Structure and evolution of the Gulf of Lions: The Sardinia seismic experiment and the GOLD (Gulf of Lions Drilling) project

International audienceThe study of the deep structure and evolution of passive continental margins is important for the understanding of rifting processes and the formation of associated sedimentary basins. Since the classical models of McKenzie (1978) and Wernicke (1985), understanding how passive continental margins form, that is to say mainly the way that continental lithosphere is thinned leading to subsidence, remains one of the main challenges in the Earth sciences. Many recent observations and discoveries have modified our basic views of margin formation. The conservational models paradigm (i.e., simple shear, pure shear, or polyphase models), which exclude exchanges between lower continental crust and upper mantle and which are usually proposed to explain lithospheric stretching and consequent crustal thinning of passive continental margins, fail to completely explain all these observations. Furthermore, these models imply a large amount of horizontal movement, movements not observed in the field. In consequence, new concepts need to be built and tested

Investigation of culturable antibiotic resistant bacterial communities in a Mediterranean karstic hydrosystem.

International audienceWaters play a crucial role in interconnecting different ecosystems like humans, animals, soils and hydrosystems, contributing to the circulation of antibiotic-resistant bacteria. Karstic hydrosystems are commonly known to be vulnerable to anthropogenic contaminations due to direct connections between surface water and groundwater and to be heterogeneous due to the contrast between waters stored in some compartments (with long residence time) and waters with fast transit. Considered as integrator ecosystems, natural waters are of great interest to survey the antibiotic resistance in the environment, which is relevant to human health. Among natural hydrosystems, karstic aquifers are poorly investigated for emergence and dissemination of antibioresistance. The question of their role as reservoir for antimicrobial resistance according their hydrogeological characteristics remains open.The Lez karst hydrosystem supplies drinking water to the metropolitan region of Montpellier, in southern France. The aim of this study is to evaluate the resistance level and the biodiversity of bacterial communities in the Lez aquifers in contrasted hydrogeological conditions and seasonality. For this purpose, we develop an original mixed method associating i) selective culture, using culture media containing tetracycline,vancomycin, ofloxacin, amoxicillin, cefotaxime or ceftazidime at increasing concentrations, and ii) molecular approaches, implementing 16S rRNA gene PCR-Temporal Temperature Gradient Gel Electrophoresis (TTGE) and sequencing. Minimal antibiotic concentrations inhibiting 50%, 70% and 90% of the whole culturable community were determined. Resistance to beta-lactams were clearly fluctuant between both compartments and periods of sampling, whereas differences obtained with the others antibiotics were not so marked. Then, the taxonomic diversity and the dynamics of the resistant sub-communities were described.These results show that hydrogeological conditions and thus the speed of water circulation in the karst aquifer can impact the resistance of bacterial communities. Then, the potential risk of bacterial resistance will be discussed in term of resistance transferability and relevance in clinical epidemiology

Coupling stratigraphic and petroleum system modeling tools in complex tectonic domains: case study in the North Algerian Offshore

International audienceIn the eastern Algerian offshore basin, 3D basinmodeling applied for facies prediction and petroleumpotentialassessment shows that most favorable zones for reservoir developmentand hydrocarbon occurrence are located at a maximumdistance of 60 km from the coastline. The lack of welldata in this area is partly compensated by a large data set ofgeophysical and geological (G&G) data such as multichannelseismic (MCS), magnetism, wide angle velocity models, andgeological outcrops; they represent important constraints for3D dynamic modeling. Facies distribution model isconstrained by sequence and environment evolution throughtime that is defined from onshore outcrops. 2D structural reconstitutionand thermal modeling were also undertaken withArcTem software. The structural interpretations highlight theoccurrence of north-verging ramps during the Quaternarywhich played an important role in HC generation and migration.Three source rocks have been considered for maturationmodeling with Temis Flow software, Burdigalian, Langhian,and Tortonian. They are found to be in gas window in the deepareas and locally in oil window at shallower structured zones.The modeling results indicate that the main fluid dischargewas focused toward the southern border of the offshore basinwhere recent thrust faults (parallel to the margin) are located.In order to test the role of these faults in terms of hydrocarbonmigration and trapping, two scenarios are considered accordingto whether they were sealed or not. In both cases, the 2D/3D simulations depict overpressures (2,000–4,000 psi) in thepre-salt sedimentary package. However, the hydrocarboncharge is most efficient with the sealing faults for the lowerLanghian and lower Messinian reservoirs. The hydrocarbonpotential depends mostly on the lateral extension of seals, theirsealing capacity and the organic carbon (TOC) content ofpotential source rocks. Besides, the sea drop of about 1,000 m during theMessinian salinity crisis has induced depressurizationthat caused oil and gas seepage from Miocenereservoirs

Tectonostratigraphic evolution of the eastern Algerian margin and basin from seismic data and onshore-offshore correlation

International audienceThe eastern Algerian basin, part of theWestern Mediterranean domain, is a back-arc basin resulting fromthe SE drift of the Lesser Kabylia block gave rise to continental extension and birth of a new oceanicdomain. We aim here to define the structure and tectonostratigraphic evolution of this basin and theadjoining continental margin. Indeed, the absence of wells and the lack of published MCS data kept thisarea mostly unknown. The crustal architecture (down to the Moho) and seismo-stratigraphy of thesedimentary infill are detailed, emphasizing particularly the pre-Messinian series, by combining a newset of offshore deep penetrating seismic, conventional MCS sections, and wide angle seismic data.Because no well exist offshore we realized new field descriptions of the Late Oligocene and Miocenedeposits on land and propose onshore-offshore extrapolation and age correlations. The pre-Messinianseries display four main units (PMSU1 to 4) above which Messinian units are consistent with stratigraphicmodels already proposed for the Mediterranean basin, the deep basin displays units as old as theOMK (“Oligo-Miocene Kabyle”) series on land. The basement is shaped by conjugate transcurrent faultsstriking N120- N40, forming a series of rhombic troughs resulting from transtensional tectonics. Thecoeval E-W extension and NW-SE stretching of the continental crust suggest a radial opening of theAlgerian basin during Late Oligocene- Lower Miocene, followed by a progressive uplift of the uppermargin after the collision of Lesser Kabylia with Africa. Besides, steep slope of the eastern Algerianmargin, downward flexure of the oceanic basin near the margin toe and growth of S-dipping thrustswithin the margin evidence a significant Quaternary stress inversion. Overall, this study highlights thecomplex stress evolution of the East Algerian margin since Oligocene times, as evidenced by significantupward/downward vertical motions and crustal extensional/compressional successions. We summarizethis evolution into three main stages: (1) rifting (including sea-floor spreading) at Late Oligocene-Burdigalian in the context of back-arc, (2) collision between AlKaPeCa blocks and Africa at 17 Ma, andpost-rift sag basin infill, till Late Tortonian to Messinian, and (3) inversion of the margin and developmentof flexural basins at Quaternary times

Probing connections between deep earth and surface processes in a land-locked ocean basin transformed into a giant saline basin: the Mediterranean GOLD project

During the last decade, the interaction of deep processes in the lithosphere and mantle with surface processes (erosion, climate, sea-level, subsidence, glacio-isostatic readjustment) has been the subject of heated discussion. The use of a multidisciplinary approach linking geology, geophysics, geodesy, modelling, and geotechnology has led to the awareness of coupled deep and surface processes. Deep earth dynamics (topography, erosion, tectonics) are strongly connected to natural hazards such as earthquakes, landslides, and tsunamis; sedimentary mass transfers have important consequences on isostatic movements and on georesources, geothermal energy repartitions. The ability to read and understand the link between deep Earth dynamics and surface processes has therefore important societal impacts. Ground-truthing at carefully-selected sites of investigation are imperative to better understand these connections. Due to its youth (<30 Ma) and its subsidence history, the almost land-locked Gulf of Lion-Sardinia continental margins system provides a unique record of sedimentary deposition from the Miocene to present. Due to its high subsidence rate, palaeoclimatic variations, tectonic events and vertical evolution are all recorded here at very high resolution. The late Miocene isolation and desiccation of the Mediterranean, the youngest and most catastrophic event, the Messinian Salinity Crisis (MSC), induced drastic changes in marine environments: widespread deposition of evaporite (gypsum, anhydrite and halite) in the central basin, and intense subaerial erosion along its periphery. These extraordinary mass transfers from land to sea induced strong isostatic re-adjustments that are archived in the sedimentary record and represent a window to the lithospheric rheology and the deep processes. The GOLD (Gulf of Lion Drilling) project, proposes to explore this unique sedimentary record as well as the nature of the deep crustal structure, providing valuable information about the mechanisms underlying vertical motions in basins and their margins

The revised Approved Instructional Resources score:An improved quality evaluation tool for online educational resources

BACKGROUND: Free Open-Access Medical education (FOAM) use among residents continues to rise. However, it often lacks quality assurance processes and residents receive little guidance on quality assessment. The Academic Life in Emergency Medicine Approved Instructional Resources tool (AAT) was created for FOAM appraisal by and for expert educators and has demonstrated validity in this context. It has yet to be evaluated in other populations.OBJECTIVES: We assessed the AAT's usability in a diverse population of practicing emergency medicine (EM) physicians, residents, and medical students; solicited feedback; and developed a revised tool.METHODS: As part of the Medical Education Translational Resources: Impact and Quality (METRIQ) study, we recruited medical students, EM residents, and EM attendings to evaluate five FOAM posts with the AAT and provide quantitative and qualitative feedback via an online survey. Two independent analysts performed a qualitative thematic analysis with discrepancies resolved through discussion and negotiated consensus. This analysis informed development of an initial revised AAT, which was then further refined after pilot testing among the author group. The final tool was reassessed for reliability.RESULTS: Of 330 recruited international participants, 309 completed all ratings. The Best Evidence in Emergency Medicine (BEEM) score was the component most frequently reported as difficult to use. Several themes emerged from the qualitative analysis: for ease of use-understandable, logically structured, concise, and aligned with educational value. Limitations include deviation from questionnaire best practices, validity concerns, and challenges assessing evidence-based medicine. Themes supporting its use include evaluative utility and usability. The author group pilot tested the initial revised AAT, revealing a total score average measure intraclass correlation coefficient (ICC) of moderate reliability (ICC = 0.68, 95% confidence interval [CI] = 0 to 0.962). The final AAT's average measure ICC was 0.88 (95% CI = 0.77 to 0.95).CONCLUSIONS: We developed the final revised AAT from usability feedback. The new score has significantly increased usability, but will need to be reassessed for reliability in a broad population.</p