Golfe Du Lion Research Articles

Population genetics reveals divergent lineages and ongoing hybridization in a declining migratory fish species complex.

Deciphering the effects of historical and recent demographic processes responsible for the spatial patterns of genetic diversity and structure is a key objective in evolutionary and conservation biology. Using population genetic analyses, we investigated the demographic history, the contemporary genetic diversity and structure, and the occurrence of hybridization and introgression of two species of anadromous fish with contrasting life history strategies and which have undergone recent demographic declines, the allis shad (Alosa alosa) and the twaite shad (Alosa fallax). We genotyped 706 individuals from 20 rivers and 5 sites at sea in Southern Europe at thirteen microsatellite markers. Genetic structure between populations was lower for the nearly semelparous species A. alosa, which disperses greater distances compared to the iteroparous species, A. fallax. Individuals caught at sea were assigned at the river level for A. fallax and at the region level for A. alosa. Using an approximate Bayesian computation framework, we inferred that the most likely long term historical divergence scenario between both species and lineages involved historical separation followed by secondary contact accompanied by strong population size decline. Accordingly, we found evidence for contemporary hybridization and bidirectional introgression due to gene flow between both species and lineages. Moreover, our results support the existence of at least one distinct species in the Mediterrannean sea: A. agone in Golfe du Lion area, and another divergent lineage in Corsica. Overall, our results shed light on the interplay between historical and recent demographic processes and life history strategies in shaping population genetic diversity and structure of closely related species. The recent demographic decline of these species' populations and their hybridization should be carefully considered while implementing conservation programs.

Grain-Size Components As Markers of Origin and Depositional Processes In the Coastal Zone of the Golfe Du Lion (Mediterranean Sea, France)

Abstract A study of beach and nearshore sands between the mouth of the River Aude and Cap d'Agde (northwestern Mediterranean Sea) shows the existence of four sediment types (ST): ST1 to ST4, with ST2 seemingly deriving from ST1, revealed by grain-size modal analysis and confirmed by a deconvolution program (LogNormal Deconvolution of Grain Size). Grain-size skewness is related to a much more persistent multimodality than graphic evidence can show. Multimodality results from mixtures of generally three STs and/or variants (the latter defining monotype grain-size distributions). Monotype mixtures are unequally distributed in morphodynamic zones, very abundant on the lower shoreface, significantly present on the berm and inner bar, but rare in the most dynamic zones (i.e., the collision zone and outer bar). On the berm and lower shoreface, modal values of the three sedimentary variants retain a close grain-size relationship. On the berm, where only bedload is present in the swash, monotype grain-size distribution trends towards a lognormal model. This trend can also be observed on the lower shoreface, where there are numerous monotype grain-size distributions (GSDs), possibly indicating a dominant process. When compared with ST1-dominated grain-size distributions of the outer bar zone, the distribution of the derived ST2 on the lower shoreface has an added fine tail derived from the coarse-skewed outer-bar sands. In addition, positive skewness of the lower-shoreface sands could indicate input of fine particles from deeper zones under the influence of shoaling waves and upwelling. Morphodynamic zones are approximately characterized by the distribution of grain-size indices. A change in the direction of the skewness sign can be observed between the shoaling zone and more energetic zones, from the breaker zone up to the berm. Finally, a more detailed description of the spatial properties of grain-size distributions could, first, help explore possible mechanisms underlying sediment sorting in the coastal zone and, second, provide a set of indices that would be of use in paleogeographic reconstructions and organization of basin borders, while improving discrimination and classification of environments.

Influence of Mixtures of Grain-Size Populations on the Parametric and Modal Characteristics of Coastal Sands (Herault, Mediterranean Sea, France)

Abstract Grain-size distributions in lower beach and nearshore sands of a segment of the coast of the Golfe du Lion (France) were analyzed by a parametric method and by modal analysis. The results have been considered both in a spatial framework delineating geographically distinct sedimentary compartments and cells, and in a morphodynamic framework separating the dynamic components of the shoreline (berm, collision zone, inner bar, outer bar, lower shoreface). Modal statistics indicate that a mixture of three dominant components (end members) contributes to the grain-size distribution (GSD) of the sediments: fine sand (Sedimentary Type I: Modal value: 0.195 mm; σI (Φ): 0.35), medium and coarse sand (ST II: Modal value: 0.680 mm; σI (Φ): 0.8) and very coarse sand and gravel (ST III I: Modal value: 2.3 mm; σI (Φ): 1.5). Quasi log-normal one-component GSDs form a minority group and mixtures produce various apparently unimodal sands and bimodal sediments. A large variation of grain-size indices results from mixing. A simulation of mixing of log-normal populations close to the end members shows the great sensitivity of parameters (sorting, skewness, and kurtosis) to small changes in the compositional formula of the mixture. The procedure followed supplies a good preliminary tool enabling rapid identification and localization of the main sand sources on a regional scale. These components derive from potential sources available in the region, well known from previous studies. ST I originates from the River Rhone and provides the textural base for most of the sediments. ST II and III form a local component originating either from fluvial input (Aude, Orb, and Herault rivers) or from the nearshore reworking of ancient Quaternary sediments and late Holocene beachrocks. Each ST takes on local aspects in relation to the morphological environment, but the regional scale of the study was too large to precisely reflect the local morphodynamic regime. A significant change in the ST I sorting of bar sands is, however, observed, probably due to the net offshore migration reported for the bar system.

The Holocene transgression in the Golfe du Lion, southwestern France: Paleogeographic and paleobotanical evolution

Starting from multidisciplinary punctual results, the authors offer a synthesis of lithologie seismic analysis, sedimentology, palynology and radiometrical measurements from sites in sea and at the border of the Golfe du Lion. The dated samples (more than 120) and the variety of the studied sites has permitted a true methodological approach. The authors also propose a curve of the rising of the Holocene sea that takes into account two major facts: the géomorphologie localisation of the site and the characteristics of the sedimentary environment (sedimentary facies and paleobotanic environment). They conclude to: 1) a generalised rapid rise of the transgression since 14,000 years BP, with an acceleration from 8000 to 6000 years BP; 2) intervals of relative stability from 12 000 to 8 000 years BP; 3) a high sea-level at +2 m at around 4500 years BP.

Effects of current and historic habitat fragmentation on the genetic structure of the sand goby Pomatoschistus minutus (Osteichthys, Gobiidae)

Habitat fragmentation is a major force that will influence the evolution of a species and its distribution range. Pomatoschistus minutus, the sand goby, has a North Atlantic–Mediterranean distribution and shows various level of habitat fragmentation along its geographic repartition. The use of mitochondrial sequences of the cytochrome b (cyt b) gene and two co-dominant sets of nuclear markers (introns and microsatellites) allowed us to describe the relationships between P. minutus populations belonging to several different geographical regions of Europe and to assess the structure of populations inhabiting the Golfe du Lion, along the French Mediterranean coast. The present study confirms that the taxon located in the Adriatic Sea (Venice) should be considered as a distinct species, separated approximately 1.75 Mya. The comparison of P. minutus between the Atlantic and western Mediterranean coasts using polymorphic co-dominant markers revealed that they belong to two demographically independent units, and thus could be considered as well as distinct species, more recently separated (0.3 Mya). The Pleistocene glaciations seem therefore to have played an important role in the diversification of this complex. Finally, at a regional scale in the Golfe du Lion, P. minutus appears to form a single huge homogeneous population.

Land and sea study of the northeastern golfe du Lion rifted margin: the Oligocene – Miocene of southern Provence (Nerthe area, SE France)

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

Linking benthic biodiversity to the functioning of coastal ecosystems subjected to river runoff (NW Mediterranean)

Continental particulate organic matter (POM) plays a major role in the functioning of coastal marine ecosystems as a disturbance as well as an input of nutrients. Relationships linking continental inputs from the Rhone River to biodiversity of the coastal benthic ecosystem and fishery production were investigated in the Golfe du Lion (NW Mediterranean Sea). Macrobenthic community diversity decreased when continen¬tal inputs of organic matter increased, whereas ecosystem production, measured by common sole (Solea solea) fishery yields in the area, increased. Decreases in macrobenthic diversity were mainly related to an increasing abundance of species with specific functional traits, particularly deposit-feeding polychaetes. The decrease in macrobenthic diversity did not result in a decrease, but an increase in ecosystem production, as it enhanced the transfer of continental POM into marine food webs. The present study showed that it is necessary to consider functional traits of species, direct and indirect links between species, and feedback loops to understand the effects of biodiversity on ecosystem functioning and productivity.

Paleo sea levels reconsidered from direct observation of paleoshoreline position during Glacial Maxima (for the last 500,000 yr)

The drastic climatic changes which characterise the cooling trend of the last few million years of Earth history led to variations in eustatic sea level that had tremendous impact on the geology and ecology of continental margins. Reconstructing a sea-level curve back in time is not an easy task. Observations of shoreline positions are always a local measurement of Relative Sea Level that needs to be corrected from the effect of tectonic and thermal subsidence, sediment loading, compaction and glacio-hydro isostasy. Extensive studies have been done for the last deglaciation and for the last 100,000 yr cycle. But very few studies deal with position of sea level during earlier cycles, simply because conditions are very rarely favourable for the preservation of such witnesses. The shelf of the Golfe du Lion (Western Mediterranean) reveals a unique record of shoreline paleopositions during glacial maxima of at least the last five circa 100 kyr glacial/interglacial cycles. In fact it is the entire glacial deltaic lobe of up to 50 m thick (from delta front or shoreface to prodelta) that has been preserved in place and which provides direct and independent constraints for relative sea-level minima. We measure a relative sea level of: −112m, −128, −134, −246 and −262 m for MIS 2, 6, 8, 10 and 12 respectively. After corrections taking into account postdepositional movement of strata (subsidence), we find, that sea level dropped to a depth of −102±6 m during the last three glaciations (MIS2, MIS6, MIS8) but reached exceptionally low values of more than −150±10 m during the preceding glaciations MIS10 and MIS 12 at about 340 and 434 kyr BP. This general time framework and sedimentological interpretation has been confirmed by preliminary results from two deep drillings during the PROMESS cruise (july 2004), which validate our methodology. However, no detailed and absolute datings of such witnesses are available so far, so that we cannot prove that these levels are the lowest ever reached during each glacials, but they correspond undoubtedly to the last preserved shoreface before rapid sea-level rise. We also suggest that the abrupt change in sea-level maxima might be the overprint of 400 kyr orbital periodicity cycles. Last but not least, these results prove that the Golfe du Lion is indeed a unique laboratory to study paleoclimates and sea-level variations on a larger time scale. Further work is needed for a complete glacio-hydro-sedimento isostatic modelling of each sequence and each glacial to further constraint local sea level versus global sea level and quantify, in particular the relative effect of glacio-hydro isostatic effect (which differ according to ice sheet extend) but also of erosion–sedimentation isostatic effect (erosion on land and deposition on the outer shelf and slope).

Mechanisms of enrichment of natural radioactivity along the beaches of the Camargue, France

A field study was carried out along the Golfe du Lion, that focussed on the beaches of the Camargue, to locate the main areas where enriched U and Th are found, and to better understand the processes that concentrate radioactivity on beaches. Indeed enriched areas are observed on some Camargue beaches, where high-dose rates are recorded due to excess U and Th activity (>1000 Bq kg −1). The coastline was mapped by means of an aerial gamma survey and the results indicated that the main actinides deposits occurred in the Camargue area. This concentrating effect is possibly due to a greater sedimentary contribution from the River Rhone relative to other minor Mediterranean rivers. Across the along-shore profile, the variability in actinides observed at the eastern part of Beauduc spit is mainly explained by variations in heavy and light mineral contents. Such variability can be accounted for by redistribution of the sand caused by erosion/deposition processes occurring in the eastern part of the spit. Further parameters such as grain size and heavy minerals content were studied in connection with the distribution of U, Th and 40K in the field at a more localised level (i.e. across-shore beach profile). The <200-μm fraction contains more than 50% of the radioactivity and heavy minerals (especially zircon) are the main contributors to the high levels of external radiation. Therefore the enriched areas, where U and Th exceed 1000 Bq kg −1, presumably result from the sorting of sand grains according to their size and density.

Differential distribution of the two cryptic species, Pomatoschistus microps and P. marmoratus, in the lagoons of southern France, with an emphasis on the genetic organisation of P. microps

The presence and the distribution of two cryptic sedentary gobies, Pomatoschistus microps and Pomatoschistus marmoratus, were investigated in several lagoons stretching along the Golfe du Lion, southern France Mediterranean coast, and Corsica. Pomatoschistus microps is the only sedentary Pomatoschistus species in two shallow lagoons with large variations of salinity and temperature. In contrast, P. marmoratus, another sedentary species, can be found preferentially in a deep salty lagoon with small salinity variations. Both species occur sympatrically in the Rhone Delta and hybridise, producing fertile offspring. Using allozymes, competition, linked to fitness, is invoked to explain the distribution pattern of these sibling species.

Laboratory hybridizations between Mytilus species and performance of pure species and hybrid veliger larvae at lowered salinity

Laboratory hybridizations between Mytilus species and performance of pure species and hybrid veliger larvae at lowered salinity

The deposition and erosion of cohesive sediments determined by a multi-class model

Sediment properties were studied experimentally using a laboratory flume and sediments sampled from both fresh and saltwater systems, i.e. the Rhône River and the adjacent continental shelf (Golfe du Lion, Mediterranean Sea). An experimental protocol is proposed which includes the development of an analytical method based on a multi-class model in order to determine the erosion and deposition fluxes of these sediments. This approach highlights the presence of a “fluff layer” characterized by a very low critical erosion shear stress and a second layer with a significantly larger critical erosion shear stress. If a global model is used, i.e. only one class of particles is considered, this distinction between the two layers cannot be made as sediment parameters are identified for the whole eroded particles including the “fluff layer”. Critical shear stresses of erosion were 0.05, 0.04 and 0.025 N m −2, respectively, for the first class of particles eroded at Rhône 1, Rhône 2 and SOFI stations. The second class of particles showed critical shear stress 10–20 times higher, around 0.20 N m −2. The use of the multi-class model allowed estimation of the erosion rates in the order of 2.5×10 −6, 6.2×10 −5 and 2×10 −6 kg m −2 s −1 for Rhône 1, Rhône 2 and SOFI. Settling velocities were in the order of 0.012–0.045 mm s −1 for the first class and between 0.05 and 0.09 mm s −1 for the second class. For the river experiments, it is shown that the “fluff layer”, corresponding to the first class of particles being eroded, is mainly representative of recent deposits of suspended particles probably trapped in the overlying water column during sediment sampling. This highlights the difficulties in sampling sediments and transporting these from field to lab and more generally into flumes, and the limits of applying a global model to flume experiments when studying sediment properties.

Palynological study of Antique shipwrecks from the western Mediterranean Sea, France

Antique shipwrecks of the western Mediterranean Sea constitute an exceptional source of data concerning naval and maritime Greco-Roman histories. Unfortunately, archaeological material gives no information about the location of Antique shipyards. The presented work tests the possibility of applying pollen analysis to resins found on shipwrecks in order to delimit their geographical origin. Pollen spectra obtained from resins preserved between wood pieces and in plant ligatures are compared to wood assemblages of two shipwrecks from the Golfe du Lion (southern France). Pollen spectra are comparable within- and between-shipwrecks, and correspond to the pollen content of resins from Antique amphorae found on the Roussillon coast, and from wood assemblages. Despite the few studied samples, these results point to the reliability of pollen data from wreck resins and provide some biogeographical indications: (1) the common set of taxa in the resins essentially reflects the arboreal vegetation surrounding the shipyards; and (2) the occurrence of Platanus both in pollen and wood records from the Baie-de-l'Amitié shipwreck (Cap d'Agde) allows location of the origin of this boat east of southern Italy.

Analysis of the postglacial deposits of the Rhône shelf (golfe du Lion). Implementation to the study of the late Quaternary depositional sequences

Abstract Postglacial deposits of the Rhône shelf have been studied from high-resolution seismic data and Kullenberg piston cores. They are organised into a set of transgressive units or parasequences backstepping from the outer shelf to the subaerial deltaic plain. On the deltaic plain, they are overlain by the prograding deltaic parasequences deposited at the end of the Holocene sea level rise. At regional scale, given the short time span covered by the late Quaternary deposits, tectonic subsidence has played a minor role and sediment deposition on the Rhône shelf was chiefly controlled by glacio-eustatic sea level changes (120 m between the maximum lowstand and present highstand). Progradational phases correspond to periods of reduced rate of eustatic sea level rise while the flooding surfaces bounding the regressive units form during periods of increasing rate of sea level rise and landward shoreline migration. At local scale, location, geometry, nature of deposits, and lateral variations of the stratigraphic pattern are controlled by the interaction between eustasy and local factors as sediment supply, antecedent morphology and ocean dynamics. Seaward of the Rhône river, terrigenous input was important during deglaciation and transgressive deposits extend continuously from the outer shelf to the inner shelf along the retreating path of the paleo-Rhône river mouth. Laterally, on either side of the Rhône incised valley, because of the reduced sediment supply, parasequences only develop on the outer shelf and inner shelf : the combination of the very low inherited gradient of the mid/outer shelf and a very high rate of sea level rise favoured a very rapid migration of the shoreline from outer to inner shelf. Ocean dynamics has been controlled, as in present time, by the E to SE prevailing waves that are the only ones which can develop on an extended fetch. The westward alongshore drift accounted for the development of parasequences west of the incised valley. The sandy material needed for the construction of the outershelf parasequence was supplied by wave-reworking and westward long-shore drift of deposits from the Rhône delta front and the uppermost forced regressive unit. The decreasing sand content of parasequences from outer shelf to inner shelf results from flattening of the equilibrium river profile that led to a decrease in competence and a change in the character of the sediment caliber (relative increase of suspension load). The underlying Pleistocene depositional sequences comprise both lowstand prograding units, that characterize most of the Mediterranean shelves, and intercalated units which are analogs of the postglacial transgressive deposits here presented.

La campagne FETCH - Etude des échanges océan-atmosphère dans le Golfe du Lion

Dédiée aux sciences de l'atmosphère, au climat et à d'autres domaines connexes, tels que l'océanographie ou la glaciologie, La Météorologie, révisée par des pairs et publiée en français, s'adresse aux professionnels de la météo et du climat, aux enseignants, aux étudiants, aux amateurs et aux utilisateurs. La Météorologie a succédé en 1925 à l'Annuaire de la Société météorologique de France (1852-1924) qui avait lui-même succédé à l'Annuaire météorologique de la France (1849-1851).

Les formations littorales pléistocènes du Languedoc [Pleistocene shorelines of Languedoc

A revision of the Golfe du Lion's coastal indicators permits, nowadays, to isolate four pleistocene transgressive levels. They correspond to four marine high-stands. The Pleistocene old level of Salses of « 27 m NGF can't be dated precisely. On the contrary the syn-vulcanic shorelines of Vias-Cap d'Agde, certified by theirs phreatic surtseyen products, of 5 m NGF high, are dated by K/Ar and paleomagnetism of paleomagnetic inversion Brunhes-Matuyama. During the Upper Pleistocene, two tyrrhenian levels are represented (stade 5). The eutyrrhenian shoreline, plentiful in the Corbieres, never overpasses 7-8 m of high in the 80 listed sites. The abundance of littoral sites attributable to the Eutyrrhenian, their sub-equality (if the shoreline is preserved) of the whole of the Corbieres and the Clape's limestone hills (here and there from the neogene gap of Narbon), pleads for a lack of later differential movements in this area. On the contrary, the materialization of slightly regressive shorelines reguarding to the regressive eutyrrhenien marina is seldom expressed precisely. The off-shore bar of the station of la Franqui, at 2,5 m high is one of the most representative structure. It has been dated by 14 C ≥ to 35 000 years and by a datation 230Th/234U, which hasn't given accurate result. The Holocene transgression, which hasn't been mentionned wittingly here, recovers to its transgressive maximum the same shorelines as Eutyrrhenian and Neotyrrhenian ages. This permanence in the position of the coastal prism for 125 000 years confirms the stability of the Golfe du Lion's margin since this period.

Abstract: Stratigraphic Organization of Late Pleistocene Deposits of the Western Part of the Golfe du Lion Shelf, Western Mediterranean Sea, Using High Resolution Seismic and Core Data

Abstract: Stratigraphic Organization of Late Pleistocene Deposits of the Western Part of the Golfe du Lion Shelf, Western Mediterranean Sea, Using High Resolution Seismic and Core Data

210Pb, manganese and carbon: indicators of focusing processes on the northwestern Mediterranean continental margin

Organic carbon contents, 210Pb data, and organic and oxidised forms of manganese in sediments are used for reconstructing the shelf and deep-sea transport of particulate matter and for evaluating early diagenesis conditions. The latter are used as indicators of focusing processes on the northwestern Mediterranean continental margin. Twelve different physiographical sites were sampled between 400 and 2000 m in the Pyrenean and Golfe du Lion canyon axes and on their open-slopes. In the canyon axes, which indent the Pyrenean slope, 210Pb activities show a regular exponential decrease with sediment depth: computed sedimentation rates range from 170 to 198 cm 10 −3 yr. For an identical regular exponential decrease in the Golfe du Lion canyon, the sedimentation rate is lower (119 cm 10 −3 yr). On the lower open slopes and deep-sea fans, rapid deposition (turbidites and surficial sliding) occurs onto sediments that were deposited regularly at a rate of about 175 cm 10 −3 yr. A deposit enriched in organic carbon is identified at mid-slope between 500 and 1300 m. In this area, surface sediments of the canyon axes are richer in organic carbon than at the adjacent open slope sites (0.9% against 0.6% dry weight). Canyon axes are more active than open-slopes as channels for organic matter transfer. In the axial channel of the Pyrenean canyon, organic carbon decreases exponentially in the uppermost 12 cm. In the Golfe du Lion canyons, only the upper 2 cm of sediment are enriched in organic carbon. This is related to lower sedimentation rates in the Golfe du Lion area as compared to the Pyrenean area. On the upper and lower open slopes, the organic carbon contents decrease rapidly within 1–2 cm of sediment. There is no exponential evolution profile and the residence times at the sediment-water interface are longer than in the canyons. The highest surface Mn concentrations are also found in the middle of the continental slope. The average is 64 μg g −1 for Mn associated with the organic phase (Mn(org)) and 1400 μg g −1 for (Mn(Ox)). As for organic carbon contents, canyons are areas of high concentrations. The lowest values (4 μg g −1 for Mn(org) and 495 μg g −1 for Mn(Ox)) are found for the lower open-slope (1200–1700 m) where there is active surficial remobilisation and gravity mass movements. Moreover, the vertical distribution of Mn has allowed us to identify sites located at depths of about 1000 m where the redox discontinuity is located in the first few centimetres and where the (Mn(Ox)) and the (Mn(org)) profiles display a positive gradient from the deepest layers to the sediment-water interface. The distribution of the various parameters was caused by three different mechanisms: (1) bottom advection of particulate matter transferred from the continental shelf deposits to the slope along the canyon axes; (2) scavenging of the dissolved phases of metals and (3) sedimentary focusing of the particles in a “favoured” area of the continental slope—a mid-slope depocenter. These data contribute to our knowledge of the role of continental margins in the global recycling of carbon and other materials.

Les sociétés riveraines du golfe du Lion (France) face à l'économie et aux sociétés touristiques et de loisirs (1960-1995) / Coastal communities of the Golfe du Lion (France ) confronted with the economy and the tourist and leisure society

The major rupture in the socio-economic life of the Languedoc-Roussillon seaboard had its origins in the 1960s with the setting up of five large-scale tourist centres created from scratch by the "Mission Racine" (1963-1982). These developments brought about the advent of a major mono-activity based on leisure along the coast which provoked both a decline and a restructuring of traditional maritime activities. The fishing communities along the "golfe du Lion" either endanger or adapt themselves to these changes, trying to conciliate their traditional structure with necessary economic modernisation.

Stacking Pattern and Stratigraphic Model of Reservoirs from a Modern Analogue to Ancient Deltaic and Siliciclastic Deposits: Golfe du Lion, SE France: ABSTRACT

The {open_quotes}Golfe du Lion{close_quotes} Pleistocene shelf deposits are used as modern analogues of ancient deltaic and shallow water siliciclastic deposits. At least 6 cyclic superimposed sedimentary packages constituting a seaward thickening wedge are documented, including major progradational clinoforms units bounded by regional unconformities, with their updip terminations. Seismic correlations and geometry models, together with age dating and facies analysis of the uppermost units have been used at regional scale. They allowed to differentiate allocyclic from autocyclic events, to improve our knowledge of the nature of tectonic control on architecture, and to rely the different seismic units, inside the packages, to the environmental changes from interglacial highstand to glacial lowstand in 4 to 5th order cycles. An alternative model of {open_quotes}forced regression{close_quotes} during sea level lowstand was documented and validated. The different illustrated sedimentary units, related to specific parts of the relative sea level curve along a short duration/high amplitude cycle, are: (i) the {open_quotes}forced regression{close_quotes} deposits (ii) the late lowstand massive sands onto the outer shelf (iii) the early transgressive backstepping (?) beach sands, (iii) the late transgressive backslapping parasequences. The sand content inferred from the seismic facies, comforted with the uppermost units facies from data cores, is in agreementmore » with this model.« less