Changes in facies distribution in the Gironde
estuary (bay of Biscay, SW France) over
the last 30 years
Vasilis Kapsimalis, Laurent Massé, Jean-Pierre Tastet
Université de Bordeaux 1, département géologie et océanographie, UMR-CNRS-EPOC 5805,
avenue des Facultés, 33405 Talence Cedex, France
v.kapsimalis@geocean.u-bordeaux.fr
Abstract
Surface sediment distribution patterns within the Gironde estuary were
investigated through grain size and statistical analysis of 642 surface
samples collected during two campaigns in 1998 and 1999. A comparison
between the present day estuarine facies and those described by Allen
(1972) shows some striking variations, mainly caused by the interplat'
between marine and fluvial processes.
Résumé
La distribution spatiale des faciès sédimentaires de l’estuaire de la Gironde
a été appréhendée à travers l’analyse granulométrique de 642 bennes réalisées au cours de deux campagnes en 1998 et 1999. La comparaison de la
distribution actuelle avec celle observée par Allen (1972) montre quelques
variations frappantes, dues en particulier à l’interaction des apports fluviatiles et des entrées de sédiments d’origine marine près de l’embouchure.
Introduction
The interplay betwœn marine and fluvial processes and the residual sediment transport patterns determine, to a large extent, the morphology and
facies distribution in estuaries. Any modification in the hydrological regime (tide, wave and river discharge) or sediment supply affects the estuarine evolution and alters the previously achieved equilibrium in the ystem (Jouanneau & Latouche, 1981). Contrary to severe human-affected
estuaries, the Gironde estuaty (bay of Biscay, SW France) has two significant advantages for further and in-depth survey: (a) numerous detailed
studies have been carried out since the end of the XlXth century on various
parameters acting in the estuary and determining its specific features; and
(la) human intervention on the drainage basin of the Gironde estuary has
not brought any drasric changes m the equilibrium of the s\ stem.
Material and methods
Grain-size and statistical analyses were performed on 642 surface sediments
collected in the Gironde estuary during the Girosed (May-June 1998) and
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estuary (bay of Biscay, SW France) over
the last 30 years
Vasilis Kapsimalis, Laurent Massé, Jean-Pierre Tastet
Université de Bordeaux 1, département géologie et océanographie, UMR-CNRS-EPOC 5805,
avenue des Facultés, 33405 Talence Cedex, France
v.kapsimalis@geocean.u-bordeaux.fr
Abstract
Surface sediment distribution patterns within the Gironde estuary were
investigated through grain size and statistical analysis of 642 surface
samples collected during two campaigns in 1998 and 1999. A comparison
between the present day estuarine facies and those described by Allen
(1972) shows some striking variations, mainly caused by the interplat'
between marine and fluvial processes.
Résumé
La distribution spatiale des faciès sédimentaires de l’estuaire de la Gironde
a été appréhendée à travers l’analyse granulométrique de 642 bennes réalisées au cours de deux campagnes en 1998 et 1999. La comparaison de la
distribution actuelle avec celle observée par Allen (1972) montre quelques
variations frappantes, dues en particulier à l’interaction des apports fluviatiles et des entrées de sédiments d’origine marine près de l’embouchure.
Introduction
The interplay betwœn marine and fluvial processes and the residual sediment transport patterns determine, to a large extent, the morphology and
facies distribution in estuaries. Any modification in the hydrological regime (tide, wave and river discharge) or sediment supply affects the estuarine evolution and alters the previously achieved equilibrium in the ystem (Jouanneau & Latouche, 1981). Contrary to severe human-affected
estuaries, the Gironde estuaty (bay of Biscay, SW France) has two significant advantages for further and in-depth survey: (a) numerous detailed
studies have been carried out since the end of the XlXth century on various
parameters acting in the estuary and determining its specific features; and
(la) human intervention on the drainage basin of the Gironde estuary has
not brought any drasric changes m the equilibrium of the s\ stem.
Material and methods
Grain-size and statistical analyses were performed on 642 surface sediments
collected in the Gironde estuary during the Girosed (May-June 1998) and
219