The Iapetus Suture is one of several major geological faults caused by the collision of several ancient land masses forming a suture. It represents in part the remains of what was once the Iapetus Ocean. Iapetus was the father of

Atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...

in Greek mythology, making his an appropriate name for what used to be called the 'Proto-Atlantic Ocean'. When the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

opened, in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period, it took a slightly different line from that of the Iapetus suture, with some originally

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

n rocks being left behind in north-west

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

and other, Avalonian, rocks remaining as part of Newfoundland.

Background

The Iapetus Ocean was an ancient ocean which existed in the Southern Hemisphere approximately 600 million years ago and was bordered by several paleocontinents:

Ganderia Ganderia or Gander Terrane (located near the town Gander, Newfoundland and Labrador, Gander, Newfoundland) is a terrane in the northern Appalachians which broke off the supercontinent Gondwana (Ma) together with Avalonia, Megumia, and Carolinia. ...

, Carolinia, Avalonia, and

Baltica Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, ...

. During a series of geological events, the Salinic orogeny and

Caledonian orogeny The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that ...

all three land masses began to converge upon each other slowly diminishing the ocean by subducting the oceanic crust. By the end of the

Silurian period The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

, approximately 420 million years ago, the ocean had disappeared. The geological fault zone resulting from the continental collision is known as the Iapetus Suture, named after the ocean it replaced. The closure of Iapetus involved a complex and protracted collisional history of numerous

continental fragment Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Cau ...

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...

s and back-arc basins that were accreted to

and Avalonia between the Early

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

and Late Silurian. The notion of a single suture zone in a complex orogen such as the Appalachian/Caledonian is unrealistic as several temporal and spatial distinct suture zones are present.

In Canada

The Early Ordovician (Taconic) Baie Verte Line in

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

and Newfoundland marks the boundary between the continental margin of Laurentia and Iapetan oceanic rocks, while the Early Ordovician (Penobscot) GRUB Line defines the contact between the vestiges of Iapetus and

. The Middle Ordovician Red Indian Line is considered the main Iapetan suture zone in that it separates peri-Laurentian and peri-Gondwanan oceanic elements. The Dog Bay Line is a younger feature in the Appalachians and delineates the terminal Iapetan suture in Newfoundland as it marks the Early Silurian (Salinic) collisional zone between Ganderia and Laurentia.

In the United States

The suture runs through the north-eastern states of Maine, New Hampshire, Massachusetts and Connecticut. Rhode Island lies entirely to the east of the suture.

In Ireland

The estuary of the River Shannon (Ireland's largest river) follows the line of the Iapetus suture on the west coast. The suture reaches the east coast at

Clogherhead Clogherhead () is a fishing village in County Louth, Ireland. Located in a natural bay on the east coast it is bordered by the villages of Annagassan to the north and Termonfeckin to the south. It has a population of 2,145 according to the 2 ...

in County Louth. Ireland's crust (and sedimentary rocks) to the north-west of the suture originally derives from Laurentia (proto-North America), while the crust to the south-east is Avalonian ("European").

On the Isle of Man (Niarbyl Fault)

Iapetus Suture - Niarbyl Fault - Isle of Man - kingsley - 23-JUN-09

The Niarbyl Fault is an exposed section of the Iapetus Suture as it crosses through the

Irish Sea The Irish Sea or , gv, Y Keayn Yernagh, sco, Erse Sie, gd, Muir Èireann , Ulster-Scots: ''Airish Sea'', cy, Môr Iwerddon . is an extensive body of water that separates the islands of Ireland and Great Britain. It is linked to the Ce ...

. It is readily visible in present-day

Niarbyl 250px, View to the south across Niarbyl Bay of the southwest coastline of the Isle of Man and Calf of Man. Niarbyl ( glv, Yn Arbyl), meaning "the tail" in Manx for the way it extends into the Irish Sea, is a rocky promontory on the southwest c ...

on the southwest coast of

Isle of Man ) , anthem = "O Land of Our Birth" , image = Isle of Man by Sentinel-2.jpg , image_map = Europe-Isle_of_Man.svg , mapsize = , map_alt = Location of the Isle of Man in Europe , map_caption = Location of the Isle of Man (green) in Europe ...

. The fault is manifested by two major rock groups which abut each other, both deposited by their respective, aforementioned continents – the

Manx Group The Manx Group is an Ordovician lithostratigraphic group (a sequence of rock strata) in the Isle of Man in the Irish Sea. The name is derived from the name of the island which is largely formed from them; these rocks have also previously been ref ...

to the south-east and the

Dalby Group The Dalby Group is a Silurian lithostratigraphic group (a sequence of rock strata) on the west coast of the Isle of Man in the Irish Sea. The name is derived from the village of Dalby near the west coast of the island. Together with those of t ...

to the north-west. The Niarbyl fault is evidence of two paleocontinents colliding: Avalonia on which present-day

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

is located and Laurentia which contains both present-day North America and

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

. The fault is visible close to the shoreline downhill from the Niarbyl Cafe and Visitor Centre in Niarbyl.

In Great Britain

The Caledonian orogeny united the northern and southern portions of present-day

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It i ...

. The Iapetus Suture runs from the

Solway Firth The Solway Firth ( gd, Tràchd Romhra) is a firth that forms part of the border between England and Scotland, between Cumbria (including the Solway Plain) and Dumfries and Galloway. It stretches from St Bees Head, just south of Whitehaven ...

to Lindisfarne. The

Anglo-Scottish border The Anglo-Scottish border () is a border separating Scotland and England which runs for between Marshall Meadows Bay on the east coast and the Solway Firth in the west. The surrounding area is sometimes referred to as "the Borderlands". The ...

runs near and roughly parallel to the suture.

References

{{Reflist

External links

Animation by Manx Geological Survey

Niarbyl (Official Website of Manx National Heritage)
Historical oceans Silurian geology Geology of the United Kingdom Natural history of Europe Triple junctions Orogeny Suture zones