Description:
These geologic map sheets and report encompass the proposed State Route 95 Relocation
Corridor in Mohave Valley, western Arizona, between the Black Mountains on the east and the
Colorado River on the west (Figure 1). The maps were developed through compilation of
existing geologic mapping and extensive new geologic mapping. The map area includes a
portion of the historical floodplain of the Colorado River, a broad swath of the piedmont east of
the river, parts of western flank of the Black Mountains, the channels and terraces of Sacramento
Wash, and the northernmost piedmont of the Mohave Mountains (the Powell Mountain area).
The corridor is predominantly covered with late Miocene and younger alluvium deposited by
local tributary washes and the Colorado River. Deposits range in age from modern to at least 8
Ma (millions of years ago), and deposit characteristics and composition vary substantially
depending on whether they were emplaced by the modern Colorado River, older versions of the
river, or tributary washes derived from the Black Mountains or the northern end of the Mohave
Mountains. The northern, northeastern, and southernmost parts of the map include a variety of
bedrock types ranging in age from early Proterozoic to middle Miocene. This map and report
describe the physical characteristics of geologic units of different ages and sources, the mapped
extent of various geologic units, and potential geologic resource and geologic hazard
implications of this mapping. These maps include modified versions of portions of several
published maps that have been completed in this area since 1997 (Howard et al., 1997; Howard
et al., 1999; Faulds et al., 2001; Murphy et al., 2004; Pearthree and House, 2005; Pearthree,
2007; Spencer et al., 2007; Malmon, in review). Extensive new surficial geologic mapping and
bedrock mapping was done where needed.