Preface The book of abstracts, represents the works that will be presented at the 2d meeting of Ph.D students of the FRE Geosystèmes., held in Villeneuve d’Ascq at the SN5 building of the University of Lille 1, on 27th may 2011. The Ph.D students will present their works orally in mixed themes plenary sessions on friday 27th afternoon. The oral presentations will take place at the «Salle Pruvost» on the ground floor of the SN5 building. Students will have 15 min for each presentation followed by 5 min of questions. Posters are on view for the duration of the conference and the presenter will be available for discussion during the coffee brake of oral presentations (15h00). Abstracts are numbered from 1-11 with the prefix «P» for posters or «O» for oral. JDD 2011 Organizing Committee Melesio Quijada (SN5) Jean Philippe Ursule (SN5) Gaël Lymer (SN5) Program: 13h00-13h20 Charlotte Skonieczny The aeolian terrigenous signal on the West African margin: may present-day deposits help interpreting the sedimentary marine records? 13h20-13h40 Melesio Quijada Carbohydrate dynamics in Cariaco Basin pore water and sediments 13h40-14h00 Jose Margotta Holocene evolution of the french side of the flemish coastal plain 14h00-14h20 Jean-Philippe Ursule Sedimentation and structure of the Cangalli Formation, Bolivia 14h20-14h40 Mariam Hamzeh Trace metals mobilization from surficial sediments of the river Seine Estuary

14h40-15h00 Emilie Prygiel In situ measurement of dissolved phosphorus in aquatic media using diffusive gradients in thin-films 15h00-15h20 Coffee break-Poster sessions 15h20-15h40 Hélène Goubel Morphological affinities of cave bear dental elements among extant and fossil ursid populations: phylogenetic and ecological implications 15h40-16h00 Lauren Pouille A new Upper Ordovician (Uppermost Darriwilian to Lowermost Sandbian) Radiolarian assemblage from Kazakhstan: Insights to Ordovician Radiolarian biodiversity 16h00-16h20 Sébastien Maillet Ostracodes paleoecology and paleodiversity throughout the Middle Devonian in Ardennes. Comparison with a current carbonated platform 17h00

BBQ in front of the SN5

ABSTRACTS O.1- The aeolian terrigenous signal on the West African margin: may present-day deposits help interpreting the sedimentary marine records?

Skonieczny C.1, Bory A.1, Bout-Roumazeilles V.1, Abouchami W.2, Galer S.2, Malaizé B.3, Grousset F.3, Crosta X.3. FRE 3298 GEOSYSTEMES, Université Lille 1 Institut for Chemistry, Mainz (Allemagne) 3 UMR 5805 EPOC, Université Bordeaux 1 1

2 Max-Planck

The Sahara-Sahel region is the Earth’s most important source of mineral dust, which is mainly transported westward over the North-Eastern Tropical Atlantic Ocean. The study of aeolian terrigenous deposits in the marine sedimentary records enables to document changes in aridity and wind patterns, therefore contributing to reconstruct paleoclimatic scenarios in this region. We are, however, often unable to interpret these paleorecords to the fullest because of our incomplete understanding of the mineralogical and geochemical proxies. Present-day investigations may thus provide valuable clues in order to calibrate those proxies, particularly in terms of changes in source area and main transport systems. Within the frame of the African Multidisciplinary Monsoon Analyses (AMMA) program, a dust collector was deployed at Mbour, on the Atlantic coast of Senegal, early 2006 and has been operating since, providing a unique pluri-annual record of weekly dust deposits in that region. In a first part, we will present the preliminary results of a multi-proxy study, including deposition fluxes, grain size distribution, clay mineralogy, major and minor elements, Strontium and Neodymium isotopes and the fresh-water diatoms, of the dust deposited at Mbour during the 2006-2008 dry and humid seasons. In a second part, we will present results from sediment core MD03-2705, which was taken on a seamount ~500 km off the Mauritanian coast. Considering this particular environmental setting, it can be assumed that the terrigenous fraction in this record is largely of aeolian origin. In the light of the terrigenous signature of the present-day deposits, we will discuss grain size, clay mineralogy, major and minor elements, as well as Strontium and Neodymium isotopes of the carbonate-free fraction covering the last 25 ka. Comparison of our results with the recent geochemical study carried out on the neighboring site ODP658C should further our understanding of the dust proxies in the North-Eastern Tropical Atlantic sediments in terms of environmental changes in the Sahara-Sahel region during the last 25 ka.

O.2- Carbohydrate dynamics in Cariaco Basin pore water and sediments

Quijada M.1, Riboulleau A.1,Guerardel Y.2 1

FRE 3298 GEOSYSTEMES, Université Lille 1 8576 Unité de glycobiologie structurale et fonctionnelle, Université de Lille 1

2UMR

Carbohydrates are one of the major constituents of the biomass, and account for a substantial amount of the total organic carbon (TOC) in water and sediments in marine environments. It is often accepted that structural carbohydrates are rapidly re-mineralized during early diagenesis and do not make substantial contribution to total organic carbon in ancient sediments and kerogens. However some studies has shown that structural carbohydrates may escape decomposition and remineralization depending on different factors, such as paleo-productivity, presence of oxygen in water and sediments and sedimentation rate. Even more, some studies report that once particulate carbohydrates escape water column in non oxygenated environments, they may be preserved within the organic matrix. In our study we investigated the neutral carbohydrates (NCHO) variation in sediments from Cariaco Basin, covering a period of time of 135ky. 15 sediment samples were obtained from sediment cores 1002 D & E collected on the central saddle of the Cariaco Basin during the ODP Leg 165. The NCHO where determined quantitatively after (i) water extraction to explore pore water carbohydrates (PNCHO) and (ii) acid hydrolysis to investigate structural and sediment-attached monomers (HNCHO). Monosaccharides were analyzed by GC-FID and GC/MS after derivatization of aldoses to their corresponding alditol acetates. Nine monosaccharides were identified in the 15 samples. Deoxysugars (fucose and ribose) are apparently more susceptible to 2N TFA hydrolysis The contribution of deoxysugars to the organic carbon (focusing in rhamnose) is considered to be indicative for the presence of bacteria. Hexoses (galactose, manose, glucose) yielded mostly in the 4N hydrolysis. The large contribution of glucose is related with the presence of storage polysaccharides. Manose and galactose present a large contribution to the total NCHO budget, corresponding to structural sugars of microorganisms. Hexose to pentose ratio show the origin of sugars and its variation with depth. The (galactose + manose) / (arabinose + xylose) ratio>2 indicated an algae and zooplankton origin for NCHO during the all period studied. The nine sugars present a global decrease with depth with some variations induced by facies variability. Heterotrophic remineralization and preservation via natural sulfurization, may be the possible causes of the total NCHO decrease with depth.

O.3- Holocene evolution of the french side of the flemish coastal plain Margotta J.1, Trentesaux A.1, Tribovillard A.1 1

FRE 3298 GEOSYSTEMES, Université Lille 1

The French Flanders fields represent a coastal plain of approximately 750km2 situated along the North Sea in the northern part of France. The sedimentary records of Quaternary in this zone display a contrasting terrigenous and biogenic sediment alternations, caused by sea-level changes during the Quaternary. In this sense, a good knowledge of the stratigraphy of this area, based in well-founded correlations, is essential to understand the rythmicity, oscillations and implications of the deposits in these lowlands areas. To improve our understanding of the stratigraphic changes, and the geometry of the sedimentary bodies, we propose a research combining stratigraphy, sedimentology and radiometric dating data obtained from a high-resolution seismic survey, cores and surface samples. The main objective is to elucidate the 3D architecture of the French maritime area of Flanders fields. This abstract takes place at the early stage of research works. It shows the planned campaign of acquisition and discuss the methodology that is necessary to obtain the data that will be performed to reconstruct the depositional history of these lowlands during the Holocene. The complex evolution of this coastal zone requires a lot of data to be integrated. They are of multidisciplinary origin. The main planned campaign of acquisition objective is to get a detailed framework for the sedimentary bodies. It includes their spatial distribution, the lateral, and vertical variation of various facies. Previous studies in the north of Belgium (Baeteman, 2005) and western Netherlands (Cleveringa, 2000) show the implementation of high resolution seismic acquired in the navigable channels of the rivers, to identify the subsurface information. This technique together with the information from cores and samples of the surface will generate the 3D-architecture of the coastal plain and help for a better understanding of the changes that occurred during the Quaternary, their effects on the sedimentation and their main controls.

O.4- Sedimentation and structure of the Cangalli Formation, Bolivia

Ursule J.P.1,2, Trentesaux A.2,Bailleul J.3, Dubois M.4 REXMA SAS. 52 ZA Galmot. 97300 Cayenne FRE 3298 GEOSYSTEMES, Université Lille 1 3 Institut Polytechnique LaSalle, r. Pierre Waguet, BP 30313, 60026 Beauvais 4 Université Lille 1. EA4515 LGCgE. 59655 Villeneuve d’Ascq 1 1

The Cangalli Formation is a thick Tertiary glacio-fluviatile sedimentary formation located in the eastern part of the Cordillera Real in the Andes Cordillera. The basement is represented by folded Ordovician schists. The Cangalli formation is known for its auriferous potential (placer deposit), particularly in the Mapiri-Tipuaniarea. The objective of this thesis is to bring new insights of the Cangalli formation emplacement. Except the richest part of the Cangalli, outcrops have been poorly studied. In addition, conditions of emplacement of the glacio-fluviatile deposits and the fine distribution of gold are unknown. The studied area is located in the Rio Zongo area, near the city of Canaravi, particularly La Esperanza, a concession of the company REXMA SAS, which represents an area of about 500 ha. A detailed study bench by bench has been made in the outcrops of the mine from the contact with the basement to the apex of the series. The contact surface with the metamorphic basement shows an erosive character with a complex geometry, sometimes marked by sub-vertical walls and pot holes reflecting an erosion in torrential regime. The contact also highlights tectonics after deposition of gold bearing formation by visible faults in the Cangalli. The series consist of plurimetric conglomerate layers that differ by the size and the nature of the clasts, although matrix is identical. It is possible to observe sequences with positive graded bedding positively, but negative and sometimes oblique gradings are common. The clasts comprise sometimes angular pebbles of Ordovician shales (especially at the base) and blocks of quartz, sandstone, quartzite from the Cordillera. An outcrop the Cangalli Formation presents two distinct colours: blue and red. This difference seems to be due to differential alteration. The highest concentrations of gold are located at the boundary between Ordovician schists and the Blue Cangalli. Sedimentological and mineralogical studies are in progress to understand the reasons of this distribution in order to define guidelines to exploration.

O.5- Trace metals mobilization from surficial sediments of the river Seine Estuary

Hamzeh M.1, Ouddane B.1, Billon G.1 1

FRE 3298 GEOSYSTEMES, Université Lille 1

Environmental contamination by metals is a worldwide problem. Urban, industrial and agricultural activities have contributed to a widespread contamination of aquatic ecosystems. Most of the metals are introduced in the aquatic environment associated to fine grained particles that progressively accumulate in the surface of the sedimentary column. Scavenging of trace metals in the sediments can be reversible due to several perturbations so as sediments also act as a source of pollutants for the overlying water. For instance, daily or seasonal natural events (tide, flood, storm) and anthropogenic processes (water management actions) can cause a disturbance of sediments and a subsequent remobilization of pollutants to the overlying water, thereby posing a potential threat for aquatic organisms. The estimation of the metal mobility was undertaken in this study on sediments sampled in the Seine estuary at the Pose dam, a site considered as one of the most polluted of the estuary. Sequential extractions of Fe, Cd, Mn, Cr, Ni, Cu, Pb and Zn were undertaken in surficial sediments for evaluating their distribution into four different fractions (exchange and carbonates, reducible, oxidizable and residual). The procedure used for these experiments is based on the BCR protocol (Rauret et al, 2007) with some modifications and has been validated by testing successfully the certified sediment material CRM 601. Some of our sediment samples were in anoxic conditions, and in order to limit the reoxidation of the reduced phases like iron sulphides, the two first steps of the sequential extraction were carried out under nitrogen environment. Another approach consists on sediment resuspension experiments in laboratory under controlled conditions to get new insights on the metal mobility in the overlying water. For that purpose, wet sediment was introduced into oxic filtrated river water and the mixture was stirred in an open cell during several days. Metal releases from the particles have been observed within the first minutes after the mixing, followed by a fast adsorption process on the suspended particles. Finally, these preliminary results obtained in the framework of the national program Seine-Aval (ToxSeine Project) will be confronted to toxicity tests carried out on the same sediments by the University of Bordeaux to get new information on the metal mobility towards the biota.

O.6- In situ measurement of dissolved phosphorus in aquatic media using diffusive gradients in thin-films

Prygiel E.1, Lesven L.1, Billon G.1, Ouddane B.1 1

FRE 3298 GEOSYSTEMES, Université Lille 1

In fresh water, dissolved phosphorus is considered as the limiting factor of the vegetable‘s growth, because it is naturally present in few concentrations. However, due to anthropogenic releases from domestic (washing powders), industrial (washing waters) and agricultural (fertilizers) activities, phosphates can be responsible of aquatic media eutrophication. Even if efforts have been lead since the 90s to reduce these emissions (phosphate treatments in sewage, reduction of tripolyphosphate in detergents), phosphate levels remain high. A monitoring of phosphate’s concentration in water is needed to understand the dynamic of the environment and to prevent some disagreements. In the literature, several methods including spectrophotometry, atomic absorption spectrometry, atomic emission spectrometry, ionic chromatography and electrochemical methods have been proposed for the determination of phosphate. In aquatic ecosystems, determination of phosphate is usually performed by an automatic colorimetric method using a Technicon AutoAnalyser which makes use of the blue color of the phosphomolybdic complex which is formed when ammonium molybdate and sulphuric acid are added to the water. The color may be compared with that of standard solutions by spectrophotometry (Murphy and Riley, 1962). Nevertheless, due to the dynamic interactions of phosphorous species in natural systems, concentrations of individual species may change when samples are stored. This is especially the case for sediment samples. Accurate analysis is, therefore, difficult unless measurements are made in situ. Some years ago, a new resin gel based on ferrihydrite was tested for application in diffusive gradients in thin-films technique (DGT) for in situ determination of phosphate (Zhang et al., 1998). Based on the same principle than DGT-Chelex for metals, phosphorus species diffuse through a layer of polyacrylamide gel and then bind to ferrihydrite embedded in a further layer of gel. The mass of phosphorus in the ferrihydrite after a known deployment time is then measured colorimetrically after acid elution. Concentration in the solution is then calculated using Fick’s first law of diffusion. A critical comparison between classical sampling method and DGT method will be presented. In addition, to illustrate this presentation, results from lakes and rivers will be discussed.

P.1- Salt tectonics and crustal tectonics along the Eastern Sardinian margin, Western Tyrrhenian : New insights from the « METYSS 1 » cruise

Gaullier V1., Chanier F2., Lymer G2., Maillard A3., Sage F4., Thinon I5., Lofi J6., Vendeville B.2 1EA

2

4218 Laboratoire IMAGES, Université de Perpignan

FRE 3298 GEOSYSTEMES, Université Lille 1

3Geosciences

Environnement de Toulouse (GET), Université de Toulouse

4Géosciences-Azur, Villefranche-Sur-Mer 5BRGM,

Orléans

6Géosciences-Montpellier,

Université de Montpelier II

The Tyrrhenian Sea is considered as a Neogene back-arc basin opened during continental rifting and oceanic spreading due to the eastward migration of the Apennine subduction system from Tortonian to Pliocene times. Rifting of the Tyrrhenian Sea started first along the Eastern Sardinian margin during the Tortonian-Messinian times, at the same time that Messinian Salinity Crisis. The « METYSS » project aims to better constrain the relations between deformation related to both crustal tectonics and/or salt tectonics and sedimentation from Messinian times to present-day. The « METYSS 1 » cruise (2009, R/V “Téthys II”-INSU) allowed us to obtain about 1200 km of highresolution seismic reflection profiles along the SE Corsican margin, and the Eastern Sardinian margin, Western Tyrrhenian. This dataset clearly illustrates that this area has been highly dissected during the rifting stage by N-S trending normal faults delineating ridges and basins. The Messinian seismic markers (like Evaporites of the “Upper Unit”), are syn-rift, as they display fan-shaped stratal geometries. The spatial repartition of the mobile salt can be also outlined. The highly-variable thickness of the confined salt basins could be due to the initial pre-Messinian basin geometry or to the syn-rift character of the deposition. Southeastward, salt tectonics appears highly vigorous. Seismic data demonstrate also significative reactivation of some major faults during the post-rift period up to late Quaternary. Such recent fault slips have been evidenced by bathymetric scarps and by associated footwall debris flows. Moreover, some of this post-rift deformation can be illustrated within the Plio-Quaternary sequence by a regional unconformity. The post-Miocene deformation shows various characteristics, depending on the occurrence of Messinian evaporites within the basins. The « METYSS 2 » cruise (2011, R/V “Téthys II”-INSU) should allow us to obtain more data, to have a better understanding of the Western Tyrrhenian basin.

P.2- A new insight in the phylogeny of the Devonian Asteropyginae (Trilobita)

Bignon, A1. and Crônier, C1. 1

FRE 3298 GEOSYSTEMES, Université Lille 1

The subfamily of Asteropyginae constitutes one of the most famous groups of Devonian trilobites. Indeed this subfamily is composed of genera with an unusual morphology among the order Phacopida such the long spines of Heliopyge and Psychopyge, or the long precephalic trident of Walliserops. This subfamily comprised more than 250 species from the Lochkovian to the Frasnian. Its biodiversity was affected by important fluctuations in agreement with the Devonian crises and radiations. Moreover, the Asteropyginae is world wide represented from America to Afghanistan via Europe and North Africa. Asteropyginae may be crucial for studying various research topics such evolution, ontogeny, paleoenvironment and paleobiogeography. A reliable phylogeny is required for such studies. Lieberman and Kloc (1997) realised a phylogenetic analysis on this subfamily. But, since their work new discoveries provide the opportunity to examine the extent of biodiversity. The purpose of the present work is to update the Asteropyginae phylogeny via a cladistic analysis. Traditionally, the evolution of this subfamily is interpreted as two major clades and is based on four pygidial patterns. The present cladistic analysis proposes a more progressive evolution with only one clade. Moreover, the pygidial patterns are redefined and five new cephalic patterns are proposed in accordance with the phylogenetical results. This study leads also the modification of genus diagnoses implying the recombination of several species.

O.7- Morphological affinities of cave bear dental elements among extant and fossil ursid populations: phylogenetic and ecological implications

Goubel H.1, Auguste P. 1, Crônier C.1 1

FRE 3298 GEOSYSTEMES, Université Lille 1

Although more and more clearly defined with the contribution of molecular data, the phylogenetic relationships among the Ursidae (including the giant panda) remain a topic of debate. By applying a geometric morphometry approach to deciduous dental elements, the objective of the study will be to bring new information on the construction of the phylogenetic framework of this group. An outline analysis will be performed on the first lower molar from extant and fossil ursids in addition to traditional measurements. The shape of occlusale surface is quantified without taking into account the size variability. Thus, morphological variability among several populations can be visualized into morphospaces. Firstly, the morphological plasticity of extant Ursidae will be analyzed at generic, specific and subspecific levels. The considered taxa are the giant panda (Ailuropoda melanoleuca David, 1829), the sloth bear (Melursus ursinus Shaw, 1791), the sun bear (Helarctos malayanus Raffles, 1821), the spectacled bear (Tremarctos ornatus Cuvier, 1825), the american brown bear (Ursus americanus Pallas, 1780), the polar bear (U. maritimus Phipps, 1774), the asian black bear (U. thibetanus Cuvier, 1823), the brown bear (U. arctos arctos Linnaeus, 1758), the east-siberian brown bear (U. arctos collaris Cuvier, 1824), the grizzly (U. arctos horribilis Ord, 1815) and the syrian brown bear (Ursus arctos syriacus Hemprich & Ehrenberg, 1828). Then, fossil populations of brown and cave bears (U. spelaeus, Rosenmüller & Heinroth, 1794 and U. deningeri Von Reichenau, 1904) will be integrated in the study. The interpretation of the cave bear morphological affinities within the group will indicate whether these morphological proximities are mostly ecological (diet related) or phylogenetic.

P.8- A cladistic test of echinoderm homologies, phylogenetic trees and character polarities

Devaere L.1 and Clausen S.1,2 FRE 3298 GEOSYSTEMES, Université Lille 1 7207 «Centre de recherche sur la paléobiodiversité et les paléoenvironnements» Muséum National d’Histoire Naturelle, Paris, France 1

2 UMR

Despite echinoderms being one of the most important and extensively studied invertebrate constituents of Palaeozoic ecosystems, their phylogenetic relationships are still highly debated. Their very incomplete Cambrian fossil record and their high disparity makes the reconstruction of their initial radiation difficult to understand. As a result, numerous models of homologies and related phylogenies have been proposed. Two major models (the Extraxial-Axial Theory and the ‘Carpoids as basal’ model) are evaluated herein through cladistic analysis. For the first time, 90 morphological traits in 38 basal echinoderm taxa have been successively coded according to each model and each matrix processed using PAUP* 4.0. Different taxa (echinoderms or hemichordates) have been selected for rooting in order to assess the effect of outgroup selection on the resulting phylogenies, and the self-consistency of each model appraised by comparing the topology of the obtained trees with a priori phylogenetic hypotheses. This study allows comparison of how the two phylogenetic models perform in term of (i) character interpretation, (ii) tree-topologies, and (iii) statistical support.

O.9- A new Upper Ordovician (Uppermost Darriwilian to Lowermost Sandbian) Radiolarian assemblage from Kazakhstan: Insights to Ordovician Radiolarian biodiversity

Pouille L.1, Danelian T.1, Popov L.2, Ghobadi-Pour M.3 FRE 3298 GEOSYSTEMES, Université Lille 1 Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, U.K. 3 Department of Geology, Faculty of Sciences, Golestan University, Gorgan, Iran. 1 2

Ordovician oceans witnessed profound changes in the structure of marine communities and food web during the “Great Biodiversification Event”. Our understanding of the origin, establishment and biodiversity dynamics of modern marine ecosystems at this period is very fragmentary. More particularly, data are rare and incomplete regarding radiolarians, a major component of the oceanic heterotrophic plankton in the early paleozoic marine ecosystem. We here report on a diverse and well-preserved radiolarian fauna from Kazakhstan, which was sampled from the Shundy Formation of the Aksuran Mountain, North Balkhash region. The Shundy Formation is composed of bedded black or dark grey limestones; they represent accumulation on the slope of a carbonate platform. Identified trilobites suggest an Upper Darriwilian to Sandbian age (Dw3Sa1). On the basis of SEM observations on over 600 specimens, the taxonomic study conducted so far on radiolarian suggests the presence of 4 families, 9 genera and 35 species. The radiolarian fauna is dominated by representatives of the family Inaniguttidae with the presence of 19 species belonging to Inanihella, Triplococcus, Inanigutta, Inanibigutta and Oriundogutta. Interestingly, this assemblage is characterized by the presence of abundant three-shelled radiolarians and it also appears to contain a number of new, previously unknown, morphotypes. The significant diversity of this assemblage contributes to improve knowledge of radiolarian diversity for the Upper Darriwilian to Sandbian age, previously considered to be of the order of 15 species. We focused on the study of the internal structure of the skeleton which allows us to identify new morphotypes and to conduct a taxonomic revision of the Inaniguttidae.

O.10-Ostracodes paleoecology and paleodiversity throughout the Middle Devonian in Ardennes. Comparison with a current carbonated platform

Maillet S1. 1

FRE 3298 GEOSYSTEMES, Université Lille 1

During the Givetian, Ardennes were a carbonated platform where numerous marine organisms evolved, of which the ostracodes. Located on the Rheno-Hercynian Ocean northern passive merging (south of the Old Red Sandstone continent) at a tropical paleolatitude, this platform presented reefal barriers. Different areas in the Dinant syncline (Ardennes) will be studied. Sampling bed by bed will be performed in several sections belonging to the Givetian stratotype (paleoenvironment close to the reefal barrier). Samples from others areas of this syncline, showing more proximal and more distal facies, will be collected. A spacio-temporal distribution pattern will be performed, showing the ostracodes populations evolution joined to a paleoenvironmental reconstitution. Possible bioevents may be characterised, as the Taghanic Event located at the end of the Middle Givetian. Morphological variability of some species due to environmental factors (ecomorphs) may be analyzed. A comparison of the Ardennes ostracodic fauna with others places will be made, either by direct sampling, by collection material reviewing or by bibliographical extension. Then, Holy Cross Mountains in Poland, Boulonnais in France and Eifel in Germany will be investigated, all belonging to the same carbonated platform as the Ardennes. Spain and Armorica (France), belonging to the old Rheno-Hercynian Ocean southern merging, will be also considered. Although they belong to the old Medio-European Ocean southern merging, Marocco and Algeria will be observed. Comparison of these faunas with Ardennes may indicate possible migratory paths and oceans opening during the Givetian. Finally, a comparison between givetian and present ostracodes environmental distribution will be attempted. Because Ardennes’ platform was carbonated, reefal and tropical, this comparison must be made with a similar current platform, as the Great Barrier Reef area.

P.11- What’s impact of THE taghanic event on tabulate corals of THE Ardennes?

Pinte, E1,2. and Mistiaen, B1. 1Laboratoire 2FRE

de Paléontologie stratigraphique, ISA & FLST

3298 GEOSYSTEMES, Université Lille 1

The Taghanic event is located in the Middle/Upper Givetian transition (late Middle Devonian). It extends from the middle part of Middle varcus to the basal hermanni Zones. This event, interpreted as polyphased, is considered as one of the major events of the Devonian (Aboussalam and Becker, 2001). A significant sea level change and a major global warming (Aboussalam, 2003) are probably the main causes to explain this extinction. In the Ardennes, the classical conodont biozonation cannot be used because of a reefal environment. Bultynck’s correlations (1974) locate the Taghanic Event in the lower part of the Fromelennes Formation (Flohimont Member). The impact of Taghanic event on tabulate corals is not clear. As for the rugose corals (Coen-Aubert, 2004) the biodiversity of tabulate corals decrease in the middle part of the Fromelennes Formation (Moulin Boreux Member, hermanni/disparilis Zone). Tabulate corals are reduced to scolioporids even if they are extremely abundant. Identically, in the Boulonnais area, in the upper part of the Blacourt Formation (Bastien Member), correlated with disparilis Zone, the diversity of tabulate corals is also drastically reduced to scolioporids (two Scolipora beds) associated with some auloporids. However, a decrease of morphological variability can already be noted at the Flohimont Member (top of varcus Zone). Tabulate corals are only represented by small and branching forms.

P.12- The Palaeoceanographic significance of Permian radiolaria from the Yangtze Platform (South China) Zhang, L. 1,2, Zhang, Q. 1, Ai, Y. 1, He, W. 1, Feng, Q. 1, Caridroit, M.2, Danelian, T. 2 1China 2FRE

University of Geosciences (Wuhan), Department of Earth Sciences, Wuhan, P.R. China. 3298 GEOSYSTEMES, Université Lille 1

The Yangtze platform is one of the three major cratons occurring in China, characterized mainly by shallow water carbonate sedimentation. Situated during the Late Palaeozoic in a tropical position, it entered since the Permian into collision with the Cathaysian and North China blocks. During the Permian siliceous sediments are particularly abundant around and within the Yangtze platform during the Permian, with a good Radiolarian record for the Middle Permian «Pseudoalbaillella globosa» biozone. Albaillellarian Radiolaria, considered in the literature to represent deep water niches, coming from six localities of the Northern part of the Yangtze platform and from one basin situated in its southern part (Qinfang trough), were compared between them and with a coeval assemblage yielded from equatorial oceanic chert sequences, preserved today in Japan. Results of a similarity analysis show that the assemblages from the northern Yangtze basins cluster together, while the Japanese assemblage plots in between the northern and southern assemblages. This may reflect the presence of two different oceanic water masses around the Yangtze platform. We believe this is the result of a bottleneck formed at this time between the Qinling Sea and the Palaeo-pacific ocean, which had as a result the restricted circulation of oceanic currents.