Stratigraphy and Tectonic History of the Tucson Basin Pima County Arizona Based on the Exxon State (32)-1 Well

A detailed stratigraphy is presented, based on well cuttings and geophysical logs, for the 3,658 m of Upper Jurassic through upper Tertiary sedimentary and volcanic rocks overlying Precambrian(?) granitoid basement in the Tucson Basin. This is a revision of previous interpretations of Tucson Basin stratigraphy and is based in part on four new 40Ar/39Ar dates. The stratigraphic units are interpreted in terms of depositional environments and tectonic setting.

The Tucson Basin is a relatively large late Cenozoic extensional basin developed in the upper plate of the Catalina detachment fault in the southern Basin and Range Province, southeastern Arizona. In 1972, Exxon Company, U.S.A., drilled an exploration well (Exxon State (32)-1) near the center of the Tucson Basin that penetrated 3,658 m (12,001 ft) of sedimentary and volcanic rocks above granitoid basement. Detailed study of cuttings and geophysical logs of the Exxon State well has led to revision of the previously reported subsurface stratigraphy for the basin and provided new insight into its depositional and tectonic history.