A study of the structural surface of the Pelvoux crystalline complex in the Morges synclinorium, southeast of Chapelle-en-Valgaudemar, in the Briancon region, France. This surface resembles that of a cumulus cloud in shape. It is concluded that during the Alpine orogeny the crystalline complex was deformed, on a large scale, as a semirigid, semiplastic mass, with faulting only on a small scale. The sedimentary cover, on the other hand, was subjected to strong tangential displacements, resulting in the piling up of thrust slices. The mechanism of formation of closed synclines, enlarging downwards and often enclosing pockets of sedimentary rocks entirely within the crystalline rocks, is not yet clear.