Crustal kinematics and deep structure of the northern Rhine Graben, Germany

Surface and subsurface geological data, unpublished information gleaned from industrial seismic surveys, and results from a deep reflection seismic profile across the Tertiary northern Rhine Graben indicate that crustal extension in excess of 6 km was achieved by asymmetric detachment of the upper crust at a depth of about 15 km. Comparison of a simple geometric‐kinematic cross‐sectional model and its depth extrapolation with the DEKORP‐9‐N deep crustal reflection data suggests that extension below the graben was achieved by slip along a gently westward dipping shear zone which truncated and offset lower crustal planar fabrics and which continues into the uppermost mantle. The planar lower crustal reflectors probably originated mainly during late Variscan (Permocarboniferous) crustal extension and/or magmatic underplating.