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La Zone du flysch dans les nappes de l'Embrunais-Ubaye (Alpes occidentales)

Abstract : The Embrunais-Ubaye-country is located in the Western Alps, between the Pelvoux and Argentera crystalline massives ; it can be divided as follows : I. — THE AUTOCHTONOUS BASEMENT consists of the sedimentary cover (Trias to upper Priabonian) of ante Westphalian crystalline rocks and belongs to the Eastern margin of the Southern subalpine zone, where paleotectonic features exhibit East West trends. The last stratigraphie member is not the Annot sandstone formation but a blocky mudstone member (Schistes à blocs) considered as olisthostromes which can be found at the same level at the top of the Subbriançonnais and Briançonnais eocene séries. Thèse olisthostromes are big slumps related to an early submarine sliding nappe which invaded the Western penninic priabonian basin (Autapie nappe). Before the arrivai of the Oligocène epiglyptic nappes, this basement was acted upon by three tectonic phases : — an Eo-senonian phase which can be seen in the Nor thern part of the région, where Senonian limestones lie direedy on Oxfordian black shales (Dévoluy or Gosau phase) ; — an Eocene (pre-lutetian) phase, marked by a slight unconformity of the « Priabonian Trilogy » in the South of the région, whereas strong-looking movements appear in the North where the Priabonian rests upon the Pelvoux Crystalline rocks ; however, thèse move ments may take again the Eo-senonian structures ; — a Sannoisian (lattorfian) phase, resulting in a gênerai uplift of the central part of the Embrunais-Ubaye, where a « Barcelonnette Dôme » appears ; subsequendy destroyed by the érosion, this dôme then becomes a dépression dug into Jurassic black shales ; it may be thought that epiglyptic nappes stopped against reliefs built by -the belt of Cretaceous and Nummulitic beds surrounding the blach shales outerops. When nappes overthrust the area, some parautochtonous slices occured, but there is no continuous parautochtonous « Ultra-dauphinois » zone in front of the Embrunais-Ubaye nappes. II. — THE NAPPES are made up of units coming from nearby or from distant realms such as outer Penninic and inner Penninic ones close to Austroalpine realms. They may be conveniently divided into two principal groups : - a lower one, in an ou ter position, formed by Subbriançonnais units with their pseudo cover of a first kind of Helminthoide Flysch, the Autapie Nappe ; - an Upper one, constituted by a second kind of Helmin thoide Flysch, the Parpaillon Nappe, overlying a number of basal slices.
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Contributor : Pascale Talour <>
Submitted on : Thursday, January 21, 2010 - 2:45:28 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Thursday, June 17, 2010 - 9:10:06 PM

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  • HAL Id : tel-00449388, version 1

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Claude Kerckhove. La Zone du flysch dans les nappes de l'Embrunais-Ubaye (Alpes occidentales). Géologie appliquée. Université Joseph-Fourier - Grenoble I, 1970. Français. ⟨tel-00449388⟩

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