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Paléogène marin et structuration des Alpes Occidentales françaises (domaine externe et confins sud-occidentaux du subbriançonnais).

Abstract : The external alpine marine Paleogene and some flysch of the Embrunais-Ubaye nappes are studied in the French Alps between the Swiss border and the Provençal realm. New data, from nanno and micropaleontology and from palynology are proposed. The benthos is used to define ecological levels. Deformations analysis permit to find the dynamic evolution of the basin, with important synsedimentary tecctonic feature (with reactivated faults). The emplacement of allochtonous units on the eastern part of the european plate and the westward motion of these ones in the marine basin caused : - 1, ahead of their front in the foreland, the appearance of a moat the subsidence of wich was responsible for the nummullitic transgression ; - 2, against their front, the appearance of an accretional prism wich developped in deep waters ; - 3, in the european plate flexure extrados, the appearance of the calco-alkaline paleogene volcanism (which was limited and located close by main faults, and more and more recent towards the external part of the orogen). During the late Priabonian, in the external alpine area the nummulitic basin was made up with a shelf, a slope and a deep basin. The shelf was bordered in the west by a main faulted zone that, in the Southern Alps, represented the more western shore-line of the paleogene sea (Front nummulitique) and in the east by a flexure and/or an another faulted zone. On the shelf, nummulities limestones then circa-littoral marls were deposited ; on the slope, marls wich bathyal microfauns, and in the basin, deep sea fans take place. The early Oligocene alpine contraction caused a structural inversion at the eastern boundary of the Priabonian shelf. Thus this area became a subsident most (Sillon préalpin) first in marine then continental environment. This trap received reworked sediments from the Priabonian slope and basin and from the internal alpine nappes ; on its eastern part a continental accretion prism developped in the Southern Alps. In this region, the westward most motion was locked during the Upper Ologocene. Howewer this motion continued in the northern part of the range : in the Upper Chattian, the most reached the eastern Jura an its subsidence will cause the Miocene transgression in this perialpine area. To sum up, the alpine Palogene basin was induced by the movements of reactiveted inherited faults. Its boundaries were superimposed on crustal borders : in the Southern Alps this basin was directly superimposed on the Bloc crustal de la Durance. These tectonic boundaries of the Paleogene basin will be still again reactivated during the Moi-Pliocene alpine movements to individualize new structural units (e.g. the Poinçon-d'Aspres-Rouaine in the Southern Alps).
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https://tel.archives-ouvertes.fr/tel-00503118
Contributor : Pascale Talour <>
Submitted on : Friday, July 16, 2010 - 3:58:50 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM

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Jean Louis Pairis. Paléogène marin et structuration des Alpes Occidentales françaises (domaine externe et confins sud-occidentaux du subbriançonnais).. Minéralogie. Université Joseph-Fourier - Grenoble I, 1988. Français. ⟨tel-00503118⟩

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