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Datations par paléomagnétisme des paléoaltérations du Massif Central et de ses bordures : implications géodynamiques

Abstract : Dating continental unconformities are essential to constrain geodynamical models. Paleomagnetism is a great tool to date ferrugineous paleoweathering. Datings of red "siderolithic" formations from the Massif central provide ages ranging from 160 Ma (Late Jurassic) in the Naussac Basin to 140 Ma (Early Cretaceous) in the Lembron region. On the southeast border of the Paris Basin, a hematitic layer located at the base of the Myennes Clays gave a recent age (0-3 Ma) which could be related to groundwater flow during the formation of the present-day landscapes. On the Massif Central and the Morvan crystalline basements albitized facies have been dated by paleomagnetism to be Triassic in age. Both datings and geographic distribution of the albitized formations argue for a superficial origin of these facies. The space and time distribution of the formations and the related unconformities gives elements to highlight the geodynamic evolution of the Massif Central. Triassic, Late Jurassic and Tertiary unconformities are superimposed on large areas. It implies very little erosion of the crystalline basement since Triassic times, as shown by the widespread albitized triassic unconformity outcroping at present. Datings points out that no Mesozoic cover was present on the basement during development of the red kaolinitic paleosoils during the Late Jurassic/Early Cretaceous period. Consequently, the Massif Central did probably not support an important (more than 500 m) sedimentary cover during the Mesozoic. Identification and dating of continental unconformities give evidences for long lasting continental evolution and landscape stability of the Massif Central all along the Mesozoic.
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https://pastel.archives-ouvertes.fr/pastel-00003382
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Submitted on : Thursday, February 7, 2008 - 8:00:00 AM
Last modification on : Friday, October 23, 2020 - 4:48:07 PM
Long-term archiving on: : Thursday, September 30, 2010 - 8:11:15 PM

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  • HAL Id : pastel-00003382, version 1

Citation

Caroline Ricordel. Datations par paléomagnétisme des paléoaltérations du Massif Central et de ses bordures : implications géodynamiques. Planète et Univers [physics]. École Nationale Supérieure des Mines de Paris, 2007. Français. ⟨NNT : 2007ENMP1479⟩. ⟨pastel-00003382⟩

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