Neogene plate-tectonic evolution of the Baja California Sur continental margin and the southern Gulf of California, Mexico
Jon E. Spencer, William R. Normark, 1989. "Neogene plate-tectonic evolution of the Baja California Sur continental margin and the southern Gulf of California, Mexico", The Eastern Pacific Ocean and Hawaii, E. L. Winterer, Donald M. Hussong, Robert W. Decker
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The Pacific margin of Baja California Sur was the site of plate convergence and subduction during late Mesozoic and early Cenozoic time. During the Neogene, the margin changed to a transform plate boundary as a result of either southward passage of a ridge-trench-transform triple junction, or cessation of spreading between the Pacific Plate and a small remnant of the FarallÃ³n- Guadalupe Plate. The latter possibility is preferred because a remnant of the FarallÃ³n-Guadalupe Plate, named the Magdalena Plate by Yeats and Haq (1981), appears to form the oceanic lithosphere at the foot of the continental margin off Baja California Sur. At about 5.5 Ma, the margin changed to a passive continental margin as the Baja California peninsula became part of the Pacific Plate and the modern Gulf of California began to form by rifting and transform faulting. In this chapter we briefly review theories concerning the Neogene plate-tectonic evolution of the area around the southern part of the Baja California peninsula, and review some of our own data from the Pacific continental margin of Baja California Sur that place constraints on the timing and nature of changes in plate-tectonic regimes and have implications for the existence of a Neogene embayment in the continental margin south of the tip of the Baja California peninsula. We are primarily concerned here with that period of time beginning approximately 14 Ma with cessation of subduction beneath Baja California Sur and ending approximately 5.5 Ma with formation of the modern San Andreas- Gulf of California system of strike-slip faults and spreading centers.
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The Eastern Pacific Ocean and Hawaii
This new synthesis includes a section on plate kinematics, documenting the basis for a new interpretation of the magnetic anomaly patterns. It also includes: six chapters on various aspects of tectonics, petrologic characteristics, and hydrothermal processes of active ridges from the Galapagos Rift to the Juan de Fuca Ridge; a section on mid-plate volcanism, including the Hawaii-Emperor chain; five chapters on various aspects of northeastern Pacific sedimentary regimes; and nine chapters on the geology of the Pacific continental margin from the Aleutians to Guatemala, seen from the perspective of marine geology. Three separate oversize plates illustrate the bathymetry of the northeast Pacific; two more on the same base show distribution of sediment samples and types and magnetic anomaly data and tectonic interpretations; and others include a synthesis of the geology and bathymetry of the Hawaiian Islands, details of bathymetry along parts of the East Pacific Rise, and a major seismic profile across the Pacific margin of Guatemala.