HR: 16:30h
AN: U34A-03    [Abstracts]
TI: No-Net-Rotation and Indo-Atlantic Hotspot Reference Frames: Towards a New View of Tectonic Plate Motions and Earth Dynamics
AU: * Quere, S
EM: squere@sca.uqam.ca
AF: Universite du Quebec A Montreal, Dept. des Sciences de la Terre, Succ. centre ville, Montreal, Qc H3C 3P8, Canada
AU: Rowley, D
EM: rowley@geosci.uchicago.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Avenue, Chicago, Il 60637, United States
AU: Forte, A
EM: forte.alessandro@uqam.ca
AF: Universite du Quebec A Montreal, Dept. des Sciences de la Terre, Succ. centre ville, Montreal, Qc H3C 3P8, Canada
AU: Moucha, R
EM: moucha@sca.uqam.ca
AF: Universite du Quebec A Montreal, Dept. des Sciences de la Terre, Succ. centre ville, Montreal, Qc H3C 3P8, Canada
AB: A new view of plate tectonics coupled to mantle dynamics is emerging from recent paleomagnetic reconstructions of tectonic plate histories obtained in the hotspot and no-net-rotation reference frames. A number of fundamental differences relative to past plate reconstructions have been discerned. Firstly, in previous models the difference between present-day plate motions in the global hotspot and no-net-rotation reference frames consisted of a westward drift of the lithosphere due to the dominant motion of the Pacific plate in the hotspot frame. In contrast, the new plate motion reconstructions based on the Indo-Atlantic hotspot reference frame now show that the present-day global rotation of the lithosphere is mainly in the South-North direction. Second, we find a more than 100% speed-up of the Nazca plate motion at 35 Ma which we have interpreted in terms of a slab avalanche event below the Nazca-South America plate boundary. This may be the first direct geological evidence for a mantle avalanche event occurring at a time which precedes a significant plate reorganisation. Third, the speed-up of the Nazca plate does not appear to be associated with a jump of the East-Pacific rise, therefore this feature may not be completely passive as previously thought. Fourth, the Hawaiian-Emperor bend which was a key element in previous plate reconstruction based on the assumption of a fixed Hawaiian hotspot, can no longer be explained by a change of direction of the Pacific plate and this corroborates recent studies showing a southward motion of the Hawaiian hotspot. Finally, the new Indo-Atlantic hotspot reconstruction of present-day plate motions is significantly different from the one previously established by Gripp and Gordon (1990) and the model appears to be in greater accord with plate motions predicted by seismic tomography-based mantle convection models.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1532 Reference fields: regional, global
DE: 7270 Tomography (6982, 8180)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Union [U]
MN: 2007 Fall Meeting