Paleomagnetic study of the Messejana Plasencia dyke (Portugal
and Spain): A lower Jurassic paleopole for the Iberian plate
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2006
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Elsevier B.V.
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Abstract
The only Iberian lower Jurassic paleomagnetic 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 km 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°N, PLo=237.6°E,
K=47.9 and A95=3.5°. 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.