Preprints
https://doi.org/10.5194/se-2020-184
https://doi.org/10.5194/se-2020-184

  20 Jan 2021

20 Jan 2021

Review status: a revised version of this preprint was accepted for the journal SE and is expected to appear here in due course.

Application of anisotropy of magnetic susceptibility (AMS) fabrics to determine the kinematics of active tectonics: Examples from the Betic Cordillera, Spain and the northern Apennines, Italy

David J. Anastasio1, Frank J. Pazzaglia1, Josep M. Parés2, Kenneth P. Kodama1, Claudio Berti3, James A. Fisher1, Alessandro Montanari4, and Lorraine K. Carnes5 David J. Anastasio et al.
  • 1Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA, 18015-3001, United States
  • 2Geochronology, Centro Nacional de Investigación de la Evolución Humana (CENIEH) Burgos, 09002, Spain
  • 3Idaho Geological Survey, Moscow, ID, 83844-3014, United States
  • 4Osservatorio Geologico di Coldigioco, Apiro MC, 62021, Italy
  • 5Arizona State University, Tempe, AZ, 85281, United States

Abstract. The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to measure fabrics and in the process, interpret the kinematics of actively deforming orogens. We collected rock fabric data of alluvial fan sediments surrounding the Sierra Nevada massif, Spain, and a broader range of Cenozoic sediments and rocks across the northern Apennine foreland, Italy, to explore the deformation fabrics that contribute to the ongoing discussions of orogenic kinematics. Sierra Nevada is a regional massif in the hinterland of the Betic Cordillera. We recovered nearly identical kinematics regardless of specimen magnetic minerology, structural position, crustal depth, or time. The principal elongation axes are NE-SW in agreement with mineral lineations, regional GPS geodesy, and seismicity results. The axes trends are consistent with the convergence history of the Africa-Eurasia plate boundary. In Italy, we measured AMS fabrics of specimens collected along a NE-SW corridor spanning the transition from crustal shortening to extension in the northern Apennines. Samples have AMS fabrics compatible only with shortening in the Apennine wedge and have locked in penetrative contractional fabrics, even for those samples that were translated into the actively extending domain. In both regions we found that specimens have a low degree of anisotropy and oblate susceptibility ellipsoids that are consistent with tectonic deformation superposed on compaction fabrics. Collectively, these studies demonstrate the novel ways that AMS can be combined with structural, seismic, and GPS geodetic data to resolve orogenic kinematics in space and time.

David J. Anastasio et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2020-184', Dario Bilardello, 22 Jan 2021
    • AC1: 'Reply on RC1', Dave Anastasio, 22 Jan 2021
    • AC2: 'Reply on RC1, Changes keyed to submitted manuscript lines based on review by Dario Biradello', Dave Anastasio, 01 Mar 2021
  • RC2: 'Comment on se-2020-184', Ruth Soto, 17 Feb 2021
    • AC3: 'Reply on RC2', Dave Anastasio, 01 Mar 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2020-184', Dario Bilardello, 22 Jan 2021
    • AC1: 'Reply on RC1', Dave Anastasio, 22 Jan 2021
    • AC2: 'Reply on RC1, Changes keyed to submitted manuscript lines based on review by Dario Biradello', Dave Anastasio, 01 Mar 2021
  • RC2: 'Comment on se-2020-184', Ruth Soto, 17 Feb 2021
    • AC3: 'Reply on RC2', Dave Anastasio, 01 Mar 2021

David J. Anastasio et al.

David J. Anastasio et al.

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Short summary
The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to interpret deforming mountain belts. In both the Betics, Spain and Apennines, Italy weak but well-organized AMS fabrics were recovered from young unconsolidated and unburied rocks that could not be analyzed with more traditional methods. Collectively, these studies demonstrate the novel ways that AMS can be combined with other data to resolve earthquake hazards in space and time.