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This study explores the paleoenvironmental changes of the Acholla coast over the last 2000 years by means of subsurface sediment analyses of lagoonal deposits via a multiproxy approach. A sequence of 5 steps is shown to have shaped the coastal development at Acholla and includes (i) the settlement of an open marine embayment during the Upper Pleistocene (substage 5e) in response to a transgressive event as evidenced by the deposition of carbonate sandstones rich in mollusc associations and marine elemental ratios Sr/Al, Ca/Al, Cl/Al, and S/Al; (ii) a sea-level rise towards183 AD, after a long period of emergence of the coast, leading to transgressive deposits of poorly sorted fine sands that are rich in diversified mollusc and ostracod taxa; (iii) a high-energy event (towards 417AD) with a peculiar biofacies characterized by coarse bioclastic mollusc-rich sands, charcoal particles, Tyrrhenian lithoclasts, and high values of marine elemental ratios Cl/Al, S/Al, and Ca/Al; (iv) a progradation of coastal habitats (between 417 and 1577 AD), favored by a period of flooding/detrital input and longshore current drifts, resulting in the development of an extensive sandspit and the formation of the Acholla lagoon. The construction of a Roman pier, originally constructed to protect the Acholla harbor from sedimentation, was counterproductive and favored the expansion of coastal swash bars and extension of the sandspit, ultimately resulting in the abandonment of the Acholla harbor; (v) the closure of the lagoon (from 1577 AD onward) and the built-up of well-sorted silt deposits are marked by the decrease of detrital elemental ratios (Ti/Al, Si/Al, and K/Al) and by reduced ostracod species richness values. The inferred scenario for the evolution at Acholla coast matches those for Sfax and Skhira coast in the Gulf of Gabes (Tunisia). Unlike Sfax and Skhira, however, the Acholla coast has been subjected to uplift by active faults, resulting in a time shift of depositional patterns.

The present study investigates the history of the northern Sfax coast by means of subsurface sediments of the sebkhas El Merdessia and El Awebed through a multiproxy approach. Ostracod and mollusk assemblages, diversity index, sedimentological criteria, correspondence analysis, and radiocarbon datings together provide an overview of the development of this coast over the last 5000 years. Original data give evidence for periods of predominantly lagoonal and brackish water conditions. These data testify to the emersion of sebkha El Awebed during Holocene, while sebkha El Merdessia recorded three marine transgressions toward 4599, 2225, and 1396 years cal BP. These transgressions are indicated by the richness of sediments in lagoonal and marine ostracod assemblages coupled with marine mollusks and the high values of species richness and diversity index. Sandwiched between 2225 and 1396 years BP, a period of sea-level stability and buildup of sand barriers in front of the estuaries was evidenced. Toward 250 years cal BP, a tsunami event is evidenced by the deposition of a shelly bed containing angular and sharpened Cerithium vulgatum in coarser marine sands overlaid by silts and clays rich in charcoal particles and pottery fragments. The comparison between the proxies analyzed of the studied area and those of Skhira coast leads to the conclusion that the two coasts were subjected to the same factors. However, a time shift of sedimentation is due to the uplift of Sfax northern coast favored by the activity of the faults, unlike the southern Skhira subsidence.

Round-shaped sieve pores of Cyprideis torosa have negative correlation with salinity and are a useful proxy for reconstructing paleo-salinity trends, especially for oligohaline to mesohaline waters. However, given its time-consuming character, this method has only been used rarely. A protocol for the automatic detection of sieve pores from Backscattered Electron Scanning Electron Microscopy (SEM-BSE) images and ImageJ-FIJI software has been developed. The use of SEM-BSE images has optimized the sieve pore contrasts and extend the observation possibilities of sieve pores on less well-preserved valves. Automatic detection significantly reduces analysis times, by avoiding individual pore measurements and applying batch processes on samples. Rosenfeld and Vesper (1977) proposed an elongation index (length/beam) to discriminate round and elongated shapes, but the identification of irregular shapes only depends on the operator's appreciation. Due to the rapid acquisition of morphometric data with the automatic detection method, it is possible to systematize the use of metrical tools to discriminate sieve pore shapes. Two methods were developed from a repository based on metric variables obtained by manually digitalized 1490 sieve pores: (i) a Functional Discriminant analysis based on 5 variables (Feret's aspect ratio, roundness, aspect ratio and two ratios: Apore/AMinimum Bounding Circle and Ppore/PMinimum Bounding Circle) and (ii) an irregularity index (Roundness/(Apore/AMinimum Bounding Circle), as a complement to the elongation index. In addition, a bootstrap on 1774 sieve pores indicates that is useful to analyze over 10 valves per sample in order to estimate the proportions of these sieve pore shapes with an acceptable level of precision.

Examination of normal pore canals, especially sieve-type pore canals, in living and fossil representatives of ten genera of the family Limnocytheridae, subfamily Timiriaseviinae, has revealed important diversity of structure. These complex pore canals have been studied via high-resolution scanning electron microscopy (the Cartographic Method) and analysed via the application of newly devised indices to assess patterns of consistency and variation in both detailed structure of individual pores and of their distribution on the calcified valve. The timiriaseviine taxa are compared with species of the genera Limnocythere, sub-family Limnocytherinae and Cyprideis (family Cytherideidae). The relationship between the living animal and its aquatic environment is discussed in the light of previous studies and of new evidence herein. The importance of normal pore canals for systematics is highlighted by the recognition and definition of the new tribe Gomphodellini Danielopol, Cabral & Lord nov. tribe, subfamily Timiriaseviinae, family Limnocytheridae.

International audience; Ostia is one of the most extensively excavated cities of the Roman period. The port-city of Rome, which today lies 4 km from the coastline, was established in a very constrained environment at the mouth of the River Tiber. Based on a review of the geoarchaeological and archaeological research at Ostia, 4 new cores analysed through palaeoenvionmental methods, and 21 new radiocarbon dates, we propose a new model of the fluvio-coastal landscape of Ostia from its origin: (1) the coastline shifted rapidly westward between the 8th and the 6th c. BCE followed by a slow progradation and possible erosion phases until the end of the 1st c. CE; (2) the castrum of Ostia (c. late 4th–early 3rd c. BCE) was founded away from the river mouth but close to the River Tiber; (3) between the 4th and the 1st c. BCE, the River Tiber shifted from a position next to the castrum, below the northern Imperial cardo of Ostia, to 150 m to the north; (4) a possible harbour was established to the north of the castrum during the Republican period; (5) the city expanded and a district was built over the harbour and the palaeochannel between the Republican period and the beginning of the 2nd c. CE, showing that Ostia was a dynamic and resilient city during that time. Finally, we suggest the possibility to combine urban fabric analysis (the orientation of the structures) and palaeoenvironmental analysis for reconstructing the evolution of the city in relation to the fluvio-coastal mobility.

This study examines the evolution of the Skhira coast (Southeastern Tunisia) during Holocene times, by analyzing ostracodes, foraminifera and mollusk associations in subsurface sediments of both sebkhas of Dreiaa and El Guettiate. Nine biofacies represented by (1) five categories of lagoon namely widely opened, opened, brackish estuarine, closed and emerged; (2) the maximum of closure of environment revealed by continental and sebkha biofacies; (3) a peculiar two biofacies, formed by coarse sands or shelly clays and dominated by mollusk fragments and showing a mixture of lagoonal, marine and brackish taxa of mollusk, ostracods and foraminifera which provide evidence of high energy events (storms). The lower Holocene continental sediments are overlain by two transgressive categories of biofacies. The first one corresponds to a widely opened lagoon biofacies, related to the first Holocene marine transgression, around 7.46 ka cal BP. The second one, more important, consists of an opened lagoon biofacies between 6.67 and 5.91 ka cal BP. Sudden changes, during Holocene time, in the numerical distribution of foraminifera and ostracods species up cores are used to infer the change from widely opened lagoon, subjected to estuarine influences, to sebkha by passing by a close lagoonal environment. The enrichment of the sediment in quartz grains coupled with the action of the current drift authorized the build-up of sandy spits in front of the estuaries and the genesis of lagoon that preserve a rich assemblage of euryhaline foraminifera, ostracods and mollusks species. This process was interrupted by two distinct high-energy events. The break of sand spits induced the introduction of washover clay deposits at 5.418 ka cal BP and washover coarse sands at 644 a cal BP rich in mixture of brackish and marine macrofauna and microfauna.

Ras Ibn Hani peninsula, a wave-dominated tombolo (800 × 1000 m) on the Syrian coast, provides evidence for significant Holocene changes that can be linked to geological inheritance, rising post-glacial sea level, sediment supply and human impacts. Initial development of Ras Ibn Hani's coastal system began ~ 8000 years ago when shallow marine environments formed in a context of rising post-glacial sea level. Following relative sea-level stabilization ~ 6000 cal yr BP, beach facies trace the gradual formation of a wave-dominated sandbank fronted by a ~ 2300 × ~ 500 m palaeo-island whose environmental potentiality was attractive to Bronze Age societies. A particularly rapid phase of tombolo accretion is observed after ~ 3500 cal yr BP characterised by a two- to fourfold increase in sedimentation rates. This is consistent with (i) a pulse in sediment supply probably driven by Bronze Age/Iron Age soil erosion in local catchments, and (ii) positive feedback mechanisms linked to regionally attested neotectonics. Archaeological remains and radiocarbon datings confirm that the subaerial tombolo was probably in place by the Late Bronze Age. These data fit tightly with other eastern Mediterranean tombolo systems suggesting that there is a great deal of predictability to their geology and stratigraphy at the regional scale.

Resume Le port antique de Frejus, situe sur les marges d’une ancienne ria holocene, a fait l’objet d’un programme de recherches archeologiques et paleo-environnementales. Nous avons pu effectuer des carottages dans le bassin portuaire romain. L’etude haute-resolution des sediments a pour objectif la caracterisation et la reconstitution chrono-stratigraphique et bio-sedimentologique des milieux. Ces travaux ont permis : (1) de valider l’hypothese de Texier (1849) qui interprete le milieu pre-portuaire comme correspondant a un fond de baie marine. Excoffon et al., 2006 et Devillers et al., 2007 soulignent la presence d’une cote rocheuse a la butte Saint-Antoine, a l’epoque de la creation du port, rapidement transformee en cote meuble sous l’influence des apports detritiques de l’Argens ; (2) Nos travaux ont ensuite permis de valider la date de fondation du port estimee a 2025 ± 30 BP (120 cal. BC–60 cal. AD), en accord avec les ecrits historiques, au debut du regne d’Auguste, (3) de mettre en evidence deux stades de confinement portuaire. Le facies sedimentaire correspondant au milieu portuaire traduit une lagune euryhaline (B1 et B3). Il se continentalise progressivement en se transformant en un lac d’eau douce (B4), en raison de la progradation du delta de l’Argens qui a peu a peu eloigne le bassin portuaire de la ligne de rivage. La quasi-absence d’archives sedimentaires entre la fin du premier siecle avant notre ere jusqu’au septieme siecle apres notre ere (vitesse de sedimentation relative d’environ 0,5 mm/an) est revelatrice de possibles curages portuaires.

Global climate changes attract the attention of researchers working with paleoceanographic proxies for reconstructing past ocean circulation changes and the physico-chemical parameters that control environmental conditions. Moreover, recent studies highlight the importance of climate change on deep sea benthic biodiversity. Deep sea benthic fauna are not isolated from atmospheric processes and climate changes controlling surface ocean biota, for benthic assemblages respond to changing climatic conditions as well. Substrate and physico-chemical characteristics of bottom waters have particularly strong influence on ostracod species distribution in all marine settings, making them excellent environmental indicators. This paper focuses on changes in ostracod assemblages at MD99-2348 site, located on the continental slope of the Gulf of Lions to determine the relationship between climatic-driven oceanographic changes and ostracod diversity and abundance. High abundances of Henryhowella asperrima and Echinocythereis echinata during Heinrich events (HE1 and HE2) may result from increased oxygenation of the bottom water and a more pulsed supply of nutrients (organic matter). Formation of surface cold water that increases the oxygen content in deep layers in the water column is linked to the intensification of northerly wind (Tramontane and Mistral) in northwestern Mediterranean during the acme of HEs, when high latitudes bodies of cold air (Mobile Polar Highs) reach the Mediterranean area. Moreover, the concomitant high abundance of Krithe pernoides , which proved to be very sensitive to variable oxygen levels, probably records even shorter (millennial to centennial scale) climate oscillations. Changes in environmental conditions are illustrated by the shift of C . testudo–Loxoconcha spp. vs. Pseudocythere sp.– Macrocypris sp. that indicates detrital input, primary productivity and the possible impact of sea level oscillation on benthic assemblages since the LGM.

Goiran Jean Philippe, Tronchère Hervé, Carbonel Perre, Salomon Ferréol, Djerbi Hatem, Ognard Carole, Lucas Gérard, Colalelli Ugo. Portus. La question de la localisation des ouvertures du port de Claude : approche géomorphologique. In: Mélanges de l'École française de Rome. Antiquité, tome 120, n°1. 2008. Antiquité. pp. 217-228.

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 explain the altitude of these deposits. Likely explanations are a historical tsunami, tempest, and/or a very strong neotectonics in this area. We choose the later hypothesis because it matches the occurrence of an argilokinetic tectonic in front of the North Atlantic Moroccan margin. In this tectonic context, results of 14 C analysis data, i.e. 2400 ± 250 BP for one outcrop and 2170 ± 215 BP for a value in a core taken in the lagoon, we obtain a rate of uplift of about 14 mm/yr. Therefore, this region corresponds to an important tectonic junction between the stable Meseta to the south, the Rifian domain to the north and the accretionary prism, in relation with the subduction of the Atlantic crust under the African and European plates to the west. Moreover, in front of the studied site, many mud volcanoes have been observed in the Gulf of Cadiz, near the Moroccan margin.

During recent years, geo-archaeology has been revitalised and much effort has been made to combine geo-archaeological sciences like geomorphology, sedimentology, micropalaeontology and geochemistry with the cultural archaeological approach. The first definition of geo-archaeology dates back to the late seventies and since then has evolved to include more and more multidisciplinary studies. In this perspective, ostracods play a crucial role since they are valuable palaeoenvironmental indicators in all aquatic habitats, from freshwater to marine. Despite their potential, the integration of ostracods in archaeological studies has not been immediate. Only in the nineties did ostracod geo-archaeology seem to finally take its place, including a systematic approach to ostracod studies in archaeological excavations. Since then, many geo-archaeological investigations have included ostracod analyses, exploiting their potential as multitask tools. The research papers composing this special issue, demonstrate that ostracods can be used in the most diverse settings as tracers of archaeological material provenance, proxies for palaeoenvironmental and palaeoclimate reconstructions as well as clues to human impact.

The 1st International Symposium on Ostracoda (ISO) was held in Naples (1963). The philosophy behind this symposium and the logical outcome of what is now known as the International Research Group on Ostracoda (IRGO) are here reviewed, namely ostracodology over the last 50 years is sociologically analysed. Three different and important historic moments for the scientific achievements of this domain are recognised. The first one, between about 1963 and 1983, is related to applied research for the oil industry as well as to the great interest in the better description of the marine environment by both zoologists and palaeontologists. Another important aspect during this period was the work by researchers dealing with Palaeozoic ostracods, who had their own discussion group, IRGPO. Gradually, the merger of this latter group with those dealing with post-Palaeozoic ostracods at various meetings improved the communication between the two groups of specialists. A second period was approximately delineated between 1983 and 2003. During this time-slice, more emphasis was addressed to environmental research with topics such as the study of global events and long-term climate change. Ostracodologists profited also from the research “politics” within national and international programmes. Large international research teams emerged using new research methods. During the third period (2003–2013), communication and collaborative research reached a global dimension. Amongst the topics of research we cite the reconstruction of palaeoclimate using transfer functions, the building of large datasets of ostracod distributions for regional and intercontinental studies, and the implementation of actions that should lead to taxonomic harmonisation. Projects within which molecular biological techniques are routinely used, combined with sophisticated morphological information, expanded now in their importance. The documentation of the ostracod description improved through new techniques to visualise morphological details, which stimulated also communication between ostracodologists. Efforts of making available ostracod information through newsletters and electronic media are evoked.

The analysis of the surface ornamentation permits us to differentiate two morphotypes in the recent populations of the ostracod Urocythereis oblonga collected in shallow marine sediments of the Huelva littoral (SW Spain). An environmental analysis was made and its abundances were compared with different environmental parameters. Morph 1 (reticulated or “normal”) is almost always dominant, characterizing microenvironments with low salinity water changes, low to moderate energy levels, poorly sorted bottom sediments with high percentages of fine grain sizes (very fine sands, silts and clays) and moderate to high ostracod diversity. Morph 2 (punctuated or “degraded”) is significantly represented (> 10%) in stressing conditions, i.e., moderate salinity fluctuations, moderate to high hydrodynamic levels, low organic matter contents, moderate to well-sorted sediments with high percentages of medium sands and low to very low ostracod diversity. These differences make clear the potential of these microcrustaceans as environmental tracers in these transitional areas.

Tyre's ancient northern harbour has been a source of scientific intrigue and debate for many centuries. Today an insignificant fishing harbour, looking north and sheltered from the dominant winds by a sandstone reef system, is all that remains of the famous Bronze Age, Phoenician, Hellenistic, Roman and Byzantine anchorage havens. In light of this many scholars have long questioned whether the modern port corresponds to its counterpart in antiquity. Here, we provide litho- and biostratigraphical evidence for an ancient harbour approximately twice as large as the present, comprising the modern day harbour and city centre. Four distinct sedimentary units have been identified, translating the different Holocene palaeoenvironments: (1) The Holocene transgressive contact is dated ca. 7800 BP, and lies at the base of a silty-clay lithodependant unit. Our proxies are consistent with a low energy, lagoonal type environment, protected by an extensive reef system. (2) Transition to a coarse sand fraction after ca. 5500 BP is concomitant with the accretion of a semi-protected pocket beach. This environment served as a proto-harbour during the Middle Bronze Age (MBA). (3) After the MBA, artificial harbour sedimentation is represented by a fine-grained silty-sand unit with stress on the natural biosystem. This unit attests to a closed, marine-lagoonal type environment, which existed until around 1500 BP. Dredging activity during the Roman and Byzantine periods explains the absence of 1st millennium BC strata. (4) The economic decline of the ancient city after the Byzantine period is marked by the opening of the basin to greater marine influence, with a progradation of the harbour coastline. Natural sediment infilling diminished the size of the harbour to its present dimensions, lost until now, beneath the Medieval and Modern centres.

The reconstruction of past climates is a major challenge. One approach is the use of paleoceanography, which looks for clues to the past activity of deep-sea currents by associating them with the melting of the poles. In different sampling zones, fossil biomarkers are used to reconstruct the oxygenation levels of the sea bottom. Among the ostracods (crustaceans), the family Cytherellidae is considered to be resistant to significant decreases in oxygen and their fossil valves are used as biomarkers for oxygenation levels in the past. We studied the basic principles behind Cytherella cf. abyssorum’s ability to adapt to variations in water oxygenation levels in an attempt to determine what could differentiate it from other ostracods. Cytherella cf. abyssorum Sars 1866 has an activity level and ventilatory frequency only half that of ostracods studied previously. When subjected to a decrease in oxygenation, it demonstrates the beginnings of ventilatory adaptation which is unknown in the other studied ostracods. Some morpho-functional aspects are also remarkable, such as the presence of thick valves, which can close hermetically by means of powerful adductor muscles. Compared with already studied ostracods, Cytherella cf. abyssorum has, therefore, characteristics which suggest an ability to present increased resistance in hypoxia. We discuss these results in the paleoceanographical context by describing a scenario suggesting why an increased proportion of the ostracod population could indicate the existence of ocean bottoms with low oxygenation.

Resume Des depots continentaux d'âge pleistocene de la region de Boliqueime (Algarve, Sud du Portugal) ont livre de nombreux exemplaires de Darwinulidae appartenant a cinq especes. Elles sont associees a d'autres ostracodes limniques representes surtout par des juveniles de Candonidae, Ilyocyprididae, Limnocytheridae, Cyprididae et Cypridopsidae. Des charophytes, de petits gasteropodes et des rhizoconcretions calcaires apparaissent aussi dans quelques niveaux. Cette association faunistique met en evidence un paleoenvironnement fluvio- ou alluvio-palustre, d'eau douce a legerement saumâtre, sous un climat plus chaud que l'actuel. La taxonomie, variabilite et distribution geographique des Darwinulidae du Quaternaire ont fait l'objet de plusieurs travaux recents (Martens et al., 1997 ; Rossetti et Martens, 1996, 1998, 1999, 2002 ; Pinto et al., 2003, 2004) qui ont contribue a la description de nouveaux genres et especes, dont Vestalenula et Penthesilenula. Ces derniers genres ont une distribution mondiale, mais la plupart de leurs especes ont une distribution restreinte. La decouverte au Portugal de Vestalenula cylindrica, Vestalenula pagliolii , Vestalenula cf. sp. B et Penthesilenula brasiliensis permet donc de mieux preciser leur distribution et leur âge en Europe.

Resume Une recherche systematique des ostracodes continentaux du Neogene aquitain nous a montre que ces formes etaient bien representees localement, et susceptibles de fournir des renseignements paleoecologiques et paleoclimatiques aussi fiables que ce que l'on connait actuellement dans d'autres domaines continentaux. Il a ete etabli une liste des taxons, pour lesquels sont precisees la repartition stratigraphique dans le Miocene inferieur et moyen, et la position geographique par rapport aux traces des rivages a ces epoques. Ces donnees ont par ailleurs beneficie des revisions stratigraphiques recentes de nombreux depots miocenes, principalement marins, tant dans le sud et le centre que dans le nord du Bassin d'Aquitaine. La microfaune inventoriee comprend une vingtaine de genres et un peu plus de 30 especes. La plupart des genres rencontres correspondent a des groupes d'eau douce supportant souvent une legere salure (en particulier, les Cytheridae et les Candonidae). Un certain nombre de genres peuvent apporter d'autres indications ; par exemple Candonopsis et Sclerocypri s (a l'Aquitanien sommital) sont des ostracodes dont les representants actuels vivent dans la zone intertropicale. Au contraire, le genre Vecticypris , rencontre dans le Miocene inferieur du sud du bassin et proche du genre Metacypris , pourrait indiquer un episode de rafraichissement relatif des eaux.

SUMMARY An adaptation strategy whereby O 2 partial pressure, P O 2 , in the tissues is maintained within a low, narrow range of 1–3 kPa, largely independent of the inspired P O 2 , has been reported in water- and air-breathing poikilotherms and in homeotherms. Based on the postulate that this basic cellular mechanism has been established since the early stages of evolution, it has been hypothesized that it could be the consequence of an early adaptation strategy to maintain cellular oxygenation within the same low and primitive range. To test this hypothesis we studied the basic mechanisms of oxygen regulation in podocopid ostracods, minute crustaceans that have existed on earth for at least 500 million years. Podocopids lack any regulatory mechanism for adapting their ventilation to cope with changes in water oxygenation, and instead adjust their tissue oxygenation status by migrating through the O 2 gradient to sediment layers where the P O 2 of the water is 3–5 kPa. Experimental manipulation of the O 2 profile induced their vertical migration to follow this precise water P O 2 and demonstrates the existence of a regulation strategy. This strategy must be associated with the lower P O 2 values within the animal9s carapace valves, showing that podocopids can actively regulate their tissue P O 2 at constant but even lower values than the water. In conclusion, the low tissue P O 2 strategy could have existed in early crustaceans and, by extension, in early animals.

The late-Holocene stratigraphy of Marseilles harbour is presented together with archaeological evidence and radiocarbon data. An anthropogenic oyster midden, dated between c. 4260 and 340014C yr BP is followed by a period of siltation that ended the accretionary growth of an algal (marl) deposit. This event was caused by early human settlement. Subsequently the coastline was subject to progradation. It is argued here that the development of the first town of Marseilles, c. 2600 years ago, accelerated soil erosion and sediment deposition in the harbour area.

In the meso-oligotrophic Bay of Biscay, a diminishing downward organic matter flux with depth is accompanied by an important decrease of the liveforaminiferal density. Although bottom water oxygenation is not directly influenced by organic matter input, the oxygenation of interstitial waters andthe primary redox fronts do change in response to variations of the organic matter flux. The occurrence of deep and intermediate infaunal taxa can belinked to fundamental redox fronts and putative associated bacterial consortia. Our data are in agreement with the TROX-model, which explains thebenthic foraminiferal microhabitat as a function of organic flux and benthic ecosystem oxygenation. Both the depth of the principle redox fronts and themicrohabitat of deep infaunal species show important increases with depth. At the deepest oligotrophic stations, deep infaunal faunas become relativelypoor. Therefore, the exported flux of organic matter appears to be the main parameter controlling the composition and the vertical distribution of benthicforaminiferal faunas below the sediment-water interface. The oxygenation of pore waters plays only a minor role. A species-level adaptation of theTROX-model is presented for the Bay of Biscay.Keywords: Live benthic foraminifera; Exported organic matter flux; Redox conditions; Microhabitat

International audience; Most of the cities built by the Mayas in the Pet en area, in the Central Yucat an Peninsula, were abandoned 1200 to 1000 years ago. The phenomenon is sometimes un-appropriately called " the collapse of the Maya civilization ". Its main causes are still debated, ranging from climatic according to the occurrence of severe or modest droughts, to societal in the form of environmental mismanagement of the environment. In both processes, it is inferred that stress triggered the formation in many Pet en lake sediments of erosional clay deposits, known as 'Maya clays'. This work presents a high resolution, multi-proxy study of 'Maya clays' in lacustrine sediments from Laguna Tusp an, near the archaeological site of La Joyanca. Micropaleontological (ostracodes), mineral-ogical (clay minerals) and geochemical (bulk elemental composition and stable isotopes in organic carbon) records reveal three different phases of soil erosion throughout the last 5300 years. The oldest phase from 5281 to 2998 cal yr BP (i.e. 3331 e 1048 BC) is characterized by successive natural and moderate soil erosion deposits which follow climatic variations recorded in the American tropical belt. The time interval between 2998 and 1281 cal yr BP (i.e. 1048 BC and AD 661) contains four distinct erosional layers which, according to clay mineralogy, are indicative of both increased erosion of the regolith and strong soil loss. The most recent, also the most massive, deposit of Maya clay ends around 1281 cal yr BP (AD 661), that is some 200 years before the so-called 'Maya collapse' in the Pet en area. Recent archeological fieldwork studies indicate that a population mobility took place into the city of La Joyanca from its hinterland by the early Late Classic Period (ca. AD 600), that is, at the end or just after this erosion episode, and well before the occurrence of the Terminal Classic-Postclassic (AD 800e1250) drastic climatic changes. Shifts in environmental management by the local society and timing of urbanization may explain environmental changes better than droughts per se.

The La Perroche marsh is a small Holocene marsh on the south-western coast of the Oleron island (Bay of Biscay, France) presently occupied by a freshwater swamp and separated from the ocean by a continuous sand dune ridge. The study of its infill shows first basal conglomeratic deposits with calcareous pebbles on a Cenomanian rough substrate. The Holocene infill since 6000 years BP begins with a very fast sedimentation of sands. Then, the sedimentation becomes finer, with lagoonal to freshwater influences recorded by ostracods. The distribution of these deposits inside the marsh is asymmetric, with a thick sandy-gravely layer in the eastern part and a succession of sands, clays and organic layers in the western part. Communication with the sea is episodic, and the sedimentation is controlled by an active channel, as shown by the presence of displaced coastal-marine faunas at some sites. Around 5000 years BP, a coastal marsh began to develop with high organic matter contents. These organic deposits presently outcrop on the beach, suggesting a more seaward location of the shoreline at that time. Generally, these sediments are azoic. When fauna is present, it indicates brackish to freshwater environments showing a progressive isolation of the system. A second phase of terrigenous sedimentation occurred after a transgressive event around 2800-2500 years BP, but the communication with the sea was then very reduced, as indicated by mainly freshwater faunas. This transgressive event appears to be synchronous with a positive sea-level tendency recorded, throughout north-western European coasts, between 3000 and 2000 years BP. The definitive closing of the marsh occurred around 2100 years BP, after a second phase of freshwater marsh. (, Le marais holocène de La Perroche, localisé sur la côte sud-ouest de l’île d’Oléron (golfe de Gascogne, France), est actuellement un marais d’eau douce séparé du domaine océanique par un cordon dunaire continu. L’étude de son comblement au cours des 6 000 dernières années montre d’abord une invasion marine sur un substrat très accidenté d’âge cénomanien. Ensuite, se déposent probablement rapidement des sédiments sableux, témoins à la fois de l’établissement et du démantèlement de cordons dunaires et de l’érosion de l’arrière pays. Puis, la sédimentation devient plus fine et de type laguno-lacustre ainsi que le montrent les faunes d’ostracodes souvent associées aux sédiments. La distribution des dépôts dans le marais apparaît dés le début dissymétrique avec la présence d’épais niveaux sablo-graveleux à l’est et des successions de sables, d’argiles et de dépôts organiques à l’ouest. Les communications avec la mer sont épisodiques et le dépôt des sédiments est commandé par une chenalisation très active. Celle-ci est soulignée par la présence à proximité immédiate du chenal de faunes de type marin, le plus souvent déplacées et amenées en suspension. Vers 5000 ans BP s’installe un marais côtier, très riche en matière organique le plus souvent dépourvu de faune. Lorsque la faune est présente, elle indique des milieux laguno-saumâtres ou lacustres, confirmant ainsi l’isolation progressive du système. Des dépôts tourbeux trouvés sur la plage sont contemporains de ceux du marais actuel, ce qui implique une continuité sédimentaire entre ces deux sites et donc une situation des cordons dunaires plus au large qu’actuellement. Une seconde phase de sédimentation apparaît à la suite d’un événement transgressif vers 2800–2500 ans BP mais les communications avec le milieu marin sont très réduites comme le montrent les faunes majoritairement d’eaux douces. Cet épisode transgressif apparaît synchrone avec une tendance positive générale du niveau des eaux enregistrée entre 3000 et 2000 ans BP le long des côtes de l’Europe du nord-ouest. La fermeture définitive du marais intervient plus tard, après une seconde phase de développement de marécages vers 2100 ans BP.

In order to understand the early diagenesis processes occurring in continental margin environment, modern sediments collected in six different sites from the Bay of Biscay have been studied. These sites can be separated into two groups. In the shallowest stations, where sediments are highly bioturbated, organic carbon levels are higher than 2%. In the deepest stations, sediments are much less bioturbated, and organic carbon levels are lower. In all sites, the vertical distribution of redox sensitive species can be explained by the well-established depth sequence of redox reactions, based on the bacterially mediated oxidation of organic matter. We have considered some alternative reaction pathways to explain the profiles of Fe, Mn, and N species. These reactions deal with the ammonia oxidation by manganese oxide, the aerobic denitrification and the oxidation of dissolved iron (II) by nitrate or Mn-oxides. Vertical flux calculations with a simple diffusion model indicate that these reactions could account for the reduction of all the Mn-oxides and the oxidation of all the upward diffusing Fe(II). They may also be responsible for a significant part of the total dinitrogen production. The relative importance of these pathways on early diagenetic processes and benthic fluxes has not been determined and must be examined with additional experimental works. Our study suggests, however, that the coupling between the benthic cycles of iron, manganese and nitrogen could strongly influence the carbon cycling at the ocean floor.

Analysis of two core samples taken from the ancient harbour of Sidon allow us to identify two main fades. Sedimentological and radiocarbon analysis has revealed a first sequence before 3500-3000 years BC when Sidon 's harbour was first developped using natural shelters, namely reefs. It is after 3500-3000 years BC, that men learned to build moles structures in order to protect the artificial basin., L'analyse de deux carottes prélevées dans le port antique de Sidon permet d'identifier deux types différents de sédiments. A la base, un premier corps sableux, antérieur à 3500-3000 ans avant J .-C. correspond à des fonds marins de mode battu. Après 3500-3000 ans avant J.-C, les milieux vaseux évoquent un bassin portuaire artificiellement confiné et protégé par des structures archéologiques., Morhange Christophe, Dubuquoy Olivier, Prunet Nicolas, Ribes Emmanuel, de Beaulieu Jacques Louis, Bourcier Michel, Carbonel Pierre, Oberlin Christine, Doumet-Serhal Claude. Étude paléoenvironnementale du port antique de Sidon. Premiers résultats du programme CEDRE. In: Méditerranée, tome 94, 1-2-2000. Ports antiques et paléoenvironnements littoraux, sous la direction de Christophe Morhange . pp. 91-100.

The phosphorus geochemistry on the Bay of Biscay margin shows that modern sediments represent a source of phosphate for overlying seawater. However, particulate phosphorus leached with an ascorbate solution and 1 N HCl remains constant in the sedimentary column, which suggests that inorganic particulate phosphorus is trapped in the sediment. This is due to bioturbation, which carries iron oxides with high adsorption capacities for phosphate deep into the sediment, and also, to the precipitation of authigenic phosphate minerals in the anaerobic zone of the sediment.

The study of sediments and of the ostracofauna of four cores, taken on the rhodanian continental slope, allows to reconstruct variations of palaeoenvironments during the last glacio-eustatic cycle. The relative chronology, attributed to the different facies, shows that they intercept deposits going from the last glacial maximum until the Recent. The synthesis of analytic results conduit to the establishment of a sequence typical, dynamic and paleaoclimatic, constituted of three sedimentary ensembles. These ensembles correspond respectively to a period of low sea level, to the transgressive interval and to a period of high sea level. Reworkings and the influence of the continental shelf are important on the slope during glacial periods. Sedimentary environments are essentially controlled by the general circulation, that follows the continental slope, and by the morphology of the margin characterized by the indentation of canyons. Spatio-temporal variations of fauna of ostracodes reflect both changes of the palaeoenvironment to the interface water-sediment, especially, eustatic variations, hydrodynamic conditions and the climatical context. The conjunction of these two types of approaches has allowed to give an interpretation of the evolution of the hydrosedimentary and morphostructural framework.

Two species of the limnic ostracode genus Rosacythere Colin (Limnocytheridae, Timiriaseviinae) have been identified in the uppermost Bajocian (Middle Jurassic) of the southern part of the Paris Basin, France. This record is the earliest for this genus and for the ‘Kovalevskiella group’ of Colin & Danielopol (1978 Colin & Danielopol (1980). This study also confirms that most of the Timiriaseviinae morphological groups really started to diversify during the Middle Jurassic.

The North shore sediments of the ancient harbour of Marseilles reflects a complex history. As early as the Neolithic period, a noticable scouring of soils is identified and related to an extension of anthropisation. The first environnmental crisis occured arround 3 860 +/-130 B.P. (1 990-1 730 cal. B.C.). The silting of the maërl bio-accumulation and the oisters anthropic deposit will stop the maërl growth. It is a biological crisis linked with human coatal settlements. No morphological crisis is detected on the interland's hills. When Greeks colonized and founded Marseilles around 600 B.C., marine biocenosis of the north shore of the antic harbour, were strongly degraded. The successive urbanization of Marseilles ' hills will lead to a major detritic crisis. The impact of anthropization is therefore determining after 600 B.C., not only on the shores but also on the hinterland. In comparison, the East shore of the harbour reveals a detritic crisis between 600-350 B.C. and a sedimentary pause during roman times. These events occured more gradually because of both the presence of coastal swamps and the peri-urban location., Les sédiments de la rive nord du Lacydon reflètent une histoire complexe. Dès le Néolithique, un discret décapage des sols peut être identifié et mis en relation avec une extension de l'anthropisation. La première crise de l'environnement littoral a lieu au Néolithique Final, vers 3 860 +/-130 B.P. (1 990-1 730 cal. B.C.) : un envasement progressif et le dépôt anthropique d'huîtres vont arrêter la bio-accumulation de maërl. Il s'agit d'une crise biologique, liée à une occupation du sol limitée à la côte. Il ne semble pas y avoir de crise érosive sur les collines. Quand les Phocéens se sont implantés vers 600 ans avant J.-C., les biocénoses marines originelles de la rive nord du Lacydon étaient donc déjà fortement dégradées. L'urbanisation successive des collines de Massalia va entraîner une crise détritique majeure (Crise Détritique Phocéenne). L'impact de l'anthropisation est donc déterminant, à partir de 600 ans avant J.-C., sur le littoral mais aussi sur les collines. Par comparaison, la rive est du Lacydon enregistre la Crise Détritique Phocéenne et la pause morphogénique romaine d'une manière très atténuée et retardée par rapport à la rive nord. Les marais de bord de mer semblent le principal facteur de cette lecture brouillée et de cette réponse sédimentaire tamponnée des fluctuations climatiques et des pressions anthropiques., Morhange Christophe, Provansal Mireille, Hesnard Antoinette, Bouiron Marc, Bourcier Michel, Carbonel Pierre, Weydert Pierre. Morphogenèse et impacts anthropiques sur les rives du Lacydon à Marseille (6000 av. J.-C. - 500 ap. J.-C.) . In: Annales de Géographie, t. 105, n°587, 1996. pp. 32-46.

The quantitative and qualitative study of the ostracod assemblages supported by the correspondence analysis (CA) allowed the reconstruction of the palaeoenvironnemental change during the Holocene in the sebkha Dreiaa of Skhira (Gulf of Gabes, SE Tunisia). Five phases were distinguished: the first phase (> cal. 6471–6874 yr BP) coincides with the first Holocene marine transgression following the deposition of the continental Holocene series. It induces the setting of an open lagoon where numerous Bivalvia, Gastropoda and marine ostracods lived. The second one (cal. 6471–6874 yr BP) is characterized by the development of brackish ostracods, high diversity index values and comparable percentages of the brackish, lagoonal and coastal assemblages. It corresponds to an open lagoon subjected to estuarine influences. During the third phase (cal. 3350–3752 yr BP), a marine environment, marked by the enrichment of marine ostracods, is evolving toward the closing. The settlement of the restricted lagoonal environments is linked to the building-up of sandy spit. At cal. 2839–3057 yr BP, the dominance of coastal ostracods, associated with coarse sands, show an open lagoon and probably a marine transgression evidenced by the progressive modification in the ostracods assemblages. After this transgression, the southern part of Sebkha of Dreiaa emerged and evolved towards the present state. The last phase, cal. 515–777 yr BP, is marked by a strong marine influence, in the northern part of the sebkha, with transport of marine Bivalvia, Gastropoda and ostracods towards the inner lagoon by means of storms. The rupture of sandy spits induced the introduction of marine macrofauna and microfauna which were accumulated and associated with charcoals and coarse sands.

This paper provides quantitative information concerning the response of ostracods to environmental variability in order to reconstruct past environments. Ostracod faunas from modern sediments of Bolivian lakes and swamps were studied. Ostracod distribution is controlled by several ecological characteristics such as lake-level and water chemistry. Statistical results indicate that three transfer functions (on water depth, Total dissolved Salts and water in Mg/Ca ratio) can be developed, from ostracod species frequencies in lacustrine sediments, with some restrictions for the two last ones.

Les recherches en géoarchéologie portuaire à Portus ont permis de faire progresser nos connaissances dans cinq domaines principaux. (1) Le port est bien muni de deux ouvertures : une principale à l’ouest et une secondaire au nord. Cette dernière possède un profil dissymétrique. (2) Le niveau marin antique a été découvert, sur les quais, sous la forme d’une ligne de coquillages fixés datée de 2115 ± 30 BP soit 230 à 450 ap. J.-C. Après cette période, la connexion entre la mer et les bassins était rendue difficile. (3) Cette ligne se situe 80 cm sous la ligne de coquillage actuelle et montre ainsi une hausse relative du niveau marin. (4) Grâce aux campagnes de carottages, les paléo profondeurs des bassins et des chenaux d’accès sont désormais bien connues. (5) Le port de Claude, exposé, s’ensable lentement alors que le port de Trajan, protégé, s’envase rapidement. Geoarchaeological research at Portus has allowed us to improve our knowledge of this port in five main areas. (1) The harbour is equipped with two openings: the main one to the west and a second to the north. The latter has a shapeless outline. (2) The ancient sea level has been discovered along the quays, through a line of shellfish attached to them that date from 2115 ± 30 BP or AD 230 to 450. After this period connectivity between the sea and the basins became difficult. (3) This line is located 80 cm under the present line of shellfish and thus shows a relative increase in the sea level. (4) Thanks to coring work, the paleo-depths of the basins and the access channels are now well known. (5) The exposed Claudian port underwent a gradual silting up while the protected Trajan port silted up rapidly.

L'etude quantitative et qualitative des ostracodes des carottes SG1 et BSC2, prelevees au niveau de la Sebkha El-Guettiate de Skhira (Sud - Est Tunisien), nous a permis de reconnaitre les trois associations suivantes : (1) association de milieu marin s.l. composee de Aurila prasina Barbieto-Gonzalez, 1971, Cushmanidea elongata (Brady, 1868), Urocythereis oblonga (Brady, 1866), U. favosa (Roemer, 1838) (marin cotier), Basselerites berchoni (Brady, 1869), Semicytherura incongruens (G.W. Muller, 1894), S. paradoxa (G.W. Muller, 1894), S. sella (Sars, 1866), S. ruggierii (Pucci, 1955), Carinocythereis carinata (Roemer, 1838) et Paracytheridea depressa (G.W. Muller, 1894) (marin ouvert) ; (2) association de milieu lagunaire, a salinite variable, constituee, de Xestoleberis aurantia (Baird, 1838), Leptocythere fabaeformis (G.W. Muller, 1894) et Cytherois fischeri (Sars, 1866), (3) association de milieu saumâtre estuarien ou se developpent Cyprideis torosa (Jones, 1850) et Loxoconcha elliptica Brady, 1868. Ces associations revelent les caracteristiques des paleo-environnements qui se sont succedes, au cours de l'Holocene superieur, a l'emplacement de la Sebkha El-Guettiate. Trois phases peuvent etre reconnues : i) la premiere phase a caractere lagunaire estuarien dominant (6595 ± 120 a 6055 ± 30 ans B.P.) comprend un environnement lagunaire ouvert riche en ostracodes marins dominants evoluant brutalement vers un environnement lagunaire estuarien. Ce dernier est caracterise par un evenement de haute energie, vers 6595 ± 120 ans B.P., revele par des apports detritiques riches en galets, synchrones a l'enrichissement des ostracodes saumâtres. Ensuite, une lagune s'installe vers 6055 ± 30 ans B.P. permettant le developpement des ostracodes principalement saumâtres dominants mais aussi lagunaires. ii) la phase suivante (6055 ± 120 a 5150 ± 50 ans B.P.) se distingue par la reapparition des taxons marins associes aux especes lagunaires et saumâtres traduisant une lagune estuarienne largement ouverte soumise a l'influence des courants de derive littorale. Ces courants, en edifiant des cordons littoraux, ont entraine la fermeture du milieu et la fin de la dominance des ostracodes saumâtres. iii) la derniere phase (5150 ± 50 ans B.P. a l'actuel) comprend un milieu caracterise par la richesse des taxons lagunaires evoluant vers un milieu laguno-saumâtre recevant le depot de washover suite a un evenement climatique extreme. La lagune, de plus en plus fermee, evoluera progressivement vers la sebkha actuelle.

A multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the Lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to ~2500 yr cal. BP and from 1150 yr cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and hurricane landfalls, leading to marine sand inputs into the pond. The intermediate time interval, from 2500 to 1150 yr cal. BP, is typified by black organic mud deposition, suggesting that hypoxic to anoxic conditions prevailed at the pond bottom. These were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata shows that the lowest δ13C values are recorded during the hypoxic periods, as a consequence of bacterial recycling of isotopically depleted organic matter. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, central coast of Belize or Barbados. By constrast, discrepancies seem to emerge from the comparison between hurricane activity recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Intertropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dry climatic conditions. Plausible links with the North Atlantic Oscillation (NAO) are also suggested.

International audience

A 122 cm-long core was taken in the El-Guettiate Sebkha of Skhira (southeastern part of Tunisia) in order to investigate the recent palaeoenvironmental evolution of this region. The quantitative and qualitative analysis of ostracod and benthic foraminifera assemblages coupled with a correspondence analysis allows the reconstruction of palaeoenvironmental changes during the Holocene in this area. Four typical associations of ostracods (open marine, coastal marine, lagoonal and estuarine brackish) and two associations of benthic foraminifera (coastal and lagoonal) were distinguished. The onset of restricted lagoonal environments linked to the building-up of sand spit led to the onset of restricted lagoon and brackish environment at cal. 5408 years BP. The Shannon and equitability index of diversity were used to decipher the structural variations of the populations of ostracods and benthic foraminifera along the sampled core. We note a reduction in the Shannon index from the bottom to the top, which indicates a progressive isolation of the biotope. The open lagoonal episode is characterized by high values of diversity. During restricted lagoonal episodes the Shannon and equitability index are reduced. The correspondence analysis reveals an environmental gradient related to the marine influence. It shows an antagonism between the widely opened estuarian lagoonal species and those of restricted lagoon. The less opened estuarian lagoonal taxa occupy an intermediate position. Based on these evidences, microfauna carried out in the El-Guettiate Sebkha allows us to recognize four phases beginning with a widely opened estuarian lagoon (ca. cal. 7460 years PB), followed by a restricted lagoon (ca. cal. 5408 years BP) and finally a brackish lagoon evolving towards the present-day sebkha environment. The opened estuarine lagoon is characterized by high values of species richness and diversity indices.

During the first and second centuries AD, Emperor Claudius and then Emperor Trajan successively ordered the construction of two large harbors on the Tyrrhenian coast. Research resulted in advances in understanding the palaeoenvironments of the Portus. From a bathymetric point of view, the drillings indicate a 7/8 m depth for the main basins. Different sedimentary behaviors were observed: Claudius' basin shows sand accretion, whereas the access channel to Trajan's basin shows mud accumulation. Trajan built the second hexagonal basin because Claudius' harbor did not protect the ships from the wind and swell, and not because it was prone to rapid silting. In terms of chronology, the channel between both basins worked between the end of the 2nd century and the beginning of the 5th century, when it became completely clogged. This means that, after the beginning of the 5th century, only the junction channel (canale traverso) remained to provide an access to the Tiber and to the sea.

For the first time, a large Eemian paleolake was observed by 29°N in the Mudawwara depression (Southern Jordan) which prolongates into Saudi Arabia. Lacustrine coquina shows that vast lake complexes existed in the depression during oxygen isotope stages (OIS) 7a–6e, 5e and 5c–a. These ages correlate with those of Sahara Pleistocene paleolakes and bring into question the range of monsoonal and Mediterranean rainfall over the Arabian Peninsula during the Last Interglacial. The presence of Levallois–Mousterian artefacts along the lake shores indicates that the area was inhabited during these periods.

Les tufs calcaires constituent des enregistrements clés pour l'étude de l'évolution climatique et des réponses environnementales au cours des inter­glaciaires pléistocènes en Europe de l'Ouest. Dans ce cadre, l'étude pétrographique de 34 lames minces de la séquence de tuf du début du Pléistocène supérieur de Caours a été comparée à d'autres données paléoécologiques telles que les faunes de mollusques et d'ostracodes et aux résultats d'analyses sédimentologiques. A la base, les dépôts fluviatiles fins, détritiques, traduisent dans leur partie supérieure le passage aux conditions interglaciaires. La construction du massif de tuf qui suit, résulte de la précipitation de calcite par des cyanobactéries des genres fossiles Broutinella, Ponsella et Ponsinella. Les deux premiers sont responsables de la construction de stromatolithes, bien cristallisés, associés aux zones de chenal. Broutinella intervient égale­ment dans la construction de tuf en dôme de type « chou-fleur », présent dans les milieux toujours en eau, dominés par des faunes de mollusques aqua­tiques et d'ostracodes. Ponsinella est à l'origine d'un faciès « mille-feuille », associé à de nombreux épisodes d'assèchement et à une malacofaune à dominante terrestre. La diversité des faciès et des encroûtements et leur comparaison avec les biomarqueurs, notamment malacologiques, soulignent des variations environnementales intervenues au cours de l'interglaciaire 5e. Calcareous tufa deposits are essential record of the climatic evolution and its environmental responses during Pleistocene Interglacial in Western Europe. A petrographical study of 34 thin sections from Caours tufa deposit was compared to other palaeo-ecological data, such as mollusk and ostracod fauna and to the results of sedimentological analyses. In the lowest part, fine detritical alluvial deposits show the transition to interglacial conditions. Above, the tufa deposit is precipitated by cyanobacteria of the fossil genus Broutinella, Ponsella and Ponsinella. Broutinella and Ponsella built well crystallized stromatolites in and at the top of channels. Broutinella also builts a massive tufa qualified as "cauliflower". This facies precipitates in places always in water and associated to aquatic mollusks and ostracods. In massive tufa, Ponsinella dominates the "mille-feuilles" facies associated to dry phases and mainly terrestrial malacofauna. Consequently, the facies diversity compared to malacological data shows palaeoecological variations during the 5e interglacial.