new insights into the active tectonic setting of the Italian territory and surrounding regions, the Multiple Inverse Method (MIM) has been applied to the analysis of fault plane solutions from more than 700 earthquakes with M w ≥ 4. The active stress field in the top 40 km of the lithosphere has been defined for four 10 km-thick layers, each including 810 square cells of 1.5° side. The obtained stress field maps point out that most of the upper crustal seismicity of the Western and Central Alps is controlled by a strike-slip regime, which is dominant also in part of the Dinarides, Albanides and Hellenides and in a large sector encompassing eastern Sicily and the Malta area to the eastern Tunisia offshore. On the other hand, the well-known extensional belt occurring in the interior of the Apennines appears to extend well beyond the backbone of Italy, potentially reaching the outer foothills of the northern Marche region, while the adjacent Adria block (extending to the eastern Po Plain and the outer Dinarides) sticks out as a major area characterised by dominant thrust faulting in the upper crust. A similar regime characterises also a large sector of the western Tyrrhenian Sea, from NE Tunisia through western Sicily and the west coast of Sardinia, to the Provence coast. Besides lateral variations, our analysis also points out a significant vertical heterogeneity of the stress field, the deeper levels (20 to 40 km) investigated in this study being characterised by dominant horizontal maximum compression even in areas of upper crustal extension. The application of the MIM to a large seismological dataset, providing basic information for the compilation of active stress maps, contributes to a better understanding of active tectonic processes and may be used for improving seismotectonic zoning and reservoir management.

This paper includes the results of the application of novel methodologies for the statistical analysis of tensile fracture attributes (spacing, density, and aperture). The statistical methods have been applied to a fractured Lower Cretaceous carbonate succession cropping out in the Sorrento Peninsula (Naples area, Italy), representing a geological analogue of buried reservoirs of southern Apennines major oil fields. As fracture networks (observable from outcrop to the crystal scale) can significantly affect the hydraulic behavior of a fractured reservoir, the definition of appropriate models of fracture spacing and aperture probability distribution at various scales represents an important goal of structural analysis. In order to achieve such an objective, sampling has been carried out at different scales, by means of traditional scan lines at outcrop, as well as micro-scan lines carried out both by a digital micro-camera (50×) and by the optical microscope (200×). Fracture spacing and density analysis are mainly aimed at establishing the characteristics of joint spatial distribution over a range of scales. Aperture analysis is aimed at verifying that the aperture cumulative frequency is described by a power law and, in the latter instance, to provide an effective method for a more precise determination of the exponent of the power law. Finally, new expressions are provided, in closed form, in order to calculate the confidence interval of the power-law exponent. The proposed criteria provide handy and effective methods for a significantly improved statistical analysis of fracture attributes.

Syn-orogenic sediments provide fundamental information on the timing and modes of deformation in fold and thrust belts. In this study, biostratigraphic and structural analyses on syn-orogenic depos...

An integration of seismological data with geological and geomorphological information aided by seismic interpretation was performed to characterise the Quaternary tectonic evolution of the Metauro River basin area (northern Marche) and adjacent off-shore sector of the external Northern Apennines. On-shore, along the Adriatic coast, the youngest age of thrusting and folding post-dates the Early-Middle Pliocene, while Pleistocene deposits appear to be, at least in part, not involved in the deformation. Recent (i.e. post-thrusting) tectonic structures have been recognised both in pre-Quaternary substratum rocks and in Upper Quaternary continental deposits (Upper Pleistocene terrace alluvium, Upper Pleistocene–Holocene slope deposits). These faults are all compatible with a WSW–ENE oriented extension. In the Metauro River basin area, preserved flights of stream terraces have been categorised according to the presence or absence of alluvial suites in relationship to each terrace level. Here, based on both the heights above the valley floor and the areal distribution of stream terraces, a generalised vertical tectonic uplift can be inferred, particularly during the Middle–Late Pleistocene. Moreover, the along-valley distribution of stream terraces provides further constraints on the age of thrusting and folding. In fact, the reconstructed terrace-levels are substantially parallel, and no evidence for any significant deformation by fold activity has been recognised. Local deformation displayed by both terrace surfaces and alluvial/slope-waste deposits suggests, instead, the intervening of some minor differential movements associated with the generalised uplift and/or to Middle–Late Pleistocene normal faulting. Their occurrence appears anyhow to be unrelated with the pattern of folds and associated thrusts. The present-day seismic activity of the study area was considered by analysing 83 seismic events that occurred from 1987 to 2000. The epicentre distribution is very scattered, and depths are generally comprised within the first 20 km of the crust, clustering between 0 and 15 km. Most of the events have magnitude

The active geodynamic setting of the Northern Apennines is characterised by extension in the axial zone of the chain, and by a more complex tectonic behaviour in the frontal part of the belt. In the latter sector, moderate seismicity occurs, displaying compressional, strike-slip and extensional focal plane solutions with variably oriented P and T axes. For this area, a review of available geological and geophysical data has been integrated by the analysis of seismic reflection lines calibrated with deep well logs. This study confirms that, as already suggested by some previous workers, thrusting and related folding in the study area ceased in Early Pleistocene times. This feature is in contrast with the hypothesis of active thrusting related to a subducting lithospheric slab beneath the chain—an issue which is largely debated based on available geophysical information. Our analysis shows that the Northern Apennines are characterised by an active tectonic setting which is similar to that of the central and southern portions of the belt. These areas all display a Late Quaternary inactivity of the thrust front. NE–SW oriented extension (perpendicular to the strike of the orogen) is well established in their axial zones, whereas a less homogeneous stress field characterises their external sectors and the adjacent foreland. Within this framework, the seismotectonic behaviour of the Northern Apennines—and probably of the whole Italian peninsula between the Po Plain and the Southern Apennines (north of the Calabrian Arc)—may be interpreted as essentially controlled by two main processes. The first of them involves tectonic uplift, possibly related with slab detachment and associated unbending of the foreland plate. The second process consists of a present-day northwestward motion of the Adria block with respect to stable Europe.

Paleomagnetic analyses of Upper Miocene synorogenic strata from the Marche–Romagna foothills of the Northern Apennines have been integrated with detailed structural work and structural modelling to gain new insights on the processes of tectonic rotation in fold-and-thrust belts. Measured paleomagnetic declinations indicate two different patterns from adjacent areas. Paleomagnetic declinations from the coastal (i.e. northeastern) sites show a limited amount (mean value of 11°) of anticlockwise rotation compared with the expected Late Miocene direction, whereas large anticlockwise rotations (mean value of 63°) are detected from more internal (southwestern) sites. The large amount of mean differential rotation, detected from two adjacent areas located in the same strike-length position of the thrust belt, suggests that processes other than large-scale lateral bending of the orogen played an important role. Although no major faults are exposed that can account for such large rotations, the two areas of contrasting rotation patterns are notably located in structurally different portions of the thrust belt. The coastal sites lie in the frontal part, which is characterized by broad folds and relatively low-displacement, basement-involved (‘thick-skinned’) thrusts. On the other hand, most southwestern sites overly an oblique ramp segment of the major thrust fault (Cesana Thrust) occurring in the internal area. Displacement of the detached sedimentary cover across this thrust ranges from a maximum of about 4 km (frontal ramp area) to zero at the northwestern termination of the oblique ramp segment mentioned above. Cross-section balancing and structural modelling carried out independently from paleomagnetic analysis indicates that limited (10–12°) rotations can be associated with laterally variable displacements across the external thrusts, whereas much larger rotations (in excess of 45°) must be attributed to complex strain patterns and rotations in the northwestern tip zone to the Cesana Thrust. Although a uniform counterclockwise rotation of an entire sector of the thrust belt cannot be ruled out, our results indicate that this is quite unlikely, and anyway would not exceed a maximum of approximately 12° for the study area. Therefore, large-scale lateral bending of the chain appears to be subordinate, in controlling tectonic rotations about a vertical axis, with respect to the role played by lateral/oblique ramps, non-cylindrical folding, and displacement gradients in ‘thick-skinned' or detachment-dominated thrusting. As these features are common in most fold-and-thrust belts, our results might be of interest in the application and interpretation of paleomagnetic studies in similar structural settings elsewhere.