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High enthalpy geothermal fields are typically associated with magmatic intrusions providing the heat source that makes the system working. To identify and locate these features, geothermal exploration generally uses expensive, time-consuming approaches that could also require complex logistics. Here we present the result of a pilot study carried out in the well-known Larderello-Travale geothermal field (Tuscany, Italy), exploring the possibility of an advantageous use of low temperature thermochronology to obtain useful information implementing the geothermal exploration workflow. The majority of the collected samples (except one retaining the apatite fission-track age of undisturbed, or almost undisturbed country rocks) cluster in a close time span ranging between 3.1±0.8 and 1.9±1.1 Ma, which clearly matches the known ages of magmatic bodies in the region. We propose that this approach can contribute to the identification of sectors recently affected by thermal perturbations that could have led to the development of hydrothermal systems. This approach has allowed us to achieve clues for the presence of subsurface magmatic intrusions even in areas where currently there are no direct indications. Given the small number and distribution of analyzed samples, our contribution represents a first attempt that demonstrates the potentiality of the method in geothermal exploration, but that needs to be verified by further studies involving a larger sampling density. Overall, our results suggest how low temperature thermochronology can be a powerful, fast, and cost-effective tool for geothermal exploration, to be used jointly with the classical methods.

During the evolution of extensional basins, the area interested by tensile stresses is commonly characterized by volcanic products with mantle-sourcing geochemical imprint. In this context, erosion of the rift shoulders and sedimentation in the basin can affect the stress and thermal fields at depth thereby promoting or inhibiting rock melting, but the tectonics/climatic boundary conditions that allow for such surface forcing on extensional magmatism are elusive.Here, we use a bi-dimensional coupled thermo-mechanical and landscape evolution numerical model to quantify melt production changes in slowly stretching rift basins due to changes in deposition rates. The model combines visco-elasto-plastic deformation of the lithosphere and underlying mantle during extension, partial rock melting and linear hillslope diffusion of the surface topography. The parametric study covers a range of slow extension rates, crustal thicknesses, mantle potential temperatures and diffusion coefficient (corresponding to sedimentation rates of 0.01-0.1-1 mm/y).We use the Victoria Land Basin (VLB) on the western side of the Ross Sea Embayment in Antarctica, one of the largest, long-lasting and slowest continental rifts on Earth, as a natural term of comparison for our modeling results. We particularly aim at quantifying the contribution of surface processes to rock melting in slow extensional settings, so to assess the sensitivity of extensional magmatic systems to surface processes.The VLB area is characterized by several episodes of extension from the Cretaceous to recent time, resulting in wide rifting across the West Antarctic Rift Region (WARS), and a more localized narrow rift in the VLB. The multi-phase rifting behavior of the WARS is described by seismic reflection data displaying up to 14 km-thick sediment infilling from the Lower Paleogene in the VLB and the wide to narrow rift transition marked by Ross Sea unconformities. Miocene climate cooling deeply affected the production and transport of sediments in the basin with a tenfold decrease in sedimentation rate from the M1 glaciation to the post-Mid-Miocene Climate Transition well-visible in the sedimentary record of the youngest basin, the Terror Rift. The volcanic features in the VLB and its flanks are represented by the Meander Intrusive Complex (48 to 18 Ma) and the McMurdo Volcanic Group (since 18 Ma and still active).Our models reproduce the 200 km-extension of the VLB and the lithospheric necking with up to 20 Ma of asthenospheric melt production before oceanization. Surface processes inhibit mantle decompression melting and delay the crust breakup. These results suggest that the VLB magmatic history has been significantly affected by sediment deposition within the basin, which acted as a primary melt-controlling parameter. Mutual feedbacks between surface and deep-seated processes in the VLB and other extensional basins with different tectonostratigraphic histories are also supported by our models.

This research project concerns the study, analysis and dating of obsidian flows on the island of Lipari, in relation to the population of the Aeolian Islands, during the Neolithic period.The collection, processing and diffusion of Lipari obsidian characterise the Neolithic population of Lipari and the entire Mediterranean. By improving the knowledge of supply methods in the territory, it will be possible to formulate hypotheses on the chronology of the sources, the ways of collecting the raw material and on the mobility of the Neolithic communities in the Aeolian Islands. The scientific research is divided into two main topics: the first concerns the analytical and methodological aspects of archaeological and geological studies of Lipari obsidian; the second, the formation of obsidian at Lipari, their sources and lithological characteristics. Throughout the duration of this study we will perform new age determinations of Neolithic obsidian artefacts and geological samples, directly with the method of fission track, and indirectly dating paleo soils using the radiocarbon method.

The Iranian Plateau represents a NW-SE striking, elongated, elevated (mean elevation of ~1.8 km), arid, mostly internally drained (~65 % of its area) and aseismic morphotectonic feature of the Arabia-Eurasia collision zone. With a crustal thickness up to ~65 km, the southern plateau margin includes the High Zagros Mountains and the plate suture zone. The northern plateau margin, instead, consists of the Urumieh-Dokhtar Magmatic Zone and the western Alborz-Talesh Mountains from SE and NW Iran, respectively, which exhibit a crustal thickness ranging from 40 to 50-55 km. The plateau interior is characterized by a low-topographic relief morphology with six major, mostly internally drained intermontane sedimentary basins. The backbones of these basins are mainly represented by the Sanandaj-Sirjan Zone. Plateau uplift commenced after ~17 Ma, as documented by the occurrence of Lower Miocene shallow-water marine sediments of the Qom Formation within the plateau interior. Although the Iranian Plateau represents the second largest collisional plateau after Tibet, the chronology of the events and the mechanisms that built it are poorly constrained.In this study, we combine a new low-temperature thermochronologic dataset including apatite fission- track and apatite (U-Th-Sm)/He ages from the northern plateau sectors and its interior with structural and stratigraphic data from different intermontane basins and literature thermochronology data. Combined, this information shows that after a mild phase of post late Eocene contractional deformation, collisional deformation started in the early Miocene along the plate suture zone to the south and in the middle Miocene (~16 Ma) in the Talesh-Alborz Mountains to the north. Subsequently, around 12-10 Ma, deformation jumped in the plateau interior over a rather large area including the Urumieh-Dokhtar and Sanandaj-Sirjan zones, apparently without a specific pattern of propagation. Upper plate deformation occurred mostly through the reactivation of older NE-dipping structures that led to the topographic growth of several mountain ranges spanning a wavelength of ~50-60 km. This was associated with the compartmentalization of the upper plate and the development of different intermontane basins. There, basin filling processes inhibited intrabasinal deformation and faulting along the major range-bounding faults producing the smoothed, low-relief landscape typical of an orogenic plateau.Combined, these results provide new information concerning the mechanisms and the timing of the lateral, orogen-perpendicular, growth of the Iranian Plateau

Northern Victoria Land constitutes the Pacific terminus of the Transantarctic Mountains (TAM) on the western shoulder of the Cenozoic West Antarctic Rift System. It is characterised by a distinct morphological transition from an elevated peneplain that dominates throughout most of the TAM to a strongly undulating relief with prominent narrow crests and alpine peaks. This contrast is associated with a lithological change from high-grade metamorphics and granitoids to low-grade metasedimentary rocks that contain only few scattered igneous bodies.New high-resolution thermochronological data (fission-track and (U-Th-Sm)/He) from more than 60 locations in the Southern Cross Mountains and Mountaineer Range of northern Victoria Land provide the basis for studying regional exhumation and uplift with particular focus on the establishment of landscape contrasts. In an integrated approach, differences in topography are examined with respect to regional and local controls including tectonics, lithology and climate to identify differential trends and quantify the morphological evolution of the TAM and West Antarctic Rift System. Two coastal profiles covering 2 to 3 km in elevation reveal apatite fission track ages from 23 to 45 Ma with mean track lengths of 13.3 – 14.7 μm. Corresponding (U-Th-Sm)/He apatite and zircon data range between 19 – 32 Ma and 24 – 27 Ma, respectively. The dates show distinctive spatial trends of increasing ages from north to south and at greater distance to the coast whereby younger cooling ages correlate with stronger terrain segmentation and higher topographic relief.Thermal history modelling of the combined data indicates that accelerated cooling commencing at 35 Ma proceeded at progressively higher rates reaching >25°C/Ma in late stages. This cooling episode continued until at least 20 Ma and refers to exhumation from burial depths of more than 5 km, clearly exceeding the calculated overburden on adjacent crustal blocks to the south. Although rapid upper lithospheric cooling is a generic feature of northern Victoria Land, the current data demonstrates that Cenozoic exhumation dynamics were highly differential. Understanding these patterns requires thorough balancing of structural against isostatic factors, lithological against climate parameters and focussed local incision against large-scale denudation and levelling processes.

Low-temperature thermochronology has long been utilised in the Red Sea-Gulf of Aden rift systems and adjacent hinterlands to examine exhumation cooling histories of basement blocks, particularly where datable syn-tectonic strata and/or markers are often absent. Such data have provided insights into the spatio-temporal evolution of rift basins, morphotectonic rift shoulder development and timing and rate of surface uplift. However, the relatively limited number of samples and confined areas involved in many individual case studies have precluded insights into the longer wavelength tectonic and geodynamic phenomena responsible for the latest Eocene-Oligocene to Recent separation of the Arabian plate from African and its subsequent collision with Eurasia. We present a synthesis of a large array of titanite, zircon and apatite fission track and (U-Th-Sm)/He analyses (12 TFT, 12 THe, 32 ZFT, 392 ZHe, 465 AFT and 267 AHe) from across northeast Africa and Arabia, which provide novel insights into the Phanerozoic thermo-tectonic evolution of the Arabian plate that were previously difficult to decipher from an otherwise cumbersome and intractably large dataset. Eocene to Recent cooling-heating maps have been constructed through a regional interpolation protocol of standardised thermal history models generated from the thermochronology data coupled with burial histories produced from vitrinite reflectance and well data. The interpolations, referred to here as thermo-tectonic images, record a series of pronounced episodes of upper crustal thermal regime fluctuation related to development of the latest Eocene-Oligocene-Recent Gulf of Aden and Red Sea rift systems and Cenozoic formation of the Al Hajar Mountains of Oman and the United Arab Emirates. They also provide insights into the inherited tectono-thermal histories of these regions, which controlled the spatial and temporal distribution of subsequent strain. Integration of the thermo-tectonic images, compiled with paleogeographic reconstructions and the regional igneous and strain history, offer a fresh regional perspective allowing the interrelationship between tectonism, geodynamic activity and exhumation history of the land surface to be visualised and explored on a plate scale.

The Broadly Rifted Zone (BRZ) of southern Ethiopia is a long-lived and structurally complex segment of the East African Rift System. However, due to poor surface exposure of early synrift strata and a dearth of subsurface data, the evolution of the BRZ remains poorly understood. We present new apatite (U-Th-Sm)/He and augmented apatite fission track low-temperature thermochronology data from the Beto and Galana basin boundary fault systems to constrain the tectonothermal evolution of the western and eastern BRZ, respectively. Time-temperature reconstructions suggest that East African Rift System-related extension began concurrently across the BRZ in the early Miocene (20–17 Ma), at least 6 Myr prior to faulting in the Main Ethiopian Rift further north. Increased time-temperature resolution provided by multithermochronometer analyses reveals contrasting along-strike spatiotemporal variations in Beto and Galana margin cooling histories, which appear to mirror the disparate structural geometries of their basin-bounding normal fault arrays. Longitudinal contrasts in basin architecture and rift-related cooling histories across the BRZ may reflect the region's heterogeneous distribution of preexisting basement fabrics, namely, the presence of a previously reported N-NNE trending Neoproterozoic suture zone beneath the eastern BRZ. Its influence may explain both the development of long, curvilinear faults and the gradual basinward migration of strain exhibited by the easternmost BRZ, absent further west. The anomalous evolution of the BRZ compared to the greater Ethiopian Rift, both in its earlier onset and its wider deformation zone, likely results from its inheritance of preattenuated lithosphere, thermomechanically modified by earlier Cretaceous-Paleogene Anza-South Sudan rifting and/or Eocene plume impingement.

The Terra Nova Bay region of the Transantarctic Mountains hosts three N–S to NNW–SSE extending mountain ranges, Deep Freeze Range, Eisenhower Range and northern Prince Albert Mountains. All ranges consist of basement rocks locally overlain by Permo-Triassic sediments and Jurassic volcanic rocks. Recent thermochronological studies recognized that the Eisenhower Range was originally covered by a kilometre-thick Jurassic–Eocene sedimentary sequence. Here we present a comprehensive apatite fission track (AFT) and U-Th-Sm/He (AHe) data set of vertical sample profiles from the Terra Nova Bay to reconstruct architecture, extension and geometry of this depocentre and place its evolution in the context of supraregional geodynamic processes. The study comprises new data and thermal history models from the Deep Freeze Range and new thermal history models of published data from the northern Prince Albert Mountains. New AFT and AHe ages of 25–275 Ma from the Deep Freeze Range correlate tightly with sample elevations. Thermal history modelling of these data and complementary proxies detects common heating of the Jurassic surface and rapid late Eocene cooling. Regression of vertical paleotemperature profiles reveals an increased Jurassic and a moderate Cretaceous–Eocene geothermal gradient of 45° and 25 °C/km, respectively. Paleotemperatures and gradients used in tandem infer basement burial increasing from ~ 2 km in Deep Freeze and Eisenhower Ranges to ~ 3.4 km in the Prince Albert Mountains. Such a varying overburden probably reflects regional differences in the Jurassic basement topography. Subsequently, sediment thickness uniformly increased in the order of 1 km until late Eocene. Mid-Jurassic basin initiation and subsequent sediment accumulation is explained by extension of a Mesozoic Victoria Basin during Gondwana breakup between Antarctica and Australia. Late Eocene/early Oligocene basin inversion is associated with the formation of the West Antarctic Rift System while differential final exhumation represents the change from downwearing to backstepping incision.

We present the results of a apatite fission-track (AFT) study on intrusive rocks in the southern Gulf of California, sampled along the eastern margin of Baja California Sur (western rift margin), as well as from islands and submerged rifted blocks within the Gulf of California, and from the conjugate Mexican margin (Nayarit state). For most of the samples U-Pb zircon and 40Ar-39Ar mineral ages were already available (Duque-Trujillo et al., 2015). Coupled with the new AFT data these ages provide a more complete information on cooling after emplacement. Our samples span a wide range of ages between 5.5 ± 1.1 and 73.7 ± 5.8 Ma, and show a general spatial distribution, with late Miocene AFT ages (about 6 Ma) aligned roughly NW-SE along a narrow offshore belt, parallel to Baja California Peninsula, separating older ages on both sides. This pattern suggests that in Late Miocene, deformation due to plate transtension focused at the eastern rheological boundary of the Baja California block. Some Early Miocene AFT ages onshore Baja California could be related to plutons emplaced at shallow depths and thermal resetting associated with the onset of volcanism at ~ 19 Ma in this part of the Peninsula. On the other hand, an early extensional event similar to that documented in the eastern Gulf cannot be ruled out in the westernmost Baja California.

Low-temperature thermochronology has long been utilised in the Afro-Arabian Rift System (AARS) to examine exhumation cooling histories of normal fault footwalls and elucidate rifting chronologies where datable syn-rift strata and/or markers are absent. In particular, apatite fission track (AFT) and (U-Th)/He (AHe) analyses have constrained the timing and rate of rift-related, upper crustal thermal perturbations between ~30 and 120 °C (up to ~5 km depth). In turn, these provide insights into the spatio-temporal evolution of individual rift basins, morphotectonic rift shoulder development, normal fault system growth and, in some cases, the thermal influence of igneous intrusions and circulation of hot fluids. However, the relatively limited number of samples and confined areas generally involved in individual case studies have precluded insights into longer wavelength tectonic and geodynamic phenomena, such as regional denudation trends and the growth of topography due to plume impingement.Here, we present a synthesis of >2000 apatite fission track (AFT) and ~1000 (U-Th)/He (AHe) analyses from the Eocene-Recent AARS collated using LithoSurfer, a new cloud-based geoscience data platform. This continental-scale low-temperature thermochronology synthesis, the first of its kind in Africa, provides novel insights into the upper crustal evolution of the AARS that were previously difficult to decipher from an otherwise cumbersome and intractably large dataset. The data record a series of pronounced episodes of upper crustal cooling related to the development of the Red Sea, Gulf of Aden and East African Rift System (EARS). They also provide insights into the inherited tectono-thermal histories of these regions which controlled the spatial and temporal distribution of subsequent extensional strain.Thermochronology data trends along the AARS reflect a combination of rift maturity, structural geometry and geothermal regime, intrinsically linked to lithospheric architecture and magmatic activity. These relationships are best illustrated by contrasting the upper crustal thermal evolution of different AARS segments of varying age and complexity: for example, between the nascent Okavango, mature Ethiopian and evolved Red Sea rifts, wide (e.g. Turkana Depression) versus narrow (e.g. Main Ethiopian Rift) zones of deformation, between areas of transtensional (Dead Sea Transform), oblique (e.g. Gulf of Aden) and sub-orthogonal rifting (e.g. Malawi Rift), and the magmatic eastern versus amagmatic western branches of the EARS.A regional interpolation of standardised thermal history models generated from the mined AFT, AHe and, in some cases, vitrinite reflectance data yield Mesozoic-recent heat maps, extrapolated to produce paleo-denudation and burial histories for eastern Africa and Arabia. Integrating these thermotectonic images with other regional datasets allows for the interrelationship between tectonic and dynamic topography development, the denudation history of the land surface, and sediment transport and deposition to be explored in new ways.

The French Massif Central is a portion of the Variscan belt that exhibits a present-day high topography associated with a potential Cenozoic rejuvenation. Despite other Variscan massifs in Central Europe, such as the Bohemian, Rhenish and Vosges/Black Forest Massifs, show similar topography, the French Massif Central is higher, wider and with evidence of more intense late Cenozoic volcanism. Deep-seated processes controlled by mantle upwelling are generally invoked for the origin of Cenozoic uplift, although the timing and quantification of the relief formation remain unclear. Here we presenta thermochronological study based on new apatite (U-Th)/He and fission-track data that have been integrated with published data (Barbarand et al., 2001; Gautheron et al., 2009) to reconstruct the exhumation history of the eastern margin of the massif. Apatite (U-Th)/He and fission-track data show Cretaceous ages from the high elevation samples and Eocene ages from the lower samples. Although the thermochronological ages do not allow to clearly constrain the onset of Cenozoic exhumation, the regional distribution of the mean track length is essential for the interpretation of the eastern margin evolution: mean track length-elevation relationships show a complex and non-linear trend consisting in a general decrease of MTL from high elevation/old age toward intermediate elevations and then a slight increase for the lowermost and youngest samples. We integrated inverse and forward modelling approach to test different hypothesis of margin evolution. The best fit between observed and predicted data is obtained with a Cretaceous cooling followed by a phase of thermal stability around 40°C and a renewed (lower amplitude) cooling during late Cenozoic. These two cooling events represent two main tectonic phases, the first in the Cretaceous and a minor one in late Cenozoic.The limited amount of erosion coupled with the occurrence of Cretaceous deposits on top of the massif and in the Rhône river valley floor and no evidence for faulting suggest a long-wavelength flexure of the lithosphere, which has produced a margin topography characterized by a broad monocline with a very low gradient. This topography is consistent with a surface growth induced by mantle upwelling.

International audience; The Admiralty Mountains region forms the northern termination of the northern Victoria Land, Antarctica. Few quantitative data are available to reconstruct the Cenozoic morpho-tectonic evolution of this sector of the Antarctic plate, where the Admiralty Mountains region forms the northern termination of the western shoulder of the Mesozoic-Cenozoic West Antarctica Rift System. In this study we combine new low-temperature thermochronological data (apatite fission-track and (U-Th-Sm)/He analyses) with structural and topography analysis. The regional pattern of the fission-track ages shows a general tendency to older ages (80–60 Ma) associated with shortened mean track-lengths in the interior, and younger fission-track ages clustering at 38–26 Ma with long mean track-lengths in the coastal region. Differently from other regions of Victoria Land, the younger ages are found as far as 50–70 km inland. Single grain apatite (U-Th-Sm)/He ages cluster at 50–30 Ma with younger ages in the coastal domain. Topography analysis reveals that the Admiralty Mountains has high local relief, with an area close to the coast, 180 km long and 70 km large, having the highest local relief of >2500 m. This coincides with the location of the youngest fission-track ages. The shape of the area with highest local relief matches the shape of a recently detected low velocity zone beneath the northern TAM, indicating that high topography of the Admiralty Mountains region is likely sustained by a mantle thermal anomaly. We used the obtained constraints on the amount of removed crustal section to reconstruct back-eroded profiles and calculate the erosional load in order to test flexural uplift models. We found that our back-eroded profiles are better reproduced by a constant elastic thickness of intermediate values (Te = 20–30 km). This suggests that, beneath the Admiralty Mountains, the elastic properties of the lithosphere are different with respect to other TAM sectors, likely due to a stationary Cenozoic upper mantle thermal anomaly in the region.

Located in the foreland domain of the Alpine and Pyrenean mountain belts, the French Massif Central presents enigmatic topographic features—reaching elevations of ∼1700 m above sea level and ∼1000 m of relief—that did not originate from Alpine compressional nor from extensional tectonics. Similar to other Variscan domains in Europe, such as the Bohemian, Rhenish, and Vosges/Black Forest Massifs, a Cenozoic uplift has been postulated, although its timing and quantification remain largely unconstrained. With respect to the other Variscan Massifs, the French Massif Central is wider and higher and shows a more intense late Cenozoic volcanism, suggesting that deep-seated processes have been more intense. In this study, apatite fission-track and (U-Th)/He thermochronometry were applied to investigate the long-term topographic evolution of the Massif Central. Our new thermochronological data come from the eastern flank of the massif, where sampling profiles ran from the high-elevation region down to the Rhône River valley floor with a total elevation profile of 1200 m. Age-elevation relationships, mean track-length distributions, and thermal modeling indicate a two-step cooling history: (1) a first exhumation event, already detected through previously published thermochronology data, with an onset time during the Cretaceous, and (2) a more recent Cenozoic phase that is resolved from our data, with a likely post-Eocene onset. This second erosional event is associated with relief formation and valley incision possibly induced by a long-wavelength domal uplift supported by mantle upwelling.

The Moroccan High Atlas, the Anti-Atlas belts, and the Siroua volcanic massif form an orographic system locally risen to elevations over 4 km. Topographic growth of this system occurred by Cenozoic transpressive inversion of Mesozoic rift structures concomitant with volcanic activity and related mantle processes. In order to constrain the topographic growth, we analyze the regional-scale exhumation pattern, and we compare it to physiographic features. We contribute 35 new mean (U-Th-Sm)/He and 24 new fission track ages on apatite from the High Atlas and Anti-Atlas, which all together range from 196 to 5 Ma. In the Anti-Atlas, we find that the rate and amount of Cenozoic exhumation are

Detrital apatite fission-track (AFT) thermochronology has been applied to lower Pleistocene lacustrine fan-delta sediments of the NE shoulder of the Mugello Basin, the youngest and closest to the main watershed among the Northern Apennines intermontane basins. The aim was to decode the shoulder uplift dynamics during the development of the basin through the analysis of the Quaternary fluvio-lacustrine deposits. Bedrock shoulder analysis, performed to match the detrital AFT data with their source, revealed the presence of a unexpected only partially annealed portion of a turbidite foredeep unit (AFT ages >7–5 Ma) belonging to the structural complex that constitutes the shoulder bedrock. These data disagree with the AFT age distribution pattern of the well-studied Northern Apennines chain, suggesting a segmentation of the foredeep basin. The latter may have been related to the presence of a tectonically induced topographic high (pre-late Langhian) in the area limiting the thickness of the overriding Ligurian lid. On the other hand, detrital AFT data provided arguments for understanding the dynamics of Mugello Basin shoulder uplift and rotation. The proportion in the different stratigraphic units of the fan-delta sediments of single grains showing young (reset) and old (non-reset) ages points to late Early Pleistocene timing of the development of the SW-verging backthrust that characterizes the study area. These data confirm and detail the picture of an early Quaternary development of the Mugello Basin under a compressional setting, only later (middle Pleistocene to present) superimposed by normal faultings.

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary.

In northern Turkey, the Intra-Pontide suture zone represents one of the first-order tectonic structures located between the Istanbul–Zonguldak and the Sakarya continental terranes. It consists of an E–W-trending assemblage of deformed and variably metamorphosed tectonic units, including sedimentary rocks and ophiolites derived from a Neo-Tethyan oceanic basin, known as the Intra-Pontide oceanic basin. One of these units is represented by the Daday Unit that consists of a block-in-matrix assemblage derived from supra-subduction oceanic crust and related deep-sea sedimentary cover of Middle Jurassic age. This setting was acquired during Late Jurassic time by tectonic underplating at a depth of 35–42 km associated with blueschist-facies metamorphism (D1 phase). The following D2, D3 and D4 phases produced the exhumation of the Daday Unit up to shallower structural levels in a time span running from the Albian to late Paleocene. The high geothermal gradient detected during the D2 phase indicates that the Daday Unit was exhumed during a continent–arc collisional setting. The tectonic structures of the Intra-Pontide suture zone, resulting from the previously described tectonic history, are unconformably sealed by the upper Paleocene – Eocene deposits. This tectonic setting was intensely reworked by the activity of the North Anatolian Fault Zone, producing the present-day geometrical relationships of the Intra-Pontide suture zone of the Central Pontides.

Southern Ethiopia is a key region to understand the evolution of the East African rift system, since it is the area of interaction between the main Ethiopian rift (MER) and the Kenyan rift. However, geological data constraining rift evolution in this remote area are still relatively sparse. In this study the timing, distribution, and style of rifting in southern Ethiopia are constrained by new structural, geochronological, and geomorphological data. The border faults in the area are roughly parallel to preexisting basement fabrics and are progressively more oblique with respect to the regional Nubia–Somalia motion proceeding southward. Kinematic indicators along these faults are mainly dip slip, pointing to a progressive rotation of the computed direction of extension toward the south. Radiocarbon data indicate post 30 ka faulting at both western and eastern margins of the MER with limited axial deformation. Similarly, geomorphological data suggest recent fault activity along the western margins of the basins composing the Gofa Province and in the Chew Bahir basin. This supports that interaction between the MER and the Kenyan rift in southern Ethiopia occurs in a 200 km wide zone of ongoing deformation. Fault-related exhumation at ~10–12 Ma in the Gofa Province, as constrained by new apatite fission track data, occurred later than the ~20 Ma basement exhumation of the Chew Bahir basin, thus pointing to a northward propagation of the Kenyan rift-related extension in the area.

Apatite fission-track (AFT) analyses were performed on 16 sandstone samples from a tectonic mélange unit exposed in three tectonic windows located near the inferred front of the early Miocene subduction system of the Northern Apennines of Italy. The tectonic windows display a block-on-block tectonic mélange present under the Ligurian Units. The mélange is formed by portions of the upper plate incorporated in the plate boundary shear zone as a consequence of a mechanism of frontal tectonic erosion during the Aquitanian (early Miocene). AFT and structural data, together with stratigraphic constraints, allow the reconstruction of a complete deformation cycle with a phase of underthrusting followed by underplating and early exhumation of the tectonic mélange. The exhumation, in particular, took place at ~10-20 km from the original subduction front. Moreover, the analysis suggests that multiple faults were active at the same time in the frontal part of the subduction zone.

Two volcaniclastic deposits, ROC and SBA, in the Oligo-Miocene succession of the Southern Apennines, between the Apulia and Campania regions, have been studied for the first time. Mineral composition, SEM-EDS and LA-ICP-MS analyses, for major and trace elements, respectively, allowed recognizing magmatic products of typical calc-alkaline to high-K calc-alkaline affinity. ROC glasses have a restricted compositional range in the rhyolitic field whereas SBA glasses show a wide compositional range from andesite to rhyolite, with dacite as the most common composition. Fission-track dating of apatite in the SBA deposits yielded an age of 21.7 ± 2.2 Ma, which is comprised between the Chattian and the Burdigalian. Biostratigraphic analyses in sedimentary layers adjacent to ROC layers indicate they were deposited not before Burdigalian. A provenance analysis of the studied volcaniclastics in relation to the possible source areas of the Mediterranean and neighbouring areas was performed. On the basis of time constraints, mineral and trace element composition a convincing correlation of the ROC deposits with potential source areas did not emerge. Instead, a provenance from the southwestern and northwestern Sardinian volcanic centres was favoured for the SBA volcaniclastic deposits. This hypothesis is compatible with the Oligo-Miocene paleogeographic reconstructions, that show the proximity of the Apennine sedimentary basins to Sardinia before the opening of the Tyrrhenian sea.

We use new structural and apatite fission-track data together with apatite fission-track and (U-Th)/He data from literature to examine the tectonic evolution of the continental Upper Valdarno Basin, in the hinterland sector of the Northern Apennines fold-and-thrust belt. This basin is located in-between two structural ridges, the Chianti Mountains to the southwest and the Pratomagno to the northeast. In our interpretation, the Upper Valdarno Basin developed at ca. 3.4-3.3 Ma as pop-down synformal-shaped depression bounded and controlled by oppositely-verging thrust-related structures, namely the thrust system lifting the Chianti Mountains and the southwest-facing backfolds at the base of the Pratomagno. This evolution is compatible with the accelerated exhumation rates at 4-5 Ma documented through apatite fission-track data along both the Pratomagno and Chianti ridges. Shortening suffered by basin deposits is clearly manifested by the outcrop-scale reverse faults and thrust-related folds affecting the Late Pliocene sediments (Castelnuovo dei Sabbioni Synthem), which are well exposed in the Santa Barbara mine. These strongly folded deposits are overlain unconformable by Early Pleistocene sediments (Montevarchi Synthem), which display evidence for syn-depositional normal faulting. This suggests that the Upper Valdarno Basin experienced a phase of normal faulting that started at the base of Pleistocene (ca. 2.6-2.5 Ma) and likely produced the large southwest-dipping “Trappola Fault”, which affects the southwestern margin of the Pratomagno displacing the earlier backthrusts and backfolds. Basin evolution can be thus basically framed into a two-phase history, with extensional tectonics superposed onto compressional structures that were deactivated by ca. 2.7 Ma. Being the Chianti Mountains part of the 250 km-long regional line of thrusts and thrust-related folds (the so-called “Tuscan Nappe front”), the results of this study may also involve regional implications, as they would also hint for the tectonic history of other sectors and basins settled along-strike this regional element.

Terra Nova, 24, 221–226, 2012 Abstract We applied fission-track analysis on modern river sands to constrain the Cenozoic evolution of the Alps–Apennines junction zone. West of the Villalvernia-Varzi-Ottone fault, samples yielded major peaks at 33–36 and 62–65 Ma, showing that apatites in the eroded wedge-top successions were largely unreset. To the east, samples yielded prominent peaks at 4.0–4.7, 6.5–6.7 and 19 Ma, probably formed by reset ages. Our results indicate that the Alpine orogenic wedge originally tapered out to the south. The Northern Apennines were buried beneath a thick and widespread Epiligurian cover, now almost completely eroded, and experienced major uplift and erosional exhumation since early Pliocene times, at average rates of 1 km Ma−1. A large amount of Alpine-derived detritus, previously stored on top of the orogenic wedge, was transferred into the Po Plain. Sediment recycling thus overwhelmed any eventual effect of climate change on Plio-Quaternary sedimentation rates south of the Alps.

An isolated block of Precambrian basement rocks and Mesozoic sediments is exposed at Kella along the western margin of the Central Main Ethiopian Rift (MER), surrounded by Tertiary to Quaternary volcanic rocks. Apatite fission-track thermochronology on two basement samples yielded ages of 7.2 ± 1.0 Ma and 6.7 ± 3.0 Ma and a long mean track length (>14.5 lm). Rapid Late Miocene cooling is attributed to denudation related to rifting. Despite the paucity of data, due to the absence of suitable lithologies in the area, our data confirm that the Central MER is younger than 8 Ma as recently proposed on the basis of field evidence and radiometric dating of volcanics. This implies that the Central MER formed after the Northern MER, indicating a diachronous development of this third arm of the Red Sea‐Gulf of Aden‐Ethiopian Rift system.

To reconstruct the timing of rift inception in the Broadly Rifted Zone in southern Ethiopia, we applied the fission track method to basement rocks collected along the scarp of the main normal faults bounding (i) the Amaro Horst in the southern Main Ethiopian Rift and (ii) the Beto Basin in the Gofa Province. At the Amaro Horst, a vertical traverse along the major eastern scarp yielded pre-rift ages ranging between 121.4 +/- 15.3 Ma and 69.5 +/- 72 Ma, similarly to two other samples, one from the western scarp and one at the southern termination of the horst (103.4 +/- 24.5 Ma and 65.5 +/- 4.2 Ma, respectively). More interestingly, a second traverse at the Amaro northeastern terminus released rift-related ages spanning between 12.3 +/- 2.7 and 6.8 +/- 0.7 Ma. In the Beto Basin, the ages determined along the base of the main (northwestern) fault scarp vary between 22.8 +/- 3.3 Ma and 7.0 +/- 0.7 Ma. We ascertain through thermal modeling that rift-related exhumation along the northwestern fault scarp of the Beto Basin started at 12 +/- 2 Ma while in the eastern margin of the Amaro Horst faulting took place later than 10 Ma, possibly at about 8 Ma. These results suggest a reconsideration of previous models on timing of rift activation in the different sectors of the Ethiopian Rift. Extensional basin formation initiated more or less contemporaneously in the Gofa Province (similar to 12 Ma) and Northern Main Ethiopian Rift (similar to 10-12 Ma) at the time of a major reorganization of the Nubia-Somalia plate boundary (i.e., 11 2 Ma). Afterwards, rift related faulting involved the Southern MER (Amaro Horst) at similar to 8 Ma, and only later rifting seemingly affected the Central MER (after similar to 7 Ma). (C) 2016 Elsevier B.V. All rights reserved.

International audience; Central Iran provides an ideal region in which to study the long-term morphotectonic response to the nucleation and propagation of intraplate faulting. In this study, a multidisciplinary approach that inte-grates structural and stratigraphic field investigations with apatite (U + Th)/He (AHe) thermochronometry is used to reconstruct the spatio-temporal evolution of the Kuh-e-Faghan Fault in northeastern central Iran. The Kuh-e-Faghan Fault is a narrow, similar to 80-km-long, deformation zone that consists of three main broadly left-stepping, E-W-trending, dextral fault strands that cut through the Mesozoic-Paleozoic substratum and the Neogene-Quaternary sedimentary cover. The AHe thermochronometry results indicate that the intrafault blocks along the Kuh-e-Faghan Fault experienced two major episodes of fault-related exhumation at ca. 18 Ma and ca. 4 Ma. The ca. 18 Ma faulting/exhumation episode is chiefly recorded by the structure and depositional architecture of the Neogene deposits along the Kuh-eFaghan Fault. A source-to-sink scenario can be reconstructed for this time frame, where topographic growth caused the synchronous erosion/exhumation of the pre-Neogene units and deposition of the eroded material in the surrounding fault-bounded continental depo-centers. Successively, the Kuh-eFaghan Fault gradually entered a period of relative tectonic quiescence and, probably, of regional subsidence, during which a thick pile of fine-grained onlapping sediments was deposited. This may have caused resetting of the He ages of apatite in the pre-Neogene and the basal Neogene successions. The ca. 4 Ma faulting episode caused the final exhumation of the fault system, resulting in the current fault zone and topography. The two faultrelated exhumation episodes fit with regional early Miocene collision-enhanced uplift/exhumation, and the late Miocene-early Pliocene widespread tectonic reorganization of the Iranian Plateau. The reconstructed longterm, spatially and temporally punctuated fault system evolution in intraplate central Iran during Neogene-Quaternary times may reflect states of far-field stress changes at the collisional boundaries.

New analyses have been performed in order to enhance the data-set on the independent ages of four glasses that have been proposed as reference materials for fission-track dating. The results are as follows. Moldavite - repeated 40Ar/39Ar age determinations on samples from deposits from Bohemia and Moravia yielded an average of 14.34 ± 0.08 Ma. This datum agrees with other recent determinations and is significantly younger than the 40Ar/39Ar age of 15.21 ± 0.15 Ma determined in the early 1980s. Macusanite (Peru) -four K-Ar ages ranging from 5.44 ± 0.06 to 5.72 ± 0.12 Ma have been published previously. New 40Ar/39Ar ages gave an average of 5.12 ± 0.04 Ma. Plateau fission-track ages determined using the IRMM-540 certified glass and U and Th thin films for neutron fluence measurements agree better with these new 40Ar/39Ar ages than the previously published ages. Roccastrada glass (Italy) - a new 40Ar/39Ar age, 2.45 ± 0.04 Ma, is consistent with previous determinations. The Quiron obsidian (Argentina) is a recently discovered glass that has been proposed as an additional reference material for its high spontaneous track density (around 100 000 cm-2). Defects that might produce “spurious” tracks are virtually absent. An independent 40Ar/39Ar age of 8.77 ± 0.09 Ma was determined and is recommended for this glass. We believe that these materials, which will be distributed upon request to fission-track groups, will be very useful for testing system calibrations and experimental procedures. De nouvelles analyses ont ete effectuees afin d'etoffer la base de donnees d'âges independants obtenus sur 4 verres qui ont ete proposes comme materiaux de reference pour la datation par trace de fission. Les resultats sont les suivants : sur la Moldavite, des datations 40Ar/39Ar repetees sur des echantillons provenant de depots en Boheme et en Moravie ont donne une moyenne de 14.34 ± 0.08 Ma. Ce resultat est en accord avec les autres datations recemment effectuees et est significativement inferieur a l'âge 40Ar/39Ar de 15.21 ± 0.15 Ma determine dans les annees 1980. Pour la Macusanite (Perou), quatre âges K-Ar entre 5.44 ± 0.06 et 5.72 ± 0.12 Ma avaient ete publies precedemment. Les nouvelles datations 40Ar/39Ar donnent une valeur moyenne de 5.12 ± 0.04 Ma. Les datations par trace de fission avec plateau, utilisant le verre certifie IRMM-540 et des films minces de U et Th pour mesurer les flux de neutrons sont en meilleur accord avec ces nouveaux âges 40Ar/39Ar qu'avec les âges publies precedemment. Pour le verre de Roccastrada (Italie), un nouvel âge 40Ar/39Ar de 2.45 ± 0.04 Ma est en accord avec les determinations precedentes. L'obsidienne de Quiron (Argentine) est un verre decouvert recemment qui a ete propose comme materiau de reference additionnel en raison de son importante densite de traces de fission spontanees (autour de 100 000 cm-2). Les defauts qui peuvent produire de “fausses” traces sont quasi absents. Une datation 40Ar/39Ar independante de 8.77 ± 0.09 Ma a ete determinee a la demande des groupes travaillant en trace de fission et est recommandee pour ce verre. Nous estimons que ces materiaux, qui seront distribues sur demande aux groupes travaillant en trace de fission, seront tres utiles pour tester les systemes de calibration et les procedures experimentales.

In the Northern Apennines of Italy the Ligurian and Subligurian Units (LSU) represent far-travelled/allochthonous units which, since early Miocene to Recent, migrated towards NE, above the Tuscan-Umbrian foredeep deposits, reaching the present-day frontal ranges of the chain. In the NE-facing side of the western Northern Apennines the present-day geometry of the LSU does not reflect the shape they acquired during the late Oligocene, when the early orogenic collisional phases produced a wedge whose geometry tapered out towards the foreland area, i.e. to the E-NE. In fact, at present, geological evidences indicate that the LSU are characterized by a doubly-tapering geometry, whose thickness ranges from less than 1 km at the main ridge zone (SW) up to more than 4 km along the NE slope of the chain and then tips out again few km N of the Northern Apennines topographic front, underneath the late Messinian to Recent marine and continental deposits of the Po Plain foredeep. These data imply that since late Oligocene the LSU geometry has been deeply reshaped inside a context of overall growth of the orogenic wedge. Therefore the reshaping of the LSU is related to their post-early Miocene progressive emplacement over the foredeep units and to the late orogenic evolution of the Northern Apennines, characterized by the coeval activity of extensional and compressional tectonics. In order to put new constraints on the relationships existing between timing and modes of reshaping of the LSU and the Miocene to Recent evolution of the western Northern Apennines, we adopted a multidisciplinary approach which took into account field evidences, low temperature thermal and thermochronological data (vitrinite reflectance, clay mineral analyses, apatite fission track dating), numerical modelling of the AFT cooling ages through the use of Pecube finite element code, recently published works on the evolution of the external slope of the chain, and a new interpretation of seismic lines and boreholes data. This multidisciplinary approach allowed us to: 1) build a 3D representation of the LSU present-day geometry; 2) highlight two main stages of reshaping of the LSU, first during late Miocene (10 to 6 Ma), and subsequently during Pliocene to Recent (?) time (6 to 0 (?) Ma); 3) relate, during the first stage, the LSU thinning processes, achieved by means of low-angle extensional faults, to the tectonic denudation of the foredeep units; 4) envisage the importance of coupled tectonic (high-angle extensional tectonics) and progressively increased surface erosion processes as responsible for the denudation of the foredeep units during the second stage; 5) define estimates of the exhumation/erosion rates characterizing the investigated area during the last 10 My. These results allowed us to give new insights, temporal and spatial constraints on the morphostructural evolution of the western Northern Apennines, which has been mainly affected initially (10-6 Ma) by the interplay between deep compressional and coeval shallow extensional tectonics (< 20 and < 4 km, respectively), and subsequently by the progressively more relevant onset of surface erosion processes.

Coeval extensional and contractional tectonics are a common feature in orogenic belts, especially in post-collisional phases. The attempt to constrain their relative timing and the responsible mechanisms led to several models taking into account different geodynamic contexts of various mountain chains. In peri-Mediterranean collisional orogens, extension and compression are commonly associated and coeval to the emplacement of far-travelled/allochthonous units. Therefore their internal deformation acquired during the translation across collisional belts is likely imprinted by the extensional and contractional tectonics affecting the orogen.In the western portion of the Northern Apennines of Italy, one of the northernmost peri-Mediterranean Tertiary orogens, the far-travelled/allochthonous units, i.e., the Ligurian and Subligurian units, are widely exposed. The present study integrates published and newly acquired surface geological data (geological maps, cross-sections), subsurface boreholes data, and paleothermal (vitrinite reflectance, mixed layer illite-smectite and Kübler index) and thermochronological data (apatite fission-tracks) in order to investigate the deformation history and, consequently, the record of the extension-compression relationships within these far-travelled/allochthonous units.The study of modes and timing of reshaping of the far-travelled/allochthonous units allowed us to strengthen the hypothesis that extensional and contractional tectonics were coeval in the Northern Apennines and tightly connected by a cause/effect relationship. In particular, the late orogenic low- and high-angle extensional tectonics represent the response to an overall contractional regime which induced episodes of gravitational instability in the orogenic wedge. © 2013 Elsevier B.V.

Apatite (U–Th)/He and fission-track thermochronometers are combined to constrain models of denudation and escarpment development of the high elevation Eritrean margin along the southern Red Sea. (U–Th)/He ages have been determined for apatites from two coast-perpendicular transects that were previously used for apatite fission-track analysis [E. Abbate, M.L. Balestrieri, G. Bigazzi, Morphostructural development of the Eritrean rift flank (southern Red Sea) inferred from apatite fission track analysis, J. Geophys. Res., 107, B11, doi: 10.1029/2001JB001009, (2002)]. In central Eritrea near Asmara, He ages increase from c. 7 Ma at the coast to 152 Ma on the plateau along a transect. Further south, He ages from the margin border to the base of the escarpment span a narrower range (7 to 12 Ma). One sample from the top of a marginal high (2950 m) yields older ages (22–43 Ma). Forward modeling suggests that the He age distribution across the margin should allow scarp retreat and downwearing mechanisms to be distinguished in the case of a margin formed in the last twenty million years. The distribution of He ages suggests that the escarpment evolved by downwearing and that post-break up erosion of the escarpment was facilitated by in situ excavation rather than parallel retreat. This implies the existence of an inland drainage divide located seaward of the present day escarpment rim. We envisage that the inland divide formed during or immediately after continent break up, and that the eastern marginal belt represents a remnant of the apex structure. The short distance between the eastern marginal belt and the rim (c. 10 km) represents the total retreat of the escarpment. Comparison of the measured He ages from the coastal plain with those predicted from forward modelling indicates that the main phase of post-break up erosion started at about 15 Ma, closer to the initiation of seafloor spreading in the Red Sea than was thought previously.

Application of different thermochronological methods to two areas of pronounced relief (Apuane Alps and Mt. Falterona ) of the Northern Apennines chain documents an average exhumation rate of about 0: 7m m=yr: This result suggests that the general exhumation of the chain is driven mainly by erosion. Nevertheless, the long-term exhumation trend seems to be perturbed by shortterm events at higher exhumation rates. The time of increased exhumation rates coincides with onset of intramontane sedimentation, documenting a contribution of tectonics (local normal faulting?) to the surface uplift. The data indicate an eastward shifting of the onset of topographic relief, Early Pliocene in the Apuane Alps and Early Pleistocene in the Mt. Falterona area. r 2002 Elsevier Science Ltd and INQUA. All rights reserved.

The West Antarctic Ice Sheet is the most unstable component of the Antarctic cryosphere. Its fluctuations are well documented since the Pliocene, but its behaviour over the last 35 Ma is more controversial, particularly during periods of past high global pCO2 values similar to those predicted in future global climate scenarios. Here, we present new U-Pb dating of detrital apatite grains (previously dated by the fission-track method) from Cape Roberts Project Oligocene to Pliocene marine sediments in the Ross Sea. Two past ice-flow patterns were identified: one formed by outlet glaciers sourcing short-travelled apatites and one, northerly directed, bringing far-travelled apatite grains. The latter provides the first robust physical evidence for the presence and repeated expansion of an Oligocene West Antarctic Ice Sheet.

In this work a software developed in the Instituto de Fisica Gleb Wataghin, IFGW, UNICAMP, Campinas, SP, Brazil for obtaining thermal histories using apatite fission track analysis is presented. This software works in Microsoft-Windows environment. It will be freely disposable in the web site of the Departamento de Raios Cosmicos, IFGW, UNICAMP. Thermal histories obtained through this software are compared with those deduced using Monte Trax the software compatible with Apple Macintosh developed by Gallagher.

Apatite fission-track analysis was performed on 13 granitoid samples of the Devonian Admiralty Intrusive Complex collected along two elevation profiles in the Admiralty Block, northern Victoria Land (NVL), East Antarctica. The sample age-elevation diagram shows a break in slope that indicates the presence of the Late Cretaceous phase of uplift and denudation already recognized in other sectors of NVL. Modeling of data suggests that the rocks may record also an Early Cenozoic pulse of denudation.

This paper takes into consideration more than 100 apatite fission-track analyses on samples coming from an approximately west-east cross-section throughout the Northern Apennines. This collisional chain is made of structural units and nappes (Ligurian and Tuscan Nappe) accreted to the Adriatic Foreland during the Neogene, which overthrust the Miocene turbiditic successions of the Cervarola and Marnoso-arenacea Formations. Different cooling ages and degrees of annealing delineate different evolution histories for these units. Exhumation of the western outcrops of the Ligurian Nappe can be placed at 8 Ma and follows a first denudation event occurred in Eocene times. Timing of exhumation decreases eastwards. A break in this general trend is shown by the Apuan Alps, that occupy an intermediate position and yielded the youngest cooling ages. In the external part of the Marnoso-arenacea foredeep deposits this tendency could not be tested because total annealing of the apatite system has not been reached. In this case, modeling of data allows evaluating maximum burial temperatures.

An extensive dataset of vitrinite reflectance, FTIR parameters on organic matter, illite content in mixed layers illite-smectite, apatite fission tracks and U-Th/He dating has been used to reconstruct the stepwise propagation of the Eastern Sicily fold-and-thrust belt during Late Palaeogene and Neogene times. The results indicate that the fold-and-thrust belt is divisible into two levels of thermal maturity. These levels consist of a less evolved level of thermal maturity that records limited sedimentary burial and minor heating, and a more evolved level of thermal maturity that indicates tectonic burial and exhumation at different times. Deformation and exhumation of shallowly buried units are linked to wedge forward propagation by low-angle thrusts, whereas the evolution of deeply buried units is associated with tectonic imbrications by duplex formation and steep thrusts. The two tectonic styles alternate during evolution of the fold-and-thrust belt under low erosion rates. © 2014 John Wiley & Sons Ltd.

The Eisenhower Range is a N-S trending mountain range in the Transantarctic Mountains (TAM) adjacent to the NW Ross Sea Embayment. New AFT and apatite (U-Th-Sm)/He (AHe) data from vertical basement profiles supplemented by paleotemperature and pressure estimates derived from Beacon sandstones provide new quantitative results on regional burial evolution and first regional constraints on basin inversion and exhumation processes. AFT ages between 32 +/- 2 and 259 +/- 18 Ma and AHe ages of 37 +/- 3-173 +/- 16 Ma correlate positively with sample elevations. Thermal history modeling of these data and complementary thermal indications detect heating of the paleosurface on the Eisenhower Range to temperatures >= 80 degrees C subsequent to Ferrar magmatism, and constrain Late Eocene rapid cooling. Regression of modeled paleotemperatures against sample elevations refers to a high Jurassic (similar to 45 degrees C/km) and a moderate Cretaceous-Eocene (28 +/- 8 degrees C/km) geothermal gradient. The texture of Beacon sandstones supports strong mechanical compaction that requires a higher overburden than preserved in the stratigraphic record. Modeled paleotemperatures and pressures suggest basement burial that increases from Late Jurassic (0.7-1.1 km) to Eocene (1.8-2.1 km). The overburden comprises 0.7-1.1 km cumulative Beacon/Ferrar rocks and 0.7-1.4 km of post-Ferrar sediments. Rapid cooling of the whole sample suite between similar to 35 and 30 Ma implies fast erosion of the post-Ferrar sediments and (re-) exposure of underlying magmatic rocks. Subsequent differential sample cooling to present-day surface temperature infers ongoing exhumation by glacial incision enhanced by isostatic response to basin inversion. Decreasing amounts of exhumation from the coast (>3 km) toward the interior (1.5-2.2 km) point to backstepping incision along the fault controlled Priestley Glacier. Substantial exhumation of the Eisenhower Range since the Late Eocene is hence triggered by both tectonic and climatic factors, superimposed by considerable lithological influence during the initial exhumation stage. (C) 2014 Elsevier B.V. All rights reserved.

Apatite fission-track analysis has been applied on 24 samples from the geometrically upper units (Internal and External Ligurids) of the Northern Apennines nappe pile. They yield ages between c. 20 Ma and c. 6 Ma. Two samples were also dated with fission tracks in zircon (ages of c. 155 Ma and c. 199 Ma). Together the data reveal that during post-Late Cretaceous compression the Internal Ligurids reached temperatures to completely anneal fission tracks in apatite (T>c. 120 °C) but not in zircon (T 300°C). After Eoccne continental collision these rocks were cooled (below c. 120°C) and started again to retain fission tracks in apatite. Since the Oligocene a further burial under episutural sediments ensued that caused a partial to total apatite fission-track annealing. During a final phase of cxhumation the sedimentary cover was removed. This exhumation can be linked to Late Miocenc extensional tectonics, that started at c. 8–9 Ma in the central and southern portions of the study area.

In the present paper a new irradiation position arranged for fission-track dating in the Triga Mark II reactor of the University of Pavia is described. Fluence values determined using the NIST glass standard SRM 962a for fission-track dating and the traditional metal foils are compared. Relatively high neutron thermalization (cadmium ratio of 85.3 for gold and 643 for cobalt) and lack of significant fluence spatial gradients are very favorable factors for fission-track dating. Finally, international age standards (or putative age standards) irradiated in this new position yielded results consistent with independent reference ages.

The Transantarctic Mountains (TAM) were one of the first regions where apatite fission track (AFT) thermochronology was applied routinely to study exhumation processes and long term landscape evolution. Pioneering publications from the region introduced or refined interpretation concepts of thermochronological data such as the break in slope in vertical age profiles as qualitative marker for the onset of accelerated rock cooling. New AFT data were compiled from vertical profiles in the Eisenhower Range, northern TAM, and compared with published data. Samples originally examined by the population technique were re-analyzed via the external detector technique. AFT ages increase from 32 ± 2 Ma at an elevation of 220 m to 175 ± 14 Ma at 2380 m. Geological evidence and thermal history modeling of the AFT data require Jurassic to Late Eocene reheating of the samples and an onset of cooling at ~ 35 – 30 Ma. This requires the deposition of an ~ 3 to 3.5 km thick sedimentary sequence on the granitic basement subsequent to Jurassic Ferrar magmatism at ~ 180 Ma. The regression of paleotemperatures against sample altitudes infers a high Jurassic geothermal gradient of ~ 60 °C/km related to rifting processes and Ferrar magmatism, and a moderate Cretaceous/Eocene geothermal gradient of ~ 30 °C/km. Comparison of ages generated with population and external detector technique shows the importance of determining single-grain ages for each sample, even from granitic rocks of the same intrusion, and thus strongly supports previous cases made for the determination of annealing kinetics and grain-age evaluation. Age comparison additionally illustrates that samples above a break in slope record larger deviations between population and external detector ages than samples below a break in slope. We demonstrate that the position and shape of a break in slope result from various factors, such as the thermal history prior to final cooling, maximum paleotemperatures, cooling rate, and geothermal gradient. A break in slope does not straightly date the onset of final cooling and cannot substitute thermal history modeling. Therefore, earlier studies from the TAM and similar settings elsewhere need to be validated by combining thermal history modeling of thermochronological data and supplementary geological information.

The Cenozoic tectonic reorganization of the West Antarctic Rift System in the Ross Sea region occurred concurrently with a major change in the global climate system and a global reorganization of plate motions. This region thus provides the opportunity to study in detail a range of geological issues dealing with tectonic and climate feedbacks during the late Eocene/early Oligocene greenhouse/icehouse transition at high latitudes. With the aim to decipher tectonic vs. climatic forcing in the ice sheet drainage evolution, a detrital apatite fission track study was carried out throughout the Cenozoic drill-cored stratigraphic succession of the Cape Roberts Project (McMurdo Sound, Victoria Land Basin). Apatite fission-track ages of detrital samples, with depositional ages between 34 Ma and 17 Ma, were decomposed into statistically significant age populations. Three age peaks were detected, reflecting different bedrock provenance areas: (i) a young peak (P1 between 34 Ma and 26 Ma) recording the signal of a source area exhumed with a constant denudation rate, but absent in the proximal continental area; and (ii) two peaks, older than 40 Ma, that are instead compatible with thermochronological data available from the onshore bedrock. P1 peak testifies a late Oligocene–early Miocene denudation event and traces a southern provenance of a fraction of the sediments filling the Cape Roberts Basin. We propose that this denudation event might have been triggered by renewed N–S transtensional shearing along the western shoulder of Victoria Land Basin, controlling glacial flow pattern and the associated sediment transport.

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.

The Apennine Range is a young convergent orogen that formed over a retreating subduction zone. Syn-orogenic metamorphic rocks are exposed in the mid-Tuscan ridge, Tuscan coast and Tuscan Archipelago and provide information about processes of continental subduction and exhumation associated with accretion and retreat. Apatite and zircon fission-track analyses were applied to some of these syn-orogenic metamorphic rocks. The new low-temperature thermochrono-logical data helped to constrain the timing of the metamorphic peak and the age and modality of exhumation of these rocks that were structurally buried at 20 to 40 km depth during the main tectonogenic phase of the Northern Appenine belt. In the Giglio and Elba islands and in the Monti dell'Uccellina, along the coast, minimum ages of partially reset zircon samples yielded a first time constraint on the Late-Oligocene age of the metamorphic peak. The ca. 27Ma obtained at the Monti dell'Uccellina is coeval to that found in the Alpi Apuane (located at the northern termination of the mid-Tuscan ridge). The data from the Tuscan Archipelago point to a slightly older age. In the Monti Pisani, south of the Alpi Apuane, and in the Argentario Promontary along the coast, south of the Monti dell'Uccellina, completely reset zircon samples, but composed by different populations, were behaving as multiple thermochronometers and confirm the already proposed isothermal nature of the exhumation occurred after the metamorphic peak. Zircon P1 peak indicated that at 13-10Ma rocks were already at shallow crustal levels (