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Late Cretaceous to early Paleogene deformations in the western part of the Eurasian plate

Abstract : The Late Cretaceous to early Palaeogene is a period of major deformations of the western part of the Eurasian plate within both the context of the Africa-Eurasia convergence and the North Atlantic opening. Two mechanisms are proposed: (1) surface upwelling caused by flows in the underlying mantle (Iceland Plume upwelling) and/or (2) horizontal lithospheric deformations (Africa, Iberia, Eurasia convergence). Here we discuss the timing, spatial distribution, types and magnitude of these deformations. Two approaches are used: (1) Geomorphology - on the mapping and chronology of all the macroforms (planation surfaces, incised rivers) dated by intersection with the preserved sediments, weathering and volcanics; (2) Basin stratigraphy and structural analysis - on a more classical dataset of seismic lines, wells and field observations, coupled with biostratigraphic re-evaluations. We provide an european-scale cross section that has been restored from the early Turonian to the Oligocene, through the North Pyrenean Zone, Eastern Aquitaine Basin, French Massif Central and Paris-Brussels Basins. We combine two methods to quantify the magnitude of the deformations: (1) depositional domain - 2D accommodation space measurements; (2) erosional domain - difference between the present-day elevation of ancient sea-level markers (marine sediments scattered upon it) and a global sea-level curve. The first outcomes of our study are: - The Late Cretaceous is a period of enhanced subsidence. All the studied area is covered by marine chalk deposits. - A major period of deformation occurs at the Cretaceous-Tertiary boundary possibly sub- divided into two sub-periods: intra-Maastrichtian - pre-middle-Danian and Upper Danian - pre-Thanetian. - Long wavelength (x 100 km) and moderate amplitude uplift (x 100 m) coupled with intense erosion affects the northern border of the French Massif Central and the Paris and Brussels Basins. A major change in the sedimentary system occurs from open marine chalks to siliciclastic shore deposits. To the south, extremely low accommodation rates are recorded in the retro-wedge of the eastern Aquitaine Basin with no evidences of uplift. The Eocene to Chattian corresponds to a period of enhanced subsidence in the eastern Aquitaine Basin whereas the Paris Basin has become Nous avons donc entrepris une analyse géochronologique sur les potentiels niveaux de tonsteins d’un forage carotté de Lucenay-lès-Aix (forage LY-F). Au préalable, des analyses minéralogiques (par diffraction des rayons X) et géochimiques (par ICP-AES et ICP-MS) ont été réalisées afin de confirmer l’origine volcanique de ces niveaux et d’identifier une possible contamination. Cinq échantillons ont été sélectionnés pour des analyses U/Pb (LA-ICP-MS) sur zircons. Les deux premiers échantillons, à la base du forage, permettent de calculer un âge Concordia à c. 299 Ma tandis que pour les trois autres échantillons, plus haut dans la série, la dispersion des analyses le long de la Concordia rend difficile la détermination d’un âge. Cette dispersion des données traduit à la fois une perte en Pb subie par certains grains, et la présence de grains hérités et/ou remaniés. Des analyses U/Pb (LA-ICP-MS) sur apatites ont également été réalisées sur ces trois échantillons. Les âges intercept calculés pour chacun des échantillons sont, compte tenu des erreurs calculées, identiques aux âges U/Pb sur zircons obtenus sur les échantillons de la base du forage. Des analyses en cours sur les séries contemporaines du Massif Central vont permettre d’obtenir d’autres âges, cette étude permettant d’ores-et-déjà de proposer de nouvelles stratégies pour améliorer la précision des résultats.
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Submitted on : Thursday, November 8, 2018 - 9:26:35 AM
Last modification on : Saturday, November 20, 2021 - 3:00:24 AM


  • HAL Id : insu-01915827, version 1


Guillaume Baby, François Guillocheau, Justine Briais, Eric Lasseur, Paul Bessin, et al.. Late Cretaceous to early Paleogene deformations in the western part of the Eurasian plate. 26ème Réunion des Sciences de la terre - RST, Oct 2018, Lille, France. pp.36. ⟨insu-01915827⟩



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