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Chlorine 36 (36Cl, T1/2 = 301,000 years) is a radionuclide with natural and anthropogenic origin that can be rejected during decommissioning of nuclear power plants or chronically during recycling of used nuclear fuels. Once emitted into the atmosphere, chlorine 36 (gas and particles) can be transferred to the soil and vegetation cover by dry and wet deposition. However, quantitative constraints of these deposits are very scarce. Because of its relatively high mobility in the geosphere and its high bioavailability, chlorine 36 fate in the environment should be studied for environmental and human impact assessments.The aim of this study is therefore to develop dry depositional models for the gaseous and particulate fractions of chlorine 36. The model used for the parameterization of gaseous chlorine 36 dry deposition on grass is the << Big-leaf >> model based on the electrical analogy (Seinfield 1985). It was adapted from the Bah (2020) model developed for iodine. For particulate chlorine 36, the Damay-Pellerin (2017) model was used. This model requiring the diameter of particulate chlorine 36 to be known, a sample of aerosol was taken in the chlorine 36 plume to determine on which particle size it is fixed. The sampling was performed on a low pressure impinger (LPI, DEKATI) of 13 levels for particles with diameters between 30nm and 10μm. In order to obtain model input data, meteorological and micrometeorological parameters were measured continuously at the IRSN La-Hague technical platform (PTILH, France). The PTILH is located 2 km north of Orano La-Hague plant which emits small quantities of chlorine 36. An ultrasonic anemometer (Young 81000V) installed at a height of 4,5 m from the ground measured the direction (°), the velocity u (m/s) and the air friction velocity u* (m/s), the sensible heat flux H, the Monin-Obukhov length (L) and the atmospheric stability (1/L). A weather station (Spectrum Watchdog, series 2000) measured temperature Ts (°C), relative humidity RH (%), dew point (°C), global radiation SR (Wat/m2) and photosynthetic active radiation PAR (μM/m2.s). Sampling campaigns of 2 weeks were also conducted at the PTILH site to determine experimental depositional rates of chlorine 36. Chlorine 36 measurements were carried out by acceleration mass spectrometry at CEREGE-LN2C (France).The particle size distribution of the aerosol sample from chlorine 36 plume shows two peaks, a main one at 2μm and a second one at 10μm, typical distribution of marine aerosol. The models yield chlorine 36 depositional velocities between 6,7.10-3 and 10-2 m/s for the particulate fraction, and between 5.10-3 and 1,3.10-2 m/s for the gaseous one. The total dry depositional velocities (particles and gas) calculated from the model are less than one order of magnitude than the ones obtained experimentally.

The Mw 6.4 Petrinja earthquake (2020, Croatia) is among the strongest continental earthquakes that occurred in Eastern Europe for decades. In such low-strain contexts, the sparse terrestrial-monitoring (few seismic and geodetic stations) of rare but strong earthquakes often prevents a detailed analysis of their seismic source. Here, we take advantage of > 160 geodetic benchmarks and optical image correlation to obtain a dense near-field coverage of the coseismic surface displacements. The geodetic dataset is obtained by repeated measurements of benchmark networks designed for civilian purposes and constitutes a unique dataset of coseismic displacements in the near-field of the fault. The optical image correlation is based on pre-earthquake (December 2017) WorldView and post-earthquake (February 2021) Pleiades satellite images with a 50 cm resolution. We also complete these displacement fields with unwrapped coseismic interferograms based on Sentinel-1 products, except in the near field affected by decorrelation. These displacement fields are consistent and thus suitable for modeling the slip distribution of the Petrinja earthquake. The elastic inversion of the geodetic benchmarks revealed interesting characteristics of this event: the rupture occurred on a near-vertical strike-slip fault, at a shallow depth (< 10 km), with significant slip reaching the surface. It also suggests that the deformation was partly accommodated by a subparallel strand 2.5 km from the main source northward. The aim of this research is to improve the source model of Petrinja 2020earthquake sequence, with a joint inversion of the geodetic benchmarks, optical image correlation, and InSAR data. Nevertheless, the comparison of the geodetic and coseismic offsets measurement on the field, shows that > 70% of the slip is likely distributed at the surface. Moreover, the coseismic strain maps derived from the unique benchmark data set helped us to identify zones where deformation appears distributed. Finally, the new data raises questions about whether such moderate earthquakes are accompanied by subsurface off-fault deformation or residual elastic strain.

Measuring 36Cl cosmogenic nuclides on exposed bedrock fault scarps has now been used in several places in the Mediterranean to retrieve ages of the fault seismic history (e.g. Mechernich et al. 2022, Iezzi et al. 2021 and Cowie et al. 2017).In Central Apennines, around the Fucino basin, at least 15 36Cl sampling sites were analyzed in previous studies to interpret the 36Cl data as seismic history or slip-rates. Several codes (e.g., Beck et al. 2018, Shlagenhauf et al. 2010) were used as a basis for solving 36Cl production equations to calculate the 36Cl concentration resulting from bedrock scarp exhumation history. Some codes included an MCMC routine to retrieve the seismic histories the closest to the dataset. The main differences between the various codes lie in: 1-the fault history prior to exhumation, 2-the parameters previous authors decided to inverse (as an example, mean density of the colluvium is inversed in Beck et al. 2018 but not in Tesson et al. 2019) and 3-the a priori distribution of those parameters (for instance, the time between two earthquakes follows an inverse gaussian distribution for Beck et al. 2018 but a uniform distribution for Tesson et al. 2019). I have compared the various codes and run them on the same dataset (one site at Campo Felice, one site at Roccapreturo and one site at Magnola) and found that retrieved seismic histories are similar, although the estimation of uncertainties differs.Moreover, all previous cited codes run under Matlab or Fortran. Fortran codes have the advantage of fast computing time but could be cumbersomeI here propose a new code, adapted from Tesson et al. 2019, in the more accessible and widely used Python language. The inferred pre-exposure is also inversed and is a function of the height of the fault cumulative escarpment. The parameters considered are the number of events, ages of event, the associated slips, the long term slip rate, the quiescence and the pre-exposure and their optimal evaluation is done with a MCMC algorithm provided by Numpyro (Du Phan et al. 2019).Using this new code, we have reanalyzed the 15 36Cl sites around the Fucino and, through a gaussian mixture algorithm, checked the hypothesis of common periods of activity throughout all the Fucino basin.

Slope failures and deep seated landslides are usually considered as the most efficient processes for hillslope erosion in active orogens. Erosion in the central Himalaya (Nepal) confirms such assertion (Morin et al., 2018), with in addition the probable predominance of the very large landslides in the erosive budget of the range (Marc et al., 2019).In this contribution, we report geological evidence for a giant rockslide that occurred around 1190 AD (14C burial age, 36Cl exposure age, and IRSL dating) in the Annapurna massif (central Nepal), and filled a wide glacial cirque (Sabche cirque) and the Seti valley farther downstream with a rock-avalanche deposit up to 1km thick, made of finely-crushed breccia. This rockslide, which involves a total rock volume of ~23 km3, decapitated the paleo-Annapurna IV, a paleo-summit culminating likely above 8000 m of altitude.Such giant rockslides are rare but not uncommon in central Himalaya with former description of pluri-kilometric rockslides involving up to ten cubic kilometres mass wasting (e.g. Weidinger et al., 2002). They have major implications for landscape evolution since they could represent the main mode of erosion of the high glaciated peaks, leading to the sudden reduction of ridge crest elevation by several hundred meters.They also have major implications on the fluvial network and how it responds to such massive and sudden supply of sediments. Downstream of the Seti river, the Pokhara Basin is filled by ~5 km3 of mostly conglomeratic sediment emplaced by fluvial, hyperconcentrated, or turbulent, sediment-laden flows. Extensive 14C dating of organic fragments found in the fine-grained units of the Pokhara sediments (Schwanghart et al., 2016; this study) provide robust constraints on the timing of aggradation. Onset of aggradation around 1200 AD (as well as the calcareous clasts whose only possible origin is the Sabche cirque) indicates that the conglomerates are the result of the active erosion of the Sabche rock-avalanche breccia. The aggradation lasted for about a century at an average rate of 1m/yr. During that period, the erosion of the fine-grained breccia has been extremely efficient and rapid: of the initial 27 km3 of rockslide debris, less than 10% can still be observed today in the Sabche cirque. During that period, the rate of sediment yield delivered by the Seti river was comparable to the highest measured values of post-volcanic eruption sediment transport. It led to an overwhelming content of carbonate-rich material in Narayani river sediments up to 300 km downstream, in the Narayani megafan in the middle of the Gangetic plain. Compared to the Narayani basin (30,000 km2), which exports annually ~0.05km3/yr of sediment, post-collapse erosion of the Sabche breccias (only 0.2% of the Narayani total basin area) would have increased this annual flux by a factor of 3 over 100-150 years.This particular example illustrates how the erosional/sediment routing system in active mountain range, as well as the landscapes, can be durably affected by one single extreme event.

Europe has experienced over the last years earthquakes of moderate magnitude (Mw 5-6), yet destructive, reminding us of the seismogenic potential of slowly deforming regions. Among them, the 2020 Mw 6.4 Petrinja earthquake ruptured the Petrinja-Pokupsko Fault (PPKF) in Central Croatia, about 50-km southeast of Zagreb, a region in which the caracterisation of seismogenic faults had been insufficiently studied before that event. Understanding the strain accommodation through time and space is critical for accurate assessment of the regional seismic hazard.Using field observations and high-resolution topographical data derived from airborne LiDAR (~10 cm resolution) and tri-stereo satellite images (Pléiades, resolution 50 cm), we accurately mapped the fault trace, underlined at several sites by geomorphic markers such as valleys, terrace risers, and alluvial fans that have recorded cumulative displacements ranging from 5 to > 50 m and potentially up to ~180 m. Along the studied section, our fault mapping is composed of a clear NW-SE-trending 10-km-long strand between Donja and Cepelis, and of 1-4-km-long right-stepping segments marked by a non-negligible vertical component. The southern strand is composed of 2-3 sub-parallel segments that accommodate the deformation within a < 500 m wide fault zone.We have identified several sites on the main southern strand where offsets have been accurately measured and where displaced markers have been sampled for cosmogenic nuclide exposure dating and radiocarbon datings. This will allow to estimate the slip-rate for this fault at different sites and over several time spans.The mapped fault appears very discontinuous with the deformation absorbed by a series of small fault sections rather than on a single fault strand. This likely reflects a recent transpressive deformation, with immature faults, in agreement with the source parameter of the 2020 Petrinja earthquake derived from seismology.Finaly, the 2020 coseismic surface ruptures affected the northern section of the PPKF, while the mapped cumulative displacements appears more prominent along the southern section. A better knowledge of the seismic history of this entire fault system is thus crucial for seismic hazard assessment of this area.

Long-term fault escarpments are built by the accumulation of individual earthquakes producing incremental surface displacements on the fault releasing crustal tectonic loading. Cumulative escarpment studies have revealed a spatial slip variability along active faults as well as a temporal variability with the alternation of phases of intense seismic activity over a short period of time followed by long periods of quiescence. Understanding this spatial and temporal slip variability on individual faults and over a complex fault system provide a better knowledge of co-seismic rupture extents, essential for estimating past earthquakes magnitude and for seismic hazard assessment.Up to now, most studies have focused on a timeframe over few seismic cycles, making it difficult to apprehend the rupture barriers persistence and cumulative slip distribution. Here, we aim at quantifying the slip variability over several timescales ranging from a few months to a few million years on the same fault.Our study focusses on the ~50 km-long Liri fault, SW of the Fucino basin. The fault is located at the contact between Cretaceous limestone and patches of Quaternary deposits locally convering Mio-Pliocene flysch sediments. Detailed mapping of the fault trace on high-resolution Digital Elevation Model (DEM) from UAV-acquired images, Pleiades images and Lidar together with field observations revealed changes in the morphological expression of the fault north and south of an important wind gap located at Capistrello. To the north, the faut trace is ~16 km-long located on the eastern side of ~2km-wide limestone ridge, reaching ~1300m asl elevation. Two bends in the fault trace, made of ~5km long segments, can be observed with the fault strike varying between N115° and N140°. In this northern section, the fault scarp appears subtle and we did not observe Quaternary deposits on the hanging wall. In the 30 km-long section, south of Capistrello, the cumulative scarp composed of numerous splays is evidenced by a sharp trace, offsetting several morphological surfaces and associated Quaternary sediment packages. Three major bends are observed in this section of the fault, separating 10 to 30 km-long segments striking between N110° and N160°. An alluvial surface offset by ~14 m of cumulative displacement was dated at ~35kyr using 36Cl cosmogenic exposure dating suggesting a minimum slip rate of 0.4 mm/yr. Other morphological markers that have accumulated displacement between ~10 and 70 m-high have also been sampled for 36Cl cosmogenic exposure dating. Moreover, we excavated two small trenches at the base of the fault scarp within the Quaternary deposits affected by the fault revealing 3 rupture-surfacing earthquakes over the last 2500 yr, the last one occurring after 1226 CE. We will present those results and will discuss how the displacement varies along the fault both in time and space.

Fault displacement can be a source of hazard for critical infrastructures located in the nearby of a capable fault. This issue is usually addressed with zonation and avoidance strategies, but sometime the facilities have not this option. An alternative approach to assess likelihood of exceeding a certain level of displacement for pre-existing infrastructures is the Probabilistic Fault Displacement Hazard Analysis. Different empirical approaches have been proposed since the early 2000s to assess the probability of occurrence and the probability of exceedance of certain values of displacement, for both Primary and Distributed faulting, starting from the fault parameters. We propose the methodological approach used to gain the needed parameters and the results of the PFDHA applied to the Anghiari Fault, a poorly constrained NE-dipping segmented normal fault located in the Upper Tiber Valley (Italy) and belonging to the well-known Altotiberina low-angle normal fault system.In order to constrain the fault geometry and to select sites suitable for paleoseismologic trenching we performed geological survey, morphotectonic analysis and geophysical investigations. To assess the capability of the fault and its rate of activity we carried out a paleoseimic campaign, investigating several segments of the Anghiari fault. To obtain a multiscale evaluation of the fault slip rate, we collected samples to date paleosurfaces displaced by the fault with the cosmogenic nuclides methodology. At the end we performed the PFDHA obtaining curves and maps of hazard for both primary and distributed faulting, managing the uncertainties through various rupture scenario involving different fault segment.

Active faults play a major role in relief building, partly through the accumulation of vertical co seismic displacement during major earthquakes. Triangular facets are geomorphic features recording normal fault cumulative displacements on relatively long time scales (10-100ka). To unravel the relationships between the rate at which slip accumulates on a fault scarp and the long-term evolution of triangular facets, we have to acquire quantitative datasets on normal fault slip rates at various timescales and rates of erosion of the facets.Here we present a study on facet build-up over 10-100 ka time range in the central Apennines in Italy. The normal fault systems that control the present tectonic activity of the range are very well studied with numerous detailed paleoseismological records. We focus on the Magnola-Velino fault system which displays well preserved triangular facets and accurate chronological constraints on the 10-20m high fault scarp located at the base of the facets. We combine high resolution morphometric analysis (gullies steepness, facets slope and others), using Digital Elevation Models derived from Pléiades imagery and a new dataset for cosmogenic nuclides concentration (36Cl) including 54 bedrock samples on 9 gullies and facets profiles above the scarps. Magnola-Velino fault system is 20-25km long, and morphometric parameters such as steepness index display a systematic evolution along strike. First measured 36Cl concentrations, on Magnola, range from 6 to 50 x104 at/g on gullies and 50 to 150 x104 at/g on facets, with systematic variations along strike. We document the joint evolution of geochronological data and morphological parameters for this fault system and compare it with existing constraints on long-term slip rate.

International audience; The footwall of the surface rupturing Paganica normal fault, the source of the 2009 L'Aquila earthquake (Mw 6.1) in the Central Apennines (Italy), was investigated using integrated geological and geomorphological approaches. The aim was to constrain the active tectonics by studying the Raiale River that orthogonally crosscuts the fault trace, where it provides a useful geomorphological marker of long-term fluvial incision and footwall uplift. Using morphostratigraphy and paleomagnetic analysis, the Plio-Pleistocene morphotectonic evolution of the area was reconstructed, comprising an ancient continental basin and paleolandforms that predate the footwall incision. Starting from the Late Early Pleistocene-Middle Pleistocene, fluvial dissection was mainly due to marked river downcutting triggered by significant activity of the Paganica Fault, which caused progressive base-level lowering. The Raiale River downcutting formed five Middle-Late Pleistocene fluvial terraces, that, along with absolute Optically Stimulated Luminescence (OSL) dating, allowed the identification of paleolongitudinal profiles with a diverging downstream configuration. Terrace dating yielded a minimum incision rate of 0.25 ± 0.02 mm/a, which only partially compensates the footwall uplift and can thus be considered as a minimum value for the Paganica Fault throw rate, which could reach up to ~0.45 mm/a. In parallel, using terrestrial cosmogenic nuclides, a denudation rate of 0.02-0.04 mm/a was measured on the summit of the footwall block. This denudation is in keeping with the drainage incision, suggesting a non-steady state for the fault footwall topography and a dominance of relief growth. Last, the analysis of the modern Raiale River longitudinal profile denoted an ungraded status, with two main knickzones that we interpret as transient forms due to tectonic perturbations, likely triggered by activity of the Paganica Fault during the end Early Pleistocene and the Late Pleistocene. Considering the 2009 L'Aquila earthquake coseismic rupture, we observe that the younger transience on the Raiale River longitudinal profile, if it is of tectonic origin, could have only been produced by much larger seismic events (i.e., Mw > 6.5) than those documented in the area by paleoseismological investigations. The collective results confirmed that in the Central Apennines, conditions of dynamic equilibrium are often not met, and that the persistence of transient perturbations induced by tectonics should be accounted for.

International audience

International audience

The earthquake with magnitude ML=6.2 that occurred on 29th December 2020 has caused significant material damage to objects and infrastructure in the towns of Petrinja, Sisak,Glina and the surrounding area. According to the satellite interferometry data, the coseismic and postseismic deformation area covers around 500 square kilometers. The existing geodetic benchmarks have been set in the affected towns, and their coordinates have been determined based on previous GPS campaigns. The GPS network was set up and adjusted at the State Geodetic Administration's request for geodetic monitoring of infrastructure and cadastral projects. These points are not primarily intended for high accuracy measurements at the level of a few millimeters, so their accuracy and the absolute shift concerning geodynamic processes in the region should be taken into account. Nevertheless, the data obtained by their observation after the earthquake can provide valuable information about the horizontal and vertical displacements with a certain level of confidence. The field survey has detected disappearance of a large number of benchmarks and some valuable information has been lost. Still, 58 points were found and observed and it has been concluded that 52 points are reliable and can be used for future research. Because the network of benchmarks is not developed in rural areas, there is a gap in the distribution of benchmarks in affected area. Therefore, the additional data was collected using the benchmarks established for the engineering and cadastral projects and studies. From a total of 67 points that have been found and observed, 42 points will be used. Along with the data collected in urban areas, there will be a total of 94 benchmarks. The accuracy of the geodetic benchmark measurements is at the centimeter level, while the values of deformation are at the level of a few decimeters. Therefore, the obtained data can be used to better assess the displacement recorded during the 29 December 2020 event. In the future, field research will focus on finding additional benchmarks to reach a better spatial distribution.

In the Central Apennines (Italy), up to now, no absolute dating directly based on the moraines has been carried out to constrain glacial oscillation. However, climatic constrains are often used in the Central Apennine to estimate long term (> 10 ka) fault slip rate. In addition slip rate assessments based on offset morphotectonic markers on the main branches of fault systems and encompassing several seismic cycles (> 10 ka) are sparse. This is particularly true for the Monte Vettore-Monte Bove fault system which triggered the 2016-2017 seismic sequence. We thus provide new assessment for the vertical slip rates along the Mt Vettore-Mt Bove fault system. Offset measurements were made using a 5-cm resolution DEM obtained through a drone survey and constrain a fault scarp height of 15.5 ± 1.4 m and a cumulative offset of 32-40.5 m. Samples were collected from the Valle Lunga terminal moraine at 1710 m asl and yield 36Cl exposure ages of 12.7 + 2.2/-1.9 ka while the flat, abraded surface located on top of the tectonic scarp yield 36Cl exposure ages of 23.4 + 5.3/-4.3 ka. Assuming the offset started to accumulate when climate conditions allow its preservation, thus once the surface was abandoned, we constrain a vertical slip rate of 1.2 ± 0.2 mm/yr along the master branch of the Mt Vettore normal fault. This rate is higher than the ones previously obtained from trenches along secondary splays of the Mt Vettore-Mt Bove and on the Norcia fault systems. Besides, the yielded chronology for the last glacial maximum in that area at ~23 ka is in good agreement with the timing previously proposed for the LGM in the Apennines.

International audience; The Mw 6.5 Norcia earthquake occurred on 30 October 2016, along the Mt Vettore fault (Central Apennines, Italy), it was the largest earthquake of the 2016-2017 seismic sequence that started 2 months earlier with the Mw 6.0 Amatrice earthquake (24 August). To detect potential slow slip during the sequence, we produced Interferometric Synthetic Aperture Radar (InSAR) time series using 12- to 6-day repeat cycles of Sentinel-1A/1B images. Time series indicates that centimeter-scale surface displacements took place during the 10 weeks following the Norcia earthquake. Two areas of subsidence are detected: one in the Castelluccio basin (hanging wall of the Mt Vettore fault) and one in the southern extent of the Norcia earthquake surface rupture, near an inherited thrust. Poroelastic and viscoelastic models are unable to explain these displacements. In the Castelluccio basin, the displacement reaches 13.2 +/- 1.4 mm in the ascending line of sight on 6 January 2017. South of the Norcia earthquake surface rupture (a zone between the Norcia and Amatrice earthquakes), the postseismic surface displacements affect a smaller area but reach 35.5 +/- 1.7 mm in ascending line of sight by January 2017 and follow a logarithmic temporal decay consistent with postseismic afterslip. Our analysis suggests that the structurally complex area located south of the Norcia rupture (30 October) is characterized by a conditionally stable frictional regime. This geometrical and frictional barrier likely halted rupture propagation during the Amatrice (24 August) and Norcia (30 October) earthquakes at shallow depth (

Item S1 (additional information on the modeling) and Item S2, (additional information on the sampling, analysis, and obtained dataset).

Active deformation in the Central Apennines is mostly accommodated by NW-SE normal faults systems that produce moderate to large earthquakes at shallow depth. Recent examples include the 1915 Mw≈7 Avezzano earthquake (Fucino basin) and the 2009 Mw=6.1 L’Aquila earthquake (Aterno basin) which were both associated with major loss of life and massive damage to buildings and infrastructure. Here, we study the 40-km-long Ovindoli – Piano di Pezza – Campo Felice – Monti d’Ocre (OPCM) fault system, a major NNW-SSE system that potentially links the Fucino and the Aterno fault-systems. The OPCM exhibits linear and arcuate sections with four main segments and borders the eastern margin of the Aterno basin. Paleo-earthquake rupture data on the Piano di Pezza (PPF) and Campo Felice (CFF) faults exhibit remarkable synchronicity with the Fucino fault system, with the most recent surface-rupturing earthquake likely occurring in the XIVth century. In order to better understand the relationships between and earthquake rupture scenarios, we focus on the basin geometry and fault surface expression of the Piano di Pezza fault combining geomorphology and subsurface geophysics. We map the fault trace with unprecedented detail using terrestrial laser scanner surveys and quantify surface deformation affecting alluvial fans as well as glacial moraines. We obtain a mean vertical offset of 2.5 m +/- 0.3 m for the most recent features, well in agreement with paleoseismological data. Furthermore, we document slip distributions at different time scales along strike with a maximum value at the connection between the PPF and the OF. Beneath the scarp, geophysical data reveal a complex faulting geometry with several parallel strands and two minor blind splays. Electrical resistivity tomography images show a cumulative vertical offset of ~ 15 m affecting an interface attributed to the Last Glacial Maximum and confirm the high vertical slip across the fault zone. Gravimetric anomalies across the basin also indicate the sedimentary fill has recorded a maximum finite cumulative throw of the PdP fault system of 110-140 m. This suggests a maximum vertical slip rate of 0.2-0.3 mm/year since the Pleistocene, which contrasts with the high post-LGM slip rate estimated from trenches. Overall, our observations suggest that the arcuate PPF originally formed as a reverse fault during the Mio-Pliocene compressive stage and is now reactivated as an extensional horsetail-like feature by ruptures along a major strike-slip fault (OF). This finding points to the PPF as mostly built through ruptures along the OF leaking onto an inherited structure. The time-varying slip rates may also denote an episodic behavior marked by short periods of high seismic activity (a few centuries) and long intervals of seismic quiescence (a few millennia). Furthermore, possible earthquake rupture scenarios along the OPCM may encompass the whole OPCM fault system (cumulative length ca. 40 km) or rupture termination along the PPF (cumulative length ca. 15-20 km) with significantly different impacts over the populated Fucino and Aterno basins.

A driving motivator in many active tectonics studies is to learn more about the recurrence large and potentially destructive earthquakes, providing the means to assess the respective fault’s future seismic behavior. Doing so requires long records of earthquake recurrence. The lack of sufficiently long instrumental seismic records (that would be best suited for this task) has led to the development of other approaches that may constrain the recurrence of surface rupturing earthquakes along individual faults. These approaches take different forms, depending on the specific tectonic and geographic conditions of an investigated region.For example, around the Mediterranean Sea, we frequently find bedrock scarps along normal faults. Assuming that bedrock (i.e., fault free-face) exposure is caused by the occurrence of sub-sequent large earthquakes, we may measure certain rock properties to constrain the time and size of past earthquakes as well as the fault’s geologic slip-rate. A now-classic example in this regard is the measurement of 36Cl concentrations along exposed fault scarps in limestones.For the presented study, we looked at another property of the exposed fault free-face, namely its morphologic roughness. We aim to identify whether fault free-face roughness contains information to constrain earthquake occurrence and fault slip-rates following the assumption that sub-sequent exposure to the elements and sub-areal erosional conditions may leave a signal in how rough (or smooth) the fault free-face is (assuming a somewhat uniform pre-exposure roughness). Here, we present observations of fault free-face surface roughness for the Mt. Vettore fault (last ruptured in 2016) and the Rocca Preturo fault (The underlying models of fault free-face morphology were generated using the Structure-from-Motion approach and a large suite of unregistered optical images.). Employing different metrics to quantify morphologic roughness, we were indeed able to observe a) an increase in surface roughness with fault scarp height (i.e., longer exposure to sub-areal erosion causes higher roughness), and b) distinct (rather than gradual) changes in surface roughness, suggesting a correlation to individual exposure events such as earthquakes. Hence, fault free-face morphology of bedrock faults may serve as an additional metric to reconstruct earthquake recurrence patterns.

The interaction between sedimentation/erosion and faulting represents one of the most intriguing topics in landscape and tectonics evolution. Recently, several studies attempted to unravel this issue but only few of them have been able to document the feedback between faulting and sedimentary loading. Here, we focus on how the sediment loading/unloading influences the dynamic of the faults system taking as study case the Fucino Basin in Central Apennines (Italy). The Fucino Basin represents a remarkable case study with respect to the other main extensional basins in the Apennines, because of its large dimension, rectangular shape, significant sediment thickness and more important, its endorheic nature throughout its evolution.We present a detailed structural analysis all around the basin, investigating the kinematic and geometry of each main fault strand. The slickensides analysis reveals multiples families of slip-vectors and timing of activity which suggest a changing from N240° to N200° occurred during middle-Pleistocene. Moreover, using a simple isostatic model, we estimate that up to the 30% of the total geological displacement of the faults, which overall ranges from 0.5 to 3.5 km, is related to the sediments loading/unloading. Then, we demonstrate a positive feedback between sedimentation and faulting which may also lead to a re-organization in fault-kinematic related to a significant increasing in the vertical stress. Finally, we propose a conceptual model to support the permanent endorheic configuration of the Fucino basin, mainly related to a fault-slip increasing and kinematic changing due to the sediment loading.

In Central Italy more than 393 thousands people live in villages and towns located at less than 5 km distance from a known, mapped, active fault, capable of generating Mw>6 earthquake. Improving seismic risk estimates in such places requires the use of (i) informative databases of active faults and (ii) the implementation of appropriate building-codes. The current level of knowledge regarding activity of active faults in Central Italy has been stored in a recently compiled database (160 slip rates estimates for 88 faults). Given the complex nature of fault ruptures, we adopted a multi-fault rupture approach (SHERIFS) that accounts for both individual ruptures and multi-fault complex ruptures, involving more than one seismogenic fault section. Our earthquake rupture forecast model includes 1249 possible combinations of fault ruptures with lengths ranging from 7 to 42 km. Slip rates and associated errors are used to estimate recurrences of the ruptures assuming a Gutenberg-Richter frequency-magnitudedistribution. The computed distribution is validated against the CPTI15 catalogue.The multi-fault model approach and a seismogenic area approach are used to estimate damages based on published typological fragility curves for typical building classes derived from 30 years of data in Italy (Rota et al., 2006) assuming earthquake occurrence for the faults follows a Poisson time-independent process. Two fragility curves are considered here: one for reinforced concrete designed according to seismic regulations and one for masonry with irregular layout and without tie rods and tie beams, a typical typology for the region. Expected levels of damage for 150 villages and towns in Central Italy are computed for all damage states considering a 50 years risk target period. Results obtained with the fault approach show a much higher variability of the estimated risk depending on the location of the village/town w.r.t. the fault system and the hanging-wall/footwall location. The probability of collapse in 50 years for a typical masonry building ranges between 0.01 and 0.07 in the fault approach and 0.01 and 0.04 for the area approach. For both approaches, the probability of collapse for reinforced concrete buildings is ~90 % less than that for typical masonry structures. Even if this can be considered obvious, it must be underlined that most buildings in Italy were built before 1975 (before the first applicative decree of the seismic Italian law No. 64 of 1974). Thanks to the availability of the detailed database of active faults a strategy to prioritize resources for seismic risk reduction could be adopted. Rota, M., Penna, A. & Strobbia, C. (2006). Typological fragility curves from Italian earthquake damage data. First European Conference on Earthquake Engineering and Seismology Geneva, Switzerland, 3-8 September 2006 Paper Number: 386

Aix-Marseille University launched the VirtuaField project whose objective is to integrate DOMs into a VR application to provide students with a pedagogical tool enabling learning field practice.Indeed, students have few occasions to train in the field during their academic curricula. Field trips are expensive and require a complex logistics. Nowadays, the photogrammetry or LIDAR techniques allow geoscientists to obtain High-Resolution 3D representations of outcrop geometries and textures, often termed as Digital Outcrop Models (DOM). DOMs are already used as pedagogical supports for practical exercises on computers such as fault throw or seismic occurrence calculation, or modelling 3D geological structures from outcrop interpretations. However, these exercises do not cover all required skills to gain autonomy and consistence in the field, such as the pertinent observation sampling. The computer engines are not convenient support for that task because the visualization, although in 3D, still depends on a 2D screen and does not preserve the 1:1 scale, which is of paramount importance for Geoscience interpretations.The Virtual Reality (VR) technique is the ultimate way to provide a full 3D view, which can preserve the 1:1 scale, while benefiting from the numerical nature of the support (DOMs, DEM).First prototypes were provided by the VR2Planets company from the case study of La Fare les Oliviers (SE France), which shows diffuse fractures and fracture corridors, in addition to sedimentological and geomorphological structures. The prototypes have been tested in training experiences with volunteer students. Surveys have been performed in order to obtain feedbacks from students on the ability of the VirtuaField application to gain field skills, but also on the more pertinent way to design the pedagogical tools. The synthesis of these feedbacks will be presented as well as a first outline of the pedagogical guidelines on using VR tools for educational purposes.

Correction for ‘Mass-shift mode to quantify low level 129I in environmental samples by ICP-MS/MS’ by Coralie Carrier et al., J. Anal. At. Spectrom., 2022, 37, 1309–1317, https://doi.org/10.1039/D2JA00128D.

International audience; The dynamics of carbonate-dominated landscapes is still debated, and first-order questions pertaining to the respective importance of chemical and mechanical weathering processes or the influence of climatic variability on denudation rates are largely open. To address these issues, we investigate the denudation pattern across a climatic gradient in Provence, SE France. We focused on a series of major carbonate mountain ranges with elevation spanning 200 to 2000 m and associated with >2-fold variations in mean annual temperature and precipitation. We collected 25 samples from 10 different mountain ranges and quantified denudation rates through the measurement of their Cl-36 concentrations in order to explore tectonic and climatic controls on these carbonate landscapes evolution. We observe that most of our samples experience denudation rates in the 30-60 mm/ka range (averaged over 5 to 40 ka), with no evident dependence on variations of mean annual temperature or precipitation. One range (Lure mountain) stands out as a significant outlier, with much higher denudation rates (>100 mm/ka) than adjacent sites (Ventoux mountain) at the same elevation and experiencing similar present-day environmental conditions. We explore in details the climatic, tectonic and geomorphological contexts of these two ranges in order to understand the reasons for this apparent 3-fold difference in denudation rates. A regionally-documented major Holocene hillslope destabilization event appears to be a likely candidate to explain the observed lower Cl-36 concentrations at the top of the Lure mountain. At longer wavelengths, our regional dataset shows no clear control of modem precipitation gradients on denudation rates, consistent with previous observations in landscapes underlain by other lithologies.

International audience; Key-points Folded alluvial surfaces and balanced cross-section constrain post-LGM and Neogene shortening-rates Decrease in shortening-rate and change in compression direction are inferred at 1-2 Ma Kinematic reorganization is best explained by a shift from Nubia-driven to Adria-driven convergence Abstract The eastern Southern Alps are located at the northern tip of the Adria microplate, which imposes 2.0-2.5-mm/yr of N-S-convergence relative to stable Eurasia. We map surface evidence of recent folding/faulting in this area from a 5-m-DEM. In the eastern part of the belt, observations reveal a 30-km-wide zone of active folding composed of at least five growing anticlines. The most recent ones warped the post-glacial alluvial surface by

International audience; In this study, we present a new glacial chronology based on 20 in situ-produced 36Cl-based cosmic ray exposure datings from moraine boulders and bedrock from the Throne of Zeus (TZ) and Megala Kazania (MK) cirques on Mount Olympus. The 36Cl derived ages of glacial landforms range from 15.6 ± 2.0 to 0.64 ± 0.08 ka, spanning the Late-glacial and the Holocene. The Late-glacial, recorded in both cirques, is partitioned in three distinct phases (LG1-3): an initial phase of moraine stabilization at 15.5 ± 2.0 ka with subsequent deglaciation starting at ∼14 ka (LG1), followed by a shift to marginal conditions for glaciation at 13.5 ± 2.0 ka (LG2), sustained by large amounts of wind-blown snow, despite regional warming. Glacial conditions returned at 12.5 ± 1.5 ka (LG3) and were characterized by low air temperatures and glacier shrinking. The Holocene glacial phases (HOL1-3) are recorded only in the MK cirque, likely due to its topographic attributes. An early Holocene glacier stillstand (HOL1) at 9.6 ± 1.1 ka follows the regional temperatures recovery. No glacier activity is observed during the mid-Holocene. The Late Holocene glacier expansions, include a moraine stabilization phase (HOL2) at 2.5 ± 0.3 ka, during wet conditions and solar insolation minima, while (HOL3) corresponds to the early part of the Little Ice Age (0.64 ± 0.08ka). Our glacial chronology is coherent with glacial chronologies from several cirques along the northeast Mediterranean mountains and in pace with numerous proxies from terrestrial and marine systems from the north Aegean Sea.

Located at the northeastern corner of the Adria microplate, the Alps-Dinarides junction represents a key region for understanding how the Adria microplate interacts with stable Europe. However, little is known on how the present-day deformation imposed by the rotation of the Adria microplate is absorbed across the Dinarides. Using morphotectonic analysis based on satellite and aerial images, accurate topographical maps, and digital elevation models combined with field investigations, we mapped in detail the three main active faults of the Northern Dinarides. Geomorphic and geological cumulative displacements ranging from a few meters to several kilometers have been identified on those faults and dated for the most recent ones using 36 Cl exposure dating. Those results yielded a total right-lateral motion of 3.8 ± 0.7 mm/yr oriented N317. Comparing our results with the motion expected from Adria rotation models suggests that the Northern Dinarides absorbs most of the predicted Adria-Eurasia motion, thus representing the eastern boundary of the microplate. However, a significant E-W component is lacking, suggesting that part of the stress imposed by the microplate rotation is transferred farther to the east. Finally, bounds placed on the Plio-Pleistocene kinematics confirm that faulting onset occurred during the Early Pliocene and evidence a significant kinematic change at the Early/Middle Pleistocene boundary.

Morphological and geological observations reveal that most Apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long. Although these faults have undergone numerous paleoseismological investigations, quantitative data remain crucially lacking for a large number of fault segments. Because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future, we investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto-Rotella-Aremogna fault system in the Apennines. We collected 44 samples from the Pizzalto fault plane exhumed during the Holocene and analyzed the 36Cl and rare earth element (REE) contents. Together, the 36Cl and REE concentrations show that at least six events have exhumed 4.4 m of the fault scarp between 3 and 1 ka, with slip per event values ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 kyr. The Rotella-Aremogna-Pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1.2 kyr and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years.

The Doruneh Fault System (DFS) is one of the major active strike-slip faults in the Arabia-Eurasia collision zone. Despite its geological activity, no large (M ≥ 6.5) historical or instrumental earthquakes have been recorded along it. To date, the rate and distribution of slip, as well as the seismic behavior of the DFS, have been unknown. We reconstructed 67 geomorphic offsets recorded by three successive alluvial abandonment surfaces (Q1, Q2, and Q3) displaced along the western (WFZ) and central (CFZ) fault zones. The determined ages of ~12, ~36, and ~120 ka, using in situ-produced 10 Be and 36 Cl cosmogenic nuclides for theses surfaces, allowed to estimate three sets of individual left-lateral slip rates and consequently to describe the spatiotemporal distribution of slip along the CFZ and WFZ. The slip rates averaged over time intervals of ~36 and ~120 ka reveal variable slip rates along length but similar slip rates at a point with a maximum rate of ~8.2 mm/yr. During the Holocene, however, the fault slip behavior appears more complex, with a maximum rate of ~5.3 mm/yr. The CFZ is divided into two ~4 km apart segments, with symmetrical slip distributions relative to a persistent boundary, which has not been ruptured over the last ~12 ka. The maximum length of seismic fault segments varies from 70 to 100 km, which could produce earthquakes with a magnitude of M w 7.2–7.4. This emphasizes the necessity of segmentation models for long strike-slip faults that may not necessarily rupture along their whole length during a single earthquake.

This study investigates the possibility of Holocene glaciation on Mount Olympus (Greece) with a respective local temperature–precipitation equilibrium line altitude (TP-ELA) at c. 2200 m a.s.l., based on geomorphologic and paleoclimatic evidence. At present, the local TP-ELA is situated above the mountain’s summit ( c. 2918 m a.s.l.), but permanent snowfields and ice bodies survive within Megala Kazania cirque between c. 2400 and c. 2300 m a.s.l., because of the cirque’s maritime setting that results from its close proximity ( c. 18 km) to the Aegean Sea and of the local topographical controls. The snow and ice bodies occupied a considerably larger area and attained a stabilization phase between AD 1960 and 1980, also manifested from aerial photographs, a period characterized by increased winter precipitation ( Pw) with subsequent TP-ELA depression to c. 2410 m a.s.l. Mid- to late-20th-century Pw and TP-ELA variations exhibit negative correlations with the winter North Atlantic Oscillation index (NAOw) at annual and multidecadal (30 years) timescales. Late Holocene (AD 1680–1860) reconstructed summer mean temperatures were lower by Ts w phases, thus bracketing this time interval as a favorable one to glacial formation and/or advance. Millennial-scale annual precipitation reconstructions at the hypothesized TP-ELA ( c. 2200 m a.s.l.) point the period between 8 and 4 kyr BP as another glacier-friendly candidate. The mid-Holocene rather simplistic sequence of potential glacial advance phase was disturbed by short-lived cold climatic deteriorations, well-documented over the northern Aegean region that may partly explain the multicrested shape of the highest ( c. 2200 m a.s.l.) morainic complex of Megala Kazania cirque.

Denudation of carbonate terrains dominated by chemical weathering can be treated as a rain gauge proxy, because the mass lost by dissolution over time is proportional to the time-integrated precipitation. Therefore, the denudation history of carbonate landscapes may provide paleoprecipitation data and shed light on the interactions between climate, denudation, and tectonic uplift. We apply this approach to constrain 10 4 –10 7 yr average precipitation along the western Dead Sea Rift (DSR) margin, which is underlain predominantly by carbonate rocks and maintains a climatic gradient from Mediterranean to hyperarid along its axis and between its windward and leeward flanks. The comparison between total denudation (from a Turonian datum), denudation rate calculations (from in-situ 36 Cl measurements), and present-day mean annual precipitation shows that (1) total denudation correlates with denudation rates and both correlate with precipitation, and (2) over the lifetime of the range (10–20 m.y.), the effective precipitation gradient across the range was higher than at present by at least 40% on average. Along the ∼450-km-long range, the denudation gradient is probably compensated by isostatic uplift. We suggest that along the western DSR margin, and possibly in other carbonate terrains, precipitation (to a threshold precipitation of ∼1000 mm yr –1 ) controls the long-term denudation rate and the subsequent compensating uplift.

Carbonate minerals, unlike silicates, have the potential to dissolve almost completely and with high efficiency. Thus, in carbonate terrains denudation rate and style (the governing process of denudation, mechanical or chemical) should be more sensitive to climatic forcing. Using 36 Cl measurements in 39 carbonate bedrock and sediment samples, we calculate long-term denudation rates across a sharp climatic gradient from Mediterranean to hyper-arid conditions. Our samples were collected along the Arugot watershed, which drains the eastern flank of the Judea Range (central Israel) to the Dead Sea and is characterized by a pronounced rain shadow. Denudation rates of flat-lying bedrock outcrops sampled along interfluves differ by an order of magnitude from ∼20 mm ka −1 in the Mediterranean zone to 1–3 mm ka −1 in the hyper-arid zone. These rates are strongly correlated with precipitation, and thus reflect the importance of carbonate mineral dissolution in the overall denudation process. In contrast, denudation rates of steep bedrock surfaces depend on the hillslope gradient, but only in the hyper-arid climate zone, indicating that mechanical processes dominate the overall hillslope denudation within this zone. The dominance of slope-dependent mechanical erosion in the hyper-arid zone is also reflected by an increase in spatially-average denudation rates from 17–19 mm ka −1 in the Mediterranean–semi-arid zones to 21–25 mm ka −1 in the hyper-arid zone. These higher rates are attributed to clast contribution from steep slopes under arid climate. This suggests an increased importance of mechanical processes to the overall denudation in the hyper-arid zone. We demonstrate that the transition between chemically-dominated denudation to mechanically-dominated denudation occurs between 100 and 200 mm of mean annual precipitation. Long-term denudation rates across the Judea Range indicate that between Mediterranean and hyper-arid climates, chemical weathering rates are limited by precipitation. Nevertheless, in more humid climates, chemical weathering rates are apparently limited by the rates of carbonate mineral dissolution. This study demonstrates that carbonate terrains have the capacity to shift between mechanically and chemically dominated denudation in response to changes in precipitation. Similar transitions in response to changes in temperature or the level of tectonic activity have been previously reported. We suggest that the abrupt nature of such transitions can be primarily attributed to the efficiency of carbonate dissolution processes and the competition between surface and subsurface drainage systems in carbonate terrains.

International audience; Over 30 samples from bedrock and boulders from the Veliki vrh rock avalanche have been collected for surface exposure dating. The limestone rocks have been radiochemically treated to isolate and determine long-lived Cl-36 by accelerator mass spectrometry. It could be shown that the Veliki vrh rock avalanche from the KoSuta Mountain (Slovenia) event can be very likely linked to one of the major historical earthquakes in Europe happening on the 25th of January 1348. Taken into account independently determined denudation rates, inherited Cl-36 originating from pre-exposure at shallow depths (20-55 m) could be calculated. The high amount of inherited Cl-36, i.e. 17-46% of the total Cl-36, makes this site not suitable for a precise determination of the Cl-36 production rate as it was originally anticipated. Veliki vrh is a ``classic'' rock avalanche of high velocity. The slope failed in the upper part with a translational slide predominantly along the bedding planes, whereas dynamic fragmentation is the cause for further crushing of the material and the long runout. (c) 2014 Elsevier B.V. All rights reserved.

The abundant production of in situ cosmogenic 36Cl from potassium renders 36Cl measurements in K-rich rocks or minerals, such as K-feldspars, potentially useful for precisely dating rock surfaces, either in single-nuclide or in multi-nuclide studies, for example combined with 10Be measurements in quartz. However, significant discrepancies in experimentally calibrated 36Cl production rates from spallation of potassium (36PK-sp), referenced to sea-level/high-latitude (SLHL), limit the accuracy of 36Cl dating from K-rich lithologies. We present a new 36Cl calibration using K-feldspars, in which K-spallation is the most dominant 36Cl production pathway (>92% of total 36Cl), thus minimizing uncertainties from the complex multi-pathway 36Cl production systematics. The samples are derived from boulders of an ∼13.4 ka-old landslide in the Swiss Alps (∼820 m, 46.43°N, 8.85°E). We obtain a local 36PK-sp of 306 ± 16 atoms 36Cl (g K)−1 a−1 and an SLHL 36PK-sp of 145.5 ± 7.7 atoms 36Cl (g K)−1 a−1, when scaled with a standard scaling protocol (‘Lm’). Applying this SLHL 36PK-sp to determine 36Cl exposure ages of K-feldspars from 10Be-dated moraine boulders yields excellent agreement, confirming the validity of the new SLHL 36PK-sp for surface exposure studies, involving 36Cl in K-feldspars, in the Alps.

We recover the Holocene earthquake history of seven seismogenic normal faults in the Fucino system, central Italy. We collected 800 samples from the well-preserved limestone scarps of the faults and modeled their 36Cl concentrations to derive their seismic exhumation history. We found that > 30 large earthquakes broke the faults in synchrony over the last 12 ka. The seven faults released strain at the same periods of time, 12-9 ka, 5-3 ka, and 1.5-1 ka. On all faults, the strain accumulation and release occurred in 3-6 ka supercycles, each included a 3-5 ka phase of slow (≤ 0.5-2 mm/yr) strain accumulation in relative quiescence, followed by a cluster of three to four large earthquakes or earthquake sequences that released most of the strain in

The HVE 5 MV ASTER AMS national facility at CEREGE was accepted in 2007. Since then we have continued to optimize performance for 36Cl. Cl-36 analyses use AgCl, a Cs negative ion sputter source, Ar stripping to +5 in the terminal of the Tandetron™ accelerator at 5 MV and a silicon nitride post-acceleration stripper foil to enhance suppression of 36S relative to 36Cl. The major challenges to obtaining the desired performance for Earth science applications are ion source memory, mass fractionation effects, 36S isobar suppression and sensitivity. Redesign of the SO110 ion source by HVE to change the size of the aperture and the shape of cathode significantly reduced ion source memory to less than ∼0.1%, a level that can be compensated for by matching standards to samples. We observe small systematic drifts in 35Cl/37Cl ratios over time, the source of which is not yet determined. Measurement of standards indicates that this effect limits the precision of 35Cl/37Cl ratio determination to about 2%. 36S is suppressed in several ways. First, the sample chemistry has been designed to reduce S to low levels. Second, cathodes are constructed of low-S nickel, enabling direct target loading without the use of AgBr pre-packing. Third, a post-acceleration Si3N4 stripper foil differentially absorbs energy from 36Cl and 36S. A subsequent electrostatic deflector is then able to suppress 36S by a factor of ∼240 relative to 36Cl. Differential energy loss in the detector further suppresses 36S by about 10−4, for an overall suppression factor of 4 × 10−7. 36S count rates are typically equivalent to a background 36Cl/Cl of ∼10−15. At typical 35Cl currents of ∼20 μA Cl5+ samples with 36Cl/35Cl of 6 × 10−14 can be measured to ±5% statistical uncertainty with 1 h of analysis time. Typical machine blanks have 36Cl/Cl ∼2 × 10−15.

Modelling the evolution of the concentration of in-situ produced cosmogenic nuclides as a function of depth (depth-profile) has been developed to allow determining both the exposure duration and the denudation rate affecting geomorphic features. However, material sampled through surficial deposits may exhibit an inherited component resulting from exposure to cosmic rays before deposition. In case of homogeneous inheritance, this inherited component may be estimated through sampling at increasing depths and subsequently subtracted. In case of variable inheritance, the measured concentrations are scattered and the random distribution of the depth-profile concentrations prevents modelling confidently a depth-profile and precludes constraining an exposure duration. Often observed in desert and endorheic regions, this greatly restricts the possibilities to determine an accurate abandonment age of alluvial surfaces in such environments. Provided the denudation is demonstrated negligible, a method for determining a more accurate range of minimum inheritance, hence a more accurate maximum abandonment age for a given alluvial surface, is proposed. This method, based on the rejuvenation of depth-profile samples, relies on the simple hypothesis that at least one of the depth-profile samples would be emplaced with no or negligible inherited component and on the obvious principle that none of analysed sample has been emplaced with a negative cosmogenic nuclide concentration. The method consists then in determining which of the measured depth-profile sample may have been emplaced with a null CRE concentration; i.e., with a zero inheritance value. This requires to calculate the in-situ duration of exposure needed to reach the concentration measured for each depth-profile sample and to retain the one that provides the smallest in-situ exposure duration. Several examples from alluvial surfaces of central Iran illustrate the profile rejuvenation method and highlight a variable inheritance ranging between 1.5 × 10 5 and 16.1 × 10 5 at/g (SiO 2 ) for terraces whose abandonment ages range from ten to several hundreds of ka.

Since its discovery, the Chauvet cave elaborate artwork called into question our understanding of Palaeolithic art evolution and challenged traditional chronological benchmarks [Valladas H et al. (2001) Nature 413:419–479]. Chronological approaches revealing human presences in the cavity during the Aurignacian and the Gravettian are indeed still debated on the basis of stylistic criteria [Pettitt P (2008) J Hum Evol 55:908–917]. The presented 36 Cl Cosmic Ray Exposure ages demonstrate that the cliff overhanging the Chauvet cave has collapsed several times since 29 ka until the sealing of the cavity entrance prohibited access to the cave at least 21 ka ago. Remarkably agreeing with the radiocarbon dates of the human and animal occupancy, this study confirms that the Chauvet cave paintings are the oldest and the most elaborate ever discovered, challenging our current knowledge of human cognitive evolution.

The chauvet cave discovery in 1994 has challenged our archeological, art and chronological benchmarks previously admitted and based on the chronological stylistic framework. The aim of this study is dating of the major rockfalls, which have closed the Chauvet cave to the human and animals. This work shows the results of the geomorphological approach combining high-resolution topographic survey (terrestrial LiDAR) and cosmogenic dating. The rockfall scars and rockfall deposit 3D analysis has permitted to reconstruct the Chauvet cave paleo entrance. The rock sampling strategy is based on the existence of three rockfall scars on the rockwall overhanging the Chauvet cave. All the 36Cl production factor was considered and both of them are derived from the 3D topographic. These results allow establishing a coherent and absolute chronological framework of the Chauvet cave entrance for 34,000 years until its definitively and sudden closure there 22, 000 years., La découverte de la grotte Chauvet-Pont-d Arc, en 1994, et surtout l'âge des représentations préhistoriques, ont bouleversé les schémas jusque-là admis sur l'art pariétal. Ce travail de recherche géomorphologique, qui s 'insère dans le cadre des études scientifiques pluridisciplinaires menées sur cette cavité, porte sur le processus et la datation de la fermeture qui a rendu inaccessible cette grotte aux Hommes et aux animaux de la Préhistoire, suite à l'accumulation d'un dépôt d'écroulement dans le paléoporche de la grotte. L'analyse 3D de la niche d'arrachement et de la masse écroulée a été complétée par une étude chronologique via l'utilisation de l'isotope cosmogénique du 36Cl. Le détachement du pan de paroi à l'origine de la fermeture de la grotte préhistorique a mis au jour une nouvelle surface auparavant non exposée aux rayonnements cosmiques. La stratégie d'échantillonnage a été guidée par l'identification de plusieurs niches d'arrachement révélées sur la paroi par des mesures topographiques au LiDAR terrestre. Enfin, les facteurs de production ont été contraints à partir des connaissances géométriques et géomorphologiques du site. Ces résultats permettent d'établir un cadre cohérent et absolu de l'évolution de l'entrée de la grotte Chauvet depuis 34 000 ans jusqu'à sa fermeture brutale et définitive il y 22 000 ans., Sadier Benjamin, Benedetti Lucilla, Delannoy Jean-Jacques, Bourlès Didier, Jaillet Stéphane, Arnaud Judicaël, Jarry Benoit, Vermorel Guillaume, Geneste Jean-Michel. Datations 36Cl de la fermeture de la grotte Chauvet, implications géomorphologiques et archéologiques. In: Collection EDYTEM. Cahiers de géographie, numéro 13, 2012. Karsts, Paysages et Préhistoire. pp. 63-78.

SUMMARY Be and 36 Cl cosmic ray exposure (CRE) and optically stimulated luminescence (OSL) dating of offset terraces have been performed to constrain the long-term slip rate of the Dehshir fault. Analysis of cosmogenic 10 Be and 36 Cl in 73 surface cobbles and 27 near-surface amalgamscollectedfrominsetterracesdemonstratestheoccurrenceofalowdenudationrateof 1mM a −1 and of a significant and variable inheritance from exposure prior to the aggradation of these alluvial terraces. The significant concentrations of cosmogenic nuclides measured in the cobbles collected within the riverbeds correspond to 72 ± 20 ka of inheritance. The mean CREageofthesurfacesamplescollectedontheolderterraceT3is469 ±88kabuttheanalysis of the distribution of 10 Be concentration in the near-surface samples discard ages older than 412 ka. The mean CRE age of the surface samples collected on terrace T2 is 175 ± 62 ka but the 10 Be depth profile discard ages older than 107 ka. For each terrace, there is a statistical outlier with a younger age of 49.9 ± 3.3 and 235.5 ± 35.4 ka on T2 and T3, respectively. The late sediments aggraded before the abandonment of T2 and inset levels, T1 b and T1a, yielded OSL ages of, respectively, 26.9 ± 1.3, 21.9 ± 1.5 and 10.0 ± 0.6 ka. For a given terrace, the OSL ages, where available, provide ages that are systematically younger than the CRE ages. These discrepancies between the CRE and OSL ages exemplify the variability of the inheritance and indicate the youngest cobble on a terrace, that minimizes the inheritance, is the most appropriate CRE age for approaching that of terrace abandonment. However, the upper bound on the age of abandonment of a terrace that is young with respect to the amount of inheritance is best estimated by the OSL dating of the terrace material. For such terraces, the CRE measurements are complementary of OSL dating and can be used to unravel the complex historyofweatheringandtransportinthecatchmentofdesertalluvialfans.Thiscomprehensive set of dating is combined with morphological offsets ranging from 12 ± 2t o 380± 20 m to demonstrate the Dehshir fault slips at a rate in the range 0.9 mm yr −1 –1.5 mm yr −1 .T he variable inheritance exemplified here may have significant implications for CRE dating in arid endorheic plateaus such as Tibet and Altiplano.

Evaluating the timing and size of past earthquakes is a constant challenge in palaeoseismology. Here, we show that rare earth element (REE) concentrations can be used to constrain the number and slips of major past earthquakes. We focus on one of the rare faults worldwide – the Magnola normal fault, Italy – whose Holocene earthquake history is precisely known. We analysed 42 samples from along the 10 m that form the surface of the well-preserved seismically exhumed fault scarp and seven samples extracted from the fault plane section buried in the ground. We show that the first metre of soil contaminates the scarp rocks, producing a marked concentration ‘peak’ in REE. Similar peaks are recognized on the exhumed scarp, at positions that coincide with the transitions between the known past ruptures. We conclude that the REE peaks locate palaeoground levels and are excellent markers for the large earthquakes that exhumed the scarp.

Following the installation and acceptance test of the French 5 MV AMS facility ASTER, the focus has been on improving the capability for routine measurements of 10Be and 26Al. Quality assurance has been established by the introduction of traceable AMS standards for each nuclide, by self-monitoring through participation in round-robin exercises and proficiency testing, and by surveillance of long- and short-time variability of blank and reference materials. A background level of 3 × 10−14 makes ASTER well-suited for measuring 41Ca/40Ca in the10−12 region, which is sufficient for a wide range of applications. Routine AMS measurements of volatile elements like 36Cl and 129I will most likely become feasible in the very near future as the result of significant improvements in the ion source design.

In contrary to siliceous environments, there is a severe lack of cosmogenic nuclides, that can be used for in situ dating of calcareous environments. Thus, we have investigated other nuclides than 36 Cl as possible dating tools by cross-calibration. Cosmogenic 10 Be is highly contaminated with atmospheric 10 Be and cannot be removed quantitatively, even by a very sophisticated chemical cleaning procedure. Only working on clay-free calcite provides correct 10

All exposed rocks on Earth’s surface experience erosion; the fastest rates are documented in rapidly uplifted monsoonal mountain ranges, and the slowest occur in extreme cold or warm deserts—millennial submeterscale erosion may be approached only in the latter. The oldest previously reported exposure ages are from boulders and clasts of resistant lithologies lying at the surface, and the slowest reported erosion rates are derived from bedrock outcrops or boulders that erode more slowly than their surroundings; thus, these oldest reported ages and slowest erosion rates relate to outstanding features in the landscape, while the surrounding landscape may erode faster and be younger. We present erosion rate and exposure age data from the Paran Plains, a typical environment in the Near East where vast abandoned alluvial surfaces (10 2 –10 4 km 2 ) are covered by well-developed desert pavements. These surfaces may experience erosion rates that are slower than those documented elsewhere on our planet and can retain their original geometry for more than 2 m.y. Major factors that reduce erosion converge in these regions: extreme hyperaridity, tectonic stability, fl at and horizontal surfaces (i.e., no relief), and effective surface armoring by a clast mosaic of highly resistant lithology. The 10 Be concentrations in amalgamated desert pavement chert clasts collected from abandoned alluvial surfaces in the southern Negev, Israel (representing the Sahara-Arabia Deserts), indicate simple exposure ages of 1.5–1.8 Ma or correspond to maximum erosion rates of 0.25–0.3 m m.y. –1 . The 36

International audience; Although the geology and structure of the Zagros fold-and-thrust belt (Iran) have been studied extensively, the distribution of active deformation across the belt and its seismotectonic behaviour remain controversial. We have mapped deformed fluvial terraces along the Dalaki and Mand rivers in the central Zagros, as well as marine terraces along the Persian Gulf, in order to unravel the spatial pattern of vertical displacements and to analyse active deformation and its implications for seismicity. Using appropriate fold models based on structural data allows interpreting such vertical displacements in terms of horizontal shortening across the fold structures. Obtaining well-constrained rates of deformation depends on reliably dating deformed geomorphic markers; by combining different dating techniques and correlations to sea level history, we propose an internally consistent set of ages, which allow the first geomorphic estimates of shortening rates absorbed by individual structures in the central Zagros. Our results show that shortening on Late Pleistocene timescales is concentrated in the frontal part of the belt, consistent with recent GPS data. Three or four frontal structures appear to absorb practically all of the active shortening across the Zagros, broadly consistent with a normal forward-propagating deformation sequence but with local out-of-sequence activation of structures behind the forward-most folds. The localization, rate and direction of surface shortening across individual structures appear decoupled from basement deformation, as indicated by structural cross-sections and the distribution of seismicity. Such independent behaviour suggests that the sedimentary cover of the frontal Zagros is decoupled from the basement, most probably at the level of the Hormuz Salt. This weak basal detachment level, together with several intermediate décollement levels, appears to be responsible for the overwhelmingly aseismic deformation of the Zagros sedimentary cover, and also to control the development of a large panel of fold structures, from detachment to fault-propagation folds with varying wavelength and rooting depth.

The spreading application of accelerator mass spectrometry (AMS) to the geosciences will require measurement of increasing numbers of samples with low 10Be/9Be and 36Cl/Cl isotopic ratios. To distinguish radionuclide concentrations in samples from corresponding processing blanks, samples must be prepared using stable isotope carriers with low intrinsic radionuclide concentrations. Measurements at different AMS facilities have shown that commercially available 9Be carriers rarely meet these requirements and use of 9Be carriers prepared from Be-containing minerals such as Be2SiO4 is advisable. For precise determinations at the low 10−14 level, samples need to produce the highest 9Be currents possible. Measurements performed at the two AMS facilities in France show that mixing BeO with Nb powder generally yields higher 9Be currents than mixing with Ag powder. Contamination of BeO by other elements such as Ti or Al will reduce the current by a simple dilution effect, thus limiting the statistical precision with which 10Be can be determined. In the case of 36Cl analyses, repeated water-leaching of calcite samples sufficiently removes all atmospheric 36Cl contamination, allowing determination of terrestrial cosmogenic in situ produced 36Cl concentrations for surface exposure dating.