HR: 0800h
AN: GP41E-05 [Abstracts]
TI: Palaeomagnetic Study Along a 50 km Transect of a Middle Atlas Lava Field, Morocco.
AU: McIntosh, G
EM: gregc@fis.ucm.es
AF: Dpto Geofisica, Fac CC Fisicas, Universidad Complutense de Madrid, Avda Complutense
s/n, Madrid, Mad 28040, Spain
AU: * Ruiz-Martinez, V C
EM: vcarlos@fis.ucm.es
AF: Dpto Geofisica, Fac CC Fisicas, Universidad Complutense de Madrid, Avda Complutense
s/n, Madrid, Mad 28040, Spain
AU: Villasante, V
EM: vicvilla@fis.ucm.es
AF: Dpto Geofisica, Fac CC Fisicas, Universidad Complutense de Madrid, Avda Complutense
s/n, Madrid, Mad 28040, Spain
AU: Chalouan, A
EM: chalouan@yahoo.com
AF: Departement des Sciences de la Terre, Faculte des Sciences de Rabat, University
Mohammed V -Agdal, Rabat, Rab , Morocco
AU: El Kadiri, K
EM: khalilelkadiri@yahoo.fr
AF: Fac des Sciences de Tetouan, Universite de Tetouan, M'Hannech II, Tetouan, Tet 03003,
Morocco
AB:
The North-Middle Atlas fault (NMAF), Morocco, has acted as a source of Mio-Quaternary volcanism. This provides
a resource for palaeomagnetic studies of block rotation and palaeosecular variation in the region. Here we report
the results of a study of a lava field near the western margin of the NMAF. It was sampled at 16 sites (130
specimens) along a 50 km transect.
Rock-magnetic properties are fairly uniform across the sampled transect. Two magnetic phases dominate
throughout, a low Ti titanomagnetite and either an intermediate Ti titanomagnetite or pyrrhotite. AF
demagnetisation of NRM shows a unidirectional behaviour, isolating a well-defined ChRM exhibiting normal
polarity. Site- and flow- mean directions do not support any vertical-axis rotation in the area, as suggested by an
earlier, preliminary study of Quaternary lavas (6 sites, 28 samples) in the same area.
Analysis of the geomagnetic angular dispersion has been performed from both the spin axis and the mean of the
observed VGPs. The values obtained are close to those expected from consideration of the Palaeosecular
Variation from Lavas generalised databases, albeit with inclination flattening of a few degrees.
DE: 1519 Magnetic mineralogy and petrology
DE: 1522 Paleomagnetic secular variation
DE: 1525 Paleomagnetism applied to tectonics: regional, global
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly