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An integrated AMS, structural, palaeo- and rock-magnetic study of Eocene marine marls from the Jaca-Pamplona basin (Pyrenees, N Spain); new insights into the timing of magnetic fabric acquisition in weakly deformed mudrocks

By
Juan C. Larrasoaña
Juan C. Larrasoaña
Paleomagnetic Laboratory, Institute of Earth Sciences ‘Jaume Almera’, CSIC, c/ Solé i Sabarís s/n, Barcelona 28080, SpainDepartment of Earth Sciences, University of Zaragoza, c/ Pedro Cerbuna 12, Zaragoza 50009, SpainSouthampton Oceanography Centre, European Way, Southampton S014 3ZH, UK e-mail: jc11@soc.soton.ac.uk
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Emilio L. Pueyo
Emilio L. Pueyo
Department of Earth Sciences, University of Zaragoza, c/ Pedro Cerbuna 12, Zaragoza 50009, SpainLaboratoire des Mécanismes de Transfert en Géologie, Université Paul Sabatier, Toulouse, France
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Josep M. Parés
Josep M. Parés
Department of Geological Sciences, University of Michigan, 2534 C. C. Little Building, Ann Arbor, MI 48109, USA
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Published:
January 01, 2004

Abstract

In this paper, we present a combined magnetic anisotropy (AMS), structural, palaeo- and rock-magnetic study of Eocene marine mudrocks from the western sector of the Jaca-Pamplona Basin (southwestern Pyrenees, north Spain). Comparison of structural, AMS and palaeomagnetic data reveals a subtle, but evident tectonic overprint affecting the phyllosilicate matrix of the mudrocks and the remanence carriers. The particular structural setting of the studied rocks has allowed us to combine palaeomagnetic and structural data with the AMS results in order to establish a relative chronology between sedimentation, blocking of magnetic fabrics, acquisition of magnetic remanence and deformation. Our data suggest that the blocking of the magnetic fabrics and the lock-in of the remanence occurred simultaneously during the early stages of gentle warping that affected the Jaca-Pamplona basin throughout the Mid-Late Eocene. According to the origin of the remanence carriers and the synsedimentary nature of the Mid-Late Eocene warping, the blocking of the magnetic fabrics and the lock-in of the remanence can be bracketed to a very short time span, of a few (<15?) ka, after sediment deposition. Our findings confirm previous interpretations claiming a very early origin of the magnetic fabric blocking in mudrocks undergoing weak deformation. They therefore validate the use of magnetic fabrics as palaeostress indicators and suggest that AMS data might also provide a useful tool for detecting preferred paths for the migration of geofluids during the early stages of deformation.

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Contents

Geological Society, London, Special Publications

Magnetic Fabric: Methods and Applications

F. Martín-Hernández
F. Martín-Hernández
Faculty of Geosciences, Utrecht University, The Netherlands
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C. M. Lüneburg
C. M. Lüneburg
Department of Geology and Geophysics, University of New Orleans, USA
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C. Aubourg
C. Aubourg
Laboratoire de Tectonique, Université de Cergy-Pontoise, France
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M. Jackson
M. Jackson
Institute for Rock Magnetism, University of Minnesota, USA
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Geological Society of London
Volume
238
ISBN electronic:
9781862394865
Publication date:
January 01, 2004

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