U.S. Geological Survey Scientific Investigations Map 3062
The Needles 7.5’ quadrangle straddles the Colorado River in the southern part of the Mohave Valley, in Mohave County, Arizona, and San Bernardino County, California. The quadrangle contains part of the Havasu National Wildlife Refuge, sections of the Fort Mojave Indian Reservation, most of the city of Needles, and several major interstate highways and railroads. The quadrangle is underlain by structurally undeformed sediments of Pliocene and younger age that were deposited by the Colorado River, as well as alluvial fan deposits on the piedmonts that flank the Black Mountains (in Arizona) and the Sacramento Mountains (in California).
Multiple cycles of aggradation of the Colorado River, each followed by episodes of downcutting, are recorded by Pliocene through historic deposits on the piedmonts that border the floodplain. Regionally, the complex stratigraphy related to the Colorado River has been the subject of geologic interest for over 150 years. The California and Arizona piedmont portions of the Needles quadrangle expose a subset of this incompletely understood stratigraphic record. Thus, the stratigraphic sequence presented on this map is a version of the stratigraphy of the Colorado River as interpreted locally.
The deposits in the recently active Colorado River valley floor support riparian habitat and irrigated agriculture. The distributions of sand-rich channel deposits and mud-rich floodplain deposits in the valley are mapped on the basis of the history of the movement of the Colorado River in the quadrangle, which has been documented in sequential aerial photographs since 1937 and maps dating to 1857.
Posted March 2, 2009
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Malmon, Daniel V., Howard, Keith A., and Priest, Susan S., 2009, Geologic map of the Needles 7.5' quadrangle, California and Arizona: U.S. Geological Survey Scientific Investigations Map 3062, scale 1;24,000, 1 sheet, includes 31 p. pamphlet [https://pubs.usgs.gov/sim/3062/].
Stratigraphic Nomenclature and Mapping Conventions
Geologic and Tectonic Setting
Geologic History and Interpretations
Exposure at the Southpoint Power Plant
Distribution of Sediment on the Valley Floor
Flood Hazards in the Needles Quadrangle
Description of Map Units