Orcadian Basin

The Orcadian Basin is a sedimentary basin of Devonian age that formed mainly as a result of extensional tectonics in northeastern Scotland after the end of the Caledonian orogeny. During part of its history, the basin was filled by a lake now known as Lake Orcadie. In that lacustrine environment, a sequence of finely bedded sedimentary rocks was deposited, containing well-preserved fish fossils, with alternating layers of mudstone and coarse siltstone to very fine sandstone.[1] These flagstones split easily along the bedding and have been used as building material for thousands of years.[2] The deposits of the Orcadian Basin form part of the Old Red Sandstone (ORS). The lithostratigraphic terms lower, middle and upper ORS, however, do not necessarily match exactly with sediments of lower, middle and upper Devonian age, as the base of the ORS is now known to be in the Silurian and the top in the Carboniferous.[3]

  1. ^ Rogers, D.A.; Astin, T.R. (1991). "Ephemeral lakes, mud pellet dunes and wind-blown sand and silt: reinterpretation of Devonian lacustrine cycles in north Scotland". In Anadón A.; Cabrera L.; Kelts K.R. (eds.). Lacustrine facies analysis. Special publications of the International Association of Sedimentologists. Vol. 13. John Wiley & Sons. pp. 199–221. ISBN 978-0-632-03149-8.
  2. ^ Oliver, Neil (2011). A History of Ancient Britain. Hachette UK. ISBN 978-0-297-86768-5. Retrieved 27 February 2012.
  3. ^ Barclay, W.J. (2005). "1: Introduction to the Old Red Sandstone of Great Britain" (PDF). In Barclay, W.J.; Browne, M.A.E.; McMillan, A.A.; Pickett, E.A.; Stone, P.; Wilby, P.R. (eds.). The Old Red Sandstone of Great Britain. Geological Conservation Review Series. Vol. 31. Joint Nature Conservation Committee. ISBN 978-1-86107-543-7. Retrieved 26 February 2012.