Paleomagnetic Evidence for Microplate Tectonic Development of Southern and Baja California
Steve P. Lund, David J. Bottjer, 1991. "Paleomagnetic Evidence for Microplate Tectonic Development of Southern and Baja California", The Gulf and Peninsular Province of the Californias, J. Paul Dauphin, Bernd R. T. Simoneit
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This chapter summarizes Mesozoic and Cenozoic paleomagnetic data from southern and Baja California that document significant latitudinal and rotational displacements of large-scale blocks within this region. Much of the displacement is associated with two large allochthonous terranes—the Santa Lucia allochthon and the Peninsular Ranges terrane—that accreted to the North American craton during the Tertiary. The Santa Lucia allochthon amalgamated at equatorial paleolatitudes during the Mesozoic, traveled northward relative to North America between 70 and 50 Ma, and accreted to North America in the Eocene. The Peninsular Ranges terrane amalgamated along the western margin of southern Mexico and Central America during the Mesozoic and early Tertiary, traveled northward relative to North America some time after 40 Ma, and accreted to North America and the Santa Lucia allochthon by the early Miocene. The suture zone between the Peninsular Ranges terrane and the Santa Lucia allochthon is marked by 90° clockwise rotations of structural blocks within these terranes. Other structural blocks in southern California have also been rotated, either as part of the tectonic processes associated with terrane accretion, or as part of later regional extension and right-lateral strike-slip motion along southern California faults.
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The Gulf of California is an excellent laboratory for studying sedimentary processes on time scales that are not resolvable in the open ocean. The high biological productivity and the unique physical character of the gulf combine to produce sedimentological processes that preserve annual phenomena. This volume is organized into six sections. Part 1 covers historical exploration of the area. Part 2 includes 5 chapters detailing information contained on the 5 fold-out maps that accompany the volume. Part 3 consists of chapters on regional geophysics and geology. Part 4 covers satellite geodesy. Part 5's seven chapters discuss physical oceanograpy, primary productivity, and sedimentology. Part 6 covers hydrothermal processes.