Exploring the seismic expression of fault zones in 3D seismic volumes

Acknowledgments The seismic interpretation and image processing has been run in the SeisLab facilty at the University of Aberdeen (sponsored by BG, BP and Chevron) Seismic imaging analysis was performed in GeoTeric (ffA), and Mathematica (Wolfram research). Interpretation of seismic amplitudes was performed Petrel 2014 (Schlumberger). We thank Gaynor Paton (Geoteric) for in depth discussion on the facies analysis methodology and significant suggestions to improve the current paper. We thank the New Zealand government (Petroleum and Minerals ministry) and CGG for sharing the seismic dataset utilized in this research paper. Seismic images used here are available through the Virtual Seismic Atlas (www.seismicatlas.org). Nestor Cardozo and an anonymous reviewer are thanked for their constructive comments and suggestions that strongly improved the quality and organization of this paper.Peer reviewedPostprin

Evidence for intense REE scavenging at cold seeps from the Niger Delta margin

International audienceFor many trace elements, continental margins are the location of intense exchange processes between sediment and seawater, which control their distribution in the water column, but have yet to be fully understood. In this study, we have investigated the impact of fluid seepage at cold seeps on the marine cycle of neodymium. We determined dissolved and total dissolvable (TD) concentrations for REE and well-established tracers of fluid seepage (CH4, TDFe, TDMn), and Nd isotopic compositions in seawater samples collected above cold seeps and a reference site (i.e. away from any fluid venting area) from the Niger Delta margin. We also analyzed cold seep authigenic phases and various core-top sediment fractions (pore water, detrital component, easily leachable phases, uncleaned foraminifera) recovered near the hydrocast stations. Methane, TDFe and TDMn concentrations clearly indicate active fluid venting at the studied seeps, with plumes rising up to about 100 m above the seafloor. Depth profiles show pronounced REE enrichments in the non-filtered samples (TD concentrations) within plumes, whereas filtered samples (dissolved concentrations) exhibit slight REE depletion in plumes relative to the overlying water column and display typical seawater REE patterns. These results suggest that the net flux of REE emitted into seawater at cold seeps is controlled by the presence of particulate phases, most probably Fe-Mn oxyhydroxides associated to resuspended sediments. At the reference site, however, our data reveal significant enrichment for dissolved REE in bottom waters, that clearly relates to diffusive benthic fluxes from surface sediments. Neodymium isotopic ratios measured in the water column range from εNd ~−15.7 to − 10.4. Evidence that the εNd values for Antarctic Intermediate waters (AAIW) differed from those reported for the same water mass at open ocean settings shows that sediment/water interactions take place in the Gulf of Guinea. At each site, however, the bottom water εNd signature generally differs from that for cold seep minerals, easily leachable sediment phases, and detrital fractions from local sediments, ruling out the possibility that seepage of methane-rich fluids and sediment dissolution act as a substantial source of dissolved Nd to seawater in the Gulf of Guinea. Taken together, our data hence suggest that co-precipitation of Fe-Mn oxyhydroxide phases in sub-surface sediments leads to quantitative scavenging of dissolved REE at cold seeps, preventing their emission into bottom waters. Most probably, it is likely that diffusion from suboxic surface sediments dominates the exchange processes affecting the marine Nd cycle at the Niger Delta margin

Differential Selection on Carotenoid Biosynthesis Genes as a Function of Gene Position in the Metabolic Pathway: A Study on the Carrot and Dicots

Background: Selection of genes involved in metabolic pathways could target them differently depending on the position of genes in the pathway and on their role in controlling metabolic fluxes. This hypothesis was tested in the carotenoid biosynthesis pathway using population genetics and phylogenetics. Methodology/Principal Findings: Evolutionary rates of seven genes distributed along the carotenoid biosynthesis pathway

Approche des facteurs de contamination des eaux souterraines par l'atrazine et la simazine. Cas des aquifères de la Manche

La recherche de triazines a été effectuée dans l'eau de 149 captages du département de la Manche. Seules l'atrazine et la simazine ont été retrouvées et sur un faible nombre de points d'eau uniquement. Une étude statistique montre que les ouvrages dont les teneurs en atrazine ou en simazine sont supérieures au seuil de détection sont situés dans les terrains sédimentaires carbonatés. Les captages implantés dans les formations du socle semblent bénéficier d'une protection pouvant s'expliquer par la fixation des triazines par les argiles et par leur dégradation compte tenu de la faible perméabilité des terrains mais aussi pour partie en raison d'une moindre intensification agricole dans ces secteurs. La recherche des métabolites de ces molécules s'avère cependant indispensable pour appréhender correctement les modalités de transfert de celles-ci

Epitaxial growth and cationic exchange properties of layered KNb 3 O 8 thin films

International audienc

Use of carrot genetic resources to understand root carotenoid content: preliminary steps to an association mapping study

Association mapping becomes one of the major genetic methods used to understand genetic control of complex traits. This method allows the use of natural populations with high resolution thanks to ancestral recombinations. Resolution is given by linkage disequilibrium (LD) extend. But false positives can be detected when phenotypic traits are correlated with underlying population stratification at non causal loci. Knowledge of population structure is then a preliminary step for association mapping studies. Here we investigated the population structure in cultivated carrot and the LD extend in the carotenoid isomerase gene, a key gene in the carotenoid biosynthesis pathway. An unexpected high LD for outcrossing species was found in this gene. Population stratification analysis confirmed the differentiation of the carrot germplasm in two clusters. The first one comprised European and American accessions, the second one Asian accessions. These are preliminary steps to perform association mapping studies to understand root carotenoid content in cultivated carrot