HR: 16:00h
AN: T34A-01 INVITED    [Abstracts]
TI: Observations of Extremely Thin Continental Crust: Paradoxes and Implications
AU: * Hopper, J R
EM: hopper@geo.tamu.edu
AF: Texas A&M University, Dept. of Geology and Geophysics, College Station, TX 77843, United States
AU: Manatschal, G
EM: manatschal@illite.u-strasg.fr
AF: University of Strasbourg, University of Strasbourg, Strasbourg, F-67084, France
AU: Lavier, L L
EM: luc@utig.ig.utexas.edu
AF: University of Texas, Austin, Jackson School of Geosciences, Austin, TX 78758, United States
AU: Muntener, O
EM: Othmar.Muntener@unil.ch
AF: University of Lausanne, University of Lausanne, Lausanne, CH-1015, Switzerland
AB: One of the most enigmatic problems in extensional tectonics is to understand the mechanics of thinning crust and lithosphere to an extreme amount. In magma starved settings, where extensional stresses can only be relieved by mechanical thinning, crust must be thinned from typically 30 km or more to only a few km thick before mantle exhumation takes place. Off the Galicia Bank, the zone of thinned crust consists of small half graben basins that appear to sit directly atop upper mantle. The existence of apparently only upper crustal rocks leads to imporant questions regarding what happens to mid and lower crust during such extreme extension. Along the Flemish Cap margin and conjugate to Galicia Bank, the thinning phase of breakup spans a very narrow region and is puzzling due to the lack of seismic evidence for signicant normal faulting in the uppermost crust. The region along the slope is nearly devoid of visible structure in seismic sections and the thinnest observed crust farther seaward shows only small throw normal faults and very little rotation. We summarize several competing hypotheses for the formation of these thin crust regions. In the absense of direct sampling, the available data may be unable to distinguish between these different models.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting