flysch

noun Geology.

1. an association of certain types of marine sedimentary rocks characteristic of deposition in a foredeep.

noun

1. (sometimes not capital) a marine sedimentary facies consisting of a sequence of sandstones, conglomerates, marls, shales, and clays that were formed by erosion during a period of mountain building and subsequently deformed as the mountain building continued. The phenomenon was first observed in the Alps