Surficial geologic map of the Eloy South Quadrangle, Pinal County, Arizona
Dates
Publication Date
1990-01-01
Start Date
2022-08-18
End Date
2022-08-18
Citation
Jackson, G. (2022). Surficial geologic map of the Eloy South Quadrangle, Pinal County, Arizona: .
Summary
Surficial geologic maps of the Eloy South Quadrangle of the Picacho Basin. The Picacho basin is a large and complex graben surrounded by horsts and half-horsts, which are now the Picacho, Casa Grande, Silverbell, and Sacaton mountains. It formed mainly in response to late Miocene extension. Internal drainage probably persisted until about 3 million years ago. Several thousand meters of sediments fill the basin; 2000 m of evaporites and claystone form the bulk of the basin fill (Scarborough and Pierce, 1978). The upper 200 meters or so of basin fill was deposited by a gradually aggrading, regionally integrated drainage system. Young alluvium of the Santa Cruz River is up to 30 m thick and is found within 3.2 km of the modern channel [...]
Summary
Surficial geologic maps of the Eloy South Quadrangle of the Picacho Basin. The Picacho basin is a large and complex graben surrounded by horsts and half-horsts, which are now the Picacho, Casa Grande, Silverbell, and Sacaton mountains. It formed mainly in response to late Miocene extension. Internal drainage probably persisted until about 3 million years ago. Several thousand meters of sediments fill the basin; 2000 m of evaporites and claystone form the bulk of the basin fill (Scarborough and Pierce, 1978). The upper 200 meters or so of basin fill was deposited by a gradually aggrading, regionally integrated drainage system. Young alluvium of the Santa Cruz River is up to 30 m thick and is found within 3.2 km of the modern channel (Pool, 1986). Although the Picacho Basin does have external drainage, extremely low stream gradients and a lack of long-term downcutting have resulted in playa-like sediments, eolian deposits, and a lack of significant elevation differences between "terraces. Unlike basins upstream, the Picacho basin has not been incised significantly during the Quaternary.
This is a new version of the OFR-90-02 map. Principal changes include the addition of GIS data in the USGS GeMS format and may also include corrections to metadata, map units, age information, and other geologic interpretations. This work was funded by the USGS National Geological and Geophysical Data Preservation Program under grant G21AP10428.
