Évolution morphologique et sédimentaire de la plaine alluviale d'un espace urbanisé (Tours, Indre-et-Loire, France)

http://racf.revues.org/1985National audienceUrban areas located in floodplains offer a great geo-archaeological potential for the comprehension of fluvial dynamics on long term and its relationship with land occupation, as they allow exploiting many survey data of the basement. In the floodplain of Tours, shared by the River Loire and Cher river, relations between human societies and environment are the subject of an interdisciplinary work within the frame of an archaeological program initiated in the late 1960's. A sedimentary database including 1309 surveys has been created then exploited in a geographic information system to produce geomorphological and geostatical models. The stratigraphy and chronology of the alluvial filling were also studied with surveys and 14C and OSL dating obtained in the course of archaeological prospections. The combined results provide a new reading of the morphological evolution of the floodplain of Tours from the Weichselian to nowadays.Les zones urbaines situées dans les plaines alluviales offrent un grand potentiel géo-archéologique pour la compréhension de la dynamique fluviale dans la longue durée et ses relations avec l'occupation du sol en contexte anthropisé, car elles permettent d'exploiter des très nombreuses données de sondages du sous-sol. Dans la plaine alluviale de Tours, partagée par la Loire et le Cher, les relations sociétés/milieux font l'objet de travaux interdisciplinaires autour d'un programme de recherches archéologiques initié à la fin des années 1960. Une base de données sédimentaires comprenant 1309 sondages a été constituée puis exploitée dans un système d'information géographique pour produire des modèles géostatistiques et géomorphologiques. La stratigraphie et la chronologie du remplissage alluvial ont également été étudiées avec des sondages et des datations 14C et OSL obtenues à l'occasion d'opérations archéologiques. Les résultats croisés permettent une lecture renouvelée de l'évolution morphologique de la plaine alluviale tourangelle du Weichsélien à nos jours

Significance of the correlation between the electrical conductivity dataset and lithology in Pleni-Lateglacial and Holocene alluvial archives.A case study: the Choisille catchment (SW Paris Basin, France)

Introduction Alluvial floodplains constitute rapidly evolving sedimentary environments, registering both climate changes and human impact. In the Paris Basin, the floodplain filling is generally composed of two major units (Pastre et al., 2003; Macaire et al., 2006): coarse deposits (sands and gravels) from the Pleniglacial or Late Glacial in the lower part and fine deposits (clayey-silty to carbonated or peaty sediments) from the Late Glacial and Holocene in the upper part. Because of its hi..

Evolution morpho-sédimentaire de la vallée de la Choisille (Sud-Ouest du Bassin Parisien, France) depuis le Weichsélien (spécificité de l'impact climatique et anthropique en Europe du Nord-Ouest)

La variabilité spatio-temporelle de l évolution morpho-sédimentaire du fond de la vallée de la Choisille (bassin versant : 288 km ), affluent de la Loire moyenne dans le sud-ouest du Bassin parisien (37), a été étudiée par 78 forages (8 transects), prospection géophysique, analyses sédimentologiques et datations 14C et OSL. Huit phases d évolution du système fluviatile depuis le début Weichsélien ont été définies et corrélées avec les données palynologiques et archéologiques locales, afin de comprendre l impact des facteurs forçants : climat ou/et anthropisation. Du Weichsélien jusqu au début du Subatlantique, l'activité d'incision ou de sédimentation de la Choisille a évolué sous contrôle climatique strict. Depuis l Allerød, cette évolution a été différente de celles observées sur d autres rivières en Europe du Nord-Ouest, indiquant des spécificités climatiques et géologiques régionales. Dès l Âge du Bronze, la rivière a évolué sous contrôle climatique et anthropique ; l'impact anthropique sur la sédimentation fut prépondérant, mais très variable dans le temps et l'espace au sein du bassin selon les potentialités agricoles des secteurs considérés.The spatio-temporal variability of the Choisille valley morpho-sedimentary evolution (catchment: 288 km ), a tributary of the middle Loire River in the south-western Parisian Basin (37), was studied through 78 core-drillings (8 transects), geophysical prospecting, sedimentological analyses and 14C and OSL dating. Eight phases of fluvial system evolution were defined and correlated with palynological and archaeological dataset, in order to highlight the impact of forcing factors: climate and/or human activity. From the Weichselian up to the Subatlantic, the fluvial incision or sedimentation activity has strictly evolved under climate control. Since the Allerød, this evolution was different from what has been observed on other rivers of north-western Europe, indicating regional climatic or geological specificities. Since the Bronze Ages, the river has evolved under climatic and human control; the anthropogenic impact on sedimentation was dominant, but spatio-temporaly variable in the catchment, in relationship with the agricultural potentialities of the different areas.TOURS-Bibl.électronique (372610011) / SudocSudocFranceF

Chapitre 3. Approche géomorphologique : sols et sociétés aux environs de Châteauneuf-du-Rhône

Afin de mieux comprendre les relations sociétés-milieux dans la longue durée, le sol, le sous-sol et le paysage sont devenus, ces dernières décennies, des objets d’étude de l’archéologie, au même titre que les vestiges. Parmi les approches transdisciplinaires pouvant être mises en œuvre, deux grandes catégories complémentaires car interférentes peuvent être distinguées : les approches concernant l’évolution de l’environnement physique et abiotique (géomorphologie, sédimentologie, pédologie, g..

Morphological and sedimentary evolution of an alluvial floodplain in an urban area: geoarchaeological approaches and applications (Tours, France)

International audienceUrban zones on alluvial plains offer considerable geoarchaeological potential for understanding river dynamics over large time spans and their relationship with land use, because of the extensive subsoil data that is available. In the alluvial plain of Tours, lying between the Loire and the Cher, multidisciplinary studies of the relationships between societies and environment have been conducted as part of an archaeological research programme launched in the 1960s. A sedimentary database containing data for 1309 surveys has been compiled and assembled in a geographic information system to produce geostatistical models of valley bottom geomorphology. The stratigraphy and chronology of alluvial filling have also been studied with information and C14 and OSL dating obtained during archaeological operations. Taken together, the results offer a new interpretation of the morphological evolution of the alluvial plain of Tours from the Weichselian to the present day, by providing new information that either validates or invalidates previous hypotheses: bedrock incision prior to the end of the Weichselian Upper Pleniglacial, coarse sedimentation during the Lateglacial, relative morphological stability up to the late Holocene. The morphological context of the first human settlements, which are not concentrated on the low alluvial reliefs, and the role of urbanization conditions on the present morphology of the valley floor are also presented. This applied study shows the relevance of combining different methodological approaches

Spatio-temporal evolution of the Choisille River (southern Parisian Basin, France) during the Weichselian and the Holocene as a record of climate trend and human activity in north-western Europe

International audienceThe morpho-sedimentary evolution of the Choisille floodplain (lowland river, catchment: 288 km2), a tributary of the River Loire in the south-western Parisian Basin, was studied through 61 core drillings along eight transects and a geophysical survey located in four stretches of the river: stretches A and B correspond to two sub-catchments, and stretches C and D are in the main valley. Sixty 14C and four OSL datings were obtained, and sediments were analysed on seven reference cores. Eight phases of evolution differing markedly from the evolution of more northern areas in the Parisian Basin and north-western Europe were identified from spatio-temporal distribution of nine lithological facies. The deepest incision phase (1) occurred during the first part of the Weichselian, followed by the deposition of a gravelly-sandy unit (phase 2) during the Middle Pleniglacial, which was deeply incised (phase 3), probably during the Bölling. From the Allerød up to the last third of the Boreal (phase 4), sedimentation was continuously dominated by peaty deposits, with no evidence of either increased hydraulic energy during the Younger Dryas, or of incision during the LateGlacial–Holocene transition. This trend seems to reflect the specificity of the south-western Parisian Basin climate from the Late Weichselian up to the end of the Boreal, due to the influence of the Atlantic Ocean, compared to more northern areas where the climate was more continental. The downstream incision trend during the last third of the Boreal up to the Subatlantic (phases 5 and 6) indicates a sharp increase in precipitation and vegetation cover; the lack of peaty sediments, widespread in north-western Europe, and also of precipitated carbonates frequent in the Parisian Basin, seems to be due to local physiographic characteristics. The main part of the sediment filling, which is principally silty and retrograde, began during the Subatlantic (phase 7 and 8) as a result of deforestation of the plateaux for crop farming. High human-induced sediment yield and storage concealed the possible impacts of climate change on fluvial dynamics: lithological facies change from phase 7 to 8 can only indicate the autogenic morphological evolution of the floodplain in accretion. The non-univocal upstream–downstream variation in the start of phase 7 shows that sediment yield varied in space and time in the catchment, particularly in relation to the agricultural potential of the different areas; this observation could be used to testify human-induced sedimentation in other catchments

Évolution de la sédimentation fluviatile dans le bassin de la Choisille (sud-ouest du Bassin Parisien, France) en contexte d'anthropisation à l'Holocène : premiers résultats

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Significance of the correlation between the electrical conductivity dataset and lithology in Pleni-Lateglacial and Holocene alluvial archives.A case study: the Choisille catchment (SW Paris Basin, France)

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Évolution de la distribution des stocks alluviaux dans une vallée du sud-ouest du Bassin parisien (France) depuis le Pléniglaciaire supérieur : impacts du climat et de l'anthropisation

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