HR: 15:10h
AN: T32D-07    [PDF]
TI: Seismic Images of Faulting and Fossil Subduction of the Southern Baja California Margins
AU: * Gonzalez, A
EM: mindundi@cicese.mx
AF: Geology Department, CICESE., Km 107 Carr. Tijuana-Ensenada, Ensenada, BC 22830 Mexico
AU: Fletcher, J M
EM: jfletche@cicese.mx
AF: Geology Department, CICESE., Km 107 Carr. Tijuana-Ensenada, Ensenada, BC 22830 Mexico
AU: Lizarralde, D
EM: danl@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340 United States
AU: Kent, G M
EM: gkent@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive MC 0225, La Jolla, CA 92093-0225 United States
AU: Harding, A J
EM: aharding@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive MC 0225, La Jolla, CA 92093-0225 United States
AU: Holbrook, S
EM: steveh@uwyo.edu
AF: Department of Geology and Geophysics, University of Wyoming, 16th and Gibbon, Laramie, WY 82071-3006 United States
AU: Umhoefer, P J
EM: paul.umhoefer@nau.edu
AF: Department of Earth and Space Sciences, University of California Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095-1567 United States
AU: Axen, G J
EM: gaxen@dino.ess.ucla.edu
AF: Department of Geology, Northern Arizona University, Frier Hall, Building 12, Knoles Drive, Flagstaff, AZ 86011 United States
AU: Gorman, A R
EM: andrew.gorman@stonebow.otago.ac.nz
AF: Department of Geology, University of Otago, Leith Street, P.O. Box 56, Dunedin, 9015 New Zealand
AB: From September to November 2002, a marine geophysics experiment was carried out, using 2 ships and onshore personell, recording deep MCS (Multichannel Seismics), wide angle, gravity, magnetic and bathymetric data. The main objective of this experiment is to better understand the continental breakup processes and the rifting of the Baja California Peninsula from Mexico mainland. An array of airguns with a total air volume of 8000 cu.in. was the seismic source and a 6000 km-long, 480-channel streamer was used to record the deep MCS data. This equipment was towed by the R/V Maurice Ewing. A series of stacked and migrated sections have been obtained, showing a number of noticeable structures. To the W of the line corresponding to the Pacific margin, the fossil trench is covered by recent sediments, that are part of the Magdalena Fan. Towards the E, near the slope break, the Tosco-Abreojos fault zone is clearly imaged, showing some extensional component. Further to the E, an old syncline is covered in erosive unconformity by recent sediments. In the eastern part of the section, a half-graben structure can be observed. Under this structure, a reflective zone can be interpreted as the mylonitic zone corresponding to a detachment. Some basement scarpments seem to be parallel faults to the semigraben master fault. Other normal faults in the sediments of the basin are synthetic and antithetic with it. The master fault probably is the continuation to the S of the Santa Margarita-San Lazaro fault, reported previously as a detachment in Santa Margarita and Magdalena islands. The seismic line in the Gulf of California margin begins at a conspicuous slope at the mouth of the La Paz Bay, and corresponds to the same strike-slip fault observed in Partida and Espiritu Santo islands. The rest of the line is characterized by numerous strike-slip and normal faults, producing strong bathymetric variations.
DE: 0905 Continental structures (8109, 8110)
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting