Reconstruction of inverted sedimentary basins from syn-tectonic remagnetizations. A methodological proposal
Juan J. Villalaín, Antonio M. Casas-Sainz, Ruth Soto, 2016. "Reconstruction of inverted sedimentary basins from syn-tectonic remagnetizations. A methodological proposal", Palaeomagnetism in Fold and Thrust Belts: New Perspectives, E. L. Pueyo, F. Cifelli, A. J. Sussman, B. Oliva-Urcia
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Syn-tectonic remagnetizations related to burial processes that occurred during their extensional stage are frequently recognized in inverted sedimentary basins. The incremental fold test is the main analytical tool used to detect these syn-tectonic remagnetizations. However this test gives spurious results when asymmetrical folding occurs (i.e. both limbs were not tilted simultaneously at the same rate). Asymmetrical folding is very common in sedimentary basins, especially at their margins, during the basinal stage and subsequent tectonic inversion. To correctly analyse syn-tectonic remagnetizations in these scenarios, we propose a method to restore palaeomagnetic vectors, which allows determining the tilting of beds at the remagnetization stage and therefore gives some hints on the geometry of sedimentary basins and/or folds at the overprint acquisition time. In this paper we consider the analysis of syn-tectonic remagnetization directions for basin reconstruction in two end-member basin models (i.e. syncline vs roll-over geometry). Finally, we compare the results obtained with several northern Iberian examples (Cameros basin in the Iberian Chain, Cabuérniga and Polientes Basin in the Pyrenées), formed during the Mesozoic as extensional basins and subsequently inverted during the Cenozoic compression. From these examples we propose generalizations for the application of syn-tectonic remagnetizations to constrain the geometry of sedimentary basins.
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Palaeomagnetism is a technique used to understand complex deformation patterns in fold-and-thrust belts; it can be used to characterize the distribution, magnitude and timing of vertical axis rotations, an elusive variable using other methods. A combination of palaeomagnetic and structural geology analyses has helped to unravel the geometry and kinematics of fold-and-thrust belts around the world and of different geological ages for more than 50 years. This volume comprises three sections: the first shows thorough overviews of western Mediterranean arcs and the western Carpathians; the second depicts several examples from the Andes, the Alps, Anatolia, Pyrenees, Iberian Ranges and the Atlas; and the third shows the latest research on the use of palaeomagnetism to understand fold-and-thrust belts in 3D and 4D in a more quantitative way and it also includes some methodological proposals to avoid common errors. In the papers of the first two sections, the combination of palaeomagnetic analyses with structural data, AMS or magnetostratigraphic analyses demonstrate the usefulness of palaeomagnetism in deciphering complex deformation patterns in fold-and-thrust belts.