New Early Permian paleomagnetic results from the Brive basin (French Massif Central) and their implications for Late Variscan tectonics

Chen, Yan; Henry, B.; Faure, Michel; Becq-Giraudon, Jean-François; Talbot, Jean-Yves; Daly, L.; Goff, Maxime Le

doi:10.1007/s00531-005-0010-5

Cited by 9 publications

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References 26 publications

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“…These findings are discussed in conjunction with data from the literature in quest for possible triggering mechanisms associated with Pangea instability and transformation during the late Paleozoic. To the west of the study area, a very similar timing of block rotations was observed in the Brive and Saint‐Affrique basins of the French Massif Central where Early Permian rocks show rotated paleomagnetic vectors while Late Permian rocks have not been affected by rotations [ Chen et al , 2006; see also Cogné et al , 1990, 1993; Diego ‐ Orozco and Henry , 1998; Henry et al , 1999; Diego ‐ Orozco et al , 2002]. Paleomagnetic data from the Maures‐Estérel massif located immediately to the east of our study area suggest a large clockwise block rotation during the Early to Middle Permian [ Edel , 2000].…”

Section: Discussionmentioning

confidence: 84%

“…The continental‐scale events of dextral shearing related to late Paleozoic Pangea instability should have left a fingerprint in the crustal structure of portions of southern Europe formerly located between Laurasia and Gondwana (Figures 1 and 2). For example, tectonic block rotations have been observed in Early Permian rocks from the French Massif Central, while Late Permian rocks from the same area are un‐rotated [ Chen et al , 2006, and references therein]; large rotations have also been documented in Late Carboniferous–Permian rocks from Maures‐Estérel in southern France and from Corsica‐Sardinia [ Edel , 2000; Emmer et al , 2005]; in Sardinia, recent paleomagnetic results indicate that these rotations should have occurred before Jurassic times [ Aubele et al , 2009; Kirscher et al , 2011].…”

Section: Introductionmentioning

confidence: 99%

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A paleomagnetic study of Permian and Triassic rocks from the Toulon‐Cuers Basin, SE France: Evidence for intra‐Pangea block rotations in the Permian

et al. 2012

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[1] The identification of a massive shear zone separating Gondwana from Laurasia during late Palaeozoic times is one of the prerequisites for the controversial Pangea B to A transition. Here we present new paleomagnetic data from Permian and Triassic sediments and volcanic rocks from the Toulon-Cuers basin, SE France, likely to be situated within this intra-Pangea shear zone. A total of 150 samples from 14 sites were collected in the field; 108 samples yielded reliable paleomagnetic component directions based on stepwise thermal demagnetization up to maximum temperatures of 690 C. After removal of an initial viscous magnetic component from room temperature up to 200 C, a second component of reverse polarity, oriented to the south-and-up, was identified in almost all samples of Permian age. The Triassic samples behave similarly, with the notable difference that here, two polarities of magnetization are present. Positive field tests suggest the primary character of this characteristic magnetization. The latitudes of the resulting Early to Mid Permian paleopoles agree well with the corresponding segment of the apparent polar wander path (APWP) for Europe, whereas the longitudes are strung out along a small circle segment, indicating relative rotations between the sampled regions and stable Europe. The Triassic poles, instead, plot close to the Triassic segment of the European APWP and provide an upper time limit for the observed rotations. These results suggest a wrench faulting event associated with intra-Pangea crustal instability and transformation during the Permian.

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Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

A paleomagnetic study of Permian and Triassic rocks from the Toulon‐Cuers Basin, SE France: Evidence for intra‐Pangea block rotations in the Permian

et al. 2012

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“…The Triassic poles, instead, plot close to the Triassic segment of the European APWP and provide a strong constraint on the age of the observed rotations, which is likely late Early‐Middle Permian. To the west of Toulon‐Cuers, a very similar timing of block rotations was observed in the Lodève, Brive, and Saint‐Affrique basins of the French Massif Central where Early Permian rocks show rotated paleomagnetic vectors while Late Permian rocks have not been affected by rotations [ Merabet and Guillaume , ; Cogné et al ., ; Diego‐Orozco and Henry , ; Henry et al ., ; Diego‐Orozco et al ., ; Chen et al ., ]. In addition, paleomagnetic data from the Maures‐Estérel massif located immediately to the east of the study area in SE France suggest a large clockwise block rotation during the late Early to Middle Permian [ Edel , ].…”

Section: Discussionmentioning

confidence: 99%

Paleomagnetic data from Late Paleozoic dykes of Sardinia: Evidence for block rotations and implications for the intra‐Pangea megashear system

Aubele

Bachtadse

Muttoni

et al. 2014

Geochem Geophys Geosyst

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Paleomagnetic studies of dyke swarms from the Variscan belt of Europe can be used to reconstruct internal postorogenic rotations within the fold belt. Here we present paleomagnetic data from 13 late Variscan dykes from Sardinia ranging in age from 298 6 5 to 270 6 10 Ma. The dykes can be grouped on the basis of their different directions in strike in a northern, a central-eastern and a south-eastern province. Paleomagnetic component directions have been obtained using thermal and alternating field demagnetization techniques, which give reproducible results. The paleomagnetic mean directions differ significantly between northern Sardinia and south-eastern and central-eastern Sardinia, the latter two regions yielding statistically similar paleomagnetic mean directions. These results indicate that Sardinia fragmented into two, arguably three, crustal blocks after emplacement of the dykes, which experienced differential relative rotations, as is also indicated by the differences in overall strike directions. The determination of timing, sense, and magnitude of these rotations has major implications for the reconstruction of the geodynamic evolution of the region in post-Carboniferous times. We argue that the observed block rotations occurred during the Permian as the result of post-Variscan intra-Pangea mobility possibly related to the transformation of an Early Permian Pangea B to a Late Permian Pangea A.

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“…They were therefore located just where most of the inferred shearing between Gondwana and Laurussia is expected to have taken place. We therefore speculate that post‐Variscan intra‐Pangea wrenching and shearing may have induced the large‐scale rotations of fault‐bounded blocks observed in Permian units of Sardinia as well as elsewhere in Europe, e.g., in the Saint‐Affrique and Brive basins of the French Massif Central [ Chen et al , 2006], as preliminarily discussed by Emmer et al [2005]. This inference, which remains at present speculative, however, will be explored in detail in a paleomagnetic work (now in progress) on Late Paleozoic–Middle Triassic rocks of Sardinia, which we consider as geological key witnesses of a major African‐European contact zone.…”

Section: Discussionmentioning

confidence: 99%

Paleomagnetism of Jurassic carbonate rocks from Sardinia: No indication of post-Jurassic internal block rotations

Kirscher¹,

Aubele²,

Muttoni

et al. 2011

J. Geophys. Res.

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[1] Several paleomagnetic studies on Carboniferous and Permian sedimentary and volcanic rocks from Sardinia and Corsica have recently demonstrated (1) the tectonic coherence between southern Corsica and northern Sardinia and (2) significant rotations between individual crustal blocks within Sardinia itself. The geodynamic significance of these rotations, however, is not clearly understood mainly because of uncertainties in defining their timing and causes. In order to contribute to these issues, a pioneering paleomagnetic study on Jurassic carbonates from the Baronie-Supramonte region of eastern-central Sardinia has been extended regionally and stratigraphically. A total of 280 oriented drill cores were taken from 44 sites of Middle and Late Jurassic age in the Nurra, Baronie-Supramonte, Barbagia-Sarcidano, and Sulcis regions. Despite generally weak remanent magnetization intensities, on the order of less than 1 mA/m, thermal and alternating field demagnetizations were successfully applied to define a characteristic remanent magnetization component in about 60% of the samples. Site mean directions show rather good agreement after correction for bedding tilt and yield Middle and Late Jurassic overall mean directions of D = 269.7°and I = 45.0°(a 95 = 8.0°, k = 14, and n = 25 sites) and D = 275.5°and I = 50.7°(a 95 = 7.2°, k = 45.3, and n = 10 sites). Positive regional and local fold and reversal tests demonstrate the primary character of the natural magnetic remanence, which is carried by magnetite. These results indicate only insignificant amounts (AE10°) of post-Jurassic rotations within the island of Sardinia. The resulting Middle and Late Jurassic paleopoles (latitude (Lat) = 16.5°, longitude (Long) = 299.1°, dp = 6.4°, and dm = 10.1°and Lat = 23.4°, Long = 301.2°, dp = 6.5°, and dm = 9.7°), corrected for the opening of (1) the Liguro-Provençal Basin and (2) the Bay of Biscay using rotation parameters from the literature, fall near the coeval segment of the European apparent polar wander path. These results constrain the timing of large differential block rotations found in Late Carboniferous-Permian rocks to a pre-Middle Jurassic age and lead us to exclude tectonics related to the Alpine orogeny for such rotations.

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New Early Permian paleomagnetic results from the Brive basin (French Massif Central) and their implications for Late Variscan tectonics

Abstract: In order to assess the structural evolution of the Brive basin and the Paleozoic activity of surrounding major faults in the French Massif Central, we carried out a paleomagnetic study

Cited by 9 publications

References 26 publications

A paleomagnetic study of Permian and Triassic rocks from the Toulon‐Cuers Basin, SE France: Evidence for intra‐Pangea block rotations in the Permian

A paleomagnetic study of Permian and Triassic rocks from the Toulon‐Cuers Basin, SE France: Evidence for intra‐Pangea block rotations in the Permian

Paleomagnetic data from Late Paleozoic dykes of Sardinia: Evidence for block rotations and implications for the intra‐Pangea megashear system

Paleomagnetism of Jurassic carbonate rocks from Sardinia: No indication of post-Jurassic internal block rotations

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