Abstract
Geodynamics of Cenozoic extension along a transect across the Colorado River extensional corridor, southwestern USA
Highlights
The structural geology of the Colorado River extensional corridor, a 400-km-long belt of severe extension between Phoenix, Arizona, and Las Vegas, Nevada, is dominated by regionally eastward- and northeastwarddipping extensional detachment faults and the mylonitic footwall rocks that make up several metamorphic core complexes (Howard and John, 1987; Spencer and Reynolds, 1989a)
Exceptional exposures afforded by the arid environment in the Mojave-Sonoran Desert region, and the relative youth of extension, facilitated numerous studies over the past 50 years that were instrumental in understanding processes of severe tectonic extension of continental crust (e.g., Anderson, 1971; Reynolds and Rehrig, 1980; Davis et al, 1980, 1986; Wernicke, 1981, 1990; Howard et al, 1982a, 1982b; Wilkins and Heidrick, 1982; Spencer, 1984, 1999; John, 1987; Davis and Lister, 1988; Lister and Davis, 1989; Faulds et al, 1990; Richard et al, 1990; Foster et al, 1990, 1993; Spencer and Reynolds, 1990b, 1991; Scott and Lister, 1992; Livaccari et al, 1993; Livaccari and Geissman, 2001; Singleton, 2015; Gans and Gentry, 2016; Spencer et al, 2016b; Singleton et al, 2018; Prior et al, 2018)
The early Miocene geologic history of the northern Plomosa Mountains and western Bouse Hills was characterized by a period of basin genesis and sedimentation, mafic volcanism, and rock-avalanche deposition, followed by a period of extensional faulting that broke up and tilted previously deposited strata and was associated with dacitic volcanism and minor sedimentation
Summary
The structural geology of the Colorado River extensional corridor, a 400-km-long belt of severe extension between Phoenix, Arizona, and Las Vegas, Nevada, is dominated by regionally eastward- and northeastwarddipping extensional detachment faults and the mylonitic footwall rocks that make up several metamorphic core complexes (Howard and John, 1987; Spencer and Reynolds, 1989a). The contrast in extensional faulting north and south of Plomosa Pass has been inferred to reflect a concealed, northeast-dipping normal fault, with characteristic southwest tilting of volcanic rocks in its hanging-wall block (Spencer and Reynolds, 1991).
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