The upper Rhenish Shield basement (Vosges, Upper Rhinegraben and Schwarzwald): Main structural features deduced from magnetic, gravimetric and geological data

Abstract

Interpretation of magnetic and gravimetric data and correlations with geological observations on outcrops and in boreholes have enabled the construction of a geological sketch map of the pre-Westphalian basement in the area of the upper Rhenish shield. The map demonstrates the contrast between the “heavy” and “magnetic” Saxothuringian, characterized by Palaeozoic units metamorphosed to varying degrees and intruded by Early Carboniferous basites, and the “lighter” Moldanubian, consisting mainly of gneisses and granites. Geological structures and tectonic features are recorded beneath the Mesozoic and Cenozoic cover. The present picture of the basement is mainly the result of late Visean-early Namurian structural features represented by a linear arrangement of magmatic bodies and the distribution of strike-slip and thrust faults. The major structural features are the E-W Vittel-Lalaye-Lubine- Baden-Baden fault that marks the border between Saxothuringian and Moldanubian, the N35° left-lateral wrench-fault system running along the present Rhinegraben, the N60° grain of the northern Vosges and the Saar basin, and the S-verging crustal thrusts of Moldanubian.