Sebastien Zaragosi

• Université Bordeaux-I

Two volcanic provinces have been recently discovered during the SISMAORE oceanographic cruise in the Comoros archipelago in the North Mozambique Channel between Madagascar and East Africa: N’Droundé, along the North‐eastern insular slopes of Grande Comores Island and Mwezi, in the abyssal plain, north‐east of Mayotte and Anjouan islands. By combini...

Geophysical and geological data from the North Mozambique Channel acquired during the 2020–2021 SISMAORE oceanographic cruise reveal a corridor of recent volcanic and tectonic features 200 km wide and 600 km long within and north of Comoros Archipelago. Here we identify and describe two major submarine tectono-volcanic fields: the N’Droundé provinc...

A multiproxy sedimentological study was conducted on five sediment cores retrieved between 67 and 79°N in the Greenland/Iceland/Norwegian seas in order to infer a common chronostratigraphic model for the selected cores. This model is based on the use of a series of geochemical, physical and micropaleontological proxies which are routinely measured...

The Mediterranean Sea is generally described as an oligotrophic area where primary productivity is limited to a few coastal environments with nutrient-enriched fluvial input. However, several studies have revealed that the hydrology of the western Mediterranean has major seasonal productive patterns linked either to significant riverine input or to...

Between the Last Glacial Maximum and the mid-Holocene, the Mediterranean Sea experienced major hydrological changes. The deposition of the last sapropel, S1, during the Early Holocene is a consequence of these changes. In order to cause anoxia in the Eastern Mediterranean Sea (EMS) bottom water, a long preconditioning period of a few thousand years...

Reconstructions of ocean primary productivity (PP) help to explain past and present biogeochemical cycles and climate changes in the oceans. We document PP variations over the last 50 kyr in a currently oligotrophic subtropical region, the Gulf of Cadiz. Data combine refined results from previous investigations on dinocyst assemblages, alkenones, a...

The physical, sedimentological, mineralogical and elemental geochemical properties of sediment cores AMD1803-02BC and 01PC from the Cape Norton Shaw Inlet were investigated to reconstruct glacial sediment discharges from southeastern Manson Icefield and document the impact of ice–ocean interactions on the sediment dynamics and opening of the North...

Since its existence, paleoceanography has relied on fossilized populations of planktonic foraminifera. Except for some extreme environments, this calcareous protist group composes most of the silty-to-sandy fraction of the marine sediments, i.e., the foraminiferal oozes, and its extraction is probably the simplest among the currently existing set o...

The upper branch of the Atlantic meridional overturning circulation (AMOC) plays a critical role in ocean circulation and climate change, yet its variability during the last glacial period is poorly documented. Here, we investigate the northward‐flowing Glacial Eastern Boundary Current (GEBC) in the North Atlantic, known today as the European Slope...

A detailed morpho-bathymetric study of the Comoros archipelago, based on mostly unpublished bathymetric data, provides a first glimpse into the submarine section of these islands. It offers a complete view of the distribution of volcanic structures around the archipelago, allowing to discuss the origin and evolution of this volcanism. Numerous volc...

Premiers essais de réalisation de lames minces. Présentation du protocole de réalisation, informations sur la perte de matière et premières images de lames minces.

Palynological analyses of 60 surface sediment samples from West Greenland margin revealed high concentrations of dinoflagellate cysts (dinocysts), particularly in the Disko Bugt area, where they reach >10⁴ cysts g⁻¹. Dinocyst assemblages are characterized by a relatively high species diversity and are dominated by Operculodinium centrocarpum, cysts...

We present a new version of the standardized Northern Hemisphere “modern” dinoflagellate cyst (“dinocyst”) database, which includes abundances of 71 taxa at 1968 sites across the Northern Hemisphere, cross-referenced with 17 environmental parameters extracted mostly from the 2013 World Ocean Atlas. Several taxa with tropical to warm temperate affin...

Sediment cores from the Mediterranean Sea have evidenced several periods of Sapropel deposition, which can be explained by events of anoxic bottom conditions. An explanation for such events calls for a very stratified sea, possibly related with freshwater input through increased precipitations and runoff discharges. It has been suggested that such...

The Arabian Sea is affected by an extremely dynamical climate system characterized by a pronounced seasonal monsoonal atmospheric circulation associated to changes in ocean circulation. Seasonal reversals and intensity changes of wind systems drive the development/suppression of strong coastal upwellings. High surface productivity, linked to upwell...

The seafloor of the Bay of Bengal is covered by thick sediment deposits that constitute the largest turbiditic system in the world. This system is fed primarily by the Ganges and Brahmaputra rivers, which drain the high Himalayan ranges. Sediment transfers from the delta to the deep-sea fan take place as turbidity currents in channel-levee systems....

In marine sediments of late Cenozoic age, Spiniferites is a very common genus of dinoflagellate cysts (dinocysts). Despite some taxonomical ambiguities due to large range of morphological variations within given species and convergent morphologies between different species, the establishment of an operational taxonomy permitted to develop a standar...

La version numérique est disponible ici : https://www.terres-du-passe.com/page-123-reunion-des-sciences-de-la-terre-2018.htm Le détroit de Fram est la seule connexion directe actuelle entre les eaux chaudes et salées de l’Atlantique Nord et les eaux froides et plus douces de l’Arctique. Le courant atlantique remonte par l’est, le long de la marge...

Lille. France

Lille, France

Living (stained) benthic foraminifera were investigated in surface sediments from the western Barents Sea, a subarctic environment strongly impacted by climate warming. In this area, the warmer Atlantic water largely influences intensity and seasonality of the primary productivity and therefore affects the benthic life. Six surface sediment cores w...

In the Ionian Sea, the subduction of the Nubia plate underneath the Eurasia plate leads to an important sediment remobilisation on the Calabrian Arc and the Mediterranean Ridge. These events are often associated with earthquakes and tsunamis. In this study, we analyse gravity-driven deposits in order to establish their recurrence time on the Calabr...

Toulouse, France

Toulouse, France

The last glacial millennial Heinrich and Dansgaard–Oeschger events have been the subject of many studies in recent decades. However, significant uncertainties remain, notably regarding associated oceanic mechanisms. Here we investigate the evolution of hydrographical conditions in the 3–41 ka cal BP interval of core MD99-2285 located in the souther...

Mineralogical and geochemical analyses conducted on cores located on the active channel-levee system of the northern Bengal Fan are used to establish changes in the weathering pattern and the sediment transport of the Himalayan system, and evaluate the effect of Indian summer monsoon rainfall during the Holocene. Our data indicate that during the H...

This paper documents the evolution over the last 10 kyr of one of the key parameters of climate: sea-surface temperatures (SSTs) in the North Atlantic. We focus on the southern Bay of Biscay, a highly sensitive oceanographic area regarding the dynamics of the North Atlantic subpolar and subtropical gyres (SPG and STG respectively). This site furthe...

The detailed morphology and internal structure of the Calabrian accretionary wedge and adjacent Eastern Sicily margin are imaged in unprecedented detail by a combined dataset of multi-beam bathymetry and high-resolution seismic profiles. The bathymetric data represent the results of 6 recent marine geophysical surveys since 2010 as well as a compil...

The relationships between oceanic circulation in the Arabian Sea and Late Cenozoic climate changes, including variations in monsoon intensity at the million year time-scale, remain poorly investigated. Using multibeam and seismic data, we provide the first description of a contourite drift in the Arabian Sea, along the south-eastern Oman margin. Th...

The eastern levee of the Active Channel in the Bengal fan has been investigated in order to better understand the history of turbidite activity in this channel during the Holocene in the context of Ganges-Brahmaputra ‘source-to-sink’ system. A robust ¹⁴C-based chronostratigraphy provides high temporal resolution for reconstructing sediment accumula...

The north Ecuador/south Colombia convergent margin is affected by recurrent subduction earthquakes with magnitudes > 7.5, like the 1906, 1942, 1958, 1979 and 2016 events. The subduction trench is characterized by the construction of the Esmeraldas Turbidite System (ETS) fed by the large Esmeraldas Canyon that deeply incises the continental slope an...

Turbiditic events are mostly avoided in paleomagnetic studies and therefore their remanence and magnetic properties are poorly described. Turbidites are exempt of bioturbation and potentially provide pertinent information about depositional remanence. We studied four quaternary turbidites of different origins in marine sediment cores. Upward fining...

This paper documents the last 10 ka evolution of one of the key parameters of climate: sea-surface temperatures (SST) in the subpolar North Atlantic. We focus on the southern Bay of Biscay, a highly sensitive oceanographic area because of its strategic and nodal position regarding the dynamics of the North Atlantic subpolar and subtropical gyres. T...

Bordeaux, France.

Bordeaux, France.

The Ionian Sea, due to the presence of two accretionary prisms, the Calabrian Arc and the Mediterranean Ridge, associated with the subduction of the Nubia plate and the Eurasia plate, is the witness of large and catastrophic turbidite events. These events are associated with high magnitude earthquakes and tsunamis. They lead an important gravity-dr...

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard–Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses...

Les études antérieures portant sur les systèmes turbiditiques du golfe de Gascogne (systèmes Celtique, Armoricain et du Cap-Ferret) n’ont jamais permis d’atteindre leurs parties terminales (Bourillet et al., 2006) et ce uniquement en raison de l’absence de levés dans ces zones. Afin de connaitre leurs extensions réelles nous avons compilé des donné...

La mer Ionienne, de par la présence de deux prismes d’accrétions (arc calabrais et ride méditerranéenne) liés à la subduction de la plaque nubienne sous la plaque eurasienne, est le témoin de grands évènements turbiditiques, parfois appelés homogénites. Ces évènements sont associés à des séismes de magnitude supérieure à 7 ainsi qu’à des tsunamis....

Pontarlier, France.

The amplitude and shape of the reverberated signal are significantly modified by the nature of the seabed. The acoustic methods of sediment characterization used in sedimentology (acoustic imagery, seismic profiles) and the acoustic systems used in marine physics are both based on similar systems, the main difference being the emission incidence an...

The direct comparison between marine and terrestrial data from the NW Iberian margin, core MD03-2697, allows us to accurately evaluate, without chronological ambiguity, the vegetation response to North Atlantic climate events across the last deglaciation. Comparison of MD03-2697 data with other marine and terrestrial records from a vast area stretc...

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich Events and Dansgaard–Oeschger cycles. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high resolution a...

Brest, France.

Brest, France.

The core MD03-2693 (43 degrees 39.258N; 01 degrees 39.805W; 431m water depth) was collected on an abandoned meander of the Capbreton Canyon (SE Bay of Biscay), filled over the last millennia by very high sedimentation rates (mean sedimentation rate of 1.2cm/yr) linked to its specific environmental location and fine-grained clayed sediment decantati...

Le canyon de Capbreton se singularise des autres canyons du Golfe de Gascogne par sa proximité à la côte. La tête du canyon s’initie dès 30 mètres d’eau et donne naissance à un thalweg sinueux encaissé dans un canyon étroit aux flancs raides. Le thalweg de Capbreton s’étend sur plus de 270 km jusqu’à 3 000 mètres de profondeur où il connaît un brus...

24e Réunion des Sciences de la Terre

The Dalrymple Trough is a 150-km-long, 30-km-wide basin located at the northern termination of the Owen Fracture Zone (OFZ), which is the present-day active India-Arabia plate boundary. The Dalrymple Trough is closely associated with the Murray Ridge, a complex of prominent bathymetric highs located on its eastern flank. Recent multibeam mapping of...

Benthic foraminiferal thanatocoenoses from the Cap-Ferret Canyon area were studied in the >150-µm fraction of 4–5 cm deep sediment levels, at 13 stations. The shallowest station (151 m depth) is located at the shelf break, close to the canyon head. All other stations are located along two bathymetric transects: seven stations along the canyon axis...

From Bordeaux, France.

The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have generally suggested a dominant northern hemispheric (NH) control on summer monsoon...

Facies associations in cores collected in the deep part of the Gulf of Cadiz, which is under the influence of the lower branch of the Mediterranean Outflow Water, are investigated in terms of the classical contourite model using grain-size analyses and thin sections of indurated sediment. Cores include both low-energy (contourite drift) and high-en...

The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several coun-tries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have suggested a dominant north hemispheric (NH) control on sum-5 mer monsoon dynamics...

The study of the post-rift sediment architecture and continental slope morphology leads to a reconstruction of the initial stages of formation and evolution of gravity-driven processes on the northern margin of the eastern Gulf of Aden. The slope-related features and associated deposits in the deep basin along this young passive margin are investig...

The study of sedimentary processes across a young and segmented passive margin under the influence of the Asian monsoon-climate, provide a potential record of tectonic, climatic and high-resolution eustatic events. The northern margin of the eastern Gulf of Aden is one of the world rare examples to study the setting up of gravity sedimentation in a...

The last glacial period, showing the progressive development of large boreal ice sheets, was punctuated by large climatic excursions. These excursions were triggered mainly by atmosphere–ocean–ice coupled dynamics and are thus exemplary case studies of natural climate variability. To characterize the sea-surface palaeohydrographical changes accompa...

The Indus sedimentary basin forms one of the largest “source-to-sink” systems of the Quaternary and extends over 106 km2 offshore. It is characterized by a complex tectonic setting marked by the Himalayan active orogenic belt in the source area, and the active strike-slip India-Arabia plate boundary (Owen Fracture Zone; OFZ) in its distal reaches....

Capbreton Canyon extends from 200 m water depth near the Aquitanian coast to 3000 m water depth before abruptly turning northward and merging with the Cap-Ferret systems. The Capbreton Canyon has been disconnected from the Adour River input since 1310 AD. Despite this situation, modern sedimentary activity is evident in the first kilometres from th...

The rapid climatic variability characterising the Marine Isotopic Stage (MIS) 3 (~60–30 cal ka BP) provides key issues to understand the atmosphere–ocean–cryosphere dynamics. Here we investigate the response of sea-surface paleoenvironments to the MIS3 climatic variability through the study of a high resolution oceanic sedimentological archive (cor...

La communauté scientifique a porté un très grand intérêt envers les évènements d’Heinrich ces dernières années. Cependant, et ce malgré un nombre très important de publications, aucun de ces travaux ne présente une résolution d’analyse véritablement haute définition des niveaux d’Heinrich (Heinrich Layer, HL) dans l’Atlantique Nord. Pourtant, l’app...

The Owen Ridge is a prominent relief that runs parallel to the coast of Oman in the NW Indian Ocean and is closely linked to the Owen Fracture Zone, an 800-km-long active fault system that accommodates today the Arabia–India strike–slip motion. Several types of mass failures mobilizing the pelagic cover have been mapped in details along the ridge u...

During the late Quaternary, both external and internal forcings have driven major climatic shifts from glacial to interglacial conditions. Nonlinear climatic steps characterized the transitions leading to these extrema, with intermediate excursions particularly well expressed in the dynamics of the Northern Hemisphere cryosphere. Here we document t...

The rapid climatic variability characterising the Marine Isotopic Stage (MIS) 3 (~ 60-30 CAL-ka BP) provides key issues to understand the atmosphere-ocean-cryosphere dynamics. Here we investigate the response of sea-surface paleoenvironments to the MIS3 climatic variability through the study of a high resolution oceanic sedimentological archive (co...

The depositional architecture across a stretched and segmented margin is composed of several turbidite systems and mass-transport deposits, which constitute the record of tectonic, climate and high-resolution eustatic events. The characterisation of turbidite system architecture is a main challenge in order to clarify which of these parameters cont...

Sequence stratigraphic models predict increased sediment delivery to deep-water areas during sea-level lowstand. The Armorican margin (Bay of Biscay, western European margin) is an interesting area to test this hypothesis because the margin has a wide continental shelf, still partly flooded during sea-level lowstand, and the Armorican turbidite sys...

Present sedimentation in three canyons of the Bay of Biscay (Audierne, Blackmud and Capbreton) is studied by the combined analysis of cores and current meter data collected over a 7 month period. At the current meter mooring locations, interface cores were collected to characterize the recent sedimentation processes. In the two canyons located in t...

This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of glaciers, sea ice and deep water formation at Milankovit...

During the late Quaternary, both external and internal forcings have driven major climatic shifts from glacial to interglacial conditions. Nonlinear climatic steps characterized the transitions leading to these extrema, with intermediate excursions particularly well xpressed in the dynamics of the Northern Hemisphere cryosphere. Here we document th...

The Owen Fracture Zone is a 800 km-long fault system that accommodates the dextral strike-slip motion between India and Arabia plates. Because of slow pelagic sedimentation rates that preserve the seafloor expression of the fault since the Early Pliocene, the fault is clearly observed on bathymetric data. It is made up of a series of fault segments...

Editor: P. DeMenocal Keywords: summer/winter monsoon productivity Arabian Sea timing precession obliquity A recent study suggested that Indian monsoonal proxies commonly used in the Arabian Sea, in general productivity proxies, could be impacted by changes in the Atlantic overturning rate (AMOC) throughout a control on the nutrient delivery into th...

Chronologies of sediments that document the last glacial history of the Black Sea “Lake” are hampered by issues relating to reservoir age. Regulated by basin hydrology, reservoir ages represent a tool that could potentially be used to better understand the response of Black Sea “Lake” hydrology to climate change. Therefore, deciphering reservoir ag...

This study focuses on the exceptionally high occurrence of Orbulina suturalis and morphotypes very close to Praeorbulina in Late Glacial sediments from the Northern Arabian Sea. The genus Praeorbulina has been described by Blow (1956) as an ancestor of Orbulina universa. Our study is based on the analysis of three sediment cores retrieved in the Gu...

Abstract This study investigates the morphology and Late Quaternary sediment distribution of the Makran turbidite system (Makran subduction zone, north-west Indian Ocean) from a nearly complete subsurface mapping of the Oman basin, two-dimensional seismic and a large set of coring data in order to characterize turbidite system architecture across a...

We surveyed the Owen Fracture Zone at the boundary between the Arabia and India plates in the NW Indian Ocean using a high-resolution multibeam echo-sounder (Owen cruise, 2009) for search of active faults. Bathymetric data reveal a previously unrecognized submarine fault scarp system running for over 800 km between the Sheba Ridge in the Gulf of Ad...

In this paper, we investigate the ecology of live (rose Bengal stained) benthic foraminifera collected at 20 stations ranging from 15 to 100 m depth in the Rhône prodelta (Gulf of Lions, NW Mediterranean). These sites were sampled in September 2006, five months after the Rhône River annual flood. Statistical analyses based on foraminiferal communit...

The main sediment depocenter along the Oman margin is the Al Batha turbidite system that develops in the Gulf of Oman basin. It is directly connected to the wadi Al Batha, and forms a typical sand and mud rich point source system that acts as regional sediment conduit and feeds a ~ 1000 km2 sandy lobe.The Al Batha lobe depositional architecture has...

Late Quaternary turbidite system growth along the Makran convergent margin is investigated through a set of deep-sea cores from upper slope and piggy-back basins to deep basin plain settings. High-resolution stratigraphy in these various depositional environments permits reconstruction of the evolution of sand-to-mud ratio, sedimentation rates, fre...

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 fr...

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 cha...

The Fleuve Manche (English Channel) palaeoriver represents the largest river system that drained the European continent during Pleistocene lowstands, particularly during the Elsterian (Marine Isotope Stage 12) and Saalian Drenthe (MIS 6) glaciations when extensive ice advances into the North Sea area forced the central European rivers to flow south...