Rheic Ocean
Encyclopedia
The Rheic Ocean was a Paleozoic
ocean
between the large continent Gondwana
to the south and the microcontinents Avalonia
and others to the north. It formed during the Cambrian
and was destroyed during the Hercynian (European name) and Alleghenian
(North American name) orogenies
during the Carboniferous
.
and Baltica
. The Paleozoic ocean between Gondwana, Laurentia and Baltica is called the Iapetus Ocean
. The northern edge of Gondwana had been dominated by the Cadomian orogeny
during the Ediacaran
period. This orogeny formed a cordillera
-type volcanic arc
where oceanic crust
subducted below Gondwana. When a mid-oceanic ridge subducted
under an oblique angle, extensional basins
developed along the northern margin of Gondwana. During the late Cambrian
to Early Ordovician these extensional basins had evolved a rift
running along the northern edge of Gondwana. The rift in its turn evolved into a mid-oceanic ridge that separated small continental fragments such as Avalonia and Carolina from the main Gondwanan land mass.
Avalonia drifted north from Gondwana, the Rheic Ocean grew. The northward movement of Avalonia made the Iapetus Ocean
shrink during the Middle Ordovician to Late Silurian. For much of the Late Ordovician, the Rheic Ocean appears to have widened as fast as today's East Pacific Rise
(at 17 cm/year). Meanwhile, Avalonia
collided with Baltica
and Laurentia
in the Late Silurian to form Laurussia during the Caledonian orogeny
. The Rheic Ocean itself began to close in the Devonian
when Gondwana, probably preceded by terranes that had broken off, drifted towards Laurussia. By the Late Devonian
, the Rheic Ocean had become a narrow ocean that was then sutured
between Gondwana and Laurussia. The ocean closed from east to west, first in what is presently central Europe (the Hercynian orogeny), then the northeast of North America (Alleghenian orogeny) and northwest of Africa and finally in the southeast of North America (Ouachita orogeny
) and north of South America.
, in Greek mythology
the father of Atlas
, just as the Iapetus Ocean was the predecessor of the Atlantic Ocean
. The ocean between Gondwana and Baltica was then named Rheic Ocean for Rhea
, sister of Iapetus.
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
between the large continent Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
to the south and the microcontinents Avalonia
Avalonia
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, 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...
and others to the north. It formed during the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
and was destroyed during the Hercynian (European name) and Alleghenian
Alleghenian orogeny
The Alleghenian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957....
(North American name) orogenies
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
during the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
.
Geodynamic evolution
At the beginning of the Paleozoic Era, about 540 million years ago, most of the continental mass on Earth was clustered around the south pole as the paleocontinent Gondwana. The exception was formed by a number of smaller continents, such as LaurentiaLaurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
and Baltica
Baltica
Baltica is a name applied by geologists to a late-Proterozoic, early-Palaeozoic continent that now includes the East European craton of northwestern Eurasia. Baltica was created as an entity not earlier than 1.8 billion years ago. Before this time, the three segments/continents that now comprise...
. The Paleozoic ocean between Gondwana, Laurentia and Baltica is called the Iapetus Ocean
Iapetus Ocean
The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...
. The northern edge of Gondwana had been dominated by the Cadomian orogeny
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...
during the Ediacaran
Ediacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
period. This orogeny formed a cordillera
Cordillera
A cordillera is an extensive chain of mountains or mountain ranges, that runs along a coastline . It comes from the Spanish word cordilla, which is a diminutive of cuerda, or "cord"...
-type volcanic arc
Volcanic arc
A volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
where oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...
subducted below Gondwana. When a mid-oceanic ridge subducted
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
under an oblique angle, extensional basins
Extensional tectonics
Extensional tectonics is concerned with the structures formed, and the tectonic processes associated with, the stretching of the crust or lithosphere.-Deformation styles:...
developed along the northern margin of Gondwana. During the late Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
to Early Ordovician these extensional basins had evolved a rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
running along the northern edge of Gondwana. The rift in its turn evolved into a mid-oceanic ridge that separated small continental fragments such as Avalonia and Carolina from the main Gondwanan land mass.
Avalonia drifted north from Gondwana, the Rheic Ocean grew. The northward movement of Avalonia made the Iapetus Ocean
Iapetus Ocean
The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...
shrink during the Middle Ordovician to Late Silurian. For much of the Late Ordovician, the Rheic Ocean appears to have widened as fast as today's East Pacific Rise
East Pacific Rise
The East Pacific Rise is a mid-oceanic ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate...
(at 17 cm/year). Meanwhile, Avalonia
Avalonia
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, 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...
collided with Baltica
Baltica
Baltica is a name applied by geologists to a late-Proterozoic, early-Palaeozoic continent that now includes the East European craton of northwestern Eurasia. Baltica was created as an entity not earlier than 1.8 billion years ago. Before this time, the three segments/continents that now comprise...
and Laurentia
Laurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
in the Late Silurian to form Laurussia during the Caledonian orogeny
Caledonian orogeny
The Caledonian orogeny is 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 occurred from the Ordovician to Early Devonian, roughly...
. The Rheic Ocean itself began to close in the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
when Gondwana, probably preceded by terranes that had broken off, drifted towards Laurussia. By the Late Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
, the Rheic Ocean had become a narrow ocean that was then sutured
Suture (geology)
In structural geology, a suture is a major fault zone through an orogen or mountain range. Sutures separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories...
between Gondwana and Laurussia. The ocean closed from east to west, first in what is presently central Europe (the Hercynian orogeny), then the northeast of North America (Alleghenian orogeny) and northwest of Africa and finally in the southeast of North America (Ouachita orogeny
Ouachita orogeny
The Ouachita orogeny was a mountain building event that resulted in the folding and faulting of strata currently exposed in the Ouachita Mountains...
) and north of South America.
Name
The ocean between Baltica and Laurentia was named for IapetusIapetus (mythology)
In Greek mythology, Iapetus , also Iapetos or Japetus , was a Titan, the son of Uranus and Gaia, and father of Atlas, Prometheus, Epimetheus, and Menoetius and through Prometheus, Epimetheus and Atlas an ancestor of the human race...
, in Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
the father of Atlas
Atlas (mythology)
In Greek mythology, Atlas was the primordial Titan who supported the heavens. Although associated with various places, he became commonly identified with the Atlas Mountains in north-west Africa...
, just as the Iapetus Ocean was the predecessor of the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. The ocean between Gondwana and Baltica was then named Rheic Ocean for Rhea
Rhea (mythology)
Rhea was the Titaness daughter of Uranus, the sky, and Gaia, the earth, in Greek mythology. She was known as "the mother of gods". In earlier traditions, she was strongly associated with Gaia and Cybele, the Great Goddess, and was later seen by the classical Greeks as the mother of the Olympian...
, sister of Iapetus.
External links
- Website of the PALEOMAP Project
- Middle Silurian paleoglobe showing the expanding Rheic Ocean
- Early Carboniferous paleoglobe showing the almost disappeared Rheic Ocean