Christopher M. Menges

Geomorphic, stratigraphic, paleomagnetic, and pedologic data reveal that: (a) the principal phase of the Basin and Range disturbance, sensu strictu, terminated within a latest Miocene to early Pliocene interval (~6 to 3 m.y.B.P) in two basins near Tucson; and (b) general tectonic quiescence has continued in these basins to the present. Approximately correlative relationships in adjacent basins suggest a similarly timed waning of large-scale Basin-Range tectonism throughout most of southeastern Arizona.

A distinctive suite of volcanic, sedimentary, structural, and physiographic characteristics permits differentiation of the post-1 2- to 15- Ma Basin-Range disturbance from earlier mid-Tertiary extensional tectonism in Arizona. Basin-Range volcanism comprises basalts or bimodal basalt-rhyolite suites that are concentrated in several fields in central and northern Arizona; the age of volcanism generally decreases northeast and east onto the Colorado Plateau margin.

This map presents data and interpretations concerning the distribution, amounts and timing of neotectonic faulting in Arizona. It is one part of a larger study and analysis of the neotectonic framework of Arizona..

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Susan Blake

Apache Leap Special Management Area
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