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Orogeny (Greek for "mountain generating") is the process of mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within a time frame.
Orogenic events occur solely as a result of the processes of plate tectonics; the problems which were investigated and resolved by the study of orogenesis contributed greatly to the theory of plate tectonics, coupled with study of flora and fauna, geography and mid ocean ridges in the 1950s and 1960s.
The physical manifestations of orogenesis (the process of orogeny) are
orogenic belts or
orogens. An orogen is different from a mountain range in that an orogen may be completely
erosion away, and only recognizable by studying (old) rocks that bear the traces of the orogeny. Orogens are usually long, thin, arcuate tracts of rocks which have a pronounced linear structure resulting in
terranes or blocks of deformed rocks, separated generally by
Strike and dip thrust faults. These thrust faults carry relatively thin plates (which are called nappes, and differ from
tectonic plates) of rock in from the margins of the compressing orogen to the core, and are intimately associated with fold (geology) and the development of
metamorphism.
The topographic height of orogenic mountains is related to the principle of isostasy, where the
Newton's law of universal gravitation of the upthrust mountain range of light, continental crust material is balanced against its buoyancy relative to the dense
mantle (geology).
Erosion inevitably takes its course, removing much of the mountains, leaving the core or
mountain roots, which may be exhumed by further isostatic events balancing out the loss of elevated mass. This is the final form of the majority of old orogenic belts, being a long arcuate strip of crystalline metamorphic rocks sequentially below younger sediments which are thrust atop them and dip away from the orogenic core.
History
Before geology, the presence of mountains was explained in Christian contexts as a result of the Biblical Deluge, for Neoplatonic thought, which influenced early Christian writers, assumed that a perfect Creation would have to have been in the form of a perfect sphere. Such thinking persisted into the eighteenth century.
Orogeny was used by
Amanz Gressly (1840) and
Jules Thurmann (1854) as
orogenic in terms of the creation of mountain elevations, as the term
mountain building was still used to describe the processes.
Elie de Beaumont (1852) used the evocative "Jaws of a Vise" theory to explain orogeny, but was more concerned with the height rather than the implicit structures orogenic belts created and contained. His theory essentially held that mountains were created by the squeezing of certain rocks.
Eduard Suess (1875) recognised the importance of horizontal movement of rocks. The concept of a
precursor geosyncline or initial downward warping of the solid earth (Hall, 1859) prompted
James Dwight Dana (1873) to include the concept of
compression in the theories surrounding mountain-building. With hindsight, we can discount Dana's conjecture that this contraction was due to the cooling of the Earth (aka the
cooling earth theory).
The cooling Earth theory was the chief paradigm for most geologists until the 1960s. It was, in the context of orogeny, contested hotly by proponents of vertical movements in the crust (similar to
tephrotectonics), or convection within the asthenosphere or mantle (geology).
Gustav Steinmann (1906) recognised different classes of orogenic belts, including the
Alpine type orogenic belt, typified by a
flysch and molasse geometry to the sediments;
ophiolite sequences, tholeiitic basalts, and a
nappe style fold structure.
In terms of recognising orogeny as an
event,
Leopold von Buch (1855) recognised that orogenies could be placed in time by bracketing between the youngest deformed rock and the oldest undeformed rock, a principle which is still in use today, though commonly investigated by
geochronology using radiometric dating.
H.J. Zwart (1967) drew attention to the metamorphic differences in orogenic belts, proposing three types, modified by W. S. Pitcher (1979);
- Hercynotype (back-arc basin type);
- Shallow, low-pressure metamorphic rock; thin metamorphic zones
- Metamorphism dependent on increase in temperature
- Abundant granite and migmatite
- Few ophiolites, ultramafic rocks virtually absent
- very wide orogen with small and slow uplift
- nappe structures rare
- Alpinotype (ocean trench style);
- deep, high pressure, thick metamorphic zones
- metamorphism of many facies, dependent on decrease in pressure
- few granites or migmatites
- abundant ophiolites with ultramafic rocks
- Relatively narrow orogen with large and rapid uplift
- Nappe structures predominant
- Cordilleran (arc) type;
The advent of plate tectonics has explained the vast majority of orogenic belts and their features. The cooling earth theory (principally advanced by Descartes) is dispensed with, and tephrotectonic style vertical movements have been explained primarily by the process of isostasy.
Some oddities exist, where simple collisional tectonics are modified in a transform plate boundary, such as in New Zealand, or where island arc orogenies, for instance in
New Guinea occur away from a continental backstop. Further complications such as Proterozoic continent-continent collisional orogens, explicitly the
Musgrave Block in Australia, previously inexplicable (see Dennis, 1982) are being brought to light with the advent of seismic imaging techniques which can resolve the deep crust structure of orogenic belts.
Physiography
The process of orogeny can take tens of millions of years and build mountains from plains or even the
Seabed. Orogeny can occur due to
continental collision or
volcano. Frequently, rock formations that undergo orogeny are severely deformed and undergo
metamorphism. During orogeny, deeply buried rocks may be pushed to the surface. Sea bottom and near shore material may cover some or all of the orogenic area. If the orogeny is due to two continents colliding, the resulting mountains can be very high (see
Himalaya).
Orogeny usually produces long linear structures, known as
orogenic belts. Generally, orogenic belts consist of long parallel strips of
Rock (geology) exhibiting similar characteristics along the length of the belt. Orogenic belts are associated with
subduction zones, which consume
crust (geology), produce volcanoes, and build island arcs. These island arcs may be added to a
continent during an orogenic event.
List of orogenies
North American orogenies
- Caledonian orogeny
- the Taconic orogeny in the NE U.S. and Canada during the Ordovician Period.
- the Acadian orogeny in the Eastern U.S. during Silurian and Devonian Geologic periods.
- Antler orogeny
- Ancestral Sierra Nevada (U.S.) western United States.
- Appalachian orogeny, usually seen as the same as the Variscan orogeny in Europe.
- Big Sky orogeny
- Grenville orogeny
- Worldwide during the late Proterozoic, 1300-1000 mya. Associated with the assembly of the supercontinent Rodinia. Formed folded mountains in Eastern North America from Newfoundland and Labrador to North Carolina, 1100-1000 mya.
- Mazatzal orogeny US mid to south western circa 1600 mya
- Laramide orogeny
- Nevadan orogeny
- developed along western North America during the Jurassic Period.
- Ouachita orogeny
- Penokean orogeny
- Wisconsin, Minnesota, and Michigan, U. S. A. and southern Ontario, Canada, 1900 Myr ago.
- Sevier orogeny
- Rocky Mountains, western North America, 140 - 50 million years ago.
- Sonoma orogeny
- Rocky Mountains, western North America, 270 - 240 million years ago
- Trans-Hudsonian orogeny
- Extends from Hudson Bay west into Saskatchewan then south through the western Dakotas and Nebraska. Result of the collision of the Superior craton with the Hearne craton and the Wyoming craton during the Proterozoic.
European orogenies
Asian orogenies
South American orogenies
- Andean orogeny
- Andes Mountains, 0-200 Myr ago.
African orogenies
Australian orogenies
- Sleaford Orogeny (2440-2420 Ma), Gawler Craton, South Australia
- Glenburgh Orogeny (c. 2005 - 1920 Ma), Glenburgh Terrane, Western Australia.
- Kimban Orogeny (c. 1845-1700 Ma), Gawler Craton, South Australia
- Yapungku Orogeny (c. 1700 Ma), North Yilgarn craton margin, Western Australia
- Mangaroon Orogeny (c.1680 - 1620 Ma), Gascoyne Complex, Western Australia.
- Kararan Orogeny (1650- Ma), Gawler Craton, South Australia
- Barramundi Orogeny (c. 1600 Ma), MacArthur Basin, northern Australia
- Isan Orogeny, c. 1600 Ma, Mount Isa, Queensland Block, Queensland
- Olarian Orogeny, Olary Block, South Australia
- Capricorn Orogeny, Gascoyne Complex, Western Australia
- Musgrave Orogeny (c. 1080 Ma), Musgrave Block, Central Australia.
- Edmundian Orogeny (c. 920 - 850 Ma), Gascoyne Complex, Western Australia.
- Petermann Orogeny (c. 550-535 Ma late Neoproterozoic to Cambrian), Central Australia
- Delamerian Orogeny, South Australia and Victoria (Australia), Australia, Ordovician
- Lachlan Orogeny, c. 540 and 440 Ma., Victoria (Australia) and New South Wales
- Alice Springs Orogeny in central Australia, Early Carboniferous
- Hunter-Bowen orogeny, (c. 260 - 225 Ma) Permian to Triassic, Queensland and New South Wales
Antarctic orogenies
- Napier orogeny (4000 ± 200 Myr ago.)
- Rayner orogeny (~ 3500 Myr ago.)
- Humboldt orogeny (~ 3000 Myr ago.)
- Insel orogeny (2650 ± 150 Myr ago.)
- Early Ruker orogeny (2000 - 1700 Myr ago.)
- Late Ruker / Nimrod orogeny (1000 ± 150 Myr ago.)
- Beardmore orogeny (633 - 620 Myr ago.)
- Ross Orogeny (~ 500 Myr ago.)
New Zealand orogenies
- Tuhua Orogeny (370 to 330 Myr ago)
- Rangitata Orogeny (142 to 99 million years ago)
- Kaikoura Orogeny (24 million years ago to present day)
See also
- Continental collision
- Plate tectonics
References
- Jean-Baptiste Élie de Beaumont, 1852. Notice sur les Systèmes de Montagnes ("Note on Mountain Systems"), Bertrand, Paris, 1543 pp. (English synopsis in Dennis (1982))
- Buch, L. Von, 1902. Gesammelte Schriften, Roth & Eck, Berlin.
- Dana, James D., 1873. On some results of the Earth's contraction from cooling, including a discussion of the origins of mountains, and the nature of the Earth's interior. American Journal of Science, 5, pp. 423-443.
- Dennis, John G., 1982. Orogeny, Benchmark Papers in Geology, Volume 62, Hutchinson Ross Pulishing Company, New York ISBN 0-87933-394-4
- Hall, J., 1859. Palaeontology of New York, in New York National Survey No. 3, Part 1, 533 p.
- Suess, Eduard, 1875. Die Entstehung Der Alpen lit. The Origin Of The Alps, Braumüller, Vienna, 168 p.
- Harms, Brady, Cheney, 2006. "EXPLORING THE PROTEROZOIC BIG SKY OROGENY IN SOUTHWEST MONTANA", 19th annual Keck symposium.
External links
- Maps of the Acadian and Taconic orogenies
- Antarctic Geology
Orogeny (Greek for "mountain generating") is the process of
mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within a time frame.
Orogenic events occur solely as a result of the processes of
plate tectonics; the problems which were investigated and resolved by the study of orogenesis contributed greatly to the theory of plate tectonics, coupled with study of flora and fauna, geography and mid ocean ridges in the 1950s and 1960s.
The physical manifestations of orogenesis (the process of orogeny) are
orogenic belts or
orogens. An orogen is different from a mountain range in that an orogen may be completely erosion away, and only recognizable by studying (old) rocks that bear the traces of the orogeny. Orogens are usually long, thin, arcuate tracts of rocks which have a pronounced linear structure resulting in terranes or blocks of deformed rocks, separated generally by
Strike and dip thrust faults. These thrust faults carry relatively thin plates (which are called nappes, and differ from
tectonic plates) of rock in from the margins of the compressing orogen to the core, and are intimately associated with
fold (geology) and the development of metamorphism.
The topographic height of orogenic mountains is related to the principle of
isostasy, where the Newton's law of universal gravitation of the upthrust mountain range of light, continental crust material is balanced against its buoyancy relative to the dense
mantle (geology).
Erosion inevitably takes its course, removing much of the mountains, leaving the core or
mountain roots, which may be exhumed by further isostatic events balancing out the loss of elevated mass. This is the final form of the majority of old orogenic belts, being a long arcuate strip of crystalline metamorphic rocks sequentially below younger sediments which are thrust atop them and dip away from the orogenic core.
History
Before geology, the presence of mountains was explained in Christian contexts as a result of the Biblical Deluge, for
Neoplatonic thought, which influenced early Christian writers, assumed that a perfect Creation would have to have been in the form of a perfect sphere. Such thinking persisted into the eighteenth century.
Orogeny was used by Amanz Gressly (1840) and Jules Thurmann (1854) as
orogenic in terms of the creation of mountain elevations, as the term
mountain building was still used to describe the processes.
Elie de Beaumont (1852) used the evocative "Jaws of a Vise" theory to explain orogeny, but was more concerned with the height rather than the implicit structures orogenic belts created and contained. His theory essentially held that mountains were created by the squeezing of certain rocks.
Eduard Suess (1875) recognised the importance of horizontal movement of rocks. The concept of a
precursor geosyncline or initial downward warping of the solid earth (Hall, 1859) prompted
James Dwight Dana (1873) to include the concept of
compression in the theories surrounding mountain-building. With hindsight, we can discount Dana's conjecture that this contraction was due to the cooling of the Earth (aka the
cooling earth theory).
The cooling Earth theory was the chief paradigm for most geologists until the 1960s. It was, in the context of orogeny, contested hotly by proponents of vertical movements in the crust (similar to tephrotectonics), or convection within the asthenosphere or mantle (geology).
Gustav Steinmann (1906) recognised different classes of orogenic belts, including the
Alpine type orogenic belt, typified by a
flysch and molasse geometry to the sediments; ophiolite sequences,
tholeiitic basalts, and a nappe style fold structure.
In terms of recognising orogeny as an
event,
Leopold von Buch (1855) recognised that orogenies could be placed in time by bracketing between the youngest deformed rock and the oldest undeformed rock, a principle which is still in use today, though commonly investigated by geochronology using radiometric dating.
H.J. Zwart (1967) drew attention to the metamorphic differences in orogenic belts, proposing three types, modified by W. S. Pitcher (1979);
- Hercynotype (back-arc basin type);
- Shallow, low-pressure metamorphic rock; thin metamorphic zones
- Metamorphism dependent on increase in temperature
- Abundant granite and migmatite
- Few ophiolites, ultramafic rocks virtually absent
- very wide orogen with small and slow uplift
- nappe structures rare
- Alpinotype (ocean trench style);
- deep, high pressure, thick metamorphic zones
- metamorphism of many facies, dependent on decrease in pressure
- few granites or migmatites
- abundant ophiolites with ultramafic rocks
- Relatively narrow orogen with large and rapid uplift
- Nappe structures predominant
- Cordilleran (arc) type;
The advent of plate tectonics has explained the vast majority of orogenic belts and their features. The cooling earth theory (principally advanced by Descartes) is dispensed with, and tephrotectonic style vertical movements have been explained primarily by the process of isostasy.
Some oddities exist, where simple collisional tectonics are modified in a transform plate boundary, such as in New Zealand, or where island arc orogenies, for instance in
New Guinea occur away from a continental backstop. Further complications such as Proterozoic continent-continent collisional orogens, explicitly the
Musgrave Block in Australia, previously inexplicable (see Dennis, 1982) are being brought to light with the advent of seismic imaging techniques which can resolve the deep crust structure of orogenic belts.
Physiography
The process of orogeny can take tens of millions of years and build mountains from plains or even the Seabed. Orogeny can occur due to continental collision or
volcano. Frequently, rock formations that undergo orogeny are severely deformed and undergo
metamorphism. During orogeny, deeply buried rocks may be pushed to the surface. Sea bottom and near shore material may cover some or all of the orogenic area. If the orogeny is due to two continents colliding, the resulting mountains can be very high (see Himalaya).
Orogeny usually produces long linear structures, known as
orogenic belts. Generally, orogenic belts consist of long parallel strips of Rock (geology) exhibiting similar characteristics along the length of the belt. Orogenic belts are associated with subduction zones, which consume
crust (geology), produce volcanoes, and build island arcs. These island arcs may be added to a continent during an orogenic event.
List of orogenies
North American orogenies
- Caledonian orogeny
- Antler orogeny
- Appalachian orogeny, usually seen as the same as the Variscan orogeny in Europe.
- Appalachian Mountains is a well studied orogenic belt resulting from a late Paleozoic collision between North America and Africa.
- Taconic orogeny
- Acadian orogeny
- Alleghenian orogeny
- Big Sky orogeny
- Proterozoic (1.77 Ga) collision between the Hearne craton and the Wyoming craton in southwest Montana.
- Grenville orogeny
- Mazatzal orogeny US mid to south western circa 1600 mya
- Laramide orogeny
- Nevadan orogeny
- developed along western North America during the Jurassic Period.
- Ouachita orogeny
- Ouachita Mountains of Arkansas and Oklahoma is an orogenic belt that dates from the late Paleozoic Era (geology) and is most likely a continuation of the Appalachian orogeny west across the Mississippi embayment - Reelfoot Rift zone.
- Penokean orogeny
- Wisconsin, Minnesota, and Michigan, U. S. A. and southern Ontario, Canada, 1900 Myr ago.
- Sevier orogeny
- Rocky Mountains, western North America, 140 - 50 million years ago.
- Sonoma orogeny
- Rocky Mountains, western North America, 270 - 240 million years ago
- Trans-Hudsonian orogeny
- Extends from Hudson Bay west into Saskatchewan then south through the western Dakotas and Nebraska. Result of the collision of the Superior craton with the Hearne craton and the Wyoming craton during the Proterozoic.
European orogenies
- The Caledonian orogeny
- Formation of the highlands of west Norway, Great Britain and Ireland in the Silurian Period.
- Uralian orogeny
- Formation of the Ural Mountains, Eurasia, during the Permian Period.
- The Variscan orogeny (also called the Hercynian orogeny)
- The Alpine orogeny, encompassing:
- Ongoing (happening now):
Asian orogenies
- The Aravalli-Delhi Orogen (precambrian)
- The Cimmerian orogeny and Cathayasian orogeny orogenies
- Alpine orogeny, encompassing:
- The Geology of the Himalaya, forming the Himalaya, as a result of the ongoing collision of the Indian Plate with the Eurasian Plate.
South American orogenies
African orogenies
Australian orogenies
- Sleaford Orogeny (2440-2420 Ma), Gawler Craton, South Australia
- Glenburgh Orogeny (c. 2005 - 1920 Ma), Glenburgh Terrane, Western Australia.
- Kimban Orogeny (c. 1845-1700 Ma), Gawler Craton, South Australia
- Yapungku Orogeny (c. 1700 Ma), North Yilgarn craton margin, Western Australia
- Mangaroon Orogeny (c.1680 - 1620 Ma), Gascoyne Complex, Western Australia.
- Kararan Orogeny (1650- Ma), Gawler Craton, South Australia
- Barramundi Orogeny (c. 1600 Ma), MacArthur Basin, northern Australia
- Isan Orogeny, c. 1600 Ma, Mount Isa, Queensland Block, Queensland
- Olarian Orogeny, Olary Block, South Australia
- Capricorn Orogeny, Gascoyne Complex, Western Australia
- Musgrave Orogeny (c. 1080 Ma), Musgrave Block, Central Australia.
- Edmundian Orogeny (c. 920 - 850 Ma), Gascoyne Complex, Western Australia.
- Petermann Orogeny (c. 550-535 Ma late Neoproterozoic to Cambrian), Central Australia
- Delamerian Orogeny, South Australia and Victoria (Australia), Australia, Ordovician
- Lachlan Orogeny, c. 540 and 440 Ma., Victoria (Australia) and New South Wales
- Alice Springs Orogeny in central Australia, Early Carboniferous
- Hunter-Bowen orogeny, (c. 260 - 225 Ma) Permian to Triassic, Queensland and New South Wales
Antarctic orogenies
- Napier orogeny (4000 ± 200 Myr ago.)
- Rayner orogeny (~ 3500 Myr ago.)
- Humboldt orogeny (~ 3000 Myr ago.)
- Insel orogeny (2650 ± 150 Myr ago.)
- Early Ruker orogeny (2000 - 1700 Myr ago.)
- Late Ruker / Nimrod orogeny (1000 ± 150 Myr ago.)
- Beardmore orogeny (633 - 620 Myr ago.)
- Ross Orogeny (~ 500 Myr ago.)
New Zealand orogenies
See also
References
- Jean-Baptiste Élie de Beaumont, 1852. Notice sur les Systèmes de Montagnes ("Note on Mountain Systems"), Bertrand, Paris, 1543 pp. (English synopsis in Dennis (1982))
- Buch, L. Von, 1902. Gesammelte Schriften, Roth & Eck, Berlin.
- Dana, James D., 1873. On some results of the Earth's contraction from cooling, including a discussion of the origins of mountains, and the nature of the Earth's interior. American Journal of Science, 5, pp. 423-443.
- Dennis, John G., 1982. Orogeny, Benchmark Papers in Geology, Volume 62, Hutchinson Ross Pulishing Company, New York ISBN 0-87933-394-4
- Hall, J., 1859. Palaeontology of New York, in New York National Survey No. 3, Part 1, 533 p.
- Suess, Eduard, 1875. Die Entstehung Der Alpen lit. The Origin Of The Alps, Braumüller, Vienna, 168 p.
- Harms, Brady, Cheney, 2006. "EXPLORING THE PROTEROZOIC BIG SKY OROGENY IN SOUTHWEST MONTANA", 19th annual Keck symposium.
External links
- Maps of the Acadian and Taconic orogenies
- Antarctic Geology
Orogeny - Wikipedia, the free encyclopedia
Orogeny (Greek for "mountain generating") is the process of natural mountain building, and may be studied as a tectonic structural event, as a geographical event and a ...
Caledonian orogeny - Wikipedia, the free encyclopedia
The Caledonian orogeny is a mountain building event recorded in the mountains and hills of northern Scotland, Ireland, England, Wales, and west Norway.
Grampian Orogeny Shetland
geological map. Lewisian. Moine. Dalradian. Caledonian Orogeny. Devonian. Regional background. Grampian Orogeny. A recent evaluation of the Shetland ophiolite does not regard it to ...
Caledonian Orogeny Shetland
geological map. Lewisian. Moine. Grampian Orogeny. Dalradian. Devonian. geological evolution : Caledonian Orogeny. The Caledonian Orogeny encompasses the final closure of ...
orogeny - Wiktionary
Definition from Wiktionary, a free dictionary
orogeny - definition of orogeny by the Free Online Dictionary ...
The process of mountain formation, especially by a folding and faulting of the earth's crust.
orogeny - Hutchinson encyclopedia article about orogeny
orogenesis. In its original, literal sense, orogenesis means ‘mountain building’, but today it more specifically refers to the tectonics of mountain building (as opposed to ...
Laramide orogeny definition of Laramide orogeny in the Free Online ...
Laramide orogeny. Series of mountain-building events that affected much of western North America in Late Cretaceous and Early Tertiary time (c. 65 million years ago).
orogeny -- Britannica Online Encyclopedia
Britannica online encyclopedia article on orogeny:mountain-building event, generally one that occurs in geosynclinal areas. In contrast to epeirogeny, an orogeny tends to occur ...
The Caledonian Orogeny redefined
Journal of the Geological Society , London , Vol. 157 , 2000, pp. 1149-1154. Printed in Great Britain. The Caledonian Orogeny redefined W. S. McKERROW 1, C.