Structure of the Variscan belt beneath the British and Armorican overstep sequences

Abstract

Interpretation of gravity and magnetic data from southern England and of deep seismic data from the English Channel, Celtic Sea, and Paris basin provides a new picture of the buried Hercynian belt between France and England. The main structure corresponds to a mobile belt of crustal thickening that developed between the Midlands block, a northern block that had detached from the Armorican block prior to Hercynian time, and the Armorican block. The frontal collision between the two blocks recorded during the late Carboniferous was responsible for a pronounced narrowing of the belt between the Isle of Wight and Normandy. During collision, structural wedges were ejected in the channel and possibly also in the Hercynian basement beneath the Paris basin.