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Phanerozoic Tethys region (view source)
Revision as of 23:41, 17 February 2016
, 23:41, 17 February 2016no edit summary
[[file:M106Ch01Fig04.jpg|thumb|300px|{{figure number|4}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Early Devonian time (about 400 Ma).]]
[[file:M106Ch01Fig04.jpg|thumb|300px|{{figure number|4}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Early Devonian time (about 400 Ma).]]
===Early Devonian (about 400Ma)===
===Early Devonian (about 400 Ma)===
During Early Devonian time Gondwana was centered on the Southern Pole, with northern Africa and Antarctica located toward the equator ([[:file:M106Ch01Fig04.jpg|Figure 4]]). The continental plates that would form future Laurasia were located immediately to the south of the equator, so that most of the continental masses were in the southern hemisphere. The Iapetus Ocean had been closed by the collision between North America and Baltica, giving rise to the Caledonian orogeny. The Avalonia Ocean between southern England and Scotland was still present, and other minor oceanic seaways separated different blocks. These blocks would later form the components of Europe, assembled during the Carboniferous Variscan orogeny, with the closure of the Rheic Ocean. The width of the Rheic Ocean is still questioned, but the paleobiogeographic distribution of different groups of fossil organisms between Laurasia and Gondwana suggests that this ocean was relatively narrow during Early Devonian.<ref name=Wehrmannetal_2010>Wehrmann, A. et al., 2010, Devonian shallow-water sequences from the North Gondwana coastal margin (central and eastern Taurides, Turkey): Sedimentology, facies and global events: Gondwana Research, v. 17, p. 546–560.</ref> The Paleo-Tethys Ocean was opening along northern Gondwana, generating a fringe of microplates (e.g., Armorica, Adria, Pontides, Hellenic, and Moesia terranes). We follow the interpretation of Torsvik and Cocks,<ref name=Torsvikandcocks_2004>Torsvik, T. H., and Cocks, L. R. M., 2004, Earth geography from 400 to 250 Ma: A palaeomagnetic, faunal and facies review: Journal of the GSL v. 161, p. 555–572.</ref> who considered Adria and Apulia as separate microplates split apart by the opening of Paleo-Tethys. The width of the Paleo-Tethys Ocean at this time is still a matter of discussion. According to Robardet et al.,<ref name=Robardetetal_1990>Robardet, M., Paris, F., and Racheboeuf, P. R., 1990, Palaeogeographic evolution of southwestern Europe during Early Palaeozoic times, in W. S. McKerrow and C. R. Scotese, eds., Palaeozoic palaeogeography and biogeography: GSL Memoirs 12, p. 411–419.</ref> the detachment of Armorica from Gondwana is not older than Late Devonian, and Robardet<ref name=Robardet_2003 /> considers a fiction even the concept of an Armorica microplate. Other reconstructions<ref name=Stampfliandborel_2002 /> <ref name=Torsvikandcocks_2004 /> <ref name=Vonraumerandstampfli_2008 /> suggest that the opening of the Paleo-Tethys occurred before Early Devonian, and this is more certain for the eastward extension of this ocean.<ref name=Metcalfe_2002>Metcalfe, I., 2002, Tectonic history of the SE Asian-Australian region: Advances in Geoecology, v. 34, p. 29–48.</ref> Besides the strongly debated concepts of Armorica (e.g., Cocks and Torsvik,<ref name=Cocksandtorsvik_2002 /> Nysæther et al.,<ref name=Nysætheretal_2002 /> Robardet,<ref name=Robardet_2003 /> Torsvik and Cocks<ref name=Torsvikandcocks_2009 />), also the relative position of the microplates detached from Gondwana with the opening of the Paleo-Tethys differs in several reconstructions: Stampfli and Borel<ref name=Stampfliandborel_2002 /> and von Raumer and Stampfli<ref name=Vonraumerandstampfli_2008 /> identify a major continental block (Hun superterrane), whereas Torsvik and Cocks<ref name=Torsvikandcocks_2004 /> suggest the presence of different independent microplates. In fact, the separation of these various microplates may have been diachronous.
During Early Devonian time Gondwana was centered on the Southern Pole, with northern Africa and Antarctica located toward the equator ([[:file:M106Ch01Fig04.jpg|Figure 4]]). The continental plates that would form future Laurasia were located immediately to the south of the equator, so that most of the continental masses were in the southern hemisphere. The Iapetus Ocean had been closed by the collision between North America and Baltica, giving rise to the Caledonian orogeny. The Avalonia Ocean between southern England and Scotland was still present, and other minor oceanic seaways separated different blocks. These blocks would later form the components of Europe, assembled during the Carboniferous Variscan orogeny, with the closure of the Rheic Ocean. The width of the Rheic Ocean is still questioned, but the paleobiogeographic distribution of different groups of fossil organisms between Laurasia and Gondwana suggests that this ocean was relatively narrow during Early Devonian.<ref name=Wehrmannetal_2010>Wehrmann, A. et al., 2010, Devonian shallow-water sequences from the North Gondwana coastal margin (central and eastern Taurides, Turkey): Sedimentology, facies and global events: Gondwana Research, v. 17, p. 546–560.</ref> The Paleo-Tethys Ocean was opening along northern Gondwana, generating a fringe of microplates (e.g., Armorica, Adria, Pontides, Hellenic, and Moesia terranes). We follow the interpretation of Torsvik and Cocks,<ref name=Torsvikandcocks_2004>Torsvik, T. H., and Cocks, L. R. M., 2004, Earth geography from 400 to 250 Ma: A palaeomagnetic, faunal and facies review: Journal of the GSL v. 161, p. 555–572.</ref> who considered Adria and Apulia as separate microplates split apart by the opening of Paleo-Tethys. The width of the Paleo-Tethys Ocean at this time is still a matter of discussion. According to Robardet et al.,<ref name=Robardetetal_1990>Robardet, M., Paris, F., and Racheboeuf, P. R., 1990, Palaeogeographic evolution of southwestern Europe during Early Palaeozoic times, in W. S. McKerrow and C. R. Scotese, eds., Palaeozoic palaeogeography and biogeography: GSL Memoirs 12, p. 411–419.</ref> the detachment of Armorica from Gondwana is not older than Late Devonian, and Robardet<ref name=Robardet_2003 /> considers a fiction even the concept of an Armorica microplate. Other reconstructions<ref name=Stampfliandborel_2002 /> <ref name=Torsvikandcocks_2004 /> <ref name=Vonraumerandstampfli_2008 /> suggest that the opening of the Paleo-Tethys occurred before Early Devonian, and this is more certain for the eastward extension of this ocean.<ref name=Metcalfe_2002>Metcalfe, I., 2002, Tectonic history of the SE Asian-Australian region: Advances in Geoecology, v. 34, p. 29–48.</ref> Besides the strongly debated concepts of Armorica (e.g., Cocks and Torsvik,<ref name=Cocksandtorsvik_2002 /> Nysæther et al.,<ref name=Nysætheretal_2002 /> Robardet,<ref name=Robardet_2003 /> Torsvik and Cocks<ref name=Torsvikandcocks_2009 />), also the relative position of the microplates detached from Gondwana with the opening of the Paleo-Tethys differs in several reconstructions: Stampfli and Borel<ref name=Stampfliandborel_2002 /> and von Raumer and Stampfli<ref name=Vonraumerandstampfli_2008 /> identify a major continental block (Hun superterrane), whereas Torsvik and Cocks<ref name=Torsvikandcocks_2004 /> suggest the presence of different independent microplates. In fact, the separation of these various microplates may have been diachronous.
Most of the Asian terranes, mainly located immediately north of the equator, were still separated by seaways before their collision with and incorporation into Pangea. The position and vergence of subduction among these blocks is not clear, and different models have been proposed (e.g., Stampfli and Borel,<ref name=Stampfliandborel_2002 /> Torsvik and Cocks,<ref name=Torsvikandcocks_2004 /> Ruban et al.,<ref name=Rubanetal_2007 /> von Raumer and Stampfli<ref name=Vonraumerandstampfli_2008 />).
Most of the Asian terranes, mainly located immediately north of the equator, were still separated by seaways before their collision with and incorporation into Pangea. The position and vergence of subduction among these blocks is not clear, and different models have been proposed (e.g., Stampfli and Borel,<ref name=Stampfliandborel_2002 /> Torsvik and Cocks,<ref name=Torsvikandcocks_2004 /> Ruban et al.,<ref name=Rubanetal_2007 /> von Raumer and Stampfli<ref name=Vonraumerandstampfli_2008 />).
During Early Devonian time, a global sea-level fall was responsible for the reduction of the neritic belts. The occurrence of a wide depositional hiatus close to the Early Devonian in most of the Middle East is ascribed to this sea-level low-stand, probably enhanced by a tectonic uplift.<ref name=Rubanetal_2007 />. The middle latitude position of North Africa and part of Arabia favored the development of alluvial deposits. Tectonic activity was weak and limited volcanic flows are documented<ref name=Meneissy_1990>Metcalfe, I., 2002, Tectonic history of the SE Asian-Australian region: Advances in Geoecology, v. 34, p. 29–48.</ref> mainly in Sudan and in the southern area of the Eastern Desert of Egypt.<ref name=Schandelmeierandreynolds_1997 />
During Early Devonian time, a global sea-level fall was responsible for the reduction of the neritic belts. The occurrence of a wide depositional hiatus close to the Early Devonian in most of the Middle East is ascribed to this sea-level low-stand, probably enhanced by a tectonic uplift.<ref name=Rubanetal_2007 />. The middle latitude position of North Africa and part of Arabia favored the development of alluvial deposits. Tectonic activity was weak and limited volcanic flows are documented<ref name=Meneissy_1990>Meneissy, M. Y., 1990, Vulcanicity, in R. Said, ed., The Geology of Egypt: Balkema, Rotterdam, p. 157–172.</ref> mainly in Sudan and in the southern area of the Eastern Desert of Egypt.<ref name=Schandelmeierandreynolds_1997 />
[[file:M106Ch01Fig05.jpg|thumb|300px|{{figure number|5}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Early Permian time (about 290 Ma).]]
===Early Permian (about 290 Ma)===
The late Paleozoic was a period of major plate tectonic reconfiguration ([[:file:M106Ch01Fig05.jpg|Figure 5]]). The Variscan orogeny led to the assembly of Gondwana and Laurasia into one supercontinent, Pangea. Adria and Apulia, previously separated, are from here onward assembled as a microplate that is referred to as Adria in the Early Permian and subsequent maps. The opening of the Neo-Tethys Ocean along the eastern margin of Gondwana, from Arabia to Australia, created the Cimmerian terranes (Iran, Central Afghanistan, Karakorum, Qiangtang). These migrated northward across the Tethys Ocean from southern Gondwanan paleolatitudes in Early Permian time to subequatorial paleolatitudes by the ~Middle Permian–Early Triassic times (e.g., Sengör<ref name=Sengör_1979>Sengör, A. M. C., 1979, Mid-Mesozoic closure of Permo-Triassic Tethys and its implications: Nature, v. 279, p. 590–593.</ref> Dercourt et al.,<ref name=Dercourtetal_1993>Dercourt, J., Ricou, L. E., and Vrielynck, B., 1993, Atlas Tethys palaeoenvironmental maps: Paris, Gauthier-Villars, p. 307.</ref> Besse et al.,<ref name=Besseetal_1998>Besse, J., Torcq, F., Gallet, Y., Ricou, L. E., Krystyn, L., and Saidi, A., 1998, Late Permian to Late Triassic palaeomagnetic data from Iran: Constrains on the migration of the Iranian block through the Tethyan Ocean and initial destruction of Pangea: Geophysical Journal International, v. 135, p. 77–92.</ref> Metcalfe,<ref name=Metcalfe_2006>Metcalfe, I., 2006, Palaeozoic and Mesozoic tectonic evolution and palaeogeography of East Asian crustal fragments: The Korean Peninsula in context: Gondwana Research, v. 9, p. 24–46.</ref> Muttoni et al.<ref name=Muttonietal_2009a>Muttoni, G., Mattei, M., Balini, M., Zanchi, A., Gaetani, M., and Berra, F., 2009, The drift history of Iran from the Ordovician to the Triassic, in M.-F. Brunet, M. Wilmsen, and J. W. Granath, eds., South Caspian to Central Iran Basins: GSL Special Publications 312, p. 7–29.</ref>). According to Muttoni et al.,<ref name=Muttonietal_2003>Muttoni, G., Kent, D. V., Garzanti, E., Brack, P., Abrahamsen, N., and Gaetani, M., 2003, Early Permian Pangea ‘B’ to Late Permian Pangea ‘A’: Earth and Planetary Science Letters, v. 215, p. 379–394.</ref> <ref name=Muttonietal_2004>Muttoni, G., Kent, D. V., Garzanti, E., Brack, P., Abrahamsen, N., and Gaetani, M., 2004, Erratum to “Early Permian Pangea ‘B’ to Late Permian Pangea ‘A"’: Earth and Planetary Science Letters, v. 218, p. 539–540.</ref> <ref name=Muttonietal_2009b>Muttoni, G., Gaetani, M., Kent, D. V., Sciunnach, D., Angiolini, L., Berra, F., Garzanti, E., Mattei, M., and Zanchi, A., 2009b, Opening of the Neo-Tethys Ocean and the Pangea B to Pangea A transformation during the Permian: GeoArabia, v. 14, no. 4, p. 17–48.</ref> the Neotethyan opening is in part coeval to a major dextral motion of Laurasia relative to Gondwana that takes place essentially during Permian time. This relative motion causes the transformation of Pangea from an Early Permian configuration of the B-type, where Africa is placed south of Asia and South America is placed south of Europe,<ref name=Irving_1977>Irving, E., 1977, Drift of the major continental blocks since the Devonian: Nature, v. 270, p. 304–309.</ref> <ref name=Morelandirving_1981>Morel, P., and Irving, E., 1981, Paleomagnetism and the evolution of Pangea: Journal of Geophysical Research, v. 86, p. 1858–1987.</ref> <ref name=Muttonietal_1996>Muttoni, G., Kent, D. V., and Channell, J. E. T., 1996, Evolution of Pangea: Paleomagnetic constraints from the Southern Alps, Italy: Earth and Planetary Science Letters, v. 140, p. 97–112.</ref> <ref name=Torqetal_1997>Torq, F., Besse, J., Vaslet, D., Marcoux, J., Ricou, L. E., Halawani, M., and Basahel, M., 1997, Paleomagnetic results from Saudi Arabia and the Permo-Triassic Pangea configuration: Earth and Planetary Science Letters, v. 148, p. 553–567.</ref> <ref name=Bachtadseetal_2002>Bachtadse, V., Zanglein, R., Tait, J., and Soffel, H., 2002, Palaeomagnetism of the Permo/Carboniferous (280 Ma) Jebel Nehoud ring complex, Kordofan, Central Sudan: Journal of African Earth Sciences, v. 35, p. 89–97.</ref> <ref name=Irving_2005>
Irving, E., 2005, The role of latitude in mobilism debates: PNAS, v. 102, p. 1821–1828.</ref> <ref name=Angiolinietal_2007>Angiolini, L., Gaetani, M., Muttoni, G., Stephenson, M. H., and Zanchi, A., 2007, Tethyan oceanic currents and climate gradients 300 m.y. ago: Geology, v. 35, p. 1071–1074.</ref> to a Late Permian configuration of the Wegenerian A-type, where Africa is placed immediately south of Europe and South America is placed south of North America. The presence of a E-W trending trans-Pangean seaway (connecting the Paleo-Tethys to the Panthalassa oceans) persisting until the Late Permian is proposed by Vai<ref name=Vai_2003>Vai, G. B., 2003, Development of the palaeogeography of Pangaea from Late Carboniferous to Early Permian Palaeogeography, Palaeoclimatology, v. 196, p. 125–155.</ref> based on his interpretation of facies analyses and paleobiogeographic distribution of floral, reptile, and marine benthic organisms.
The proposed Early Permian reconstruction is from Muttoni et al.,<ref name=Muttonietal_2009b /> which is based on Early Permian poles that support a Pangea B configuration essentially similar to that originally proposed by Irving<ref name=Irving_1977 /> and confirmed by subsequent analyses.<ref name=Morelandirving_1981 /> <ref name=Muttonietal_1996 /> <ref name=Torqetal_1997 /> <ref name=Bachtadseetal_2002 /> <ref name=Muttonietal_2003 /> <ref name=Muttonietal_2004 /> <ref name=Angiolinietal_2007 /> The Cimmerian terranes (alternatively named Cimmeria Superterrane) are placed close to the Gondwanan margin in Early Permian time on the basis of geological, paleontological, and paleomagnetic evidences.<ref name=Stöcklin_1968>Stöcklin, J., 1968, [http://archives.datapages.com/data/bulletns/1968-70/data/pg/0052/0007/1200/1229.htm Structural history and tectonics of Iran: A review]: AAPG Bulletin, v. 52, p. 1229–1258.</ref> <ref name=Stöcklin_1974>Stöcklin, J., 1974, Possible ancient continental margins in Iran, in C. A. Burk and C. L. Drake, eds., The geology of continental margins: Springer-Verlag, p. 873–887.</ref> <ref name=Berberianandking_1981>Berberian, M., and King, G., 1981, Toward a paleogeography and tectonic evolution of Iran: Canadian Journal of Earth Sciences, v. 18, p. 210–265.</ref> <ref name=Wendtetal_2005>Wendt, J., Kaufmann, B., Belka, Z., Farsan, N., and Bavandpur, A. K., 2005, Devonian/Lower Carboniferous stratigraphy, facies patterns and palaeogeography of Iran Part II. Northern and central Iran: Acta Geologica Polonica, v. 55, no. 1, p. 31–97.</ref> <ref name=Muttonietal_2009b />
Neotethyan rifting along the eastern Gondwana margin from India<ref name=Garzantiandsciunnach_1997>Garzanti, E., and Sciunnach, D., 1997, Early Carboniferous onset of Gondwanian glaciation and Neo-Tethyan rifting in Southern Tibet: Earth Planetary Science Letters, v. 148, p. 359–365.</ref> to Oman<ref name=Albelushietal_1996>Al-Belushi, J., Glennie, K. W., and Williams, B. P. J., 1996, Permo-Carboniferous glaciogenic Al Khlata Formation, Oman: A new hypothesis for origin of its glaciation: GeoArabia, v. 1, p. 389–403.</ref> started in Carboniferous times and was followed by continental breakup and formation of oceanic crust in Early Permian time (mid-Sakmarian<ref name=Garzanti_1999>
Garzanti, E., 1999, Stratigraphy and sedimentary history of the Nepal Tethys Himalayan passive margin, in B. N. Upreti and P. Le Fort, eds., Advances on the geology of the Himalaya - focus on Nepal: Journal of Asian Earth Sciences, v. 17, p. 805–827.</ref> <ref name=Angiolinietal_2003>Angiolini, L., Balini, M., Garzanti, E., Nicora, A., and Tintori, A., 2003, Gondwanan deglaciation and opening of Neotethys: Palaeontological and sedimentological evidence from interior Oman: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 196, p. 99–123.</ref> <ref name=Metcalfe_2006 />). In the same time interval, a major zone of northward subduction of Paleotethyan oceanic crust was active along the Eurasian margin and persisted through most of Permian–Triassic times (e.g., Dercourt et al.,<ref name=Dercourtetal_1993 /> Alavi et al.,<ref name=Alavital_1997>Alavi, M., Vaziri, H., Seyed Enami, K., and Lasemi, Y., 1997, The Triassic and associated rocks of the Nakhlak and Aghdarband areas in central and northeastern Iran as remnants of the southern Turanian active continental margin: GSA Bulletin, v. 109, p. 1563–1575.</ref> Besse et al.,<ref name=Besseetal_1998 /> Metcalfe<ref name=Metcalfe_2006 />). Transpressive strike-slip tectonics was responsible for basin inversion in Lybia and Egypt.<ref name=Schandelmeierandreynolds_1997 />
In Pennsylvanian–Early Permian times, an extensive glaciation affected much of Gondwana (e.g., Stephenson et al.,<ref name=Stephensonetal_2007 /> Frank et al.<ref name=Franketal_2008 />), leaving widespread glacial deposits at high to intermediate southern latitudes. The tropical belt was thus restricted to very low latitudes, which benefited from a warm westward-flowing equatorial current, which, upon reaching the continental shelves of the western Tethys Gulf, deflected southeastward, bringing warm surface waters toward the northern corner of Arabia.<ref name=Angiolinietal_2007 /> This compressed tropical current gyre was bounded to the south by the thermal effects of the Gondwanan glacial climate, which directly controlled the distribution of cold biota in most other peri-Gondwanan terranes.