Late Miocene Extensional Deformation in the Sierra Bacha, Coastal Sonora, Mexico: Implications for the Kinematic Evolution of the Proto-Gulf of California
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Date
2011-12
Authors
Darin, Michael Harrison
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
The Gulf of California is an active rift basin formed by late Cenozoic dextral-oblique extension along the Pacific-North America plate boundary. Well exposed volcanic and sedimentary rocks in the Sierra Bacha, coastal Sonora, Mexico, preserve a history of proto-Gulf (late Miocene) deformation and offer insight into the structures and kinematics responsible for localization of the plate boundary and inception of the Gulf at about 6 Ma. Geologic mapping, fault kinematic analysis, and paleomagnetic data suggest that proto-Gulf deformation in the Sierra Bacha occurred primarily by ENE-WSW extension and that vertical-axis rotation related to dextral strain was minor. Lack of significant dextral shear supports an emerging model for proto-Gulf deformation in which dextral strain was not ubiquitous across Sonora but instead became localized during latest Miocene time in a narrow coastal shear zone that mechanically weakened the lithosphere and helped facilitate continental rupture.
This thesis includes the "Geologic Map of the Sierra Bacha, Coastal Sonora, Mexico" as supplemental material.
Description
xv, 95 p. : ill. (some col.), maps (some col.) Plate 1. Geologic Map of the Sierra Bacha, Coastal Sonora, Mexico (1:30,000 scale) attached as a separate file.
Keywords
Geology, Continental Dynamics, Plate Tectonics, Earth sciences, Extension, Gulf of California, Sonora, Strain localization, Transtension