Tectonic evolution and global crustal architecture of the Variscan crust of the European Variscan belt constrained by geophysical data
Karel SchulmannJean Bernard EdelJosé R. Martı́nez CatalánStanisław MazurA.W. GuyJean Marc LardeauxP. AyarzaI. Palomeras
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Comprehensive set of seismic and potential field data from the whole European Variscan belt is used to interpret the structure and evolution of the European Variscides as defined by Martínez Catalán et al. (2021). The gravity data show the presence of high amplitude, short-wavelength gravity anomalies correlated with the outcrops of eclogites, ultramafic rocks and ophiolites delineating the main body of the Mid-Variscan Allochthon (MVA) and the Devonian Mid-Variscan suture (MVS). The medium amplitude and elongated long-wavelength gravity highs, aligned parallel to the Variscan structural grain, correspond to the low-grade Proterozoic rocks of the MVA and Devonian arc – back-arc system. On the other hand, the short wavelength negative gravity anomalies developed in the central part of the belt coincide with Carboniferous (330–310 Ma) per- to meta-aluminous magmatic bodies. The magnetic data show two belts correlated with Carboniferous Rhenohercynian and Devonian Mid-Variscan magmatic arc granitoids. The Rhenohercynian and Mid-Variscan subduction systems are also well-imaged by moderately dipping primary reflectors in reflection seismic lines. Younger moderately dipping reflectors in the upper-middle crust coincide with outcrops of Carboniferous detachments, limiting granite plutons and core complexes along-strike the core of the Variscan orogeny. Deep crustal reflectors are considered as an expression of lower crustal flow resulting from extensional re-equilibration of the previously thickened Variscan crust. A P-wave velocity logs synthesis shows a high-velocity cratonic crust surrounding a thin Variscan orogenic crust defined by low-velocity lower and middle crusts. The latter crustal type coincides with regional outcrops of 330–310 Ma per- to meta- aluminous granitoids and associated gravity lows along-strike the belt. All these data are used to define the primary polarity of Devonian subduction systems defining the European Variscan belt (Schulmann et al., 2022) and discuss the Carboniferous extension forming specific structure of the Variscan crust. This geodynamic evolution is integrated into a paleomagnetically constrained model of the movements of continental plates and intervening oceans (Edel et al., 2018; Martínez Catalán et al., 2021).REFERENCES:Catalan, J.R.M., Schulmann, K. and Ghienne, J.F., 2021. The Mid-Variscan Allochthon: Keys from correlation, partial retrodeformation and plate-tectonic reconstruction to unlock the geometry of a non-cylindrical belt. Earth-Science Reviews, 220, 1–65.Edel, J.B., Schulmann, K., Lexa, O. and Lardeaux, J.M., 2018. Late Palaeozoic palaeomagnetic and tectonic constraints for amalgamation of Pangea supercontinent in the European Variscan belt. Earth-science reviews, 177, 589-612.Schulmann, K., Edel, J.B., Catalán, J.R.M., Mazur, S., Guy, A., Lardeaux, J.M., Ayarza, P. and Palomeras, I., 2022. Tectonic evolution and global crustal architecture of the European Variscan belt constrained by geophysical data. Earth-Science Reviews, 234,  p.104195.Keywords:
Devonian
Orogeny
Jimushaer sag is the main Oil and Gas unit in the eastern part of Junggar Basin,it shows good exploration prospect in Carboniferous formation by accessing to industrial oil flow of well Ji15,We can find a clear overlap and trunction featrues by the detailed study of the seismic reflection characteristics of the Carboniferous in the area,and those characteristic can be carried out a very good comparison that used for strata correlation of the Carboniferous in the area.Based on the above,we classify the Bashan Formation in Upper Carboniferous and Low Carboniferous,then we divide the tectonic units of Carboniferous in the area.These results will play an important role in the exploration of Carboniferous
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Abstract The Daposhang section at Muhua, Changshun, Guizhou, is an excellent and attractive Devonian‐Carboniferous boundary section. The transitional beds between the Devonian and Carboniferous of the section are continuous and well exposed, belonging to the deep‐water basin facies. Abundant fossil groups have been discovered from this section: conodonts, ammonoids, trilobites, ostracods, vertebrate microfossils and so on. So far as known, it has the most continuous and complete conodont zonation for the Devonian‐Carboniferous boundary beds in the world. It is especially worth pointing out that both typical Siphonodella praesulcata and the transitional forms between S. praesulcata and S. sulcata have been found from the upper praesulcata Zone of the Daposhang section. Evidently, we can not only prove the actual existence of the evolutionary lineage from S. praesulcata to S. sulcata , but also exactly define the level of the Devonian‐Carboniferous boundary. In this paper, the development of the Devonian‐Carboniferous boundary beds at the Daposhang section is dealt with and the section is compared with the Muhua section and the Nanbiancun section which are the candidates for the Devonian‐Carboniferous boundary stratotype. In the authous' opinion the Daposhang section is obviously better than the Muhua and the Nanbiancun sections, hence it can be recommended as one of the candidates for the international Devonian‐Carboniferous boundary stratotype.
Devonian
Stratotype
Section (typography)
Conodont
Late Devonian extinction
Tournaisian
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Devonian
Orogeny
Marine transgression
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Devonian
Late Devonian extinction
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Abstract The Devonian stratigraphy of the Capertee geanticline is discussed. A fairly complete Devonian sequence is preserved in the Mudgee area, which shows no signs of a mid-Devonian (Tabber-abberan) orogeny, but has been affected by a Carboniferous orogeny, so that it resembles the New England area more than the rest of central-western New South Wales.
Devonian
Orogeny
Sequence (biology)
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Brachiopods from the Devonian-Carboniferous passage beds in the Babilon 1 column (Western Pomerania) (Preliminary Report) 42 brachiopod species belonging to 29 genera have been determined from the higher members of the Famennian and the Devonian-Carboniferous passage beds of the Babilon 1 column. Their distribution in the profile is shown and two assemblages distinguished, namely assemblage A - of the Devonian brachiopods and B – containing Devonian, Strunian and Carboniferous forms. Three subassemblages have been distinguished within the B” assemblage.
Devonian
Assemblage (archaeology)
Late Devonian extinction
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Devonian
Subgenus
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After correction for Mesozoic and Tertiary opening of the Atlantic, Ordovician and Silurian – Lower Devonian paleomagnetic poles from Britain are significantly different to contemporaneous results from North America. Upper Devonian poles from the two regions are similar. The discrepancy observed in the Ordovician and Silurian – Lower Devonian data is interpreted as due to major sinistral transcurrent faulting during the Middle Devonian concurrent with the short lived Acadian Orogeny. Rate of motion on this fault (or faults) was approximately 9 ± 4 cm/y. A consequence of this interpretation is that the Caledonide ocean was apparently narrow during the interval Ordovician to Devonian. However, inaccuracies in the paleomagnetic data permit the opening and closing of small ocean basins (≤ 1000 km), which may be related to the more extended Taconic Orogeny.
Devonian
Orogeny
Late Devonian extinction
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