sentences:  Triassic sandstones are also found along the border with Cheshire and Shropshire, though most often concealed beneath recent fluvial and glacially derived material.Rocks dating from the Jurassic period occur widely across the Vale of Glamorgan.Much of the Glamorgan coast between Ogmore-by-Sea and Barry is formed by cliffs of layered Jurassic limestone known as the Lias.