Encontrados 11 documentos, a visualizar página 1 de 2
Palaeomagnetism in the Sines massif (SW Iberia) revisited: evidences for Late C...
Ribeiro, Paulo; Silva, Pedro; Moita, Patrícia; Kratinova, Zuzana; Marques, Fernando; Henry, BernardThis study revisits the palaeomagnetism of the Sines massif (∼76 Ma) in the southwestern Iberian Margin (Portugal). The palaeomagnetic analysis was complemented by a comprehensive study of the magnetic mineralogy by means of rock magnetic measurements and petrographic observations. The overall dispersion of palaeomagnetic directions (declination ranging between ∼N0º and ∼N50º) and their migration observed durin...
Reply to the comment by Quartau and Mitchell on “Reconstructing the architectur...
Hildenbrand, Anthony; Marques, Fernando; Costa, A.; Sibrant, A.; Silva, Pedro; Henry, Bernard; Miranda, Jorge Miguel; Madureira, PedroReply to the comment by Quartau and Mitchell on “Reconstructing the architectural evolution of volcanic islands from combined K/Ar, morphologic, tectonic, and magnetic data: The Faial Island example (Azores)”, J. Volcanol. Geotherm. Res. 241–242, 39–48, by Hildenbrand et al. (2012)
Palaeomagnetic study of a subaerial volcanic ridge (S˜ao Jorge Island, Azores) ...
Silva, Pedro; Henry, Bernard; Marques, Fernando; Hildenbrand, Anthony; Madureira, Pedro; Mériaux, Catherine; Kratinová, ZusanaWe present a palaeomagnetic study on 38 lava flows and 20 dykes encompassing the past 1.3 Myr on S. Jorge Island (Azores Archipelago—North Atlantic Ocean). The sections sampled in the southeastern and central/western parts of the island record reversed and normal polarities, respectively. They indicate a mean palaeomagnetic pole (81.3◦N, 160.7◦E, K = 33 and A95 = 3.4◦) with a latitude shallower than that expect...
Reconstructing the architectural evolution of volcanic islands from combined K/...
Hildenbrand, Anthony; Marques, Fernando; Costa, A.; Sibrant, A.L.R.; Silva, Pedro; Henry, Bernard; Miranda, Jorge; Madureira, PedroThe morpho-structural evolution of oceanic islands results from competition between volcano growth and partial destruction by mass-wasting processes. We present here a multi-disciplinary study of the successive stages of development of Faial (Azores) during the last 1 Myr. Using high-resolution digital elevation model (DEM), and new K/Ar, tectonic, and magnetic data, we reconstruct the rapidly evolving topograp...
Reconstructing the architectural evolution of volcanic islands from combined K/...
Hildenbrand, Anthony; Marques, Fernando; Costa, A.C.G.; Sibrant, A.L.R.; SIlva, Pedro; Henry, Bernard; Miranda, Miguel; Madureira, PedroThe morpho-structural evolution of oceanic islands results from competition between volcano growth and partial destruction by mass-wasting processes. We present here a multi-disciplinary study of the successive stages of development of Faial (Azores) during the last 1 Myr. Using high-resolution digital elevation model (DEM), and new K/Ar, tectonic, and magnetic data, we reconstruct the rapidly evolving topograp...
Thick dyke emplacement and internal flow: A structural and magnetic fabric stud...
Silva, Pedro; Marques, Fernando; Henry, Bernard; Madureira, Pedro; Hirt, Ann; Font, Eric; Lourenço, NunoKnowledge on forced magma injection and magma flow in dykes is crucial for the understanding of how magmas migrate through the crust to the Earth's surface. Because many questions still persist, we used the long, thick, and deep-seated Foum Zguid dyke (Morocco) to investigate dyke emplacement and internal flow by means of magnetic methods, structural analysis, petrography, and scanning electron microscopy. We a...
Multi-stage evolution of a sub-aerial volcanic ridge over the last 1.3 Myr: S. ...
Hildenbrand, Anthony; Madureira, Pedro; Marques, Fernando; Cruz, Inês; Henry, Bernard; Silva, PedroNew K/Ar dating and geochemical analyses have been carried out on the WNW-ESE elongated oceanic island of S. Jorge (central Azores) to reconstruct the volcanic evolution of a linear ridge developed close to the triple junction between the American, the Eurasian and the Nubian lithospheric plates. We show that S. Jorge sub-aerial edification encompasses the last 1.3 Myr, a time interval far much longer than prev...
Multi-stage evolution of a sub-aerial volcanic ridge over the last 1.3 Myr: S. ...
Hildenbrand, Anthony; Madureira, Pedro; Marques, Fernando; Cruz, Inês; Henry, Bernard; Silva, PedroNew K/Ar dating and geochemical analyses have been carried out on the WNW–ESE elongated oceanic island of S. Jorge to reconstruct the volcanic evolution of a linear ridge developed close to the Azores triple junction. We show that S. Jorge sub-aerial construction encompasses the last 1.3 Myr, a time interval far much longer than previously reported. The early development of the ridge involved a sub-aerial build...
Resultados preliminares de um estudo paleomagnético da ilha do Faial (Arquipéla...
Silva, Pedro; Henry, Bernard; Hildenbrand, Anthony; Marques, Fernando; Madureira, PedroWe present preliminary paleomagnetic results dor Faial Island (central group of Azores Archipelago, North Atlantic Ocean). Our sampling strategy was focused on a collection of samples from lava flows that represent a large temporal window according to previous geochronological data. Main results show that: (i) onshore volcanic activity began during the Matuyama geomagnetic chron; (ii) the southern branch of the...
Variation of magnetic properties in sedimentary rocks hosting the Foum Zguid dy...
Silva, Pedro; Henry, Bernard; Marques, Fernando; Mateus, António; Madureira, Pedro; Lourenço, Nuno; Miranda, MiguelThe effects of dyke intrusion on the magnetic properties of host sedimentary rocks are still poorly understood. Therefore, we have evaluated bulk magnetic parameters of standard palaeomagnetic samples collected along several sections across the sediments hosting the Foum Zguid dyke in southern Morocco. The study has been completed with the evaluation of the magnetic fabric after laboratory application of sequen...
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