Flysch

Flysch (/flɪʃ/) is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones.

Flysch typically consists of a sequence of shales rhythmically interbedded with thin, hard, graywacke-like sandstones.

On the upper plate, the land between the mountains and the undeformed continent bends downward, forming a foreland basin.

If the mountain slope is steep enough at the edge of the basin, it will shed material in rapidly moving sedimentary flows called turbidity currents, resulting in turbidite deposits.

Well-known flysch deposits are found in the forelands of the Pyrenees and Carpathians and in tectonically similar regions in Italy, the Balkans and on Cyprus.