Changements côtiers holocènes le long de l’estuaire de la Gironde : nouvelles données à partir du système plage/dune de la péninsule du nord‑Médoc
ARNAUD-FASSETTA, Gilles
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG (UMR_8586 / UMR_D_215 / UM_115)]
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Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG (UMR_8586 / UMR_D_215 / UM_115)]
ARNAUD-FASSETTA, Gilles
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG (UMR_8586 / UMR_D_215 / UM_115)]
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG (UMR_8586 / UMR_D_215 / UM_115)]
BERTRAND, Frédéric
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG]
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG]
CULIOLI, Camille
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG (UMR_8586 / UMR_D_215 / UM_115)]
Pôle de recherche pour l'organisation et la diffusion de l'information géographique [PRODIG (UMR_8586 / UMR_D_215 / UM_115)]
BERTRAN, Pascal
De la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie [PACEA]
Institut national de recherches archéologiques préventives [Inrap]
< Reduce
De la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie [PACEA]
Institut national de recherches archéologiques préventives [Inrap]
Language
en
Article de revue
This item was published in
Quaternaire. 2019, vol. 30, n° 1, p. 47-75
AFEQ-CNF INQUA
Abstract
L’Amélie beach is located near the mouth of the Gironde estuary (south-western Atlantic coast of France). It has been greatly eroded by recent storms, especially in the winter of 2013-2014. Erosion of the dune front and ...Read more >
L’Amélie beach is located near the mouth of the Gironde estuary (south-western Atlantic coast of France). It has been greatly eroded by recent storms, especially in the winter of 2013-2014. Erosion of the dune front and beach has uncovered a set of estuarine and aeolian sediment deposits containing numerous archaeological remains. A campaign of topographic surveys was undertaken with DGPS and TLS equipment during the springs of 2014 and 2015 along the 2 km length of L’Amélie beach in order to reconstruct the elevation and stratigraphy of these deposits. Sedimentological analyses (grain size, micro-faunal) were performed to better constrain the depositional environment. Archaeological remains and several radiocarbon dates obtained from sediment samples collected in the field were used to propose a consistent chronological framework for this sedimentary sequence. Ten main lithofacies were distinguished from the lower part of the beach to the top of the dune. The base of the sedimentary sequence is composed of Pleistocene deposits dating from MIS 9 (unit 1a) to MIS 2 (unit 1b) (Bosq et al., 2019). The Holocene sedimentary infilling began around 5000 BC with an accumulation of coarse marine sands, which suggests the presence of a tidal inlet. On both sides of this tidal channel, archaeological remains dating from the early Neolithic period up to the Bronze Age testify to a human occupation of the coastal area. From ca. 5000 to ca. 3500 cal. a BP, a characteristic deposit of intertidal mudflats indicates the transformation of the tidal inlet into estuarine marshes protected by a coastal dune barrier. Between ca. 3500 and ca. 3000 cal. a BP, the dune barrier records a phase of erosion resulting in the exposure of the marsh to stronger hydrodynamic conditions. From ca. 2800 to 1650 cal. a BP, a second phase of estuarine sedimentation is recognized. This period is characterized by significant human occupation as indicated by the presence of numerous archaeological remains of the Iron Age and Gallo-Roman periods, associated with the exploitation of a saltwater-to-brackish environment. From 1650 to 1250 cal. a BP, the estuarine salt marsh is gradually overrun by northward migrating coastal-dune fields. After 1250 cal. a BP, the marsh is completely covered by aeolian sands. These results are consistent with previously published data and allow us to detail the local sequence of palaeogeographic changes of the north-Médoc peninsula. Using the ‘sea-level index points’ method (Hijma et al., 2015), the analysis of radiocarbon dated levels also provides new relative sea level records for this part of the French Atlantic coast. Finally, the phases of coastal dune activity/stability recognized along L’Amélie beach are synchronous with those in the wider Aquitaine coastal region, suggesting a regional driving factor. We propose that the shared sedimentary dynamics are the consequence of the onshore migration of intertidal and subtidal sand banks distributed at the mouth of the Gironde.Read less <
English Abstract
L’Amélie beach is located near the mouth of the Gironde estuary (south-western Atlantic coast of France). It has been greatly eroded by recent storms, especially in the winter of 2013-2014. Erosion of the dune front and ...Read more >
L’Amélie beach is located near the mouth of the Gironde estuary (south-western Atlantic coast of France). It has been greatly eroded by recent storms, especially in the winter of 2013-2014. Erosion of the dune front and beach has uncovered a set of estuarine and aeolian sediment deposits containing numerous archaeological remains. A campaign of topographic surveys was undertaken with DGPS and TLS equipment during the springs of 2014 and 2015 along the 2 km length of L’Amélie beach in order to reconstruct the elevation and stratigraphy of these deposits. Sedimentological analyses (grain size, micro-faunal) were performed to better constrain the depositional environment. Archaeological remains and several radiocarbon dates obtained from sediment samples collected in the field were used to propose a consistent chronological framework for this sedimentary sequence. Ten main lithofacies were distinguished from the lower part of the beach to the top of the dune. The base of the sedimentary sequence is composed of Pleistocene deposits dating from MIS 9 (unit 1a) to MIS 2 (unit 1b) (Bosq et al., 2019). The Holocene sedimentary infilling began around 5000 BC with an accumulation of coarse marine sands, which suggests the presence of a tidal inlet. On both sides of this tidal channel, archaeological remains dating from the early Neolithic period up to the Bronze Age testify to a human occupation of the coastal area. From ca. 5000 to ca. 3500 cal. a BP, a characteristic deposit of intertidal mudflats indicates the transformation of the tidal inlet into estuarine marshes protected by a coastal dune barrier. Between ca. 3500 and ca. 3000 cal. a BP, the dune barrier records a phase of erosion resulting in the exposure of the marsh to stronger hydrodynamic conditions. From ca. 2800 to 1650 cal. a BP, a second phase of estuarine sedimentation is recognized. This period is characterized by significant human occupation as indicated by the presence of numerous archaeological remains of the Iron Age and Gallo-Roman periods, associated with the exploitation of a saltwater-to-brackish environment. From 1650 to 1250 cal. a BP, the estuarine salt marsh is gradually overrun by northward migrating coastal-dune fields. After 1250 cal. a BP, the marsh is completely covered by aeolian sands. These results are consistent with previously published data and allow us to detail the local sequence of palaeogeographic changes of the north-Médoc peninsula. Using the ‘sea-level index points’ method (Hijma et al., 2015), the analysis of radiocarbon dated levels also provides new relative sea level records for this part of the French Atlantic coast. Finally, the phases of coastal dune activity/stability recognized along L’Amélie beach are synchronous with those in the wider Aquitaine coastal region, suggesting a regional driving factor. We propose that the shared sedimentary dynamics are the consequence of the onshore migration of intertidal and subtidal sand banks distributed at the mouth of the Gironde.Read less <
Keywords
dune
estuaire
vasière
marais maritimes
Holocène
hausse du niveau marin
ensablement éolien
TLS
Gironde
Aquitaine
English Keywords
Aquitaine
Gironde
TLS
aeolian sand drift
sea-level rise
salt marsh
mudflat
dune
estuary
Holocene
ANR Project
Using the world in ancient societies : processes and forms of appropriation of space in Long Time - ANR-10-LABX-0052
Initiative d'excellence de l'Université de Bordeaux
Initiative d'excellence de l'Université de Bordeaux
Origin
Hal imported