The oldest Precambrian rocks of the northeastern Armorican Massif are represented by the migmatites and gneisses of La Hague which make up the Lower Proterozoic Pentevrian basement. This is overlain by the low-grade Upper Proterozoic rocks of the Brioverian succession which were affected by Cadomian deformation and plutonism. The Lower Brioverian Group consists of four tholeiitic volcanic formations overlain by terrigenous units which contain some black chert horizons. In the Coutances area this assemblage was affected by a local tectonometamorphic event which led to the formation of the Constantian arc (585 Ma). The uplift and erosion of this arc yielded the Upper Brioverian flysch which includes spilitic rocks at Vassy and sulphide deposits at Rouez. A plate tectonic model is proposed for the Cadomian orogeny in the northeastern Armorican Massif. Major and trace element geochemical features of the Brioverian igneous rocks allow us to assign it to a ‘Pacific’ tectonic setting. An island-arc system was established on Pentevrian crust remnants and led to magmatic arcs separated by marginal basins floored by MORB. Strain analysis shows that Cadomian thrusts and folds verge northwestwards, synthetic to southeasterly-directed subduction. A second southeastward-dipping subduction zone developed and was responsible for the closure of the back-arc basin and the generation of the Mancellian Batholith. The folded Upper Brioverian rocks were then intruded by these late-tectonic granodiorites at c. 540 Ma. The Brioverian rocks and Cadomian plutons were then uplifted, eroded and unconformably overlain by the Lower Cambrian cover. In the northeastern Armorican Massif, this Cadomian evolution corresponds to a major period of crustal growth and represents progressive cratonisation of the Brioverian basin and arc system.
L'article propose une mise au point sur le Mésolithique du Nord-Cotentin, extrémité nord de la Basse-Normandie et également du Massif armoricain. Les sites fouillés dans les années 80 et les prospections encore en cours ont permis de dégager des séries importantes, permettant de caractériser le débitage et l'outillage et son évolution durant le Mésolithique moyen. Des comparaisons avec les régions environnantes, particulièrement le Sud de l'Angleterre et le bassin de la Somme, ont ainsi pu être esquissées. Un riche outillage sur galet a également pu être mis en évidence. La présence sur le site d'Auderville du lieu d'extraction de ces galets et d'outils sur galet biseautés a permis de proposer l'hypothèse d'une exploitation à flanc de falaise de galets et de plaquettes de grès.
In 1966, the marine erosion of Quaternary deposits on the North Cotentin coast revealed a small Neolithic valley settlement. Excavation between 1967-1969 of a few square metres revealed a pit and a fossil soil layer rich in material. Re-examination of the hitherto unpublished small finds within the assemblage established the presence of a vase support decorated in Er Lannic style, associated with transverse arrowheads and a backed knife, as well as sherds with repoussé buttons and shallow groove decorations recalling the Breton Castellic tradition and some Channel Islands material (e.g. Grosnez Hougue, Jersey). This site could be attributed to the beginning of Middle Neolithic II, contemporary with the first megalithic monuments of Western France.
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