The South Stack Formation is a sequence of Cambro-

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

(

Furongian The Furongian is the fourth and final epoch and series of the Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding ...

Tremadocian The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from to million years ago. The base of the Tremadocian is defined as the First appearance datum ...

)

metasediment In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment Sediment is a solid material that is transported to a new location where it is deposited. It occu ...

ary rocks exposed in northwestern

Anglesey Anglesey ( ; ) is an island off the north-west coast of Wales. It forms the bulk of the Principal areas of Wales, county known as the Isle of Anglesey, which also includes Holy Island, Anglesey, Holy Island () and some islets and Skerry, sker ...

North Wales North Wales ( ) is a Regions of Wales, region of Wales, encompassing its northernmost areas. It borders mid Wales to the south, England to the east, and the Irish Sea to the north and west. The area is highly mountainous and rural, with Snowdon ...

. The outcrop of this formation at

South Stack South Stack () is an island situated just off Holy Island on the northwest coast of Anglesey, Wales. Geology South Stack is an island known as a sea stack. It was formed by the wave erosion of sedimentary rocks that once connected the isla ...

was chosen as one of the top 100 geosites in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

by the

Geological Society of London The Geological Society of London, known commonly as the Geological Society, is a learned society based in the United Kingdom. It is the oldest national geological society in the world and the largest in Europe, with more than 12,000 Fellows. Fe ...

, for its display of small-scale

folding Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure * Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Abov ...

References

{{Reflist

* Phillips, E, 1991. Progressive deformation of the South Stack and New Harbour Groups, Holy Island, Western Anglesey, North Wales. Quarterly Journal of the Geological Society, Vol.148, p. 1091-1100 * Shackleton, R M, 1954. The structure and succession of Anglesey and the Lleyn Peninsula. British Association for the Advancement of Science, Vol.11, p. 106-108 * Greenly, E. 1919. Geology of Anglesey. Memoir of the Geological Survey, UK * Blake, J F, 1888. The Monian System of rocks. Quarterly Journal of the Geological Society, Vol.44, p. 476-480 Geologic formations of Wales Cambrian System of Europe Ordovician System of Europe Cambrian Wales Ordovician Wales Furongian Tremadocian Sandstone formations Mudstone formations of the United Kingdom Geology of Anglesey

References

Further reading