Seismic reprocessing of BELCORP-DEKORP 1A reveals deep fault reflections of the Paleozoic Eifel Fold and Thrust Belt in Germany

Abstract

The Paleozoic Eifel Fold and Thrust Belt is part of the northern Variscan Deformation Front. Due to erosion, parts of its uppermost layers have been removed, enabling direct seismic reflection imaging of its internal deformation pattern in the upper crust utilizing seismic reflection imaging techniques. Reprocessing of the BELCORP-DEKORP seismic reflection line 1A from 1987 reveals previously undocumented structural details when applying state-of-the-art tools such as an improved seismic velocity background model and Fresnel volume migration. Additionally, a detailed analysis of seismic polarities helps to characterize the impedance contrasts of the reflectors at depth. A marked reflector of approximately 80 km length is identified, originating in the Belgian Ardennes Mountains and terminating in the southeast in the Hocheifel Volcanic Field at a depth of c. 12 km. The reflector dips in average with about 8° towards the southeast and has a thickness of approximately 400 m. In many parts, this reflector is characterized by a negative impedance contrast, which can be interpreted as a fault gouge or breccia composed of crushed rock, possibly containing fluids. This large feature is interpreted as the basal detachment zone of a wedge-like structure. A restoration model of this wedge results in shortening of about 22 km. In addition to the main detachment reflector, numerous tectonic features like subsidiary fault strands, synclines, ramps and backthrusts have been imaged. Strong reflectors in the Hocheifel Volcanic Field are interpreted as solidified sills related to the Cenozoic magmatism.