Geosyncline

Geosyncline originally called a geosynclinal[1] is an obsolete[2] geological concept to explain orogens which was developed in the late 19th and early 20th centuries before the theory of plate tectonics was envisaged. A geosyncline was described as a giant downward fold in Earth's crust with associated upward folds (geanticlines, geanticlinals) that preceded the climax phase of orogenic deformation.[1]

History

The geosyncline concept was first developed by the American geologists James Hall and James Dwight Dana in the mid-19th century during the classic studies of the Appalachian Mountains.[1][3] Émile Haug actualized the geosyncline concept and "reintroduced" it to Europe with a 1900 publication.[4][5] Eduard Suess, a leading geologist of his time, disapproved the concept of geosyncline and argued in 1909 against its use due to its associated theories.[5][6] This did not stop further developed of the concept by Leopold Kober and Hans Stille in the first half of the 20th century,[7] both of whom worked on a contracting Earth framework.[7] Stille and Kober had rather similar views.[8]

The development of the geosycline concept in the aftermath of Eduard Suess' book Das Antlitz der Erde (1883–1909) by Stille and Kober was not unchallenged as another school of thought was led by Alfred Wegener and Émile Argand.[7] This competing view rejected Earth contraction and argued for continental drift.[9] These two views can be called fixist in the case of geosyncline theory and mobilist for the support of continental drift.[10]

John F.Dewey and John M.Bird adapted the geosyncline concept to plate tectonics in 1970.[11] The term continued to have usage within a plate tectonics framework in the 1980s, albeit Celâl Şengör argued in 1982 against its use considering its association to pre-plate tectonics ideas.[6][12]

Kober–Stille school

As a geosyncline depression originated uplifted geanticlines were eroded providing sediments that filled the basin.[1] According to Stille geosynclines formed as depressions without any faulting and if faults were found these were the product of later processes like the final collapse of the geosyncline.[4] Collapse of geosynclines into orogens were thought by Dana and Stille to be the result of Earth's contraction over time.[5] In Stille's and Kober views geosynclines were together with orogens the unstable parts of Earth's crust in stark contrast with the very stable Kratogens.[8][13] In Stille's view geosynclines developed as result of contractional forces that also formed epeirogenic uplifts resulting in a pattern of undulation of Earth's crust. While this was according to him the common state of Earth episodic world-wide revolutions collapsed geosynclines into orogens.[13]

Steinmann interpreted ophiolites using the geosyncline concept. He theorized that the apparent lack of ophiolites in the Peruvian Andes was either indebted to the Andes being preceded by a shallow geosyncline or the Andes representing just the margin of a geosyncline.[14] Thus, Steinmann added this to a distintion between Cordilleran-type and Alpine-type mountains.[14] According to Stille a type of geosyncline called eugesynclines were characterized by producing an "initial magmatism" that in some cases corresponded to ophiolitic magmatism.[14]

Regarding oceans Kober held them to be strictly different to geosynclines.[15] Kober further held that mid-ocean ridges were orogens, while Stille disagreed showing that they, as seen in Iceland, were places of extensional tectonics.[8] Argand on the other side argued that geosynclines that stretched enough could turn into oceans basins as a material called sima surfaced.[15]

Hans Stille's classification[16][17][14]
Geosyncline typeGeosyncline subtypeAssociated magmatismResuting mountain type
Orthogeosyncline Eugeosyncline Initial magmatism Alpinotype
Miogeosyncline -
Parageosyncline - Germanotype
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References
  1. Şengör (1982), p. 11
  2. Selley, Richard C., Applied Sedimentology, Academic Press, 2nd edition, 2000, p. 486 ISBN 978-0-12-636375-3
  3. Adolph Knopf, The Geosynclinal Theory, Bulletin of the Geological Society of America 59:649-670, July 1948
  4. Şengör (1982), p. 25
  5. Şengör (1982), p. 26
  6. Şengör (1982), p. 43
  7. Şengör (1982), p. 23
  8. Şengör (1982), p. 28
  9. Şengör (1982), p. 24
  10. Şengör (1982), p. 30
  11. Dewey, John F.; Bird, John M. (1970). "Plate tectonics and geosynclines". Tectonophysics. 10 (5–6): 625–638. doi:10.1016/0040-1951(70)90050-8.
  12. Şengör (1982), p. 44
  13. Şengör (1982), p. 29
  14. Şengör & Natal'in (2004), p. 682
  15. Şengör (1982), p. 33
  16. Şengör (1982), p. 36
  17. Şengör (1982), p. 37

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.
  • Şengör, Celâl (1982). "Classical theories of orogenesis". In Miyashiro, Akiho; Aki, Keiiti; Şengör, Celâl (eds.). Orogeny. John Wiley & Sons. ISBN 0-471-103764.
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