During the Variscan orogeny the original sedimentary succession of the Génis Unit subsided and was metamorphosed due to increasing overburden. The metamorphism followed a retrograde path (neoformation of chlorite) and recorded the epizonal conditions of the greenschist facies. This fact is very important for the geology of the Massif Central, because low-grade metamorphic successions are underrepresented and quite rare. Usually the metasediments in the Massif Central are strongly deformed and metamorphosed (under amphibolite facies conditions) and therefore only rough guesses can be made about their protoliths.
