The Eday Group is a

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

lithostratigraphic Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneous ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

(a sequence of

rock strata In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ...

) in

Orkney Orkney (), also known as the Orkney Islands, is an archipelago off the north coast of mainland Scotland. The plural name the Orkneys is also sometimes used, but locals now consider it outdated. Part of the Northern Isles along with Shetland, ...

, northern

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

. The name is derived from the island of

Eday Eday (, ) is one of the islands of Orkney, which are located to the north of the Scottish mainland. One of the North Isles, Eday is about from the Orkney Mainland. With an area of , it is the ninth-largest island of the archipelago. The bedroc ...

where the

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

are exposed in coastal cliffs.

Outcrops

These rocks are exposed throughout Orkney, notably in coastal cliffs of Eday and western Sanday,

South Ronaldsay South Ronaldsay (, also , ) is one of the Orkney Islands off the north coast of Scotland. It is linked to the Orkney Mainland by the Churchill Barriers, running via Burray, Glimps Holm and Lamb Holm. Name Along with North Ronaldsay, the islan ...

and the Deerness peninsula of

Mainland Mainland is defined as "relating to or forming the main part of a country or continent, not including the islands around it egardless of status under territorial jurisdiction by an entity" The term is often politically, economically and/or demogr ...

. There are spectacular exposures of the Hoy Sandstone Formation and particularly the Trowie Glen Sandstone Member in the precipitous cliffs of Hoy's west coast.

Lithology and stratigraphy

The Group comprises the Upper Eday Sandstone Formation, Eday Marl Formation, Middle Eday Sandstone Formation, Eday Flagstone Formation, Lower Eday Sandstone Formation and the Hoy Sandstone Formation laid down in the shallow Orcadian Basin during the

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...

stage of the Devonian period. The sediments vary from fluvial to lacustrine to lagoonal. On the island of

Hoy Hoy may refer to: People Given name * Hoy Menear (died 2023), American politician * Hoy Phallin (born 1995), Cambodian footballer * Hoy Wong (1920–2009), American bartender Surname * Hoy (surname), a Scottish and Irish surname * H� ...

, the Hoy Sandstone is a particularly thick formation at whose base is the Hoy Volcanic member.British Geological Survey 1:100,000 scale geological map (Scotland) ''Orkney Islands'' (special sheet)

References

{{Reflist Geological groups of the United Kingdom Geologic formations of Scotland Devonian System of Europe Devonian Scotland Givetian Stage

Outcrops

Lithology and stratigraphy

See also

References