recognition of pervasive remagnetization of the natural remanent magnetization
(NRM) is essential for a correct interpretation of paleomagnetic data and,
evidently, has important geodynamical implications.
It has only recently
become apparent that this ‘remagnetization syndrome’ may be much more widespread
than previously anticipated, particularly in sedimentary rocks of forelands
and outer margins of orogenic zones.
The proposed research
revolves around the Organya basin of Cretaceous age in the Pyrenees
Limestones and marly limestones constitute most of the lithology.
The NRM of the rocks
is argued to be non-remagnetized in the top while it is remagnetized in
the bottom (Dinarès-Turell,
J. and Garcia-Senz, J., 2000).
cores in Bajocian limestones in Aguilon
Font Bordonera marls below the Santa Fe formation, Organya Basin
the Font Bordonera marls on the northern side of the Organya syncline
could be the consequence of externally derived basinal fluids or
the result of burial diagenesis with a much more limited involvement of
Fe formation, Organya Basin
the Santa Fe formation, Organya Basin
To answer this question,
the research strategy involves optimizing a blend of mineral-magnetic,
paleomagnetic and ‘non-magnetic’ methods. The latter methods include thin
section and SEM/TEM microscopy on rocks and magnetic concentrates, determination
of the 87Sr/86Sr ratio from carbonates, and the determination
of smectite/illite ratios. The target is to extend the criteria to diagnose
remagnetization and to provide a more reliable basis for existing criteria,
independent of the analysis of paleomagnetic directions.
The research has also
been extended to Jurassic limestones from the Aguilon basin which show
a pervasive Cretaceous overprint and hence a partial remagnetization. Yet,
part of the original (Jurassic) signal has been preserved.
and Tithonian limestones near Aguilon
(above) and sampling (below) in the Aguilon Basin
Dekkers, M.J., Heslop, D. and Mullender, T.A.T. (2009). End-member modelling
of isothermal magnetization (IRM) acquisition curves: A novel approach
to diagnose remagnetization, Geophy. J. Int., 178, 693-701.
Van Hinsbergen, D.J.J., Vissers, R.L.M. and Dekkers, M.J. (2009). Early
Cretaceous syn-rotational extension in the Organyà basin: new constraints
on the palinspastic position of Iberia during its rotation, Tectonophysics,
Van Hinsbergen, D.J.J., Dekkers, M.J. (2009). Diachronous pervasive remagnetization
in northern Iberian basins during Cretaceous rotation and extension, Earth
Planet. Sci. Lett., 284, 292-301
Dekkers, M.J., Dinarès-Turell, J. and Mullender, T.A.T. (2008).
Remagnetization mechanism of Lower Cretaceous rocks from the Organyà
Basin (Pyrenees, Spain), Studia Geoph. Geod., 52, 187-210.
Langereis, C.G. and Mullender, T.A.T. (2008). The rotation of Iberia during
the Aptian and the opening of the Bay of Biscay, Earth Planet. Sci.
Lett., 273, 80-93
(2008). The rotation of Iberia during the Aptian and consequences for pervasive
Cretaceous remagnetization (PhD Thesis Utrecht University), Geologica
Ultraiectina, 292, 103 pp.