sentences:  Marble sequences corresponding to the Falacron Marbles intercalated by schists and gneisses, are up to 500m thick and are separated from the underlying gneisses by a transition zone about 300 m thick termed the T-zone consisting of alternances of dolomitic and calcitic marbles intercalated by schists and gneisses.The rocks have undergone several periods of regional metamorphism, to at least upper amphibolite facies, and there was a subsequent phase of retrograde metamorphism.At least three periods of regional deformation have been identified, the most important being large scale isoclinal folding with axes aligned north-west.