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Plouzané, France

Hautot S.,IMAGIR Sarl | Tarits P.,IUEM
1st EAGE Eastern Africa Petroleum Geoscience Forum - Sharing Lessons Learned: What's Next?

The East African Rift region has a strong potential in oil&gas resources and is being under exploration in several areas. Complex geology, large volcanic provinces and remoteness make the exploration difficult and expensive. In the EAR, the basins are generally complicated geological structures because of active magmatism and control by tectonic directions inherited from syn-rifting and Precambrian faults. 3-D magnetotelluric (MT) can be used for preliminary investigations in order to provide an accurate geological background of possible prospects prior extensive seismic surveys. We report on results of 3-D inversion of MT data in the Turkana and Northern Tanzania. The method developed provides accurate models of the sharp resisitivity boundaries observed in these regions. Such a good resolution is necessary to obtain geological models able to help understand the nowadays structuration of the sedimentary basins by the active rifting and volcanism. Source

Paquet F.,University of Southern Brittany | Paquet F.,Bureau de Recherches Geologiques et Minieres | Menier D.,University of Southern Brittany | Estournes G.,University of Southern Brittany | And 3 more authors.
Marine Geology

High-resolution seismic data have been acquired in June 2008 on the Armorican Shelf (AS), in the northern Bay of Biscay, in order to reassess its stratigraphic architecture in detail and to study the impact of eustasy, tectonic and sediment delivery on the margin sedimentary record. Several profiles show fluvial-type incisions of several tens of meters (up to 54 m) associated to a widespread erosion surface. Several hypotheses are proposed for the stratigraphic position of this surface and incisions. We suggest Middle to Late Miocene age. Considering the relatively quiescent tectonic activity of the margin, we infer that the relative sea-level fall responsible of aerial incision on the Miocene shelf is eustasy-related. We propose the attested Serravallian-Tortonian eustatic lowstand (c. 11.6 Ma) as the key event responsible of such erosion and incision. This event marks the early beginning of the high-amplitude sea-level fluctuations that culminated during the Pleistocene and significantly controlled the present day AS morphology. The variability of vertical incision observed along single reaches can be explained by the confluence of several tributaries, the sinuosity of the channel and can be amplified by the unconsolidated nature of the Miocene substratum. The main pathways of the fluvial network corresponding to these buried valleys have been reconstructed and connections to other existing networks are proposed. © 2009 Elsevier B.V. All rights reserved. Source

Hamelin C.,IUEM | Dosso L.,CNRS Oceanic Domains Laboratory | Hanan B.B.,San Diego State University | Moreira M.,CNRS Paris Institute of Global Physics | And 2 more authors.
Earth and Planetary Science Letters

Samples collected during the PACANTARCTIC 2 cruise fill a sampling gap from 53° to 41° S along the Pacific Antarctic Ridge (PAR). Analysis of Sr, Nd, Pb, Hf, and He isotope compositions of these new samples is shown together with published data from 66°S to 53°S and from the EPR. The recent advance in analytical mass spectrometry techniques generates a spectacular increase in the number of multidimensional isotopic data for oceanic basalts. Working with such multidimensional datasets generates a new approach for the data interpretation, preferably based on statistical analysis techniques.Principal Component Analysis (PCA) is a powerful mathematical tool to study this type of datasets. The purpose of PCA is to reduce the number of dimensions by keeping only those characteristics that contribute most to its variance. Using this technique, it becomes possible to have a statistical picture of the geochemical variations along the entire Pacific Ridge from 70°S to 10°S. The incomplete sampling of the ridge led previously to the identification of a large-scale division of the south Pacific mantle at the latitude of Easter Island. The PCA method applied here to the completed dataset reveals a different geochemical profile. Along the Pacific Ridge, a large-scale bell-shaped variation with an extremum at about 38°S of latitude is interpreted as a progressive change in the geochemical characteristics of the depleted matrix of the mantle. This Pacific Isotopic Bump (PIB) is also noticeable in the He isotopic ratio along-axis variation. The linear correlation observed between He and heavy radiogenic isotopes, together with the result of the PCA calculation, suggests that the large-scale variation is unrelated to the plume-ridge interactions in the area and should rather be attributed to the partial melting of a marble-cake assemblage. © 2010 Elsevier B.V. Source

Schaeffer J.,IUEM | Casanova A.G.,CC IN2P3
Journal of Physics: Conference Series

TReqS is a new layer in the storage infrastructure at CCIN2P3 controlling the read operations for data stored on tapes in HPSS (a HSM) by centralizing all requests. The development and deployment of TReqS at CCIN2P3 has brought major advances in data access services on several aspects. First, by sorting and scheduling tape mounts, we radically reduce the waiting time due to media movements in the tape library. Second, in a mutualised environment where tape drives are globally available to all users, TReqS ensures the fair share of the drives. Finaly, TReqS softens the impact of unpredictable grid jobs and transfers on the actual tape library and efficiently masks the data access complexity to the end user. Source

Trinkler N.,IUEM | Labonne M.,Center Bretagne | Marin F.,University of Burgundy | Jolivet A.,French Research Institute for Exploitation of the Sea | And 4 more authors.
Analytical and Bioanalytical Chemistry

Since 1987, the Manila clam Ruditapes philippinarum has been regularly affected by the brown ring disease (BRD), an epizootic caused by the bacterium Vibrio tapetis. This disease is characterized by the development of a brown deposit on the inner face of valves. While most of the clams die from the BRD infection, some of them are able to recover by mineralizing a new repair shell layer, which covers the brown deposit by a process of encapsulation. The purpose of this work was to study the organic matrix of the shells of Manila clams in the inner shell layer before, during and after the brown deposit and during the shell repair process by confocal Raman micro-spectrometry and wavelength dispersive spectrometry (WDS) microprobe. In addition, the organic matrix of the repaired shell layer was extracted and quantified, by using standard biochemical shell matrix extractions protocols. The brown deposit exhibited high luminescence intensity in Raman spectra, and an increase of S, C, Sr (forming two peaks) and a decrease of Ca, Na concentrations (% w/w), using WDS microprobe mapping and cross-sectional transects. The signature of these trace elements was similar to that recorded on periostracal lamina (% w/w). The high S concentration likely corresponds to the presence of a high amount of sulfated organic compounds. Interestingly, on cross-sectional transects, before the brown deposit, a thin layer of the shell showed also a high luminescence, which may suggest that this layer is modified by bacteria. After the brown deposit, at the beginning of the shell repair process, the luminescence and the S concentration remain high, before declining the level found in non-BRD-affected shells. Quantification of the organic matrix shows that the shell repair layer zone is significantly different from non-BRD-affected shell layer, in particular with a much higher amount of insoluble matrix. © 2009 Springer-Verlag. Source

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