Pliocene-Holocene Rifting and Associated Volcanism in Southwest Mexico: An Exotic Terrane in the Making
Published:January 01, 1991
J. F. Allan, S. A. Nelson, J. F. Luhr, I. S. E. Carmichael, M. Wopat, P. J. Wallace, 1991. "Pliocene-Holocene Rifting and Associated Volcanism in Southwest Mexico: An Exotic Terrane in the Making", The Gulf and Peninsular Province of the Californias, J. Paul Dauphin, Bernd R. T. Simoneit
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Three late Cenozoic rift systems—the northwest-trending Tepic-Zacoalco rift, the east-trending Chapala rift, and the north-trending Colima rift—intersect 50 km south-southwest of Guadalajara, Mexico to form a rift-rift-rift triple junction. These rifts structurally and topographically dominate the western part of the Mexican Volcanic Belt, a predominantly calc-alkaline continental arc. The Tepic-Zacoalco rift is the site of northwest-trending, late Cenozoic normal and right-lateral strike-slip faulting, whereas the Colima rift and its offshore extension (the Manzanillo Trough) overlies the subducting Rivera fracture zone, the boundary between the Rivera and Cocos plates. Together, the Colima and Tepic-Zacoalco rifts outline the Jalisco block. Associated with the rifts are 4.7 Ma to Holocene alkaline and peralkaline volcanic rocks, which are rarely found in continental volcanic arcs but are typical of continental rift zones. The alkaline volcanic rocks of western Mexico are thought to reflect rifting of the Jalisco block away from the Mexican mainland; the Jalisco block should eventually accrete to the Pacific plate. This rifting event represents the latest in a series of northward-propagating spreading-ridge jumps along the East Pacific Rise. Ongoing rifting in southwest Mexico may serve as a model for the rifting of Baja California, and for the origin of microplates and exotic terranes.
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The Gulf and Peninsular Province of the Californias
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.