Tesson M.,GD ARGO |
Tesson M.,University of Perpignan |
Labaune C.,GD ARGO |
Gensous B.,GD ARGO |
And 7 more authors.
Journal of Sedimentary Research
A buried system was observed using seismic data along the northern side of the Roussillon coastal plain and inner shelf (Western Gulf of Lion, Mediterranean Sea) far from the nearest Agly and Tet rivers. It was interpreted as an example of a "compound" type, which is subject to controversy. A core 60 meters long was obtained on the sandy beach barrier between sea and lagoon approximately on the axis of the basal surface of erosion mapped from seismic data and long core logs obtained previously on the coastal plain. In the lower part of the core (-64 m to-26 m b.p.s.l.) the main estuarine muddy-silt facies and thin levels of fluvial gravels intercalated in the mud suggest that successive cycles of base-level and sea-level falls and rises were recorded. This interpretation is confirmed by pollen diagrams showing several successive warming periods during climatic changes (differentiated as " interglacial" phases) recorded by the estuarine muds. Owing to these correlated data we can attest that this incised-valley system is of a "compound" type. Every vertical succession of fluvial gravels and estuarine muddy silts represents a fundamental depositional sequence typical of the "simple" model of wave-dominated incised-valley filling, truncated at the top by a subsequent base-level fall. Several depositional sequence remnants are stacked upon each other. The chronostratigraphic benchmark is based on microforaminiferal biomarkers which indicate that the time period covered by the successive phases of base-level and sea-level cycles extends from MIS 16 (about 600,000 years B.P.) to MIS1 (present day). The exact correlation of base level and sea level cycles with identified climate cycles remains partly approximate, but the cycles which contain well-known plant associations are quite reliable. The internal geometry of the incised-valley system, based upon high-resolution seismic data, shows that the lateral migration of the successive phases of incision and filling explains both the preservation of several cycles and the incomplete preservation of the typical facies due to the reworking of the upper part of all individual depositional sequences. Eustasy is the dominant controlling factor, and differential subsidence, an important factor on the mid and outer shelf, has a reduced impact at this location. The preservation of the "compound" system depends upon the variable maximum depth of erosion reached at each maximum sea-level lowstand. We propose that different interglacial conditions took place in the drainage basins, rather than differences in the lowstand-sea-Ievel values. The transverse shape of the incisions, with lateral terraces and deeper channels, combined with a continuous lateral shift of the successive incisions, also contributed to preservation. The lateral shifting is partly due to a normal fault and substratum tilting, and partly to the oceanic regime. Copyright © 2011, SEPM (Society for Sedimentary Geology). Source
Marchand M.,Deltares |
Sanchez-Arcilla A.,Polytechnic University of Catalonia |
Ferreira M.,Mediterranean Center |
Gault J.,University College Cork |
And 7 more authors.
Ocean and Coastal Management
The main objective of the Conscience project was to develop and test concepts, guidelines and tools for the sustainable management of erosion along the European coastline, based on the best available scientific knowledge and on existing practical experience. Four concepts are potentially capable of providing the nexus between scientific knowledge and management: coastal resilience, coastal sediment cell, favourable sediment status and strategic sediment reservoir. The project has tested the use of these concepts and found that they are useful, provided that they are positioned and linked within a logical structure that we shall call the Conscience " Frame of Reference" , defined in time and space and supported through data and monitoring. Practical experience in six coastal sites in Europe has shown that the use of this Frame of Reference together with these concepts can make management objectives explicit and transparent. It can therefore support the design of an appropriate, resilience based coastal erosion management practice. © 2011 Elsevier Ltd. Source
Lardeaux J.-M.,University of Nice Sophia Antipolis |
Munch P.,Montpellier University |
Munch P.,Aix - Marseille University |
Corsini M.,University of Nice Sophia Antipolis |
And 10 more authors.
Bulletin de la Societe Geologique de France
In this paper we present and discuss new investigations performed on both the magmatic basement and the sedimentary formations of La Désirade. We report structural and sedimentary evidences for several episodes of deformation and displacement occurring prior to the present day tectonics. The main faults, respectively N130 ± 10°, N040 ± 10° and N090 ± 10°, previously considered as marker of the current tectonic regime corresponds to reactivated tectonic structures developed first during late Cretaceous compression and second during Pliocene to early Pleistocene extension. We demonstrate also the importance of late Pliocene-early Pleistocene and middle-late Pleistocene vertical movements in this part of the Lesser Antilles fore-arc as well as the role of compressive tectonics in the over thickened character of the arc basement in the Guadeloupe archipelago. Source
Dalibard M.,GeoBioStratData Consulting |
Popescu S.-M.,GeoBioStratData Consulting |
Maley J.,Montpellier University |
Baudin F.,CNRS Institute of Earth Sciences |
And 6 more authors.
The essential characteristics of the vegetation dynamics of tropical Africa remain only partially known. This study assesses the succession of vegetation-types over Central Africa during the last two glacial/interglacial cycles. Analysis of core KZai02, which contains pollen from the Zaire River watershed (latitudes 9°N-13°S), allows the investigation of long-term patterns of plant ecosystem development and their climatic causes. Core KZai02 (18.20m long) was recovered from 6°24.20'S/9°54.10'E in the uppermost axial edifice of the Zaire deep sea fan. The chronology of this sedimentary archive was established using nannofossils and correlations of pollen and total organic carbon signals with the nearby core GeoB1008. The pollen record indicates that: (i) glacials (MIS 6, 4, 2) are marked by the development of afromontane (Podocarpus) forest at high altitudes when central basin lowlands were occupied by Cyperaceae marshes and savannah; (ii) during interglacials (MIS 1, 5) lowland forests were developed, marked by the successive expansion of pioneer, warm-temperate, rain forests, and mangrove indicating sea-level rise; (iii) glacial-interglacial transitions (MIS 6/5, 2/1) display similar vegetation dynamics. The strong evidence of afromontane forest and the opening of the vegetation during glacials suggest a reduced latitudinal distribution of rainfall by the strengthening of the trade wind system. West African monsoon systems were enhanced during interglacials, allowing the progressive development of lowland forests. The development of rain and pioneer forests during glacial Heinrich stadials suggests an enhancement of water availability in tropical Africa associated with these high-latitude events. However, no augmentation of wind activity described by previous studies is evidenced by our pollen record. Similar vegetation successions during glacial/interglacial transitions suggest the diachronous and stepped intervention of CO2 (emphasizing the influence of temperature on plant ecosystems) and water availability. © 2014 Elsevier Masson SAS. Source
Lericolais G.,French Research Institute for Exploitation of the Sea |
Guichard F.,CEA Saclay Nuclear Research Center |
Morigi C.,Geological Survey of Denmark |
Minereau A.,Asterie |
And 2 more authors.
The north-western Black Sea shelf is the widest continental shelf of the Black Sea, where the Danube delta/prodelta system includes important records on the Black Sea water level fluctuations. This study integrates newly acquired high-resolution single channel seismic reflection profiles and Calypso piston cores recovered along a transect extending from the Danube delta deep into its deep sea fan. The correlated results provide information on the Late Quaternary architecture of the Danube Black Sea shelf and on the role of global glacio-eustatic fluctuations on the building of the Danube delta/prodelta. The sedimentary sequences in the Black Sea are strongly affected by water level changes. For the whole duration of Late Glacial-Holocene period, the level of the Black Sea was controlled by the regional climate modifications rather than the global eustatic changes. The seismic sequences recognized on a very high-resolution seismic profile were dated by two Calypso piston cores. Based on the obtained data, during the Last Glacial Maximum the Black Sea was a land locked lake with the level below -120 m. In the course of the deglaciation the lake level rose up to -40 m, which is confirmed by occurrence of the prodelta lobes formed after the rise in water level originated from the melt water. Following the Younger Dryas, 11 000-8500 14C BP, there occurred a new level lowering to the level of -100 m, identified by the forced regression deposits recorded on the Romanian shelf. This last lowstand previously recognized by a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes is also indicated by the prodelta at -100 m depth. All these coastal features as well as the incised anastomosed channel system remained preserved on the shelf resulting from a rapid ultimate transgression starting immediately after 8500 14C BP. © 2010 Elsevier Ltd and INQUA. Source