Éditeur(s) : ISTPM
Résumé : The study of the foraminifers contained in the samples collected by the "President-Theodore-Tissier" during its 1948 cruise enabled:1° to draw up the list of the genera and species dwelling in the north-eastern Atlantic Ocean;2° to notice that some of these species are widely distributed but that others are localized in these areas. Among them are:Quinqueloculina angulataQuinqueloculina dunkerquianaQuinqueloculina lataQuinqueloculina quadrangularisGaudryina rudisNonionella turgidaBolivina pseudo-plicataBolivina laevigataDiscorbis globularis var. anglicaDiscorbis millettiiDiscorbis nitida3° to clarify a few taxonomic points for some species;4° to classify the different stations according to the nature of the sea bed and to determine the foriminifer fauna living in each category;5° to establish the important role played by the substratum, not only because of its nature, but also because of the biocenose it is linked to.
L'étude des Foraminifères contenus dans les échantillons récoltes par le « President-Theodore-Tissier » au cours de sa campagne de 1948 a permis: 1° - d'établir la liste des genres et espèces vivant dans cette partie nord-orientale de l'Océan Atlantique; 2° de constater que certaines de ces formes ont une large distribution géographique mais que d'autres sont localisées dans ces régions. Parmi ces dernières on peut citer: Quinqueloculina angulata Quinqueloculina dunkerquiana Quinqueloculina lata Quinqueloculina quadrangularis Gaudryina rudis Nonionella turgida Bolivina pseudo-plicata Bolivina laevigata Discorbis globularis var. anglica Discorbis millettii Discorbis nitida 3° de préciser pour certaines espèces quelques points d'ordre systématique; 4° de classer les différentes stations suivant la nature du fond et de déterminer la composition de la faune des Foraminifères qui pullulent dans chacune des catégories; 5° de constater le rôle important joue par le substratum, non seulement par sa nature, mais aussi par la biocénose qui lui est étroitement liée. ATTENTION : Ce texte a été extrait du document par un processus automatique, non contrôlé, de reconnaissance optique de caractères (OCR). Il est donc susceptible de comporter des erreurs. En cas de doute, consultez le fichier PDF.
Revue des Travaux de l'Institut des Pêches Maritimes (0035-2276) (ISTPM), 1958-06 , Vol. 22 , N. 2 , P. 148-211

Droits : Ifremer
http://archimer.ifremer.fr/doc/1958/publication-4597.pdf
http://archimer.ifremer.fr/doc/00000/4597/

Éditeur(s) : Elsevier
Résumé : This study was carried out in shrimp ponds from New Caledonia, in order to determine the cause of the exceptional proportion of abnormal tests (FAI) (often >50%, sometimes >80%). FAI was positively correlated to the quantity of easily oxidized material (EOM) deposited on the bottom of the ponds and to the sediment oxygen demand, and negatively correlated to redox. These results suggest that a very high FAI is a potential indicator for great accumulations of native organic matter, leading to a high sediment oxygen demand. When studying ancient sediments in core samples, exceptional abundances of abnormal tests may indicate periods of high accumulation of EOM, and therefore of oxygen depletion. This finding should help in better management of aquaculture ponds, but should also allow new insight into the interpretation of sedimentary records, providing a useful proxy for paleoenvironmental reconstructions.
Marine Pollution Bulletin (0025-326X) (Elsevier), 2009-09 , Vol. 59 , N. 8-12 , P. 323-335

Droits : 2009 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/2009/publication-6955.pdf
DOI:10.1016/j.marpolbul.2009.08.012
http://archimer.ifremer.fr/doc/00000/6955/

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Diverse, abundant and usually well-preserved communities of skeletal organisms occur in the lower Pleistocene (Gelasian) siliciclastic deposits of the Greek island of Rhodes. Benthic foraminifers, molluscs and bryozoans have been studied in four measured and sampled sections located in the northern part of the island. Among these bottom-dwelling organisms, numerous extant taxa are good environmental indicators and, combined with field observations and sedimentological data, they provide information on the probable conditions in which they developed. The siliciclastic deposits of the Kritika Formation have been divided into 14 different bio- and lithofacies, which have been further grouped into four facies associations corresponding to four different environmental settings: (1) continental to fluviatile; (2) brackish-water (lagoonal/deltaic); (3) infralittoral (0–20 m); and (4) upper circalittoral (depths of 20–40 m, but also down to c. 50–60 m). Among the marine facies associations, several characteristic biocoenoses have been recognized: soft-bottoms (fine to coarse sands and gravels); seagrass meadows; biogenic calcareous crusts on drowned beachrock slabs; red algal rhodoliths; and bivalve shell beds. In the studied sections, 13 superimposed genetic sequences have been documented. The repetition of similar facies associations within each sequence suggests: (1) a possibly eustasy-controlled, cyclic sedimentation; (2) a general subsidence of Rhodes during the deposition of the studied facies associations; and (3) a mostly constant range of environmental conditions (i.e. sedimentation rates and temperature) throughout the Gelasian.
ISSN: 0016-7568

hal-01277829
https://hal.archives-ouvertes.fr/hal-01277829
DOI : 10.1017/S0016756815000230

Éditeur(s) : American Geophysical Union
Résumé : [1] A multiproxy integrated chronological framework, based on oxygen and carbon stable isotope stratigraphy, biostratigraphy (foraminifera and nannoplankton bioevents and foraminifer assemblage-based climate cyclicity), magnetostratigraphy, sapropel stratigraphy, and C-14 AMS radiometric dates, has been achieved for borehole PRAD1-2, collected in 185.5 m water depth in the central Adriatic. This work was carried out within the European Community project Profiles across Mediterranean Sedimentary Systems (PROMESS1). The 71.2 m long borehole spans a time interval between late MIS 11 and MIS 1 (the last 370 ka), showing a chronological resolution of 500 and 250 years per cm during interglacial and glacial intervals, respectively. At present, this record is the most expanded and continuous marine record available for the Adriatic Basin. Several orbital cycles can be recognized in the PRAD1-2 record: the 100 ka glacial-interglacial fluctuations and the 23 ka precession-related cycles, which in turn control the deposition of sapropel layers. An integrated analysis of short-term oscillations within the Last Glaciation interval (MIS 4-MIS 2) allowed the identification of the Adriatic signature of Dansgaard-Oeschger events, showing the potential to achieve a more refined chronostratigraphic framework for the top part of the PRAD1-2 record. Finally, the age model obtained by this study allowed the chronological integration of the main foraminifera bioevents detected in the borehole as well as of the volcanoclastic layers present in the upper part of the record. Despite its proximal location, PRAD1-2 presents a continuous record and shows the potential to be consistently correlated both with deep-sea and continental records in the Mediterranean region and beyond.
Geochemistry Geophysics Geosystems (1525-2027) (American Geophysical Union), 2008 , Vol. 9 , P. NIL_107-NIL_127

Droits : 2008 American Geophysical Union
http://archimer.ifremer.fr/doc/2008/publication-3605.pdf
DOI:10.1029/2007GC001713
http://archimer.ifremer.fr/doc/00000/3605/

Éditeur(s) : Elsevier
Résumé : In situ microbialites occurring in reef rocks dredged between 80 and 130 in water depth on the modern fore-reef slopes of Tahiti and the Marquesas islands yield ages ranging from 17,100 2900 to 4410 2250 years BP, suggesting that they played a prominent role during the last deglacial sea level rise. Microbialites developed in both shallow and deep water depositional environments where they characterize various zones of the reef tracts (reef crests, upper reef slopes, deep fore-reef slopes), reflecting contrasting scenarios of microbialite development involving ''reefal microbialites'' in shallow-water settings and ''slope microbialites'' that formed in environments deeper than 1020 in and extending down to more than 100 m. Reefal microbialites correspond to a late stage of encrustation of the dead parts of coral colonies, or more commonly, of related encrusting organisms (red algae and foraminifers), thus forming surface crusts. Slope microbialites generally form the ultimate stage of a biological succession indicating a deepening sequence, whereby shallow water corals and associated encrusting organisms are replaced by deeper water assemblages of red algae and foraminifers before microbialite growth. The precipitation of phosphatic-iron-manganese crusts and the deposition of planktonic micritic limestones on the microbialites characterize a deepening-upward sequence. The widespread development of microbialites in reef sequences from the Last Deglaciation characterizes a period of environmental degradation consequential oil the rapid sea-level rise and abrupt climatic changes of that time. The reported biological succession reflects changes in water quality, and especially an increase in nutrients. In shallow-water settings, increased alkalinity and nutrient availability in interstitial waters were related to surface fluxes and terrestrial groundwater seepage while slope environments were exposed to continuous upwelling of nutrient-rich deeper waters during the last deglacial sea level rise. The age differences between corals and overlying slope microbialites range from 1600 to 8400 years, based on high-precision U-series age measurements of both corals and microbialites, and indicates that a significant time (several thousand years) elapsed between the development of the coralgal frameworks and the growth of slope microbialite crusts. Microbialites cannot be considered as part of the drowning event some 14,000 years ago that resulted in the demise of reef frameworks in the 90-110 m present depth range, but are Substantially younger. (c) 2006 Elsevier B.V. All rights reserved.
Sedimentary Geology (0037-0738) (Elsevier), 2006-03 , Vol. 185 , N. 3-4 , P. 277-295

Droits : 2006 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2006/publication-4204.pdf
DOI:10.1016/j.sedgeo.2005.12.018
http://archimer.ifremer.fr/doc/00000/4204/

Éditeur(s) : HAL CCSD Elsevier
Résumé : An integrated magneto-biostratigraphic study, based on calcareous nannofossils and foraminifers, together with the radiometric dating of a volcaniclastic layer found in several outcrops, was carried out on the hemipelagic deposits of the Lindos Bay Formation (LBF) at six localities on the island of Rhodes (Greece). Our highly refined chronostratigraphic framework indicates that the lower and upper lithostratigraphic boundaries of the LBF are diachronous. Associated with the 40Ar/39Ar age determination of 1.85 ± 0.08 Ma for the volcaniclastic layer, our data show that among the investigated outcrops, the Lindos Bay type locality section provides the longest record (1.1 Ma) of the LBF. Hemipelagic deposition occurred continuously from the late Gelasian (∼1.9 Ma) to the late Calabrian (∼0.8 Ma), i.e., from Chrons C2n (Olduvai) to C1r.1r (Matuyama) and from nannofossil Zones CNPL7 to CNPL10. This long record, together with the hemipelagic nature of the deposits, make the Lindos Bay type locality section a unique element in the eastern Mediterranean region, allowing future comparisons with other early Quaternary deep-sea sections available in the central and western Mediterranean regions.
ISSN: 0033-5894

hal-01467764
https://hal.archives-ouvertes.fr/hal-01467764
DOI : 10.1016/j.yqres.2016.05.002

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : In the western Mediterranean Sea, the Liguro-Provençal Basin (LPB) is a key area for studying passive margins because of its recent formation and abundance of onshore and offshore data. The Nerthe area located in the northern margin of LPB provides the unique continuous Oligo-Miocene deposits contemporaneous of the transition rifting to drifting. However, the age of the deposits remains debated and the link between outcrops and offshore seismic data is poorly constrained. The purpose of this paper is double. First, we intend to propose a new chronostratigraphic frame based on bio- (planktonic foraminifera, calcareous nannofossils) and magneto-stratigraphy. Second, we aim to make, through the integration of new highly time-resolved seismic data and field works, a coherent onshore-offshore link concretized by a 3D geological model. The new temporal and spatial data presented in this paper allow correlating the Oligo-Miocene sequences, defining their geometry and specifying precisely the timing of syn- and post-rift stages. The first marine transgression is now precisely dated latest Chattian within the syn-rift deposits and appears to be synchronous with the first marine deposits in the offshore wells and other marginal basins. The transition from syn-rift to post-rift appears to last 3.3 Ma at maximum, between 21.8 and 18.5 Ma (late Aquitanian to early Burdigalian). It is underlined by two major erosional unconformities bearing a hiatus of around 1 Ma. The post-rift started with a major marine transgression that is now dated from middle Burdigalian, at around 18.5 Ma, as elsewhere in the LPB. Contrarily to recent proposals, the post-rift deposits are widely represented on the northeastern margin of the "Golfe du Lion". There, the subsidence of the margin was low during the syn-rift and the transitional periods and high during the post-rift. The onset of this high post-rift subsidence appears to be synchronous with the slowdown of the Corsica-Sardinia block (CSb) motion.
EISSN: 1777-5817

hal-00558497
https://hal.archives-ouvertes.fr/hal-00558497
DOI : 10.2113/gssgfbull.181.6.591

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : The Latest Cretaceous/Paleocene paleokarsts from Bas-Languedoc (South of France) are characterized by : 1) exokarstic paleosurfaces (sink holes, pinnacles, canyons) which are mostly superimposed onto the Late Jurassic limestones and partly filled up with breccias and sandy clays containing Paleocene planktonic foraminifera; 2) endokarstic cavities filled up by sandy pelites and laminated mudstones with similar micropaleontological assemblage. All these cavities constitute three cut-and-filled paleokarstic systems. A general model of formation for this polyphase system is proposed. These paleosurfaces are generated by a Latest Cretaceous tectonic phase and Paleocene movements associated with eustatic rises inducing rapid floodings. During Upper Danian-Lower Selandian times three successive base levels drops, whose cumulated duration could be as long as 3 Ma, have induced several hundred metres of incisions within the exposed Jurassic carbonate series. A paleogeographic reconstruction shows three main marine gulfs which extend towards NE the EW Pyrenean thrust belt ("Pyrenean Paleocene Trough", PPT) located on the axis of the future Pyrenees. The similarity of the facies and micropaleontological content in the two domains suggests connexions between the marine Paleocene deposits of Bas-Languedoc and the PPT. It could thus explain the succession of the same tectono-eustatic events. We propose, as an hypothesis, that the rapid sea-level changes, as recorded by the imbricated karstic paleomorphologies, could be induced by the closing and the opening of a strait in the Eastern part of the PPT acting as a sill. This would be controlled by tectonic movements along the active orogenic axis of the Pyrenean Range and eustatic variations of the Paleocene World Ocean. The karstic systems developed during these low-stand episodes may have been later reactivated after the Early Selandian and more specifically during the Messinian desiccation event. This late evolution may have generated deep flooded karsts, now situated below the present sea level. Such karsts, partly inherited from Paleocene, could be important aquifers of economic interest.
ISSN: 0985-3111

hal-00407601
https://hal.archives-ouvertes.fr/hal-00407601
DOI : 10.3166/ga.20.301-326

Éditeur(s) : HAL CCSD
Résumé : National audience
se sont accrétés au cours du Mésozoïque. Ainsi, la collisionentre les blocs Indochine et Chine du Sud a engendré l’orogénèseIndosinienne. Durant la première moitié du XXè siècle, cet orogènea été défini et documenté à partir d’une discordance, dite Indosinienne,mise en évidence dans le Nord du Vietnam. Les études alorsréalisées ont permis d’estimer un âge antérieur au Jurassique inférieurpour cette discordance, qui n’a depuis pas fait l’objet deréévaluation. Outre la discordance Indosinienne, de nombreux débatsportent sur l’âge de la collision, la vergence de la subductionocéanique qui l’a précédée ou encore l’existence d’un véritable domaineocéanique ayant séparé l’Indochine de la Chine du Sud.Les bassins permo-triasiques du Nord du Vietnam (bassins deSam Nua et de Song Da), situés de part et d’autre de la sutureophiolitique de Song Ma, constituent, via le flux sédimentaireprovenant de l’érosion et du volcanisme des zones adjacentes, desarchives essentielles pour documenter l’évolution tectonique ducouple Indochine-Chine du Sud. A partir de données sédimentologiques,géochronologiques (datation U-Pb sur zircons) et biostratigraphiques(foraminifères), nous proposons une réévaluationdu cadre stratigraphique du Nord du Vietnam. Ces données nouspermettent d’envisager un âge postérieur au Trias moyen pour ladiscordance Indosinienne. A l’aide de données géochimiques et del’analyse du remplissage sédimentaire et volcanique des bassins,il est possible de documenter un volcanisme d’arc, actif au Triasinférieur. La position de cet arc par rapport aux limites des blocsIndochine et Chine du Sud, marquée par la suture ophiolitique deSong Ma, implique (i) une zone de subduction qui plongeait vers leSud (coordonnées actuelles), sous le bloc Indochine, en marge (ii)d’un véritable domaine océanique, et non pas d’une croûte continentaleamincie, séparant les deux blocs jusqu’au Trias moyen.Nos interprétations, issues de l’analyse des bassins sédimentairespermo-triasiques du Nord Vietnam, permettent également de reconstituerl’évolution de l’orogénèse Indosinienne. Celle-ci faitsuite à la subduction de la croûte océanique rattachée à une plaqueChine du Sud sous une plaque Indochine au Trias inférieur (etprobablement au moins depuis le Permien inférieur). A partir dela fin du Trias moyen, les blocs Indochine et Chine du Sud entrenten collision et forment l’orogène Indosinienne.
RST 2016, livre des résumés
Caen, France

insu-01388676
https://hal-insu.archives-ouvertes.fr/insu-01388676

Éditeur(s) : ISTPM
Résumé : A micropaleontological study of sediment sampling on the French Guiana coast showed the occurrence of an important fauna of actual planktonic and benthic Foraminifera.
Revue des Travaux de l'Institut des Pêches Maritimes (0035-2276) (ISTPM), 1977-12 , Vol. 41 , N. 4 , P. 403-416

Droits : Ifremer
http://archimer.ifremer.fr/doc/1977/publication-1992.pdf
http://archimer.ifremer.fr/doc/00000/1992/

Éditeur(s) : Springer
Résumé : Large benthic foraminifers are considered to be good indicators of shallow marine carbonate environments in fossil series. Over the last 50 years, the palaeoenvironment of Tertiary Nummulites accumulations has been a matter of debate, particularly because of difficulties in interpreting these deposits, and in this way, the absence of analogues in present-day seas does not help. The aim of this paper is to insight the different ways Nummulites tests and clasts may accumulate according to their hydrodynamic behaviour. Based on experimental measurements and on SEM observations, it appears that the high primary skeletal porosity of Nummulites made them easily transportable. The calculated threshold shear velocities confirm that large-sized Nummulites can be moved by weak wave-driven currents. This peculiar hydrodynamic behaviour of Nummulites could explain the diversity of depositional models. Depending on local hydrodynamic conditions, autochthonous Nummulites deposits can be preserved as in situ winnowed bioaccumulations or be accumulated offshore, onshore or alongshore, away from the original biotope.
Facies (0172-9179) (Springer), 2006-05 , Vol. 52 , N. 2 , P. 221-235

Droits : Springer-Verlag 2005
http://archimer.ifremer.fr/doc/00085/19597/17234.pdf
DOI:10.1007/s10347-005-0035-z
http://archimer.ifremer.fr/doc/00085/19597/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The marine Messinian deposits of Tunisia cover a narrow littoral strip some 300 km long between the northern Bizerte and Cap Bon areas and the central-eastern Sahel region. Litho- and biofacies analysis of six stratigraphic sections reveals the distinctive features of these deposits.;The lower Messinian deposits are characterized by ubiquitous siliciclastics and abundant oolitic/bioclastic limestones organized in an eastward facing ramp. Westward (landward), this ramp changes into coastal lagoons, sometimes containing evaporites. Eastward, the ramp passes to the reefal Pelagian Platform extending as far as Lampedusa.;Two main sedimentary cycles are distinguished: 1) an early Messinian siliciclastic retrogradational then oolitic/bioclastic progradational cycle (Beni Khiar Formation and lower Oued bel Khedim Formation): 2) a late Messinian brackish to continental cycle that probably accumulated in rapidly subsiding lagoons (Cued el Bir Formation and upper Oued bel Khedim Formation). The Tunisian early Messinian cycle is partly eustatically controlled, but the late Messinian cycle cannot be confidently correlated to other well-known Messinian series because of tectonic movements.;The lower Messinian deposits of Tunisia are also characterized by abundant suspension-feeding organisms (molluscs and bryozoans) and rare corals, calcareous algae, echinoids, and larger benthic foraminifers. The proposed palaeoenvironmental model shows that the lower Messinian ramp of Tunisia was located on a current-protected margin and subjected to continent-derived sediment and nutrient supply. Eastward, nutrient influx diminished and a shallow-water isolated carbonate platform with coralgal facies developed between the western and the eastern Mediterranean basins. The main hydrological connection between these two basins occurred through a narrow seaway situated to the northeast of the Pelagian Platform, south of Sicily and Malta.
ISSN: 0031-0182

hal-00475583
https://hal.archives-ouvertes.fr/hal-00475583
DOI : 10.1016/j.palaeo.2009.10.028

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The chronostratigraphy of the lower Miocene deposits of northwestern Sardinia is refined in the Castelsardo Basin. The combination of new 40Ar/39Ar isotopic datings, 19 micropalaeontological datings (calcareous nannofossils, planktonic and large benthic foraminifers) and 16 palaeomagnetic polarity measurements led to a new chronostratigraphic framework. The continental deposits of the first megasequence (Valledoria and Casteldoria members) are possibly Aquitanian. The overlying marine sediments are early Burdigalian (Vaginella depressa Molasse). The marine transgression can be dated to around 19.7 Ma. Marine conditions ceased 18.83 ± 0.13 Ma, the age of the index aerial τ2 ignimbrite. The continental part of the second megasequence (“Lacustre” unit) is early–middle Burdigalian, between 18.8 and 18 Ma. The overlying marine part (Campulandu and Sedini members) is middle–late Burdigalian. The second marine transgression began in the earliest–late Burdigalian, during the Chron C5Dr reversal, at the time of the eustatic Bur 4 event. The Castelsardo basin went through two main extensional tectonic episodes. The first one occurred as the Valledoria Member was deposited and possibly dates back to the Aquitanian. The second one occurred as the uppermost part of the Vaginella depressa Molasse was deposited during the early Burdigalian. The second extensional episode is related to a rapid rotation of Sardinia. Palaeomagnetic results confirm that Corsica and Sardinia acted as a single block which suffered a 28 ± 17° ccw rotation after 19.2 Ma. The Castelsardo basin is held to be an Aquitanian–early Burdigalian intra-arc rift basin that later evolved in a thermally controlled subsident margin of the Ligurian-Provençal Basin during the middle–late Burdigalian.
ISSN: 0031-0182

hal-00498288
https://hal.archives-ouvertes.fr/hal-00498288
DOI : 10.1016/j.palaeo.2010.06.007

Éditeur(s) : Elsevier Science Bv
Résumé : The timing, routing and processes of sediment transfer from the continents to the oceans at millennial time-scale are still largely unknown. The potential of turbidite systems (dominantly deposited during sea-level lowstands) to record global or regional environmental fluctuations is usually under-exploited because of the difficulty to obtain robust chronostratigraphic constraints in turbiditic deposits, and therefore to tie changes in sedimentary processes to environmental fluctuations. We were able to obtain a millennial-scale chronostratigraphy based on oxygen isotopes of the scarce foraminifera preserved in turbiditic deposits of the Rhone Turbidite System within the Western Mediterranean. Our results show that 1) objective criteria can be defined for the selection of foraminifera preserved within the pelagic intervals between the turbiditic sequences, in order to obtain a reliable isotope stratigraphy; 2) Turbidites triggered by hyperpycnal currents are described for the first time within the Rhone Turbidite System. They are related to the periods of direct fluvial connection with the canyon head (during the sea-level lowstand and early rise), and to a period of high sediment flux in relation with the massive recession of the Rhone glaciers in the Alps; 3) The lithofacies change passing from hyperpycnal to “Bouma-type” is dated at ca 19 cal. ka BP, which might correspond to an acceleration of sea-level rise (19-ka Meltwater Pulse,).
Sedimentary Geology (0037-0738) (Elsevier Science Bv), 2015-06 , Vol. 323 , P. 148-166

Droits : 2015 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00266/37712/35730.pdf
DOI:10.1016/j.sedgeo.2015.04.009
http://archimer.ifremer.fr/doc/00266/37712/

Éditeur(s) : HAL CCSD Blackwell Publishing
Résumé : International audience
The study of eight stratigraphic sections at the margin of the semi-enclosed Zsambek Basin (Hungary) allows the sedimentary anatomy of oolitic-bioclastic systems in the Sarmatian of the Central Paratethys to be reconstructed. The mollusc, foraminiferal and ostracod associations indicate that the carbonate systems are Latest Badenian to Late Sarmatian in age. The Lower-Upper Sarmatian deposits are organized in superimposed subaqueous dunes prograding towards the basin on a low-angle ramp. During the Late Sarmatian, the ramp underwent subaerial erosion linked to a moderate relative fall in sea-level. Lagoonal deposits were later formed and microbial-nubeculariid-bryozoan-serpulid buildups were emplaced. The 'abnormal' marine conditions of the Sarmatian, conducive to the development of a poorly diversified flora and fauna and dominant non-skeletal grains, are linked to fluctuating salinities, mesotrophic to eutrophic conditions and perhaps high alkalinity.
ISSN: 1469-3496

hal-00429337
https://hal.archives-ouvertes.fr/hal-00429337
DOI : 10.1111/j.1365-3091.2009.01055.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Cold seeps, located on sea floors and frequently fueled with methane, have been much studied for the formation of carbonate nodules, crusts or masses resulting from the activity og communities of anaerobic bacteria. In this paper, we examine the impact of cold seepage on their caging sediments, as far as their geochemical composition and microfaunal content are concerned. To this end, two fossil cold seeps of the Jurassic Beauvoisin site (Vocontian Trough, SE-France) are studied, focusing on the redox-sensitive and/or sulfide-forming trace metals. We observe that: 1) the carbonate edifices of the cold seeps are enriched in specific elements, namely, Sr, Mo As and Sb, compared to their caging marlstones, and 2) the benthic foraminifer populations were present close to the edifices. The Sr enrichment is ascribed to a contamination of the seeping fluids at the contact with underlying evaporites; the Mo-As-Sb enrichment may have several, non-exclusive, origins. We retain two scenarios; in the first one, the enrichment is due to the ascending fluids that could collect these elements when passing through thick shaly formations; in the second scenario, Mo, As and Sb were supplied to the sites of carbonate precipitation together with Fe- and Mn-oxy-hydroxides (the so-called particulate shuttle process). We favor the second scenario (possibly coupled to the first one) because the rather uncommon Mo-As-Sb association is also observed for reducing sediments deposited under the influence of Fe-Mn-shuttling.
ISSN: 0009-2541

hal-00806655
https://hal.archives-ouvertes.fr/hal-00806655
DOI : 10.1016/j.chemgeo.2012.12.012

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Multiproxy analyses were performed on core MS27PT recovered in hemipelagic sediments deposited on the Nile margin in order to reconstruct Nile River palaeohydrological fluctuations during the last 100,000 years. The strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source, oscillating between a dominant aeolian Saharan contribution during arid periods and a dominant Nile River contribution during pluvial periods. Iron content shows a strong correlation with strontium and neodymium isotopes. This allows the use of a high-resolution continuous Fe record as a proxy of Blue Nile sediment input over the last 100,000 years. The detailed Fe record, with approximately 10 years resolution during pluvial periods, is consistent with subtropical African records of well-dated lake level fluctuations and thus constitutes a first continuous high resolution record of the East African monsoon regime intensity over Ethiopia.;The detailed Fe record shows the two main known pluvial periods attributed to strengthening of the African monsoon over Ethiopia, the Nabtian period from 14 to 8 ka cal BP and the Saharan period from 98 to 72 ka BR For the first time, the last glacial period (Marine Isotope Stage (MIS) 2,3 and 4) is documented with a continuous record showing large oscillations between high and low East African palaeo-monsoon regimes.;The end of the Nabtian period occurred at 8 ka in core MS27PT, i.e. much earlier than on the East Equatorial African region where it ended around 5.5 ka. We interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the Eastern Ethiopian Highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka. During the last glacial period, two wet periods are present around 60-50 ka BP and 38-30 ka BP. These two humid periods are in phase with the rise of atmospheric CH4 concentrations suggesting that wetland tropical African area was one of the sources of the atmospheric CH4 during the MIS 3. During the Last Glacial Maximum and MIS 4, high Saharan aeolian influxes in phase with records of aeolian dust deposited in East Antarctica are documented. This study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low- and high-latitude climate variability at millennial timescales.
ISSN: 0277-3791

hal-00496481
https://hal.archives-ouvertes.fr/hal-00496481
DOI : 10.1016/j.quascirev.2010.02.006

Éditeur(s) : Gauthier-Villars
Résumé : Archaias angulatus is a soritid species found in abundance on littoral intertropical carbonate platforms. In the margino-littoral euryhaline biotopes, wedged in the neighbouring littoral marine environment, lives a distinct but similar form: Androsina lucasi. As the latter cannot migrate by sea or be transported by birds or fish, it cannot have been derived phylogenetically from an ancestral species before colonizing this wedged habitat in space and time. Only the idea of a reiterated phenomenon of speciation induced by the environment from another littoral species (Archaias angulatus) can explain its noticeable ubiquity in margino-littoral biotopes isolated from one another but each in contact with the biotopes favoured by Archaias angulatus. This interpretation is reinforced by morpho-structural, taxinomic, biological and ecological data concerning these two taxa.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1994 , Vol. 17 , N. 1 , P. 33-41

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00098/20895/18509.pdf
http://archimer.ifremer.fr/doc/00098/20895/

Éditeur(s) : Elsevier Science Bv
Résumé : For 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 epsilon(Nd) similar to-15.7 to -10.4. Evidence that the epsilon(Nd) 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 epsilon(Nd) 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. (C) 2011 Elsevier B.V. All rights reserved.
Earth And Planetary Science Letters (0012-821X) (Elsevier Science Bv), 2011-12 , Vol. 312 , N. 3-4 , P. 443-452

Droits : 2011 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00066/17754/15571.pdf
DOI:10.1016/j.epsl.2011.10.008
http://archimer.ifremer.fr/doc/00066/17754/

Éditeur(s) : Gauthier-Villars
Résumé : In the sedimentary areas surrounding the Florida Keys, Soritidae and Peneroplidae are very well represented. These benthic foraminifera are generally attached to seagrasses or algae and more rarely to carbonate deposits. The colouring of their protoplasm results from the nature of endosymbiotic algae. The principal species represented are: Androsina lucasi (never recorded before in Florida) which lives only in the margino-littoral biotopes where the salinity is highly variable; Archaias angulatus and Amphisorus hemprichii which live in the biotopes of the littoral platform but also in those of the interior margin of the bay where the variations of salinity are weak; Cyclorbiculina compressa and Peneroplis proteus which live for the main part in the littoral biotopes of the oceanic platform where the salinity is normal and quite constant; five other species of secondary importance take the number of taxa observed alive in the Keys area up to ten. Moreover, if the comparison of the biocenoses and thanatocenoses emphasizes their comparative similitude, knowledge of the biocenoses permits a better understanding of their adaptation to present-day environments.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 5 , P. 515-524

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00103/21379/18979.pdf
http://archimer.ifremer.fr/doc/00103/21379/