marine molasses

The ground at Beaucastel is marked by the violence wrought by the Rhone river. It consists of a layer of marine molasses (sandstone) of the Miocene period, covered by alpine alluvium. The presence in this topsoil of a great number of rounded stones, known as "galets", bears evidence of the time when the Rhone, then a torrent, tore fragments of rock from the Alps and deposited them along its course.