Morphostructure of the Egyptian Continental Margin: Insights from Swath Bathymetry Surveys

In the Eastern Mediterranean, offshore Egypt, the Nile continental margin is characterized by a large deep water turbiditic system known as the Nile Deep Sea Fan. This post-Miocene terrigenous construction covers an approximately 10 km-thick sedimentary pile, including 1–3 km of Messinian salt layers. Systematically collected swath bathymetric data proved to be the most powerful tool to discover, describe and study many sea floor features of this sedimentary construction which reflects competition between active tectonic, sedimentary, and geochemical processes. Gravity tectonics, triggered by underlying mobile salt layers, construction of channel-levee systems, the passage of turbidite flows, sedimentary slope failures at various scales, massive mud expulsions and fluid seepages are all interfering to shape the Nile Deep Sea Fan seabed.     

Trophic ecology of the rocky shore community associated with the Ascophyllum nodosum zone (Roscoff,France): A δC vs δN investigation

This study aimed to characterize the structure and functioning of the benthic food web associated with the Ascophyllum nodosum zone of the rocky shore of Roscoff by using δ¹³C and δ¹⁵N. Several characteristics of the trophic ecology of the invertebrates associated with this mid-littoral habitat and which belong to different functional groups (e.g., grazers, filter-feeders, predators and omnivores) were highlighted. In particular, the filter feeder species (including mostly sponges) used macroalgae-derived organic matter as a substantial food requirement. The results also pointed out an important stable isotopes variability for strict coexisting primary consumers which: (1) is directly related to the high δ¹⁵N range of the food sources; (2) makes it impossible to establish a unique trophic level scale based on δ¹⁵N values, as previously done in coastal environments; and (3) points out the existence of major co-occurring trophic pathways which characterise the Ascophyllum nodosum habitat.     

Marine spatial planning in the high seas

Although high seas resources are being exploited, reciprocal legal obligations to protect its environment have not been met. Marine spatial planning (MSP) is clearly a practical way forward, particularly for the high seas, where non-spatial monitoring is difficult, and where data gaps obstruct conventional management approaches. To ensure the effective application of MSP in the high seas, however, some institutional reforms are necessary. This paper outlines the main hurdles, summarizes existing high seas spatial protections, presents an example of a high seas marine protected area that resulted through MSP, identifies three institutional priorities, and suggests three immediate steps.     

Trophic coupling between two adjacent benthic food webs within a man-made intertidal area: A stable isotopes evidence

This study aimed at establishing the effects of human-made physical modifications on the trophic structure and functioning of an intertidal benthic food web in Arcachon Bay (France). The main food sources and the most representative consumers were sampled on an artificial rocky dyke and its adjacent seagrass meadow. The food sources of consumers were inferred through the use of carbon and nitrogen stable isotopes. The contributions of the different food sources to the diets of the consumers were established using the Isosource mixing model. In order to reduce the range of feasible contributions, additional non-isotopic constraints were added when necessary to the outputs of this model.     

The late Messinian event: A worldwide tectonic revolution

A review of geological and geophysical observations points towards a worldwide kinematic change at around 6 Ma. The synchronicity of many manifestations (tectonics, magmatism, kinematics, ecological events, among others) at ~6 Ma, similar to those recognized from time to time on the geological time‐scale, argues for a global geodynamic event that has led to many regional consequences on Earth's surface. In particular, we propose that this global event was the main trigger for the three fold increase in sediment deposits in the world ocean over the last ~5 Ma, but also for the onset of the Messinian Salinity Crisis in the Mediterranean area, one of the most severe ecological crises in the Earth's history. We suggest this Messinian revolution to be the last occurrence of cyclic successions of global events.     

Early Cretaceous (late Berriasian to early Aptian) palaeoceanographic change along the northwestern Tethyan margin (Vocontian Trough,southeastern France): δ13C, δ18O and Sr-isotope belemnite and whole-rock records

Stable carbon, oxygen, and strontium isotope records were obtained from uppermost Hauterivian to lowermost Aptian belemnite rostra, which were collected in well-dated sections from the Vocontian Trough (southeastern France). This data set complements previously published belemnite-isotope records from the uppermost Berriasian-Hauterivian interval from the same basin. The belemnite carbon and oxygen isotope record is compared to the carbonate bulk-rock isotope record from the same sections, and from additional Italian sections. With regards to their long-term trends, both belemnite and whole-rock δ¹⁸O records are well correlated, except for the uppermost Hauterivian-lower Barremian interval, within which they deviate. This discrepancy is interpreted to be linked to the latest Hauterivian Faraoni oceanic anoxic event and its early Barremian aftermath. The Faraoni level is characterized by enhanced sea-water stratification, probably induced by the onset of a warmer and more humid climate along the northern Tethyan margin. The early Barremian was characterized by stronger vertical sea-water mixing reflected by a decrease in density contrast between sea-surface and deeper waters. The belemnite oxygen isotope record shows a more stable evolution with smaller fluctuations than its bulk-rock counterpart, which indicates that deeper water masses were not as much subjected to density fluctuations as sea-surface water. The comparison of belemnite and bulk-rock carbon isotope records allows observing the impact of regional influence exerted by platform carbonate ooze shedding on the carbon cycle. Discrepancies in the two records are observed during time of photozoan carbonate platform growth. The strontium isotopic record shows a gradual increase from the uppermost Berriasian to the uppermost lower Barremian followed by a rapid decrease until the uppermost Barremian and a renewed small increase within the lowermost Aptian. The major inflection point in the uppermost lower Barremian appears to predate the onset in the formation of the Ontong-Java volcanic plateau.     

Impact of the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model

The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m² which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m² when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged.     

Nickeliferous pyrite tracks pervasive hydrothermal alteration in Martian regolith breccia: A study in NWA 7533

Martian regolith breccia NWA 7533 (and the seven paired samples) is unique among Martian meteorites in showing accessory pyrite (up to 1% by weight). Pyrite is a late mineral, crystallized after the final assembly of the breccia. It is present in all of the lithologies, i.e., the fine‐grained matrix (ICM), clast‐laden impact melt rocks (CLIMR), melt spherules, microbasalts, lithic clasts, and mineral clasts, all lacking magmatic sulfides due to degassing. Pyrite crystals show combinations of cubes, truncated cubes, and octahedra. Polycrystalline clusters can reach 200 μm in maximum dimensions. Regardless of their shape, pyrite crystals display evidence of very weak shock metamorphism such as planar features, fracture networks, and disruption into subgrains. The late fracture systems acted as preferential pathways for partial replacement of pyrite by iron oxyhydroxides interpreted as resulting from hot desert terrestrial alteration. The distribution and shape of pyrite crystals argue for growth at moderate to low growth rate from just‐saturated near neutral (6 < pH<10), H₂S‐HS‐rich fluids at minimum log fO₂ of >FMQ + 2 log units. It is inferred from the maximum Ni contents (4.5 wt%) that pyrite started crystallizing at 400–500 °C, during or shortly after a short‐duration, relatively low temperature, thermal event that lithified and sintered the regolith breccias, 1.4 Ga ago as deduced from disturbance in several isotope systematics.     

Freshwater seepages and ephemeral macroalgae proliferation in an intertidal bay: I Effect on benthic community structure and food web

Freshwater seepages and ephemeral Enteromorpha spp. proliferation create heterogeneity at small spatial scale in intertidal sediment. Macrobenthic community diversity was compared between these two disturbances and their respective control points throughout the year 2007 at the Roscoff Aber Bay (Western English Channel, France). In March and September 2007, trophic community pathways of characteristic species were additionally studied using stable isotope ratios of carbon and nitrogen. The low salinity recorded at the freshwater seepage induced the exclusion of the main bioturbator and the presence of omnivores which modified the community composition by biotic pressure. Moreover, food web analyses clearly highlighted a separation at small spatial scale between the two trophic pathways of the impacted area and its control. On the contrary, little differences were observed owning to the ephemeral Enteromorpha spp. proliferation. This suggested a progressive and diffusive disturbance which was applied from the algal mat to the nearby area. However, seasonal changes were observed. First, the algal expansion phase increased the macrofauna diversity and foraminifers’ abundance (meiofauna) and then acted as a physical barrier decreasing sediment and water column exchanges and decreasing the fauna diversity. This study highlights the need to take into account small spatial heterogeneity to avoid misinterpretations in intertidal ecology studies.     

Microstructural defects in experimentally shocked diopside: A TEM characterization

Transmission electron microscopy was used for characterizing the defect microstructure induced by shock experiments in a single crystal of diopside. The shock-induced defects found in the crystal can be divided in four distinct types:

1. A high density and pervasive distribution of dislocations in glide configuration (glide systems (100)[0
2. Mechanical twin lamellae, mostly parallel to (100), the (001) twin lamellae are less abundant. li]3)
3. Heterogeneously distributed tiny molten zones (3 to 20 μm size) which, after cooling, appear as a glass with a chemical composition very close to the one of the original diopside.

The present TEM study reveals that the defect micro-structure in shocked diopside consists of a large variety of shock-induced defects. Especially, the amorphous PDFs which were never observed in statically deformed diopside seem to be an important characteristic micro-structural defects in shocked silicate minerals. Although the presence of amorphous PDFs is not yet confirmed for naturally shocked clinopyroxene, we strongly suggest that these features can serve as a diagnostic tool for recognizing impact phenomena on all planetary bodies of our solar system.