The Columbia Channel-levee system: a fan drift in the southern Brazil Basin
The Columbia Channel is a turbiditic channel elongated W-E on the rise of the south Brazilian basin (4200 to 5000 m water depth). The whole area is swept by the northward flowing Antarctic Bottom Water. As a consequence, depositional processes have built a fan drift system. This system displays a levee along the northern flank of the channel while no levee occurs on its southern flank due to the Coriolis effect. The levee (400 km in length and 100 to 200 km in width) is bounded to the north by the Vitoria-Trindade Seamounts. It shows, first, a W-E trend parallel to the channel axis and predominantly turbiditic pattern, and then a S-N trend parallel to the rise contours with a predominant contouritic pattern. Its thickness is up to 1000 m. The distribution of sedimentary processes and associated deposits were investigated on the basis of water gun seismic and 3.5 kHz echosounding profiles, and core lithology. On the lower S-N part of the levee, the deposits consist of muddy contourites. On the shallowest part, turbidites that originate from the upper continental margin in the channel and on the southern part of the levee close to the channel, and from the Vitoria-Trindade Seamounts on the northern part of the levee, are interbedded with contouritic muds, and top-truncated silty turbidites. Areas subjected to turbidity current processes show chaotic to well-stratified, high amplitude reflections, in the subsurface, and more or less prolonged echofacies with or without sub-bottom reflectors, at the seabed. Areas subjected to contour currents show, in the subsurface, transparent seismofacies with some discontinuous low amplitude wavy reflections, and, in the surficial deposits, predominant wavy echofacies with sub-bottom relectors, frequently associated with tangential hyperbolae.
(Geological Society of London Memoirs. vol. 22, n° 0435-4052, pp. 223-238, 01/01/2002)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The Vema contourite fan in the South Brazilian basin
The Vema contourite fan is a Neogene mud-rich accumulation (200-400 m thick), fed by Antarctic Bottom Water bottom currents and located downstream of the Rio Grande Rise. It forms one single, mounded, fan-shaped body deposited between two major channels through which the main part of the deep AABW circulation is funneled. A suite of cores and seismic lines have been collected over the whole area. The sediments deposited below the shear zone between the two current branches consist almost exclusively of muddy contourites, either homogeneous in structure or micro-brecciated. Manganiferous deposits occur in the vicinity of the channels and on the channel floors. As a result of the morphological and hydrological background, the contourite drift has prograded mostly downstream. It is composed of several depositional units bounded by widespread discontinuities showing erosional patterns. This geometry results from an alternation of episodes of strong and unstable erosive currents, and periods of relatively weak and stable depositional currents
(Geological Society of London Memoirs. vol. 22, n° 0435-4052, pp. 209-222, 01/01/2002)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records
(Quaternary Science Reviews. vol. 21, n° 0277-3791, pp. 295-305, 01/01/2002)
PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, WHOI, ANU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Peut-on évaluer le rôle de la sédimentation sur l'effet de serre à l'échelle de temps des cycles orbitaux ?Can the role of sedimentation in the greenhouse effect at the time scale of orbital cycles be evaluated?
The evolution of the atmospheric CO 2 content is partly a response to the lack of balance between oceanic sedimentation and continental weathering, because the oceanic C reservoir tends to balance net inputs or losses from slow processes by rapid exchanges with the atmospheric reservoir. This response strongly depends on both amplitudes and time scales of the related processes. At Milankovitch or lower time scales, global models generally do neglect organic matter fossilisation, but such an assumption is only valid for oligotrophic systems. In eutrophic or mesotrophic systems, organic matter is not negligible and should be considered relatively to the carbonate sedimentation in order to know whether the impact of the sedimentation was a source or a sink for atmospheric CO 2. To cite this article: P. Bertrand, C. R. Geoscience 334 (2002) 521-528.
(Comptes Rendus. Géoscience. vol. 334, n° 1631-0713, pp. 521-528, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evolution d'une barre sableuse sous un courant permanent
Des expériences ont été réalisés pour évaluer la paramétrisation du transport sédimentaire dans un courant permanent. Une barre de sable est placée perpendiculairement au courant permanent d'intensité U. Différentes valeurs de U ont été considérées afin d'observer différents régimes de transport pour différentes tailles de sédiment. Pour nos essais, il apparaît que le débit solide dépend fortement de la vitesse de l'écoulement et peu du diamètre du sédiment.
(pp. 205-212, 21/02/2026)
LEGI, UJF, Grenoble INP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Corrélation des niveaux fossilifères marins interstratifiés dans les gypses messiniens, entre la carrière de Los Yesos et la carrière de Molinos de Aguas (bassin de Sorbas, SE Espagne)
Deux niveaux fossilifères marins ont été récemment découverts intercalés dans la série évaporitique messinienne de la carrière de Molinos de Aguas (bassin de Sorbas, SE Espagne). Le plus ancien correspond à des marnes noires riches en poissons Clupeidae appartenant à l’espèce Sardina crassa (Sauvage, 1873), alors que le plus récent est constitué de marnes et calcaires gris pâle contenant le bivalve Neopycnodonte navicularis (Brocchi, 1814) et l’échinide Brissopsis lyrifera (Forbes, 1841). Ces interruptions de la série évaporitique par des niveaux marins fossilifères signent des remises en eau locale de l’Est du bassin de Sorbas, dans un contexte marin de salinité peu différente de la normale. Sur le plan stratigraphique et paléoenvironnemental, ces intercalations marines sont interprétées comme les équivalents latéraux de deux des trois niveaux à fossiles marins précédemment découverts interstratifiés dans la série évaporitique de Los Yesos, à l’Ouest du bassin de Sorbas : 1) les argiles noires à poissons de Molinos de Aguas pourraient constituer l’équivalent de l’un des deux faciès de sables noirs à huîtres et pectinidés de Los Yesos ; et 2) les marnes et calcaires gris à Neopycnodonte et Brissopsis de Molinos de Aguas seraient l’équivalent des marnes et calcaires gris à Neopycnodonte et Brissopsis de Los Yesos.
(Geodiversitas. vol. 24, n° 1280-9659, pp. 659-667, 21/02/2026)
GR, UR, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, MNHN, CNRS
Combined 3D-spectrofluorometry, high performance liquid chromatography and capillary electrophoresis for the characterization of dissolved organic matter in natural waters
3D-spectrofluorometry, high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) were used to differentiate between marine and fresh water samples. These three techniques were used to obtain different patterns for marine and fresh waters, thus confirming that the organic materials they contain are different. The HPLC fractionation allowed the separation of different classes of dissolved organic matter (DOM) components. Their further analyses using both 3D spectrofluorometry and CE demonstrated that the isolated fractions were specific of the water origin. Furthermore, capillary electrophoresis was shown to have a considerable potential for fingerprinting and for a better characterisation of DOM of different origins. \textcopyright 2002 Elsevier Science Ltd. All rights reserved.
(Organic Geochemistry. vol. 33, n° 0146-6380, pp. 221--236, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Late quaternary variations of elemental ratios (C/Si and N/Si) in diatom-bound organic matter from the Southern Ocean
The carbon cycle in the Southern Ocean is considered as a major factor controlling past atmospheric CO 2 concentration variations. However, accumulation rates of biogenic opal are not linearly related to carbon burial rates. Here, we show that it is possible to measure the carbon and nitrogen content of diatom-bound organic matter (%C diat and %N diat, respectively) and that the signals recorded do not appear to be analytical artifacts. Analyses of two cores from the Atlantic and Indian sectors of the Southern Ocean show that %C diat and %N diat change on glacial-interglacial cycles by 30-40% and 120-175%, respectively. Accordingly, C/N ratios vary between 3 and 7 on glacial-interglacial timescales. If changes recorded in the occluded organic matter are representative of the changes in the diatom bulk organic matter, this provides a new tool to document the carbon cycle in the Southern Ocean and to determine its role on past atmospheric pCO 2 variations. Laboratory experiments on diatom cultures are needed to validate the use of diatom organic bound C and N as a tracer of diatom physiology and of carbon export from surface waters.
(Deep Sea Research Part II: Topical Studies in Oceanography. vol. 49, n° 0967-0645, pp. 1939-1952, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Effet de la turbidité sur la dégradation des pigments phytoplanctoniques dans l'estuaire de la GirondeEffect of turbidity on phytoplanktonic pigments degradation in the Gironde Estuary
In the Gironde Estuary, most part of phytoplanktonic material carried by the rivers is mineralised in the maximum turbidity zone (MTZ). In order to follow the degradation of the phytoplanktonic material into the MTZ, we developed an in vitro approach based on the monitoring of phytoplanktonic pigments. Algal material from two chlorophytes ( Scenedesmus suspicatus Chaudat and Chlamydomonas sp.) was incubated in the dark during 28 days into water samples from the Gironde estuary MTZ, at variable suspended solid concentrations (SPM) as well as in a sterilised turbid sample. First order decay constants of chlorophylls a and b and lutein increased by a factor 3 to 5 between SPM of 0 and 3 g l-1. The production of pheophytin a in the presence of particles and the lack of degradation in the sterilised turbid sample confirmed the effect of attached bacteria on the particles. To cite this article: E. Lemaire et al., C. R. Geoscience 334 (2002) 251-258.
(Comptes Rendus. Géoscience. vol. 334, n° 1631-0713, pp. 251-258, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Oligocene reefal deposits in the Pisang Ridge and the origin of the Lucipara Block (Banda Sea, eastern Indonesia)
In 1998 we dredged early Oligocene/late Oligocene boundary, shallow-water reefal deposits and pelagic, early Pliocene muds in the submerged Pisang Ridge. The shallow-water deposits were identified as moderate- to low-energy coral-reef depositional environments, which confirms that the PisangRidg e belonged to the continental to continental-arc Lucipara Block which also includes the TukangBesi, Lucipara and Rama ridges. On the basis of these findings, it was possible to reconstruct parts of the general geological evolution of the Lucipara Block, which drifted away from northern Irian Jaya duringmid- Miocene times and collided with the Kolonodale Block during the late Miocene. A late-early Oligocene calc alkaline volcanic arc developed in the Weber Trough area, then uplifted to a shallow-water position at the early–late Oligocene boundary in the Pisang Ridge. Late Oligocene–early Miocene metamorphism subsequently developed, prior to the deposition of early Miocene coral reefs in the Rama Ridge. Locally, late Miocene metamorphism was identified in the Lucipara Ridge, prior to the latest Miocene–Pliocene general drowning and the splitting of the Lucipara Block into several small blocks throughout the Banda Sea region.
(Geo-Marine Letters. vol. 22, n° 0276-0460, pp. 66-74, 21/02/2026)
CNRS, SPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS