The geology of the State of Qatar comprises large spans of carbonate rocks at the surface and evaporitic rocks at shallow depth, and a number karst features (depressions, caves) spread across the country that may cause challenges during land development or infrastructure construction. The government of Qatar has identified that existing geodatabases and geological and hydrogeological maps require improvement to mitigate this risk. In this framework, a thorough assessment of the karst geohazard has been performed including a karst features survey, geologic study of karstification, and an assessment of associated ground subsidence related to karst. The main findings indicate the existence of two types of caves: one corresponding to shallow subsurface dissolution caves developed under phreatic conditions in the past and truncated by erosion at a later stage, the other corresponding to large roof collapse caves originating at depth (intrastratal karst). These latter caves are systematically located on the edge of large depressions. In agreement with the existing literature, it is proposed that the depressions and collapse caves are part of a same collapse/sagging process caused by loss of material at depth (e.g., dissolution of evaporites, compaction of weathered dolostone, or incremental collapse of coalesced relict caves). To extract the karst collapse depressions among the large number of depressions mapped using a recent (2017) LiDAR DTM dataset, it is hypothesized that the karst depressions shall have the same geometrical characteristics (width, length, area, depth) than the few ones containing a roof collapse cave. This results in the identification and mapping of 3537 karst depressions spread across the entire Qatar peninsula. Presently, these karst features seem mostly inactive and thus inherited from a geoclimatic context, which was more favorable to karstification. Under the present geoclimatic conditions, the karst subsidence geohazard appears to be generally low, as caves are inherited, and ongoing karstification processes are limited. However, this geohazard is present across large spans of the territory and any future land development shall include plans and strategies to consider the presence of karstified rocks in the subsurface and ensure that karst is not reactivated by human activity.

Developing accurate 3D geological models of the subsurface is crucial, as they provide the foundations for multiple uses (e.g., resource exploration and exploitation, geohazard assessment, and environmental geoscience). The construction of these models is an intrinsically integrative task, which jointly takes into account all available data and information from multiple sources, i.e. structural geology, stratigraphy, petrophysics, geophysics. Despite the progress made in automating the integration, in particular with recent advances in artificial intelligence, human interpretation remains essential. Consequently, the performance and limitations of human geological interpretation need to be carefully assessed particularly when subsurface data are incomplete, sparse and imprecise. In this context, the French geological survey – BRGM – has set up a blind interpretation exercise that enables the geo-interpreters to test their ability to answer two main operational questions when jointly analyzing geological and multi-source geophysical datasets (seismic, gravimetric, electric/magneto-telluric): (q1) Is it possible to detect and characterize structural traps and potential migration pathways at several kilometers depth? (q2) Do the errors associated with each of the different datasets influence / affect / bias the geological interpretation? If so, how?To this end, the following procedure was applied: (1) a simplified 3D geological model was constructed using a real exploration project dedicated to the characterization of helium reservoirs in a deep Permian sedimentary basin; (2) two cross-sections were extracted from the model with realistic petrophysical properties to constrain geophysical forward models, i.e. gravimetric, magneto-telluric, and seismic; (3) these geophysical "truths" were intentionally degraded to reflect measurement errors and realistic processing. During the 6-hour exercise, the degraded geophysical datasets along with geological data from one borehole and from the 1:1,000,000 scale geological map were provided to three teams of interpreters - each consisting of a geologist and a geophysicist, with the aim of interpreting the two cross-sections.This communication summarizes the main lessons learned from this exercise by discussing the interaction between data resolution, quality and reliability, and cognitive biases. It points out the value of fostering recurrent exchanges with data producers during the geological interpretation process. Finally, we propose recommendations for improving the links between data-centric and human-centric inversion procedures.

The external parts of mountain belts, including their foreland basins, classically present a fold-and-thrust belt often detached on shallow decollement levels. These areas exhibit complex geometries with significant non-cylindrical components, necessitating a 3D approach to accurately determine the timing and style of deformation in the external zones.The southwestern Alpine orogenic front is mainly characterized by the Digne Nappe, which thrusts over the deformed Mesozoic units. These Mesozoic units are unconformably overlain by the Cenozoic molasse deposits of the Valensole foreland basin, which are also deformed.Despite the well-constrained sedimentary series of Barles and many of its structures, no study has yet fully explained the complex 3D geometries and processes that led to their formation. This region serves as an exceptional 3D example of a folded foreland, capturing much of the syn- and post-collisional history of the Alpine orogeny. The structural style, timing, and presence of salt structures remain challenging to specify, largely due to the non-cylindrical geometries that complicate simple 2D reconstruction. The Velodrome fold, formed by the initial deposits of the Valensole foreland basin, exemplifies a non-cylindrical structure whose understanding is still incomplete, leading to debates and various interpretations, including growth fold, post-sedimentary fold, and salt mini-basin.To provide an accurate depiction and interpretation of the 3D geometries of the structures and to better characterize the style and timing of deformation in the Digne region, a combined approach of detailed structural field study and 3D geometric modeling using GeoModeller ©BRGM was undertaken. The 3D modeling was conducted at two scales: (i) regional, encompassing the Digne Nappe, the Robine unit, the Barles half-window, and the Valensole Basin, and (ii) more local, focusing on the Velodrome syncline. For the latter, GeoModeller was utilized to test hypotheses proposed in the literature. This approach enabled the reproduction of field-observed geometries in 3D, offering an interpretation of all formations consistent with surface observations. As a result, the contributions of regional tectonics and salt tectonics were assessed, and the timing of deformation was refined.Elements of the geometry and timing of deformation in this frontal part of the Alps have been clarified. We show that south of the Barles half-window, the deformation of the Velodrome is early syn-depositional, starting earlier in the south of the basin (23 Ma) than in the north (18 Ma), requiring both regional tectonic control and halokinetic processes to account for the closure of the folded structures. The northern part of this half-window shows more cylindrical structures, but some faults appear localized and correlated with thickness variations of the Tithonian unit, indicating a role of inheritance in the localization of deformation. Finally, this study also demonstrated the power of GeoModeller as a 3D tool that is both predictive and useful for testing geological hypotheses in areas as complex as folded forelands.

The Maul & eacute;on basin is a world-class example of hyperextended rift suture. The basin possesses key attributes of an optimal hydrogen target, namely mantle, at shallow depth with tectonic structures rooted into it. Natural H2 seepages have been recognized at the surface in the foothills. Yet distribution and quantification of serpentinization within the mantel piece representing the potential H2 source has not been addressed while this aspect is crucial to consider further exploration. We discuss these aspects using joint gravimetric and magnetic 2D forward modeling along two orthogonal transects. 2D forward modeling shows that serpentinization gradually increases from bottom (20 km depth) to top reaching a maximum amount of nearly 76% (8 km depth). The N-S transect evidence that serpentinization fronts are northward inclined, suggesting a N-S serpentinization gradient responsible for the long wavelength gravity and magnetic anomalies. This orientation matches that of detachment within the former hyperextended domain, which exhumed the mantle during the Cretaceous. The W-E transect shows that serpentinization also increase toward the east reaching its maximum amount against the Barlan & egrave;s lithospheric structure. The latter also coincides with the main short wavelength magnetic anomaly recognized in the basin. Forward geophysical modeling reveals that this anomaly could be linked to the presence, at shallow depth, of an alkaline magmatic body or a shallower piece of highly serpentinized subcontinental mantle both attesting for the paroxysm of the Cretaceous rifting phase. Finally, we propose a conceptual model of the H2 life cycle in the Maul & eacute;on basin and discuss the implications for H2 exploration. We address the distribution of serpentinization in an inverted hyperextended rift system based on joint gravimetric and magnetic modeling The mantle is gradually serpentinized on an overall thickness of around 15 km reaching a maximum amount of nearly 76% The mantle and the basement top are respectively in optimal thermal windows to generate H2 by serpentinization and trap it

Fold geometries and kinematics within foreland basins is a major issue for understanding the late evolution of thrust fronts. In the foreland of the southwestern Alps, the Vélodrome complex fold involves the whole Tertiary series which have recorded the evolution of the alpine front. From a geometrical and kinematic point of view, the Vélodrome is classically described as a recumbent Mio-Pliocene syncline with a strongly curved axis; interpreted either as a classic growth-fold, a post-deposit fold, or a result of coeval salt activity. The debate reveals a lack of consensus on the internal structure of the Vélodrome and the potential role of salt motion. By a detailed field analysis coupled with an implicit 3D geometrical modelling approach, we test the different hypotheses and provide a new 3D illustrated interpretation of the Vélodrome series. The Vélodrome consists in a complex non-cylindrical structure composed by several folds with different orientations together with inter- and intra-formations unconformities. Folding is partly syn-depositional and began earlier in the south, near Esclangon village, than in the north. In the north, deformation started with the marly and sandy molasse (m2, middle Burdigalian), attested by the transition from the conformable conglomeratic marine molasse (m1–2, Aquitanian and early Burdigalian) to the unconformable m2 to the Valensole formation. Deformation began earlier in the south, during the deposition of the m1–2, as shown by internal unconformities. We discuss the ingredients controlling the deformation in the Vélodrome, regional tectonics (mainly since middle Burdigalian) versus salt tectonics. This study further brings new constraints on the timing and pattern of deformation of the southwestern orogenic front of the Alps. It also highlights the power of the 3D geometrical modelling approach for testing different hypotheses and better understanding 3D complex structures.

The 4.9 Mw earthquake of 11 November 2019 at Le Teil (France) occurred at a very shallow depth (about 1 km), inducing the surface rupture of La Rouvière fault. The question was raised shortly after about the potential impact of a nearby surface quarry. Thanks to satellite differential interferometry, here, we revealed the existence of a secondary surface rupture of the quasi-parallel Bayne Rocherenard fault. A newly processed seismic cross-section allowed us to shape the three-dimensional geometry of the local three-fault system. Assuming that the earthquake was triggered by the impact of meteoric water recharge, our numerical simulations show that the hydraulic pressure gradient at depth was at a maximum during the period of 2010–2019, just before the seismic event. The estimated overpressure at the intersection of the two faults, which is the most probable place of the hypocenter, was close to 1 MPa. This hydraulic effect is about two and a half times larger than the cumulative effect of mechanical stress release due to the mass removal from the surface quarry over the two past centuries. This work suggests a rapid hydraulic triggering mechanism on a network of faults at a shallow depth after a heavy rainfall episode.

The Mw 4.9 earthquake of 11 November 2019 at Le Teil (France) occurred at a very shallow depth (about 1 km) inducing the surface rupture of La Rouvière fault, nearby of a limestone quarry. Thanks to satellite differential interferometry, we detected the existence of the secondary surface rupture of the quasi-parallel Bayne Rocherenard fault. A newly processed seismic cross-section allowed us to construct a local 3D fault system. Assuming that the earthquake was triggered by the transient increase in hydraulic pressure following heavy rainfall before the event, our numerical 3D simulations demonstrate that the hydraulic pressure gradient is maximum just before the earthquake at the intersection of the two faults, the most probable place of the hypocenter. This hydraulic effect is about two and a half times larger than the cumulative effect of mechanical stress release due to the mass removal from the surface quarry over the two past centuries.

“The Source-to-Sink Vade Mecum: History, Concepts and Tools” is the latest Open-Access addition to the SEPM series Concepts in Sedimentology and Paleontology. In the form of a carry-along vade-mecum, in English and French, this volume offers a comprehensive history of the source-to-sink approach, tracing its origins from early geomorphological thinkers to its current applications in exploration, quantitative geomorphology and paleoclimate research. The reader will gain a deeper understanding of the major controls of erosion, transfer, and deposition, and how they shape landscapes and the sedimentary record. The book also describes the latest developments on the propagation of environmental signals from source to sink. The book contains all the basic science concepts needed to understand the complex interactions between the Earth's surface and its sedimentary systems. Also designed as a text-book for teaching the subject in academia or industry, each concept is carefully explained with dedicated figures, making it easy to understand for both students and professionals. The “S2S Vade-Mecum” also includes a toolbox of methods currently in use for the source-to-sink approach. This toolbox provides a quick overview of the many methods available for reconstructing ancient sedimentary systems from source to sink, making it an ideal reference for students, researchers and practitioners alike. With contributions from leading experts from academia and industry, this volume is an essential resource for anyone seeking a deeper understanding of sedimentology and sedimentary basin evolution. Whether you are a student, researcher, academic or industry professional, the “S2S Vade-Mecum” is a must-have reference that will undoubtedly enhance your knowledge and skills in this dynamic field.

On 11 November 2019, the Le Teil Mw4.9 earthquake occurred in southeast France, in the vicinity of a surface quarry. We focus this work on the effect of hydraulic recharge linked to the infiltration of meteoric water in the fault zones in the period preceding the earthquake. In the reference simulation, we used the in situ soil moisture at 30 cm depth (Berzème station) as surface boundary conditions.We describe first the local 3D fault system from an updated geological model and the boundary conditions that are used to calculate the pressure variations at depth using a double permeability model.The movement of moisture in partially-saturated media is then simulated by the Compass code (1) during the period 2015-2019. A maximum overpressure takes place near the junction of the three-fault system at around 1,200 m depth. Moreover, the calculated increase in pore fluid pressure is maximum during 2015-2019 just before the earthquake of 11 November 2019. Additionally, the surface soil moisture (SSM) data acquired by the SMOS satellite (2) are used to extend the study period between 2010 and 2015.A sensitivity study carried out on the main hydraulic parameters allows us to estimate that the overpressure linked to the hydraulic recharge of the fault system is between 0.7 and 1 MPa at about 1200 m depth before the seismic event.Finally, we compare this result with the maximum Coulomb stress change linked to the mass withdrawal from the surface quarry over the two past centuries (3). The conclusion is that the hydraulic effect is about two and a half times larger than the cumulative effect of the mechanical stress release due to the mass removal from the surface quarry.(1) https://github.com/BRGM/ComPASS(2) Li, X., Wigneron, J.-P., et al.: The first global soil moisture and vegetation optical depth product retrieved from fused SMOS and SMAP L-band observations, Remote Sensing of Environment 282, 113272, 2022. https://doi.org/10.1016/j.rse.2022.113272(3) Maury, J., Guillon, T., Aochi, H., Bazargan, B., and Burnol, A.: Assessing the effect of mass withdrawal from a surface quarry on the Mw4.9 Le Teil (France) earthquake triggering, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2742, https://doi.org/10.5194/egusphere-egu22-2742, 2022.

<p>Deformation of intraplate sedimentary basins essentially results from tectonic stresses that propagate from plate boundaries. Yet, the detailed characteristics of this far field propagation are often poorly constrained, especially in age. Recent developments of U/Pb dating of calcite precipitations in fault planes and veins hopefully greatly help to frame the schedule of deformation. This is the case for the Meso-Cenozoic Paris basin, liable to have recorded several Cenozoic events due to its location in the western Eurasian plate, like Pyrenean and Alpine collisions and Oligocene extension (ECRIS).</p> <p>Our study focusses on the southern Paris basin area, north of the Morvan massif, where Alpine deformations are expected. Field data reveal almost exclusively strike-slip deformations with variable σ<sub>1</sub> direction. These results are about to be confirmed at the microscopic scale using Anisotropy of Magnetic Susceptibility and of P-Wave Velocity methods. Associated U-Pb dating of synkinematic calcites from Jurassic strata indicates distributed Eocene deformation and an absence of Oligocene or Miocene ages. Such ages suggest the record of Pyrenean and possibly ECRIS tectonic events. Strikingly, Alpine deformation and especially stress propagation leading to the growth of the Jura fold-and-thrust belt during Miocene does not imprint the studied area although the Alpine orogen is located closer than the Pyrenean belt.</p>

Recently, the understanding of the role of salt dynamics in the evolution of fold-and-thrust belts and foreland basins has significantly improved with the development of high-resolution seismics. Understanding a salt-related structure in the field as a mini-basin requires a thorough understanding of the 3-D geometries of folds. In the western subalpine chain of Haute Provence, the Digne thrust area has undergone a complex tectonic history involving syn-sedimentary deformation, the migration of alpine front, late exhumation related to surface processes, and salt tectonics. In the front of the Digne thrust, the Vélodrome is an emblematic example of a complex fold displaying a 3D structure hardly explained by regional tectonics. The Vélodrome is an overturned syncline displaying a curved axis which direction changes from E-W in the north to N-S in the east and to E-W again in the south-eastern part. The Vélodrome is often interpreted as a growth fold with internal unconformities, but microstructural analyses (Fournier et al., 2008) have alternatively suggested a post-deposition folding. Moreover, recent studies (Graham et al., 2012; Celini, 2020) propose that the fold formed due to salt tectonics and interpret the Vélodrome as a mini-basin. Thus, the Vélodrome complex tectonic structure requires a thorough understanding of the 3-D geometries to understand its tectonostratigraphic evolution. This study aims at understanding the emplacement and the tectonic history of the Miocene Vélodrome series using in-situ field observations and drone field data to realize a 3-D geometrical model (GeoModeller - ©BRGM). More than 3000 structural data have been measured - both directly in the field and on 3D models obtained from drone image processing - and used in the GeoModeller to test the different hypotheses. The implicit approach offered by the GeoModeller and the field structural data-based approach bring an objective and new vision of 3-D geometries of the Vélodrome basin and confirm the Vélodrome as a syn-sedimentary fold. This study highlights several discontinuities inter- and intra-formations spatially localized. In the north of the Vélodrome, Aquitanian deposits do not present any unconformity, whereas internal unconformities can be observed in Burdigalian deposits. In the southeast of the fold, we observed internal unconformities both in the Aquitanian and Burdigalian deposits. This leads us to propose an early salt-related episode of deformation in the southeast part of the fold (Aquitanian) compared to the north, where deformation began only during the Burdigalian.

The origin of the Eocene-Oligocene European Cenozoic Rift System (ECRIS) is debated in terms of driving forces, far-field or near field, Alpine slab-pull or active plume. An analysis of residual (non-isostatic) topography over Africa and Europe reveals domains elongated parallel to the absolute motion of plates in a hot-spot reference frame. The East African Rift (EAR) and the ECRIS sit on top of such positive anomalies. A recent whole mantle tomographic model (French et al., 2013; French & Romanowicz, 2015; Davaille & Romanowicz, 2020) shows in addition that the low shear-wave velocity zones of the lower and upper mantle are organized with a bundle of vertical plumes and horizontal fingers pointing in the same direction parallel to the absolute motion of Africa and Eurasia, thus parallel to the main rifts. The case of the EAR and its magmatic extension toward the north across the Arabian Plate is particularly clear with several levels of such fingers. The northward migration of the first volcanism from Ethiopia to Armenia between the Eocene and the Late Miocene suggests that the asthenosphere moves faster than the plates and thus drives plate motion (Faccenna et al., 2013). We propose a simple model where plates are driven by basal drag, following an upwelling from the low-velocity anomalies below Africa and toward subduction zones. The EAR develops as lithospheric weak zones on top of the positive anomalies of residual topography due to the underlying low velocity anomalies elongated parallel to the absolute motion. This indicates an interplay between large-scale convection, a small-scale fingering instability, and lithospheric deformation. The development of the Eocene-Oligocene short-lived ECRIS and its interference with Mediterranean slab dynamics are then discussed in the framework of this simple model.

The Pyrenean domain records the development of a hyperextended system during the Early Cretaceous at Iberia/Eurasia plate-boundary. This rifting stage is controlled by the coeval development of N120° longitudinal and N20° transverse tectonic features. In the west-Pyrenean Mauléon basin, preserved in the heart of a N120° lithospheric pop-up, the Iholdy, Saison and Barlanès transverse structures are known to play a significant role during the Cretaceous hyperextension. Using a multidisciplinary approach combining Raman thermometry, paleostress reconstructions, seismic interpretations, 3D implicit geological modeling and passive seismic interpretation, we define these three N20° structures as syn-collisional transfer zones rooting at depth in the upper lithospheric mantle. These tectonic features significantly control the 3D structural architecture of the Mauléon basin pop-up. Indeed, the N120°-oriented thrust systems, defining the edges of the Mauléon basin pop-up, branch into these transfer zones and define corridors with differing amounts of shortening. This overall structural pattern defines drawer-like structures allowing the closure, by stages, of the former rift domain. Thus, this study clarifies the role of inherited lithospheric transfer zones in the reactivation of a hyperextended rift basin and bears upon the origin of the non-cylindrical shape of the West-Pyrenean belt.

The Mauléon Basin, in the northwestern Pyrenean Belt, is related to Early Cretaceous rifting and mantle denudation. Here we review the evolution of depositional systems in the Mauléon Rift Basin during Albian and Cenomanian time. This review includes the lithostratigraphy, regional distribution, boundaries, age and facies sedimentology of the basin’s syn-rift formations and their members. We construct paleogeographic maps to elucidate (1) the 3D distribution of sedimentary facies and depositional systems during the Albian and Cenomanian from the Iberian proximal margin to the hyperextended domain and (2) the link between major extensional structures and sedimentation during rifting and mantle denudation. The Mauléon Rift was supplied during most of the Albian by sediments from the Iberian proximal margin. The southern margin had a steep and abrupt topographic boundary related to a northward crustal rollover along the south-dipping Saint-Palais detachment. This feature controlled the deposition of coarse-grained turbidites at the base of the margin that abruptly gave way to low-density turbidites, then deep-basin deposits in the hyperextended domain. During uppermost Albian to Early Cenomanian time, mantle denudation occurred in the eastern Mauléon Basin and the vergence of the detachment systems reversed. Minor debris-flow deposits formed at the foot of fault scarps associated with the newly formed north-dipping detachments. Elsewhere, sediment from deltaic systems to the west in the Saint-Jean-de-Luz area deposited low-density turbidites in the hyperextended domain. During the post-rift stage, the flux of coarse sediment from the detachment footwall gradually declined as deformation waned, and low-density turbidites expanded onto the hyperextended domain from the European Upper Cretaceous carbonate platform. These paleogeographic reconstructions, in addition to offering a synthetic view of the evolution of sedimentary environments during rifting, offer new insight into the post-rifting exhumation of the lower crust and mantle.

This chapter presents an overview of the main interpolation methods available in geomodeling software. Different interpolation methods are employed by a wide variety of modeling software products. The chapter provides an overview of the SKUA GOCAD system, and demonstrates how GOCAD tools and procedures may be applied to modeling shallow discontinuous Quaternary stratigraphic units using explicit methods with added stratigraphic rules and constraints. GOCAD was developed to model, manage, and visualize complexly deformed geological surfaces. The development of SKUA-GOCAD has been mostly focused on solving specific problems related to modeling deformed sedimentary basins and their physical properties. The chapter provides an overview of the Geological Data Management Software Suite and GeoModeller, both developed by the Bureau de Recherches Géologiques et Miniéres (BRGM). In the 1990s, BRGMdeveloped the “Editeur Géologique” to support its geological mapping/modeling activities. The GeoModeller process of 3-D model creation and validation involves several steps, beginning with the collection of multiple data sources.

In the front of the Digne thrust, the deformed foreland basin, the well exposed tectonic window of Barles, is still not well understood. This region has undergone a complex tectonic history involving synsedimentary deformation, potential migration of alpine front, late exhumation related to surface processes and potential salt tectonics. Although the stratigraphy and the structural geology of the area is well known, the respective contributions of regional tectonics, salt tectonic and surface processes remain uncertain. The region displays still enigmatic objects emplaced at each step, from the rifting phase to the late exhumation, such as the overturned Liassic Barre de Chine or the overturned Miocene syncline of the Vélodrome. This study aims at understanding the evolution of the foreland Valensole basin from the deposition of first sediments 30Ma ago to late exhumation and relief formation. We focused our work on the emblematic Vélodrome syncline which is also the only place where a continuous sequence of the basin deposits is exposed. The molassic and conglomeratic layers of the Vélodrome form an overturned syncline with a curved axis of which direction changes from EW in the north to NS in the most south-eastern part. The Vélodrome has been studied for more than a century but its history is still debated. If the Vélodrome is often interpreted as a growth fold which explain the observation of progressive unconformities, microstructural analyses (Fournier et al., 2008) suggest that folding postdates sedimentation. Moreover, recent studies (Graham et al., 2012) propose that this spectacular fold formed as a result of salt tectonic. The obliquity of the regional shortening direction regarding the axis direction, the 3-D pattern of the overturned Miocene series and the origin of the progressive unconformities are issues still not resolved. Such a complex tectonic structure as the Vélodrome fold requires a thorough understanding of the 3-D geometries and their evolution through time. Based on field observations and 3-D geometrical modelling (GeoModeller - ©BRGM), we propose a preliminary model of the Vélodrome that brings new insights on this part of the Valensole basin. The implicit approach that offer the GeoModeller and the field structural data-based approach (here more than 2000 structural data) bring an objective and new vision of the geometries in 3-D of the Vélodrome basin and provide arguments to determine the contribution of each geological processes in the tectonostratigraphic evolution of the north margin of the Valensole basin and subsequent shortening at the western subalpine front.