The Tucson 1 ° X 2.0 quadrangle exhibits a wide variety of basin landforms and late Cenozoic surficial geologic deposits. Several factors contribute to this diversity. The Tucson quadrangle spans the transition between the relatively low ranges and typically undissected basins of south-central Arizona and the higher ranges and typically dissected basins of southeastern Arizona.
This report is a compilation of available data on Quaternary faults in Arizona as of the summer of 1998. These data were compiled as part of a effort to compile data and map information on Quaternary faults throughout the world, which is being overseen by Michael Machette of the U.S. Geological Survey.
One of the fastest growing areas of Arizona is the eastern part of the Phoenix Basin near the communities of Chandler, Gilbert, Mesa, and Apache Junction. Much of this development has occurred on the piedmont near the base of the mountains where little of the surficial geology has ever been mapped. Because this area of the Phoenix Basin will continue to grow in the future, there is a need to understand the nature and distribution of surficial deposits.
The study area is situated along the southern edge of the Superstition Mountains approximately 40 miles east of the greater Phoenix metropolitan area (Figure 1). Geology is dominated by mid-Tertiary volcanic rocks of the Superior volcanic field (Ransome, 1903), and these rocks depostionally overlie a crystalline basement of early Proterozoic Pinal Schist intruded by middle Proterozoic granitoids. In some areas a relatively thin sequence of the Middle Proterozoic Apache Group occurs along the contact between these two rock types.
The Copper Mountain quadrangle is centered just north of the southwest-facing escarpment on the southwest side of the crest of the Sierra Ancha. Elevations range from about 4200 feet in the southwest corner of the map to 6676 feet at Copper Mountain.
New geologic mapping from the Cedar Mountains - Bloody Basin - Cooks Mesa area in the central Arizona Transition Zone presents an enigmatic geologic relationship that has previously gone unstudied. Here, fault blocks of Early Proterozoic basement overlain by Tertiary sedimentary and tuffaceous-lacustrine deposits and capped by a thick accumulation of basalt flows, dated in the project area between 15.1 and 13.5 Ma, are rotated ~20o west to west-southwest along east-dipping normal faults.
The Picketpost Mountain and Iron Mountain 7.5' quadrangles are located east of the Phoenix metropolitan area and are within the Basin and Range physiographic and tectonic province of southwestern North America.
The study area is situated along the southern edge of the Superstition Mountains approximately 40 miles east of the greater Phoenix metropolitan area (Figure 1). Geology is dominated by mid-Tertiary volcanic rocks of the Superior volcanic field (Ransome, 1903), and these rocks depostionally overlie a crystalline basement of early Proterozoic Pinal Schist intruded by middle Proterozoic granitoids. In some areas a relatively thin sequence of the Middle Proterozoic Apache Group occurs along the contact between these two rock types.
The draft EIS public comment period closed November 7, 2019. All 30,000+ comment submittals are now under review for consideration in the compilation of the final EIS.
