Sandstone and shale sediments. This exposed cliff shows sediments arranged in an anticline (convex) fold. The layers are alternating sandstone and shale deposits, spanning the Cretaceous period (from 145 to 65 million years ago), at right, and Palaeocene period (from 65 to 56 million years ago), at left. These sediments are known as Flysch sediments, meaning they were deposited simultaneously with the throwing up of mountain ranges at collisional tectonic plate boundaries. The material in the sediment is from pre-existing rocks, often originating from the new mountains. Photographed at Zumaia, Spain.