The Walker Lane belt of eastern California and western Nevada is the northernmost extension of the Gulf of California transtensional rift, where the process of continental rupture has not yet been completed, and rift initiation can be studied on land. GPS and earthquake focal mechanism studies demonstrate that the Walker Lane belt currently accommodates NW-SEdirected movement between the Sierra Nevada microplate and the North American plate, but the timing and nature of rift initiation remains unclear. In this paper, Cathy J. Busby presents a model for plate-margin-scale initiation of the Gulf of California and Walker Lane transtensional rifts approx. 12 million years ago. Busby notes that localization of rifting in both was initiated by thermal weakening in the axis of a subduction- related arc undergoing extension due to slab rollback, and thermal weakening in the arc was enhanced by stalling of the trenchward- migrating precursor arc against a thick Cretaceous batholithic lithospheric profile on its western margin. Rifting succeeded very quickly in the Gulf of California, due to stalling of Farallon slabs, but the Walker Lane transtensional rift has been unzipping northward along the axis of the Cascades arc, following the Mendocino triple junction.
Late Oligocene to middle Miocene rifting and synextensional magmatism in the southwestern Sierra Madre Occidental, Mexico: The beginning of the Gulf of California rift
Luca Ferrari et al., Centro de Geociencias, Universidad Nacional Autnoma de Mxico, Campus Juriquilla, 76230, Quertaro, Qro., Mexico. Posted online 13 Sept. 2013; http://dx.doi.org/10.1130/GES00925.1. Themed issue: Origin and Evolution of the Sierra Nevada and Walker Lane.
Although Basin and Range-style extension affected large areas of western Mexico after the Late Eocene, m
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