HR: 17:45h
AN: T34A-08    [Abstracts]
TI: Plate motion of Iberia relative to Europe in the Cretaceous: problems with the fit at M0 time
AU: * Norton, I O
EM: norton@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, Univ. of Texas, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AU: Lawver, L
EM: lawver@utig.ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, Univ. of Texas, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AU: Gahagan, L
EM: lisa@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, Univ. of Texas, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AB: Conjugate sets of sea floor magnetic chron M0 (120 Ma, Early Aptian) that have been mapped between Iberia and Newfoundland provide a well-constrained plate reconstruction of Iberia relative to North America. Other North Atlantic-bounding plate positions are less well constrained in the Early Cretaceous because these reconstructions require estimates of total extension vectors in basins bordering the North Atlantic. Published estimates of extension can, however, be used to build a satisfactory plate fit of Europe to North America in the Early Aptian. The resulting plate reconstruction shows a large, eastward-widening gap between eastern Iberia and Europe in the space now occupied by the Pyrenees. With M0 being at the beginning of the Cretaceous Superchron, the next youngest available plate reconstruction constrained by sea floor magnetic data is chron 34 (83 Ma, Campanian). The position of Iberia relative to Europe in this reconstruction suggests that the gap that existed between Iberia and Europe in the Aptian (at least in the M0 reconstruction) was closed by Campanian time. This implies several hundred kilometers of convergence between Iberia and Europe in the mid Cretaceous. Although feasible, such a large convergence amount should be recorded as a foldbelt and/or subduction system. Available data from the area suggest, however, that the mid Cretaceous was a time of tectonic quiescence, with the Pyrenean orogeny only initiating in the Eocene. One possible implication of these observations is that the fit of M0 is incorrect and that the magnetic lineation mapped as M0 is in fact not a sea floor spreading lineation. M0 occurs at the boundary between normal oceanic crust and the wide zones of exhumed mantle material found on both the Iberian and Newfoundland margins. We suggest that the M0 lineation is caused by a boundary effect between these different domains. An additional implication is that the boundary itself is not an isochron and is diachronous, with the transition from exhumation to sea floor spreading getting younger to the north along both margins.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8150 Plate boundary: general (3040)
DE: 8157 Plate motions: past (3040)
DE: 8162 Rheology: mantle (8033)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting