|
|
|
| Registros recuperados: 15 | |
|
| |
|
|
| Thomas, Elizabeh R; Allen, Claire S; Etourneau, Johan; King, Amy Cf; Severi, Mirko; Winton, V. Holly L.; Mueller, Juliane; Crosta, Xavier; Peck, Victoria L.. |
| Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate archives, from marine sedimentary records and coastal Antarctic ice cores, provide a means of understanding sea ice variability and its drivers over decadal to centennial timescales. In this study, we collate published records of Antarctic sea ice over the past 2000 years (2 ka). We evaluate the current proxies and explore the potential of combining marine and ice core records to produce multi-archive reconstructions. Despite identifying 92 sea ice reconstructions, the spatial and temporal... |
| Tipo: Text |
Palavras-chave: Sea ice; Antarctica; Paleoclimate; Ice cores; Marine sediments. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00595/70709/68916.pdf |
| |
|
|
| Durbin, Alan M.; Teske, Andreas. |
| Examining the patterns of archaeal diversity in little-explored organic-lean marine subsurface sediments presents an opportunity to study the association of phylogenetic affiliation and habitat preference in uncultured marine Archaea. Here we have compiled and re-analyzed published archaeal 16S rRNA clone library datasets across a spectrum of sediment trophic states characterized by a wide range of terminal electron-accepting processes. Our results show that organic-lean marine sediments in deep marine basins and oligotrophic open ocean locations are inhabited by distinct lineages of archaea that are not found in the more frequently studied, organic-rich continental margin sediments. We hypothesize that different combinations of electron donor and acceptor... |
| Tipo: Text |
Palavras-chave: Archaea; Marine sediments; Oligotrophy; Subsurface; Phylogeny; Uncultured archaea. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00263/37444/35695.pdf |
| |
|
|
| Omoregie, E; Mastalerz, V; De Lange, G; Straub, K; Kappler, A; Roy, H; Stadnitskaia, A; Foucher, Jean-paul; Boetius, A. |
| In this study we determined the composition and biogeochemistry of novel, brightly colored, white and orange microbial mats at the surface of a brine seep at the outer rim of the Chefren mud volcano. These mats were interspersed with one another, but their underlying sediment biogeochemistries differed considerably. Microscopy revealed that the white mats were granules composed of elemental S filaments, similar to those produced by the sulfide-oxidizing epsilonproteobacterium "Candidatus Arcobacter sulfidicus." Fluorescence in situ hybridization indicated that microorganisms targeted by a "Ca. Arcobacter sulfidicus"-specific oligonucleotide probe constituted up to 24% of the total the cells within these mats. Several 16S rRNA gene sequences from organisms... |
| Tipo: Text |
Palavras-chave: Gulf of mexico; Sulfate reducing bacteria; Egyptian continental margin; Northeast pacific ocean; Ribosomal rna sequences; In situ hybridization; Anaerobic oxidation; Marine sediments; Gas hydrate; Oxiding bacteria. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6201.pdf |
| |
|
| |
|
|
| Sultan, Nabil; Marsset, Bruno; Ker, Stephan; Marsset, Tania; Voisset, Michel; Vernant, Antoine-mathieu; Bayon, Germain; Cauquil, Eric; Adamy, J.; Colliat, J. L.; Drapeau, D.. |
| Based on acquired geophysical, geological and geotechnical data and modeling, we suggest hydrate dissolution to cause sediment collapse and pockmark formation in the Niger delta. Very high-resolution bathymetry data acquired from the Niger delta reveal the morphology of pockmarks with different shapes and sizes going from a small ring depression surrounding an irregular floor to more typical pockmarks with uniform depression. Geophysical data, in situ piezocone measurements, piezometer measurements and sediment cores demonstrate the presence of a common internal architecture of the studied pockmarks: inner sediments rich in gas hydrates surrounded by overpressured sediments. The temperature, pressure and salinity conditions of the studied area have allowed... |
| Tipo: Text |
Palavras-chave: Methane gas hydrate; Sea floor; Marine sediments; Pore pressure; Porous media; Continental margin; Clathrate hydrate; Fluid flow; Stability; Slope. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00012/12300/9092.pdf |
| |
|
|
| Passier, Hf; Dekkers, Mj. |
| Low-temperature magnetic properties of eastern Mediterranean sediments from a box-core have been investigated. This box-core contains the present-day oxic-suboxic boundary that is situated at the top of the relic of the youngest sapropel (S1). The upper half of sapropel S1 has been oxidized, and Fe oxides have precipitated in the oxidized sapropel. Zero-field-cooling (ZFC) and field-cooling (FC) saturation remanent magnetization (M-r; induced in a field of 2.5 T at 20 K after cooling from 300 K with or without the 2.5 T field) was measured during warming to 300 K. An M (r) imparted at room temperature (RTSIRM) was cycled to 20 K as well. The difference between ZFC and FC curves around the Verwey transition, as estimated by the parameter delta(FC)... |
| Tipo: Text |
Palavras-chave: Geochemistry; Low-temperature magnetism; Magnetite; Marine sediments; Oxidation; Sediment magnetism. |
| Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00223/33399/31887.pdf |
| |
|
|
| Nouze, Herve; Henry, P; Noble, M; Martin, V; Pascal, G. |
| Previous studies have revealed the presence of a widespread Bottom Simulating Reflector (BSR) on the eastern Nankai slope, as well as the occurrence of enigmatic high amplitude reflections that extend well above the BSR. New high-resolution 2-D seismic data were collected on the eastern Nankai slope, during the French-Japanese SFJ cruise in year 2000 and AVA analyses of the enigmatic reflectors are conducted. At the studied location, these analyses suggest that high amplitude anomalies above the BSR delineate the top of gas hydrate rich sediments. Several tens % of the sediment porosity would be filled with gas hydrates between the BSR and a sharp boundary 30 to 60 m above. To account for these observations, we propose that an invasion by free gas of the... |
| Tipo: Text |
Palavras-chave: Zone; Model; Ridge; Methane gas; Marine sediments. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-510.pdf |
| |
|
|
| Kissel, C.; Sarnthein, M.; Laj, C.; Wang, P. X.; Wandres, C.; Egli, R.. |
| More than 650 million tons/year of fluvial sediment are delivered from continental regions into the South China Sea (SCS). Previous studies have shown that the composition of the magnetic fraction of riverine sediments drained into the SCS is significantly variable from north to south. On the basis of this evidence, we now examine a full set of magnetic properties for a number of core‐tops taken at water depth comprised mostly between 800 and 3500 m. Room‐temperature magnetic parameters and thermal spectra are used to obtain information about the concentration and mineralogical magnetic composition. Spatial changes are observed in the relative proportion of magnetite and hematite with an increase of the latter toward the south, similarly to the observation... |
| Tipo: Text |
Palavras-chave: South China Sea; Magnetic mineralogy; Marine sediments. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00443/55502/57048.pdf |
| |
|
|
| Passier, Hf; De Lange, Gj; Dekkers, Mj. |
| Magnetic properties (IRM, ARM, chi (in), S-ratio at 0.3 T, room temperature (RT) hysteresis and thermomagnetic curves) and geochemical data (Fe, S, Mn, Al, Ti, organic C) were studied in two eastern Mediterranean boxcores (ABC26 and BC19) at a resolution of 3-5 mm. The boxcores contain sapropel S1 (9-6 kyr BP) at a few decimetres below seafloor. The magnetic fraction consists predominantly of single-domain (SD) to pseudo-single-domain (PSD) magnetite in the entire cores. The original input of magnetic grains comes from two sources: aeolian dust (both cores) and volcanic ash from the Minoan eruption of Santorini (core BC19 only). Non-steady-state diagenesis has changed the magnetic mineralogy considerably in these alternating organic-rich /organic-poor... |
| Tipo: Text |
Palavras-chave: Geochemistry; Magnetite; Marine sediments; Mediterranean Sea; Oxidation; Sediment magnetism. |
| Ano: 2001 |
URL: https://archimer.ifremer.fr/doc/00221/33184/31805.pdf |
| |
|
|
| Gruenke, S.; Lichtschlag, A.; De Beer, D.; Felden, J.; Salman, V.; Ramette, A.; Schulz-vogt, H. N.; Boetius, A.. |
| This study investigated the bacterial diversity associated with microbial mats of polar deep-sea cold seeps. The mats were associated with high upward fluxes of sulfide produced by anaerobic oxidation of methane, and grew at temperatures close to the freezing point of seawater. They ranged from small patches of 0.2-5 m in diameter (gray mats) to extensive fields covering up to 850 m(2) of seafloor (white mats) and were formed by diverse sulfide-oxidizing bacteria differing in color and size. Overall, both the dominant mat-forming thiotrophs as well as the associated bacterial communities inhabiting the mats differed in composition for each mat type as determined by microscopy, 16S rRNA gene sequencing and automated ribosomal intergenic spacer analysis.... |
| Tipo: Text |
Palavras-chave: Mosby mud volcano; Gulf of mexico; Eastern mediterranean sea; Filamentous sulfur bacteria; Sulfide oxidizing bacteria; In situ hybridization; Sulfate reduction; Microbial communities; Marine sediments; Beggiatoa spp. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00212/32360/30823.pdf |
| |
|
|
| Heimbuerger, Lars-eric; Cossa, Daniel; Thibodeau, Benoit; Khripounoff, Alexis; Mas, Virginie; Chiffoleau, Jean-francois; Schmidt, Sabine; Migon, Christophe. |
| The magnitude and the chronology of anthropogenic impregnation by Hg and other trace metals of environmental concern (V, Cr, Ni, Cu, Zn, Ag, Cd and Pb, including its stable isotopes) in the sediments are determined at the DYFAMED station, a site in the Ligurian Sea (Northwestern Mediterranean) chosen for its supposed open-sea characteristics. The DYFAMED site (VD) is located on the right levee of the Var Canyon turbidite system, at the end of the Middle Valley. In order to trace the influence of the gravity current coming from the canyon on trace metal distribution in the sediment, we studied an additional sediment core (VA) from a terrace of the Var Canyon, and material collected in sediment traps at the both sites at 20 m above sea bottom. The patterns... |
| Tipo: Text |
Palavras-chave: Marine sediments; Sediment traps; Mercury; Trace metals; Lead isotopes; Geochronology. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00073/18435/16125.pdf |
| |
|
|
| Zhao, Xueqin. |
| South Africa is very sensitive to climate change, because it is located between two atmospheric systems (subtropical and warm-temperate systems) and two oceanic systems (Benguela Current and Agulhas Current). Presently, the seasonal changes of atmospheric and oceanic systems induce a pronounced rainfall seasonality comprised of three different rainfall zones (summer rainfall zone, SRZ; year-round rainfall zone, YRZ and winter rainfall zone, WRZ) over South Africa. However, the seasonality development during the Holocene in South Africa is poorly understood and the driving forces of the climate change are debated. Therefore, this study aims to provide a detailed reconstruction of Holocene climate and vegetation variability of South Africa,... |
| Tipo: Text |
Palavras-chave: Holocene; Marine sediments; Pollen; Microcharcoal; Organic-walled dinoflagellate cyst; Paleoenvironment; Paleoceanography; South Africa. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00493/60442/63887.pdf |
| |
|
| |
|
|
| Govin, A.; Capron, E.; Tzedakis, P. C.; Verheyden, S.; Ghaleb, B.; Hillaire-marcel, C.; St-onge, G.; Stoner, J. S.; Bassinot, F.; Bazin, L.; Blunier, T.; Combourieu-nebout, N.; El Ouahabi, A.; Genty, D.; Gersonde, R.; Jimenez-amat, P.; Landais, A.; Martrat, B.; Masson-delmotte, V.; Parrenin, F.; Seidenkrantz, M. -s.; Veres, D.; Waelbroeck, C.; Zahn, R.. |
| The Last Interglacial (LIG) represents an invaluable case study to investigate the response of components of the Earth system to global warming. However, the scarcity of absolute age constraints in most archives leads to extensive use of various stratigraphic alignments to different reference chronologies. This feature sets limitations to the accuracy of the stratigraphic assignment of the climatic sequence of events across the globe during the LIG. Here, we review the strengths and limitations of the methods that are commonly used to date or develop chronologies in various climatic archives for the time span (similar to 140 -100 ka) encompassing the penultimate deglaciation, the LIG and the glacial inception. Climatic hypotheses underlying record... |
| Tipo: Text |
Palavras-chave: Last Interglacial; Penultimate deglaciation; Last glacial inception; Chronology; Corals; Speleothems; Ice cores; Marine sediments; Peat and lake sediments; Climate dynamics. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00496/60802/64786.pdf |
| |
| Registros recuperados: 15 | |
|
|
|
