Chanty Mansi Ocean
The Chanty-Mansi Ocean (English: Khanty-Mansi Ocean ), also known as the Chanty-Mansi-Backarc-Basin (English: Khanty-Mansi back-arc basin ), is a hypothetical ocean basin that lasted from the late Neoproterozoic to the higher Paleozoic in the vicinity of the European (Baltica) and Siberian craton (Sibiria, Angara-Kraton) should have existed. The “Chanty Mansi Ocean” concept is part of a plate tectonic reconstruction of the crustal development of Central and Northwest Asia in the Paleozoic Era (Altaiden Orogenic Complex), which was first published in 1993 by the Turkish geologist Celâl Şengör and colleagues. The name refers to the Khanty and Mansi , two Finno-Ugric speaking West Siberian peoples. Integral part of this hypothesis and directly associated with the concept of the Khanty-Mansi ocean is the Kiptchak-island arc (engl .: Kipchak arc ) formed in the late stage of its development the small continent Kasachstania ( Kazakhstan Tienschan- or Kazakhstan Kirgis-continent ) corresponds. It is named after the Kipchak languages , a branch of the Turkic languages .
development
initial situation
Paleomagnetic data allow the conclusion that in the late Neoproterozoic (" Vendian ") the cratons Baltica and Sibiria were connected to one another at their present northern edges and were located in the southern hemisphere. In current paleogeographical reconstructions, which take Şengör's hypothesis into account, “Balto-Sibiria” is integrated into the late Neoproterozoic supercontinent Pannotia .
Opening and widening
On the eastern edge of this Baltica-Sibiria block, which corresponds to today's eastern edge of Europe or the western edge of Siberia, there was a subduction zone on which the oceanic crust of the so-called Turkestan Ocean § plunged approximately westwards under the continental block. In the continental hinterland of the subduction zone, a crustal expansion then occurred, which in such a context is generally referred to as backarc expansion . As a result, a rift system parallel to the eastern edge of Balto-Siberia emerged from the late Vendium . As a result of sustained expansion, oceanic crust finally formed for the first time in the center of the rift valley. that is, the rift valley had expanded to form a narrow ocean basin that separated a narrow strip of continental crust from Balto-Sibiria. This strip is called the Kipchak island arc . The ocean basin at the back of the arch of the island is the Khanty Mansi Ocean. In the course of the Ordovician and Silurian era, the Chanty Mansi Backarc Basin opened up further. At about the same time as the formation of a rift valley on the eastern edge of Balto-Siberia, crust expansion also took place between the two cratons and ultimately led to their separation. The paleogeographical situation in the Middle Silurian can be roughly compared with today's Alëuten - Kommandeur -Bogen, under which the oceanic crust of the Pacific plate (analogous to the Turkestan Ocean) is subducted to the northeast and in its backarc basin , the Alëuten basin, the deep regions of the Bering Sea (analogous to the Khanty Mansi Ocean) extend.
Over the millions of years, the crust volume of the Kipchak island arc grew continuously, both through igneous activity and through the incorporation (accretion) of oceanic sediments and other parts of the crust of the descending plate onto the upper plate (see → Accretion Wedge ). In the Silurian, the arc was only in direct contact with the Siberian craton at its northern end. Its southern end was believed to have moved away from Baltica along an approximately east-west trending transform fault . At the same time, a subduction zone had formed on the then northern edge and today's eastern edge of Baltica, whereby a crust strip also loosened there, the Mugodschar island arc with the Sakmara-Magnitogorsk-Backarc basin on its rear.
closure
In the early Devonian, the southern tip of the Kipchak Arch collided with the Mugodschar Arch during a clockwise rotation of Siberia. This ushered in the deformation of the Kipchak Arch and the closure of the Khanty Mansi Ocean. The southern part of the Kipchak Arc was compressed in the course of the Devonian in north-south direction along by shifting leaves and a "kink" formed in its northern part. The "kinked" Kipchak arch is now referred to as the Kazakhstan orokline . Subduction and accretion only took place on the northern edge.
In the course of the Lower Carboniferous , Baltica * and Sibiria moved towards each other, while Sibiria continued to rotate. The Magnitogorsk-Backarc-Basin had closed and the Mugodschar-Inselbogen had been attached to the eastern edge of Baltica again. The Kazakh orokline was increasingly narrowed, and its former south branch was now parallel to today's eastern edge of Baltica with the Ural Mountains, which were in the process of being formed . ** In the Upper Carboniferous the rotation of Siberia stopped while Baltica and Siberia continued to approach. This eventually led to the complete closure of the Chanty Mansi Basin.
Alternative hypotheses and current reception
As an alternative to the Kipchak-arc-Khanty-Mansi-Backarc hypothesis, a Paleo-Asian Ocean is postulated, which from the early Silurian onwards is divided into four sub-basins: the Ural Ocean between Baltica, Siberia and Kazakhstan, the Ob-Zaisan Ocean between Siberia and Kazakhstan, the Dschungar-Balkhash Ocean enclosed by the Kazakhstan orocline, and the Turkestan Ocean between Kazakhstan and some Perigondwanian terranos. The name “Chanty-Mansi” in this model does not refer to an ocean basin, but to a microcontinent.
In older paleoplate tectonic reconstructions by the Swiss Gérard Stampfli, the concept of the Chanty Mansi Ocean is adopted. In these hypotheses, however, the Kipchak arch and Kazakhstan have a slightly different geometry and moreover collide with a perigondvanian crustal band, the so-called Hun superterran, in the Central Devonian . In more recent hypotheses about the development of the Altaids from the House of Stampfli, a Chanty Mansi ocean in the original Shengörian sense no longer occurs.
Remarks
- §corresponds to the Asian Ocean or Paleo- Asian Ocean by other authors (see alternative hypotheses )
- **The Ural ("Uralide accretionary complex") is described by Şengör et al. not added to the Altaids, but viewed as an independent orogen on today's eastern edge of Baltica.
literature
- AMC Şengör, BA Natal'in, VS Burtman: Evolution of the Altaid tectonic collage and Palaeozoic crustal growth in Eurasia. Nature. Vol. 364, 1993, pp. 299-306, doi : 10.1038 / 364299a0 .
Individual evidence
- ↑ IB Filippova, VA Bush, AN Didenko: Middle Paleozoic subduction belts: The leading factor in the formation of the Central Asian fold-and-thrust belt. Russian Journal of Earth Sciences. Vol. 3, No. 6, 2001, pp. 405-426, doi : 10.2205 / 2001ES000073
- ^ Brian F. Windley, Dmitriy Alexeiev, Wenjiao Xiao, Alfred Kröner, Gombosuren Badarch: Tectonic models for accretion of the Central Asian Orogenic Belt. Journal of the Geological Society. Vol. 164, No. 1, 2007, pp. 31–47, doi : 10.1144 / 0016-76492006-022 (alternative full text access : Researchgate )
- ↑ GM Stampfli, GD Borel: A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons. Earth and Planetary Science Letters. Vol. 196, No. 1–2, 2002, pp. 17–33, doi : 10.1016 / S0012-821X (01) 00588-X (alternative full text access : Researchgate )
- ^ Caroline Wilhem, Brian F. Windley, Gérard M. Stampfli: The Altaids of Central Asia: A tectonic and evolutionary innovative review. Earth Science Reviews. Vol. 113, No. 3-4, 2012, pp. 303-341, doi : 10.1016 / j.earscirev.2012.04.001