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Apatite fission track (AFT) and (U-Th)/He (AHe) thermochronometry are applied to constraint the thermal history of the basement rock forming the Peloritani Mountains in northeast Sicily, Italy. AFT ages range between 29.0 [+ or -] 5.5 Ma and 5.5 [+ or -] 0.9 Ma while AHe ages vary from 19.4 Ma to 3.3 Ma. Most AFT ages are younger than the overlying terrigenous sequence that, in turn, postdates the main orogenic phase. Through the coupling of the thermal modeling with the stratigraphic record, a middle Miocene thermal event is revealed. This event affected an inner-intermediate portion of the Peloritani Mountains and is confined by the distribution of the AFT ages < 15 Ma. The U-shaped pattern of AFT ages along N-S transects across the mountain chain is consistent with burial below a thrust stack that is a few km thick, created by an out-of-sequence thrusting phase that affected the inner portion of the belt. The tectonic load was then removed initially by erosion enhanced by the high relief at 10-7 Ma. The difference between young AFT and AHe ages is used to infer a rate of exhumation of 0.3 mm/yr for this stage. The gap between the youngest AHe ages and the sedimentary record above indicate a final exhumation stage with increasing rates of denudation (1-3 mm/yr) since the Pliocene times due to extensional tectonics. doi: 10.1029/2009TC002659.

[1] Recent geodetic data are compatible with NNE-SSW tectonic extension at a rate of ~5 mm/yr in Sicily, southern Italy, within a broader region of net active compression along the Nubian plate margin (northern Africa). The structures that accommodate such extensional regime and its cause are still unknown. From field structural surveys and seismological analyses, the geometry, kinematics, structural architecture, and seismic potential of an extensional seismic zone linking Cefalu and Mount Etna in central eastern Sicily are defined. The zone includes high-angle WNW striking normal and right-lateral strike-slip faults and subordinate north and NNE striking strike-slip faults either right or left lateral. The occurrence of small discontinuous faults and the absence of related depressions and sedimentary basins suggest that the extensional regime is still in an incipient stage. The ongoing seismic activity possibly reactivates preexisting faults. Instrumentally and historically recorded earthquakes are lower than about 6 in magnitude, and destructive events are historically unknown since at least 1300 A.D. This apparent upper bound of earthquake magnitudes is consistent with the maximum magnitude values estimated from the length of the longest mapped faults and sources of seismic swarms, which all together suggest a value between 6 and 6.5 as the maximum expected magnitude that can be proposed at the present stage of investigation for earthquakes in the study area. Lateral extension on preexisting faults and upwelling of melt mantle material beneath Mount Etna are considered viable processes to explain, at least in part, the active extensional tectonics along the Cefalu-Etna seismic zone. Strike-slip seismic faulting beneath Mount Etna may be part of a previously proposed diffuse transfer zone affecting northeastern Sicily and including the Tindari Fault. Citation: Billi, A., D. Presti, B. Orecchio, C. Faccenna, and G. Neri (2010), Incipient extension along the active convergent margin of Nubia in Sicily, Italy: Cefalu-Etna seismic zone, Tectonics, 29, TC4026, doi: 10.1029/2009TC002559.

[1] The Neogene tectonics of the central Mediterranean are related to the subduction and trench rollback of the Ionian basin under Eurasia, causing the opening of the Liguro-Provencal and Tyrrhenian back-arc basins and the formation of the Calabrian accretionary wedge. The Calabrian accretionary wedge is a partially submerged accretionary complex located in the Ionian offshore and laterally bounded by the Apulia and Malta escarpments. While the history of the back-arc extension process is fairly well defined, the structure and evolution of the wedge are still poorly known. We have analyzed and interpreted the available reflection multichannel and single-channel seismic profiles in the Ionian offshore and integrated them with other geological and geophysical data acquired in the last 40 years. Here we present unpublished seismic profiles to provide a new map of the tectonic structure of the Ionian offshore and to define the structure of the wedge and its evolution during the last 15 Myr. Our reconstruction points out that the Messinian salinity crisis represents an important break in the evolution of the wedge, as the basal decollement ramps up onto the Messinian salt deposits, producing a dramatic and fast forward propagation of the frontal thrust and resulting underplating of the underlying crustal Ionian sequence during progressive trench rollback. Our results provide new insight into the style of accretion in a weakly converging setting, which is typical for the Mediterranean region. Citation: Minelli, L., and C. Faccenna (2010), Evolution of the Calabrian accretionary wedge (central Mediterranean), Tectonics, 29, TC4004, doi: 10.1029/2009TC002562.

[1] We report new paleomagnetic and structural data from late Cretaceous to Mio-Pliocene continental sandy/silty sedimentary rocks from the Eastern Cordillera (central Andes). Here, N-S to NNE-SSW ridges hosting Paleozoic basement and upper Cretaceous continental red beds overthrust thick adjacent Cenozoic basins. Pretilting (and likely primary) reliable directions gathered at 15 sites document 45.9 [degrees] [+ or -] 9.4, 30.1 [degrees] [+ or -] 23.9 [degrees], and 15.4[degrees] [+ or -] 19.3 [degrees] clockwise (CW) rotations with respect to South America occurring after the late Cretaceous (~80 Ma), Oligo-Miocene (20-30 Ma), and late Miocene-Pliocene (5-10 Ma), respectively. Conversely, four upper Cretaceous sites from the walls of a N-S left-lateral strike-slip fault (Yavi-Abra Pampa fault) yield a null rotation. About 20 km to the west, flower structures and subvertical syntectonic strata dated at 14.26 [+ or -] 0.19 Ma are exposed along the subparallel Abra Moreta left-lateral strike-slip fault. Relying on data from the literature on the period when deformation began, we suggest that since Eo-Oligocene times (30-40 Ma) the Eastern Cordillera has undergone a regional CW rotation of 40[degrees]-50[degrees], synchronous with crustal shortening and large-scale bending of the Andean salient. The CW rotation is possibly still active today, as documented by regional GPS data from the Andes. Since ~15 Ma ago, the activity of N-S left-lateral strike-slip faults induced counterclockwise rotations along the fault zone, locally annulling the regional CW rotation. In agreement with a previous model, we speculate that mid-Miocene strike-slip activity accommodated the progressive southward spreading of the Altiplano-Puna high-altitude plateau, laterally migrating from the overthickened crustal region of the salient apex. Citation: Maffione, M., F. Speranza, and C. Faccenna (2009), Bending of the Bolivian orocline and growth of the central Andean plateau: Paleomagnetic and structural constraints from the Eastern Cordillera (22-24[degrees]S, NW Argentina), Tectonics, 28, TC4006, doi: 10.1029/2008TC002402.

[1] Northern Victoria Land is located at the boundary between an extended, presumably hot, region (West Antarctic Rift System) and the thick, possibly cold, East Antarctic craton. The style and timing of Tertiary deformation along with relationships with the magmatic activity are still unclear, and contrasting models have been proposed. We performed structural and morphotectonic analyses at the NE termination of northern Victoria Land in the Admiralty Mountains area, where the relationship between topography, tectonics, and magmatism is expected to be well pronounced. We found evidence of two subsequent episodes of faulting, occurring concurrently with the Neogene McMurdo volcanism. The first episode is associated with dextral transtension, and it is overprinted by extensional tectonics during the emplacement of large shield alkaline volcanoes. Upper mantle seismic tomography shows that the extensional regime is limited to regions overlying a low-velocity anomaly. We interpret this anomaly to be of thermal origin, and have tested the role of large-scale upwelling on lithosphere deformation in the area. The results of this integrated analysis suggest that the morphotectonic setting of the region and the magmatism is likely the result of upwelling flow at the boundary between the cold cratonic and the hot stretched province (WARS), at work until recent time in this portion of the northern Victoria Land.

[1] New estimates of trench migration rates allow us to address the dynamics of trench migration and backarc strain. We show that trench migration is primarily controlled by the subducting plate velocity [V.sub.sub], which largely depends on its age at the trench. Using the hot and weak arc to back-arc region as a strain sensor, we define neutral arcs characterized by the absence of significant strain, meaning places where the forces (slab pull, bending, and anchoring) almost balance along the interface between the plates. We show that neutral subduction zones satisfy the kinematic relation between trench and subducting plate absolute motions: [V.sub.t] = 0.5[V.sub.sub] - 2.3 (in cm [a.sup.-1] ) in the HS3 reference frame. Deformation occurs when the velocity combination deviates from kinematic equilibrium. Balancing the torque components of the forces acting at the trench indicates that stiff (old) subducting plates facilitate trench advance by resisting bending. Citation: Lallemand, S., A. Heuret, C. Faccenna, and F. Funiciello (2008), Subduction dynamics as revealed by trench migration, Tectonics, 27, TC3014, doi:10.1029/ 2007TC002212.

[1] We present lithospheric-scale analog models, investigating how the absolute plates' motion and subduction of buoyant oceanic plateaus can affect both the kinematics and the geometry of subduction, possibly resulting in the appearance of flat slab segments, and how it changes the overriding plate tectonic regime. Experiments suggest that flat subductions only occur if a large amount of a buoyant slab segment is forced into subduction by kinematic boundary conditions, part of the buoyant plateau being incorporated in the steep part of the slab to balance the negative buoyancy of the dense oceanic slab. Slab flattening is a long-term process (~10 Ma), which requires the subduction of hundreds of kilometers of buoyant plateau. The overriding plate shortening rate increases if the oceanic plateau is large enough to decrease the slab pull effect. Slab flattening increases the interplate friction force and results in migration of the shortening zone within the interior of the overriding plate. The increase of the overriding plate topography close to the trench results from (1) the buoyancy of the plate subducting at trench and (2) the overriding plate shortening. Experiments are compared to the South American active margin, where two major horizontal slab segments had formed since the Pliocene. Along the South American subduction zone, flat slab segments below Peru and central Chile/NW Argentina appeared at ~7 Ma following the beginning of buoyant slab segments' subduction. In northern Ecuador and northern Chile, the process of slab flattening resulting from the Carnegie and Iquique ridges' subductions, respectively, seems to be active but not completed. The formation of flat slab segments below South America from the Pliocene may explain the deceleration of the Nazca plate trenchward velocity. Citation: Espurt, N., F. Funiciello, J. Martinod, B. Guillaume, V. Regard, C. Faccenna, and S. Brusset (2008), Flat subduction dynamics and deformation of the South American plate: Insights from analog modeling, Tectonics, 27, TC3011, doi:10.1029/2007TC002175.

[1] The Hyblean Plateau in southeastern Sicily, Italy, consists of an isolated and elevated forebulge structure formed since the early Miocene time by bending the foreland lithosphere below the advancing Maghrebian thrust-fold belt. The Hyblean forebulge is presently located in front of an orogenic recess and partly surrounded by two orogenic salients. We analyzed magnetic (anisotropy of magnetic susceptibility) and structural (joints, faults, slickenside lineations, and bed attitudes) fabric data from Neogene carbonate rocks exposed atop the Hyblean forebulge. Results showed unidirectional fabrics developed in response to a NWSE extension at the end the of early Miocene time and beginning of middle Miocene time, and duple-to-multiple fabrics developed in response to major NWSE and NE-SW extensions from the Langhian time onward. We interpreted these results as the evidence for the growth of a doubly plunging forebulge due to the presence of foreland crustal heterogeneities, which enhanced differential retreating processes of the foreland along the subduction zone and the subsequent formation of orogenic salients and recesses. A semianalytical model shows that the observed brittle deformations potentially involved a significant thickness of the carbonate sedimentary cover, thereby reducing the lithosphere flexural rigidity and enhancing its bending aptitude. Citation: Billi, A., M. Porreca, C. Faccenna, and M. Mattei (2006), Magnetic and structural constraints for the noncylindrical evolution of a continental forebulge (Hyblea, Italy), Tectonics, 25, TC3011, doi: 10.1029/2005TC001800.

[1] The Tindari Fault System (southern Tyrrhenian Sea, Italy) is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab. Onshore structural data, an offshore seismic reflection profile, and earthquake data are analyzed to constrain the present geometry of the Tindari Fault System and its tectonic evolution since Neogene, including the present seismicity. Results show that this zone of deformation consists of a broad NNW trending system of faults including sets of fight-lateral, left-lateral, and extensional faults as well as early strike-slip faults reworked under late extension. Earthquakes and other neotectonic data provide evidence that the Tindari Fault System is still active in the central and northern sectors and mostly accommodates extensional or right-lateral transtensional displacements on a diffuse array of faults. From these data, a multiphase tectonic history is inferred, including an early phase as a right-lateral strike-slip fault and a late extensional reworking under the influence of the subduction-related processes, which have led to the formation of the Tyrrhenian back-arc basin. Within the present, regional, geodynamic context, the Tindari Fault System is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments, these tectonic compartments relating to the complex processes of plate convergence occurring in the region. The Tindari Fault System might also be included in an incipient, oblique-extensional, transfer zone linking the ongoing contractional belts in the Calabrian-Ionian and southern Tyrrhenian compartments. Citation: Billi, A., G. Barberi, C. Faccenna, G. Neri, F. Pepe, and A. Sulli (2006), Tectonics and seismicity of the Tindari Fault System, southern Italy: Crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab, Tectonics, 25, TC2006, doi:10.1029/2004TC001763.

[1] 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 [sup.40]Ar/[sup.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. INDEX TERMS: 1035 Geochemistry: Geochronology: 3660 Mineralogy and Petrology: Metamorphic petrology: 8100 Tectonophysics; 8102 Tectonophysics: Continental contractional orogenic belts: 8109 Tectonophysics: Continental tectonics--extensional (0905); KEYWORDS: compression/ extension, orogenic wedges, HP/LT metamorphism. Mediterranean region, Calabria.

[1] The western Mediterranean subduction zone (WMSZ) extends from the northern Apennine to southern Spain and turns around forming the narrow and tight Calabrian and Gibraltar Arcs. The evolution of the WMSZ is characterized by a first phase of orogenic wedging followed, from 30 Ma on, by trench retreat and back-arc extension. Combining new and previous geological data, new tomographic images of the western Mediterranean mantle, and plate kinematics, we describe the evolution of the WMSZ during the last 35 Myr. Our reconstruction shows that the two arcs form by fragmentation of the 1500 km long WMSZ in small, narrow slabs. Once formed, these two narrow slabs retreat outward, producing back-arc extension and large scale rotation of the flanks, shaping the arcs. The Gibraltar Arc first formed during the middle Miocene, while the Calabrian Arc formed later, during the late Miocene-Pliocene. Despite the different paleogeographic settings, the mechanism of rupture and backward migration of the narrow slabs presents similarities on both sides of the western Mediterranean, suggesting that the slab deformation is also driven by lateral mantle flow that is particularly efficient in a restricted (upper mantle) style of mantle convection. INDEX TERMS. 8120 Tectonophysics: Dynamics of lithosphere and mantle general; 8102 Tectonophysics: Continental contractional orogenic belts; 8158 Tectonophysics: Plate motions--present and recent (3040); 8150 Tectonophysics: Plate boundary--general (3040); KEYWORDS: Mediterranean, subduction, arcuate belt, tomography. Citation: Faccenna, C., C. Piromallo, A. Crespo-Blanc, L. Jolivet, and F. Rossetti (2004), Lateral slab deformation and the origin of the western Mediterranean arcs.

Research is presented concerning the use of 40Ar/39Ar geochronology, petrographical and structural techniques to investigate the metamorphic and main structural breaks of the Sila Piccola Massif in Calabria, Italy.

Research is presented concerning the tectonic events occurring during the Africa-Eurasia collision 30- to 25-million-years ago. The effect of the collision on geological events in the Mediterranean area are discussed.