Mean papers by Laurent Deschodt
![Research paper thumbnail of Sédimentologie et datation des dépôts fluvio-éoliens du Pléniglaciaire weichselien à Lille (vallée de la Deûle, bassin de l'Escaut, France)________[Sedimentology and dating of weichselian upper pleniglacial fluvio-aeolian deposits in Lille (Deûle valley, schelde basin, France)]](https://attachments.academia-assets.com/46061191/thumbnails/1.jpg)
Dans la région de Lille, la Deûle a nettement incisé le substrat crayeux. L’incision la plus anci... more Dans la région de Lille, la Deûle a nettement incisé le substrat crayeux. L’incision la plus ancienne se situe sous le bas de versant du Pays de Weppes et est antérieure au Weichselien. Le tracé a été actif jusqu’au Début Glaciaire. Une incision plus récente, antérieure au Pléniglaciaire supérieur weichselien, s’individualise environ un kilomètre plus à l’est. Le chantier de la rue Hegel permet une observation directe d’une partie du remblaiement du chenal pléniglaciaire weichselien. Les alluvions sableuses se développent sur 12,5 mètres, elles se déposent en petits chenaux et sont accompagnées de quelques marqueurs de froids. Elles sont datées de la fin du Pléniglaciaire (17 960 ± 90 BP, soit 21 639 ± 361 cal. BP). Elles cèdent la place à des formations fluvio-éoliennes, apparemment en continuité, qui, d’abord litées et argileuses, deviennent loessiques. A la lumière de la date 14C et de deux datations OSL (21,7 ± 1,9 et 23,7 ± 2,0 ka), la formation limoneuse à dominante éolienne semble se mettre en place rapidement (vers 21,7 ka). Ces premières dates effectuées sur le remblaiement loessique terminal des fonds de vallées du nord de la France sont à considérer avec prudence. Elles impliquent la simultanéité du dépôt éolien en fond de vallée et sur versant à la fin du Pléniglaciaire, plus précocement que dans les vallées sableuses du bassin belgo-néerlandais.
The Deûle River has scoured the chalk substratum in two places in the vicinity of Lille. The older scouring is under the lower slopes of the Weppes country. It occurred prior to the Weichselian. It was still active in the Early Glacial. A more recent scouring, predating the Upper Pleniglacial, appeared one kilometre eastward. The Hegel street excavations allow direct observation of a portion of the in-filled channel; a 12,5 m thick sandy alluvium deposited in small channels associated with indications of cold. It dated to about the end of the Pleniglacial (17 960 ± 90 BP, i.e. 21 639 ± 361 cal. BP). These deposits gave way to -apparently continuous- fluvio-aeolian formations, bedded and clayey at first, becoming loess-like in the upper strata. According to the C14 date and to two OSL dates (21.7 ± 1.9 and 23.7 ± 2,0 ka), this silty, primarily aeolian formation seems to have been rapidly deposited (about 21.7 ka). These first dates of loess upper valley infilling from northern France should be considered with caution. They appear to indicate the simultaneity of aeolian deposit on slope and valley bottoms at the end of the Pleniglacial, earlier than in the sandy valleys of Belgium and Netherlands.
![Research paper thumbnail of Transect partiel de la plaine de la Scarpe (bassin de l'Escaut, Nord de la France). Stratigraphie et évolution paléogéographique du Pléniglaciaire supérieur à l'Holocène récent________[Partial cross-section of the Scarp plain (schelde bassin, north of France). (...)]](https://a.academia-assets.com/images/blank-paper.jpg)
La plaine de la Scarpe est une vaste dépression développée dans les sables marins éocènes entre l... more La plaine de la Scarpe est une vaste dépression développée dans les sables marins éocènes entre les pays de la Pévèle et de l’Ostrevant. Une « plaine haute » au nord se distingue d’une « plaine basse » au sud. Le remplissage est essentiellement sableux (en partie tourbeux dans la plaine basse). La plaine est ponctuée de nombreux microreliefs. Les petits cours d’eau qui la drainent sont en inadéquation avec son gabarit. La pose d’un gazoduc à travers la plaine a été précédée de sondages archéologiques. Nous présentons la stratigraphie sous la forme d’un long transect partiel et nous proposons un scenario d’évolution de la plaine depuis le Pléniglaciaire supérieur weichselien. La majeure partie de la sédimentation quaternaire est constituée de lits sableux qui alternent avec des lamines limoneuses. Cette nappe alluviale, corrélable à l’Older coversand I de la zone sableuse, s’est déposée en tout point de la plaine sous un régime hydrologique périglaciaire très contrasté au cours du Pléniglaciaire supérieur weichselien (datations OSL aux environs de 34, 21 et 20 ka). Des avulsions répétées de chenaux larges et peu profonds ont laissé des traces de défluviation dans la microtopographie. La plaine haute est assimilable à des cônes de déjections très étalés issus de la Pévèle. A la fin du Pléniglaciaire supérieur weichselien, dans une ambiance climatique plus sèche, de petites dunes allongées (sable ou alternances de sable et de loess) se forment au centre de la plaine ou s’adossent contre le talus bordier de la Pévèle (datations OSL aux environs de 19 et 15 ka). Cette phase semble être au moins en partie contemporaine du Beuningen gravel bed de la zone sableuse. Une ultime phase de déflation est attribuée au Dryas récent. Plus modeste encore, ce dernier dépôt éolien se présente sous la forme d’une nappe peu épaisse mais continue, limitée à une large partie sud de la plaine. Les cours d’eau tardiglaciaires et holocènes, légèrement incisés, occupent le dernier état de chenaux pléniglaciaires (datations 14C des remplissages à partir de 12 345 BP). Les anciens chenaux peuvent alors constituer le lit majeur des petits cours d’eau tardiglaciaires-holocènes. Au cours de l’Holocène, la nappe remonte et la tourbe envahit les zones les plus basses de la plaine. L’ennoiement tourbeux, étendu mais souvent peu épais, exploite et estompe la topographie héritée du Pléistocène. Trois systèmes chenalisés tardiglaciaires-holocènes (deux chenaux secondaires de la Scarpe et un affluent) ont été recoupés. Nous détaillons deux d’entre eux. Le méandre de Vred a conservé les traces d’une occupation archéologique (structure de franchissement de l’Age du Bronze, environ 1000-800 av. J.-C.) et de l’impact de la capture anthropique en amont de la Satis au Haut Moyen Age (dépôt d’inondation limoneux travertineux).
The Scarpe plain is a depression in the Eocene marine sands between the Pevele and Ostrevant regions. A “high plain” is distinguished northwards from a “low plain” southwards. The infilling is mainly sandy (with a peaty part in the low plain). Numerous micro-topographies are scattered throughout the plain. The small water courses which drain the plain are not proportionate to its size. The laying of a gas pipeline across the plain was preceded by archaeological borings. We present the stratigraphy as a long crosssection and propose an evolution scenario for the plain since the Weichselian Upper Pleniglacial. The sedimentation consists mainly of sandy beds alternating with loamy laminae. This alluvial sheet, present everywhere in the plain, was deposited under strongly contrasted hydrological conditions during the Weichselian Upper Pleniglacial (OSL dates about 34, 21 and 21 ka). It may be correlated to the northern sand belt Older coversand I. Repeated avulsions of wide yet shallow channels have left deflection marks in the micro-topography. The high plain is comparable to flat and broad alluvial fans emanating from the Pevele. At the end of the Weichselian Upper Pleniglacial, under a dryer climate, small elongated dunes (sand or sand alternating with loess) formed in the center of the plain or alongside the Pevele border (OSL dates about 19 and 15 ka). This phase is at least partly contemporary with the Beuningen gravel bed. An ultimate deflation phase is imputed to the Younger Dryas. This last aeolian deposit is even fainter and looks like a thin yet continuous sheet restricted to a large southern part of the plain. Slightly scoured Late Glacial and Holocene streams can be found in the last state of Pleniglacial channels (C14 dates since 12 345 BP). The former main Pleniglacial channels may thus constitute the overbank channel of the faint Late Glacial and Holocene channels. During the Holocene, the water table rose and consecutively the peat spread in the lower areas of the plain. The widely spread yet often thin peat gradually takes over and blurs the Pleistocene topography. We have crossed three Late Glacial-Holocene channel systems (two Scarpe minor channels and an affluent). Two of them are detailed. The Vred meander bears traces of archaeological remains (a Bronze Age bridge-like structure from around 1000-800 AD) and of anthropic piracy in the upstream “Satis” during the Early Middle Ages (calcareous tufa loam flood deposits).
![Research paper thumbnail of Lambersart « les Conquérants » (Vallée de la Deûle, Nord de la France) : une transition versant-fond de vallée au Début glaciaire et Pléniglaciaire wiechselien________[Lambersart «Les Conquérants» (Deûle Valley, North of France): A Weichselian Early-Pleniglacial Slopebottom Valley Transition]](https://attachments.academia-assets.com/31026778/thumbnails/1.jpg)
La séquence observée dans la tranchée de Lambersart « les Conquérants » se compose d’un limon coq... more La séquence observée dans la tranchée de Lambersart « les Conquérants » se compose d’un limon coquillier surmonté d’alluvions grossières. L’ensemble est recouvert de plusieurs mètres de loess du Pléniglaciaire supérieur weichselien. Les données palynologiques et malacologiques indiquent que le dépôt de limon coquillier s’est effectué dans les conditions froides et humides du Début glaciaire, évoluant vers un interstade plus tempéré, dans un environnement de fond de vallée, au pied du versant du Pays de Weppes. Une érosion marquée, attribuée au début du Pléniglaciaire, affecte versant et fond de vallée. Elle démantèle les sols du Début glaciaire et leur contenu archéologique ou paléontologique. En partie basse, des lits de sable et limon se déposent. Cette accumulation de fond de vallée est alors séparée du versant par une zone de transition constituée de petits chenaux peu profonds et très mobiles, emplis de gravier, de sable et d’une seconde génération de limon coquillier. Par la suite, les accumulations loessiques pléniglaciaires ont entraîné la progradation du versant sur les formations de fond de vallée antérieures, tout en les protégeant. Un recensement de données disponibles met en évidence la forte extension de dépôts similaires sous le versant actuel du pays de Weppes et à Seclin dans une vallée affluente.
The Lambersart «les Conquérants» trench sequence is made of a shelly loam topped by coarse alluviums. The whole is covered by several meters thick pleniglacial loess. The palynological and malacological data shows that this shelly loam deposit occured during Early Glacial, in cold and moist conditions and ended in a more temperate interstadial. It settled at the valley bottom, down the Weppes Country slope. Significant erosion (attributed to the Pleniglacial) occurred on the slope and the valley bottom. It broke Early glacial soils and disturbed their archaeological and palaeontological remains. Sandy and silty beds settled in the lower part. Thereafter, this valley deposit is broken appart from the slope by a transitional aera. The latter shows narrow; deepless and mobile channels infilled by sand, gravels, and a younger shelly loam. Afterwards, pleniglacial loess accumulations grew up the slope on the previous valley bottom formations, yet protecting them. A overall look at available data indicates the large extend of similar deposits under the actual slope of the Weppes Country and in the tributary valley of Seclin.
![Research paper thumbnail of L'Enregistrement tardiglaciaire de Dourges (Nord de la France, Bassin de la Deûle) : Evolution d'une zone lacustre et gisements archéologiques associés________[The Dourges Late Glacial record (North of France, Deûle river basin): lacustrine area evolution and connected archaeological sites]](https://attachments.academia-assets.com/31026744/thumbnails/1.jpg)
Une dépression dans le fond de la vallée de la Deûle, au pied du versant crayeux de la Gohelle (b... more Une dépression dans le fond de la vallée de la Deûle, au pied du versant crayeux de la Gohelle (bassin minier de Lens), a permis la mise en place et la conservation de sédiments tardiglaciaires lacustres et palustres avec des sites paléontologiques et archéologiques associés. La nature des dépôts est commandée par les variations d’humidité. Un épisode lacustre est daté du Bølling. Il est caractérisé par le développement d’une biocénose aquatique (poissons et mollusques). Un fragment de harpon magdalénien et les restes d’un aurochs de grande taille ont été trouvés dans le tuf lacustre. Le Dryas moyen se distingue par un assèchement et un hiatus stratigraphique. Après une nouvelle période d’hydrologie plus marquée (récurrence de crues de courte durée), la zone redevient marécageuse à l’Allerød. Elle est fréquentée par des chasseurs Federmesser ainsi qu’en témoigne une halte de chasse qui a livré des éléments fugaces mais caractéristiques : sagaie, pointe en os barbelée, pointe de flèche. La fin de l’Allerød se caractérise par un retour à des conditions sèches et la formation d’un sol humifère. Le refroidissement du Dryas récent engendre une déstabilisation du versant et le début du comblement de la dépression par des colluvions limoneuses. Leur base a livré un crâne d’élan.
A dipped area in the bottom of the Deûle valley, bottom the chalky slope of the Gohelle country (Lens mining basin), has yielded Late Glacial deposits with palaeontological remains and archaeological artifacts. The nature of the deposits appears linked to humidity variations. A lacustrine episode dated from the Bølling is characterized by the development of an aquatic biocoenosis (fish and mollusks). A fragment of a Magdalenian harpoon and the remains of a large wild ox were discovered in the lacustrine tufa. The Older Dryas corresponds to dry conditions and a stratigraphic hiatus. After a new increase in hydrological conditions (short floodings), the area turns marshy again during the Allerød. Federmesser hunters are represented by assegai, barbed bone points and arrow points. The end of the Allerød corresponds to a return to dry conditions and the formation of humic soil. During the Younger Dryas the cooling provokes slope erosion and the filling up of the hollow by silt colluvium. An elk skull was discovered at the base of this last deposit.
![Research paper thumbnail of Formations sédimentaires et évolution de la vallée de la Deûle depuis le Pléniglaciaire supérieur à Houplin-Ancoisne (Nord de la France)________[Sedimentary formations and evolution of the Deûle valley since the Upper Pleniglacial at Houplin-Ancoisne (northern France)]](https://attachments.academia-assets.com/31026616/thumbnails/1.jpg)
Dans la région d'Houplin-Ancoisne (vallée de la Deûle, Nord), l'ampleur de la sédimentation loess... more Dans la région d'Houplin-Ancoisne (vallée de la Deûle, Nord), l'ampleur de la sédimentation loessique du Pléistocène supérieur dans le fond de vallée a favorisé la conservation des dépôts fluviatiles antérieurs, sur une bande de plus de 3 km de large et parfois jusqu'à 22 m d'épaisseur. Un transect partiel de la vallée de la Deûle a révélé un chenal tardiglaciaire qui incise sur environ 3 m les dépôts antérieurs, créant une terrasse pléistocène supérieur / Tardiglaciaire. Son remblaiement débute précocément au Bölling, mais la majeure partie du comblement est datée du Dryas récent : après un dépôt lité relativement riche en débris végétaux (environ 1 m), la partie supérieure (0,9 m) est azoïque et s'accumule rapidement (après 12350-12150 cal. BP). Ce comblement terminal du Dryas récent témoigne d'une relative sécheresse et d'une modification de la morphologie du chenal. L'incision holocène, décalée par rapport au chenal tardiglaciaire, est plus modérée. Elle dégage une morphologie de basses terrasses creusées dans les nappes fluviatiles antérieures et le loess qui les scelle. Après un dépôt grossier, la tourbe se développe à partir du Boréal, déborde du lit mineur et ennoie les zones les plus basses du fond de vallée. La palynozone atlantique repérée dans la tourbe offre l'image d'un paysage boisé dominé par le Tilleul avec des traces d'anthropisation fugaces. Depuis le Néolithique, la micro-topographie du bas de versant à proximité de la rive droite est peu à peu régularisée par les colluvions.
In Houplin-Ancoisne area (Deûle valley, north of France), the size of the upper pleistocene loessic sedimentation in the bonom of the valley facilitated the former river deposits conservation, over more than a 3 km large belt, up to 22 m thick. A partial cross-section of the valley revealead a
lateglacial channel which incises the former deposits on about 3 m depth creating an upper pleistocene terrace. Its filling begins earlier in the Bolling phase, but the main filling dates from the Younger Dryas phase : after a bedded deposit quite rich in vegetal remains (around 1 m), the upper part (0.9 m)
is azoïc and fast-setting (later 12350-12150 cal. BP). The final filling of the Younger Dryas gives evidence of a relative dryness and a modification of the channel morphology. The holocene incision, shifted from the tardiglacial chennal, is more moderate. It created low terraces digged into the frontal fluvial
layers and the loess that fixes them in. After a coarse sedimentary deposit, the peat developps from the Boreal, oveflows the mean bed and inundates the valley lowest zone. Atlantic palynozone spoted in the peat gave a wooded landscape where lime trees prevail with fugace anthropogenic pollens. Since the Neolithic period, the microtopography of the bonom slope near the right bank is progressively sorted out by the colluviums.
All papers by Laurent Deschodt
La Découverte, Paris, 2012
Quaternaire, 23 (1), 117-127, 2012
Quaternaire, 23 (1), 87-116, 2012
Quaternaire, 22 (4), 307-325, 2011
Revue du Nord. Hors Série. Collection Histoire n°26, 45 - 77, 2011
Les Cahiers de l'Inrap, 3, Paris, Inrap, 8-12, 2010
Revue du Nord. Hors Série. Collection Art et Archéologie, 14, 19-27, 2009
Archaeological Reports Ghent University, 5, 333-361, 2009
Revue du Nord, 91, n°383, 19-27, 2009
Quaternaire, 19, (4), 2008, p. 309-333, 2008
Les Cahiers de l'Inrap, 2, 2008
Revue du Nord, tome 88, n°368, 9-31, 2006
Quaternaire, 17, (3), 259-267, 2006
Presses Universitaires Blaise-Pascal, collection « Nature et Sociétés », 3, 97-102, 2006
Quaternaire, 16 (3), 2005, 229-252, 2005
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Mean papers by Laurent Deschodt
The Deûle River has scoured the chalk substratum in two places in the vicinity of Lille. The older scouring is under the lower slopes of the Weppes country. It occurred prior to the Weichselian. It was still active in the Early Glacial. A more recent scouring, predating the Upper Pleniglacial, appeared one kilometre eastward. The Hegel street excavations allow direct observation of a portion of the in-filled channel; a 12,5 m thick sandy alluvium deposited in small channels associated with indications of cold. It dated to about the end of the Pleniglacial (17 960 ± 90 BP, i.e. 21 639 ± 361 cal. BP). These deposits gave way to -apparently continuous- fluvio-aeolian formations, bedded and clayey at first, becoming loess-like in the upper strata. According to the C14 date and to two OSL dates (21.7 ± 1.9 and 23.7 ± 2,0 ka), this silty, primarily aeolian formation seems to have been rapidly deposited (about 21.7 ka). These first dates of loess upper valley infilling from northern France should be considered with caution. They appear to indicate the simultaneity of aeolian deposit on slope and valley bottoms at the end of the Pleniglacial, earlier than in the sandy valleys of Belgium and Netherlands.
The Scarpe plain is a depression in the Eocene marine sands between the Pevele and Ostrevant regions. A “high plain” is distinguished northwards from a “low plain” southwards. The infilling is mainly sandy (with a peaty part in the low plain). Numerous micro-topographies are scattered throughout the plain. The small water courses which drain the plain are not proportionate to its size. The laying of a gas pipeline across the plain was preceded by archaeological borings. We present the stratigraphy as a long crosssection and propose an evolution scenario for the plain since the Weichselian Upper Pleniglacial. The sedimentation consists mainly of sandy beds alternating with loamy laminae. This alluvial sheet, present everywhere in the plain, was deposited under strongly contrasted hydrological conditions during the Weichselian Upper Pleniglacial (OSL dates about 34, 21 and 21 ka). It may be correlated to the northern sand belt Older coversand I. Repeated avulsions of wide yet shallow channels have left deflection marks in the micro-topography. The high plain is comparable to flat and broad alluvial fans emanating from the Pevele. At the end of the Weichselian Upper Pleniglacial, under a dryer climate, small elongated dunes (sand or sand alternating with loess) formed in the center of the plain or alongside the Pevele border (OSL dates about 19 and 15 ka). This phase is at least partly contemporary with the Beuningen gravel bed. An ultimate deflation phase is imputed to the Younger Dryas. This last aeolian deposit is even fainter and looks like a thin yet continuous sheet restricted to a large southern part of the plain. Slightly scoured Late Glacial and Holocene streams can be found in the last state of Pleniglacial channels (C14 dates since 12 345 BP). The former main Pleniglacial channels may thus constitute the overbank channel of the faint Late Glacial and Holocene channels. During the Holocene, the water table rose and consecutively the peat spread in the lower areas of the plain. The widely spread yet often thin peat gradually takes over and blurs the Pleistocene topography. We have crossed three Late Glacial-Holocene channel systems (two Scarpe minor channels and an affluent). Two of them are detailed. The Vred meander bears traces of archaeological remains (a Bronze Age bridge-like structure from around 1000-800 AD) and of anthropic piracy in the upstream “Satis” during the Early Middle Ages (calcareous tufa loam flood deposits).
The Lambersart «les Conquérants» trench sequence is made of a shelly loam topped by coarse alluviums. The whole is covered by several meters thick pleniglacial loess. The palynological and malacological data shows that this shelly loam deposit occured during Early Glacial, in cold and moist conditions and ended in a more temperate interstadial. It settled at the valley bottom, down the Weppes Country slope. Significant erosion (attributed to the Pleniglacial) occurred on the slope and the valley bottom. It broke Early glacial soils and disturbed their archaeological and palaeontological remains. Sandy and silty beds settled in the lower part. Thereafter, this valley deposit is broken appart from the slope by a transitional aera. The latter shows narrow; deepless and mobile channels infilled by sand, gravels, and a younger shelly loam. Afterwards, pleniglacial loess accumulations grew up the slope on the previous valley bottom formations, yet protecting them. A overall look at available data indicates the large extend of similar deposits under the actual slope of the Weppes Country and in the tributary valley of Seclin.
A dipped area in the bottom of the Deûle valley, bottom the chalky slope of the Gohelle country (Lens mining basin), has yielded Late Glacial deposits with palaeontological remains and archaeological artifacts. The nature of the deposits appears linked to humidity variations. A lacustrine episode dated from the Bølling is characterized by the development of an aquatic biocoenosis (fish and mollusks). A fragment of a Magdalenian harpoon and the remains of a large wild ox were discovered in the lacustrine tufa. The Older Dryas corresponds to dry conditions and a stratigraphic hiatus. After a new increase in hydrological conditions (short floodings), the area turns marshy again during the Allerød. Federmesser hunters are represented by assegai, barbed bone points and arrow points. The end of the Allerød corresponds to a return to dry conditions and the formation of humic soil. During the Younger Dryas the cooling provokes slope erosion and the filling up of the hollow by silt colluvium. An elk skull was discovered at the base of this last deposit.
In Houplin-Ancoisne area (Deûle valley, north of France), the size of the upper pleistocene loessic sedimentation in the bonom of the valley facilitated the former river deposits conservation, over more than a 3 km large belt, up to 22 m thick. A partial cross-section of the valley revealead a
lateglacial channel which incises the former deposits on about 3 m depth creating an upper pleistocene terrace. Its filling begins earlier in the Bolling phase, but the main filling dates from the Younger Dryas phase : after a bedded deposit quite rich in vegetal remains (around 1 m), the upper part (0.9 m)
is azoïc and fast-setting (later 12350-12150 cal. BP). The final filling of the Younger Dryas gives evidence of a relative dryness and a modification of the channel morphology. The holocene incision, shifted from the tardiglacial chennal, is more moderate. It created low terraces digged into the frontal fluvial
layers and the loess that fixes them in. After a coarse sedimentary deposit, the peat developps from the Boreal, oveflows the mean bed and inundates the valley lowest zone. Atlantic palynozone spoted in the peat gave a wooded landscape where lime trees prevail with fugace anthropogenic pollens. Since the Neolithic period, the microtopography of the bonom slope near the right bank is progressively sorted out by the colluviums.
All papers by Laurent Deschodt
The Deûle River has scoured the chalk substratum in two places in the vicinity of Lille. The older scouring is under the lower slopes of the Weppes country. It occurred prior to the Weichselian. It was still active in the Early Glacial. A more recent scouring, predating the Upper Pleniglacial, appeared one kilometre eastward. The Hegel street excavations allow direct observation of a portion of the in-filled channel; a 12,5 m thick sandy alluvium deposited in small channels associated with indications of cold. It dated to about the end of the Pleniglacial (17 960 ± 90 BP, i.e. 21 639 ± 361 cal. BP). These deposits gave way to -apparently continuous- fluvio-aeolian formations, bedded and clayey at first, becoming loess-like in the upper strata. According to the C14 date and to two OSL dates (21.7 ± 1.9 and 23.7 ± 2,0 ka), this silty, primarily aeolian formation seems to have been rapidly deposited (about 21.7 ka). These first dates of loess upper valley infilling from northern France should be considered with caution. They appear to indicate the simultaneity of aeolian deposit on slope and valley bottoms at the end of the Pleniglacial, earlier than in the sandy valleys of Belgium and Netherlands.
The Scarpe plain is a depression in the Eocene marine sands between the Pevele and Ostrevant regions. A “high plain” is distinguished northwards from a “low plain” southwards. The infilling is mainly sandy (with a peaty part in the low plain). Numerous micro-topographies are scattered throughout the plain. The small water courses which drain the plain are not proportionate to its size. The laying of a gas pipeline across the plain was preceded by archaeological borings. We present the stratigraphy as a long crosssection and propose an evolution scenario for the plain since the Weichselian Upper Pleniglacial. The sedimentation consists mainly of sandy beds alternating with loamy laminae. This alluvial sheet, present everywhere in the plain, was deposited under strongly contrasted hydrological conditions during the Weichselian Upper Pleniglacial (OSL dates about 34, 21 and 21 ka). It may be correlated to the northern sand belt Older coversand I. Repeated avulsions of wide yet shallow channels have left deflection marks in the micro-topography. The high plain is comparable to flat and broad alluvial fans emanating from the Pevele. At the end of the Weichselian Upper Pleniglacial, under a dryer climate, small elongated dunes (sand or sand alternating with loess) formed in the center of the plain or alongside the Pevele border (OSL dates about 19 and 15 ka). This phase is at least partly contemporary with the Beuningen gravel bed. An ultimate deflation phase is imputed to the Younger Dryas. This last aeolian deposit is even fainter and looks like a thin yet continuous sheet restricted to a large southern part of the plain. Slightly scoured Late Glacial and Holocene streams can be found in the last state of Pleniglacial channels (C14 dates since 12 345 BP). The former main Pleniglacial channels may thus constitute the overbank channel of the faint Late Glacial and Holocene channels. During the Holocene, the water table rose and consecutively the peat spread in the lower areas of the plain. The widely spread yet often thin peat gradually takes over and blurs the Pleistocene topography. We have crossed three Late Glacial-Holocene channel systems (two Scarpe minor channels and an affluent). Two of them are detailed. The Vred meander bears traces of archaeological remains (a Bronze Age bridge-like structure from around 1000-800 AD) and of anthropic piracy in the upstream “Satis” during the Early Middle Ages (calcareous tufa loam flood deposits).
The Lambersart «les Conquérants» trench sequence is made of a shelly loam topped by coarse alluviums. The whole is covered by several meters thick pleniglacial loess. The palynological and malacological data shows that this shelly loam deposit occured during Early Glacial, in cold and moist conditions and ended in a more temperate interstadial. It settled at the valley bottom, down the Weppes Country slope. Significant erosion (attributed to the Pleniglacial) occurred on the slope and the valley bottom. It broke Early glacial soils and disturbed their archaeological and palaeontological remains. Sandy and silty beds settled in the lower part. Thereafter, this valley deposit is broken appart from the slope by a transitional aera. The latter shows narrow; deepless and mobile channels infilled by sand, gravels, and a younger shelly loam. Afterwards, pleniglacial loess accumulations grew up the slope on the previous valley bottom formations, yet protecting them. A overall look at available data indicates the large extend of similar deposits under the actual slope of the Weppes Country and in the tributary valley of Seclin.
A dipped area in the bottom of the Deûle valley, bottom the chalky slope of the Gohelle country (Lens mining basin), has yielded Late Glacial deposits with palaeontological remains and archaeological artifacts. The nature of the deposits appears linked to humidity variations. A lacustrine episode dated from the Bølling is characterized by the development of an aquatic biocoenosis (fish and mollusks). A fragment of a Magdalenian harpoon and the remains of a large wild ox were discovered in the lacustrine tufa. The Older Dryas corresponds to dry conditions and a stratigraphic hiatus. After a new increase in hydrological conditions (short floodings), the area turns marshy again during the Allerød. Federmesser hunters are represented by assegai, barbed bone points and arrow points. The end of the Allerød corresponds to a return to dry conditions and the formation of humic soil. During the Younger Dryas the cooling provokes slope erosion and the filling up of the hollow by silt colluvium. An elk skull was discovered at the base of this last deposit.
In Houplin-Ancoisne area (Deûle valley, north of France), the size of the upper pleistocene loessic sedimentation in the bonom of the valley facilitated the former river deposits conservation, over more than a 3 km large belt, up to 22 m thick. A partial cross-section of the valley revealead a
lateglacial channel which incises the former deposits on about 3 m depth creating an upper pleistocene terrace. Its filling begins earlier in the Bolling phase, but the main filling dates from the Younger Dryas phase : after a bedded deposit quite rich in vegetal remains (around 1 m), the upper part (0.9 m)
is azoïc and fast-setting (later 12350-12150 cal. BP). The final filling of the Younger Dryas gives evidence of a relative dryness and a modification of the channel morphology. The holocene incision, shifted from the tardiglacial chennal, is more moderate. It created low terraces digged into the frontal fluvial
layers and the loess that fixes them in. After a coarse sedimentary deposit, the peat developps from the Boreal, oveflows the mean bed and inundates the valley lowest zone. Atlantic palynozone spoted in the peat gave a wooded landscape where lime trees prevail with fugace anthropogenic pollens. Since the Neolithic period, the microtopography of the bonom slope near the right bank is progressively sorted out by the colluviums.
Le site du Vignoble occupe la jonction entre le fond de vallée de l’Escaut et un talweg descendant du versant. Un cône de déjection pléistocène a développé une petite zone basse en périphérie. Elle est comblée par un limon colluvié attribué au début de l’Holocène, puis par 1,5 m de tourbe formée durant l’Atlantique. L’enregistrement bénéficie de sept dates radiocarbone, comprises entre 7 310 ± 59 BP (soit environ 8 100 ans cal. BP) et 5 422 ± 43 BP (soit environ 6 300 cal. BP), et d’une étude palynologique. Au cours de l’Atlantique, le diagramme pollinique présente un enregistrement récurrent de rudérales, parfois associé à un recul des essences forestières. Cependant, l’analyse permet d’exclure une causalité anthropique automatique. En revanche, différentes phases de recul de la chênaie semblent être liées à des variations des conditions édaphiques. La dernière phase humide, la plus importante, débute au sommet de la tourbe et fait suite aux premiers indices d’agriculture néolithique.