Laurent Londeix

University of Bordeaux · Earth Sciences and Environment

The Messinian salinity crisis and its precursor events have been the greatest environmental perturbation of the Mediterranean Sea to date, offering an opportunity to study the response of marine ecosystems to extreme hydrological change and a large-scale biological invasion. The restriction of the marine connection between the Mediterranean and the...

Understanding deep-time marine biodiversity change under the combined effects of climate and connectivity changes is fundamental for predicting the impacts of modern climate change in semi-enclosed seas. We quantify the Late Miocene-Early Pliocene [11.63 to 3.6 million years (Ma)] taxonomic diversity of the Mediterranean Sea for calcareous nannopla...

Massive salt accumulations, or salt giants, have formed in highly restricted marine basins throughout geological history, but their impact on biodiversity has been only patchily studied. The salt giant in the Mediterranean Sea formed as a result of the restriction of its gateway to the Atlantic during the Messinian Salinity Crisis (MSC) 5.97 to 5.3...

Understanding deep-time marine biodiversity change under the combined effects of climate and connectivity changes is fundamental for predicting the impacts of modern climate change in semi-enclosed seas. We quantify the Late Miocene–Early Pliocene (11.63–3.6 Ma) taxonomic diversity of the Mediterranean Sea for calcareous nannoplankton, dinocysts, f...

The Messinian Salinity Crisis and its precursor events have been the greatest environmental perturbation of the Mediterranean Sea to date, offering an opportunity to study the response of marine ecosystems to extreme hydrological change and a large-scale biological invasion. The restriction of the marine connection between the Mediterranean and the...

Nous poursuivons ici l’étude de l'échantillon BIL en présentant les résultats d’une analyse spectroscopique en rayons X (XRF) dont le but était de déterminer les principaux élément chimiques. C’est la première étape de notre travail visant à caractériser sa composition. Après un bref rappel de la technique XRF et de la présentation des conditions e...

Preliminary analysis of the Bristol Impact Layer (for large public)

Shallow-water reef-building corals have an extensive geological record and many aspects of their evolution, biodiversity, and biogeography are known in great details. In contrast, the adaptive potential and risk of extinction of coral reefs in response to excessive warming and ocean acidification remains largely undocumented. It is well established...

Organic-walled resting cysts of planktonic dinoflagellates occur commonly in modern marine sediment where they represent, with rare exceptions, the only geologically preservable part of the life cycle. Although many species do not produce fossilizable resting cysts, upper Quaternary sediments contain a diverse cyst record that is used frequently fo...

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...

Dans le cadre du stage de Master 1 de L. Saint George nous avons mesuré la densité de quatre météorites à partir de la méthode de la double pesée. Ces mesures nous ont permis de faire une première caractérisation de trois de ces météorites qui ne sont pas encore réfé-rencées. L'une d'elle notamment, qui a l'aspect d'une météorite lunaire, à effecti...

Dans le cadre d'un stage de Master 1 de physique, nous avons utilisé plusieurs techniques pour analyser la météorite lunaire NWA 5000. Les résultats que nous avons obtenus sont en bon accord avec des études antérieures de la même météorite (mais sur des échantillons différents). Ces travaux préliminaires nous ont permis de nous familiariser avec le...

Dans le cadre d'un stage de Master 1 de physique, nous avons utilisé plusieurs techniques d'analyse pour caractériser une météorite potentiellement lunaire NWA XXX (non référencée) ainsi qu'un échantillon de la météorite lunaire NWA 5000. Nous avons comparé les résultats que nous avons obtenus pour la météorite non référencée avec ceux de NWA 5000...

Dans le cadre d'un stage de Master 1 de physique, nous avons utilisé plusieurs techniques pour analyser une météorite non référencée qui s'avère, d'après l'ensemble de nos analyses, être très probablement une météorite chondritique de type CV3. En particulier, les analyses EDS montrent que la matrice et les chondres de la météorite sont composés d'...

Dans le cadre d'un stage de Master 1 de physique, nous avons utilisé plusieurs techniques pour analyser une chondrite ordinaire non référencée mais identifiée par un collectionneur comme une probable chondrite ordinaire de type LL. Les différentes analyses effectuées (me-sure de densité, de susceptibilité magnétique, analyses élémentaires en XRF et...

The use of dinoflagellate cyst assemblages as a tool for palaeo-environmental reconstructions strongly relies on the robustness of cyst identification and existing information on the distribution of the different species. To this purpose, we propose a functional key for the identification of Pliocene and Quaternary Spiniferites bearing intergonal p...

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...

In this article, we are proposing an Identification Key for recognition of Quaternary Spiniferites species and some morphologically close Quaternary taxa of some related genera. We summarize the morphological features of 43 taxa (including three subspecies and one variety) based on the original description of the holotypes and sometimes supplemente...

A new quantitative biostratigraphical method, based on an ‘index of stratigraphical abundance’ (ISA), has been used to refine the stratigraphical range of 50 dinoflagellate cyst taxa. Most of these correspond to Quaternary representatives of Achomosphaera or Spiniferites. Some extinct taxa are also discussed when their morphology is close to that o...

We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly desc...

Dansgaard–Oeschger and Heinrich events constitute ones of the most enigmatic features of the last glacial period. Many studies have focused on their characteristic millennial climatic variability, testing atmospheric/cryospheric/oceanic couplings, but major uncertainties and discrepancies still remain. Anew scenario, robustly supported by an approa...

https://halshs.archives-ouvertes.fr/halshs-02284487

The last glacial millennial climatic events (i.e. Dansgaard-Oeschger and Heinrich events) constitute outstanding case studies of coupled atmosphere-ocean-cryosphere interactions. Here, we investigate the evolution of sea-surface and subsurface conditions, in terms of temperature, salinity and sea ice cover, at very high-resolution (mean resolution...

IODP 339 Site U1385 ("Shackleton site", e.g. Hodell et al., 2013a), from the SW Iberianmargin, offers the opportunity to study marine microfossil population dynamics bycomparing several past interglacials and to test natural shifts of species that occurred acrossthese warm periods, in a subtropical context. Here, more specifically, we present resul...

We present and examine a multi-sensor global compilation of mid-Holocene (MH) sea surface temperatures (SST), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and ev...

Des événements anoxiques océaniques sont présents au cours du Crétacé et sont notamment caractérisés par le dépôt de black shales riches en matière organique (plusieurs % de COT) souvent propices à la formation d’une roche-mère pour les hydrocarbures. Ces événements se retrouvent de façon synchrone à l’échelle océanique, témoignage de leur impact g...

We present and examine a~multi-sensor global compilation of Mid-Holocene (MH) sea surface temperatures (SSTs), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and e...

Si c’est bien grâce à ses fossiles marins que l’Aquitaine a été choisie comme région éponyme de l’étage Aquitanien, il n’en reste pas moins vrai que ce vaste bassin sédimentaire recèle un grand nombre de gisements continentaux à partir desquels il est possible de se faire une idée des faunes terrestres contemporaines des faciès marins. Représentés,...

In order to document the distribution of organic-walled dinoflagellate cysts (dinocysts) and their relationship with sea-surface parameters (temperature, salinity, primary productivity), palynological analyses were performed on 44 surface sediment samples from the Gulf of Mexico (17°N to 29°N). Samples display low to moderate concentrations with va...

Dinoflagellate cysts are useful for reconstructing upper water conditions. For adequate reconstructions detailed information is required about the relationship between modern day environmental conditions and the geographic distribution of cysts in sediments. This Atlas summarises the modern global distribution of 71 organic-walled dinoflagellate cy...

Surface sediment samples (0-1 cm) from 44 sites of the Gulf of Mexico and adjacent lagoonal bodies were analyzed for their palynological content in order to document the relationship between organic-walled dinoflagellates cysts (dinocysts) and sea-surface conditions (temperature, salinity, productivity). The analyses also aimed at identifying trace...

Dinoflagellate cysts are useful for reconstructing upper water conditions. For adequate reconstructions detailed information is required about the relationship between modern day environmental conditions and the geographic distribution of cysts in sediments. This Atlas summarises the modern global distribution of 71 organicwalled dinoflagellate cys...

High-resolution pollen analysis of core MD01-2430 from the Sea of Marmara (40 • 47.81 N, 27 • 43.51 E) allows us to reconstruct the vegetation response to climatic changes during the past 23 cal ka in the Northeastern Mediterranean. Variation in mesic/temperate forest cover indicates major climatic shifts connected to Heinrich Sta-dial 1, Bölling-A...

Classically, no Miocene deposits are recorded in the Poitou-Charentes region (Central Western France). Previous authors suggested the existence of a hill forming a peninsula during high sea level periods (Aquitanian, Burdigalian, Langhian and Serravallian) in this area. This relief seems to be highly linked to the general Alpin orogen and the forma...

High-resolution pollen analysis of core MD01-2430 from the Sea of Marmara (40°47.81′ N, 27°43.51′ E) allows us to reconstruct the vegetation response to climatic changes during the past 23 cal ka in the Northeastern Mediterranean. Variation in mesic/temperate forest cover indicates major climatic shifts connected to Heinrich Stadial 1, Bölling-Alle...

The Messinian Salinity Crisis is well known to have resulted from a significant drop of the Mediterranean sea level. Considering both onshore and offshore observations, the subsequent reflooding is generally thought to have been very sudden. We present here offshore seismic evidence from the Gulf of Lions and re-visited onshore data from Italy and...

Using the analysis of dinoflagellate cysts in three deep-sea sediments cores situated in the Sicilian-Tunisian Strait, in the Gulf of Lions and in the Alboran Sea, we reconstruct the paleoenvironmental changes that took place during the last glacial-interglacial transition in the western Mediterranean Sea. The development of the warm microflora Imp...

Dinoflagellate cysts are useful for reconstructing upper water conditions. For adequate reconstructions detailed information is required about the relationship between modern day environmental conditions and the geographic distribution of cysts in sediments. This Atlas summarises the modern global distribution of 71 organicwalled dinoflagellate cys...

Export Date: 6 February 2013, Source: Scopus, Article in Press

Several methods of biostratigraphy, usable for the Aquitanian stage, are presented on the occasion of the revision of the stratotype described in the Northern Aquitaine Basin (MAYER, 1858). The paleontological markers reliable for this period belong generally to the microfossils of open oceanic environments. In the Aquitaine Basin, if littoral to c...

De nombreuses universités scientifiques possèdent des collections. L'université Bordeaux 1 possède neuf grandes collections concernant les domaines de la préhistoire, de l'anthropologie, de la géologie terrestre et marine, de la paléontologie et micropaléontologie, de la biologie, de l'astronomie et d'un fonds ancien et moderne d'ouvrages scientifi...

This paper evaluates the evidence for millennial-scale variability in pollen records of the last glacial (Marine Isotope Stages 4, 3, and 2; 73.5–14.7 calendar ka BP) from the European continent, taking into account information derived from long, continuous terrestrial records, the fragmentary northern European terrestrial record, and marine pollen...

A high resolution micropalaeontological study of the core MD 04-2797 CQ recovered in the Sicilian–Tunisian Strait provides insights into the paleoclimatic history of the Mediterranean Sea at the transition between the western and eastern basin over the last 30 ka. Using the analysis of dinoflagellate cyst and planktonic foraminiferal assemblages, w...

The history of the connection between the Mediterranean and Black seas since the Last Glacial Maximum (LGM) is documented through the study of an organic-walled dinoflagellate cysts (dinocysts) record at high temporal resolution from the Marmara Sea (MD01-2430 core). Late Glacial dinocyst assemblages indicate that the Marmara Sea was a mildly brack...

Direct correlation of terrestrial and marine climatic data for marine cores MD95-2043 (Alboran Sea, western Mediterranean) and MD01-2430 (Marmara Sea, eastern Mediterranean) provides evidence for millennial-scale climatic changes in western and eastern Mediterranean sectors during the Holocene. In the Alboran region, multi-centennial-scale oscillat...

Absolute abundances (concentrations) of dinoflagellate cysts are often determined through the addition of Lycopodium clavatum marker-grains as a spike to a sample before palynological processing. An inter-laboratory calibration exercise was set up in order to test the comparability of results obtained in different laboratories, each using its own p...

Absolute abundances (concentrations) of dinoflagellate cysts are often determined through the addition of Lycopodium clavatum marker-grains as a spike to a sample before palynological processing. An inter-laboratory calibration exercise was set up in order to test the comparability of results obtained in different laboratories, each using its own p...

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was dev...

A biometrical analysis of the dinoflagellate cyst Lingulodinium machaerophorum [Deflandre, G., Cookson, I.C., 1955. Fossil microplankton from Australia late Mesozoic and Tertiary sediments. Australian journal of Marine and Freshwater Research 6: 242–313.] Wall, 1967 in 144 globally distributed surface sediment samples revealed that the average proc...

Absolute abundances (concentrations) of dinoflagellate cysts are often determined through the addition of Lycopodium clavatum marker-grains as a spike to a sample before palynological processing. An inter-laboratory calibration exercise was set up in order to test the comparability of results obtained in different laboratories, each using its own p...

The historical stratotypes of the Aquitanian and Burdigalian in the Aquitaine Basin are studied here by using the tools of facies sedimentology and the concept of sequence stratigraphy. This analytical method combines recognition and sequential organization of facies, and several types of stratigraphic markers. This method allows identification of...

The recent discovery of emerged and lifted lagunal deposits near the Moulay Bouselham lagoon (North Moroccan Atlantic coast), up to 32 m above sea level, requires a new model to explain the evolution of this ecosystem. All the studies on these deposits seem to indicate that we are dealing with very recent lagoonal levels. The main problem is to exp...