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.