Le socle vosgien / The vosgian basement

Abstract

The Vosges basement — This synthesis about the Vosges basement is based on the assessment of the geological results of the two last decades. The geologic units, their structures and their geodynamic evolution are described, first for the northern Vosges (Saxo-Thuringian Vosges), then for the middle and southern Vosges (Moldanubian Vosges). The history of these two areas which display a contrasted evolution during the Lower Palaeozoic can be studied as part of the geodynamics of the Variscan Central Europe. The metamorphism of the pre-Devonian basement shows a progressive retrograde evolution after an eclogitic episode at the base of the Palaeozoic. The magmatism is contemporaneous with the paroxysmal structuration of the variscan belt and displays a jerky evolution which leads to products resulting from an important crustal contamination. The Devono-Dinantian volcano-sedimentary cover gives evidence of marine sedimentary basins which evolve to emersion. Afterwards, this cover is affected by thrust tectonics which produces migmatization at the bottom of the crystalline nappes. The important Visean shortening generates the nappe structuration with vergences on both sides of the Lalaye-Lubine dislocation. At last, comparisons with other massives of the Variscan belt are outlined.