HR: 1340h
AN: T33C-1401    [Abstracts]
TI: Continental Rifting Across the Alarcon Basin, Gulf of California
AU: * sutherland, f H
EM: fi@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, MC 0225, La Jolla, CA 92093-0225 United States
AU: Harding, A J
EM: aharding@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, MC 0225, La Jolla, CA 92093-0225 United States
AU: Kent, G M
EM: gkent@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, MC 0225, La Jolla, CA 92093-0225 United States
AU: Lizarralde, D
EM: danl@eas.gatech.edu
AF: Georgia Tech, 311 Ferst Drive, Atlanta, GA 30332-0340 United States
AU: Holbrook, W S
EM: steveh@uwyo.edu
AF: Univeristy of Wyoming, 1000 E. University Avenue, Laramie, WY 82071 United States
AU: Fletcher, J M
EM: jfletche@cicese.mx
AF: CICESE, Dept. Geologica PO Box 434843, San Diego, CA 92143 United States
AU: Gonzalez-Fernandez, A
EM: mindundi@cicese.mx
AF: CICESE, Dept. Geologica PO Box 434843, San Diego, CA 92143 United States
AU: Umhoefer, P
EM: paul.umhoefer@nau.edu
AF: University of Northern Arizona, PO BOx 4099, Flagstaff, AZ 86011 United States
AU: Axen, G J
EM: gaxen@ess.ucla.edu
AF: UCLA, PO Box 951567, Los Angeles, CA 90095-1567 United States
AB: In Fall 2002 seismic refraction data and multi-channel seismic reflection data were collected in the Gulf of California as part of the Margins Rupturing Continental Lithosphere (RCL) initiative. Across the Alarcon Basin 56 Ocean-Bottom Seismometers and 11 onshore Ref-Teks collected wide-angle refraction data over an 880 km transect, coincident with 660 km of reflection data. The refraction data has been used to construct an initial velocity model across the entire rifted margin. Our results show ~150 km of new oceanic crust of normal thickness (6.5- 7 km) and lower crustal velocity (~6.7 km/s). The continent-ocean transition seems relatively abrupt occurring over less than 50 km on both conjugate margins. The rifted margin across the Alarcon Basin seems symmetric: There is roughly 300 km of extended continental crust on both margins- characterized by normal faulting at the surface and crust thinned to an average of 15 km with an average velocity of 6.2 km/s. At the furthest extents of our model, underneath the Baja peninsula crust seems to be about 28km thick, and under mainland Mexico about 26 km. Assuming an initially uniform crust of 30 km thickness, slightly greater than the observed maximum thicknesses, and 2-D extension there has been 100% extension across both margins. This predicts a total tectonic separation of around 470 km, which agrees with previous estimates for the Gulf of California of 450-500 km.
DE: 9305 Africa
DE: 8109 Continental tectonics--extensional (0905)
DE: 7205 Continental crust (1242)
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting