A new structural interpretation of the Salvan-Dorénaz syncline (Aiguilles Rouges massif) is proposed; it proves that this syndine, filled with Permo-Carboniferous sediments, is mainly an alpine structure. The geologic evolution comprises the following stages :
a) Stephanian A - unknown date (Upper Stephanian, Autunian (?)): continental detrital sediments fill a NNE-SSW intramountainous trough in subsidence. Red layers define long alluvial fans imbricated in a dark sequence of sandstones and mudstones, with coals and lacustrine limestones.
b) Weak deformations occur during the «Saalic» tectonic phase (Permian). They correspond to the readjustment of relatively "plastic" sedimentary layers to brittle deformations that affect the underlying pre-Stephanian basement.
The progressive cessation of these movements during late Permian is followed by a "peneplanation" stage. The Permo-Carboniferous beds are eut by the transgressive Triassic deposits along a low-angle unconformity.
c) Alpine deformations start during Upper Eocene times; a first phase records the formation of the "parautochtonous slices" and the emplacement of the Morcles nappe (large recumbent fold). The separation of the "parautochtonous slices" is probably connected with early deformations of the basement-cover contact.
d) During a second phase, the pre-Triassic basement of the Aiguilles Rouges massif is affected by deformation (large-scale folding) and the more ductile Permo-Carboniferous sediments are strongly folded (formation of the Salvan-Dorénaz syncline).
For two reasons, (a) the continuation of the translation towards the NW of the Morcles nappe, (b) the disharmonie folds that appear in the Triassic rocks of the autochtonous cover, the folding of the Permo-Carboniferous only affects moderately the basal thrust of the Morcles nappe.
The metamorphic grade reaches the anchizone-epizone limit.