Geologic Map of the Ninetysix Hills SE, Pinal County, Arizona v.2.0
Dates
Publication Date
2022-11-17
Start Date
2022-11-17
End Date
2022-11-17
Citation
Skotnicki, S.J. (2022). Geologic Map of the Ninetysix Hills SE, Pinal County, Arizona v. 2.0.
Summary
The Ninetysix Hills of Pinal County, Arizona, consist of a series of low hills and pediment situated about half way between the towns of Florence and Catalina, and are about 70 km ( 45 mi.) north of Tucson (see figure 1). The low spine of hills is underlain by at least four separate granitic plutons. The older pluton, a coarse-grained K-feldspar megacrystic granite exposed in the south, is intruded by a medium-grained granite to granodiorite. Both of these units are locally foliated, but have mineralogic and textural characteristics that suggest they do not belong to the regional suite of 1.65 to 1. 7 Ga-old granites, but are younger. The quartz-porphyritic Teacup granodiorite (Krieger, 1974a, 1974b, Bradfish, 1979) comprises most [...]
Summary
The Ninetysix Hills of Pinal County, Arizona, consist of a series of low hills and pediment situated about half way between the towns of Florence and Catalina, and are about 70 km ( 45 mi.) north of Tucson (see figure 1). The low spine of hills is underlain by at least four separate granitic plutons. The older pluton, a coarse-grained K-feldspar megacrystic granite exposed in the south, is intruded by a medium-grained granite to granodiorite. Both of these units are locally foliated, but have mineralogic and textural characteristics that suggest they do not belong to the regional suite of 1.65 to 1. 7 Ga-old granites, but are younger. The quartz-porphyritic Teacup granodiorite (Krieger, 1974a, 1974b, Bradfish, 1979) comprises most of the northern part of the Ninetysix Hills, and is mapped to the north in the Grayback Quadrangle (Cornwall and Krieger, 1975) and North Butte Quadrangle (Spencer and Richard, 1997). The Teacup granodiorite appears to be intruded by a younger, medium- to coarse-grained, slightly peraluminous granite that forms the central part of the range. A correlation diagram is shown in figure 2. This study encompasses the four USGS 7.5' quadrangles that encompass the Ninetysix Hills; they are (1) Ninetysix Hills NW, (2) Ninetysix Hills NE, (3) Ninetysix Hills SW, and ( 4) Ninetysix Hills SE. Most of the bedrock exposures were examined and mapped on the ground. The surficial deposits were largely mapped using approximately 1:24,000 scale black-and-white aerial photographs, dated 10/90, obtained from the US Geological Survey. Access to the area is very good. Highway 80 cuts diagonally across the southwestern part of the map area. Branching off this road, the 96 Hills Ranch Road provides access to the northwestern part of the range. The Freeman Road is well maintained and provides excellent access to the southern and southwestern areas. The Freeman Road also crosses the range where it meets up with the Barkerville Road, which parallels the east side of the Ninetysix Hills. To the north the Barkerville Road intersects the Florence-Kelvin Highway-a well-maintained dirt road that provides good access to the northern part of the region. Several of the.dirt roads that branch off these major roads are accessible even with a 2-wheel drive vehicle.
This is a new version of the OFR-99-20 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.
