Orcadian Basin

Last updated

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]

Contents

Extent

The exact extent of the Orcadian Basin is uncertain due to later tectonic effects and burial beneath younger sediments, but it is known to have reached from the south coast of the Moray Firth to the Shetland Islands in the north and from Strathy on the Caithness coast in the west, to the Outer Moray Firth and East Shetland Platform in the east, where it is proven by hydrocarbon exploration wells. [4] Continental sediments of the same age are also known from the Clair oilfield west of the Shetland Islands and have been tentatively identified in the West Orkney Basin. The connection of the Orcadian Basin to the Devonian basins of western Norway and eastern Greenland is not known in any detail. To the south the basin may continue almost as far south as the Highland Boundary Fault, including the half-grabens at Turriff and Rhynie. [5]

Tectonic setting

Extent of the Orcadian Basin from outcrop and offshore hydrocarbon exploration wells Orcadian Basin extent.png
Extent of the Orcadian Basin from outcrop and offshore hydrocarbon exploration wells
The Sandwick Fish Bed near Stromness, deposited in the deepest, most widespread and longest-lasting lake in the basin Sandwick Fish Bed.jpg
The Sandwick Fish Bed near Stromness, deposited in the deepest, most widespread and longest-lasting lake in the basin
Thick fluvial sandstones of Givetian age exposed in the cliffs on the western coast of Hoy Cliffs NW of St John's Head - geograph.org.uk - 90781.jpg
Thick fluvial sandstones of Givetian age exposed in the cliffs on the western coast of Hoy
Tuff layer within Eday Sandstone near Houton Head, Mainland, Orkney Base of tuff layer in Lower Eday Sst.jpg
Tuff layer within Eday Sandstone near Houton Head, Mainland, Orkney

In common with the Devonian basins of Norway and East Greenland, the Orcadian Basin lies entirely within the area affected by crustal thickening during the Caledonian orogeny. The recognition of extensional faulting at various scales in these areas at the same time as deposition led to the suggestion that these basins reflect the gravitational collapse of this thickened zone. [6] Other tectonic models have suggested that transtensional sinistral (left lateral) strike-slip movement on the Great Glen Fault, which passes through the centre of the basin, was the main cause of basin formation. [7] The continuity of Middle Devonian facies belts across the trace of the fault zone, after accounting for subsequent reactivation of the Great Glen Fault in a dextral sense, has been used to argue against strike-slip activity during sedimentation. [8] However, the uplift of a block containing late granitic veins within the basement Moine complex in Easter Ross, whose intrusion has been dated as earliest Eifelian, before deposition of the overlying Middle Devonian sediments, is evidence of some continuing activity along this structure into the middle Devonian period. [9]

Development

Early Devonian

Evidence from onshore in Easter Ross and offshore in the Inner Moray Firth shows that a series of isolated half-grabens were formed at this time filled with a mixture of coarse, often conglomeratic sediments, combined with organic-rich lacustrine shales, such as those exposed at Strathpeffer. [10] [11] [12]

Middle Devonian

Sedimentation during the middle Devonian covered the full extent of the Orcadian Basin with only local exposed basement highs, such as near Stromness in Orkney. The early part of this period, approximately equivalent to the whole of the Eifelian and early Givetian, saw the development of a large lake, that covered most of the basin at times. Regular variations in its depth and extent, which have been linked to Milankovitch cycles, led to pronounced cyclicity in the sequence. At the deep permanent lake stage in a typical cycle there is normally a laminite, consisting of fine-scale alternations of clastic, carbonate and organic laminae, thought to represent annual varves. As the lake shallows and becomes ephemeral the sequence consists of alternations of silts and fine sandstones often with mudcracks, showing the repeated periods of drying out. The lake development culminated in a single very deep and particularly thick and extensive lake interval, the Achanarras Fish Bed Member. The lake at this time covered an area of at least 50,000 km2 [13] with a maximum estimated depth of at least 100 metres. [14] From the fossil fish fauna preserved at one level in this unit, it is known to have been particularly diverse and widespread in its occurrence. [14] This interval is also known as the Sandwick Fish Bed Member in Orkney and a series of other equivalent fish beds in Shetland and on the south side of the Moray Firth. A thick lake interval of similar age is also found in East Greenland. This deep lake interval is dated as late Eifelian and is correlated to the global Kačák Event of marine anoxia, which was associated with significant extinctions. The increase in lake size is explained as the result of an intensification of the monsoon system. [14] This unit splits the flagstone sequence into two parts known regionally as the Lower and Upper Orcadian Flagstone formations. [15]

In mid-Givetian times, the dominant lake environment gave way to mainly fluvial conditions, with the main sediment type changing from flagstones to sandstones. In parts of the basin, the sequence consists almost entirely of sandstones, mainly fluvial in origin, such as the Dunnet Head and Hoy Sandstones. Elsewhere, such as in Orkney in the Eday Group, the sequence shows more variety with major intercalations of marls and flagstones, marking the local return of lacustrine conditions. There is local evidence of marine conditions affecting the basin during one of these periods as shown by the presence of scolecodonts (marine microfossils) in the Eday Marl Formation. This and other later marine incursions have been correlated with global sea level highstands previously recognised from the middle to upper Devonian sequences of New York State, including the Taghanic, Genundewa, Middlesex and Rhinestreet events. [16]

On the Orkney Islands, volcanic rocks are found within the lower part of the Eday Group. These form isolated exposures of varying chemistry, indicating a change in magma source from one with a strong influence from earlier subduction to the alkali basalts more normally associated with extensional tectonics. [17] The Devonian of West Mainland in the Shetland Islands contains more volcanic rocks and the upper middle Devonian sequence there is intruded by the Late Devonian Sandsting Granite.

Late Devonian to Early Carboniferous

The later history of the Orcadian Basin is only known from offshore well data, as the youngest exposed Devonian known is Late Givetian in age. Well data shows that the depositional style remained similar throughout the Late Devonian and into the Early Carboniferous. [15]

Later effects

The original form of the Orcadian Basin has been modified by a series of later tectonic events. In the late Carboniferous, the basin was partly inverted during dextral reactivation of the Great Glen Fault system. This caused widespread folding and local small-scale thrust faulting. [8] This was followed in the Permo-Triassic and Jurassic by a series of rift events, during which the Inner and Outer Moray Firth basins were formed. During the Early Cretaceous and again in the Cenozoic, the area was uplifted and eroded. [18] The Great Glen Fault was reactivated after the early Cretaceous, probably in sinistral sense by analogy with the connected Walls Boundary Fault, [19] although the exact timing is unknown. [18]

Palaeogeography

The landscape consisted of rounded hills formed of older metamorphic and igneous rock. The lakes varied in depth and extent from time to time, sometimes lapping against the side of the hills and sometimes retreating so that river flood plains were able to form. [20] Stromatolites can be found at Stromness, indicating that the lake was sometimes saline. Locally scolecodonts (marine microfossils) have been found in the Eday Marl suggesting at least a temporary connection to the sea. [16] The hills were bare of vegetation. [20] The land was not colonised by large plants as it is today, so erosion would therefore be rather rapid and probably seasonal, as would be lake productivity. This is reflected in the deep lake carbonates, which show very fine laminations, interpreted as varves. [21]

Fossils

Fauna

Fish living of the edge of the lake would float out into the centre, then sink and be preserved in the anoxic conditions prevailing at depth. The Achanarras quarry near Thurso has yielded the most extensive fish fauna and at least one example of all the following groups have been found there. [22]

Flora

Very few plant remains have been found and none in situ. There is evidence of algal and bacterial activity. [23]

Cultural and economic importance

Flagstone quarry near Thurso, Caithness Achscrabster quarry - geograph.org.uk - 823145.jpg
Flagstone quarry near Thurso, Caithness

The flagstone facies of the Middle Devonian lacustrine sequence has provided local building material since at least the Neolithic period. The houses at Skara Brae, the tomb at Maes Howe, the Ring of Brodgar and Standing Stones of Stenness, were all built with flagstone. The quarrying of flagstone became an important industry in the 18th century, particularly in Caithness. Flagstones from Caithness were exported round the world and are still being produced, although in more limited quantities. [24]

The lacustrine sequence has also acted as an oil source rock, being responsible, at least in part, for the oil accumulation in the Beatrice field in the Inner Moray Firth. [4]

Altar Stone

The Altar Stone in Stonehenge, a 6-tonne shaped sandstone block, originally thought to have come from South Wales, is now thought likely to have been brought from a site in the Orcadian Basin. This is based on the analysis of the age spectra of detrital mineral grains found in samples from the Altar Stone, which match closely with those of samples from the basin. [25]

See also

Related Research Articles

<span class="mw-page-title-main">Old Red Sandstone</span> Assemblage of rocks in the North Atlantic region

Old Red Sandstone, abbreviated ORS, is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the eastern seaboard of North America. It also extends northwards into Greenland and Svalbard. These areas were a part of the paleocontinent of Euramerica (Laurussia). In Britain it is a lithostratigraphic unit to which stratigraphers accord supergroup status and which is of considerable importance to early paleontology. The presence of Old in the name is to distinguish the sequence from the younger New Red Sandstone which also occurs widely throughout Britain.

<span class="mw-page-title-main">Great Glen Fault</span> Geological fault in Scotland

The Great Glen Fault is a strike-slip fault that runs through the Great Glen in Scotland. Occasional moderate tremors have been recorded over the past 150 years.

<span class="mw-page-title-main">Moine Thrust Belt</span> Fault in Highland, Scotland, UK

The Moine Thrust Belt or Moine Thrust Zone is a linear tectonic feature in the Scottish Highlands which runs from Loch Eriboll on the north coast 190 kilometres (120 mi) southwest to the Sleat peninsula on the Isle of Skye. The thrust belt consists of a series of thrust faults that branch off the Moine Thrust itself. Topographically, the belt marks a change from rugged, terraced mountains with steep sides sculptured from weathered igneous, sedimentary and metamorphic rocks in the west to an extensive landscape of rolling hills over a metamorphic rock base to the east. Mountains within the belt display complexly folded and faulted layers and the width of the main part of the zone varies up to ten kilometres, although it is significantly wider on Skye.

<span class="mw-page-title-main">Highland Boundary Fault</span> Geological fault zone crossing Scotland

The Highland Boundary Fault is a major fault zone that traverses Scotland from Arran and Helensburgh on the west coast to Stonehaven in the east. It separates two different geological terranes which give rise to two distinct physiographic terrains: the Highlands and the Lowlands, and in most places it is recognisable as a change in topography. Where rivers cross the fault, they often pass through gorges, and the associated waterfalls can be a barrier to salmon migration.

<span class="mw-page-title-main">Caledonian orogeny</span> Mountain building event caused by the collision of Laurentia, Baltica and Avalonia

The Caledonian orogeny was a mountain-building cycle recorded in the northern parts of the British Isles, the Scandinavian Caledonides, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 million years ago (Ma). It was caused by the closure of the Iapetus Ocean when the Laurentia and Baltica continents and the Avalonia microcontinent collided.

<span class="mw-page-title-main">Geology of Scotland</span>

The geology of Scotland is unusually varied for a country of its size, with a large number of different geological features. There are three main geographical sub-divisions: the Highlands and Islands is a diverse area which lies to the north and west of the Highland Boundary Fault; the Central Lowlands is a rift valley mainly comprising Palaeozoic formations; and the Southern Uplands, which lie south of the Southern Uplands Fault, are largely composed of Silurian deposits.

<i>Coccosteus</i> Extinct genus of fishes

Coccosteus is an extinct genus of arthrodire placoderm from the Devonian period. Its fossils have been found throughout Europe and North America. The majority of these have been found in freshwater sediments, though such a large range suggests that they may have been able to enter saltwater. It was a small placoderm, with Coccosteus cuspidatus measuring 29.6–39.4 cm (11.7–15.5 in) long.

<span class="mw-page-title-main">Geology of Orkney</span>

The geology of the Orkney islands in northern Scotland is dominated by the Devonian Old Red Sandstone (ORS). In the southwestern part of Mainland, this sequence can be seen to rest unconformably on a Moinian type metamorphic basement.

The Cheshire Basin is a late Palaeozoic and Mesozoic sedimentary basin extending under most of the county of Cheshire in northwest England. It extends northwards into the Manchester area and south into Shropshire. The basin possesses something of the character of a half-graben as its deepest extent is along its eastern and southeastern margins, where it is well defined by a series of sub-parallel faults, most important of which is the Red Rock Fault. These faults divide the basin from the older Carboniferous rocks of the Peak District and the North Staffordshire Coalfield.

<span class="mw-page-title-main">Hebridean Terrane</span> Part of the Caledonian orogenic belt in northwest Scotland

The Hebridean Terrane is one of the terranes that form part of the Caledonian orogenic belt in northwest Scotland. Its boundary with the neighbouring Northern Highland Terrane is formed by the Moine Thrust Belt. The basement is formed by Archaean and Paleoproterozoic gneisses of the Lewisian complex, unconformably overlain by the Neoproterozoic Torridonian sediments, which in turn are unconformably overlain by a sequence of Cambro–Ordovician sediments. It formed part of the Laurentian foreland during the Caledonian continental collision.

The Antarctic Peninsula, roughly 1,000 kilometres (650 mi) south of South America, is the northernmost portion of the continent of Antarctica. Like the associated Andes, the Antarctic Peninsula is an excellent example of ocean-continent collision resulting in subduction. The peninsula has experienced continuous subduction for over 200 million years, but changes in continental configurations during the amalgamation and breakup of continents have changed the orientation of the peninsula itself, as well as the underlying volcanic rocks associated with the subduction zone.

<span class="mw-page-title-main">Caithness Flagstone Group</span> Sequence of rock strata in Scotland

The Caithness Flagstone Group is a Devonian lithostratigraphic group in northern Scotland. The name is derived from the traditional county of Caithness where the strata are well exposed, especially in coastal cliffs.

<span class="mw-page-title-main">Eday Group</span> Group in Orkney Islands, Scotland, UK

The Eday Group is a Devonian lithostratigraphic group in Orkney, northern Scotland. The name is derived from the island of Eday where the strata are exposed in coastal cliffs.

<span class="mw-page-title-main">St Magnus Bay</span> Bay in Northwest of Mainland, Shetland

St Magnus Bay is a large coastal feature in the north-west of Mainland Shetland, Scotland. Roughly circular in shape with a diameter of about 19 kilometres (12 mi), it is open to the North Atlantic Ocean to the west. The indented coastline to the north, south and east between Esha Ness in the north and the Ness of Melby in the south contains numerous bays, firths and voes and there are several islands around the perimeter. The waters of the bay are up to 165 metres (541 ft) deep and may have been the site of a substantial meteor impact.

<span class="mw-page-title-main">Northern North Sea basin</span>

The North Sea is part of the Atlantic Ocean in northern Europe. It is located between Norway and Denmark in the east, Scotland and England in the west, Germany, the Netherlands, Belgium and France in the south.

<span class="mw-page-title-main">Geology of the southern North Sea</span> Largest gas producing basin

The North Sea basin is located in northern Europe and lies between the United Kingdom, and Norway just north of The Netherlands and can be divided into many sub-basins. The Southern North Sea basin is the largest gas producing basin in the UK continental shelf, with production coming from the lower Permian sandstones which are sealed by the upper Zechstein salt. The evolution of the North Sea basin occurred through multiple stages throughout the geologic timeline. First the creation of the Sub-Cambrian peneplain, followed by the Caledonian Orogeny in the late Silurian and early Devonian. Rift phases occurred in the late Paleozoic and early Mesozoic which allowed the opening of the northeastern Atlantic. Differential uplift occurred in the late Paleogene and Neogene. The geology of the Southern North Sea basin has a complex history of basinal subsidence that had occurred in the Paleozoic, Mesozoic, and Cenozoic. Uplift events occurred which were then followed by crustal extension which allowed rocks to become folded and faulted late in the Paleozoic. Tectonic movements allowed for halokinesis to occur with more uplift in the Mesozoic followed by a major phase of inversion occurred in the Cenozoic affecting many basins in northwestern Europe. The overall saucer-shaped geometry of the southern North Sea Basin indicates that the major faults have not been actively controlling sediment distribution.

<span class="mw-page-title-main">North German basin</span> Passive-active rift basin in central and west Europe

The North German Basin is a passive-active rift basin located in central and west Europe, lying within the southeasternmost portions of the North Sea and the southwestern Baltic Sea and across terrestrial portions of northern Germany, Netherlands, and Poland. The North German Basin is a sub-basin of the Southern Permian Basin, that accounts for a composite of intra-continental basins composed of Permian to Cenozoic sediments, which have accumulated to thicknesses around 10–12 kilometres (6–7.5 mi). The complex evolution of the basin takes place from the Permian to the Cenozoic, and is largely influenced by multiple stages of rifting, subsidence, and salt tectonic events. The North German Basin also accounts for a significant amount of Western Europe's natural gas resources, including one of the world's largest natural gas reservoir, the Groningen gas field.

<span class="mw-page-title-main">Nordfjord-Sogn Detachment</span> Zone of deformed rocks in Norway

The Nordfjord—Sogn Detachment (NSD) is a major extensional shear zone in Norway up to 6 km in thickness, which extends about 120 km along strike from Nordfjord to Sognefjord, bringing Devonian continental coarse clastic sedimentary rocks into close contact with eclogite facies metamorphic rocks of the Western Gneiss Region. It formed towards the end of the Caledonian Orogeny and was mainly active during the Devonian. It has an estimated displacement of at least 70 km and possibly as much as 110 km. It was reactivated during the Mesozoic and may have influenced the development of fault structures in the North Sea rift basin.

<span class="mw-page-title-main">Junggar Basin</span> Sedimentary basin in Xinjiang, China

The Junggar Basin, also known as the Dzungarian Basin or Zungarian Basin, is one of the largest sedimentary basins in Northwest China. It is located in Dzungaria in northern Xinjiang, and enclosed by the Tarbagatai Mountains of Kazakhstan in the northwest, the Altai Mountains of Mongolia in the northeast, and the Heavenly Mountains in the south. The geology of Junggar Basin mainly consists of sedimentary rocks underlain by igneous and metamorphic basement rocks. The basement of the basin was largely formed during the development of the Pangea supercontinent during complex tectonic events from Precambrian to late Paleozoic time. The basin developed as a series of foreland basins – in other words, basins developing immediately in front of growing mountain ranges – from Permian time to the Quaternary period. The basin's preserved sedimentary records show that the climate during the Mesozoic era was marked by a transition from humid to arid conditions as monsoonal climatic effects waned. The Junggar basin is rich in geological resources due to effects of volcanism and sedimentary deposition. According to Guinness World Records it is a land location remotest from open sea with great-circle distance of 2,648 km from the nearest open sea at 46°16′8″N86°40′2″E.

<span class="mw-page-title-main">Hornelen Basin</span> Sedimentary basin in Vestland, Norway

The Hornelen Basin is a sedimentary basin in Vestland, Norway, containing an estimated 25 km stratigraphic thickness of coarse clastic sedimentary rocks of Devonian age. It forms part of a group of basins of similar age along the west coast of Norway between Sognefjord and Nordfjord, related to movement on the Nordfjord-Sogn Detachment. It formed as a result of extensional tectonics as part of the post-orogenic collapse of crust that was thickened during the Caledonian Orogeny towards the end of the Silurian period. It is named for the mountain Hornelen on the northern margin of the basin.

References

  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. Archived from the original (PDF) on 7 March 2012. Retrieved 26 February 2012.
  4. 1 2 Duncan, W.I.; Buxton N.W.K. (1995). "hydrocarbon source potential on the East Shetland Platform, North Sea New evidence for evaporitic Middle Devonian lacustrine sediments with hydrocarbon source potential on the East Shetland Platform, North Sea". Journal of the Geological Society. 152 (2). Geological Society: 251–258. Bibcode:1995JGSoc.152..251D. doi:10.1144/gsjgs.152.2.0251. S2CID   131618967 . Retrieved 22 January 2012.
  5. ↑ Norton, M,G; McClay K.R.; Way N.A. (1987). "Tectonic evolution of Devonian basins in northern Scotland and southern Norway" (PDF). Norsk Geologisk Tidsskrift. 67 (4): 323–338.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ↑ McClay, K.R.; Norton M.G.; Coney P.; Davis G.H. (1986). "Collapse of the Caledonian orogen and the Old Red Sandstone". Nature. 323 (6084): 147–149. Bibcode:1986Natur.323..147M. doi:10.1038/323147a0. S2CID   4370677.
  7. ↑ Dewey, J.F.; Strachan R.A. (2003). "Changing Silurian–Devonian relative plate motion in the Caledonides: sinistral transpression to sinistral transtension". Journal of the Geological Society. 160 (2). Geological Society: 219–229. doi:10.1144/0016-764902-085. S2CID   129100037 . Retrieved 28 January 2012.
  8. 1 2 Rogers, D.A.; Marshall J.E.A.; Astin T.R. (1989). "Devonian and later movements on the Great Glen fault system, Scotland". Journal of the Geological Society. 146 (3). Geological Society: 369–372. doi:10.1144/gsjgs.146.3.0369. S2CID   128498128 . Retrieved 28 January 2012.
  9. ↑ Mendum, J.R.; Noble, S.R. (2010). "Mid-Devonian sinistral transpressional movements on the Great Glen Fault: the rise of the Rosemarkie Inlier and the Acadian Event in Scotland" (PDF). In Law R.D.; Butler R.W.H.; Holdsworth R.E.; Krabbendam M.; Strachan R.A. (eds.). Continental Tectonics and Mountain Building: The Legacy of Peach and Horne. Special Publications. Vol. 335. London: Geological Society. pp. 161–187. ISBN   978-1-86239-300-4 . Retrieved 28 January 2012.
  10. ↑ Marshall, J.A.E. (1998). "The recognition of multiple hydrocarbon generation episodes: an example from Devonian lacustrine sedimentary rocks in the Inner Moray Firth, Scotland". Journal of the Geological Society . 155 (2). Geological Society: 335–352. Bibcode:1998JGSoc.155..335M. doi:10.1144/gsjgs.155.2.0335. S2CID   130545880 . Retrieved 28 January 2012.
  11. ↑ Richards, P.C. (1985). "A Lower Old Red Sandstone lake in the offshore Orcadian Basin". Scottish Journal of Geology. 21 (3). London: Geological Society: 381–383. doi:10.1144/sjg21030381. S2CID   129710660 . Retrieved 27 February 2012.
  12. ↑ Clarke, P.; Parnell J. (1999). "Facies analysis of a back-tilted lacustrine basin in a strike-slip zone, Lower Devonian, Scotland". Palaeogeography, Palaeoclimatology, Palaeoecology. 151 (1–3). Elsevier: 167–190. Bibcode:1999PPP...151..167C. doi:10.1016/S0031-0182(99)00020-6.
  13. ↑ Reading, H.G. (1996). Sedimentary environments: processes, facies, and stratigraphy (3 ed.). John Wiley & Sons. p. 113. ISBN   978-0-632-03627-1 . Retrieved 2 March 2012.
  14. 1 2 3 Marshall, J.A.E.; Astin, T.R.; Brown, J.F.; Mark-Kurik E.; Lazauskiene J. (2007). "Recognizing the Kačák Event in the Devonian terrestrial environment and its implications for understanding land–sea interactions". In Becker R.T.; Kirchgasser W.T. (eds.). Devonian events and correlations. Special Publications. Vol. 278. London: Geological Society. pp. 133–155. ISBN   9781862392229 . Retrieved 28 January 2012.
  15. 1 2 Marshall, J.E.A.; Hewett, T. (2003). "6: Devonian". In Evans D.; Graham C.; Armour A.; Bathurst P. (eds.). The Millennium Atlas. London: Geological Society. pp. 6–1 to 6–16. ISBN   978-1-86239-119-2.
  16. 1 2 Marshall, J.E.A.; Rogers, D.A.; Whitely, M.J. (1996). "Devonian marine incursions into the Orcadian Basin, Scotland". Journal of the Geological Society . 153 (3). Geological Society: 451–466. Bibcode:1996JGSoc.153..451M. doi:10.1144/gsjgs.153.3.0451. S2CID   129433694 . Retrieved 28 January 2012.
  17. ↑ Odling, N.W.A. "Point of Ayre" (PDF). Volume 17: Caledonian Igneous Rocks of Great Britain Chapter 9: Late Silurian and Devonian volcanic rocks of Scotland. Retrieved 29 January 2012.
  18. 1 2 Thomson, K.; Underhill, J.R. (1993). "Controls on the development and evolution of structural styles in the Inner Moray Firth Basin". In Parker J.R. (ed.). Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference. London: Geological Society. pp. 1167–1178. Retrieved 29 January 2012.
  19. ↑ Watts, L.M.; Holdsworth R.E.; Sleight J.A.; Strachan R.A.; Smith S.A.F. (2007). "The movement history and fault rock evolution of a reactivated crustal-scale strike-slip fault: the Walls Boundary Fault Zone, Shetland" (PDF). Journal of the Geological Society. 164 (5). Geological Society: 1037–1058. doi:10.1144/0016-76492006-156. S2CID   129369241 . Retrieved 29 January 2012.
  20. 1 2 Stephen Jay Gould. The Book of Life. Ebury Hutchinson, 1993
  21. ↑ Trewin, N.H.; Davidson, R.G. (1999). "Lake-level changes, sedimentation and faunas in a Middle Devonian basin-margin fish bed". Journal of the Geological Society. 156 (3): 535–548. doi:10.1144/gsjgs.156.3.053.
  22. ↑ "Orkney and Shetland SNH Online Publication - Life on Earth". Archived from the original on 2011-05-06. Retrieved 2007-10-16.
  23. ↑ R. O. Muir and J. M. Ridgway, Mineralium Deposita, Volume 10 Number 3, pp 205–215
  24. ↑ McMillan, A.; Hyslop E.; Maxwell I.; McKinney A. (2006). "Indigenous stone resources for Scotland's Built Heritage" (PDF). IAEG2006 Paper number 825. London: Geological Society. pp. 2–3. Archived from the original (PDF) on 23 September 2010. Retrieved 27 February 2012.
  25. ↑ Clarke, A.J.I.; Kirkland, C.L.; Bevins, R.E.; Pearce, N.J.G.; Glorie, S.; Ixer, R.A. (2024). "A Scottish provenance for the Altar Stone of Stonehenge". Nature. 632: 570–575. doi:10.1038/s41586-024-07652-1. PMC   11324516 .

59°00′N1°30′W / 59.0°N 1.5°W / 59.0; -1.5

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.