The delta plain of the Rhone shows many sandy beach ridges cropping out at the surface. We propose here a radiocarbon chronology for the accumulation of the sedimentary bodies and an interpretation ...of the morphology of the mouth lobes that they form. Morphologies of the lobes depend on four principal factors: (1) the variation of the relative sea level, which constitutes the morphogenic base level, (2) the fluvial input (volume of water discharge and sedimentary input, number and position of the mouths), (3) marine dynamics (volume and direction of the longshore drift, dominant wave direction) (4) the accommodation space created by the rise of relative sea level, along with the paleobathymetry onto which the lobe will prograde immediately in front of the delta and at sea.
Our conclusions are: the main Holocene paleo-delta lobes of Ulmet and Saint Ferréol were contemporaneous, being deposited from 4000 to 2000 yr BP. However, the fluvial style of their downstream channel (meandering for Ulmet channel and linear for Saint-Ferréol) and the lobe morphologies of both channels are contrasted: rounded in the case of Ulmet and elongated for Saint-Ferréol. The role of the accommodation space is confirmed by two recent drillholes traversing the entire Holocene succession, which reveal a prior stage of sedimentary filling in the case of the Saint-Ferréol lobe, thus limiting the accommodation space and favouring a rapid and pointed progradation of this lobe.
The decoupling between hydrological activity and progradation of lobe indicates the complexity of mechanisms in the large catchment basin of Rhône. However, the high rate of progradation of Saint-Ferréol lobe after 2900 BP is probably a consequence of the increase of human activity after this date.
The variation of relative sea level remains an important factor controlling the evolution of the Rhone delta after 6000 BP. The local (?) stabilization of the relative sea level between 4585 BP and 3520 BP played an important role in the triggering of coastal progradation (Saint-Ferréol lobe, eastern margin Rhône delta).
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.
As part of the ECOMARGE operation (J.G.O.F.S. France), macrobenthic assemblages in the Toulon Canyon were described and quantified on the basis of sampling carried out between 250 and 2000
m depth on ...the Mediterranean continental slope. Results show that Mediterranean bathyal assemblages are made up mainly of continental shelf eurybathic species. The qualitative and quantitative composition of populations varies with depth on the slope and also varies with station position at equivalent depth, whether on the flanks or in the canyon channel. Various analyses have provided evidence on the factors responsible for this population distribution pattern. No single factor emerges as predominant, but rather a group of factors, which are related to the nature and origin of sediments and more particularly their grain size distribution, geochemical composition and mode of transportation and sedimentation (benthic nepheloid or originating from the water column), act in conjunction to determine the pattern. Comparison with ocean continental slopes shows that in the Mediterranean Sea the absence of tidal current modifies the trophic structure of the macrobenthic assemblages, which are characterized by a dominance of surface and subsurface deposit feeders as compared to a dominance of suspension feeders and carnivores in the upper and median part of the slope in the ocean. Surface dumping of dredge spoil at the canyon head and channelling of waste induces an increase of organic matter and pollutant concentrations in sediment from the upper part of the canyon channel but does not give rise to any marked population degradation.
Les récentes opérations d’archéologie préventive ont profondément renouvelé la connaissance du centre ancien de Marseille et des quartiers suburbains peu à peu intégrés à ta cité Ainsi les fouilles ...dont rend compte cet ouvrage, réalisées en 1992-1993 à proximité du Vieux Port et de la Canebière ont elles révélé quantité d’informations médites sur les aménagements du rivage depuis le IVe s av. J-C jusqu’à l’installation de salines au haut Moyen Âge. puis sur la mise en place du paysage périurbain au-delà de la fortification du Plan fourmiguier Liés à la fondation d‘édifices comme l’hôpital du Saint-Sépulcre, plusieurs flots constituent peu à peu le faubourg Sainte-Catherine, à caractère essentiellement agricole, qui est totalement rasé vers 1360 Intégré a la ville en 1670, cet espace se reconstruit au XVIIIe s après la création de la rue Paradis le nouvel flot est démoli au début du XIXe s pour la création de l’actuelle place du General-de-Gaulle, élément structurant de l’urbanisme moderne de Marseille.
Résumé L'analyse stratigraphique et la présence de vestiges immergés à Fos ont permis d'identifier cinq lignes de rivage depuis 6500 В P. L'étude d'indicateurs bathymétriques (faunistiques et ...sédimentologiques) sur les substrats meubles du Golfe de Fos et leur comparaison avec la courbe établie sur substrat rocheux en Provence et en Corse par J. Laborel (1994) ont mis en évidence des mouvements tectoniques verticaux négatifs évalués à 0,01 mm/an et 0,37 mm/an depuis 4000 BP, et à 0,2 mm/an et 0,5 mm/an depuis le Ier siècle. Ces mouvements du sol semblent induire une réponse sédimentaire, à partir de 6120 ± 55 BP et après 2100 BP ± 45, qui semblerait indiquer l'apport d'un exutoire du Rhône se rapprochant du golfe de Fos.
Abstract Stratigraphie analyses and the presence of submerged ruins at Fos have allowed the identification of five coastlines dating from 6500 В P. The study and comparison between bathymétrie indicators (faunistic and sedimentological) from sandy substrates in the Gulf of Fos and the curve obtained on rocky substrates of Provence and Corsica by J. Laborel (19941 indicate tectonic movements evaluated at 0.01 mm/yr and 0.37 mm/yr since 4000 BP, and 0.2 mm/yr and 0.5 mm/yr since the first century AD. These ground movements seem to have caused sedimentary influxes since 6120 ± 55 BP and after 2100 ± 45 BP, which would suggest that one of the mouths of the Rhône was closer to the Gulf of Fos.
Since 1965, macrobenthic communities have been studied in the area surrounding the sewer outfall of Marseille, France. The polluted zone increased by a factor of 3 and the subnormal zone increased by ...a factor of 10 between 1970 and 1980. After construction of a primary treatment plant in 1987, the macrobenthos of the polluted zone decreased significantly in terms of number of individuals. This decrease was apparently caused by a reduction of organic matter discharged to the sea and was particularly notable near the discharge. However, composition of communities began to change in 1992 to 1993. Benthic samples taken at depths of 35, 39, and 51 m in July 1994 and January 1995 indicated a recovery of parts of a polluted zone to a community resembling the subnormal zone. Most notable is the disappearance of species indicative of the polluted zone at stations H3 and H4 and the decrease at station 17 (nearest the outfall). Also, sentinel species of the subnormal zone and species characteristic of the unpolluted zone increased in number. The study demonstrated a complete change of communities at stations 17 and H4 between 1990 and 1994. Communities at these two stations, both near the sewer outfall, are characteristic of the subnormal zone. The community at station H3 that belonged to the subnormal zone displayed a degree of structural stability. These changes in benthic populations indicated that construction of the primary treatment plant reduced contamination in the area and may lead to recovery of the benthos in this region.
Le programme de recherches paléo-environnementales du Centre d’études alexandrines a pour objectif de préciser les dynamiques géomorphologiques des littoraux d’une des plus grandes cités portuaires ...antiques de Méditerranée : Alexandrie d’Égypte. Plusieurs campagnes de carottage et des prospections en scaphandre autonome ont permis d’identifier six principales étapes dans l’évolution des paysages. (1) Un tombolo, établi entre l’île de Pharos et le futur site d’Alexandrie, se développe dès le début du ive millénaire. (2) Au moment de la fondation d’Alexandrie, le tombolo devient semi-émergé. L’Heptastade, chaussée de près de 1300 m de long reliant l’île et la cité, est alors construit sur la partie sommitale de ce tombolo et non sur une accumulation massive de remblais. (3) À partir de la période Romaine, on assiste à une progradation des plages et au comblement progressif des bassins portuaires. (4) Durant l’Antiquité Tardive et le début de la période Arabe, un ou plusieurs tsunamis provoquent une ingression marine brutale par érosion des plages. (5) La progradation des rivages reprend rapidement en raison d’un important stock sédimentaire grossier disponible provenant des destructions occasionnées par le ou les tsunamis. (6) Vers les viiie-ixe siècles après J.-C., une hausse du niveau marin relatif de 5,5 ± 1 m est enregistrée. Les raisons de cet enfoncement soudain sont encore mal connues. Enfin, la progradation des plages reprend progressivement au cours de l’époque arabe, puis ottomane.
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