Layered flysch sediments. In a gully eroded by a mountain torrent, alternating rock strata have been exposed. Light sandstone layers alternate with darker grey mudstones. The sandstone layers were rapidly deposited by submarine turbidity currents descending from a continental slope, whereas the mudstones are the result of much slower sedimentation during quiescent phases. Such flysch sediments are easily eroded, as can be seen by the jumble of boulders in the riverbed.