Foliation and magnetic fabrics associated with fold interference in the Pyrenean Axial Zone (La Seu d’Urgell, Lleida)
DOI:
https://doi.org/10.55407/geogaceta100813Keywords:
fold interference, Sardic unconformity, cleavage, AMS, Variscan, PyreneesAbstract
The study area, in the vicinity of La Seu d’Urgell (Pyrenean Axial Zone), is composed of a stratigraphic series of Cambro-Ordovician rocks, mostly detrital, where the Sardic unconformity can be clearly identified, between the Jujols Series and Rabassa conglomerates Formation. The main structures are N-S folds with horizontal axial surfaces, that show an associated cleavage, well developed in the pelitic levels (and clearly distinguished in thin sections) and more poorly developed in the sandstone levels. In the conglomerates overlying the Sardic unconformity (Rabassa conglomerates Fm.) the regional cleavage is characterized by superposed conjugate shear bands surrounding the clasts. Magnetic fabrics (mainly paramagnetic) are consistent with the observed microstructures,although the correspondence of axes between the magnetic fabric and the structures observed in the field is not straightforward. The orientation of lineation directions are bimodal (N-S and E-W), a fact that can be interpreted as the result of fold interference (type 2 of Ramsay).
References
Carreras, J., y Capella, I. (1994). Journal of Structural Geology, 16(11), 1509-1524. https://doi.org/10.1016/0191-8141(94)90029-9
Casas, J. M. (2010). Geological Magazine,147(5), 674-689. https://doi.org/10.1017/S0016756809990756
Casas, J. M., Queralt, P., Mencos, J., and Gratacós, O. (2012). Distribution of linear mesostructures in oblique folded surfaces: Unravelling superposed Ordovician and Variscan folds in the Pyrenees. Journal of Structural Geology, 44, 141-150. https://doi.org/10.1016/j.jsg.2012.08.013
Cavet, P. (1957). Le Paléozoïque de la zone axiale des Pyrénées orientales françaises entre le Roussillon et l' Andorre (étude stratigraphique et paléontologique). Bulletin des Services de la Carte géologique de France, 254, 303-518.
García-Sansegundo, J. (1990). Structure of the Paleozoic in the Aran valley, Axial zone, central Pyrenees. Bull. Soc. Geol. Fr, 8, 229-239. https://doi.org/10.2113/gssgfbull.VI.2.229
García-Sansegundo, J. (1996). Journal of Structural Geology, 18, 1315-1325. https://doi.org/10.1016/S0191-8141(96)00050-8
Gil-Peña, I. y Barnolas, A. (2001). Bol. Geol. Min, 112, p. 17-38.
Margalef, A., Casas, J. M. and Queralt, P. (2012). Superposición de pliegues en el domo de la Rabassa: simulación usando el paquete FoldPlot (Mathematica). Geotemas, 13, 50-56.
Matte, P. (2002). Comptes Rendus Geoscience, 334(10), 773-779. https://doi.org/10.1016/S1631-0713(02)01808-4
Muñoz, J. A. (1992). In: Thrust Tectonics (K. R. McClay, Ed.). Springer, Dordrecht, 235-246. https://doi.org/10.1007/978-94-011-3066-0_21
Parés, J.M., Van der Pluijm, B.A.,(2002). Geophys. Res. Lett. 29 (24). https://doi.org/10.1029/2002GL015459
Parés, J. M. (2015). Frontiers in Earth Science, 3, 4.
Ramsay, J. G. (1967). Folding and fracturing of rocks. McGraw Hill, New York, p. 568.
Saura, E., y Teixell, A. (2006). Journal of Structural Geology, 28(11), 1909-1920. https://doi.org/10.1016/j.jsg.2006.06.005
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Copyright (c) 2024 Ana Simón Muzás, Antonio Casas Sainz, Ruth Soto, Pilar Clariana, Aina Margalef
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