Many hectometric half-grabens of the margin of the alpine ocean are visible near the Lac Besson.
Under the foot of Mireille, the escarpment of the normal fault consists of hercynian gneisses. The half graben is filled with red triassic dolomites which rest unconformably on the Hercynian basement on the right side of the photography (to the East). PhotoID296
Many hectometric half-grabens of the margin of the alpine ocean are visible near the Lac Besson.
Under the foot of Mireille, the escarpment of the normal fault consists of hercynian gneisses. The half graben is filled with red triassic dolomites which rest unconformably on the Hercynian basement on the right side of the photography (to the East). PhotoID296
Photograph: ch.nicollet
Reference: http://christian.nicollet.free.fr/page/Alpes/ornon/besson.html