POSTOROGENIC ANISOTROPIC CREEPING OF THE LAYERED LOWER CRUST IN THE HERCYNIAN CHAIN (ENGLISH-CHANNEL)

The measurement of the length of seismic reflectors of the layered low er crust is, in some conditions, statistically significant. In the Eng lish Channel and Celtic Sea, we can show that the stretching of these reflectors depends on the azimuth of the seismic lines with respect to the orogenic axis. Because the maximum stretching is perpendicular to the root of the orogen, we consider, by comparison with surface data, that it is of Stephano-Permian age. The creep of the layered lower cr ust was probably anisotropic and associated with the gravity collapse of the Variscan orogen, now well understood at the surface.