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|Título:||Paleomagnetic study of the Messejana Plasencia dyke (Portugal and Spain): A lower Jurassic paleopole for the Iberian plate|
|Autor:||Ortas, A. Palencia|
Osete, M. L.
Atlantic Magmatic Province
Apparent Polar Wander
|Citação:||Ortas A P, Osete M L, Vegas R, Silva P. Paleomagnetic study of the Messejana Plasencia dyke (Portugal and Spain): A lower Jurassic paleopole for the Iberian plate.Tectonophysics. 2006; 420 ( 3-4): 455-472.|
|Relatório da Série N.º:||420;|
|Resumo:||The only Iberian lower Jurassic palcomagnetic pole come from the "Central Atlantic Magmatic Province"-related Messejana Plasencia dyke, but the age and origin of its remanence have been a matter of discussion. With the aim of solving this uncertainty, and to go further into a better understanding of its emplacement and other possible tectonic features, a systematic paleomagnetic investigation of 40 sites (625 specimens) distributed all along the 530 kin of the Messejana Plasencia dyke has been carried out. Rock magnetic experiments indicate PSD low Ti-titanomagnetite and magnetite as the minerals carrying the NRM. The samples were mostly thermally demagnetized. Most sites exhibit a characteristic remanent component of normal polarity with the exception of two sites, where samples with reversed polarities have been observed. The paleomagnetic pole derived from a total of 35 valid sites is representative of the whole structure of the dyke, and statistically well defined, with values of PLa = 70.4 degrees N, PLo = 237.6 degrees E, K= 47.9 and A(95) = 3.5 degrees. Paleomagnetic data indicates that: (i) there is no evidence of a Cretaceous remagnetization in the dyke, as it was suggested; (ii) most of the dyke had a brief emplacement time; furthermore, two dyke intrusion events separated in time from it by at least 10,000 y have been detected; (iii) the high grouping of the VGPs directions suggests no important tectonic perturbations of the whole structure of the dyke since its intrusion time; (iv) the pole derived from this study is a good quality lower Jurassic paleopole for the Iberian plate; and (v) the Messejana Plasencia dyke paleopole for the Iberian plate is also in agreement with quality-selected European and North American lower Jurassic paleopoles and the magnetic anomalies data sets that are available for rotate them to Iberia.|
|Aparece nas colecções:||ISEL - Eng. Civil - Artigos|
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|Paleomagnetic study of the Messejana Plasencia dyke (Portugal and Spain) - A lower Jurassic paleopole for the Iberian plate.rep.pdf||14,69 kB||Adobe PDF||Ver/Abrir|
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