Early Holocene Paeloenvironments (original) (raw)
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Contribution of laminated sediments to the study of holocene environmental changes
HAL (Le Centre pour la Communication Scientifique Directe), 2010
The high resolution study of laminated sediments from Lake Anterne (2063 m asl) and Lake Bourget (231.5 m asl), both located in northern French Alps, led us to reconstruct paleoenvironmental changes induced both by climate changes and human activities. Anthropogenic impacts upon lake catchment area, and in particular on erosion processes, alter the sensitivity of the sediment record to climatic variations. One of the challenges of this thesis is to disentangle the respective roles of these two factors in the changes observed throughout the study of lake sediments. The sedimentary archive of Lake Anterne covers most of the Holocene period. The evolution of erosion processes in the catchment area have been reconstructed from sedimentological analyses. A «source-to-sink» approach was applied on organic and mineral geochemical analyses. This methodological approach, coupled with quantitative indicators of erosion, allowed highlighting the evolution of soil cover. These results brought also information about the climatic or anthropogenic origin of changes in erosion patterns. During the early Holocene (9950-5450 cal. BP), a gradual evolution was recorded: establishment of vegetation and soil with pedogenesis processes (decarbonation and acidification), and then stabilization of the catchment linked to a well-developed vegetation cover. We evidenced anoxic conditions at the bottom of the lake during this period of stabilization. We interpret it as a consequence of slope stabilisation by a dense vegetation cover. A regressive story of soils, accompanied by a significant enhancement of erosion processes, began at ca. 5450 cal. BP, due to a climate reversal towards colder conditions. This regressive story was reinforced by anthropogenic impacts (deforestation, pastoral activity) during the Bronze Age (around 3400 cal. BP), the end of Iron Age-beginning of the Roman period (2400 cal. BP-150 AD) and the lower middle age (1000-1200 AD). Our interpretations were reinforced and enriched by crossing our data with climate reconstructions obtained at Anterne (temperature from chironomids) and in the region, and with paleovegetation (pollen, wood macrofossils) and archaeological data from surrounding areas. The record from Lake Le Bourget covers only the last 120 years. This archive was studied in the aim to reconstruct the evolution of the trophic level and the oxygenation at the bottom of the lake, in relation with human activities (discharge of sewage waters, agricultural activities) and climate evolution. The hydroclimatic variability at annual and pluriannual scales was also considered. Unlike Anterne, laminated sediments of Lake Le Bourget are varved. Therefore, a fair, accurate and high resolution dating was obtained. Our environmental reconstruction is based on sedimentological and geochemical analyses. The comparison between trophic level indicators and River Rhône detrital inputs highlighted the opposed effects of Rhône floods (a non-permanent tributary) on lake water quality (nutrient but also oxygen supply). Therefore, a special interest was also brought to the understanding of the factors controlling Rhône floods (anthropogenic climate/activities).
PALEOENVIRONMENTAL AND PALEOCLIMATIC RECONSTRUCTION OF THE EARLY LATE PLEISTOCENE (MIS 5a)
2016
Les gisements archéologiques de Hat et Preresa sont situés respectivement dans les vallées des rivières Jarama et Manzanares, à environ 6 km l’un de l’autre et à 18 km au sud-est de Madrid. Ils correspondent à des dépôts de plaines d’inondation ayant conservé les restes d’activités ponctuelles de groupes de néanderthaliens notamment le dépeçage de carcasses de grands mammifères il y a environ 80 000 ans. Les assemblages de petits vertébrés récupérés lors des campagnes de fouilles de 2001 à Hat et de 2003 à 2005
in Dictionnaire de la pensée écologique, D. Bourg (dir.), PUF, 2015, 35-40.
Early Holocene Leporid Processing at the LSP-1 Rockshelter, Oregon
2017
In this study a discourse analysis approach will be adopted in order to investigate different discourse types, namely institutional discourses, discourses of professionals in the field of tourism, the discourse of tourist guides, and the media discourse. The aim is to find out whether there are any recurrent discourse patterns, discourse ambiguities, and defining statements concerning alternative tourism, responsible tourism, fair tourism and ecotourism. In this study the hypothesis of discourse contamination of the alternative tourism with the types and specificity of the traditional discourse of mass tourism will also be put forward. Finally, the different sources and their complexity, as well as their ambiguities will be considered since they can be significant obstacles to the development and future of the field of tourism.
The upper pleistocene - Early Holocene fauna of Toca da Pena (Piauí, Brazil) - paleontological study
Quaternaire, 2018
Le site de la Toca da Pena correspond à une petite grotte qui se trouve dans le massif calcaire d'Antero, au sud de la Serra da Capivara et à 7 km à l'est-nord-est de la ville de Coronel José Dias. Des fouilles entreprises entre 2008 et 2014 ont permis de recueillir, associés à quelques artefacts lithiques, de nombreux vestiges osseux. Près de la moitié d'entre eux sont rapportés à Scelidodon piauiense, un paresseux terrestre de la taille d'un grand boeuf. Ce Mylodontidé est associé à Leopardus pardalis, Hippidion, Tayassu pecari, Mazama gouazoubira, Mazama americana et à Palaeolama niedae. Cette association faunique permet de dater ce site du Pléistocène supérieur ou du tout début de l'Holocène. Par ailleurs, cette faune de la Toca da Pena présente beaucoup de similitude avec celle de la Toca do Barrigudo, qui se trouve à moins d'un kilomètre et d'où provient l'holotype de l'espèce : Scelidodon piauiense Guérin & Faure, 2004.
Impact of the Eocene-Oligocene transition on terrestrial ecosystems
2016
L’étude de l’impact des changements climatiques passés sur le domaine continental permet de comprendre les mécanismes, les vitesses et le calendrier des réponses des écosystèmes aux perturbations.La Transition Eocène-Oligocène (TEO) de la limite Eocène-Oligocène (EOb) se prête bien à ce type d’étude car elle enregistre la dernière transition climatique entre le mode greenhouse et le mode icehouse en passant par un intervalle mal compris : le doubthouse. Cette transition climatique a été étudiée sur un enregistrement lacustre riche en Matière Organique. Le modèle d’âge est construit par cyclostratigraphie,les évolutions de la végétation par des biomarqueurs moléculaires, et le climat local (température ethydrologie) par des proxies moléculaires et isotopiques. Les évolutions du climat mettent en évidence un refroidissement et une aridification marqués, en réponse au refroidissement EO. La végétation ne montre pas ce changement brutal, mais des changements rythmiques et marqués, en ph...
Quaternaire, 2014
Dans le cadre des travaux préalables au creusement du futur Canal Seine-Nord Europe (liaison Seine-Escaut), une opération de diagnostic archéologique de grande ampleur a été menée entre 2008 et 2011 dans le nord de la France. A Havrincourt (Pas-de-Calais), la découverte de plusieurs niveaux de silex paléolithiques inclus dans une séquence loessique relativement épaisse (~ 6-7m) préservée sur un versant en pente douce exposé nord-est a débouché sur une opération de fouille sur une surface totale de 6 000 m 2. Quatre niveaux paléolithiques en position primaire ont été mis au jour. Cette séquence a fait l'objet d'un travail de suivi stratigraphique en continu sur plus de neuf mois et d'une approche interdisciplinaire associant pédostratigraphie, sédimentologie, micromorphologie, paléontologie, malacologie, magnétisme environnemental, datations OSL et 14 C. Sur la base de ces recherches, nous proposons : 1) une nouvelle séquence pédostratigraphique de référence pour le nord de la France, notamment en ce qui concerne le début du Pléniglaciaire inférieur et le Pléniglaciaire moyen (~ 70-30 ka), 2) un nouveau canevas géochronologique régional pour le Dernier Glaciaire (datations par luminescence et radiocarbone) ainsi qu'une révision du schéma pédostratigraphique et chronoclimatique régional, et 3) la description et la datation d'une succession unique d'horizons périglaciaires comportant cinq réseaux de fentes associés à des gleys de toundra qui constitue une première séquence régionale de référence. Par ailleurs, la bonne conservation des niveaux archéologiques, associée à l'analyse pluridisciplinaire de la séquence pédosédimentaire et aux datations, débouche sur le calage chronostratigraphique et chrono-climatique précis des quatre niveaux paléolithiques fouillés incluant un ensemble exceptionnel attribuable au Paléolithique supérieur ancien (Gravettien ancien). Ces résultats et découvertes font d'Havrincourt une nouvelle séquence pédostratigraphique et archéologique de référence pour le Pléistocène supérieur de la France septentrionale et plus largement pour la zone loessique ouest-européenne.
This article presents the preliminary results on the geomorphological study conducted on the region of Klimonas-Ayios Tychonas. It aims to understand the palaeoenvironment and the palaeotopography when the site was settled as well as during its occupation. Also it aims to define any human impact on environmental changes. The importance of the site for the Cypriot Neolithic period, as the first village community on a Mediterranean island, makes necessary to understand the palaeoenvironment and the palaeolandscape of the region. This study is based on two different spatial scales: the localone by the study of the slope where the settlement installed on. The second is the regional scale which is based on the study of alluvial deposits in the vicinity of the site towards the south. The first study is based on a section on the road up to the site. It aims to understand the palaeotopography directly related to the site. The section is composed by a succession of colluvium deposits and paleosols. The colluvium accumulations alternate with three phases of pedogenesis. Radiocarbon dates on the first and on the last paleosols of the section give us the chronological frame of the formation of this slope. The first date is 19715–18 822 cal. BC and the second is 8224–7837 cal. BC which means that the slope where the village is installed was formed from the end of Pleniglacial period up to the beginning of the Holocene. Thus, the last paleosol corresponds to the paleosol where the site is installed on. At the time the slope was more regular than nowadays despite the fact that the colluvium deposits show an irregular profile which may be the result of tectonic activities at the end of Pleistocene as it is already observed during the excavation of the site. Concerning the regional palaeoenvironment, the study of alluvial terraces of the Athiaki stream, 400 m south of the site, reflects the river dynamic, the climatic conditions during its formation and the topography evolution through the millenniums. The section under study comes from the first alluvial terrace, which is the most ancient, and it is characterized by a succession of alluvial deposits alternating with six paleosols. The radiocarbon dates obtained from the first paleosol is 22166–21411 cal. BC and the one from the fifth paleosol is 7676–7517 cal. BC. These dates show that this terrace was formed between the end of the Pleniglacial period and the beginning of the Holocene. According to the data collected by the field study and the facies of the layers, the sub-humid conditions of Pleniglacial period became more arid and the river dynamic became less strong at the beginning of Holocene. At the time of the occupation of Klimonas, the climatic conditions were arid and the flow of the river was short. Regarding the paleotopography, 10,000 years ago, only the first terrace was formed thus, the river was situated almost 15m higher than nowadays and the topography was less important. The fine elements such as the silt and the clay and the water table close to the surface could offer suitable conditions for any agriculture activities. A comparison is made with data from Gialias River in Cyprus and speleothem study in Soreq cave in Israel, in order to obtain an overview of the palaeo-environment in eastern Mediterranean. The forthcoming sedimentological results will provide more accurate information on Athiaki stream.
Fluvial holocene palaeo-dynamics in the south-western upper Rhine graben (France)
2016
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