HR: 17:05h
AN: GP34A-04    [Abstracts]
TI: Structural Implications of the Paleomagnetic Data from the Aptian-Albian Sedimentary Formation in Lebanon
AU: * Henry, B
EM: henry@ipgp.jussieu.fr
AF: Paleomagnetism, IPGP, 4 avenue de Neptune, Saint-Maur cedex, 94 94107, France
AU: Homberg, C
EM: homberg@hermes.lgs.jussieu.fr
AF: Tectonique, UPMC, 4 place Jussieu, Paris cedex 05, 75 75252, France
AU: Mroueh, M
EM:
AF: Lebanese University, Beirut, Beirut, Lebanon
AU: Hamdan, W
EM:
AF: Lebanese University, Beirut, Beirut, Lebanon
AU: Higazi, F
EM:
AF: Lebanese University, Beirut, Beirut, Lebanon
AB: In order to estimate the block rotations around the central part of the Dead Sea Transform, 325 cores of Aptian and Albian rocks were sampled in 38 sites in Lebanon. Sites are situated in the cores and limbs of the Mount Lebanon and Mount Anti-Lebanon anticlines, with a widespread regional distribution. The intensity of the Natural Remanent Magnetisation is mostly low. Hysteresis loops indicates presence of at least two magnetic phases, one having high coercivity. In most samples, the NRM includes two components in addition to a viscous component A: component B carried by magnetite and component C carried by high coercive minerals. The mean direction of component B is slightly different before and after bedding correction, with a better clustering in inclination after the correction. Significant scattering in declination indicates effect of some local rotation. Progressive bedding correction for all the 37 sites gives the best clustering (maximum k value=17.8) for 85% of unfolding, but without significant difference with 100% unfolding (k=17.6). Positive reversal test in one site strongly suggests that component B is the primary magnetisation. The direction of component C has a coherent orientation before bedding correction. Its high clustering, its only normal polarity, and the significant fold test strongly argue for a single component acquired after folding. From comparison of the declination of the magnetisation component B with the African Apparent Polar Wander Path, a mean counter-clockwise rotation of 28.0 ± 6.4° affected all our sites since Lower Cretaceous period. According to the orientation of the component C, part of this rotation (17.7 ± 3.8°) occurred after folding, i.e. after the Late Miocene. A global rotation of all the Levant area being inconceivable, rotation affected small blocks limited by the numerous dextral presently E-W faults existing in Lebanon.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1525 Paleomagnetism applied to tectonics: regional, global
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly