Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

PALAEO-ENVIRONMENTAL STUDY AREA P17

THE ATLANTIC COAST, NORTH MÉDOC, FRANCE

Plate P17 Palaeo-environmental investigations on the shore near Soulac-sur-Mer, Atlantic Coast, France

LOCATION

Geographical description (Figure P17.1)

The Aquitaine coast (Plate P17) is a 240 Km long low coast, bordering the Bay of Biscay in southwestern France. Between the mouth of the Gironde Estuary, in the north, and the mouth of the Adour river, in the south, this represents 5% (and the least protected part) of the total length of the French coastline. The coast is bordered inland by a forested complex of Holocene dune systems, isolating several coastal lakes. This long beach-dune sandy barrier is only interrupted by the inlet of the Arcachon lagoon and, towards the south, by the mouths of minor channels draining coastal lakes and know locally as "courants".

The area of land containing the dunes is known as ‘’Les Landes de Gascogne’’. The distribution of dunes differs along the coast. In the north crescentric or barchan dunes are dominant, whilst parabolics occur in the centre and increase in importance towards the south. All the dunes formed under a predominant wind direction of 280 N.

Historical records show that the rates of erosion vary along the Atlantic coast, ranging from 1,0- 2,0 meters per years in the northern part of the area (5-10 meters per years close to the Gironde mouth), to 0,2-1,0 meters per years in the southern section.

1.2 Coastal description

The northern part of the Aquitaine Coast is the a continuous sandy coast, bordered by linear foredune which is maintained artificially by the Forestry Service (O.N.F-Office National des Forêts).

1 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

The Gironde coast is formed by two linear sedimentary cells, of differents orientations. Between the Cape of Pointe de La Négade and the Pointe de Grave, the orientation of the coast is N55°; between Pointe de La Négade and the Cap Ferret spit, the coast is orientated approximately N- S (N7°).

We focussed our studies on the north of the Atlantic Coast between Pointe de Graves and the Hourtin lake (Figure P17.1).

1.3 Regional Authority

Conseil Régional d' Aquitaine, Conseil General de Gironde. Towncouncil of: Le Verdon-sur- Mer, Soulac-sur-Mer, Grayan-et-L'Hopital, Vensac, Vendays-Montalivet, Naujac-sur-Mer and Hourtin.

1.4 Designation (protected areas)

IGN map, 25 000e, 1433 OUEST and 1434 OUEST.

2. MODERN HUMAN GEOGRAPHY

The french Aquitain coast is one of the Europe's less populated regions (348,000 people). However, as a tourist attraction there is an average increase of the population of more than 150% during July and August : some of the smaller town, such as Soulac-sur-Mer, can see their population multiplied by 10. The littoral zone is strewn with isolated bathing stations most often seetled on the foredune; consequently, these stations are especially sensitive to changes in the shoreline position.

The cities surrounding this study area are seaside resorts. Their winter population are respectively: Le Verdon-sur-Mer, 1 274; Soulac-sur-Mer, 2 720; Grayan-et-L'Hopital, 728; Vensac, 694; Montalivet, 1 827; Naujac-sur-Mer, 631; Hourtin, 2 323.

3. CONTEMPORARY COASTAL PROBLEMS: (DUNE MOVEMENT, EROSION, ACCRETION; I.E. COASTAL CONTEXT) (Appendix P17.2)

The macrotidal (2-5 m range) Gironde coast, situated to the south of the Gironde estuary, is dominated by N-W swell. The predominent cape Pointe de la Négade separated two linear sections of this coastline, with different orientations and different dynamic settings: a northern section, dominated by a maximum resultant northerly longshore drift (4000,000m3 /yr); and the southern section by a 630,000 m3 /yr southerly drift.

Presently, sediment movements along the Gironde coast are considered to be the results of the combined action of:

1. longshore drift removing sediment and transporting it alongshore 2. aeolian transport 3. onshore-offshore exchange, between the shore and the nearshore zone and connected with the sight increase of sea level.

A synthesis of numerous studies allows erosion over (at least) the past 37 years to be estimated; for certain sections for the past 200 years. The average rate of erosion decreases on both side of the Pointe de La Négade, where it reached the maximum between 1957-1994 (7.3 m/yr). The northern section, protected by dykes and sea defences between the estuary mounth at Pointe de La Négade and Soulac, has been stabilised. Today, only the limited area of the Huttes is not protected and is subjected to erosion of 9.6 m/yr; it is an area of great concern. To the south, the average rate of erosion decrease rapidly-it reached 0.4 m/yr in Montalivet-and then was relatively constant around 1 m/yr as far as the Grang-Crohot. The

2 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

extremity of the Cap Ferret spit has been generally accreting to seawards; it also has extended to the south, for the past 200 yeras. Since 1970, the tip of the spit has undergone erosion.

Erosion of the Gironde coast results from a sedimentary budget in deficit by some 350,000 m3/yr escarping northward (the difference between the northely longshore drift (400,000 m3/yr) and 50,000 m3/yr retained in the system by the process of erosion/accretion of the Huttes beach and St Nicolas sandbank) and 630,000 m3/yr transported toward the south. Aeolian loss appears minimal and offshore loss, due to relative sea-level rise, is estimated to be between 600,000 and 900,000 m3/yr. The system receives no fluvial supply of sand and the primary source of sediment originates from coastal erosion, mobilised by longshore drift. Total sediment loss for the Gironde coast ranges between 1,580,000 and 1,880,000 m3/yr; this explains the average erosion rate, of between 1 and 2 m/yr. Whilst the longshore transport is quite well known, the onshore/offshore movements, especially those caused by the present-day sea-level rise and/or aeolian action, are still poorly understood and require further investigation.

4. KNOWLEDGE, HISTORY, ARCHAEOLOGICAL AND PALAEO-ENVIRONMENTAL SETTING OF THE COASTAL COMMUNITY

4.1 Sedimentological and Palaeo-environmental data concerning the study area

Along the Aquitaine coast aeolian sand dunes cover an area from 0.2 to 10 km wide, and enclose several large coastal lakes (Figure P17.1). The only previous stratigraphic and cartographic work on the sandy dune system in this region was carried out by the B.R.G.M. (Bureau de Recherches Géologiques et Minières - Marionnaud, 1972; Dubreuilh and Marionnaud, 1973). They divided the dune complex into four systems on the basis of morphology. These generations are orientated in a linear pattern along the coast with the oldest located furthest inland and the youngest near the present littoral zone (Figures P17.2 and P17.3). Assuming that the dunes stretched beneath each other to the coast where they were exposed as overlying sand units separated by paleosols, in which only three dates were available: 5100, 3000 and 2300 B.P.. Dubreuilh (1971) suggested the age of the dunes from east to west as follow:

(i) Meso- to Neolithic dune system (Boreal to Atlantic) constituted by isolated barchans or barchanoid ridges. This dune system disappears just to the north of Hourtin lake and is absent to the south of the Medoc peninsula. The system was considered to be older than 5100 B.P. based on a date obtained from a peat, outcropping on the present day coast beneath the foredune, considering it as a "lateral equivalent" of the base of the dune system (Dubreuilh, 1971). (ii) Proto-historic dune system from Copper Age to Bronze Age (Subboreal to the early Sub- Atlantic) constituted by parabolic dunes and interpreted as moving between 5100 and 3000 B.P.. (iii) Historic dune system, constituted by barchanoid dunes, found only in localised areas in north Medoc near Soulac and to the south seaward of the lake of Hourtin. This system was interpreted as a sand sheet formed between 3000 and 2300 B.P., and covered by dunes moving from this time until the 19th century. (iv) Present day littoral dunes, forming an artificial barrier several hundred metres wide along the coast. These were established in the middle of the last century to protect the recently planted pine forests further inland.

The morpho-chronology of Dubreuilh (1971), Marionnaud (1972), and Dubreuilh and Marionnaud (1973) although apparently rigorous, shows a number of problems when examined more closely. Firstly, the authors do not explain the east-west succession of parabolic-barchan- parabolic-foredune forms found to the west of Hourtin lake. Secondly, to the north of Hourtin Lake, similar barchanoid dunes are interpreted as belonging to two different generations: Meso- Neolithic and Historic. Finally, the cartography and morphological description of Marionnaud (1972) and Dubreuilh and Marionnaud (1973) does not correspond with old maps and historical

3 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

records (Masse, 1707; Belleyne, 1762; Cassini, 1798; Buffault, 1942; Bressolier et al., 1990; Froidefond and Prud'homme, 1991; Barrere, 1992). These records show that dunes in many areas in north Medoc were classified as being active before 5100 B.P. or from 5100 to 2300 B.P. (Marionnaud, 1972; Dubreuilh and Marionnaud, 1973), but were in fact mobile during the last century. Additionally, the historical evidence shows the existence of a first generation of parabolic dunes stabilised before the last century. They are therefore the oldest dunes in the area. The work of the cited authors fails to recognise this system of dunes, including within the Meso-Neolithic dune generation, defined as being constituted by barchan forms alone.

New studies based on a number of paleosols and on OIRSL datings have confirmed the existence of only two generations of dunes which are constitued by six different dune types. The first of this generation is termed ‘’primary ‘’ and consists of a coalescent parabolic dunes which were naturally fixed by vegetation before the invasion by the ‘’recent ‘’ dunes some time before the last century. The second system is termed ‘’modern ‘’ and consists of: simple barchans, isolated compound barchanoid ridges, a coalescent field of compound barchanoid ridges, simple parabolics and compound digitate parabolics; were active between 200 BP.

4.2 Archaeological data concerning the study area: a synthesis of human occupation along the Atlantic coast (Appendix P17.1 and Figure P17.4)

The coastal history of North Medoc is one of progressive erosion on which only the past 37 years allow a precise estimation. For the previous periods, the use of old cartographic evidence may give some ideas on the natural changes but not enought precise before the 18th A.D.

The archaeological data are more revealing. The earliest known occupation belongs to the Epipalaeolithic (Azilian) probably circa 11 000 years B.P. (flints recovered during the 19th century from now destroyed sites in Soulac-sur-Mer and Grayan "Le Gurp").

Mesolithic communities had established at La Lède du Gurp and some other sites along the present coastline of North Medoc from the end of the Xth century B.P. (uncalibrated). At La Lède du Gurp the mesolithic flint industries were associated with wood and plant remains (acorns and hazelnuts) and animal foot prints (mainly deer and aurochs).

The establishment of the first farmers of the Neolithic is documented at L'Amélie and La Balise (Soulac-sur-Mer) and La Lède du Gurp as early as 6420 years B.P. onwards.

The human settlement of the coastal part of Medoc continued during the Middle Neolithic. In the Anse du Gurp (Gurp Bight) in the 80's the coastal erosion destroyed a megalithic barrow. Human bones of roughly the same period were excavated from a ditch at La Lède du Gurp. For the Late Neolithic out of the main site at La Lède du Gurp several finds and a scatter of stone artefacts and pottery sherds have been recovered in a large area of the coast from La Glaneuse in the North to Dépée in the South. At l'Amélie in the intertidal area a structure made of wood and big limestone pebbles have been rapidly observed. It could be a burial and has been 14C dated around 4770 years B.P.

For the Beaker period an interesting information has been gained: three tanged copper daggers, several copper Palmela points (casual finds on the beach from Soulac to Montalivet) and an occupational level at La Lède du Gurp.

For the Bronze Age the early and middle periods are particulaly well documented in the North Medoc coast. The occupation continues at La Lède du Gurp. All around the site aeolian erosion brought to light a cultivated area (traces of ploughing). The bronze metallurgy was practised at that time as testified by broken crucibles, pieces of slag and stone and clay moulds. On the beach at l'Amélie as a consequence of defensive works against coastal erosion a very important series of bronze hoards were successively found from 1993 to 1995. 73 bronze axes (mostly of the flanged medocain type), copper ingots and 5 spirals of gold wire. One part of these artifacts was found in pots of which 3 could be recovered, other pots had been destroyed by the engines and the waves. A scatter of other bronze implements has been recorded in this

4 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

area (from La Glaneuse to l'Amélie). At l'Amélie a wooden structure in the intertidal zone have been rapidly observed. It has been 14C dated around 3470 years B.P.and could be an Early Bronze Age burial structure. Another EBA burial was discovered in the section of the sandy cliff at La Négade. The burnt bones of a young adult had been deposited in a basket or mat whose burnt remains were buried in a shallow pit. There were no associated finds but the chronology of the bones is established by a 14C datation.

By contrast, the Late Bronze Age is poorly represented in the whole area as well as the beginning of the Early Iron Age. The situation changes again around theVIth century B.C. At that time the coastal area is densely occupated. One of the main reasons should be the development of salt making (briquetage). The main site is again La Lède du Gurp but other secondary sites have been observed at La Glaneuse and l'Amélie. On the same sites traces of domestic activities, pottery and sometimes animal bones have been reported. At La Léde du Gurp fossilised landscape has been evidenced with plough marks and tracks of the foot prints of domestic cattle and horses. In the immediate vicinity the regression of the coastal sandy cliff caused the discovery of a burial urn with its cover.

During the Late Iron Age a substantial coastal community is established in the same area. Salt extraction is practised in roughly the same locations as before without any important modifications in the processing and the manufacturing implements. There is a general trend an enlargment of the trade network testified by imported goods : amphorae of Greco-italic and Dressel Ia types, vessels imported from the Mediterranean and/or copies. Coins have been found at many places in the coastal area of Medoc : rare golden statères and less unfrequent silver coins mostly of the "à la croix" type. A hoard of such coins was found at l'Amélie in the 60's. On the same beach at l'Amélie wooden structures appear sporadically as a results of coastal erosion or storms. They consist mainly in upright posts in rows and alignments. Some other features have been observed particularly a piece of carved wood. The top represents human face. It was found laying on the beach but after the discoverer it was a part of a quadrangular wooden structure. Two mortices on each sides of the "statue" may confirm this statement.

5. THE ARCHAEOLOGICAL AND PALAEO-ENVIRONMENTAL POTENTIAL

5.1 Sedimentological and Palaeo-environmental Results

Morpho-chronology of coastal dune in the North Médoc

The mapping and establishment of the stratigraphy and the chronology of the dune systems of the coastal zone of the North Médoc were based essentially upon the morphology of the dunes. Three 14C dates were obtained from palaeosols, intercalated in dune sands which were exposed on the eroding coastline: 5100, 3000, 2300 yrs BP. Until now, these were the only dates used in the palaeogeographical reconstitution of this coastal Holocene landscape.

Recent fieldwork, confirmed by a number of new dates and by a reanalysis of historical data, makes it possible to propose a different interpretation of the dune morphology and chronology. Also, a new morphological classification of the coastal dune systems is proposed.

From the morphological point of view, the dunes of North-Médoc are crescentic dunes, which are isolated or arranged in ridges or coalescent ridges. They can be divided into barchanoid and parabolic types which occur as six different dune forms: 1) simple parabolic dunes (sometimes isolated), 2) compound digitate parabolic dunes, 3) coalescent compound climbing parabolic dunes, 4) simple barchans, 5) isolated compound barchanoid ridges, 6) coalescing compound barchanoid ridges.

From the chronological point of view, a new classification is proposed, reviewing and modifying the work of Buffault (1942). The Aquitaine coastal dunes consist of two major transgressive dunefields: primary dunes which were fixed by the natural development of pine forest and the

5 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France modern dunes, which were active until the beginning of the 19th century, when they were stabilized by planting of maritime pines.

Aims and Methods

The aim of this study is to propose a new chronology and topography description for the dune systems found in Medoc thanks to new observations and datations (OIRSL dates).

The interpretation represents a refinement of the one suggested by Pontee et al. (1997) which was based on the chronology and classification given by the B.R.G.M. (Marionnaud, 1972; Dubreuilh and Marionnaud, 1973). The new study is based upon:

(i) a more thorough study of dune morphological types and distribution based upon the 1/25000 topographical maps of the I.G.N. (the French Geographical Institute), (ii) a re-analysis of a previous work by Buffault (1942), historical records, and a number of old maps, particularly those of Belleyne (1762) and Cassini (1798), (iii) a number of dated paleosols exposed along the Medoc coast, or inter-stratified in the Pyla Dune. Although the Pyla Dune is located 70km to the south of the Medoc peninsula its paleosols represent major periods of forest development bounding important periods of increased aeolian activity. (iv) we received lately, after the elaboration of this document, the results of new OIRSL datings which will contribute to modify our interpretation of the chronology of the aeolian period undergone by the Aquitaine Coast during the last 4 000 yeras.

Results

Dune morphology

Analysis of the 1/25000 topographical maps shows a number of different types of dune morphologies in northern Medoc. All the dunes can be considered as relief features on a flat sub-horizontal surface, in English literature named a slack by Pethick (1986) or Ranwell (1992), but known locally as a "lette" or "lède" (Buffault, 1942). In Medoc the altitude of the lède's surface increases from 5-6m in the far north (Figure P17.5), to 18- 19m in the south of the peninsula (Figure P17.6). In the northern part of the peninsula the lède area is continuous while the dune area is limited. To the south the lède areas are split up by dune ridges in north-south bands. From north to south the abundance of dunes increases and around the Hourtin lake only a few lèdes can be found. In the east-west direction the lède surface is convex with the central area reaching 1-7m above the peripheral regions. The lède surface reflects the ground water table, which is normally dome shaped in large dune fields (Williss et al., 1959; Bakker, 1990), and represents a lower limit for deflation action (Pethick, 1986).

Previously dunes have been classified in a variety of systems based on combinations of age, mobility, sand source, structure, position relative to the shoreline, morphology, shape, number and orientation of slip-faces (see reviews of Carter et al., 1990; Pye and Tsoar, 1990). In Medoc most of the dunes have a crescentic form, or derive from a crescentic form. They can be divided into barchanoid and parabolic types. According to Pye and Tsoar (1990) these dunes can be sub-divided into: (i) simple dunes, consisting of individual dune forms spatially separated from their neighbours; (ii) compound dunes, formed by coalescence or superimposition of two or more dunes of the same type, and; (iii) complex dunes consisting of two or more different types of simple dunes which have coalesced or are superimposed. Following the nomenclature used by McKee (1979), Pye and Tsoar (1990) and Thomas (1992) we can differentiate six different dune forms in Medoc: (1) simple parabolic dunes, (2) compound digitate parabolic dunes, (3) coalescent compound climbing parabolic dunes, (4) simple barchans, (5) isolated compound barchanoid ridges, (6) coalescent compound barchanoid ridges. These types are now described in terms of their morphological characteristics (Figures P17.7, P17.8, P17.9, P17.10) and location on the Medoc peninsula (Figures P17.5 and P17.6).

6 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

The simple parabolic dunes are associated with the foredunes on the present day coastline. They occur from La Négade Cape to Montalivet (Figure P17.5). Along the coast north of Montalivet their heights are up to 20-30m. South of Montalivet the dunes reach the same hight, but are more hummocky in form. Around the Saint-Nicolas area the parabolic forms are highly degraded and apparently form two generations. Here the parabolic form is constituted by isolated hummocks similar to those reported by Pethick (1986) and Carter et al. (1990). Between Le Gurp and l’Amélie (Figure P17.5), and around Montalivet et le Pin Sec (Figure P17.6), parabolic dunes form compound types. Figure P17.8 illustrates a compound parabolic dune composed of several individual dunes and thus forming a digitate morphology (Pye, 1993). Only one generation of parabolic dunes exists and it forms a discontinuous system (20-30m high) between the barchanoid dunes to the east and the foredune to the west. There is a suggestion that the trailing arms of the parabolic dunes described above are truncated by the present day foredune (Figure P19.8). Associated with these compound parabolic dunes is the Dune de La Gastouse (Figure P17.5 and P17.8) located approximately 1km inland between Grayan and Le Gurp. This dune represents the only example of an isolated simple parabolic dune found in northern Medoc. The dune is 20-24m high, 600m long, and up to 250m wide. It is situated on a lède surface with a height of approximately 12m.

The coalescent counpound climbing parabolic dunes exist only, in the studied area, in the Cape of Piqueyrot of the Hourtin lake (Figure P17.6) with heights of up to 35m (Figure P17.11). At this point the parabolic forms have the same form as the simple parabolic dunes associated with the foredunes, and are composed of isolated hummocks. In Medoc there is no evidence of an evolutionary transition of parabolic dunes into elongate parabolic dunes as described by Pye and Tsoar (1990). The coalescent counpond climbing parabolic dunes are more frequent to the south of this area, especially to the south of Archachon bay.

The isolated simple barchan dunes have heights of 20-40m, widths of 300-500m, lengths of 300-750m, and are situated on a sandy lède which has an elevation of around 10m. There are nine isolated barchans south of Grayan along the La Perge marsh (Figure P17.5) situated north and east of an isolated barchan ridge (described below). Three of the more significant dunes, named on the I.G.N. map are Dune du Crohot du Negre, Dune de Labiney, and Dune du Lignon (Figure P17.6). The Dune de Labiau (Figure A5 and A9) is the largest dune and is situated north of La Perge marsh. To the north of La Perge the distance between the dunes is 300m. Between north of Pechaud (Figure P17.4) and Labiau the distances between the dunes are much greater, up to 4km.

Further to the south, between Le Flamand (Figure P17.5) and the south of La Perge marsh, the isolated simple barchans coalesce to form isolated compound barchanoid ridges. Such features have been observed by other authors in different parts of the world (McKee, 1979; Pye and Tsoar, 1990) and have also been termed sinuous transverse dunes (Carter et al., 1990; Hesp and Thom, 1990). In Medoc the heigth of these dunes is up to 39-55m (the highest dune being Dune de Mourey: Figures P17.5 and P17.9), they are 500-700m wide, and the ridges can be separated by a flat lède which has an elevation of 9-13m and is less than 500m wide (Figure P17.9). Westwards of Dune de Mourey there are some very small isolated mounds. South of Le Mourey to Saint-Isidore the isolated barchanoid ridges occur in pairs. Individual dunes can show varying degrees of reworking. For example in the area of Dune de Sergenteau, Dune du Mourey and Dune du Ginestras (Figure P17.5), the dunes show blowout development on their stoss sides (Figure P17.9). To the north of the region between La Perge and le Flamand the degree of reworking is less.

South of Saint-Isidore (Figure P17.5) the isolated compound barchanoid ridges merge together to form a coalescent field of barchanoid ridges composed of four ridges (Figure P17.10). The height of these ridges is 42-66m (the highest is Truc de la Hourcade to the south - v on Figure P17.5) and widths of 1km to nearly 2km. Barchanoid ridges frequently

7 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France join forming the dominant components of complex dune networks (McKee, 1979; Pye and Tsoar, 1990). The resulting morphology has been referred to as grid-iron, fishscale, akle, or reticulate networks (Pye and Tsoar, 1990). In Medoc the most landward of the barchanoid ridges is more linear than the ones further seaward, and the most seaward ridge is discontinuous. In this area dune heights increase from west to east starting at 32m for the western most barchanoid ridge, 64 and 59m for the next two, and then falling to 35m for the remnants of the compound climbing parabolic dunes located just west of Hourtin lake. Between the ridges are depressions, which Buffault (1942) termed internal lèdes. Some of these have similar elevations to the external lède underlying the whole dune field, whilst others are raised.

Dune chronology

Careful re-analysis of an earlier work by Buffault (1942) together with observations of old maps (Belleyne, 1762; Cassini, 1798) shows that, with the exception of the compound climbing parabolic dunes, all the dunes in north Medoc where moving until the last century. Preliminary field investigations showed a lack of sand bleaching and a very small humic horizon, thus indicating that the dunes have to be substantially younger than the 5100yrs suggested by the note of the B.R.G.M. geological maps (Marionnaud, 1972; Dubreuilh and Marionnaud, 1973).

Buffault (1942) divides the dunes of the Aquitaine region into primary, and modern forms. The primary dunes were covered by forest prior to the 18th century (Buffault, 1942) and consist of coalescent compound climbing parabolic dunes (or closely imbricated parabolas in the terminology of Cooper (1958). Barrere (1992) stated that the invasion of these primary dunes by barchans occurred in the Middle Ages, and that inland sand movement resulted in long tongues of sand, small dunes transverse to the coastline and low parabolic dunes. It is believed that the primary dunes were responsible for the impounding of rivers and the formation of the lakes along the Aquitaine coast (Duregne, 1890; Welsh, 1911; Buffault, 1942). Cooper (1958) reported that Harle and Harle (1920) estimated that the building of the primary and modern dunes has required about 6000yrs. This debatable estimation was based in the computation of total volume per unit frontage/present annual increment.

All the dunes situated westwards of this primary dune system were considered by Buffault (1942) as modern. Thus modern dunes consist of the two type of crescentic dunes: parabolic and barchanoid. Before stabilisation the modern dunes were actively invading the primary dunes and had overtaken them in many places. Buffault (1942) believed that the modern dunes did not begin to form before the 5th century A.D. (around 1500 B.P.). He reports that in the 10th century A.D. a charter documented the existence of a pine forest on the primary dunes in the Soulac area. These primary dunes were distinguished by being used for animal grazing and called locally "montagne" or "forêt". Further evidence for the date of formation of the modern dunes comes from a record cited by Buffault (1942) concerning the town of Biscarosse, situated south of Archachon bay (Figure P17.1). The first of these records, dated July 2nd 1277, describes the forest which covered the primary dunes as “lying between the sea shore on one side, and La Lucate (the lake shore) on the other”. In a re-iteration of this document, dated September 18th 1680, mention is made of “the white sands which lie between the forest and the sea shore”. It is possible that these white sands, which represent the mobile dunes, with regard to time appeared between the dates of the two records.

Other historical evidences, reported by Buffault (1942), confirm the mobility of the modern dunes during the following centuries. This evidence describes sand invasion in a number of areas including:

(i) the church of Lège, north of Archachon bay, which led to its relocation 4km eastward in 1480, and a further 3km to the south in 1650; (ii a property in Lilhan, a village to the south of Soulac, in 1580 and the abandonment

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of the village in 1595; (iii) the harbour of the Pointe de Grave marsh in 1585. (iv) the church of Soulac and the surrounding forest in 1690, the covering of up to 65% of the village in 1710, and the final abandonment of the church and the foundation of a new one, 2km further landward in 1744; (iv) numerous other villages and their churches in the south of Aquitaine at the end of the 18th century.

Finally, the modern dunes are mapped in the last centuries as being mobile on the lède areas, by Masse (1707), Cassini (1798) and Belleyne (1762). It is notable that all these dates for the period of mobility of the modern dunes are substantially younger than the date of 3000 or 2300 B.P. quoted by the B.R.G.M. for the youngest dunes. The first attempts at stabilising the modern dunes occurred between the 14th and 15th centuries in the south of the Aquitaine, and the 17th to mid-18th century in other areas. However, it was only in 1770 that dune fixation became of importance to the local government. After a number of attempts before 1789, it was only in 1801 that the French government decreed the dunes would be stabilised by forest plantation (Buffault, 1942).

In an attempt to substantiate the above dates for the periods of dune activity all the 14C dates from the Medoc have been compiled (Table 1). In simple terms the 14C dates represent times when organic material (plant debris) was present to date. With regard to dune activity, periods of vegetation and paleosol development correspond to periods of stabilisation. The 14C dates show that there are two groups of dated samples, one between approximately 3500 and 3000 B.P., and the other from approximately 2250

to 1500 B.P. Of course, with a greater number of dated samples a different pattern may be observed and it cannot be ruled out that the two groups represent part of a larger age bracket spanning approximately 3500 to 1500 B.P. These data suggest two possible scenarios for the periods of dune development:

(i) three periods spanning approximately 5000-3500 B.P., 3000-2250 B.P., and 1500- 250 B.P.; (ii) two periods spanning approximately 5000-3500 B.P. and 1500-250 B.P.

Regardless the chosen scenario it is likely that the modern dunes were active from approximately 1500 to 250 B.P., which is consistent with the historical evidence. However, the period of activity of the primary dunes is somewhat problematical. An earlier date would be from 5000 to 3500 B.P. and would be in accordance with the calculations of Harle and Harle (1920). However, it is also possible that the dunes were active, either again or for the first time, between 3000 and 2250 B.P.. Support for the latter dates comes from pollen data from a core at the head of La Perge marsh (Diot and Tastet, 1995; Pontee et al., 1997) which suggests a dry period, marked by the decrease of arboreal pollens, which reached a maximum around 2500 B.P. and corresponds to the Sub-Atlantic period.

OIRSL Datations

The first OIRSL datations were realise on samples collected from different sites along the Médoc Peninsula , following the chronological framework of the BRGM (Marionnaud, 1972). They were realised in the Laboratory of Geography in the Universty of the Sussex (UK) (Clarke et al, 1999). They show that the morphological dune system types are mobile simultaneously. The ages obtained (Table 2) seems to be in contradiction with the chronological classification of the dune system proposed by Dubreuilh, 1971, Marionnaud, 1972 and Dubreuilh and Marionnaud, 1973. It appears clearly that the isolated barchanes, the barchanoid ridges and the parabolic dunes were mobiles while

9 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

the same period of aeolian activity which ended after the XVIIth century. Moreover, they belong to the same system of the "modern" dunes. Then, it seems dangerous to establish a chronology of the dune system based only on their morphology.

Recent new OIRSL datations were obtained in the North Médoc and in the Sanguinet lake dune system (Table 3 and Figure P17.12) as on the Pyla dune (Table 4). They will give us the opportunity to modify the precedent chronology based on 14C datations on paleosols.

Discussion

Chronology

Both historical and 14C evidences suggest that the modern dunes on the Medoc peninsula were active from 1500 to around 200 B.P.. This period spans the Little Ice Age when dune activity was widespread throughout Europe occurring in the Netherlands (Zagwijn, 1984; Klijn, 1990; Orme, 1990), Denmark (Christiansen et al., 1990), the Baltic coast of Poland (Borowka, 1990), and U.K. (Tooley, 1990; Pye and Neal, 1993). At this time dune development was favoured by the climatic deterioration and the concomitant deforestation in consequence of the inhabitants increased need for fuel (Grove, 1987).

Comparison with Bressolier et al. (1990) in the Dune du Pyla area is difficult since these workers interpreted three overlapping phases of dune activity. The first dune building episode was believed to have occurred 3000-1000 B.P., with the formation of parabolic dunes contributing to partial or complete closure of small estuary inlets leading to tagoon formation. The second phase of dune activity occurred 2400-500 B.P. (and later) and was thought to have resulted in barchan dunes completing the enclosure lagoons of Les Landes (Bressolier et al., 1990). They also suggested that man settled in the sparse pine/hazel forest towards 2000 B.P.. Around 1500 B.P. coastal barchan dunes moved inland, invading the parabolic dune system and burying the vegetation. The third and final phase of dune activity in the Dune du Pyla region was believed to have occurred since the end of the 19th century.

A comparison of dune activity in Medoc with dates obtained from the paleosols from the Pyla dune is more informative (Fig. 10). It can be seen that at Pyla there is a strong suggestion of a period of stability lasting from approximately 3700 to 3000 B.P. and thus overlapping the first period of stability in Medoc (3500-3000 B.P.). The second period of stability in Medoc, from 2250-1500 B.P., is absent in Pyla indicating that dune activity resumed earlier at Pyla. However, the existence of a diatom strata between paleosols III and IV (Froidefond and Legigan, 1985) possibly indicates a humid period at this site. Confirmation of this hypothesis must wait for further studies of the diatomaceous strata.

General setting of dune development

On the Aquitaine coast of France previous works (Bressolier et al., 1990; Tastet et al., 1993) suggested dune formation during receding sea level. Due to the poor understanding of sea level changes in this area it is difficult to prove/disprove this theory with absolute certainty. However, it can be said that dune development on the Aquitaine coast has taken place in the general context of the Holocene S.L.R. and coastal erosion. Present day rates of erosion along the Atlantic littoral zone of Medoc are 0.2 to 10m/yr (Froidefond and Prud'homme, 1991; Klingebiel and Gayet, 1995; Aubie and Tastet, 2000). Transport of eroded material has led to the formation of an offshore sand sheet and the southerly progradation of the Cap Ferret spit partially closing the Arcachon Bay (Figure P17.1). In terms of the coastal sediment budget, dune development has therefore occurred under conditions of a negative sediment budget in which longshore littoral transport, coupled with onshore aeolian transport, and, to a lesser degree, offshore transport, has exceeded the sediment supply (L.C.H.F., 1979). The result is in accordance with many other areas of the world (Hesp, 1988; Klijn, 1990; Orme, 1990; Pye, 1990) and corresponds to scenario of marine sand supply slightly lower than the rate of aeolian transfer from the beach to the dunes described by Pye (1990). This situation is

10 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France conductive to small transgressive parabolic forms originating from a series of blowouts on the foredune. Hesp and Thom (1990) note that under these conditions partial re- vegetation following dune field development is possible. Further foredune ridges may develop, or be reconstructed, on the seaward margin in response to a series of storms (Goldsmith, 1985) or the coalescence of foreshore bars (Carter et al., 1993). Because of widespread management of the vegetation the present day foredunes on the Aquitaine coast lack extensive blow-out development despite the general coastal erosion.

The sparse vegetation, on the pre-existing lède surface further inland, moderate sand supply and wind energy have led to moderate-width transgressive dune fields dominated by transverse and oblique dunes with inter-dune deflation plains and troughs (Hesp and Thom, 1990). In Medoc the dune complex is most developed in the south where the greater part of the barchanoid forms occur. The general opinion is that barchans are formed in vegetation free areas, with limited sand supply, with large sand flow and almost unidirectional winds (Pye and Tsoar, 1990, Thomas, 1992; Pye, 1993). However, several authors are doubting whether barchans are always formed under conditions of limited sand supply (Orme, 1990; Cooke et al. 1992). In Medoc the north-south trend from isolated simple barchans to isolated compound barchanoid ridges and further to coalescent compound barchanoid ridges can be interpreted as a consequence of increasing sand supply (McKee, 1979; Thomas, 1992; Pye and Tsoar, 1990). The increasing sand supply is thought to have resulted from the existence of a large sand sheet located on the southern part of the continental shelf (Gensous B., 1971; Castaing et al., 1972; Klingebiel A. and Gayet J., 1995). This sand was reworked by the Holocene rise of sealevel and formed the extensive aeolian dunes in the southern part of Medoc.

The location of the barchanoid ridges has been caused by the retardation of landward dune migration and the concurrent accumulation of sand supplied from the reworking or landward movement of parabolic dunes to the west. The small isolated mounds (Figure P17.9), located to the west of the Dune de Mourey, may represent smaller, but more rapidly migrating dune forms supplying the barchanoid ridges. . The retardation of landward dune migration is thought to have resulted from the presence of lakes, wet or vegetated lèdes, and most importantly, the primary dune system covered by forest. The trend of increasing height of barchanoid ridges further inland (Figure P17.10), and their increasingly linear morphology, can be interpreted as resulting from the accumulation of sand.

Although parabolic dunes normally are suggested to develop from blowouts in a vegetated sand surface (Pye and Tsoar, 1990), extensive fields of large parabolic dunes (5-10m in height and 1-2km in length) have been formed by transverse dunes behind the foredune under the increasingly stabilising effect of vegetation (Goldsmith, 1985). Additionally, parabolic dunes have been reported to develop as a consequence of decreased sand supply resulting from increased distance to the coast (McKee, 1966), or a cessation of sealevel rise (Orme, 1990). However, in Medoc area there is a clear association of parabolic forms with the foredunes. The degraded form of the simple parabolic dunes to the south of Montalivet results from inland dune migration and the concomitant sand loss. An examination of the surface topography illustrates that simple parabolic dunes, located some distance from the coast, in fact originated in the compound digitate parabolic dunes located further seawards. The release of simple parabolic forms is indicated by several small mounds of sand representing the remnants of the trailing arms (Figure P17.7). The truncation of the trailing arms of the compound digitate parabolic dunes by the present day foredunes can be interpreted as a result of coastal erosion and inland migration of the foredune since the parabolic activity stopped after pine plantation. According to Pye (1990) blowout development in the foredune, giving rise to small transgressive parabolic dunes, can be initiated by shoreline erosion which damages the foredune vegetation.

The coalescent compound climbing parabolic dune field, forming the primary dune system, is different in it morphology from the parabolic dunes forms from the modern

11 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

system. It is interpreted to have formed under different climatic conditions prior to the modern system. It is well know that parabolic dunes generally form in humid region with a relatively dense vegetation cover and predominal wind direction (Pye, 1993). Additionally, Cooke et al. (1992) report that strong winds are necessary to drive parabolic forms over vegetated surfaces. It is possible that the primary system of dunes represents a continental reworking of the earlier continental system known as the Sables des Landes (Duregne, 1890; Welsh, 1911; Buffault, 1942) or of more recent holocene sandsheets, the existance of which seems demonstrated by the interpretation of the 14C and OIRSL datings.

Conclusion

The transgressive dune fields of the Aquitaine coast formed in the context of Holocene sealevel rise and subsequent coastal erosion. This resulted in a negative sediment budget in which alongshore and offshore wave transport and onshore aeolian transport exceeded the sediment supply. The most important dune development occurred in the south of the region where sand deposits on the continental shelf were reworked during the Holocene sealevel rise (Gensous, 1971; Klingebiel and Gayet, 1995).

The only previous stratigraphic and cartographic work in Medoc was carried out by the B.R.G.M. (Marionnaud, 1972; Dubreuilh and Marionnaud, 1973). Based on morphology and few 14C ages they divided the dunes into four chronological generations comprising:

(i) isolated barchans (>5100 B.P.); (ii) parabolic dunes (5100-3000 B.P.) localised on slack areas; (iii) barchan dunes (2300-200 B.P.); (iv) present day littoral dunes (or foredune).

This classification has been revised after a more thorough study of dune morphological types, information from historical records and additional 14C dating. Excluding the foredune, this work has allowed the identification of six different morphological dune types: (1) simple parabolic dunes, (2) compound digitate parabolic dunes, (3) coalescent compound climbing parabolic dunes, (4) simple barchans, (5) isolated compound barchanoid ridges, (6) coalescent compound barchanoid ridges. Historical sources and 14C dating indicate that the chronology of dune development differs substantially to the B.R.G.M. interpretation, since there are only two generations of dunes; primary and modern (Buffault, 1942), both substantially younger than oldest generation of dunes as proposed by the B.R.G.M.

The primary dunes consist of coalescent compound climbing parabolic dunes which were naturally fixed by vegetation before the invasion of the modern dunes some time before the last century. They are interpreted to have been formed under different climatic conditions to the present, possibly more humid. The date for initiation of the primary dunes is not clear at present, but could possibly be around 5000-3500 B.P. or 3000-2300 B.P.if we consider only the age of the paleosols. In the North Medoc area the previous work of the B.R.G.M. ignored this system of dunes, and included them within their Meso-Neolithic dune system. They considered this system to be constituted by only barchan forms. The new OIRSL dates suggest that the primary dunes were moving until the Xth Century, age of the burying of the sand on the leeside of the climbing parabolic dunes from this system (Tables 2 and 3).

The modern dunes consist of: simple barchans, isolated compound barchanoid ridges, a field of coalescent compound barchanoid ridges, simple parabolic dunes and compound digitate parabolic dunes associated with the foredunes. Historical sources and 14C informations and the OIRSL datings demonstrate that all the morphological dune types forming the modern dunes were simultaneously active between 500 and 200 B.P.

In the region of Hourtin lake, the sequence of dunes inland from the coast consists of: the littoral foredune, compound digitate parabolic dunes, discontinuous isolated barchanoid ridges,

12 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France and coalescent compound barchanoid ridges of increasing height and linearity further landwards and belonging to the modern dune system. Inland of the last barchanoid ridge is an older field of coalescent compound climbing parabolic dunes of lower height belonging to the primary system. The barchanoid forms are interpreted as a result of the amalgamation of landward migrating parabolic dune forms appearing at the coast as blowouts in the foredunes. The large heights of the barchanoid forms can be explained by favourable conditions of sand accumulation caused by the presence of the lèdes, the Hourtin lake, and most importantly, the vegetated primary dune system that curtailed landward sand transport past this point. The north-south trend from simple barchans, to isolated compound barchanoid ridges to coalescent compound barchanoid ridges may be due to the increased sand supply.

The dates (14C and OIRSL) obtained allow a different interpretation of the dune morphology and chronology. They suggest that the modern dunes were mobile between 500-200 years B.P.(i.e during the "Little Ice Age"); when coastal-dune mobility was widespread in Europe. The modern dunes consist of a variety of types of cresentic dunes which were active simultaneously. Landward of the present foredune, there is a succession (more or less complete) of: digitate or isolated parabolic dunes, barchanoid dunes which are (as in the Hourtin lake) simple barchans, isolated barchanoid ridges and finally coalescing barchanoid ridges, whose altitude increase from west to east. This sequence is thought to be the result of an increasing accumulation of sand. After a number of attempts before 1789, the French gouvernment finally decreed in 1801 that the dunes were to be stabilised by the planting of pines.

The OIRSL datings, we have lately received, permit to rejuvenate the primary dune system, the climbing parabolic dune of which seem to have be mobile until the Xth Century. However, it is actually difficult to precise when they started to move, sometimes before the VIIIth or the VIIth Century.

It seems that the paleosols older than 1500 B.P., which outcrop more or less horizontaly are not representative of any dune system, at present morphologicaly represented in the Aquitaine Coast.

They separated sandsheets the OIRSL of which are 3520+/-315 B.P., 3645+/-460 B.P. and 3350+/-310 B.P (Table 4, Figure P17.15).

So, to summerise (Figure P17.16), the periods of strong aeolian activity on the Aquitaine Coast, appear to have occured for the first time and episodicaly before 1 000 B.C., given rise to aeolian spreadings only representated by sandsheets between paleosols. There is at present no dates of aeolian deposits from the gap 1 000 B.C.-500 A.D. which seems correspond in Médoc to an aeolian spreading separating by two groups of palaeosols. Finally, the two transgressive dune system are the only morphological evidence of the wind action and their age as to be rejuvenate as explained above.

Palaeo-environmental investigations on the beach of the North Médoc

Observations on the beach of the North Médoc in the proximity of Soulac-sur-Mer allows the realisation of a schematic transect regrouping the palaeoenvironmental and archaeological remains (Figure P17.13). Estuarine clays with Scrobicularia and Oysters were found in depressions of the Pleistocene clays of "Le Gurp". This profile shows firstly the presence of two different periods of human occupation (around 2500 years B.P. and 1600 years B.P.). Secondly, two generations of clay appear. They are separated by a period erosion and channels formation. Thanks to these remains, we tried to reconstruct the coastal changes (Figure P17.14):

· Firstly, the palaeoenvironmental and archaeological remains were leveling permitting to reconstruct the situation around 2500 years B.P.(with a human occupation from the Iron Age) · We observe that between 2500 and 1850 years B.P., a period of clay (with Scrobicularia)

13 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

erosion followed by the filling by clays (with oysters) of the channels occurred. It may correspond to a positive tendency of the sea-level. · Around 1600 years B.P., we note the end of the infilling of the channels and a human occupation of the area. · After 1600 years B.P., the dune system recover those formations.

5.2 Archaeological Results

Shown in full in Appendix P17.3.

6. CURRENT APPROACH TO THE ARCHAEOLOGICAL RESULTS

Archaeological prospections are always in progress along the Atlantic Coast. New sites and remains are found each year due to coastal erosion (especially after storms in winter).

7. CURRENT APPROACH TO THE PALAEO-ENVIRONMENTAL RESULTS

OIRSL datations are still in progress and will bring a more complete chronology of the dune system.

New investigations will be made on the beach of the North Médoc to better understand the geometrical retation between all the dated evidences and so to precise the evolution of the coastal changes.

8. SUCCESSES AND PROBLEMS IDENTIFIED BY THE LIFE PROGRAM

The LIFE progam allows firstly archaeological inventory and palaeoenvironmental prospections along the Atlantic coastline of the North Médoc. The archaeological sites were described and studied. Palaeoenvironmental investigations on the beach brough in evidence some light sea- level fluctuations during the Late Holocene and especially a positive tendency of the sea-level between 2500 and 1940 years B.P. (Figure P17.15). This positive tendency is not only recorded in the Médoc area but also in the marshes of the East and West Banks of the Gironde Estuary and in the Oléron Island ("La Perroche" marsh).

So, we can postulate that its origin is not due to a local event but to a more regional, and even global, climatic change (Figure P17.15).

Secondly, studies on the dune system allowed to establish a chronology of their evolution. All these informations contributed to a better understanding of how the Médoc coastline evolved during the Holocene.

9. COMMUNITY INVOLVEMENT ISSUES AND SOCIAL INCLUSION

9.1 Funding agency

The "Conseil Régional d'Aquitaine" and the "Conseil Général de la Gironde" can, with or without the State, subsidize research or managment studies on the coastal zone, upon request of a city council or of a group of cities. The "Service Régional de l'Archéologie d'Aquitaine", depending on the Culture Ministry, is the authority delivering the excavation authorizations and supporting, at least partially, archaeological research.

9.2 Investigation and monitoring

A State/Region Plan is in progress concerning "a tool for the provisional management of the

14 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

(whole of the) Aquitaine Coast". Under the direction of the Aquitaine Region council, (funded 50% by the Region and 50% by the State), this programme is realized by the BRGM in collaboration with IFREMER and the Forestry service (ONF).

Some local programmes are in progress as well as the "District de la Pointe du Médoc" Three breakwaters are progammed.

9.3 Current status and action

Funded by the State, the Conseil Régional, the Conseil Général and the cities, some actions are in progress. Firstly, in terms of touristic initiative: the management of the waterfronts of seaside resorts, the creation of landscaped car parks in the forest with access ways to the beach, the building of cycle tracks. Secondly, in terms of environmental and coastal ecosystem protection: integrated management of some dune areas, maram grass planting with additionnal funding from the ONF, the "Conservatoire du Littoral" and the European Community.

9.4 Public awareness

Mobile public exhibitions "Aquitaine Terre des Hommes" and "Histoire d'Océan, Rivages Aquitains" realised by "Cap Sciences", (an association for the dissemination science results to the general public), are supported by the Regional Council. An "Atlas du Littoral Aquitain" was realised by the Conservatoire du Littoral, with partial funding by the Regional Council.

From the archaeological point of view, the city of Soulac has a small Archaeological Museum organised and maintained by volunteers. The Société Archéologique et Historique du Médoc, a volunteers association, edits a biannual report "Les Cahiers Médulliens".

9.5 Experiences, successes and problems with the current approach

The most positive action on the Aquitaine coast was developed by the MIACA (Mission Interministerielle d'Aménagement de la Côte Aquitaine) between 1970 and 1992. The exemplarity of the MIACA approach allowed to preserve the Aquitaine coastline by suggesting an urbanization along 3 axes: perpendicular to the coast, associated to existing urban area and alterning managed and natural zones. This management preserved the natural environment of the coastal zone, including the coastal dunes, forest and coastal lakes. This major experience led to the creation of a new similar structure, the "Mission Littoral", which will work in the same way in the framework of the 2000-2006 State/Region plan.

The methods of hard defences used in some local areas against coastal erosion (L'Amélie for example) have produced significant disorder, in terms of sediment dynamics, to demonstrate that they are not appropriate. They have to be replaced by soft interventions. In this case, the experience of the city of Montalivet has to be cited as an example. They developed an original system made of wood posts placed in zigzag to keep the sand at the highest level of the beachface.

10. CONCLUSIONS

10.1 Threats

The main natural threat on the Atlantic coast is the beach and dune erosion. Flooding of the saltmarshes is threatening in the North at the "Anse des Huttes", where the dune ridge, separating the Ocean from the marsh, is only 200 m wide and undergoes a present-day severe erosion of more than 5 m/yr.

On another hand, the touristic pressure is a matter of concern, and as effects on landscape integrity (the high frequentation of dunes and beaches facilitate the erosion), sanitation, and water pollution.

15 Palaeo-environmental Study Area P17 The Atlantic Coast, North Médoc, France

10.2 Management needs

Currently the Regional and Departemental Councils do not have the leadership of the management of the coastal zone because of the decentralisation developed during the last 20 years. The cities are free to choose their own management projects. However the action of the Region or the Departement can favour the elaboration of concerted plans. Nevertheless, the decentralisation is still an obstacle for a coherent management. This situation is particulary known by the littoral town councils which grouped in "Syndicats intercommunaux" as "Le District de la Pointe du Médoc" to minimize the effects of the decentralisation.

11. KEY ISSUES

The coastal erosion, demonstrated by studies of long term coastal changes, should be taken into account by development plan policies. In detail, the sedimentary and dynamic processes must be better understood to precise the management plans. The erosion of sediment archives and archaeological evidences of high value requires the organisation of rapid intervention by both archaeological sedimentological and palaeoenvironmental teams..

12. BIBLIOGRAPHY

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13. ACKNOWLEDGEMENTS

We thank all the Municipalities the Atlantic coast involved in our work on the LIFE program for their support throughout the project.

Appendix = Please contact the project partners (see ‘Home' page) for copies of the Appendices

21 Age BP Error +/- Calibrated age Field reference Sample type Lab. ref. DATES FROM THE MEDOC 310 60 1450-1675 AD HO 9210 (core) Organic sand under a barchan dune Beta 95393 1450 70 527-692 AD Montalivet Stump in life position UQ2147 1760 50 145-410 AD TM 96056 Wood in palaeosol between sand layers Beta 102697 1920 130 197 BC-413 AD La Barrière Peat between sand layers UQ 1990 1980 60 103 BC-142 AD Gurp Niv. 2 Wood above the clay of the Gurp LY 4597 2300 70 (Marionnaud, 1972) Peat (Dépé) ? 3000 90 (Marionnaud, 1972) Peat (Dépé) ? 3160 60 1525-1285 BC TM 96049 Sandy peat between sand layers Beta 95383 3420 135 2110-1414 BC Euronat niv. 4 Peat between sand layers UQ 1991 5100 90 (Dubreuilh and Marionnaud, 1973) Peat (Saint-Nicolas) ? DATES FROM THE PYLA DUNE 320 60 1450-1670 AD TM 96016 Wood in palaeosol 3 Beta 95381 2690 70 (Froidefond and Legigan, 1985) Charcoal in the sand above the palaeosol 2 LRGMR Bx 2980 110 (Froidefond and Legigan, 1985) Wood in palaeosol 2 Gif ? 3080 60 1440-1145 BC TM 96013 Wood in palaeosol 2 Beta 95378 3180 60 1535-1305 BC TM 96012 Wood in palaeosol 2 Beta 95377 3220 70 1645-1380 BC TM 96015 Sandy peat in the base of palaeosol 1 Beta 95380 3310 70 1745-1425 BC TM 96014 Peat at the top of palaeosol 1 Beta 95379 3460 70 (Froidefond and Legigan, 1985) Wood in palaeosol 1 Gif ? 3490 60 1945-1660 BC TM 97001 Wood in palaeosol 1 Beta 102698 3510 70 1985-1660 BC TM 96023 Wood in palaeosol 1 Beta 95382 3680 110 (Froidefond and Legigan, 1985) Wood in palaeosol 1 LRGMR Bx

Ref. Location of the Sampling Name of Morphology Calculated Calendar Sample the dune Age Date and side of sampling

x y z en m

N M1 328,30 3 341,70 7 - 0,75 Mourey barchanoïd 560+/-65 1370- (west) ridge 1500 AD

N M3 328,75 3 341,55 10 - 0,75 Mourey barchanoïd 325+/-40 1630- (east) ridge 1710 AD

N M5 328,09 3 354,85 20 - 0,65 La barchanoïd 335+/-35 1625- Gastouse ridge 1695 AD (east)

N M7 330,00 3 353,80 28 - 0,80 Labiau barchanoïd 380+/-50 1565- (west) ridge 1665 AD

Table 2 Results of the OIRSL dating on the dune system of the North Médoc.

Name of the dune Side of the dune OIRSL Dates OSIRL Dates (BP) Réf (map location) system (BC-AD) Dune de Piqueyrot Stoss side 685-975 AD 1170+/-145 BP HT1 Dune de Piqueyrot Lee side 740-1190 AD 1035+/-225 BP HT2 Monts des Genêts Lee side 1615-1765 AD 310+/-75 BP HT4 Dune de la Gastouse Lee side 1630-1700 AD 335+/-35 BP NM5 Dune de Labiau Stoss isde 1570-1670 AD 380+/-50 BP NM7 Dune du Mourey Stoss side 1405-1535 AD 530+/-65 BP NM1 Dune du Mourey Lee side 1635-1715 AD 325+/-40 BP NM3 Le Moutchic Stoss side 1645-1715 AD 320+/-35 BP MC1

Table 3 Results of the OIRSL dating on the dune system of the North Médoc.

Name of the dune OIRSL Dates (BC/AD) OSIRL Dates (BP) Réf (map location) system Pyla dune 1835-1205 BC 3520+/-315 BP PA1 Pyla dune 2105-1185 BC 3645+/-460 BP PA3 Pyla dune 1660-1040 BC 3350+/-310 BP PA4 Pyla dune 945-1185 AD 935+/-120 BP PA5 Pyla dune 1670-1720 AD 305+/-25 BP PA7

Table 4 OIRSL dating of the palaeosols in the Pyla dune.

Figure P17.1 Distribution of the sand sheet system of “Les Landes de Gascogne” and the Holocene dune complex and marshes (modified after Enjalbert 1973). The study area is enclosed in a dashed line. Figure P17.2 & P17.3 Simplified geological maps of the coastal complex of the Médoc peninsula (after Marionnaud 1972; Dubreuilh and Marionnaud 1973). (1) Meso- to Neolothic dune system, (2) Proto-historic dune system, (3) Historic dune system, (4) Present-day littoral dune. Each system included the dune slack area between the dunes themselves. The distance between the crosses is 5 km. Figure P17.4 Location of the archaeological complex and sites along the Atlantic coastline. Figure P17.5 & P17.6 New maps of the coastal dune complex based on revised classification. (1) Dune slack areas (locally called “lette” or “lède”), (2) Primary dune system (coalescent compound climbing parabolic dunes), (3) Dunes of barchanoid type from the modern dune system (simple barchans, isolated compound barchanoid ridges, coalescent compound barchanoid ridges); (4) Parabolic dunes from the modern system (simple parabolic dunes, compound digitate parabolic dunes), (5) Foredune. The distance between the crosses if 5 km. Figure P17.7 Example of simple parabolic dunes associated with the littoral foredune. The distance between the crosses is 1 km. Figure P17.8 Example of a compound digitate parabolic dune associated with the littoral foredune and an isolated simple parabolic dune situated inland of the littoral foredune. The distance between the crosses is 1 km. Figure P17.9 Example of simple barchan dunes. The distance between the crosses is 1 km. 47

40 30

46

30

55

30 40

Figure P17.10 Example of an isolated compound barchanoid ridge showing blowout development on it’s windward side. The distance between the crosses is 1 km. Figure P17.11 Example of field coalescent compound barchanoid ridges (a) and east-west cross- section (b). To the east of the last linear ridge are two coalescent compound climbing parabolic dunes belonging to the primary dune system. The distance between the crosses is 1 km. Figure P17.12 Location of the dune system and of the samples dated by OIRSL. Figure P17.13 Transect on the beach of the Atlantic coast of the North Médoc. Figure P17.14 Reconstruction of the evolution of the outcrop on the beach. Figure P17.15 Synthesis of the Holocene evolution of the martime and estuarine marshes of our Study Area. a. b.

c. d-i

d-ii d-iii

Plate P17a The "La Glaneuse" complex: (a) "Védrine" structure (C) (b) Ditch (D) (c) Salt working site (E) (d) Woody posts alignments (G) (di) The north woody posts alignments (dii) The central woody posts alignments (diii) The south woody posts alignments a. b.

c. d.

e. f.

Plate P17b The "La Glaneuse" complex: (a) Woody quadrangular structure (I) (b) Stony well (J) (c) Tree trunks (L) (d) Animal footprints (M) (e) Agricultural prints (N) (f) Pyre (O) a. Burial wooden structure (E) b. The Boar (H)

c. Quadrangular wooden pits (I) d-i. Discovery of the Palaeoxodon antiquus on the beach

d-ii. Bones of the Palaeoxodon antiquus found d-iii. Bones of the Palaeoxodon antiquus found on the beach on the beach

Plate P17c The "L'Amelie" complex: (a,b,c) The "La Balise" complex: (d) a. Pits (C) b. Settlement and cemetery of from the Gallo- Roman period (D)

c. Pits in "gabion" (I) d-i. The "La Lede du Gurp" site excavations in 1981

d-ii. The "La Lede du Gurp" site Protohistoric e. The "La LAnse du Gurp" complexe: gardens Artefacts from the Neolithic period (A)

Plate P17d The "Pointe de La Négade" site: Archaeological Inventory: Atlantic Coast, France

Coastal Environme Running Cultural Visible Classification Source Sea-level Climatic Unvalidate Coastal Coastal Coastline Altitude Name Classification1 Source 2 Description X Lamb2ext Y Lamb2ext Managmen ntal Chronolog Amenity Amenity Fragility 2 1 Change Change d Code Unit Risk Context Type t Change y Value Bonus posts A scatter of archaeological remains, from the Neolithic alignment, to the Modern period including copper and Bronze Age wooden (+2.25 "La A scatter of implements, were found in outcrops of estuarine clays structures, 328.385 to 2062.023 to to -1.5 Glaneuse" archaeological AC 1 / or scattered on the beach or near the dune. Posts 1 3 3 3 3 2 1 3 D-R-I E 4 dune coast coins, ditch, 327.467 2060.233 m) complexe remains alignments and wooden structures were discovered. stony well, Celtic, roman, medieval and modern coins were also briquetage, found. prints in clays hoards,axes Archaeological remains from Neolithic to gallo-roman and palstaves, period were discovered in outcrops of estuarine clays or A scatter of (0 to "L'Amélie" boar sign, scattered on the beach. Hoards of middle bronze age 327.467 to 2060.233 to archaeological AC 2 / 1 3 2 2 2 2 0 4 D-R-I E 4 dune coast 6.5 m) complexe ceramics, axes and palstaves, briquetage for salt production (Iron 327.162 2059.379 remains coins, Age), a brass boar sign, ceramics of the 1st and the briquetage 2nd Iron Age and celtic and roman coins were found.

pottery Early Neolithic remains in organic layers in the foredune A scatter of "La Balise" sherds,stone : cardium impressed pottery sherds, stone mauld for a 327.162 to 2059.379 to >1 m archaeological AC 3 / 3 3 1 1 1 3 0 4 D-R-I E 4 dune coast complexe mauld, bones middle Bronze Age amboss.Pleistocene outcrops with 326.993 2058.621 remains remains bones remains : Palaeoxodon antiquus.

pits, water- Investigated from 1966 to 1985 and seemingly A scatter of "¨Pointe de la well, ceramics, destroyed by marine erosion: celtic to gallo-roman 326.993 to 2058.621 to >1 m archaeological AC 4 / 3 destroyed destroyed destroyed destroyed destroyed 0 4 D E 4 dune coast Négade" site coins, fibulae, period with celtic pits, water-wells, fibulae, glass, 326.902 2058.039 remains glass ceramics, coins.

Very important archaeological site, excavated from Settlement from traces of 1973 to 1994. Multiperiod occupations : Mesolithic, the (3 to 9 La Lède du metallurgy and Early, Middle and Late Neolithic, Beaker and Middle 326.902 to 2058.039 to Epipalaeolithic AC 5 / 3 2 3 3 3 4 0 4 D-R-I E 4 dune coast m) Gurp" site agriculture, Bronze Age, Iron Age. Early Neolithic wooden ; Middle 327.183 2056.664 to the Gallo pottery incomplete burials, Middle Bronze Age metallurgy and Roman Period traces of agriculture

In the north, traces of Romano-celtic occupation and of Romano-celtic a funeral pyre, with pottery sherds, fibulae and coins. In "L'Anse du pottery sherds, (2.5 to settlement, the south, a megalith (destroyed by the ocean in the 327.183 to 2056.664 to Gurp" fibulae, coins, AC 6 / 3 1 2 1 1 2 0 3 D-R-I E 4 dune coast 4.5 m) funeral pyre, seventies); a scatter of worked flints (including 326.947 2055.677 complexe flints megalith microliths), and Bronze Age pottery included in clays under the dune. flints, Settlement from ceramics, Azilian settlement reoccupied during the Neolithic period The the Neolithic to fibulae, (lithic artefacts), during the end of the Bronze Age 326.947 to 2055.677 to > 1 m "Taillebois" AC 7 / 3 1 2 1 2 2 0 3 D-R-I E 4 dune coast the Iron Age artefacts from period and the Iron Age period (ceramics and metallic 316.319 2053.408 Complexe period Bronze Age artefacts discovered in paleosoils under the dune). period Neolithic flints, The "Pointe settlement, Neolithic settlement with abundant artefacts. Possible ceramics, de la settlement from settlement from the Second Iron Age period with 316.319 to 2053.408 to > 1 m coins, oven for AC 8 / 3 1 2 1 2 2 0 3 D-R-I E 4 dune coast Pinasse" the Iron Age to ceramics and very rare coins (from Ptolémée Ier-Soter), 325.933 2050.028 ceramics complexe the Gallo- Gallo-Roman occupation (ceramic production). production Roman period Neolithic flints, Neolithic settlement located at 3Km south from The settlement, ceramics, Montalivet, Discovery of bronze artefacts from the Early "Montalivet depository of > 1 m bronze and AC 9 / and the Middle Bronze Age (axes, depository), 325.933 2050.028 3 1 2 1 2 2 0 3 D-R-I E 4 dune coast Beach" bronze axes, copper axes, numerous Gallo-Roman traces on the beach and in the complexe Gallo-Roman statues, coins dune : small statue, coins from the 3rd century A.D. settlement