HR: 14:55h
AN: T32D-06    [PDF]
TI: Palinspastic Reconstructions of the Gulf of California Based on Airy Isostatic Profiles: Evidence for One Kinematic Phase of Neogene Shearing
AU: * Fletcher, J M
EM: jfletche@cicese.mx
AF: CICESE, Dept. Geologia PO Box 434843, San Diego, CA 92143 United States
AU: Martin-Atienza, B
EM: jfletche@cicese.mx
AF: CICESE, Dept. Geologia PO Box 434843, San Diego, CA 92143 United States
AU: Axen, G J
AF: UCLA, Dept. Earth & Space Sciences Box 951567, Los Angeles, CA 90095-1567 United States
AU: Gonzalez-Fernandez, A
AF: CICESE, Dept. Geologia PO Box 434843, San Diego, CA 92143 United States
AU: Holbrook, W S
AF: University of Wyomiing, Dept. of Geology and Geophysics, Laramie, WY 82071 United States
AU: Kent, G
AF: UCSD, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Lizarralde, D
AF: Georgia Tech University, School of Earth and Atmospheric Sciences, 221 Bobby Dodd Way, Atlanta, GA 30332 United States
AU: Harding, A
AF: UCSD, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Umhoefer, P
AF: Northern Arizona University, Department of Geology, P. O. Box 4099, Flagstaff, AZ 86011 United States
AB: Palinspastic reconstructions of serial crustal profiles drawn parallel to transform faults yield new estimates of total shear and define relative magnitudes of orthogonal versus transform-parallel rift components across the Gulf of California. Crustal thicknesses in serial cross sections across the Gulf depression were calculated from topographic profiles assuming local airy isostatic compensation, and model parameters like crust-mantle density contrast and thickness of a reference crust were calculated by fitting predetermined crustal thickness variations in the Peninsular Ranges and Gulf extensional province (e.g., Lewis et al., 2001, JGR). The serial cross sections show that the magnitude of seafloor spreading is highly variable and correlated with the geomorphologic expression of the spreading centers; magmatically robust ridges like the EPR, Alarcon and Guaymas have accommodated 210 to 340 km of separation, whereas, the magmatically starved centers that form deep rhombochasmic basins like the Pescadero, Carmen and Farallon have accommodated only 80-130 km of separation. Nonetheless, differences in the magnitude of seafloor spreading are systematically offset by differences in the magnitude of continental extension, and total tectonic separation calculated in nine separate profiles generally ranges from 450-500 km. Profiles across the southern tip of Baja show less total separation than those farther north, which indicates that there is small component (5-20 km) of margin-perpendicular tectonic transport. Because the total separation vector is large in magnitude and subparallel to the modern transforms, we infer that the Gulf must have opened in one kinematic phase of Neogene shearing.
DE: 8105 Continental margins and sedimentary basins
DE: 8107 Continental neotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting