Comment mesurer l'impact érosif des dynamiques de l'occupation du sol ? Approche pluridisciplinaire dans la vallée de la Choisille (Indre-et-Loire, France)

International audienceThe Choisille valley, in the north of Tours (37), has been a laboratory for a multidisciplinary experiment which was aimed at measuring the impact of human activities on soil erosion, conducted within the ECLIPSE II program. We propose a synthesis of the acquired knowledge about land use evolution based on archaeological, written and environmental data analyzed within a GIS. This information documents the settlement and landscape dynamics at different time and space scales, and provides a partial explanation to the variation of sediments recording within the Choisille valley.La vallée de la Choisille au nord de Tours (37) a été un laboratoire pour une expérience multidisciplinaire visant à mesurer l'impact des activités anthropiques sur l'érosion des sols, expérience réalisée dans le cadre du programme ECLIPSE II. Nous proposons la synthèse des connaissances acquises sur l'évolution de l'occupation du sol à partir des données archéologiques, écrites, planimétriques et environnementales analysées au sein d'un SIG. Ces informations documentent les dynamiques de l'habitat et du paysage à différentes échelles de temps et d'espace, et permettent en partie d'expliquer les variations de l'enregistrement sédimentaire au sein de la vallée de la Choisille

Occupation du sol et impact érosif dans la vallée de la Choisille (France, Indre-et-Loire). Approches croisées pour la restitution des paysages anciens.

International audienceThe Choisille catchment, a tributary of the Loire in the north of Tours, is used since 2003 as a common geographical framework for investigation of geologists and archaeologists teams with the aim of studying the main steps of land use of this space in the long term and the impact of human activities on soil erosion and sedimentation in wetlands during the Holocene. Archaeological fieldwalking surveys, analysis of medieval and modern written sources and sedimentological and palynological cores-drillings have been made. The comparison of these works highlights an anthropogenic forcing on sediment fluxes since the Bronze Age, with an increasing intensity since the Middle Ages, but also raises questions about discrepancies between the different types of sources. The limits of each discipline and the "blind spots" between them stress their complementarities and the necessity to cross them to approach the ancient realities.Le bassin-versant de la Choisille, affluent de la Loire au nord de Tours, sert depuis 2003 de cadre géographique commun d'investigation pour les équipes de géologues et d'archéologues dont le but est de mesurer, dans la longue durée, les principales phases d'occupation humaine de l'espace et l'impact des activités anthropiques sur l'érosion des sols et la sédimentation dans les zones humides durant l'Holocène. Des prospections archéologiques de surface, le dépouillement des sources écrites médiévales et modernes et des carottages sédimentologiques et palynologiques ont été réalisés. Le croisement de ces travaux met en lumière un forçage anthropique sur les flux sédimentaires dès l'Âge du Bronze, avec une intensité plus forte depuis le Moyen Âge, mais amène également à s'interroger sur les discordances observées entre les différents types de sources. Les limites propres à chaque discipline et les " angles morts " entre elles soulignent leur complémentarité et la nécessité de les multiplier pour approcher les réalités anciennes

La vallée de la Choisille (sud du Bassin parisien – France) : le paysage végétal depuis le Tardiglaciaire jusqu’à l’époque actuelle d’après les données paléopalynologiques

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La géostatistique en contexte préventif : un outil robuste d'aide à la stratigraphie

International audienc

La géostatistique en contexte préventif : un outil robuste d'aide à la stratigraphie

International audienc

La géostatistique en contexte préventif : un outil robuste d'aide à la stratigraphie

International audienc

La géostatistique en contexte préventif : un outil robuste d'aide à la stratigraphie

International audienc

La géostatistique en contexte préventif : un outil robuste d'aide à la stratigraphie

International audienc

Human impact variability on soil erosion during the Holocene based on valley floor sediments study in a Parisian basin fluvial catchment (France): crossing sedimentological, archaeological and palynological proxies

International audienceThis work is part of the French CNRS ECLIPSE program « Impact anthropique sur l'érosion des sols et la sédimentation dans les zones humides associées durant l'Holocène ». It aims to reconstitute the evolution of human impact on soil erosion at various periods via the study of Holocene sedimentary archives. In this framework the Choisille catchment (288 km²; elevation: 50 - 200 m), tributary of the River Loire near Tours (France), has been the subject of an interdisciplinary study (sedimentology, geophysics, archaeology, palynology). 3 areas are investigated: a downstream stretch, a silicated sub-catchment area and a carbonated sub-catchment area. In the downstream stretch, located near ancient populated areas, drillings were performed along cross sections through valley floor alluviums. They show that a more or less organic clayey silty sedimentation started at the beginning of the Holocene. The sedimentation rates strongly increased at the beginning of the Subbatlantic (Bronze Age), simultaneously with the anthropogenic pressure advent (on set of agriculture), as shown by archaeological and palynological evidences (agricultural settlements, massive loggings on slopes, stockbreeding on valley-floor grasslands). In the silicated sub-catchment area, located upstream, drillings have shown that clayey silty sedimentation began at the end of the Roman Period, continued during the Early Middle Ages and increased during the High Middle Ages. Spatial archaeological prospecting has revealed a faint anthropogenic presence at the Roman Period, then a decline of population until the High Middle Ages, characterised by an agricultural revival. Palynological analyses have shown that, in this area, grasslands were dominant since the Early Middle Ages, with an increase in cereal cultures at the beginning of the High Middle Ages. In the carbonated sub-catchment area, drillings have shown that the more or less organic clayey silty sedimentation has begun during the Bronze Age. Sedimentation rates have increased during the Modern era and the Contemporary history. The high fine sediment storage appeared and evolved differently, depending on the considered period and catchment valley area, due to variation of soil erosion. The difference between a fine, early and regularly increasing sedimentation in the downstream site and the later, intense and non-univocal sedimentation in the sub-catchments doesn't seem to be strictly resulting from natural factors. This idea and the palaeoenvironnemental dataset show that the fine sedimentation basically results from an anthropogenic impact, notably in the sub-catchments. Therefore soil exploitation by humans seems to be the main sedimentary production factor. This work mainly shows that anthropogenic impact (age of appearance, intensity) highly varies spatially, even into a little catchment. This variability would be led by the agricultural potential of the considered catchment valley area