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Caractérisation et évolution des flux détritiques et authigènes en contexte lacustre carbonaté au cours du Tardiglaciaire et de l'Holocène (Lac Saint-Point, Haute-Chaîne du Jura) : implications paléoclimatiques et paléoenvironnementales

Abstract : Located in the high chain of the Jura Mountains, Lake Saint-Point appears to be one of the most significant natural lake systems in France. A coring campaign was carried out in 2005 and resulted in the extraction of a 12.5 m long continuous sequence in its deep zone. Based on various dating methods (ie radiocarbon dating, tephrochronology...), this sequence's chronology spans over the Late Glacial and actual periods. A multi-parameter approach to this sequence consists in characterizing its inorganic (mineralogy, major element geochemistry, granulometry, ostracods assemblage) as well as organic fractions (rates of organic carbon, pollen). The comparison of different markers in different parts of the system (soils, vegetation, water column) highlights different evolution periods influenced by climate and human impacts. The sequence is thus composed of two distinct sedimentary sections, one being associated to the Late Glacial (from 18,500 to 11,300 cal BP) and the other to the Holocene (from 11,300 to the actual period). This bipartition is the consequence of a dramatic early Holocene authigenic production increase and a pedogenetic evolution combined with the development of forests (mixed oak) in the catchment basin. This evolution corresponds to the Holocene Climatic Optimum. Another transition occurs in 6,300 BP with the shift from Holocene Climatic Optimum to Neoglaciation due to the influence of the orbital impact. Vegetation then evolves to an Abies-Picea forest, resulting in soil and soil erodibility modifications. Even though some anthropization related pollen data have been detected from 7,200 cal BP, human impact on sedimentary response can only be observed from 2,600 cal BP on. It takes two different forms. From 2,600 cal BP to 1,200 cal BP, agricultural activities (cereals) prompt an increase in global detritism. From 1,200 cal BP, a decrease in silicate inputs, concurrent with increased anthropization related pollen data, can be seen as the consequence of a shift in agricultural practices from cereal growing to dominant pastoralism.
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Contributor : Aurélie Leroux <>
Submitted on : Friday, October 7, 2011 - 1:27:44 PM
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Aurélie Leroux. Caractérisation et évolution des flux détritiques et authigènes en contexte lacustre carbonaté au cours du Tardiglaciaire et de l'Holocène (Lac Saint-Point, Haute-Chaîne du Jura) : implications paléoclimatiques et paléoenvironnementales. Planète et Univers [physics]. Université de Franche-Comté, 2010. Français. ⟨tel-00630131⟩

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