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36-747: 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. Continental sediments of

72-453: A clear day it is possible to see Wick in the far north of Scotland more than 80 km (50 mi) away. From Lossiemouth it is possible to see the hills of Caithness and the hills are easily identified, one being Morven and the other being Scaraben. From Burghead , the white mass of Dunrobin Castle can just be made out in the distance on a very clear day; from Nairn, the two red bands on

108-524: A mixture of coarse, often conglomeratic sediments, combined with organic-rich lacustrine shales, such as those exposed at Strathpeffer . 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

144-511: 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. 59°00′N 1°30′W  /  59.0°N 1.5°W  / 59.0; -1.5 Moray Firth The Moray Firth ( / ˈ m ʌr i -/ ; Scottish Gaelic : An Cuan Moireach , Linne Mhoireibh or Caolas Mhoireibh )

180-759: Is a roughly triangular inlet (or firth ) of the North Sea , north and east of Inverness , which is in the Highland council area of the north of Scotland . It is the largest firth in Scotland, stretching from Duncansby Head (near John o' Groats ) in the north, in the Highland council area, and Fraserburgh in the east, in the Aberdeenshire council area, to Inverness and the Beauly Firth in

216-517: 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. This unit splits the flagstone sequence into two parts known regionally as the Lower and Upper Orcadian Flagstone formations. In mid-Givetian times, the dominant lake environment gave way to mainly fluvial conditions, with

252-646: Is derived from the island of Eday where the strata are exposed in coastal cliffs. These rocks are exposed throughout Orkney, notably in coastal cliffs of Eday and western Sanday , South Ronaldsay and the Deerness peninsula of Mainland . 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. The Group comprises

288-542: Is the site of the Beatrice Wind Farm . Much of the fishing industry focuses on scallops and Norway lobsters . The area also contains the Moray East (completed) and Moray West (to be completed in 2025) offshore wind farms. The Inner Moray Firth is designated as a special protection area for wildlife conservation purposes. The Moray Firth contains a special area of conservation (SAC) designated under

324-654: The Gaelic for sea, whilst Murav and Morav are believed to be rooted in Celtic words Mur (sea) and Tav (side), condensed to Mur'av for sea-side. The firth has, in the past, been referred to as the Murro Firth and the Morra Firth. 'Murro' and 'Morra' being variants of Moray; these older variations are also shown in older names for Morayshire itself, such as Morrowshire. A number of rivers flow into

360-560: The Great Glen Fault , which passes through the centre of the basin, was the main cause of basin formation. 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. However, the uplift of a block containing late granitic veins within

396-712: The Tarbat Ness Lighthouse around 30 km (20 mi) away, can be seen with binoculars. The Great Channel in the Inner Moray Firth, was dredged by engineers in 1917 for the safe passage of ships that wanted to avoid the long and dangerous passage around the north of Scotland, by transiting the Caledonian Canal . The Channel went from the entrance of Munlochy Bay to the Meikle Mee Starboard Hand Mark, but

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432-597: The common dolphin and minke whale . The popular wildlife viewing area located at Chanonry Point host some spectacular displays of dolphins within the inner Moray Firth. Also, visitor centres at Spey Bay and North Kessock are run by the Whale and Dolphin Conservation Society , where dolphins and other wildlife can often be seen. The old jetty at the Fort George Point is the location of

468-584: 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. Other tectonic models have suggested that transtensional sinistral (left lateral) strike-slip movement on

504-606: The Dolphin Research Centre, with leading marine biologist Prof. Greame Taylor working part-time studying hunting and breeding habits and part-time working with the Community Council giving tours and teaching the ways of the dolphin. It is also an important oil field and fishing grounds. The Beatrice oil field about 20 miles south of Wick and east of Helmsdale was the closest of the North Sea oil fields; since being decommissioned in 2017 it

540-642: The EU Habitats Directive, which is one of the largest marine protection areas in Europe. The SAC protects the inner waters of the Moray Firth, from a line between Lossiemouth (on the south coast) and Helmsdale (on the north coast) westwards. Eday Group The Eday Group is a Devonian lithostratigraphic group (a sequence of rock strata ) in Orkney , northern Scotland . The name

576-627: The Late Devonian Sandsting Granite. 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. The original form of the Orcadian Basin has been modified by a series of later tectonic events. In

612-634: 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

648-759: The Moray Firth, including the River Ness , the River Findhorn and the River Spey . Various smaller firths and bays are inlets of the firth, including the Cromarty Firth and the Dornoch Firth . The Pentland Firth has its eastern mouth at the Moray Firth's northern boundary. The Moray Firth is effectively two firths, the Inner Moray Firth 57°33′N 04°09′W  /  57.550°N 4.150°W  / 57.550; -4.150 , which

684-624: 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 stage of the Devonian period. The sediments vary from fluvial to lacustrine to lagoonal. On the island of Hoy , the Hoy Sandstone is a particularly thick formation at whose base

720-477: 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. 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

756-628: 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. On the Orkney Islands, volcanic rocks are found within

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792-415: 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

828-420: 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. Very few plant remains have been found and none in situ. There is evidence of algal and bacterial activity. The flagstone facies of

864-597: The fossil fish fauna preserved at one level in this unit, it is known to have been particularly diverse and widespread in its occurrence. 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

900-515: 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 km with a maximum estimated depth of at least 100 metres. From

936-534: 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. The hills were bare of vegetation. 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 . Fish living of

972-682: 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 . 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. The Great Glen Fault

1008-526: 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 . The Devonian of West Mainland in the Shetland Islands contains more volcanic rocks and the upper middle Devonian sequence there is intruded by

1044-565: 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

1080-512: The rivers draining into the bay have estuaries . Masses of sediment from the adjacent mountains have formed spits around several mouths. Those of River Ness and River Carron have significantly narrowed the fjords they enter. The Moray Firth is one of the most important places on the British coast for observing dolphins and whales . The most common species are the bottlenose dolphin and harbour porpoise , with occasional sightings of

1116-630: 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 . In common with

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1152-477: The west. Therefore, three council areas have Moray Firth coastline: Highland to the west and north of the Moray Firth and Highland, Moray and Aberdeenshire to the south. The firth has more than 500 miles (800 km) of coastline, much of which is cliff. The firth is named after the 10th-century Province of Moray , whose name in turn is believed to derive from the sea of the firth itself. The local names Murar or Morar are suggested to derive from Muir ,

1188-537: The world and are still being produced, although in more limited quantities. 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. 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

1224-542: Was not maintained and filled in very quickly. The Moray Firth is of tectonic origin, the formation is related in part to the Helmsdale Fault . For some time during the last ice age , the whole of the present day Moray Firth was a huge glacier. Nevertheless, the inner part and its side-inlets, the Cromarty Firth and Dornoch Firth , are true fjords themselves. Though there is a reasonable tide with mean tide ranges of about three metres (ten feet), only some of

1260-488: Was reactivated after the early Cretaceous, probably in sinistral sense by analogy with the connected Walls Boundary Fault, although the exact timing is unknown. 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. Stromatolites can be found at Stromness, indicating that

1296-456: Was traditionally known as the Firth of Inverness, and the Outer Moray Firth which is more open North Sea water. The name "Firth of Inverness" is rarely found on modern maps, but extended from the Beauly Firth in the west, to Chanonry Point in the east. The Moray Firth is visible for considerable distances, including a long range view from as far to the east as Longman Hill . From Buckie , on

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