Avalonia

Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States. Avalonia is named for the Avalon Peninsula in Newfoundland.

Avalonia developed as a volcanic arc on the northern margin of Gondwana. It eventually rifted off, becoming a drifting microcontinent. The Rheic Ocean formed behind it, and the Iapetus Ocean shrank in front. It collided with the continents Baltica, then Laurentia, and finally with Gondwana, ending up in the interior of Pangea. When Pangea broke up, Avalonia's remains were divided by the rift which became the Atlantic Ocean.

AVALONIA
The terranes of Avalonia with modern borders for orientation: 1 Laurentia; 2 Baltica; 3 Proto-Tethys Ocean; 4 Western Avalonia; 5 Eastern Avalonia.
US: United States; CT: Connecticut; MA: Massachusetts; NH: New Hampshire; ME: Maine; RI: Rhode-Island
CA: Canada; NB: New Brunswick; NFL: Newfoundland; NS: Nova-Scotia; PE: Prince Edward Island
Europe: IE: Ireland; UK: United Kingdom; FR: France; BE: Belgium; NL: Netherlands; DE: Germany; PL: Poland

Development

Avalonia entwicklung odovizium silur
Schematic diagram of the paleogeographic evolution of Avalonia, Baltica and Laurentia. (Names in German.)
Caledonides EN
Location of the Caledonian/Acadian mountain chains in the Early Devonian Epoch. Present day coastlines are shown for reference. Red lines are sutures, capitalized names are the different continents/super-terranes that joined during the Caledonian orogeny.
Euramerica en
The Old Red Sandstone Continent in the Devonian

The early development of Avalonia is believed to have been in volcanic arcs near a subduction zone on the margin of Gondwana.[1] Some material may have accreted from volcanic island arcs which formed further out in the ocean and later collided with Gondwana as a result of plate tectonic movements. The igneous activity had started by 730 million years ago and continued until around 570 million years ago, in the late Neoproterozoic.[2]

In the early Cambrian, the supercontinent Pannotia broke up and Avalonia drifted off northwards from Gondwana. This independent movement of Avalonia started from a latitude of about 60° South. The eastern end of Avalonia collided with Baltica, a continental plate occupying the latitudes from about 30°S to 55°S, as Baltica slowly rotated counterclockwise towards it. This happened at the end of the Ordovician and during the early Silurian.

In the late Silurian and lower Devonian, the combined Baltica and Avalonia collided progressively, with Laurentia, beginning with the long extremity of Avalonia which is now attached to North America. The result of this was the formation of Euramerica. At the completion of this stage, the site of Britain was at 30°S and Nova Scotia at about 45°S. This collision is represented by the Caledonian folding or in North America as an early phase in the Acadian orogeny.

In the Carboniferous, the new continent and another terrane, Armorica which included Iberia, drifted in from Gondwana, trapping Avalonia between it and the continent so adding Iberia/Armorica to Euramerica. This was followed up by the arrival of Gondwana. The effects of these collisions are seen in Europe as the Variscan folding. In North America it shows as later phases of the Acadian orogeny. This was happening at around the Equator during the later Carboniferous, forming Pangaea with Avalonia near its centre but partially flooded by shallow sea.

In the Jurassic, Pangaea split into Laurasia and Gondwana, with Avalonia as part of Laurasia. In the Cretaceous, Laurasia broke up into North America and Eurasia with Avalonia split between them.

Iberia was later rotated away again as the African part of Gondwana strike-slipped past it. This last movement caused the Alpine orogeny including the raising of the Pyrenees during the Miocene and Pliocene. As a result of this, part of Avalonia is now to be found on each side of the Straits of Gibraltar.

Consequences

Avalonia in Europe
This map shows the positions of the rocks of Avalonia remaining in Europe. The notes on it indicate the part which collided with Baltica in the upper Ordovician and that which collided with Laurentia in the Silurian. The parts of Avalonia now in Iberia and Morocco were carried there by rotation of Iberia during the subsequent collision with Gondwana followed by separation. These rocks are by no means all at the modern surface.

The Avalonian part of Great Britain almost exactly coincides with England and Wales. Elsewhere in Europe, parts of Avalonia are found in the Ardennes of Belgium and north-eastern France, north Germany, north-western Poland, south-eastern Ireland, and the south-western edge of the Iberian Peninsula.

Part of the British-Belgian section formed an island in the Carboniferous, affecting the disposition of coalfields; this is known by names such as the 'London-Brabant Island'. Its bulk had an effect on the geological structure between the Ardennes and the English Midlands by influencing the subsequent crustal folding resulting from the Variscan collision.

In Canada, Avalonia comprises the Avalon Peninsula of southeast Newfoundland, southern New Brunswick, part of Nova Scotia, and Prince Edward Island. In the United States, Avalonia consists of northern coastal Maine, all of Rhode Island, and other sections of coastal New England.

See also

References

  1. ^ Murphy, J. B.; Pisarevsky, S. A.; Nance, R. D.; Keppie, J. D. (2001). Jessell, M. J. (ed.). "Animated history of Avalonia in Neoproterozoic - Early Proterozoic" (PDF). General Contributions. Journal of the Virtual Explorer. 3: 45–58. Retrieved November 2015. Check date values in: |accessdate= (help)
  2. ^ Strachan, R. A. (2000). "Late Neoproterozoic to Cambrian accretionary history of Eastern Avalonia and Armorica on the active margin of Gondwana". In Woodcock, N. H.; Strachan, R. A. (eds.). Geological History of Britain and Ireland. Blackwell. pp. 127–139. Retrieved November 2015. Check date values in: |accessdate= (help)

External links

Acadian orogeny

The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the early Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago, with deformational, plutonic, and metamorphic events extending into the Early Mississippian. The Acadian orogeny is the third of the four orogenies that created the Appalachian orogen and subsequent basin. The preceding orogenies consisted of the Potomac and Taconic orogeny, which followed a rift/drift stage in the Late Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental fragments with the Laurasian continent. Geographically, the Acadian orogeny extended from the Canadian Maritime provinces migrating in a southwesterly direction toward Alabama. However, the Northern Appalachian region, from New England northeastward into Gaspé region of Canada, was the most greatly affected region by the collision.It was roughly contemporaneous with the Bretonic phase of the Variscan orogeny of Europe, with metamorphic events in southwestern Texas and northern Mexico, and with the Antler orogeny of the Great Basin.

Aspy River

The Aspy River is a river on northeastern Cape Breton Island which rises in the Cape Breton Highlands and empties into Aspy Bay. The river valley follows the ancient Aspy Fault which extends for 40 km inland from the coast and extends along the upper section of the northeast Margaree River. This geological fault is thought to be a part of the Cabot Fault (Newfoundland)/ Great Glen Fault (Scotland) system of Avalonia.It is believed by some sources that John Cabot landed at Aspy Bay in 1497. In 1856, a submarine cable was laid across the Cabot Strait from Aspy Bay to Newfoundland establishing a telegraph link between St. John's, Newfoundland and New York City.

A dirt road in Cape Breton Highlands National Park leads to the Beulach Ban falls on the North Aspy River. "Beulach Ban" is Gaelic for "white gorge".

Avalonianus

Avalonianus is a name used for fossil teeth from the Late Triassic of England. It was first described in 1898 by Harry Seeley with the name Avalonia, but that name was preoccupied (Walcott, 1889), so Kuhn renamed it in 1961. It was thought to be a prosauropod, but later analysis revealed it was actually a chimera, with the original teeth coming from a non-dinosaurian ornithosuchian (or possibly an early theropod), and later-referred post-cranial prosauropod remains (which were renamed Camelotia).

Borrowdale Volcanic Group

The Borrowdale Volcanic Group is a group of igneous rock formations named after the Borrowdale area of the Lake District, in England. They are Caradocian (late Ordovician) in age (roughly 450 million years old). It is thought that they represent the remains of a volcanic island arc, approximately similar to the island arcs of the west Pacific today. This developed as oceanic crust to the (present) north-west and was forced by crustal movement under a continental land-mass to the present south-east. Such forcing under, as two plates meet, is termed subduction. This land-mass has been named Avalonia by geologists. It is now incorporated into England and Wales and a sliver of North America.

At that time the rocks that now comprise most of Scotland (and part of the northern Irish landmass) were not attached to Avalonia. They were separated by an ocean, called the Iapetus Ocean by geologists. The line of joining, or suture, is approximately under the Solway Firth and Cheviot Hills. In the Lake District, the junction between the early Ordovician series, Skiddaw Slate, and the Borrowdale Volcanic that was forced under it, can be seen on the slopes of Fleetwith Pike.

In the English Lake District, the Borrowdale Volcanic Group is composed of lavas (mainly andesites), tuffs and agglomerates, along with some major igneous intrusions. These rocks of the Borrowdale Volcanic Group give rise to dramatic scenery. The mountainous nature of the area, its high rainfall and the relative impermeability of the rock give rise to a high risk of storm flooding as demonstrated by the 2009 flooding of Cockermouth.

The upper boundary of the group is an unconformity with the overlying Windermere Supergroup. The lower boundary is an unconformity with the underlying Skiddaw Group.The outcrop of this sequence on Crinkle Crags (and other surrounding peaks in the Lake District), was chosen as one of the top 100 geosites in the United Kingdom by the Geological Society of London.

Cadomian Orogeny

The Cadomian Orogeny was a tectonic event or series of events in the late Neoproterozoic, about 650–550 Ma, which probably included the formation of mountains. This occurred on the margin of the Gondwana continent, involving one or more collisions of island arcs and accretion of other material at a subduction zone. The precise events, and geographical position, are uncertain, but are thought to involve the terranes of Avalonia, Armorica and Iberia. Rocks deformed in the orogeny are found in several areas of Europe, including northern France, the English Midlands, southern Germany, Bohemia, southern Poland and the southwest Iberian Peninsula. The name comes from Cadomus, the Latin name for Caen, northern France. L Bertrand gave the orogeny its name in 1921, naming it after Cadomus the Gaulish name for Caen in Normandy. He defined the end as being marked by Lower Palaeozoic red beds.

The interpretation is that the belt was formed as oceanic crust subducted below the Armorica land mass in a similar way to the Andes. Sediments deposited on the continental margin were pushed up onto the continent, at the same time as intrusions of calc-alkaline magmas occurred.

Caledonian orogeny

The Caledonian orogeny was a mountain-building era recorded in the northern parts of Ireland and Britain, the Scandinavian Mountains, 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 continents and terranes of Laurentia, Baltica and Avalonia collided.

The Caledonian orogeny is named for Caledonia, the Latin name for Scotland. The name was first used in 1885 by Austrian geologist Eduard Suess for an episode of mountain building in northern Europe that predated the Devonian period. Geologists like Émile Haug and Hans Stille saw the Caledonian orogeny as one of several episodic phases of mountain building that had occurred during Earth's history. Current understanding has it that the Caledonian orogeny encompasses a number of tectonic phases that can laterally be diachronous. The name "Caledonian" can therefore not be used for an absolute period of geological time, it applies only to a series of tectonically related events.

Carcinosomatoidea

Carcinosomatoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of the superfamilies classified as part of the suborder Eurypterina.

Some carcinosomatoid genera have been suggested to have been fully marine as opposed to living in near-shore brackish or hypersaline environments.The majority of carcinosomatoid taxa are known from the paleocontinents of Laurentia, Baltica and Avalonia. Isolated and fragmentary fossils from the Late Silurian of Vietnam and the Czech Republic show that the terranes of Annamia and Perunica were within the geographical range of the carcinosomatoids. Only a few basal carcinosomatoids (e.g. Carcinosoma and Paracarcinosoma) have been found in deeper waters whilst the more derived forms, such as Mixopterus and Lanarkopterus have not. Basal carcinosomatoids (Carcinosomatidae) are likely responsible for the fossil remains in Vietnam and the Czech Republic and may have had a distribution similar to the cosmopolitan distribution of the pterygotoids, though were not as common nor as successful.

Euramerica

Euramerica (also known as Laurussia – not to be confused with Laurasia, – the Old Red Continent or the Old Red Sandstone Continent) was a minor supercontinent created in the Devonian as the result of a collision between the Laurentian, Baltica, and Avalonia cratons during the Caledonian orogeny, about 410 million years ago. In the Late Carboniferous, tropical rainforests lay over the equator of Euramerica. A major, abrupt change in vegetation occurred when the climate aridified. The forest fragmented and the lycopsids which dominated these wetlands thinned out, being replaced by opportunistic ferns. There was also a great loss of amphibian diversity and simultaneously the drier climate spurred the diversification of reptiles.

Geology of England

The geology of England is mainly sedimentary. The youngest rocks are in the south east around London, progressing in age in a north westerly direction. The Tees-Exe line marks the division between younger, softer and low-lying rocks in the south east and the generally older and harder rocks of the north and west which give rise to higher relief in those regions. The geology of England is recognisable in the landscape of its counties, the building materials of its towns and its regional extractive industries.

Iapetus Ocean

The Iapetus Ocean was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago). The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia. The ocean disappeared with the Acadian, Caledonian and Taconic orogenies, when these three continents joined to form one big landmass called Euramerica. The "southern" Iapetus Ocean has been proposed to have closed with the Famatinian and Taconic orogenies, meaning a collision between Western Gondwana and Laurentia.

Because the Iapetus Ocean was positioned between continental masses that would at a much later time roughly form the opposite shores of the Atlantic Ocean, it can be seen as a sort of precursor of the Atlantic. The Iapetus Ocean was therefore named for the titan Iapetus, who in Greek mythology was the father of Atlas, after whom the Atlantic Ocean was named.

LittleBigPlanet 2

LittleBigPlanet 2 is a puzzle-platformer video game that features user-generated content. The game is developed by Media Molecule, published by Sony Computer Entertainment for PlayStation 3. It was originally scheduled for release in November 2010 but was delayed until January 2011. The game was released in North America on 18 January 2011, in mainland Europe on 19 January 2011, in Australia and New Zealand on 20 January 2011 and the UK and Ireland on 21 January 2011.It is a direct sequel to the critically acclaimed 2008 title LittleBigPlanet and the third game in the series following a PSP version released in 2009. Most of the more than 3 million levels created by users in the first game carry over and are playable and editable in LittleBigPlanet 2. Unlike its predecessor, which was marketed as a platform game, LittleBigPlanet 2 was marketed as a "platform for games". Support for PlayStation Move was added to the game through a software update in September 2011, allowing users to play the game using the PlayStation Move motion controller in conjunction with a Navigation Controller or gamepad.

Mistaken Point Ecological Reserve

Mistaken Point Ecological Reserve is a wilderness area and a UNESCO World Heritage Site located at the southeastern tip of Newfoundland's Avalon Peninsula in the Canadian province of Newfoundland and Labrador. The reserve is home to the namesake Mistaken Point Formation, which contains one of the most diverse and well-preserved collections of Precambrian fossils in the world. Ediacaran fossils discovered at the site constitute the oldest known remnants of multicellular life on Earth.

Rheic Ocean

The Rheic Ocean was an ocean which separated two major palaeocontinents, Gondwana and Laurussia (Laurentia-Baltica-Avalonia). One of the principal oceans of the Palaeozoic, its sutures today stretch 10,000 km (6,200 mi) from Mexico to Turkey and its closure resulted in the assembly of the supercontinent Pangaea and the formation of the Variscan–Alleghenian–Ouachita orogenies.

Sandy Point Island

Sandy Point Island (more commonly referred to as Sandy Point) is a 35-acre island in Little Narragansett Bay, lying mostly in Westerly, Rhode Island and partly in Stonington, Connecticut. Once an extension of Napatree Point, Sandy Point is now a mile-long island that serves as an important nature preserve and recreation site. Sandy Point is the westernmost piece of land in the state of Rhode Island.

Tornquist Sea

The Tornquist Sea or Tornquist Ocean was a sea located between the palaeocontinents Avalonia and Baltica about 600 to 450 million years ago. The remains of the sea today form a suture stretching across northern Europe (Tornquist Zone).

Trans-European Suture Zone

The Trans-European Suture Zone (TESZ), also known as the Tornquist Zone, is the crustal boundary between the Precambrian East European Craton and the Phanerozoic orogens of South-Western Europe. The zone runs from the North Sea to the Black Sea. The north-western part of the zone was created by the collision of Avalonia and Baltica/East European Craton in the Late Ordovician. The south-eastern part of the zone, now largely concealed by deep sedimentary basins, developed through Variscan and Alpine orogenic events.

Various branches of the TESZ go under different names:

The Teisseyre-Tornquist Zone (TTZ) in Ukraine and Poland.

The Sorgenfrei-Tornquist Zone (STZ) through Scania (Sweden), Kattegat, and North Jutland (Denmark).

The Trans-European Fault (TEF), Thor-Tornquist Suture or Thor Suture through southern Denmark.The later two branches (STZ and TEF) span a triangular area of numerous faults, called the Tornquist Fan.

Variscan orogeny

The Variscan or Hercynian orogeny is a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea.

Welsh Basin

The Welsh Basin was a northeast-southwest aligned back-arc depositional basin during the Cambrian, Ordovician and Silurian periods during which a considerable thickness of marine sediments was laid down in the area. To the southeast lay the Midland Platform (a part of the micro-continent of Avalonia) and to the northwest, within the Iapetus Ocean, through what is now Ireland and the Lake District, was an island arc; a northeast-southwest aligned Irish Sea landmass which was associated with volcanic activity. Examination of the sediments and associated fossils allows the deeper centre of the basin to be distinguished from shallower 'platform' areas along its southeastern margins. From the middle Silurian onwards, collision of Avalonia with the more northerly continent of Laurentia occurred giving rise to the Caledonian Orogeny. The inversion of the basin occurred at that time i.e. its uplift and deformation.

The southeastern limit of the Welsh Basin can be defined as the Welsh Borderland Fault Zone comprising the Pontesford-Linley Fault and Church Stretton Fault which stretch from Pembrokeshire to Shropshire and, in the northwest, the Menai Strait Fault Zone. Its extent to the southwest and northeast is uncertain as these areas are cloaked by more recent rocks.

Siliciclastic material was derived from the landmass to its southeast Pretannia, some being deposited in the shallower margins before subsequently being redeposited as turbidites as the sediment mass became unstable from time to time. In addition to the sedimentary rocks of the Welsh Basin, there are a number of volcanic formations within the overall sequence, particularly within the Ordovician system.Typical of the sediments of the Welsh Basin are the Llandovery age Aberystwyth Grits which outcrop along the middle coastal section of Cardigan Bay and comprise alternating mudstones and turbiditic sandstones.

Weymouthiidae

The Weymouthiidae are an extinct family of eodiscinid agnostid trilobites. They lived during the late Lower Cambrian and earliest Middle Cambrian (Botomian to Delamaran) in the so-called Olenellus- and Eokochaspis-zones in the former paleocontinents of Laurentia, Avalonia, Gondwana. The Weymouthiidae are all blind and lack free cheeks.

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