Susceptibility, conductivity and porosity along a GEM-SHARK profile

The coastal systems, are often subjected to high anthropogenic pressure, which makes it necessary to develop new techniques to assess the environmental impacts caused by such human activity. This paper presents the first results obtained during the development and implementation of a new equipment of submarine geophysics survey oriented to integrated coastal zone management (ICZM). It is based on the drag of a submarine in contact with the sea-bottom. The submarine is equipped with an electromagnetic sensor which allows the measurement of the magnetic susceptibility and electrical conductivity of the surface sediments continuously and to a depth of sediment of 40 cm. This system, once improved, will allow us to obtain valuable information for monitoring the environmental quality of coastal areas.

Dive depth and dive duration data of subadult and adult, male and female southern elephant seals from Marion Island between 2004 and 2008 with links to datasets

Although numerous studies have addressed the migration and dive behaviour of southern elephant seals (Mirounga leonina), questions remain about their habitat use in the marine environment. We report on the vertical use of the water column in the species and the potential lifetime implications for southern elephant seals from Marion Island. Long-term mark-resight data were used to complement vertical habitat use for 35 known individuals tagged with satellite-relay data loggers, resulting in cumulative depth use extrapolated for each individual over its estimated lifespan. Seals spent on average 77.59% of their lives diving at sea, 7.06% at the sea surface, and 15.35% hauled out on land. Some segregation was observed in maximum dive depths and depth use between male and female animals-males evidently being physiologically more capable of exploiting increased depths. Females and males spent 86.98 and 80.89% of their lives at sea, respectively. While at sea, all animals spent more time between 300 and 400 m depth, than any other depth category. Males and females spent comparable percentages of their lifetimes below 100 m depth (males: 65.54%; females: 68.92%), though males spent 8.98% of their lives at depths in excess of 700 m, compared to females' 1.84% at such depths. Adult males often performed benthic dives in excess of 2,000 m, including the deepest known recorded dive of any air-breathing vertebrate (>2,133 m). Our results provide a close approximation of vertical habitat use by southern elephant seals, extrapolated over their lifespans, and we discuss some physiological and developmental implications of their variable depth use.

Mineralogy and stable oxygen isotope ratios of the Cretaceous-Tertiary boundary

Results of detailed mineralogical, chemical, and oxygen isotope analyses of the clay minerals and zeolites from two Cretaceous-Tertiary (K/T) boundary regions, Stevns Klint, Denmark, and Deep Sea Drilling Project (DSDP) Hole 465A in the north central Pacific Ocean, are presented. In the central part of the Stevns Klint K/T boundary layer, the only clay mineral detected by x-ray diffraction is a pure smectite with > 95 percent expandable layers. No detrital clay minerals or quartz were observed in the clay size fraction in these beds, whereas the clay minerals above and below the boundary layer are illite and mixed-layer smectite-illite of detrital origin as well as quartz. The mineralogical purity of the clay fraction, the presence of smectite only at the boundary, and the d18O value of the smectite (27.2 ± 0.2 per mil) suggest that it formed in situ by alteration of glass. Formation from impact rather than from volcanic glass is supported by its major element chemistry. The high content of iridium and other siderophile elements is not due to the cessation of calcium carbonate deposition and resulting slow sedimentation rates. At DSDP Hole 465A, the principal clay mineral in the boundary zone (80 to 143 centimeters) is a mixed-layer smectite-illite with >=90 percent expandable layers, accompanied by some detrital quartz and small amounts of a euhedral authigenic zeolite (clinoptilolite). The mixed-layer smectite-illite from the interval 118 to 120 centimeters in the zone of high iridium abundance has a very low rare earth element content; the negative cerium anomaly indicates formation in the marine environment. This conclusion is corroborated by the d18O value of this clay mineral (27.1 ± 0.2 per mil). Thus, this mixed-layer smectite-illite formed possibly from the same glass as the K/T boundary smectite at Stevns Klint, Denmark.

Mineralogical and isotopic compositions of ODP Hole 107-650A

Red-brown dolomitic claystones overlay the Marsili Basin basaltic basement at ODP Site 650. Sequential leaching experiments reveal that most of the elements considered to have a hydrothermal or hydrogenous origin in a marine environment, such as Fe, Cu, Zn, Pb, Co, Ni, are present mainly in the aluminosilicate fraction of the dolomitic claystones. Their vertical distribution, content and partitioning chemistry of trace elements, and REE patterns suggest enhanced terrigenous input during dolomite formation, but no significant hydrothermal influence from the underlying basaltic basement. Positive correlations in the C and O isotopes in the dolomites reflect complex conditions during the dolomitization. The stable isotopes can be controlled in part by temperature variations during the dolomitization. Majority of the samples, however, form a trend that is steeper than expected for only temperature control on the C and O isotopes. The latter indicates possible isotopic heterogeneity in the proto-carbonate that can be related to arid climatic conditions during the formation of the basal dolomitic claystones. In addition, the dolostones stable isotopic characteristics can be influenced by diagenetic release of heavier delta18O from clay dehydration and/or alteration of siliciclastic material. Strontium and Pb isotopic data reveal that the non-carbonate fraction, the "dye" of the dolomitic claystones, is controlled by Saharan dust (75%-80%) and by material with isotopic characteristics similar to the Aeolian Arc volcanoes (20%-25%). The non-carbonate fraction of the calcareous ooze overlying the dolomitic claystones has a Sr and Pb isotopic composition identical to that of the dolomitic claystones, indicating that no change in the input sources to the sedimentary basin occurred during and after the dolomitization event. Combination of climato-tectonic factors most probably resulted in suitable conditions for dolomitization in the Marsili and the nearby Vavilov Basins. The basal dolomitic claystone sequence was formed at the initiation of the opening of the Marsili Basin (~2 Ma), which coincided with the consecutive glacial stage. The glaciation caused arid climate and enhanced evaporation that possibly contributed to the stable isotope variations in the proto-carbonate. The conductive cooling of the young lithosphere produced high heat flow in the region, causing low-temperature passive convection of pore waters in the basal calcareous sediment. We suggest that this pumping process was the major dolomitization mechanism since it is capable of driving large volumes of seawater (the source of Mg2+) through the sediment. The red-brown hue of the dolomitic claystones is terrigenous contribution of the glacially induced high eolian influx and was not hydrothermally derived from the underlying basaltic basement. The detailed geochemical investigation of the basal dolomitic sequence indicates that the dolomitization was most probably related to complex tectono-climatic conditions set by the initial opening stages of the Marsili Basin and glaciation.

Composition of Carnian to Norian sandstones from the Wombat Plateau (Table 1)

The Carnian to Norian sediments, as much as 600 m in total thickness, recovered from ODP Sites 759 and 760 on the Wombat Plateau, are generally represented by fluvial-dominated deltaic successions. In general, the Carnian to Norian sandstones are quartzose. The average ratio of monocrystalline quartz grains, total feldspar grains, and total lithic fragments (i.e., Qm:F:Lt ratio) is 71:22:7. This indicates that they were derived mainly from the transitional continental and cratonic interior provenance terranes, such as the Pilbara Precambrian block to the south of the Wombat Plateau. The upper Carnian sediments, however, are characterized by more feldspathic sandstone petrofacies. They typically contain some volcanic rock fragments with trachytic texture and indicate the onset of the incipient rift-related tectonic movement, such as uplift and subsequent abrupt basin subsidence, together with volcanism in the Gondwana continental block. Mixed siliciclastic and carbonate cycles are typically intercalated in the prodelta to delta front deposits that developed mainly in a lagoon-like, restricted marine environment. The restricted marine environment developed during transgressions as the outflow of shallow water was restricted by depositional barriers. Around the barriers and/or delta lobes, carbonate shoals/banks were probably developed and the allochemical components of the neritic limestones may have been transported into the restricted marine environment by overwash processes and/or storm waves. Siliciclastic detritus, on the other hand, was mainly derived accompanied by delta progradation dominated by fluvial processes in the restricted marine environment. Therefore, we interpret the mixed siliciclastic and carbonate cycles in the deltaic successions to be a result of transgression-regression cycles in a deltaic system during the Late Triassic.

Analysis of organic matter from DSDP Leg 81 Holes

Organic geochemical and visual kerogen analyses were carried out on approximately 50 samples from Leg 81 (Rockall Plateau, North Atlantic). The sediments are from four sites (Sites 552-555), Pleistocene to Paleocene in age, and represent significantly different depositional environments and sources of organic matter. The Pleistocene glacial-interglacial cycles show differences in sedimentary organic matter based on Rock-Eval pyrolysis, organic phosphorus, and pyrolysis/mass-spectrometry analyses. Glacial samples contain more organic carbon, with a larger proportion of reworked organic matter. This probably reflects increased erosion of continental and shelf areas as a result of low sea level stands. Inter glacial samples contain a larger proportion of marine organic matter as determined by organic phosphorus and pyrolysis analyses. This immature, highly oxidized marine organic matter may be associated with the skeletal organic matrix of calcareous organisms. In addition, Rock-Eval data indicate no significant inorganic-carbonate contribution to the S3 pyrolysis peak. The Pliocene-Miocene sediments consist of pelagic, biogenic carbonates. The organic matter is similar to that of the Pleistocene interglacial periods; a mixture of oxidized marine organic matter and reworked, terrestrial detritus. The Paleocene-Oligocene organic matter reflects variations in source and depositional factors associated with the isolation of Rockall from Greenland. Paleocene sediments contain primarily terrestrial organic matter with evidence of in situ thermal stress resulting from interbedded lava flows. Late Paleocene and early Eocene organic matter suggests a highly oxidized marine environment, with major periods of deposition of terrestrially derived organic matter. These fluctuations in organic-matter type are probably the result of episodic shallowing and deepening of Rockall Basins. The final stage of Eocene/Oligocene sedimentation records the accelerating subsidence of Rockall and its isolation from terrestrial sources (Rockall and Greenland). This is shown by the increasingly marine character of the organic matter. The petroleum potential of sediments containing more than 0.5% organic carbon is poor because of their thermal immaturity and their highly oxidized and terrestrial organic-matter composition.

DISPRO datasets for validation of coastal hydrodynamic models

Appropriate field data are required to check the reliability of hydrodynamic models simulating the dispersion of soluble substances in the marine environment. This study deals with the collection of physical measurements and soluble tracer data intended specifically for this kind of validation. The intensity of currents as well as the complexity of topography and tides around the Cap de La Hague in the center of the English Channel makes it one of the most difficult areas to represent in terms of hydrodynamics and dispersion. Controlled releases of tritium - in the form of HTO - are carried out in this area by the AREVA-NC plant, providing an excellent soluble tracer. A total of 14 493 measurements were acquired to track dispersion in the hours and days following a release. These data, supplementing previously gathered data and physical measurements (bathymetry, water-surface levels, Eulerian and Lagrangian current studies) allow us to test dispersion models from the hour following release to periods of several years which are not accessible with dye experiments. The dispersion characteristics are described and methods are proposed for comparing models against measurements. An application is proposed for a 2 dimensions high-resolution numerical model. It shows how an extensive dataset can be used to build, calibrate and validate several aspects of the model in a highly dynamic and macrotidal area: tidal cycle timing, tidal amplitude, fixed-point current data, hodographs. This study presents results concerning the model's ability to reproduce residual Lagrangian currents, along with a comparison between simulation and high-frequency measurements of tracer dispersion. Physical and tracer data are available from the SISMER database of IFREMER (www.ifremer.fr/sismer/catal). This tool for validation of models in macro-tidal seas is intended to be an open and evolving resource, which could provide a benchmark for dispersion model validation.