The sandy channel-lobe depositional systems in the Gulf of Cadiz: Gravity processes forced by contour current processes
The sedimentation in the Gulf of Cadiz (NE Atlantic Ocean) is significantly controlled by the Mediterranean Outflow Water (MOW). Along its pathway onto the continental slope, the MOW is canalized by contourite channels, some of them feeding gravity sandy channel-lobe depositional systems firstly recognized in previous study [Habgood et al., 2003. Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic. Sedimentology 50(3), 483-510.].Using very high resolution acoustic data and cores, a detailed characterization and a new evolution pattern of these channel-lobe depositional systems is established. Complex internal geometry of the lobes shows several depositional units revealing a polyphase evolution of these systems, with a general progradation punctuated by retrogradation and avulsion phases. A gravity origin controlled by contouritic processes and climatic changes is demonstrated for the feeding and the evolution of these sandy channel-lobe depositional systems. Climate oscillations, via the MOW variations, act as a major forcing of the activity of the channel-lobe depositional systems during the Late Quaternary.
(Sedimentary Geology. vol. 229, n° 0037-0738, pp. 110-123, 01/08/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER, LFCR, UPPA, CNRS
Variations of the Antarctic Circumpolar Current intensity during the past 500 ka
[1] We examine the past variations of the Antarctic Circumpolar Current (ACC) by using variations in size and abundance of the magnetic grains deposited by this current at a site east the Kerguelen-Crozet plateau. Core MD00-2375G was taken at a midlatitude site during the ANTAUS cruise conducted in 2000 by the French R/V Marion Dufresne. Marine isotope stages (MIS) down to MIS 13 are identified, and an age model is derived from a correlation to the ice core isotopic record obtained from EPICA in Antarctica. Continuous records of abundance and size of the magnetic grains were obtained using environmental magnetism methods. Results show a strong modulation of the ACC flow intensity in response to glacial and interglacial cycles. The low abundance and the small size of magnetic grains indicate that the ACC was weak during warm stages and strong during glacial epochs. A large modulation is also observed at the sub-stage scale during the interglacials. A minimum in concentration and grain size occurs at the onset of MIS 11. At the MIS 6-5, 10-9, and possibly 12-11 transitions, observed variations suggest a mechanism involving both rapid and progressive variations of the ACC flow at deglaciations.
(Geochemistry, Geophysics, Geosystems. vol. 11, pp. n/a-n/a, 01/08/2010)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
High-resolution analysis of submarine lobes deposits: Seismic-scale outcrops of the Lauzanier area (SE Alps, France)
The Lauzanier area represents the northernmost extension of the Annot Sandstone series and contains deposits between 650 and 900 m-thick. This basin was active from upper Bartonian or lower Priabonian to early Rupelian. It is composed of two superposed units separated by a major unconformity. The sediment supply is due to channelled flows coming from the south. Flow processes include mass flow to turbidity currents. The size of the particles and the absence of fine-grained sediment suggest a transport over a short distance. The Lower Unit is made of coarse-grained tabular beds interpreted as non-channelled lobe deposits. The Upper Unit is made of massive conglomerates interpreted as the channelled part of lobes. These lobe deposits settle in a tectonically confined basin according to topographic compensation that occurs from bed scale to unit scale. The abrupt progradation between the lower and the upper unit seems related to a major tectonic uplift in the area. This uplift is also suggested by a change in the petrographic nature of the source and an abrupt coarsening of the transported clasts. This field example allows providing high resolution analysis for depositional sedimentary sequences of terminal lobe deposits in a coarse-grained turbidite system. The outcrop analysis shows the lateral evolution of deposits and the system progradation allows a longitudinal analysis of facies evolution by superposing on the same outcrops the channelled lobe system and the non-channelled lobe system. These results of high-resolution outcrop analysis can be extrapolated to results obtained on sedimentary lobes in recent deep-sea turbidite system that are either restricted to cores, or with a lesser resolution (seismic).
(Sedimentary Geology. vol. 229, n° 0037-0738, pp. 160-191, 01/08/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, AREVA-BU Mines, IFPEN, GR, UR, INSU - CNRS, CNRS, UPPA, GM, IFREMER
Long-term monitoring (1960–2008) of the river-sediment transport in the Red River Watershed (Vietnam): Temporal variability and dam-reservoir impact
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(Science of the Total Environment. vol. 2010, n° 0048-9697, pp. 4654-4664, 31/07/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Bioemco, ENS-PSL, PSL, IRD, INRA, UPMC, CNRS, IWMI-SEA, IWMI, CGIAR, SFRI, VAAS
Metal fluxes to the sediments of the Moulay Bousselham lagoon, Morocco.
The metal content in surface sediments (0-2 cm, 26 samples), in a sediment core (120, 1 cm slices), taken from Moulay Bousselham (Morocco) was investigated. Concentrations of Al, Fe, Mn, Pb, Zn, Cu, Ni, Cr, Cd, As, and Hg were evaluated in surface and cored sediments of Moulay Bousselham lagoon. Significantly high concentrations in lg g-1 dw of Pb (31.7-6.2), Zn (758.9-167), Cu (310.7- 22), Ni (96-10.5), Cr (113-18.9), Cd (0.84-0.02), As (1-0.1), and Hg (0.61-0.02) were found in sediment samples from Moulay Bousselham lagoon. Calculated enrichment factors [EFMe = (Me/Al)sample/(Me/Al)background], using Al as a normalizer, and correlation matrices showed that metal pollution in Merja Zerga of Moulay Bousselham lagoon was the product of anthropogenic sources, while the metal content in Merja Kehla was of natural origins. The results suggest that a major change in the sedimentary regime of the lagoon, associated with internal trapping and re-distribution of heavy metal, has been occurring in the past few decades. The cause would appear to be the construction of a Nador Canal at the lagoon. Probable effects concentrations (PEC) were often exceeded for heavy metals in the lagoon sediments, especially for Zn, Cu, Ni, and Cr, and four stations, stations MZ-11, MZ-12, MZ-13, MZ-14, MZ-16, and MZ-17, had multiple metals at presumptively toxic levels. These comparisons suggest that sediment metal levels in the river are clearly high and probably pose an environmental risk at some stations. The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance when contamination issues are at stake. Metal concentrations found in Moulay Bousselham lagoon were comparable to aquatic systems classified as contaminated from other regions of the world.
(Environmental Earth Sciences. vol. 61, n° 1866-6280, pp. 275-286, 01/07/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LETG - Nantes, UNICAEN, NU, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN
Contrasting paleoceanographic conditions off Morocco during Heinrich events (1 and 2) and the Last Glacial Maximum
(Quaternary Science Reviews. vol. 29, n° 0277-3791, pp. 1923-1939, 01/07/2010)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, IIQAB-CSIC, CSIC
Modélisation couplée vagues-courant : développement avec MARS 3D et WAVEWATCH-III
(pp. 17-24, 20/06/2010)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER
Pliocene and Lower Pleistocene vegetation and climate changes at the European scale: Long pollen records and climatostratigraphy
The biostratigraphically calibrated long pollen record at DSDP Site 380 (southwestern Black Sea) displays a high-resolution continuous and contrasted evolution of the vegetation in the region for the entire Pliocene and Lower Pleistocene. An accurate correlation is established with the reference global oxygen isotopic curve and with the Northwestern European climatostratigraphy. Climatostratigraphic relationships are evident at the latitudinal and longitudinal scale of Europe, confirming the extensive strength of pollen analysis as a tool for correlations over large distances.
(Quaternary International. vol. 219, n° 1040-6182, pp. 152-167, 17/06/2010)
LDO, INSU - CNRS, UBO EPE, CNRS, AYBE, ITÜ, ITÜ, PEPS, UCBL, INSU - CNRS, CNRS, GeoEcoMar, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS
Large scale Vorticity generation due to dissipating waves in the surf zone.
In this paper, we investigate the mechanisms which control the generation of wave-induced mean current vorticity in the surf zone. From the vertically-integrated and time-averaged momentum equations given recently by Smith [21], we obtain a vorticity forcing term related to differential broken-wave energy dissipation. Then, we derive a new equation for the mean current vorticity, from the nonlinear shallow water shock-wave theory. Both approaches are consistent, under the shallow water assumption, but the later gives explicitly the generation term of vorticity, without any ad-hoc parametrization of the broken-wave energy dissipation.
(Discrete and Continuous Dynamical Systems - Series B. vol. 13, n° 1531-3492, pp. 729--738, 16/06/2010)
I3M, UM2, UM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM