New insights into asymmetric folding by means of the anisotropy of magnetic susceptibility,Variscan and Pyrenean folds (SW Pyrenees) |
| |
Authors: | Belén Oliva-Urcia Inma Gil-Peña Ruth Soto José María Samsó Borja Antolín Emilio L. Pueyo |
| |
Affiliation: | 1.Department of Geology and Geochemistry, Sciences Faculty, Universidad Autonoma de Madrid,Calle Francisco Tomás y Valiente, 7,Madrid,Spain;2.Departamento de Ciencias de la Tierra,Universidad Zaragoza,Zaragoza,Spain;3.Instituto Geológico y Minero de Espa?a,Madrid,Spain;4.Instituto Geológico y Minero de Espa?a,Unidad de Zaragoza,Zaragoza,Spain;5.Consulting Geologist,Jaca,Spain;6.Department of Geological Sciences and Geological Engineering,Queen’s University,Kingston, Ontario,Canada |
| |
Abstract: | Magnetic fabric allows to unravel the petrofabrics of sedimentary rocks and to assess their deformational history. The use of this technique, in addition to classical structural field observations in the limbs of seven asymmetric folds in the Pyrenees, helps to determine the differences of internal deformation as well as the folding kinematics. Three folds developed during the Variscan Orogeny in Ordovician and Devonian rocks, and four folds developed during the Pyrenean Orogeny in Eocene rocks, are studied. Folds show a variety of structural locations, in different thrust sheets of the Southern Central Pyrenees, different cleavage development, age, geometry and lithology. Sampling follows an equivalent lithological layer in the two limbs, except for one case, of the selected folds. Results show a modified tectonic magnetic fabric in most sites with the magnetic lineation on the tectonic foliation plane. A larger scattering of the magnetic lineation (maximum magnetic anisotropy axis) and a higher intensity of the preferred orientation of minerals (eccentricity of the anisotropy of magnetic susceptibility - AMS ellipsoid) is better observed in the overturned (short) limb of the asymmetric Variscan folds than in the normal (long) limb. On the other hand, the shape parameter in Alpine folds is generally larger in the overturned (short) limb then in the normal (long) one. A good clustering of the minimum magnetic anisotropy axes is observed in all limbs. The combination of the AMS data with the structural data helps to understand and better constrain the deformation degree in these asymmetric folds and to unravel the deformational history. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|