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Reconstructing the Late Paleocene-Early Eocene continental paleosurface in and around the Paris and adjacent basins: new insights for paleogeographic, geodynamic and climatic studies

Abstract : Historically, the NW European basins, and more particularly those of the southern North Sea, are the cradle of stratigraphy, where the notion of "Sparnacian" took shape (Dollfus, 1880; Aubry et al., 2005). The Sparnacian facies, mainly continental to coastal, often record paleoweatherings. Towards the Mesozoic cover and old basements which surround the Paris basin, many fluvial sands and conglomerates units seal or incise thick kaolinitic weathering profiles and are themselves weathered, often oxidised, kaolinised and/or silicified. Among those paleoweathering types the silcretes are probably the most striking geological markers, found for a long time by geologists and geomorphologists who tried to map the "Eocene paleosurface". These silcretes are often ascribed to Late "Landenian" to the north of the Paris basin and correlated to the Sparnacian continental deposits to the south, west and east. In the best preserved successions (work in progress), those continental facies and weathering profiles lie above or are developed upon Upper Thanetian formations and are overlain by Lower Ypresian marine formations. And in few places, for example in Avesnois, they are the stratigraphic equivalents to fluvial sands which contain lignitic units where the PETM has been recorded (Quesnel et al, 2006). The processes involved in the genesis of these types of weathering are relatively well known in the Paris Basin and its borders (Thiry, 1981; Dupuis & Steurbaut, 1987; Thiry & Simon-Coinçon, 1996; Quesnel et al, 2007) and some appear to be closely linked to effects ascribable to a climate crisis like that of the PETM (marked alternations of flooding, inducing clay illuviation in the porosity and soil cracks, followed by dry phases saturating the ground solutions; acid drainage of highly organic and pyrite-rich sediments, destabilization of kaolinite, etc.; cf. Thiry, 1999). The work exposed here has consisted in 1) compiling, reviewing and validating all available evidence, 2) making new field observations in poorly investigated areas, backed up by augerhole drilling, 3) studying occurrences of paleoweatherings and continental deposits, dating using biostratigraphy, paleomagnetism, and ascribing them to the Lower Eocene paleosurface, 4) using all the data to digitally reconstruct the present geometry of this paleosurface at 1:1 000 000 scale, 5) reconstructing the continental paleogeography of the Paris basin and its surroundings during this interval, 6) discussing the geodynamic and climatic processes involved in the development of the paleoweatherings and associated paleosurface. Furthermore, this regional study may be directly usable in improving the tools for simulating the landscape evolution and the Earth's climate in paleoenvironmental modelling.
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Soumis le : mercredi 10 octobre 2012 - 17:18:04
Dernière modification le : mercredi 3 août 2022 - 04:02:20
Archivage à long terme le : : vendredi 11 janvier 2013 - 03:42:26


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Florence Quesnel, Christian Dupuis, Johan Yans, Caroline Ricordel-Prognon, Setareh Rad, et al.. Reconstructing the Late Paleocene-Early Eocene continental paleosurface in and around the Paris and adjacent basins: new insights for paleogeographic, geodynamic and climatic studies. GNS Miscellanous series, 2009, 18, pp.102-106. ⟨hal-00740721⟩



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