Palaeomagnetism in fold and thrust belts: use with caution
E. L. Pueyo, A. J. Sussman, B. Oliva-Urcia, F. Cifelli, 2016. "Palaeomagnetism in fold and thrust belts: use with caution", Palaeomagnetism in Fold and Thrust Belts: New Perspectives, E. L. Pueyo, F. Cifelli, A. J. Sussman, B. Oliva-Urcia
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The application of palaeomagnetism in fold and thrust belts is a unique way to obtain kinematic information regarding the evolution of these systems. However, since many potential problems can affect the reliability of palaeomagnetic datasets and their interpretations, such data should be used with caution. In this paper, we thoroughly review the sources of error from palaeomagnetism with a particular focus on deciphering vertical-axis rotations and the assumptions behind the method. Recent investigations have demonstrated that the age of the magnetization and syn-folding results from the fold test must also be carefully examined: factors such as internal deformation, deficient isolation of components (i.e. overlapping) or incorrect restoration procedures may produce apparent syn-folding results. In fact, the restoration procedure used to return the palaeomagnetic signal to the palaeogeographic coordinate system may itself inhibit accurate estimations of vertical-axis rotations when complex deformation histories induce different, non-coaxial, deformation axes. We recommend the auxiliary use of the inclination v. dip diagram as an efficient tool for identifying many errors. Finally, to determine accurate vertical axis rotations, the reference direction should honour standard reliability criteria and would ideally be measured within the undeformed foreland of the thrust system. In this paper, we review five decades of palaeomagnetic research in fold and thrust belts by concentrating on maximizing standard reliability criteria procedures to reduce uncertainty and increase confidence when applying palaeomagnetic data to unravel the tectonic evolution of fold and thrust belts.
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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.