HR: 16:20h
AN: GP24A-01 INVITED     [Abstracts]
TI: Paleomagnetism and Tectonic Evolution of Mexico: Precambrian to Recent
AU: * Fucugauchi, J U
EM: juf@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, UNAM, Ciudad Universitaria, Coyoacan, Mexico, 04510, Mexico
AB: It is 20yr since publication of the last synthesis of country-wide paleomagnetic data and almost 30yr of first attempt to construct an apparent polar wander path for Mexico. During this time, data has increased ten-fold and a new synthesis may appear long overdue. Mexico constitutes the southern portion of the North American plate, and tectonic models long suggested a complex evolution involving ocean-basin closure, continental collision/break-up, terrane accretion, large-scale motions, orogenic deformation, oceanic plate reorganizations and oceanic basin development. Paleoreconstructions of Atlantic-bordering continents show major overlap of northern South America onto Mexico, highlighting the geometric problem, allocthonous nature and opening room for a diversity of models. Paleomagnetism appears well-suited to tackle these problems, and data had early been used to evaluate tectonic models. Likewise, the larger database is now used to assess models and develop alternatives. This task is greatly aided by new available geochronological, geophysical and geological data. Our new synthesis still shows data gaps, with Paleozoic and Precambrian units poorly represented. Paleomagnetic data and tectonic models require complex large-scale motions of Precambrian and Paleozoic blocks, solutions for opening of Gulf of Mexico and Caribbean Sea, and post-Triassic-Jurassic amalgamation of Mexico and Central America. The southern edge of the North American craton is positioned in northern Mexico, marking the limit for accreted terranes to the south. Possible southern extension of Marathon-Ouachita Paleozoic belt, obscured or truncated when it comes into Mexico, remains unstudied paleomagnetically. Left-lateral motions along faults related to opening of Gulf of Mexico are not supported by paleomagnetism. The Western Cordilleran belt appears laterally displaced in southern US and into Mexico, where the paleomagnetic signature of northward latitudinal translations and clockwise rotations pervasive in the north changes to counterclockwise rotations and smaller latitudinal translation. The Cenozoic record is somehow consistent with models of regional left-lateral shear and vertical axis rotations. Recent major deformation is related to Gulf of California opening, margin truncation, oblique subduction and translation of margin slivers.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1533 Remagnetization
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly