Geologic map of the Lincoln Ranch Basin, eastern Buckskin Mountains, western Arizona. Report and one map sheet, map scale 1:24,000.

Quaternary geologic map of the Corona de Tucson 7.5' Quadrangle, Arizona. Map scale 1:24,000.

Geologic map of Saddle Mountain, Maricopa County, Arizona. Report and one map sheet, map scale 1:24,000.

New geologic mapping in the Bloody Basin of central Arizona’s Transition Zone reveals two distinct sets of normal faults that have a nearly 90° orientation with respect to one another. Miocene Hickey basalt unconformably overlies the Verde River granite that together makes a sequence of rocks that has been dissected into a series of tilted fault blocks. Regionally anomalous, northeast-striking normal faulting resulted in a synthetic array of half-grabens that are locally filled with a volcaniclastic conglomerate grading into a granite-rich conglomerate. These northeast-striking faults are thought to be influenced by a preexisting Precambrian structure that has been defined by aeromagnetic studies as the Holbrook lineament. This lineament projects directly through the Bloody Basin and would explain, at least in part, the origin of these anomalously oriented faults. Following this northwest-southeast directed extension, a dominant northeast-southwest extension direction resulted in a more regionally pervasive pattern of northwest-striking normal faults, including the Verde fault that cross-cuts the previously formed set. The least principal stress direction required for development of these extensional features is that which currently exists within the Colorado Plateau, northeast-southwest directed. The resultant thinned upper crust due to this extension gave way to the emplacement of a suite of mafic dikes that intruded basin-filling material shed during the first tectonic event.

This report presents the results of surficial geologic mapping of the Chandler Heights and Sacaton NE, 7.5-minute quadrangles located in the Santan Mountain piedmont area (herein referred to as Santan Piedmont) southeast of the Phoenix metropolitan area (Figure 1). Adjacent 7.5-minute quadrangles located to the east (Magma), south (Blackwater and Sacaton), and west (Gila Butte) have been previously mapped (Huckleberry 1993b, 1992). Most of the southern part of the Chandler Heights and Sacaton NE quadrangles is undeveloped and under the jurisdiction of the Gila River Indian Community and Bureau of Land Management; smaller areas are under private ownership and consist of low density housing. Most of the northern part of the Chandler Heights and Sacaton NE quadrangles is agriculturally developed and privately owned and includes the communities of Chandler Heights and Queen Creek. Most of the geologic materials within the project area are composed of deposits derived from the Santan Mountains except in the extreme northern and eastern portions where sediments are derived from the Superstition Mountains area (see Huckleberry, 1993b). Surficial Geology of the Santan Mountains Piedmont Area, northern Pinal and eastern Maricopa County Area, Arizona. Report with two map sheets, map scale 1:24,000.

Surficial geology of the Apache Junction Area, northern Pinal and eastern Maricopa Counties, Arizona. Report and two map sheets, map scale 1:24,000.

Most of southern and western Arizona lie within the Basin and Range physiographic province, a region characterized by broad valleys and linear mountain ranges. The valleys are deeply filled with alluvium that has eroded from adjacent mountains during the last 10 My 1. This aggradation has been driven by tectonism and climate change, although regional tectonic stability within the last 5 My suggests that climate change is the more recent dominant driving force (Morrison, 1985). Climatic fluctuations between relatively wet and dry conditions have resulted in pulses of aggradation producing a mosaic of different aged alluvial deposits in piedmont areas. Urban development on piedmonts, especially in the Phoenix Basin, has created a need to better understand the distribution and nature of these deposits. Surficial geologic maps characterize and distinguish different piedmont deposits on the basis of age and genesis. Such information provides baseline data for evaluating geologic hazards potential (e.g., Pearthree, 1991), locating possible source areas for industrial minerals (e.g., Wellendorf et aI., 1986), and determining locations favorable for groundwater recharge (e.g., Huckleberry, 1994). Moreover, these maps are also useful for assessing the potential for buried cultural resources and providing insight into local geologic history and landscape evolution. This report presents the results of surficial geologic mapping in the Wittmann and Hieroglyphic Mountains SW 7.5' quadrangles located northwest of metropolitan Phoenix (Figure 1). The project area includes segments of U.S. Highway 60, State Route 79, and the Central Arizona Project Canal, and is contiguous to the south with the White Tanks Mountain piedmont area previously mapped by Field and Pearthree (1991). (24 pages; 2 map sheets, map scale 1:24,000)

Geologic map of the Agua Caliente Mountains, Baragan Mountain, and Turtleback Mountain, Maricopa and Yuma Counties, Arizona. One map sheet, scale 1:24,000.

Geologic map of the Sacaton Moutains, Pinal County, Arizona. Two map sheets, map scale 1:24,000.

Geologic map of the Picacho Mine Area, southeastern California. Scale 1:10,000