Most of the younger rocks have been eroded away, taking with them clues to the events that formed them – most of 300 million years of rock history is now missing (12) but isolated exposures of Permian rocks outcrop in the far west (where a small outcrop of Permo-Triassic desert sandstones (Appleby Group) occurs south-west of Ingleton), and in the east limestones of the Cadeby Formation (Zechstein Group) are present. The Zechstein Group deposits are late Permian in age, from about 252 to 251 million years old, and represent deposits formed at the margin of an enclosed marine sea that periodically became hypersaline and evaporitic.