WHAT DOES THE MONTS-DE-LACAUNE FAULT (MON TAGNE-NOIRE, FRANCE) MEAN -IMPLICATIONS FOR THE ORIGIN OF THE NAPPES

The Monts de Lacaune fault (Montagne Noire, France) is a complex accid ent located between two contrasting structural domains: the autochthon ous metamorphic axial zone on one side and the Monts de Lacaune tecton ic slices on the other, of Palaeozoic age, thrust toward the SE. This accident is obviously a dextral wrench fault. However, considering the displacement along the wrench fault leads one to admit that this acci dent is moreover the basal thrust plane of a larger allochthonous comp lex including both the Monts de Lacaune domain and the terranes which now form the nappes of the Montagne Noire's southern slope. The result ing palaeogeographic reconstitution of the Cambrian deposits thus sugg ests an original solution to the long debated problem of the origin of those nappes.