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A geosyncline (originally called a geosynclinal) is an obsolete
geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other E ...
concept to explain orogens, which was developed in the late 19th and early 20th centuries, before the theory of
plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
was envisaged. Şengör (1982), p. 11 A geosyncline was described as a giant downward fold in the
Earth's crust Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
, with associated upward folds called geanticlines (or geanticlinals), that preceded the climax phase of orogenic deformation.


History

The geosyncline concept was first conceived by the American geologists James Hall and
James Dwight Dana James Dwight Dana FRS FRSE (February 12, 1813 – April 14, 1895) was an American geologist, mineralogist, volcanologist, and zoologist. He made pioneering studies of mountain-building, volcanic activity, and the origin and structure of continent ...
in the mid-19th century, during the classic studies of the
Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. The ...
. Émile Haug further developed the geosyncline concept, and introduced it to Europe in 1900. Şengör (1982), p. 26 Eduard Suess, a leading geologist of his time, disapproved the concept of geosyncline, and in 1909 he argued against its use due to its association with outdated theories. Şengör (1982), p. 43 This did not prevent further development of the concept in the first half of the 20th century by Leopold Kober and
Hans Stille Hans Wilhelm Stille (8 October 1876 – 26 December 1966) was an influential German geologist working primarily on tectonics and the collation of tectonic events during the Phanerozoic. Stille adhered to the contracting Earth hypothesis A ...
, both of whom worked on a contracting Earth framework. Şengör (1982), p. 23 The continued development of the geosyncline theory by Stille and Kober following the publication of
Eduard Suess Eduard Suess (; 20 August 1831 - 26 April 1914) was an Austrian geologist and an expert on the geography of the Alps. He is responsible for hypothesising two major former geographical features, the supercontinent Gondwana (proposed in 1861) and t ...
' ''Das Antlitz der Erde'' from 1885 to 1909 was not unchallenged, as another school of thought was led by
Alfred Wegener Alfred Lothar Wegener (; ; 1 November 1880 – November 1930) was a German climatologist, geologist, geophysicist, meteorologist, and polar researcher. During his lifetime he was primarily known for his achievements in meteorology and ...
and
Émile Argand Émile Argand (6 January 1879 – 14 September 1940) was a Swiss geologist. He was born in Eaux-Vives near Geneva. He attended vocational school in Geneva then worked as a draftsman. He studied anatomy in Paris, but gave up medicine to pursue his ...
. This competing view rejected the premise of planetary contraction, and argued that orogeny was the result of
continental drift Continental drift is the hypothesis that the Earth's continents have moved over geologic time relative to each other, thus appearing to have "drifted" across the ocean bed. The idea of continental drift has been subsumed into the science of pl ...
. Şengör (1982), p. 24 These two views can be called "fixist", in the case of geosyncline theory, and "mobilist" for the support of continental drift. Şengör (1982), p. 30 Even as continental drift became generally accepted, the concept of geosynclines persisted in geological science. In 1970, John F. Dewey and John M. Bird adapted the geosyncline to plate tectonics. The term continued to have usage within a
plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
framework in the 1980s, although as early as 1982,
Celâl Şengör Ali Mehmet Celâl Şengör (born 24 March 1955) is a Turkish geologist. He is currently on the faculty at Istanbul Technical University, Department of Geological Engineering. Şengör is a (foreign) member of the American Philosophical Society ...
argued against its use, in light of its association with discredited geological ideas. Şengör (1982), p. 44


Geosynclinal theory

Dana and Stille supposed that the collapse of geosynclines into orogens was result of the Earth's contraction over time. In Stille and Kober's view, geosynclines and orogens were the unstable parts of the Earth's crust, in stark contrast with the very stable kratogens. Şengör (1982), p. 28 Şengör (1982), p. 29 Stille theorized that the contractional forces responsible for geosynclines also formed epeirogenic uplifts, resulting in a pattern of undulation in the Earth's crust. According to this view, regular, episodic global revolutions caused geosynclines to collapse, forming orogens. According to Kober and Stille, developing geosynclinal depressions were accompanied by uplifted geanticlines, which then
eroded Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is disti ...
, providing
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...
s that filled the geosynclinal basin. According to Stille, geosynclines were formed from crustal folding rather than
faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
; if faults were present in geosynclines, they were the product of later processes, such as the final collapse of the geosyncline. Şengör (1982), p. 25
Gustav Steinmann Johann Heinrich Conrad Gottfried Gustav Steinmann (9 April 1856 – 7 October 1929) was a German geologist and paleontologist. He performed various studies in the Ural Mountains, North America, South America, the Caucasus and the Alp ...
interpreted
ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found ...
s using the geosyncline concept. He theorized that the apparent lack of ophiolite in the Peruvian
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
was indebted either to the Andes being preceded by a shallow geosyncline, or because the Andes represented just the margin of a geosyncline. Steinmann contributed this correlation to the distinction between Cordilleran and Alpine-type mountains. According to Stille, a type of geosyncline called a "eugeosyncline" was characterized by producing an "initial magmatism", which in some cases corresponded to ophiolitic magmatism. With respect to oceanic basins, Kober held them to be separate and distinct from geosynclines. Şengör (1982), p. 33 He nonetheless believed that
mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a div ...
s were orogens, although Stille disagreed, asserting that they were places of
extensional tectonics Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend ...
, as exemplified by
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...
. Meanwhile, Argand argued that geosynclines, sufficiently attenuated through stretching, could become oceans basins, as a material called "
sima Sima or SIMA may refer to: People * Sima (Chinese surname) * Sima (given name), a Persian feminine name in use in Iran and Turkey * Sima (surname) Places * Sima, Comoros, on the island of Anjouan, near Madagascar * Sima de los Huesos, a cav ...
" surfaced.


See also

* * *


References


Bibliography

* King, Philip B. (1977) ''The Evolution of North America'', Revised edition, Princeton University Press, pp 54–58 * Kay, Marshall (1951) ''North American Geosyncline: Geol. Soc. America Mem. 48'', 143pp. *


External links

{{Authority control Obsolete geology theories