The French global geosciences transect between Brabant and the Basque provinces: A complete section of the Variscan orogen of western Europe

A new image of the French continental crust between Brabant (Belgium) and t he Basque province of Spain is presented on the basis of considerable recen t geological and geophysical information as well as the compilation and rei nterpretation of previously available data. The resulting section, which sh ows the main basement structures to a depth of 45 km, also is the first non speculative image of the westernmost part of the Variscan orogen. The Frenc h Global Geoscience Transect reveals a complete picture of this orogen betw een its remnant root and the surface. The divergent thrusts are bounded on the north and in the south by the old Brabant and Ebro-Aquitaine cratons, r espectively; these thrusts also involve two previous plate boundaries. The lower part of the orogen is limited by a layered lower crust, probably of P ermian age. Near the surface the Hercynian orogen is buried-near the northe rn end of the transect by the Paris Basin, which can be considered an eastw ard extension of the English Channel, and in the south by the South Armoric an continental margin, which makes a transition between the oceanic crust o f the Bay of Biscay and the axis of the Variscan orogen. In this area, the deep Parentis graben is located at the site of pronounced crustal thinning, since only 7 km of Hercynian crust are now preserved.