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Bulletin De La Societe Geologique De France | 2005

Conceptual modelling of sand bars morphodynamics for a microtidal beach (Sète, France)

R. Certain; Jean-Paul Barusseau

The sandy littoral of Sete, with its barred shoreface, is one of the three studied sites of the thematic action Morphodynamics of sandy beaches of the French Programme National dEnvironnement Cotier (PNEC), selected because of its microtidal wave-dominated characteristics and of the long time series of available data. During the PNEC program, the principal results obtained show that the morphological evolution of the sedimentary bars can be synthesized according to two conceptual models, in reaction to hydrodynamic variability. (1) The model of oscillation around a position of equilibrium (O.P.E) defines the usual mode of behaviour of the bars, with an alternation of shoreward and seaward movements. The bars migrate seaward during storms and shoreward when the energy conditions decrease. This oscillation is expressed with several rhythms. (i) During the main phases of the bar evolution, which are long periods during which the bars present the same geometrical characters. The passage from one phase to the other occurs when a 4 m significant height storm happens. (ii) At the seasonal scale, which is well illustrated by the behaviour of the inner bar: during summer, when the conditions of agitation are weak, the bar aggregates punctually with the shore; when the conditions of agitation increase in autumn the inner bar is reformed and moved seaward. (2) The model of Net Offshore Migration (N.O.M) points to the tendency of the bars to retreat under the effect of paroxysmal events (storms with a 20 to 50 yrs return time) being a prelude to their degeneration. From the former position of equilibrium, the outer bar strongly moves seaward and drops following heavy swell. Instead of moving to the coast according to the O.P.E model, the outer bar loses material that is recovered by the inner bar and degenerates. The inner bar, exposed to the swell, then moves seaward to replace the initial outer bar, a new inner bar being created at the coast. A few years after, the standard pattern is restored. These results are compared with those described in the literature.


Bulletin De La Societe Geologique De France | 2004

Very high resolution seismic investigation of the sedimentary infill of the Leucate lagoon (Aude and Pyrenees-Orientales - SE France)

R. Certain; Bernadette Tessier; Thierry Courp; Jean-Paul Barusseauet; Henri Pauc

A very high resolution seismic investigation has for the first time allowed the imaging of the sedimentary infill of a Mediterranean lagoon. The Leucate lagoon is part of a lagoon system located along the shore of the western Gulf of Lions, from the Rhone delta to the Spanish border. These lagoons are separated and protected from the sea by sandy barriers, also called lidos, which are the result of a process of shore regularization by waves.nnThe seismic data, obtained by using a boomer-Seistec, coupled with lithological and radiocarbon data [Martin, 1978] previously collected from cores, have revealed three main sedimentary formations : The basal formation represents the substratum of the lagoon and the middle and upper formations its infill. The basal formation displays a very uniform seismic facies with reflectors almost constantly dipping towards the sea. It comprises conglomeratic sediments and is interpreted as a progradating fluvio-deltaic formation. Its upper surface is erosional and is locally deeply incised. In the shallowest parts of the lagoon, where the basal formation almost emerges, its upper part is reworked by modern processes into multiple cut-and-fill structures. The middle formation overlaps the basal formation, and constitutes the main depositional unit of the lagoon fill (up to 20 ms twtt thick). The seismic facies are variable and correspond to sand and clay sediments deposited under fluvio-lagoonal to lagoonal and marine conditions. The upper formation represents the upper part of the infill. It rests above the middle formation through a conformable surface, locally slightly erosional, and overlaps the basal formation along the western rim and in the shallowest parts of the basin. The thickness of this upper formation does not exceed 3mst wtt. It mainly consists of clay sediments of lagoonal origin. The main characteristic of this upper formation is a thin sole of very dense sand at the base. This bed is also a remarkable seismic reflector, and is interpreted as resulting from the maximum marine flooding of the system. This occurs before the beginning of the barrier construction, and the progressive closure of the lagoon. Another remarkable aspect of the upper formation is the simultaneity of its basal part with the lido construction. In this upper unit, the seismic data allow the imaging of the lateral passing between the planar bedded sediments of the infill, with the sigmoidal beds representing washover fans that construct the lagoonal side of the lido. The uppermost part of the formation represents the final and present-day stage of the lagoonal infill since the final closure by the barrier.nnDating, performed on cored sediments, allow the sediments of the basal formation to be assigned to the Middle Pleistocene (with no more precision). The erosion of the top of the basal formation is interpreted as fluvial incision during the last sea level fall. The lagoon infilling is of Holocene age and comprises two stages : the first and main stage corresponds to fluvio- to marino-lagoonal sedimentation, and occurred before 6,000 B.P. The second corresponds to the recent to modern infilling that began around 4,000 B.P. with the construction of the lido and the closure of the lagoon. The two stages are clearly separated by a period of maximum marine flooding. The thickness of the lagoon fill is relatively limited, probably no more than 20 m.


Marine and Petroleum Geology | 2005

Sedimentary balance and sand stock availability along a littoral system. The case of the western Gulf of Lions littoral prism (France) investigated by very high resolution seismic

R. Certain; Bernadette Tessier; Jean-Paul Barusseau; Thierry Courp; Henri Pauc


Bulletin De La Societe Geologique De France | 2010

Late-Holocene evolution of a coastal lagoon in the Gulf of Lions(South of France)

Pierre Sabatier; Laurent Dezileau; Mickaël Barbier; Olivier Raynal; Johanna Lofi; Louis Briqueu; Michel Condomines; Frédéric Bouchette; R. Certain; Ulrich Van Grafenstein; Christophe Jorda; Philippe Blanchemanche


Bulletin De La Societe Geologique De France | 2010

Holocene evolution of a Languedocian lagoonal environment controlled by inherited coastal morphology (northern Gulf of Lions, France)

Olivier Raynal; Frédéric Bouchette; R. Certain; Pierre Sabatier; Johanna Lofi; Michel Séranne; Laurent Dezileau; Louis Briqueu; Pierre Ferrer; Thierry Courp


Journal of Coastal Research | 2011

Typology of nearshore bars in the Gulf of Lions (France) using LIDAR technology

Nicolas Aleman; Nicolas Robin; R. Certain; C. Vanroye; P. Barusseau; Frédéric Bouchette


Bulletin De La Societe Geologique De France | 2010

The Late Holocene sediment infilling and beach barrier dynamics of the Thau lagoon (Gulf of Lions, Mediterranean sea, SE France)

Pierre Ferrer; Massinissa Benabdellouahed; R. Certain; Bernadette Tessier; Jean-Paul Barusseau; Frédéric Bouchette


Geomorphology | 2015

Longshore variability of beach states and bar types in a microtidal, storm-influenced, low-energy environment

Nicolas Aleman; Nicolas Robin; R. Certain; Edward J. Anthony; Jean-Paul Barusseau


Marine Geology | 2014

Post-glacial filling of a semi-enclosed basin: The Arguin Basin (Mauritania)

Nicolas Aleman; R. Certain; Jean-Paul Barusseau; T. Courp; A. Dia


Marine Geology | 2017

Morphodynamics of slightly oblique nearshore bars and their relationship with the cycle of net offshore migration

Nicolas Aleman; R. Certain; Nicolas Robin; Jean-Paul Barusseau

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Henri Pauc

University of Perpignan

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Johanna Lofi

University of Montpellier

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Louis Briqueu

University of Montpellier

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